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Sample records for model relating reaction

  1. Constitutive Relations for Reactive Transport Modeling: Effects of Chemical Reactions on Multi-Phase Flow Properties

    Science.gov (United States)

    Zhang, S.; Liu, H. H.; van Dijke, M. I.; Geiger, S.; Agar, S. M.

    2016-12-01

    The relationship between flow properties and chemical reactions is key to modeling subsurface reactive transport. This study develops closed-form equations to describe the effects of mineral precipitation and dissolution on multiphase flow properties (capillary pressure and relative permeabilities) of porous media. The model accounts for the fact that precipitation/dissolution only takes place in the water-filled part of pore space. The capillary tube concept was used to connect pore-scale changes to macroscopic hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and consequently in the pore-size distribution. The updated pore-size distribution is converted back to a new capillary pressure-water saturation relation from which the new relative permeabilities are calculated. Pore network modeling is conducted on a Berea sandstone to validate the new continuum-scale relations. The pore network modeling results are satisfactorily predicted by the new closed-form equations. Currently the effects of chemical reactions on flow properties are represented as a relation between permeability and porosity in reactive transport modeling. Porosity is updated after chemical calculations from the change of mineral volumes, then permeability change is calculated from the porosity change using an empirical permeability-porosity relation, most commonly the Carman-Kozeny relation, or the Verma-Pruess relation. To the best of our knowledge, there are no closed-form relations available yet for the effects of chemical reactions on multi-phase flow properties, and thus currently these effects cannot be accounted for in reactive transport modeling. This work presents new constitutive relations to represent how chemical reactions affect multi-phase flow properties on the continuum scale based on the conceptual model of parallel capillary tubes. The parameters in our new relations are either pre-existing input in a multi-phase flow

  2. On Back-reaction in Special Relativity

    CERN Document Server

    Nelson, William M

    2013-01-01

    Back-reaction of fields plays an important role in the generation of particle masses and the mass-energy equivalence of special relativity, but the most natural demonstrations using classical models result in apparent errors such as the notorious "4/3" problem. Here we discuss the resolution of these discrepancies within the underlying atomic description of matter, with the aim of encouraging classroom discussion of back-reaction and its connection to relativistic effects.

  3. EQ6, a computer program for reaction path modeling of aqueous geochemical systems: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 4

    Energy Technology Data Exchange (ETDEWEB)

    Wolery, T.J.; Daveler, S.A.

    1992-10-09

    EQ6 is a FORTRAN computer program in the EQ3/6 software package (Wolery, 1979). It calculates reaction paths (chemical evolution) in reacting water-rock and water-rock-waste systems. Speciation in aqueous solution is an integral part of these calculations. EQ6 computes models of titration processes (including fluid mixing), irreversible reaction in closed systems, irreversible reaction in some simple kinds of open systems, and heating or cooling processes, as well as solve ``single-point`` thermodynamic equilibrium problems. A reaction path calculation normally involves a sequence of thermodynamic equilibrium calculations. Chemical evolution is driven by a set of irreversible reactions (i.e., reactions out of equilibrium) and/or changes in temperature and/or pressure. These irreversible reactions usually represent the dissolution or precipitation of minerals or other solids. The code computes the appearance and disappearance of phases in solubility equilibrium with the water. It finds the identities of these phases automatically. The user may specify which potential phases are allowed to form and which are not. There is an option to fix the fugacities of specified gas species, simulating contact with a large external reservoir. Rate laws for irreversible reactions may be either relative rates or actual rates. If any actual rates are used, the calculation has a time frame. Several forms for actual rate laws are programmed into the code. EQ6 is presently able to model both mineral dissolution and growth kinetics.

  4. A Bigraph Relational Model

    DEFF Research Database (Denmark)

    Beauquier, Maxime; Schürmann, Carsten

    2011-01-01

    In this paper, we present a model based on relations for bigraphical reactive system [Milner09]. Its defining characteristics are that validity and reaction relations are captured as traces in a multi-set rewriting system. The relational model is derived from Milner's graphical definition...

  5. Reduction of chemical reaction models

    Science.gov (United States)

    Frenklach, Michael

    1991-01-01

    An attempt is made to reconcile the different terminologies pertaining to reduction of chemical reaction models. The approaches considered include global modeling, response modeling, detailed reduction, chemical lumping, and statistical lumping. The advantages and drawbacks of each of these methods are pointed out.

  6. Exact First-Passage Exponents of 1D Domain Growth: Relation to a Reaction-Diffusion Model

    Science.gov (United States)

    Derrida, Bernard; Hakim, Vincent; Pasquier, Vincent

    1995-07-01

    In the zero temperature Glauber dynamics of the ferromagnetic Ising or q-state Potts model, the size of domains is known to grow like t1/2. Recent simulations have shown that the fraction r\\(q,t\\) of spins, which have never flipped up to time t, decays like the power law r\\(q,t\\)~t-θ\\(q\\) with a nontrivial dependence of the exponent θ\\(q\\) on q and on space dimension. By mapping the problem on an exactly soluble one-species coagulation model ( A+A-->A), we obtain the exact expression of θ\\(q\\) in dimension one.

  7. Economic consequences of the adverse reactions related with antipsychotics: an economic model comparing tolerability of ziprasidone, olanzapine, risperidone, and haloperidol in Spain.

    Science.gov (United States)

    Bobes, Julio; Cañas, Fernando; Rejas, Javier; Mackell, Joan

    2004-12-01

    Frequency of adverse reactions (ARs) related with antipsychotics usage is high. Along with clinical implications, economic impact might be important. The purpose of this study was to model the economic consequences of ARs related with ziprasidone, olanzapine, risperidone, and haloperidol in Spain, by means of a cost-effectiveness model developed using a Markov modeling approach. The model simulated treatment of a cohort of 1000 schizophrenics for 12 months, initiating treatment with one of four antipsychotic drugs; haloperidol, risperidone, olanzapine and ziprasidone. Conditional probabilities of developing any of four adverse events were calculated. Treatment was modified (decrease dose, switch medication) according to incidence of ARs and physician judgments, obtained from a local cross-sectional study and clinical trials previously published. The analysis was conducted in year 2002 from a third party payer perspective. Results are shown as annual cost per month with psychotic symptoms controlled and included univariate sensitivity analysis. The therapeutic strategy starting with ziprasidone showed the lower costs and the greater number of months with symptoms controlled in most scenarios evaluated versus the other options considered, although the differences were weak: 9.6, 9.3, 9.5 and 9.5 controlled months per patient in base scenario, with annual cost per patient per month with symptoms controlled of 1035 Euros, 1084 Euros, 1087 Euros and 1090 Euros for ziprasidone, haloperidol, risperidone and olanzapine, respectively. Results were robust to one-way sensitivity analysis. Despite the unlike drug prices of antipsychotics, a considerable economic impact due to adverse reactions was seen in our setting. These results should be taken into account by health decision makers and clinicians in the management of patients with schizophrenia.

  8. Progress in microscopic direct reaction modeling of nucleon induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dupuis, M.; Bauge, E.; Hilaire, S.; Lechaftois, F.; Peru, S.; Pillet, N.; Robin, C. [CEA, DAM, DIF, Arpajon (France)

    2015-12-15

    A microscopic nuclear reaction model is applied to neutron elastic and direct inelastic scatterings, and pre-equilibrium reaction. The JLM folding model is used with nuclear structure information calculated within the quasi-particle random phase approximation implemented with the Gogny D1S interaction. The folding model for direct inelastic scattering is extended to include rearrangement corrections stemming from both isoscalar and isovector density variations occurring during a transition. The quality of the predicted (n,n), (n,n{sup '}), (n,xn) and (n,n{sup '}γ) cross sections, as well as the generality of the present microscopic approach, shows that it is a powerful tool that can help improving nuclear reactions data quality. Short- and long-term perspectives are drawn to extend the present approach to more systems, to include missing reactions mechanisms, and to consistently treat both structure and reaction problems. (orig.)

  9. Investigation and Modelling of Diesel Hydrotreating Reactions

    DEFF Research Database (Denmark)

    Boesen, Rasmus Risum

    This project consists of a series of studies, that are related to hydrotreating of diesel. Hy- drotreating is an important refinery process, in which the oil stream is upgraded to meet the required environmental specifications and physical properties. Although hydrotreating is a ma- ture technology...... on a commercial CoMo catalyst, and a simple kinetic model is presented. Hydrogenation of fused aromatic rings are known to be fast, and it is possible, that the reaction rates are limited by either internal or external mass transfer. An experiment conducted at industrial temperatures and pressure, using...... kinetic models. Hydrogenation reactions are quite fast, and in order to avoid mass transfer limitations, and only measure intrinsic rates, experiments are often conducted, at conditions that are milder than in industrial units. A reactor model for a Robinson-Mahoney reactor that takes mass transfer...

  10. Modelling Chemical Reasoning to Predict Reactions

    CERN Document Server

    Segler, Marwin H S

    2016-01-01

    The ability to reason beyond established knowledge allows Organic Chemists to solve synthetic problems and to invent novel transformations. Here, we propose a model which mimics chemical reasoning and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outperforms a rule-based expert system in the reaction prediction task for 180,000 randomly selected binary reactions. We show that our data-driven model generalises even beyond known reaction types, and is thus capable of effectively (re-) discovering novel transformations (even including transition-metal catalysed reactions). Our model enables computers to infer hypotheses about reactivity and reactions by only considering the intrinsic local structure of the graph, and because each single reaction prediction is typically ac...

  11. Temporal Lobe Reactions After Carbon Ion Radiation Therapy: Comparison of Relative Biological Effectiveness–Weighted Tolerance Doses Predicted by Local Effect Models I and IV

    Energy Technology Data Exchange (ETDEWEB)

    Gillmann, Clarissa, E-mail: clarissa.gillmann@med.uni-heidelberg.de [Department of Radiation Oncology and Radiation Therapy, Heidelberg University Hospital, Heidelberg (Germany); Jäkel, Oliver [Department of Radiation Oncology and Radiation Therapy, Heidelberg University Hospital, Heidelberg (Germany); Heidelberg Ion Beam Therapy Center (HIT), Heidelberg (Germany); Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg (Germany); Schlampp, Ingmar [Department of Radiation Oncology and Radiation Therapy, Heidelberg University Hospital, Heidelberg (Germany); Karger, Christian P. [Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg (Germany)

    2014-04-01

    Purpose: To compare the relative biological effectiveness (RBE)–weighted tolerance doses for temporal lobe reactions after carbon ion radiation therapy using 2 different versions of the local effect model (LEM I vs LEM IV) for the same patient collective under identical conditions. Methods and Materials: In a previous study, 59 patients were investigated, of whom 10 experienced temporal lobe reactions (TLR) after carbon ion radiation therapy for low-grade skull-base chordoma and chondrosarcoma at Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany in 2002 and 2003. TLR were detected as visible contrast enhancements on T1-weighted MRI images within a median follow-up time of 2.5 years. Although the derived RBE-weighted temporal lobe doses were based on the clinically applied LEM I, we have now recalculated the RBE-weighted dose distributions using LEM IV and derived dose-response curves with Dmax,V-1 cm³ (the RBE-weighted maximum dose in the remaining temporal lobe volume, excluding the volume of 1 cm³ with the highest dose) as an independent dosimetric variable. The resulting RBE-weighted tolerance doses were compared with those of the previous study to assess the clinical impact of LEM IV relative to LEM I. Results: The dose-response curve of LEM IV is shifted toward higher values compared to that of LEM I. The RBE-weighted tolerance dose for a 5% complication probability (TD{sub 5}) increases from 68.8 ± 3.3 to 78.3 ± 4.3 Gy (RBE) for LEM IV as compared to LEM I. Conclusions: LEM IV predicts a clinically significant increase of the RBE-weighted tolerance doses for the temporal lobe as compared to the currently applied LEM I. The limited available photon data do not allow a final conclusion as to whether RBE predictions of LEM I or LEM IV better fit better clinical experience in photon therapy. The decision about a future clinical application of LEM IV therefore requires additional analysis of temporal lobe reactions in a

  12. Metathesis of alkanes and related reactions

    KAUST Repository

    Basset, Jean-Marie

    2010-02-16

    (Figure Presented) The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, (=SiO)2TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of aluminasupported tungsten hydride, W(H)3/Al 2O3, which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of

  13. Metathesis of alkanes and related reactions.

    Science.gov (United States)

    Basset, Jean-Marie; Copéret, Christophe; Soulivong, Daravong; Taoufik, Mostafa; Cazat, Jean Thivolle

    2010-02-16

    The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, ([triple bond]SiO)(2)TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of alumina-supported tungsten hydride, W(H)(3)/Al(2)O(3), which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis

  14. Modelling Chemical Reasoning to Predict Reactions

    OpenAIRE

    Segler, Marwin H. S.; Waller, Mark P.

    2016-01-01

    The ability to reason beyond established knowledge allows Organic Chemists to solve synthetic problems and to invent novel transformations. Here, we propose a model which mimics chemical reasoning and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outpe...

  15. Modeling the isotope effect in Walden inversion reactions

    Science.gov (United States)

    Schechter, Israel

    1991-05-01

    A simple model to explain the isotope effect in the Walden exchange reaction is suggested. It is developed in the spirit of the line-of-centers models, and considers a hard-sphere collision that transfers energy from the relative translation to the desired vibrational mode, as well as geometrical properties and steric requirements. This model reproduces the recently measured cross sections for the reactions of hydrogen with isotopic silanes and older measurements of the substitution reactions of tritium atoms with isotopic methanes. Unlike previously given explanations, this model explains the effect of the attacking atom as well as of the other participating atoms. The model provides also qualitative explanation of the measured relative yields and thresholds of CH 3T and CH 2TF from the reaction T + CH 3F. Predictions for isotope effects and cross sections of some unmeasured reactions are given.

  16. REACTION CHEMISTRY RELATED TO FCC GASOLINE QUALITY

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    About 80% of the gasoline pool as a whole in China for supplying the domestic market at current stage directly originates from FCC units. Obviously, FCC gasoline quality is critical for refiners to meet the nations more and more stringent gasoline specifications. FCC process is expected to produce gasoline with reduced contents of olefins, aromatics, benzene, sulfur, and, contradictorily, still with high octane number.   Catalytic cracking process involves a series of acid catalyzed reactions. Bronsted acid sites dominate the surface of the catalyst used for FCC process. All the reactions of hydrocarbons in FCC process are based on carbonium ions of penta-coordinated, or carbenium ions of tri-coordinated. The monomolecular beta scission mechanism for alkane cracking explains that the cracking of carbon-carbon bonding occurs at the beta position to the carbon atom bearing positive charge, and hence forms two small hydrocarbon molecules: one alkane molecule and one olefin molecule. The molar ratio of alkane to olefin for the primary cracking product will be 1 and it will be less than 1 if the cracking reaction proceeds.   However, it is proved that bimolecular reaction pathways exist between surface carbenium ions and the feed molecules. The products of this bimolecular disproportionation reaction could be an alkane molecule and a newly formed carbenium ion. The better understanding of the reaction chemistry of FCC process based on monomolecular pathways and bimolecular pathways should be the basis for searching approaches to the improvement of FCC gasoline quality. In the complicated reaction scheme of the FCC process, the isomerization reaction leading to the formation of iso-alkanes is obviously a target reaction, which favors both olefin reduction and octane enhancement.   The cracking of small paraffin molecules, due to its limited number of reaction pathways and products, has been used to investigate cracking mechanism. In the present work the

  17. Reaction time in relation to duration of heroin abuse

    Directory of Open Access Journals (Sweden)

    Martinović-Mitrović Slađana

    2011-01-01

    Full Text Available Introduction. Consequences of heroin abuse include organic damage of cerebral structures. The level of impairments is in a direct and positive relation with the length of heroin abuse. Objective. The aim of this research was the evaluation of the reaction time with heroin addicts with different length of substance abuse. Methods. Research method: 90 examinees were divided into three groups with relation to the length of heroin abuse. Data collection included a questionnaire referring to socio-demographic and addictive characteristics. A specially designed programme was used for the evaluation of reaction time to audio/ visual signal. Results. In relation to the reaction time as overall model, the difference between examinees with different length of heroin abuse can be found on the marginal level of significance (F=1.69; df=12; p=0.07. In visual modality, with the increase of length of heroin abuse leads to a significant prolongation of simple (the first visual sign: F=3.29; df=2; p=0.04 and choice reaction time (the second visual sign: F=4.97; df=2; p=0.00; the third visual sign: F=3.08; df=2; p=0.05. Longer heroin consumption also leads to the prolongation of the simple (the first auditory task: F=3.41; df=2; p=0.04 and the complex auditory reaction time (the second auditory task: F=5.67; df=2; p=0.01; the third auditory task: F=6.42; df=2; p=0.00. Conclusion. Heroin abuse leads to the prolongation of both simple and choice reaction time in visual as well as auditory modality. The average daily dose of opiates was the most important predictor of the abovementioned cognitive dysfunction.

  18. Connectionist and diffusion models of reaction time.

    Science.gov (United States)

    Ratcliff, R; Van Zandt, T; McKoon, G

    1999-04-01

    Two connectionist frameworks, GRAIN (J. L. McClelland, 1993) and brain-state-in-a-box (J. A. Anderson, 1991), and R. Ratcliff's (1978) diffusion model were evaluated using data from a signal detection task. Dependent variables included response probabilities, reaction times for correct and error responses, and shapes of reaction-time distributions. The diffusion model accounted for all aspects of the data, including error reaction times that had previously been a problem for all response-time models. The connectionist models accounted for many aspects of the data adequately, but each failed to a greater or lesser degree in important ways except for one model that was similar to the diffusion model. The findings advance the development of the diffusion model and show that the long tradition of reaction-time research and theory is a fertile domain for development and testing of connectionist assumptions about how decisions are generated over time.

  19. Chemical-reaction model for Mexican wave

    Science.gov (United States)

    Nagatani, Takashi

    2003-05-01

    We present a chemical-reaction model to describe the Mexican wave ( La Ola) in football stadia. The spectator's action is described in terms of chemical reactions. The model is governed by three reaction rates k 1, k 2, and k3. We study the nonlinear waves on one- and two-dimensional lattices. The Mexican wave is formulated as a clockwise forwardly propagating wave. Waves are growing or disappear, depending on the values of reaction rates. In the specific case of k1= k2= k3=1, the nonlinear-wave equation produces a propagating pulse like soliton.

  20. A Networks Approach to Modeling Enzymatic Reactions.

    Science.gov (United States)

    Imhof, P

    2016-01-01

    Modeling enzymatic reactions is a demanding task due to the complexity of the system, the many degrees of freedom involved and the complex, chemical, and conformational transitions associated with the reaction. Consequently, enzymatic reactions are not determined by precisely one reaction pathway. Hence, it is beneficial to obtain a comprehensive picture of possible reaction paths and competing mechanisms. By combining individually generated intermediate states and chemical transition steps a network of such pathways can be constructed. Transition networks are a discretized representation of a potential energy landscape consisting of a multitude of reaction pathways connecting the end states of the reaction. The graph structure of the network allows an easy identification of the energetically most favorable pathways as well as a number of alternative routes.

  1. Kinetics of Model Reactions for Interfacial Polymerization

    Directory of Open Access Journals (Sweden)

    Henry Hall

    2012-02-01

    Full Text Available To model the rates of interfacial polycondensations, the rates of reaction of benzoyl chloride and methyl chloroformate with various aliphatic monoamines in acetonitrile were determined at 25 °C. Buffering with picric acid slowed these extremely fast reactions so the rate constants could be determined from the rate of disappearance of picrate ion. The rates of the amine reactions correlated linearly with their Swain-Scott nucleophilicities.

  2. A Full Disturbance Model for Reaction Wheels

    NARCIS (Netherlands)

    Le, M.P.; Ellenbroek, Marcellinus Hermannus Maria; Seiler, R; van Put, P.; Cottaar, E.J.E.

    2014-01-01

    Reaction wheels are rotating devices used for the attitude control of spacecraft. However, reaction wheels also generate undesired disturbances in the form of vibrations, which may have an adverse effect on the pointing accuracy and stability of spacecraft (optical) payloads. A disturbance model for

  3. Modeling of turbulent chemical reaction

    Science.gov (United States)

    Chen, J.-Y.

    1995-01-01

    Viewgraphs are presented on modeling turbulent reacting flows, regimes of turbulent combustion, regimes of premixed and regimes of non-premixed turbulent combustion, chemical closure models, flamelet model, conditional moment closure (CMC), NO(x) emissions from turbulent H2 jet flames, probability density function (PDF), departures from chemical equilibrium, mixing models for PDF methods, comparison of predicted and measured H2O mass fractions in turbulent nonpremixed jet flames, experimental evidence of preferential diffusion in turbulent jet flames, and computation of turbulent reacting flows.

  4. Reactions to the New Standards for School Public Relations Specialists.

    Science.gov (United States)

    Kowalski, Theodore J.

    2002-01-01

    Reactions by 10 individuals associated with the "Journal of School Public Relations" to new National School Public Relations Association standards for school public relations and communications professionals and programs. Includes general reactions, impact of the standards, possible ambiguity, adding or eliminating standards, and…

  5. Reactions to the New Standards for School Public Relations Specialists.

    Science.gov (United States)

    Kowalski, Theodore J.

    2002-01-01

    Reactions by 10 individuals associated with the "Journal of School Public Relations" to new National School Public Relations Association standards for school public relations and communications professionals and programs. Includes general reactions, impact of the standards, possible ambiguity, adding or eliminating standards, and influence on…

  6. Hypersensitivity reactions and contrast medium injection: Are they always related?

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, Ingrid, E-mail: i.boehm@uni-bonn.de [Department of Radiology, Philipps University of Marburg, Baldingerstrasse, 35039 Marburg (Germany); Alfke, Heiko [Department of Radiology, Klinikum Luedenscheid, Luedenscheid (Germany); Klose, Klaus Jochen [Department of Radiology, Philipps University of Marburg, Baldingerstrasse, 35039 Marburg (Germany)

    2011-11-15

    Background: Hypersensitivity (allergic or non-allergic) reactions that occur after contrast medium (CM) injection are usually related to the CM. Recent studies, and case reports lack the analysis of alternate causes that could be also responsible in individual cases. Patients and methods: We investigated the individual relevant factor/causative agent of adult patients with hypersensitivity reactions that occurred in radiological units during CM-enhanced procedures (CT, angiography, urography, or MR-examinations). Both immediate and non-immediate (delayed) reactions were included. To find out the relevant agent a detailed patients' history was carefully analyzed. In addition, the records were retrospectively reviewed, and if indicated and possible laboratory (e.g. basophil activation test) and skin tests (e.g. prick) and/or provocations with CM-injections under routine conditions were performed. Results: 38 patients (men n = 21) suspected for CM-hypersensitivity reactions were identified. These reactions were in most cases mild (n = 21), moderate reactions occurred in 13 cases, and four patients had severe reactions. In 28 patients the reactions were induced by the CM (iodinated CM in 25 cases). Four patients had reactions that were not CM-related (latex allergy, adenosine reaction, vasovagal reaction, unknown cause) and in six cases the reaction was partly CM-related (immunological activation was present due to the patients' diseases). Conclusion: Our data support the hypothesis that in CM-enhanced procedures not only contrast materials but also a broad range of other factors may also induce hypersensitivity reactions. Therefore, the number of CM-induced hypersensitivity is smaller than initially suspected. The knowledge of the cause of a reaction is essential to effectively prevent its recurrence and to improve safety aspects in patients undergoing CM-injection. Larger trials should be performed to more specifically assess alternate causes in patients

  7. A Reaction-Based River/Stream Water Quality Model: Reaction Network Decomposition and Model Application

    OpenAIRE

    2012-01-01

    This paper describes details of an automatic matrix decomposition approach for a reaction-based stream water quality model. The method yields a set of equilibrium equations, a set of kinetic-variable transport equations involving kinetic reactions only, and a set of component transport equations involving no reactions. Partial decomposition of the system of water quality constituent transport equations is performed via Gauss-Jordan column reduction of the reaction network by pivoting on equil...

  8. Curing Reaction Model of Epoxy Asphalt Binder

    Institute of Scientific and Technical Information of China (English)

    QIAN Zhendong; CHEN Leilei; WANG Yaqi; SHEN Jialin

    2012-01-01

    In order to understand the strength developing law of the epoxy asphalt mixture,a curing reaction model of the epoxy asphalt binder was proposed based upon the thermokinetic analysis.Given some assumptions,the model was developed by applying the Kissinger law as well as Arrhenius equation,and the differential scanning calorimetry was performed for estimating the model parameters.To monitor the strength development of the epoxy asphalt mixture,a strength test program was employed and then results were compared to those produced from the proposed model.The comparative evaluation shows that a good consistency exists between the outputs from test program and the proposed model,indicating that the proposed model can be used effectively for simulating the curing reaction process for the epoxy asphalt binder and predicting the strength development for the epoxy asphalt mixture.

  9. Nonlinear control of the Salnikov model reaction

    DEFF Research Database (Denmark)

    Recke, Bodil; Jørgensen, Sten Bay

    1999-01-01

    This paper explores different nonlinear control schemes, applied to a simple model reaction. The model is the Salnikov model, consisting of two ordinary differential equations. The control strategies investigated are I/O-linearisation, Exact linearisation, exact linearisation combined with LQR...... and Control Lyapunov Functions (CLF's). The results show that based on the lowest possible cost function and shortest settling time, the exact linearisation performs marginally better than the other methods....

  10. Dynamical Model of Weak Pion Production Reactions

    CERN Document Server

    Sato, T; Lee, T S H

    2003-01-01

    The dynamical model of pion electroproduction has been extended to investigate the weak pion production reactions. The predicted cross sections of neutrino-induced pion production reactions are in good agreement with the existing data. We show that the renormalized(dressed) axial N-$\\Delta$ form factor contains large dynamical pion cloud effects and this renormalization effects are crucial in getting agreement with the data. We conclude that the N-$\\Delta$ transitions predicted by the constituent quark model are consistent with the existing neutrino induced pion production data in the $\\Delta$ region.

  11. QGSM development for spallation reactions modeling

    Directory of Open Access Journals (Sweden)

    Gudima K.K.

    2012-12-01

    Full Text Available The growing interest in spallation neutron sources, accelerator-driven systems, R&D of rare isotope beams, and development of external beam radiation therapy necessitated the improvement of nuclear reaction models for both stand-alone codes for the analysis of nuclear reactions and event generators within the Monte Carlo transport systems for calculations of interactions of high-energy particles with matter in a wide range of energy and in arbitrary 3D geometry of multicomponent targets. The exclusive approach to the description of nuclear reactions is the most effective for detailed calculation of inelastic interactions with atomic nuclei. It provides the correct description of particle production, single- and double-differential spectra, recoil, and fission product yields. This approach has been realized in the Quark Gluon String Model (QGSM for nuclear reactions induced by photons, hadrons, and high energy heavy ions. In this article, improved versions of the QGSM model and a corresponding code have been developed tested and bench marked against experimental data for neutron production in spallation reactions on thin and thick targets in the energy range from a few MeV to several GeV/nucleon.

  12. QGSM development for spallation reactions modeling

    Science.gov (United States)

    Baznat, M. I.; Chigrinov, S. E.; Gudima, K. K.

    2012-12-01

    The growing interest in spallation neutron sources, accelerator-driven systems, R&D of rare isotope beams, and development of external beam radiation therapy necessitated the improvement of nuclear reaction models for both stand-alone codes for the analysis of nuclear reactions and event generators within the Monte Carlo transport systems for calculations of interactions of high-energy particles with matter in a wide range of energy and in arbitrary 3D geometry of multicomponent targets. The exclusive approach to the description of nuclear reactions is the most effective for detailed calculation of inelastic interactions with atomic nuclei. It provides the correct description of particle production, single- and double-differential spectra, recoil, and fission product yields. This approach has been realized in the Quark Gluon String Model (QGSM) for nuclear reactions induced by photons, hadrons, and high energy heavy ions. In this article, improved versions of the QGSM model and a corresponding code have been developed tested and bench marked against experimental data for neutron production in spallation reactions on thin and thick targets in the energy range from a few MeV to several GeV/nucleon.

  13. Breakup reaction models for two- and three-cluster projectiles

    CERN Document Server

    Baye, D

    2010-01-01

    Breakup reactions are one of the main tools for the study of exotic nuclei, and in particular of their continuum. In order to get valuable information from measurements, a precise reaction model coupled to a fair description of the projectile is needed. We assume that the projectile initially possesses a cluster structure, which is revealed by the dissociation process. This structure is described by a few-body Hamiltonian involving effective forces between the clusters. Within this assumption, we review various reaction models. In semiclassical models, the projectile-target relative motion is described by a classical trajectory and the reaction properties are deduced by solving a time-dependent Schroedinger equation. We then describe the principle and variants of the eikonal approximation: the dynamical eikonal approximation, the standard eikonal approximation, and a corrected version avoiding Coulomb divergence. Finally, we present the continuum-discretized coupled-channel method (CDCC), in which the Schroed...

  14. Kinetic modeling of reactions in Foods

    NARCIS (Netherlands)

    Boekel, van M.A.J.S.

    2008-01-01

    The level of quality that food maintains as it travels down the production-to-consumption path is largely determined by the chemical, biochemical, physical, and microbiological changes that take place during its processing and storage. Kinetic Modeling of Reactions in Foods demonstrates how to effec

  15. DSMC modeling of flows with recombination reactions

    Science.gov (United States)

    Gimelshein, Sergey; Wysong, Ingrid

    2017-06-01

    An empirical microscopic recombination model is developed for the direct simulation Monte Carlo method that complements the extended weak vibrational bias model of dissociation. The model maintains the correct equilibrium reaction constant in a wide range of temperatures by using the collision theory to enforce the number of recombination events. It also strictly follows the detailed balance requirement for equilibrium gas. The model and its implementation are verified with oxygen and nitrogen heat bath relaxation and compared with available experimental data on atomic oxygen recombination in argon and molecular nitrogen.

  16. Reaction-diffusion pulses: a combustion model

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Daniel [Grup de FIsica EstadIstica, Dept. de FIsica, Universitat Autonoma de Barcelona, E-08193 Bellaterrra (Spain); Llebot, Josep Enric [Grup de FIsica EstadIstica, Dept. de FIsica, Universitat Autonoma de Barcelona, E-08193 Bellaterrra (Spain); Fort, Joaquim [Dept. de FIsica, Univ. de Girona, Campus de Montilivi, 17071 Girona, Catalonia (Spain)

    2004-07-02

    We focus on a reaction-diffusion approach proposed recently for experiments on combustion processes, where the heat released by combustion follows first-order reaction kinetics. This case allows us to perform an exhaustive analytical study. Specifically, we obtain the exact expressions for the speed of the thermal pulses, their maximum temperature and the condition of self-sustenance. Finally, we propose two generalizations of the model, namely, the case of several reactants burning together, and that of time-delayed heat conduction. We find an excellent agreement between our analytical results and simulations.

  17. Reaction Wheel Disturbance Model Extraction Software - RWDMES

    Science.gov (United States)

    Blaurock, Carl

    2009-01-01

    The RWDMES is a tool for modeling the disturbances imparted on spacecraft by spinning reaction wheels. Reaction wheels are usually the largest disturbance source on a precision pointing spacecraft, and can be the dominating source of pointing error. Accurate knowledge of the disturbance environment is critical to accurate prediction of the pointing performance. In the past, it has been difficult to extract an accurate wheel disturbance model since the forcing mechanisms are difficult to model physically, and the forcing amplitudes are filtered by the dynamics of the reaction wheel. RWDMES captures the wheel-induced disturbances using a hybrid physical/empirical model that is extracted directly from measured forcing data. The empirical models capture the tonal forces that occur at harmonics of the spin rate, and the broadband forces that arise from random effects. The empirical forcing functions are filtered by a physical model of the wheel structure that includes spin-rate-dependent moments (gyroscopic terms). The resulting hybrid model creates a highly accurate prediction of wheel-induced forces. It accounts for variation in disturbance frequency, as well as the shifts in structural amplification by the whirl modes, as the spin rate changes. This software provides a point-and-click environment for producing accurate models with minimal user effort. Where conventional approaches may take weeks to produce a model of variable quality, RWDMES can create a demonstrably high accuracy model in two hours. The software consists of a graphical user interface (GUI) that enables the user to specify all analysis parameters, to evaluate analysis results and to iteratively refine the model. Underlying algorithms automatically extract disturbance harmonics, initialize and tune harmonic models, and initialize and tune broadband noise models. The component steps are described in the RWDMES user s guide and include: converting time domain data to waterfall PSDs (power spectral

  18. A Reaction-Based River/Stream Water Quality Model: Reaction Network Decomposition and Model Application

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2012-01-01

    Full Text Available This paper describes details of an automatic matrix decomposition approach for a reaction-based stream water quality model. The method yields a set of equilibrium equations, a set of kinetic-variable transport equations involving kinetic reactions only, and a set of component transport equations involving no reactions. Partial decomposition of the system of water quality constituent transport equations is performed via Gauss-Jordan column reduction of the reaction network by pivoting on equilibrium reactions to decouple equilibrium and kinetic reactions. This approach minimizes the number of partial differential advective-dispersive transport equations and enables robust numerical integration. Complete matrix decomposition by further pivoting on linearly independent kinetic reactions allows some rate equations to be formulated individually and explicitly enforces conservation of component species when component transport equations are solved. The methodology is demonstrated for a case study involving eutrophication reactions in the Des Moines River in Iowa, USA and for two hypothetical examples to illustrate the ability of the model to simulate sediment and chemical transport with both mobile and immobile water phases and with complex reaction networks involving both kinetic and equilibrium reactions.

  19. To address surface reaction network complexity using scaling relations machine learning and DFT calculations

    Science.gov (United States)

    Ulissi, Zachary W.; Medford, Andrew J.; Bligaard, Thomas; Nørskov, Jens K.

    2017-01-01

    Surface reaction networks involving hydrocarbons exhibit enormous complexity with thousands of species and reactions for all but the very simplest of chemistries. We present a framework for optimization under uncertainty for heterogeneous catalysis reaction networks using surrogate models that are trained on the fly. The surrogate model is constructed by teaching a Gaussian process adsorption energies based on group additivity fingerprints, combined with transition-state scaling relations and a simple classifier for determining the rate-limiting step. The surrogate model is iteratively used to predict the most important reaction step to be calculated explicitly with computationally demanding electronic structure theory. Applying these methods to the reaction of syngas on rhodium(111), we identify the most likely reaction mechanism. Propagating uncertainty throughout this process yields the likelihood that the final mechanism is complete given measurements on only a subset of the entire network and uncertainty in the underlying density functional theory calculations. PMID:28262694

  20. To address surface reaction network complexity using scaling relations machine learning and DFT calculations

    Science.gov (United States)

    Ulissi, Zachary W.; Medford, Andrew J.; Bligaard, Thomas; Nørskov, Jens K.

    2017-03-01

    Surface reaction networks involving hydrocarbons exhibit enormous complexity with thousands of species and reactions for all but the very simplest of chemistries. We present a framework for optimization under uncertainty for heterogeneous catalysis reaction networks using surrogate models that are trained on the fly. The surrogate model is constructed by teaching a Gaussian process adsorption energies based on group additivity fingerprints, combined with transition-state scaling relations and a simple classifier for determining the rate-limiting step. The surrogate model is iteratively used to predict the most important reaction step to be calculated explicitly with computationally demanding electronic structure theory. Applying these methods to the reaction of syngas on rhodium(111), we identify the most likely reaction mechanism. Propagating uncertainty throughout this process yields the likelihood that the final mechanism is complete given measurements on only a subset of the entire network and uncertainty in the underlying density functional theory calculations.

  1. Considerations on immunization anxiety-related reactions in clusters

    Directory of Open Access Journals (Sweden)

    Ricardo Palacios

    2014-11-01

    Full Text Available A cluster of adverse events following immunization (AEFI represents a stress test for an immunization program. The community can suspect on vaccine-related reaction leading to mistrust on the immunization program. An immunization anxiety-related reaction is one of the hypotheses to be tested and can be reasonably accepted when the vaccine-related and immunization error-related reactions are ruled out and no coincidental events can explain the cases. Immunization program approaches widely accepted to understand and respond to adverse events are root-cause analysis and systems analysis. Psychiatric cognitive frame will support the root-cause analysis assigning a causal relationship to individual temporary disorders of the affected vaccinees. Communication will focus on vaccine safety and absence of errors in the immunization program. Systems analysis addresses the whole context considering the fear spread as a systemic threat. Socio-psychological frame offers a broader opportunity to understand and respond to a specific community. Management is based on communication to change community belief in misperceptions of vaccine risks and support the idea of immunization as a causal factor, different from the vaccine. Communities can consider use of psychiatric labels, Mass Psychogenic Illness or Mass Hysteria, as an act of inconsiderateness. Labels like immunization anxiety-related reactions in clusters or collective immunization anxiety-related reactions are recommended to bridge the causal perception of the community with the result of the scientific investigation of the cases.

  2. SOME PHOTOCHEMICAL AND PHOTOPHYSICAL REACTIONS OP CHLOROPHYLL ANDITS RELATIVES

    Energy Technology Data Exchange (ETDEWEB)

    Calvin, Melvin

    1960-04-11

    The solution photochemistry of chlorophyll and chlorophyll analogs is described. Many cases of electron transfer to or from the porphyrin macrocycle have been found, but in no case has any very large degree of energy storage been achieved. Because of the very rapid back-reaction for products with a {Delta}F of approximately -30 kcal, some solid state models in which such an energy storage might be achieved are described and their possible relation to the natural photosynthetic apparatus is given. We can see that while the solid state model (phthalocyanine) allows an approach from a somewhat different point of view, the net result is the same as what was sought, but so far not found, when we looked at the solution chemistry of chlorophyll (and chlorophyll model substances), namely, the transfer of an electron, or hydrogen atom, from the excited porphyrin to an electron acceptor at a high reduction level which can be used to reduce the ultimate carbon dioxide reducers, followed by the donation of an electron ultimately from water to the remaining radical ion, or lattice, which produces the net results of the transfer of the hydrogen from water to carbon dioxide.

  3. Reaction-contingency based bipartite Boolean modelling

    Science.gov (United States)

    2013-01-01

    Background Intracellular signalling systems are highly complex, rendering mathematical modelling of large signalling networks infeasible or impractical. Boolean modelling provides one feasible approach to whole-network modelling, but at the cost of dequantification and decontextualisation of activation. That is, these models cannot distinguish between different downstream roles played by the same component activated in different contexts. Results Here, we address this with a bipartite Boolean modelling approach. Briefly, we use a state oriented approach with separate update rules based on reactions and contingencies. This approach retains contextual activation information and distinguishes distinct signals passing through a single component. Furthermore, we integrate this approach in the rxncon framework to support automatic model generation and iterative model definition and validation. We benchmark this method with the previously mapped MAP kinase network in yeast, showing that minor adjustments suffice to produce a functional network description. Conclusions Taken together, we (i) present a bipartite Boolean modelling approach that retains contextual activation information, (ii) provide software support for automatic model generation, visualisation and simulation, and (iii) demonstrate its use for iterative model generation and validation. PMID:23835289

  4. Novel electrochemical reactions related to electrodeposition and electrochemical synthesis

    Directory of Open Access Journals (Sweden)

    Ito Y.

    2003-01-01

    Full Text Available Novel electrochemical reactions in molten salts related to electrodeposition and electrochemical synthesis are reviewed to show their usefulness and possibilities in producing functional materials. Surface nitriding of various metals and stainless steels is possible by the use of anodic reaction of nitride ion (N3- in LiCl-KCl-Li3N melts. Electrochemical hydrogen absorption/desorption reaction occurs in molten salts containing hydride ion (H-. Electrochemical implantation and displantation can be applied to form transition metal-rare earth metal alloys in LiCl-KCl melts containing rare earth chlorides. As non-conventional electrochemical reactions, direct electrochemical reduction of SiO2 to Si, discharge electrolysis to form metal oxide particles and electrochemical plantation of Zr on ceramics are described.

  5. A theoretical model of metal surface reactions

    Energy Technology Data Exchange (ETDEWEB)

    Shustorovich, E. (Eastman Kodak Co., Rochester, NY); Baetzold, R.C.; Muetterties, E.L.

    1983-03-31

    Metal surface reactions are modeled with a novel theoretical construct in which periodic trends can be scrutinized. The theoretical model is succinctly presented and a conspectus of periodic trends, based on the model, is explored. Periodic trends are discussed in the contexts of chemisorption bond energies, electron transfer between metal surface and adsorbate, stereochemical features of chemisorption states for closed-shell diatomic and linear X-CN or X-NC molecules, and hydrocarbon reactions. Hydrocarbon C-H bond-breaking processes are analyzed in terms of d-level occupancy, electron transfer, and stereochemistry of intermediates. Conceptually and computationally, the metal surface is characterized as a good electron donor: antibonding molecular orbitals of the adsorbate species appear to be significant contributors to the chemisorption bond and also play a decisive role in bond-breaking processes. No aspect of the model projections is inconsistent with the experimental data although the electronic characterization of some chemisorption states are counter to commonly held perceptions.

  6. The difference between the perception of absolute and relative motion: A reaction time study

    NARCIS (Netherlands)

    J.B. Smeets (Jeroen); E. Brenner (Eli)

    1994-01-01

    textabstractWe used a reaction-time paradigm to examine the extent to which motion detection depends on relative motion. In the absence of relative motion, the responses could be described by a simple model based on the detection of a fixed change in position. If relative motion was present, the res

  7. Implementation of a vibrationally linked chemical reaction model for DSMC

    Science.gov (United States)

    Carlson, A. B.; Bird, Graeme A.

    1994-01-01

    A new procedure closely linking dissociation and exchange reactions in air to the vibrational levels of the diatomic molecules has been implemented in both one- and two-dimensional versions of Direct Simulation Monte Carlo (DSMC) programs. The previous modeling of chemical reactions with DSMC was based on the continuum reaction rates for the various possible reactions. The new method is more closely related to the actual physics of dissociation and is more appropriate to the particle nature of DSMC. Two cases are presented: the relaxation to equilibrium of undissociated air initially at 10,000 K, and the axisymmetric calculation of shuttle forebody heating during reentry at 92.35 km and 7500 m/s. Although reaction rates are not used in determining the dissociations or exchange reactions, the new method produces rates which agree astonishingly well with the published rates derived from experiment. The results for gas properties and surface properties also agree well with the results produced by earlier DSMC models, equilibrium air calculations, and experiment.

  8. Reaction-diffusion models of decontamination

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    A contaminant, which also contains a polymer is in the form of droplets on a solid surface. It is to be removed by the action of a decontaminant, which is applied in aqueous solution. The contaminant is only sparingly soluble in water, so the reaction mechanism is that it slowly dissolves...... in the aqueous solution and then is oxidized by the decontaminant. The polymer is insoluble in water, and so builds up near the interface, where its presence can impede the transport of contaminant. In these circumstances, Dstl wish to have mathematical models that give an understanding of the process, and can...

  9. Modelling dense relational data

    DEFF Research Database (Denmark)

    Herlau, Tue; Mørup, Morten; Schmidt, Mikkel Nørgaard;

    2012-01-01

    Relational modelling classically consider sparse and discrete data. Measures of influence computed pairwise between temporal sources naturally give rise to dense continuous-valued matrices, for instance p-values from Granger causality. Due to asymmetry or lack of positive definiteness they are no......Relational modelling classically consider sparse and discrete data. Measures of influence computed pairwise between temporal sources naturally give rise to dense continuous-valued matrices, for instance p-values from Granger causality. Due to asymmetry or lack of positive definiteness...... they are not naturally suited for kernel K-means. We propose a generative Bayesian model for dense matrices which generalize kernel K-means to consider off-diagonal interactions in matrices of interactions, and demonstrate its ability to detect structure on both artificial data and two real data sets....

  10. Modeling stochasticity in biochemical reaction networks

    Science.gov (United States)

    Constantino, P. H.; Vlysidis, M.; Smadbeck, P.; Kaznessis, Y. N.

    2016-03-01

    Small biomolecular systems are inherently stochastic. Indeed, fluctuations of molecular species are substantial in living organisms and may result in significant variation in cellular phenotypes. The chemical master equation (CME) is the most detailed mathematical model that can describe stochastic behaviors. However, because of its complexity the CME has been solved for only few, very small reaction networks. As a result, the contribution of CME-based approaches to biology has been very limited. In this review we discuss the approach of solving CME by a set of differential equations of probability moments, called moment equations. We present different approaches to produce and to solve these equations, emphasizing the use of factorial moments and the zero information entropy closure scheme. We also provide information on the stability analysis of stochastic systems. Finally, we speculate on the utility of CME-based modeling formalisms, especially in the context of synthetic biology efforts.

  11. Voter Model Perturbations and Reaction Diffusion Equations

    CERN Document Server

    Cox, J Theodore; Perkins, Edwin

    2011-01-01

    We consider particle systems that are perturbations of the voter model and show that when space and time are rescaled the system converges to a solution of a reaction diffusion equation in dimensions $d \\ge 3$. Combining this result with properties of the PDE, some methods arising from a low density super-Brownian limit theorem, and a block construction, we give general, and often asymptotically sharp, conditions for the existence of non-trivial stationary distributions, and for extinction of one type. As applications, we describe the phase diagrams of three systems when the parameters are close to the voter model: (i) a stochastic spatial Lotka-Volterra model of Neuhauser and Pacala, (ii) a model of the evolution of cooperation of Ohtsuki, Hauert, Lieberman, and Nowak, and (iii) a continuous time version of the non-linear voter model of Molofsky, Durrett, Dushoff, Griffeath, and Levin. The first application confirms a conjecture of Cox and Perkins and the second confirms a conjecture of Ohtsuki et al in the ...

  12. Modeling of Reaction Processes Controlled by Diffusion

    CERN Document Server

    Revelli, J

    2003-01-01

    Stochastic modeling is quite powerful in science and technology.The technics derived from this process have been used with great success in laser theory, biological systems and chemical reactions.Besides, they provide a theoretical framework for the analysis of experimental results on the field of particle's diffusion in ordered and disordered materials.In this work we analyze transport processes in one-dimensional fluctuating media, which are media that change their state in time.This fact induces changes in the movements of the particles giving rise to different phenomena and dynamics that will be described and analyzed in this work.We present some random walk models to describe these fluctuating media.These models include state transitions governed by different dynamical processes.We also analyze the trapping problem in a lattice by means of a simple model which predicts a resonance-like phenomenon.Also we study effective diffusion processes over surfaces due to random walks in the bulk.We consider differe...

  13. Analysis of pi (+) p -> pi (0) (eta)Delta (++) and Related Reactions

    Science.gov (United States)

    Saleem, M.; Aleem, F.; Rafique, M.

    1984-11-01

    The differential and integrated cross sections and density matrix elements for the reactions pi (+) p -> pi (0) (eta)Delta (++) and the reactions pi(-) p -> pi(-}Delta({+)) , K(+) p -> K_{0}Delta(++) and K(-) n -> bar{K}_{0}Delta(-) which are related to them by SU(2) and SU(3) are fitted by using a simple Regge pole model with phenomenological residue functions.

  14. Model for reaction kinetics in pyrolysis of wood

    Energy Technology Data Exchange (ETDEWEB)

    Ahuja, P.; Singh, P.C.; Upadhyay, S.N.; Kumar, S. [Banaras Hindu Univ., Varanasi (India)

    1996-12-31

    A reaction model for the pyrolysis of small and large particles of wood Is developed. The chemical reactions that take place when biomass is pyrolyzed are the devolatilization reactions (primary) and due to the vapour-solid interactions (secondary). In the case of small particles, when the volatiles are immediately removed by the purge gas, only primary reactions occur and the reaction model is described by weight loss and char forming reactions. The of heterogeneous secondary reactions occur in the case of large particles due to the interaction between the volatiles and the hot nascent primary char. A chain reaction mechanism of secondary char formation is proposed. The model takes both the volatiles retention time and cracking and repolymerization reactions of the vapours with the decomposing solid as well as autocatalysis into consideration. 7 refs., 3 figs., 2 tabs.

  15. Model for reaction kinetics in pyrolysis of wood

    Energy Technology Data Exchange (ETDEWEB)

    Ahuja, P.; Singh, P.C.; Upadhyay, S.N.; Kuma, S. [Banaras Hindu Univ., Varanasi (India)

    1996-12-31

    A reaction model for the pyrolysis of small and large particles of wood is developed. The chemical reactions that take place when biomass is pyrolyzed are the devolatilization reactions (primary) and due to the vapour-solid interactions (secondary). In the case of small particles, when the volatiles are immediately removed by the purge gas, only primary reactions occur and the reaction model is described by weight loss and char forming reactions. The heterogeneous secondary reactions occur in the case of large particles due to the interaction between the volatiles and the hot nascent primary char. A chain reaction mechanism of secondary char formation is proposed. The model takes both the volatiles retention time and cracking and repolymerization reactions of the vapours with the decomposing solid as well as autocatalysis into consideration. 6 refs., 3 figs., 2 tabs.

  16. Individual differences in components of reaction time distributions and their relations to working memory and intelligence.

    Science.gov (United States)

    Schmiedek, Florian; Oberauer, Klaus; Wilhelm, Oliver; Süss, Heinz-Martin; Wittmann, Werner W

    2007-08-01

    The authors bring together approaches from cognitive and individual differences psychology to model characteristics of reaction time distributions beyond measures of central tendency. Ex-Gaussian distributions and a diffusion model approach are used to describe individuals' reaction time data. The authors identified common latent factors for each of the 3 ex-Gaussian parameters and for 3 parameters central to the diffusion model using structural equation modeling for a battery of choice reaction tasks. These factors had differential relations to criterion constructs. Parameters reflecting the tail of the distribution (i.e., tau in the ex-Gaussian and drift rate in the diffusion model) were the strongest unique predictors of working memory, reasoning, and psychometric speed. Theories of controlled attention and binding are discussed as potential theoretical explanations.

  17. Nurses' workload and its relation with physiological stress reactions

    Directory of Open Access Journals (Sweden)

    Rita de Cássia de Marchi Barcellos Dalri

    2014-12-01

    Full Text Available OBJECTIVE: to analyze the relation between the workload and the physiological stress reactions among nurses working at a hospital service.METHODS: cross-sectional, correlational, quantitative study, involving 95 nurses, in 2011 and 2012. Spearman's bivariate Correlation Test was used.RESULTS: most subjects are female, between 23 and 61 years old and working between 21 and 78 hours per week. The most frequent physiological reactions were back pain, fatigue/exhaustion, stiff neck and stomach acidity, with 46.3% of the subjects presenting low and 42.1% moderate physiological stress responses. No correlation was found between the workload and the physiological stress responses.CONCLUSION: although most of the nurses work more than 36 hours/week, physiologically, they do not present high reaction levels in response to stress. These workers deal with conflicts in the vertical and horizontal relations between professionals, family members and patients. In that sense, taking care of professionals who offer health services can be a fundamental strategy, as good user care mainly depends on healthy teams.

  18. A model for reaction-assisted polymer dissolution in LIGA.

    Energy Technology Data Exchange (ETDEWEB)

    Larson, Richard S.

    2004-05-01

    A new chemically-oriented mathematical model for the development step of the LIGA process is presented. The key assumption is that the developer can react with the polymeric resist material in order to increase the solubility of the latter, thereby partially overcoming the need to reduce the polymer size. The ease with which this reaction takes place is assumed to be determined by the number of side chain scissions that occur during the x-ray exposure phase of the process. The dynamics of the dissolution process are simulated by solving the reaction-diffusion equations for this three-component, two-phase system, the three species being the unreacted and reacted polymers and the solvent. The mass fluxes are described by the multicomponent diffusion (Stefan-Maxwell) equations, and the chemical potentials are assumed to be given by the Flory-Huggins theory. Sample calculations are used to determine the dependence of the dissolution rate on key system parameters such as the reaction rate constant, polymer size, solid-phase diffusivity, and Flory-Huggins interaction parameters. A simple photochemistry model is used to relate the reaction rate constant and the polymer size to the absorbed x-ray dose. The resulting formula for the dissolution rate as a function of dose and temperature is ?t to an extensive experimental data base in order to evaluate a set of unknown global parameters. The results suggest that reaction-assisted dissolution is very important at low doses and low temperatures, the solubility of the unreacted polymer being too small for it to be dissolved at an appreciable rate. However, at high doses or at higher temperatures, the solubility is such that the reaction is no longer needed, and dissolution can take place via the conventional route. These results provide an explanation for the observed dependences of both the dissolution rate and its activation energy on the absorbed dose.

  19. Antiepileptic Drug-Related Adverse Reactions and Factors Influencing These Reactions

    Directory of Open Access Journals (Sweden)

    Parvaneh KARIMZADEH

    2013-08-01

    Full Text Available How to Cite This Article: Karimzadeh P, Bakrani V. Antiepileptic Drug-Related Adverse Reactions And Factors Influencing These Reactions. Iran J Child Neurol. 2013 Summer; 7(3:23-27. ObjectiveAccording to the basic role of drug side effects in selection ofan appropriate drug, patient compliance and the quality of life inepileptic patients, and forasmuch as new dugs with unknown side effect have been produced and introduced, necessity of this research and similar studies is explained. This study was conducted to evaluate the incidence and clinical characteristics of anti epileptic drug (AED related adverse reactions in children treated with AEDs.Material & MethodsIn this descriptive study, children less than 14 years old with AEDside effects referred to the Children’s Medical Center and MofidChilderen’s Hospital (Tehran, Iran were evaluated during 2010-2012.The informations were: sex, age, incriminating drug, type of drug side effect, incubation period, history of drug usage, and patient and family allergy history. Exclusive criterions were age more than 14 years old and reactions due to reasons other than AEDs (Food, bite, non-AEDs, etc..ResultsA total of 70 patients with AED reaction were enrolled in thisstudy. They included 26 (37% females and 44 (63 % males. The maximum rate of incidence was seen at age less than 5 years old. All the patients had cutaneous eruptions that the most common cutaneous drug eruption was maculopapular rash. The incidence of systemic and laboratory adverse events was less than similar studies. The most common culprit was phenobarbital (70% and the least common was lamotrigine (1.4%.ConclusionIn this study, we found higher rates of drug rash in patients treated with aromatic AEDs and lower rates with non-aromatic AEDs. Various endogenous and environmental factors may influence the propensity to develop these reactions. Refrences1. Blume WT, Lu¨ders HO, Mizrahi E, et al. Glossary of descriptive terminology for

  20. A computational study of pyrolysis reactions of lignin model compounds

    Science.gov (United States)

    Thomas Elder

    2010-01-01

    Enthalpies of reaction for the initial steps in the pyrolysis of lignin have been evaluated at the CBS-4m level of theory using fully substituted b-O-4 dilignols. Values for competing unimolecular decomposition reactions are consistent with results previously published for phenethyl phenyl ether models, but with lowered selectivity. Chain propagating reactions of free...

  1. Polymerization as a Model Chain Reaction

    Science.gov (United States)

    Morton, Maurice

    1973-01-01

    Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

  2. Reaction Wheel Disturbance Model Extraction Software Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Reaction wheel mechanical noise is one of the largest sources of disturbance forcing on space-based observatories. Such noise arises from mass imbalance, bearing...

  3. Reaction Wheel Disturbance Model Extraction Software Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Reaction wheel disturbances are some of the largest sources of noise on sensitive telescopes. Such wheel-induced mechanical noises are not well characterized....

  4. Modelling Chemical Reasoning to Predict and Invent Reactions.

    Science.gov (United States)

    Segler, Marwin H S; Waller, Mark P

    2016-11-11

    The ability to reason beyond established knowledge allows organic chemists to solve synthetic problems and invent novel transformations. Herein, we propose a model that mimics chemical reasoning, and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outperforms a rule-based expert system in the reaction prediction task for 180 000 randomly selected binary reactions. The data-driven model generalises even beyond known reaction types, and is thus capable of effectively (re-)discovering novel transformations (even including transition metal-catalysed reactions). Our model enables computers to infer hypotheses about reactivity and reactions by only considering the intrinsic local structure of the graph and because each single reaction prediction is typically achieved in a sub-second time frame, the model can be used as a high-throughput generator of reaction hypotheses for reaction discovery.

  5. Lateralization of Neurobiological Response in Adolescents with Post-Traumatic Stress Disorder Related to Severe Childhood Sexual Abuse: the Tri-Modal Reaction (T-MR) Model of Protection.

    Science.gov (United States)

    Mutluer, Tuba; Şar, Vedat; Kose-Demiray, Çiğdem; Arslan, Harun; Tamer, Sibel; Inal, Serap; Kaçar, Anıl Ş

    2017-03-10

    This study inquires into neurobiological response to stress and its clinical correlates among adolescents with post-traumatic stress disorder (PTSD). Structural magnetic resonance imaging (MRI) measures of cerebral anatomy were carried out on 23 female adolescents with PTSD related to severe childhood sexual abuse and 21 matched healthy controls. Clinician Administered PTSD Scale for Children and Adolescents, Adolescent Dissociative Experiences Scale, Childhood Trauma Questionnaire, Schedule for Affective Disorders and Schizophrenia for School Age Children, Beck Depression Scale, and a set of neuro-cognitive tests were administered to all participants. Compared to controls, PTSD group bilaterally had smaller amygdala, hippocampus, anterior cingulate, and thinner prefrontal cortex but normal thalamus. Further analyses within the PTSD group suggested an association between symptoms of PTSD and sizes of right brain structures including smaller amygdala but larger hippocampus and anterior cingulate. Thinner right prefrontal cortex and larger right thalamus seemed to be related to denial and response prevention, respectively. Being related to both hemispheres, dissociative amnesia was negatively associated with proportion of the right amygdala to right thalamus and to both left and right prefrontal cortex. Suggesting a neuro-protective effect against traumatic stress at least through adolescence, depersonalization-derealization and identity alteration were correlated with thicker left prefrontal cortex. Unlike the lateralization within PTSD group, correlations between regions of interest were rather symmetrical in controls. The graded response to stress seemed to be aimed at mental protection by lateralization of brain functions and possibly diminished connection between two hemispheres. A Tri-Modal Reaction (T-MR) Model of protection is proposed.

  6. Detailed reduction of reaction mechanisms for flame modeling

    Science.gov (United States)

    Wang, Hai; Frenklach, Michael

    1991-01-01

    A method for reduction of detailed chemical reaction mechanisms, introduced earlier for ignition system, was extended to laminar premixed flames. The reduction is based on testing the reaction and reaction-enthalpy rates of the 'full' reaction mechanism using a zero-dimensional model with the flame temperature profile as a constraint. The technique is demonstrated with numerical tests performed on the mechanism of methane combustion.

  7. Including lateral interactions into microkinetic models of catalytic reactions

    DEFF Research Database (Denmark)

    Hellman, Anders; Honkala, Johanna Karoliina

    2007-01-01

    In many catalytic reactions lateral interactions between adsorbates are believed to have a strong influence on the reaction rates. We apply a microkinetic model to explore the effect of lateral interactions and how to efficiently take them into account in a simple catalytic reaction. Three differ...... different approximations are investigated: site, mean-field, and quasichemical approximations. The obtained results are compared to accurate Monte Carlo numbers. In the end, we apply the approximations to a real catalytic reaction, namely, ammonia synthesis....

  8. Developed Hybrid Model for Propylene Polymerisation at Optimum Reaction Conditions

    Directory of Open Access Journals (Sweden)

    Mohammad Jakir Hossain Khan

    2016-02-01

    Full Text Available A statistical model combined with CFD (computational fluid dynamic method was used to explain the detailed phenomena of the process parameters, and a series of experiments were carried out for propylene polymerisation by varying the feed gas composition, reaction initiation temperature, and system pressure, in a fluidised bed catalytic reactor. The propylene polymerisation rate per pass was considered the response to the analysis. Response surface methodology (RSM, with a full factorial central composite experimental design, was applied to develop the model. In this study, analysis of variance (ANOVA indicated an acceptable value for the coefficient of determination and a suitable estimation of a second-order regression model. For better justification, results were also described through a three-dimensional (3D response surface and a related two-dimensional (2D contour plot. These 3D and 2D response analyses provided significant and easy to understand findings on the effect of all the considered process variables on expected findings. To diagnose the model adequacy, the mathematical relationship between the process variables and the extent of polymer conversion was established through the combination of CFD with statistical tools. All the tests showed that the model is an excellent fit with the experimental validation. The maximum extent of polymer conversion per pass was 5.98% at the set time period and with consistent catalyst and co-catalyst feed rates. The optimum conditions for maximum polymerisation was found at reaction temperature (RT 75 °C, system pressure (SP 25 bar, and 75% monomer concentration (MC. The hydrogen percentage was kept fixed at all times. The coefficient of correlation for reaction temperature, system pressure, and monomer concentration ratio, was found to be 0.932. Thus, the experimental results and model predicted values were a reliable fit at optimum process conditions. Detailed and adaptable CFD results were capable

  9. A discrete model to study reaction-diffusion-mechanics systems.

    Science.gov (United States)

    Weise, Louis D; Nash, Martyn P; Panfilov, Alexander V

    2011-01-01

    This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.

  10. A discrete model to study reaction-diffusion-mechanics systems.

    Directory of Open Access Journals (Sweden)

    Louis D Weise

    Full Text Available This article introduces a discrete reaction-diffusion-mechanics (dRDM model to study the effects of deformation on reaction-diffusion (RD processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material. Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.

  11. Do candidate reactions relate to job performance or affect criterion-related validity? A multistudy investigation of relations among reactions, selection test scores, and job performance.

    Science.gov (United States)

    McCarthy, Julie M; Van Iddekinge, Chad H; Lievens, Filip; Kung, Mei-Chuan; Sinar, Evan F; Campion, Michael A

    2013-09-01

    Considerable evidence suggests that how candidates react to selection procedures can affect their test performance and their attitudes toward the hiring organization (e.g., recommending the firm to others). However, very few studies of candidate reactions have examined one of the outcomes organizations care most about: job performance. We attempt to address this gap by developing and testing a conceptual framework that delineates whether and how candidate reactions might influence job performance. We accomplish this objective using data from 4 studies (total N = 6,480), 6 selection procedures (personality tests, job knowledge tests, cognitive ability tests, work samples, situational judgment tests, and a selection inventory), 5 key candidate reactions (anxiety, motivation, belief in tests, self-efficacy, and procedural justice), 2 contexts (industry and education), 3 continents (North America, South America, and Europe), 2 study designs (predictive and concurrent), and 4 occupational areas (medical, sales, customer service, and technological). Consistent with previous research, candidate reactions were related to test scores, and test scores were related to job performance. Further, there was some evidence that reactions affected performance indirectly through their influence on test scores. Finally, in no cases did candidate reactions affect the prediction of job performance by increasing or decreasing the criterion-related validity of test scores. Implications of these findings and avenues for future research are discussed.

  12. A time-delayed model for radiation reaction in electrodynamics

    CERN Document Server

    Faci, Sofiane; Satheeshkumar, V H

    2016-01-01

    The dynamics of a radiating charge is one of the oldest unsettled problems in classical physics. The standard Lorentz-Abraham-Dirac (LAD) equation of motion is known to suffer from several pathologies and ambiguities. This paper briefly reviews these issues, and reports on a new model that fixes these difficulties in a natural way. This model is based on a hypothesis that there is an infinitesimal time delay between action and reaction. This can be related to Feynman's regularization scheme, leading to a quasi-local QED with a natural UV cutoff, hence without the need for renormalization as the divergences are absent. Besides leading to a pathology-free equation of motion, the new model predicts a modification of the Larmor formula that is testable with current and near future ultra-intense lasers.

  13. DSMC Modeling of Flows with Recombination Reactions

    Science.gov (United States)

    2017-06-23

    rarefied gas dynamics community has seen the development of efficient algorithms for modern computer architectures16–19 which dramatically expand the area of...that participate in recombination. ACKNOWLEDGMENTS The work was supported by the Air Force Office of Sci - entific Research (Program Officer Dr. Ivett...flow,” Prog. Aerosp. Sci . 72, 66–79 (2015). 14R. D. Levine,Molecular Reaction Dynamics (Cambridge University Press, Cambridge, 2005). 15A. Alexeenko and

  14. Effect of reactions in small eddies on biomass gasification with eddy dissipation concept - Sub-grid scale reaction model.

    Science.gov (United States)

    Chen, Juhui; Yin, Weijie; Wang, Shuai; Meng, Cheng; Li, Jiuru; Qin, Bai; Yu, Guangbin

    2016-07-01

    Large-eddy simulation (LES) approach is used for gas turbulence, and eddy dissipation concept (EDC)-sub-grid scale (SGS) reaction model is employed for reactions in small eddies. The simulated gas molar fractions are in better agreement with experimental data with EDC-SGS reaction model. The effect of reactions in small eddies on biomass gasification is emphatically analyzed with EDC-SGS reaction model. The distributions of the SGS reaction rates which represent the reactions in small eddies with particles concentration and temperature are analyzed. The distributions of SGS reaction rates have the similar trend with those of total reactions rates and the values account for about 15% of the total reactions rates. The heterogeneous reaction rates with EDC-SGS reaction model are also improved during the biomass gasification process in bubbling fluidized bed.

  15. Allergic reaction related to ramipril use: a case report

    Directory of Open Access Journals (Sweden)

    Alencar Renata C

    2010-01-01

    Full Text Available Abstract Background Angiotensin-converting enzyme (ACE inhibitors are widely prescribed for patients with diabetes as a nephroprotector drug or to treat hypertension. Generally they are safe for clinical practice, but the relationship between these drugs and angioedema is known. The exact mechanism for ACE inhibitors-induced angioedema is not clear and it is still a matter of discussion. Case Report We reported a case of a 23-year-old black female with an 11 year history of type 1 diabetes, regularly monitored in the department of diabetes, in use of 0,98 UI/kg/day of human insulin, which presented an allergic reaction 24 h after ramipril use. The drug had been prescribed to treat diabetic nephropathy. There was no previous history of drug induced or alimentary allergy. The patient was instructed to discontinue the use of ramipril and oral antihistaminic drug and topical corticosteroid were prescribed. Skin biopsies were performed and confirmed the clinical hypothesis of pharmacodermy. The evaluation of ACE polymorphism identified DD genotype. Six months after the withdrawal of ramipril the patient was prescribed the angiotensin-II receptor blocker (ARB losartan as nephroprotector. She remained well without adverse reactions. Conclusions ACE inhibitors-induced angioedema is uncommon and the clinical presentation is variable with lips, tongue, oropharinge, and larynge as the most common locations. The presence of angioedema during treatment requires the immediate cessation of treatment due to the risk of possible severe complications. The case reported presented moderate symptoms, with the development of early onset edema in uncommon regions. ACE DD genotype had been associated with angioedema-ACE inhibitors induced. In patients who have experienced ACE inhibitor-related angioedema, ARB should be used cautiously used. However in the case of our patient, the prescription of losartan as nefroprotector did not result in any recurrent adverse effect.

  16. Carbonyl-Olefin Exchange Reaction and Related Chemistry

    Science.gov (United States)

    Jossifov, Christo; Kalinova, Radostina

    A new carbon—carbon double bond forming reaction (carbonyl olefin exchange reaction) mediated by transition metal catalytic systems has been discovered. The catalytic systems used (transition metal halides or oxohalides alone or in combination with Lewis acids) are active only in the case when the two reacting groups are in one molecules and are conjugated. In addition these systems accelerate other reactions which run simultaneously with the carbonyl olefin metathesis rendering a detailed investigation of the process very complicated.

  17. CHEMICAL REACTIONS SIMULATED BY GROUND-WATER-QUALITY MODELS.

    Science.gov (United States)

    Grove, David B.; Stollenwerk, Kenneth G.

    1987-01-01

    Recent literature concerning the modeling of chemical reactions during transport in ground water is examined with emphasis on sorption reactions. The theory of transport and reactions in porous media has been well documented. Numerous equations have been developed from this theory, to provide both continuous and sequential or multistep models, with the water phase considered for both mobile and immobile phases. Chemical reactions can be either equilibrium or non-equilibrium, and can be quantified in linear or non-linear mathematical forms. Non-equilibrium reactions can be separated into kinetic and diffusional rate-limiting mechanisms. Solutions to the equations are available by either analytical expressions or numerical techniques. Saturated and unsaturated batch, column, and field studies are discussed with one-dimensional, laboratory-column experiments predominating. A summary table is presented that references the various kinds of models studied and their applications in predicting chemical concentrations in ground waters.

  18. Abundances in Astrophysical Environments: Reaction Network Simulations with Reaction Rates from Many-nucleon Modeling

    Science.gov (United States)

    Amason, Charlee; Dreyfuss, Alison; Launey, Kristina; Draayer, Jerry

    2017-01-01

    We use the ab initio (first-principle) symmetry-adapted no-core shell model (SA-NCSM) to calculate reaction rates of significance to type I X-ray burst nucleosynthesis. We consider the 18O(p,γ)19F reaction, which may influence the production of fluorine, as well as the 16O(α,γ)20Ne reaction, which is key to understanding the production of heavier elements in the universe. Results are compared to those obtained in the no-core sympletic shell model (NCSpM) with a schematic interaction. We discuss how these reaction rates affect the relevant elemental abundances. We thank the NSF for supporting this work through the REU Site in Physics & Astronomy (NSF grant #1560212) at Louisiana State University. This work was also supported by the U.S. NSF (OCI-0904874, ACI -1516338) and the U.S. DOE (DE-SC0005248).

  19. Formal modeling of a system of chemical reactions under uncertainty.

    Science.gov (United States)

    Ghosh, Krishnendu; Schlipf, John

    2014-10-01

    We describe a novel formalism representing a system of chemical reactions, with imprecise rates of reactions and concentrations of chemicals, and describe a model reduction method, pruning, based on the chemical properties. We present two algorithms, midpoint approximation and interval approximation, for construction of efficient model abstractions with uncertainty in data. We evaluate computational feasibility by posing queries in computation tree logic (CTL) on a prototype of extracellular-signal-regulated kinase (ERK) pathway.

  20. Radiation reaction in binary systems in general relativity

    Science.gov (United States)

    Kennefick, Daniel John

    1997-09-01

    This thesis is concerned with current problems in, and historical aspects of, the problem of radiation reaction in stellar binary systems in general relativity. Part I addresses current issues in the orbital evolution due to gravitational radiation damping of compact binaries. A particular focus is on the inspiral of small bodies orbiting large black holes, employing a perturbation formalism. In addition, the merger, at the end of the insprial, of comparable mass compact binaries, such as neutron star binaries is also discussed. The emphasis of Part I is on providing detailed descriptions of sources and signals with a view to optimising signal analysis in gravitational wave detectors, whether ground- or space- based interferometers, or resonant mass detectors. Part II of the thesis examines the historical controversies surrounding the problem of gravitational waves, and gravitational radiation damping in stellar binaries. In particular, it focuses on debates in the mid 20th-century on whether binary star systems would really exhibit this type of damping and emit gravitational waves, and on the 'quadrupole formula controversy' of the 1970s and 1980s, on the question whether the standard formular describing energy loss due to emission of gravitational waves was correctly derived for such systems. The study shed light on the role of analogy in science, especially where its use is controversial, on the importance of style in physics and on the problem of identity in science, as the use of history as a rhetorical device in controversial debate is examined. The concept of the Theoretician's Regress is introduced to explain the difficulty encountered by relativists in closing debate in this controversy, which persisted in one forms or another for several decades.

  1. Principle Generalized Net Model of a Human Stress Reaction

    Directory of Open Access Journals (Sweden)

    Anthony Shannon

    2008-04-01

    Full Text Available The present study was aimed at investigating the mechanism of a human stress reaction by means of Generalized Nets (GNs. A principle GN-model of the main structures, organs and systems of the human body taking part in the acute and chronic reaction of the organism to a stress stimulus is generated. A possible application of the GN-model of the human stress reaction for testing the effect of known or newly synthesized pharmacological products as well as of food supplements is discussed.

  2. Modeling Electric Double-Layers Including Chemical Reaction Effects

    DEFF Research Database (Denmark)

    Paz-Garcia, Juan Manuel; Johannesson, Björn; Ottosen, Lisbeth M.

    2014-01-01

    A physicochemical and numerical model for the transient formation of an electric double-layer between an electrolyte and a chemically-active flat surface is presented, based on a finite elements integration of the nonlinear Nernst-Planck-Poisson model including chemical reactions. The model works...

  3. Turing patterns in a reaction-diffusion model with the Degn-Harrison reaction scheme

    Science.gov (United States)

    Li, Shanbing; Wu, Jianhua; Dong, Yaying

    2015-09-01

    In this paper, we consider a reaction-diffusion model with Degn-Harrison reaction scheme. Some fundamental analytic properties of nonconstant positive solutions are first investigated. We next study the stability of constant steady-state solution to both ODE and PDE models. Our result also indicates that if either the size of the reactor or the effective diffusion rate is large enough, then the system does not admit nonconstant positive solutions. Finally, we establish the global structure of steady-state bifurcations from simple eigenvalues by bifurcation theory and the local structure of the steady-state bifurcations from double eigenvalues by the techniques of space decomposition and implicit function theorem.

  4. Nuclear reaction modeling, verification experiments, and applications

    Energy Technology Data Exchange (ETDEWEB)

    Dietrich, F.S.

    1995-10-01

    This presentation summarized the recent accomplishments and future promise of the neutron nuclear physics program at the Manuel Lujan Jr. Neutron Scatter Center (MLNSC) and the Weapons Neutron Research (WNR) facility. The unique capabilities of the spallation sources enable a broad range of experiments in weapons-related physics, basic science, nuclear technology, industrial applications, and medical physics.

  5. Regimes of chemical reaction waves initiated by nonuniform initial conditions for detailed chemical reaction models.

    Science.gov (United States)

    Liberman, M A; Kiverin, A D; Ivanov, M F

    2012-05-01

    Regimes of chemical reaction wave propagation initiated by initial temperature nonuniformity in gaseous mixtures, whose chemistry is governed by chain-branching kinetics, are studied using a multispecies transport model and a detailed chemical model. Possible regimes of reaction wave propagation are identified for stoichiometric hydrogen-oxygen and hydrogen-air mixtures in a wide range of initial pressures and temperature levels, depending on the initial non-uniformity steepness. The limits of the regimes of reaction wave propagation depend upon the values of the spontaneous wave speed and the characteristic velocities of the problem. It is shown that one-step kinetics cannot reproduce either quantitative neither qualitative features of the ignition process in real gaseous mixtures because the difference between the induction time and the time when the exothermic reaction begins significantly affects the ignition, evolution, and coupling of the spontaneous reaction wave and the pressure wave, especially at lower temperatures. We show that all the regimes initiated by the temperature gradient occur for much shallower temperature gradients than predicted by a one-step model. The difference is very large for lower initial pressures and for slowly reacting mixtures. In this way the paper provides an answer to questions, important in practice, about the ignition energy, its distribution, and the scale of the initial nonuniformity required for ignition in one or another regime of combustion wave propagation.

  6. Biomass torrefaction: modeling of reaction thermochemistry.

    Science.gov (United States)

    Bates, Richard B; Ghoniem, Ahmed F

    2013-04-01

    Based on the evolution of volatile and solid products predicted by a previous model for willow torrefaction (Bates and Ghoniem, 2012) a thermochemical model has been developed to describe their thermal, chemical, and physical properties as well as the rates of heat release. The first stage of torrefaction, associated with hemicellulose decomposition, is exothermic releasing between 40 and 280 kJ/kginitial. The second stage is associated with the decomposition of the remaining lignocellulosic components, completes over a longer period, and is predicted to be either endothermic or exothermic depending on the temperature and assumed solid properties. Cumulative heat release increases with the degree of torrefaction quantified by the mass loss. The rate of mass loss and rate of heat release increase with higher temperatures. The higher heating value of volatiles produced during torrefaction was estimated to be between 4.4 and 16 MJ/kg increasing with the level of mass loss.

  7. An Equilibrium-Based Model of Gas Reaction and Detonation

    Energy Technology Data Exchange (ETDEWEB)

    Trowbridge, L.D.

    2000-04-01

    During gaseous diffusion plant operations, conditions leading to the formation of flammable gas mixtures may occasionally arise. Currently, these could consist of the evaporative coolant CFC-114 and fluorinating agents such as F2 and ClF3. Replacement of CFC-114 with a non-ozone-depleting substitute is planned. Consequently, in the future, the substitute coolant must also be considered as a potential fuel in flammable gas mixtures. Two questions of practical interest arise: (1) can a particular mixture sustain and propagate a flame if ignited, and (2) what is the maximum pressure that can be generated by the burning (and possibly exploding) gas mixture, should it ignite? Experimental data on these systems, particularly for the newer coolant candidates, are limited. To assist in answering these questions, a mathematical model was developed to serve as a tool for predicting the potential detonation pressures and for estimating the composition limits of flammability for these systems based on empirical correlations between gas mixture thermodynamics and flammability for known systems. The present model uses the thermodynamic equilibrium to determine the reaction endpoint of a reactive gas mixture and uses detonation theory to estimate an upper bound to the pressure that could be generated upon ignition. The model described and documented in this report is an extended version of related models developed in 1992 and 1999.

  8. Biogeochemical Transport and Reaction Model (BeTR) v1

    Energy Technology Data Exchange (ETDEWEB)

    2016-04-18

    The Biogeochemical Transport and Reaction Model (BeTR) is a F90 code that enables reactive transport modeling in land modules of earth system models (e.g. CESM, ACME). The code adopts the Objective-Oriented-Design, and allows users to plug in their own biogeochemical (BGC) formulations/codes, and compare them to other existing BGC codes in those ESMs. The code takes information of soil physics variables, such as variables, such as temperature, moisture, soil density profile; water flow, etc., from a land model to track the movement of different chemicals in presence of biogeochemical reactions.

  9. How is entropy production rate related to chemical reaction rate?

    CERN Document Server

    Banerjee, Kinshuk

    2013-01-01

    The entropy production rate is a key quantity in irreversible thermodynamics. In this work, we concentrate on the realization of entropy production rate in chemical reaction systems in terms of the experimentally measurable reaction rate. Both triangular and linear networks have been studied. They attain either thermodynamic equilibrium or a non-equilibrium steady state, under suitable external constraints. We have shown that the entropy production rate is proportional to the square of the reaction velocity only around equilibrium and not any arbitrary non-equilibrium steady state. This feature can act as a guide in revealing the nature of a steady state, very much like the minimum entropy production principle. A discussion on this point has also been presented.

  10. Kinetic model for hydroisomerization reaction of C8-aromatics

    Institute of Scientific and Technical Information of China (English)

    Ouguan XU; Hongye SU; Xiaoming JIN; Jian CHU

    2008-01-01

    Based on the reported reaction networks, a novel six-component hydroisomerization reaction net-work with a new lumped species including C8-naphthenes and Cs-paraffins is proposed and a kinetic model for a commercial unit is also developed. An empirical catalyst deactivation function is incorporated into the model accounting for the loss in activity because of coke forma-tion on the catalyst surface during the long-term opera-tion. The Runge-Kutta method is used to solve the ordinary differential equations of the model. The reaction kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential vari-able metric optimization method (BFGS). The kinetic model is validated by an industrial unit with sets of plant data under different operating conditions and simulation results show a good agreement between the model predic-tions and the plant observations.

  11. Relative survival multistate Markov model.

    Science.gov (United States)

    Huszti, Ella; Abrahamowicz, Michal; Alioum, Ahmadou; Binquet, Christine; Quantin, Catherine

    2012-02-10

    Prognostic studies often have to deal with two important challenges: (i) separating effects of predictions on different 'competing' events and (ii) uncertainty about cause of death. Multistate Markov models permit multivariable analyses of competing risks of, for example, mortality versus disease recurrence. On the other hand, relative survival methods help estimate disease-specific mortality risks even in the absence of data on causes of death. In this paper, we propose a new Markov relative survival (MRS) model that attempts to combine these two methodologies. Our MRS model extends the existing multistate Markov piecewise constant intensities model to relative survival modeling. The intensity of transitions leading to death in the MRS model is modeled as the sum of an estimable excess hazard of mortality from the disease of interest and an 'offset' defined as the expected hazard of all-cause 'natural' mortality obtained from relevant life-tables. We evaluate the new MRS model through simulations, with a design based on registry-based prognostic studies of colon cancer. Simulation results show almost unbiased estimates of prognostic factor effects for the MRS model. We also applied the new MRS model to reassess the role of prognostic factors for mortality in a study of colorectal cancer. The MRS model considerably reduces the bias observed with the conventional Markov model that does not permit accounting for unknown causes of death, especially if the 'true' effects of a prognostic factor on the two types of mortality differ substantially.

  12. A Lattice Boltzmann Model for Oscillating Reaction-Diffusion

    Science.gov (United States)

    Rodríguez-Romo, Suemi; Ibañez-Orozco, Oscar; Sosa-Herrera, Antonio

    2016-07-01

    A computational algorithm based on the lattice Boltzmann method (LBM) is proposed to model reaction-diffusion systems. In this paper, we focus on how nonlinear chemical oscillators like Belousov-Zhabotinsky (BZ) and the chlorite-iodide-malonic acid (CIMA) reactions can be modeled by LBM and provide with new insight into the nature and applications of oscillating reactions. We use Gaussian pulse initial concentrations of sulfuric acid in different places of a bidimensional reactor and nondiffusive boundary walls. We clearly show how these systems evolve to a chaotic attractor and produce specific pattern images that are portrayed in the reactions trajectory to the corresponding chaotic attractor and can be used in robotic control.

  13. Reaction Networks For Interstellar Chemical Modelling: Improvements and Challenges

    CERN Document Server

    Wakelam, V; Herbst, E; Troe, J; Geppert, W; Linnartz, H; Oberg, K; Roueff, E; Agundez, M; Pernot, P; Cuppen, H M; Loison, J C; Talbi, D

    2010-01-01

    We survey the current situation regarding chemical modelling of the synthesis of molecules in the interstellar medium. The present state of knowledge concerning the rate coefficients and their uncertainties for the major gas-phase processes -- ion-neutral reactions, neutral-neutral reactions, radiative association, and dissociative recombination -- is reviewed. Emphasis is placed on those reactions that have been identified, by sensitivity analyses, as 'crucial' in determining the predicted abundances of the species observed in the interstellar medium. These sensitivity analyses have been carried out for gas-phase models of three representative, molecule-rich, astronomical sources: the cold dense molecular clouds TMC-1 and L134N, and the expanding circumstellar envelope IRC +10216. Our review has led to the proposal of new values and uncertainties for the rate coefficients of many of the key reactions. The impact of these new data on the predicted abundances in TMC-1 and L134N is reported. Interstellar dust p...

  14. Uncertainty quantification for quantum chemical models of complex reaction networks.

    Science.gov (United States)

    Proppe, Jonny; Husch, Tamara; Simm, Gregor N; Reiher, Markus

    2016-12-22

    For the quantitative understanding of complex chemical reaction mechanisms, it is, in general, necessary to accurately determine the corresponding free energy surface and to solve the resulting continuous-time reaction rate equations for a continuous state space. For a general (complex) reaction network, it is computationally hard to fulfill these two requirements. However, it is possible to approximately address these challenges in a physically consistent way. On the one hand, it may be sufficient to consider approximate free energies if a reliable uncertainty measure can be provided. On the other hand, a highly resolved time evolution may not be necessary to still determine quantitative fluxes in a reaction network if one is interested in specific time scales. In this paper, we present discrete-time kinetic simulations in discrete state space taking free energy uncertainties into account. The method builds upon thermo-chemical data obtained from electronic structure calculations in a condensed-phase model. Our kinetic approach supports the analysis of general reaction networks spanning multiple time scales, which is here demonstrated for the example of the formose reaction. An important application of our approach is the detection of regions in a reaction network which require further investigation, given the uncertainties introduced by both approximate electronic structure methods and kinetic models. Such cases can then be studied in greater detail with more sophisticated first-principles calculations and kinetic simulations.

  15. Modeling Corrosion Reactions of Steel in a Dilute Carbonate Solution

    Science.gov (United States)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2016-02-01

    This research models the corrosion reactions of a high-strength steel in an aerated, dilute, carbonate solution during a single-cycle voltammetry. Based on a previous study (Eliyan et al. in J Mater Eng Perform 24(6):1-8, 2015) and a literature survey, the corrosion reactions of the cathodic reduction, anodic dissolution, and passivation, as well as the interfacial interactions and the chemistry of the corrosion products are illustrated in schematics. The paper provides a visual guide on the corrosion reactions for steel in carbonate solutions based on the available mechanistic details that were reported and are still being investigated in literature.

  16. Chemical reaction networks as a model to describe UVC- and radiolytically-induced reactions of simple compounds.

    Science.gov (United States)

    Dondi, Daniele; Merli, Daniele; Albini, Angelo; Zeffiro, Alberto; Serpone, Nick

    2012-05-01

    When a chemical system is submitted to high energy sources (UV, ionizing radiation, plasma sparks, etc.), as is expected to be the case of prebiotic chemistry studies, a plethora of reactive intermediates could form. If oxygen is present in excess, carbon dioxide and water are the major products. More interesting is the case of reducing conditions where synthetic pathways are also possible. This article examines the theoretical modeling of such systems with random-generated chemical networks. Four types of random-generated chemical networks were considered that originated from a combination of two connection topologies (viz., Poisson and scale-free) with reversible and irreversible chemical reactions. The results were analyzed taking into account the number of the most abundant products required for reaching 50% of the total number of moles of compounds at equilibrium, as this may be related to an actual problem of complex mixture analysis. The model accounts for multi-component reaction systems with no a priori knowledge of reacting species and the intermediates involved if system components are sufficiently interconnected. The approach taken is relevant to an earlier study on reactions that may have occurred in prebiotic systems where only a few compounds were detected. A validation of the model was attained on the basis of results of UVC and radiolytic reactions of prebiotic mixtures of low molecular weight compounds likely present on the primeval Earth.

  17. Theoretical Model Calculation for d + 8Li Reaction

    Institute of Scientific and Technical Information of China (English)

    HAN Yin-Lu; GUO Hai-Rui; ZHANG Yue; ZHANG Jing-Shang

    2008-01-01

    Based on the theoretical models for light nuclei, the calculations of reaction cross sections and the angular distributions for d+8Li reaction are performed. Since all of the particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism is taken into account. The three-body break-up process and the recoil effect are involved. The theoretical calculated results are compared to existing experimental data.

  18. Improvement and extension of the generalized hard-sphere reaction probability model.

    Science.gov (United States)

    Schübler, M A; Petkow, D; Herdrich, G

    2012-04-01

    The GHS (Generalized Hard Sphere)-based standard reaction probability model commonly used in probabilistic particle methods is evaluated. We show that the original model has no general validity with respect to the molecular reaction. Mathematical consistency exists only for reactions with vanishing activation energy. For small energies close to the activation threshold the individual reaction probability for the special case of associative ionization of atomic nitrogen diverges. This makes the model extremely expensive, and nonphysical. An improved model is derived, and its implementation is verified on basis of the aforementioned reaction. Both models converge to the same value at large energies. The relative error of the original model with respect to the new model is independent of the particle pairing and, hence, of the reaction type. The error is smaller than 1% for collision energies in excess of 200 times the activation energy. For typical simulation problems like atmospheric high-enthalpy entry flows (assuming heavy-particle temperatures on the order of 10000 K) the relative error is in the order of 10(5)%.

  19. An Investigation of Model Catalyzed Hydrocarbon Formation Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Tysoe, W. T.

    2001-05-02

    Work was focused on two areas aimed at understanding the chemistry of realistic catalytic systems: (1) The synthesis and characterization of model supported olefin metathesis catalysts. (2) Understanding the role of the carbonaceous layer present on Pd(111) single crystal model catalysts during reaction.

  20. Model-order reduction of biochemical reaction networks

    NARCIS (Netherlands)

    Rao, Shodhan; Schaft, Arjan van der; Eunen, Karen van; Bakker, Barbara M.; Jayawardhana, Bayu

    2013-01-01

    In this paper we propose a model-order reduction method for chemical reaction networks governed by general enzyme kinetics, including the mass-action and Michaelis-Menten kinetics. The model-order reduction method is based on the Kron reduction of the weighted Laplacian matrix which describes the gr

  1. Object-relational mapping model

    OpenAIRE

    Žukauskas, Arūnas

    2007-01-01

    This work is analyzing problems, arising because of sematical gap between relational and object-oriented approaches and discusses how to utilize object-relational mapping for solving this problem. After analysis of object-relational mapping framework (further – ORM) principles and features of existing ORM frameworks a model is suggested, that allows to implement ORM by utilizing MVP principles in a way that retains major portion of both approach pros and is perfect for transitioning existing ...

  2. The fundamental Diagram of Pedestrian Model with Slow Reaction

    CERN Document Server

    Fang, Jun; Hu, Hao; Xu, Zhaohui; Li, Huan

    2015-01-01

    The slow-to-start models are a classical cellular automata model in simulating vehicle traffic. However, to our knowledge, the slow-to-start effect has not considered in modeling pedestrian dynamic. We verify the similar behavior between pedestrian and vehicle, and propose an new lattice gas (LG) model called the slow reaction (SR) model to describe the pedestrian's delayed reaction in single-file movement. We simulate and reproduce the Seyfried's field experiments at the research centre Julich, and use its empirical data to validate our SR model. We compare the SR model with the standard LG model. We test different probability of slow reaction ps in SR model and found the simulation data of ps=0.3 fit the empirical data best. The RMS error of mean velocity of SR model is smaller than that of standard LG model. In the range of ps=0.1~0.3, our fundamental diagram between velocity and density by simulation coincides with field experiments. The distribution of individual velocity in fundamental diagram in SR mod...

  3. Dynamic order reduction of thin-film deposition kinetics models: A reaction factorization approach

    Energy Technology Data Exchange (ETDEWEB)

    Adomaitis, Raymond A., E-mail: adomaiti@umd.edu [Department of Chemical and Biomolecular Engineering, Institute for Systems Research, University of Maryland, College Park, Maryland 20742 (United States)

    2016-01-15

    A set of numerical tools for the analysis and dynamic dimension reduction of chemical vapor and atomic layer deposition (ALD) surface reaction models is developed in this work. The approach is based on a two-step process where in the first, the chemical species surface balance dynamic equations are factored to effectively decouple the (nonlinear) reaction rates, a process that eliminates redundant dynamic modes and that identifies conserved quantities. If successful, the second phase is implemented to factor out redundant dynamic modes when species relatively minor in concentration are omitted; if unsuccessful, the technique points to potential model structural problems. An alumina ALD process is used for an example consisting of 19 reactions and 23 surface and gas-phase species. Using the approach developed, the model is reduced by nineteen modes to a four-dimensional dynamic system without any knowledge of the reaction rate values. Results are interpreted in the context of potential model validation studies.

  4. A Reaction-based Diagonalization Approach to Modeling Surface Water Quality

    Science.gov (United States)

    Yu, J.; Yeh, G.; Zhang, F.; Wu, T.; Hu, G.

    2005-12-01

    makes the inclusion of arbitrary number of fast and kinetic reactions relatively easy, and, more importantly, it enables the formulation and parameterization of kinetic reactions one by one. To demonstrate the flexibility and generality, the eutrophication model in WASP5, QUAL2E, and CE-QUAL-ICM are recast in the mode of reaction networks. This illustrates that the model embeds the most widely used water quality models as specific examples. Based on these three examples, the deficiencies of current practices in water quality modeling are discussed and the actions that must be taken to improve these practices are addressed.

  5. ALTERNATING DIRECTION FINITE ELEMENT METHOD FOR SOME REACTION DIFFUSION MODELS

    Institute of Scientific and Technical Information of China (English)

    江成顺; 刘蕴贤; 沈永明

    2004-01-01

    This paper is concerned with some nonlinear reaction - diffusion models. To solve this kind of models, the modified Laplace finite element scheme and the alternating direction finite element scheme are established for the system of patrical differential equations. Besides, the finite difference method is utilized for the ordinary differential equation in the models. Moreover, by the theory and technique of prior estimates for the differential equations, the convergence analyses and the optimal L2- norm error estimates are demonstrated.

  6. Quantum toy model for black-hole back-reaction

    CERN Document Server

    Maia, Clovis

    2007-01-01

    We propose a simple quantum field theoretical toy model for black hole evaporation and study the back-reaction of Hawking radiation onto the classical background. It turns out that the horizon is also ``pushed back'' in this situation (i.e., the interior region shrinks) but this back-reaction is not caused by energy conservation but by momentum balance. The effective heat capacity and the induced entropy variation can have both signs -- depending on the parameters of the model. PACS: 04.62.+v, 04.70.Dy.

  7. On the Methods for Constructing Meson-Baryon Reaction Models within Relativistic Quantum Field Theory

    Energy Technology Data Exchange (ETDEWEB)

    B. Julia-Diaz, H. Kamano, T.-S. H. Lee, A. Matsuyama, T. Sato, N. Suzuki

    2009-04-01

    Within the relativistic quantum field theory, we analyze the differences between the $\\pi N$ reaction models constructed from using (1) three-dimensional reductions of Bethe-Salpeter Equation, (2) method of unitary transformation, and (3) time-ordered perturbation theory. Their relations with the approach based on the dispersion relations of S-matrix theory are dicusssed.

  8. College students' behavioral reactions upon witnessing relational peer aggression.

    Science.gov (United States)

    You, Ji-In; Bellmore, Amy

    2014-01-01

    With a sample of 228 college students (82.5% females) from the Midwestern United States, individual factors that contribute to emerging adults' behavioral responses when witnessing relational aggression among their peers were explored. The experience of witnessing relational aggression was found to be systematically associated with college students' behavioral responses to relational aggression through two social cognitive processes: normative beliefs about relational aggression and susceptibility to peer influence. The experience of witnessing relational aggression was associated with defending behavior through normative beliefs about relational aggression and both assisting and reinforcing behavior through normative beliefs about relational aggression and susceptibility to peer influence. The experience of witnessing relational aggression was also associated with onlooking behavior through normative beliefs about relational aggression. The findings indicate that exposure to relational aggression as a witness may influence witness responses because of the way such exposure may shape specific social cognitions. The potential for using the study findings for promoting effective witness interventions among college students is discussed.

  9. Modelling population growth with delayed nonlocal reaction in 2-dimensions.

    Science.gov (United States)

    Liang, Dong; Wu, Jianhong; Zhang, Fan

    2005-01-01

    In this paper, we consider the population growth of a single species living in a two-dimensional spatial domain. New reaction-difusion equation models with delayed nonlocal reaction are developed in two-dimensional bounded domains combining diferent boundary conditions. The important feature of the models is the reflection of the joint efect of the difusion dynamics and the nonlocal maturation delayed efect. We consider and ana- lyze numerical solutions of the mature population dynamics with some wellknown birth functions. In particular, we observe and study the occurrences of asymptotically stable steady state solutions and periodic waves for the two-dimensional problems with nonlocal delayed reaction. We also investigate numerically the efects of various parameters on the period, the peak and the shape of the periodic wave as well as the shape of the asymptotically stable steady state solution.

  10. Elastodynamic modeling and joint reaction prediction for 3-PRS PKM

    Institute of Scientific and Technical Information of China (English)

    张俊; 赵艳芹

    2015-01-01

    To gain a thorough understanding of the load state of parallel kinematic machines (PKMs), a methodology of elastodynamic modeling and joint reaction prediction is proposed. For this purpose, a Sprint Z3 model is used as a case study to illustrate the process of joint reaction analysis. The substructure synthesis method is applied to deriving an analytical elastodynamic model for the 3-PRS PKM device, in which the compliances of limbs and joints are considered. Each limb assembly is modeled as a spatial beam with non-uniform cross-section supported by lumped virtual springs at the centers of revolute and spherical joints. By introducing the deformation compatibility conditions between the limbs and the platform, the governing equations of motion of the system are obtained. After degenerating the governing equations into quasi-static equations, the effects of the gravity on system deflections and joint reactions are investigated with the purpose of providing useful information for the kinematic calibration and component strength calculations as well as structural optimizations of the 3-PRS PKM module. The simulation results indicate that the elastic deformation of the moving platform in the direction of gravity caused by gravity is quite large and cannot be ignored. Meanwhile, the distributions of joint reactions are axisymmetric and position-dependent. It is worthy to note that the proposed elastodynamic modeling method combines the benefits of accuracy of finite element method and concision of analytical method so that it can be used to predict the stiffness characteristics and joint reactions of a PKM throughout its entire workspace in a quick and accurate manner. Moreover, the present model can also be easily applied to evaluating the overall rigidity performance as well as statics of other PKMs with high efficiency after minor modifications.

  11. A Multiple Reaction Modelling Framework for Microbial Electrochemical Technologies

    Science.gov (United States)

    Oyetunde, Tolutola; Sarma, Priyangshu M.; Ahmad, Farrukh; Rodríguez, Jorge

    2017-01-01

    A mathematical model for the theoretical evaluation of microbial electrochemical technologies (METs) is presented that incorporates a detailed physico-chemical framework, includes multiple reactions (both at the electrodes and in the bulk phase) and involves a variety of microbial functional groups. The model is applied to two theoretical case studies: (i) A microbial electrolysis cell (MEC) for continuous anodic volatile fatty acids (VFA) oxidation and cathodic VFA reduction to alcohols, for which the theoretical system response to changes in applied voltage and VFA feed ratio (anode-to-cathode) as well as membrane type are investigated. This case involves multiple parallel electrode reactions in both anode and cathode compartments; (ii) A microbial fuel cell (MFC) for cathodic perchlorate reduction, in which the theoretical impact of feed flow rates and concentrations on the overall system performance are investigated. This case involves multiple electrode reactions in series in the cathode compartment. The model structure captures interactions between important system variables based on first principles and provides a platform for the dynamic description of METs involving electrode reactions both in parallel and in series and in both MFC and MEC configurations. Such a theoretical modelling approach, largely based on first principles, appears promising in the development and testing of MET control and optimization strategies. PMID:28054959

  12. Neutrino nucleus reactions within the GiBUU model

    CERN Document Server

    Lalakulich, O; Mosel, U

    2011-01-01

    The GiBUU model, which implements all reaction channels relevant at medium neutrino energy, is used to investigate the neutrino and antineutrino scattering on iron. Results for integrated cross sections are compared with NOMAD and MINOS data. It is shown, that final state interaction can noticeably change the spectra of the outgoing hadrons. Predictions for the Miner$\

  13. Modeling of calcium-based sorbent reactions with sulfur dioxide

    Directory of Open Access Journals (Sweden)

    Tomanović Ivan

    2015-01-01

    Full Text Available A mathematical model of calcium sorbent reactions for simulation of sulfur dioxide reduction from pulverized coal combustion fl e gasses is developed, implemented within numerical code and validated against available measurements under controlled conditions. The model attempts to closely resemble reactions of calcination, sintering and sulfation, occurring during the sorbent particles motion in the furnace. The sulfation is based on PSSM (Partially Sintered Spheres Model, coupled with simulated particle calcination and sintering. Complex geometry of the particle is taken into account, with the assumption that it consists of spherical grains in contact with each other. Numerical simulations of drop down tube reactors were performed for both CaCO3 and Ca(OH2 sorbent particles and results were compared with available experimental data from literature. The sorbent reactions model will be further used for simulations of desulfurization reactions in turbulent gas-particle flow under coalcombustion conditions. [Projekat Ministarstva nauke Republike Srbije, br. TR-33018: Increase in energy and ecology efficiency of processes in pulverized coal-fired furnace and optimization of utility steam boiler air preheater by using in-house developed software tools

  14. Python framework for kinetic modeling of electronically excited reaction pathways

    Science.gov (United States)

    Verboncoeur, John; Parsey, Guy; Guclu, Yaman; Christlieb, Andrew

    2012-10-01

    The use of plasma energy to enhance and control the chemical reactions during combustion, a technology referred to as ``plasma assisted combustion'' (PAC), can result in a variety of beneficial effects: e.g. stable lean operation, pollution reduction, and wider range of p-T operating conditions. While experimental evidence abounds, theoretical understanding of PAC is at best incomplete, and numerical tools still lack in reliable predictive capabilities. In the context of a joint experimental-numerical effort at Michigan State University, we present here an open-source modular Python framework dedicated to the dynamic optimization of non-equilibrium PAC systems. Multiple sources of experimental reaction data, e.g. reaction rates, cross-sections and oscillator strengths, are used in order to quantify the effect of data uncertainty and limiting assumptions. A collisional-radiative model (CRM) is implemented to organize reactions by importance and as a potential means of measuring a non-Maxwellian electron energy distribution function (EEDF), when coupled to optical emission spectroscopy data. Finally, we explore scaling laws in PAC parameter space using a kinetic global model (KGM) accelerated with CRM optimized reaction sequences and sparse stiff integrators.

  15. A Model for International Relations

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Since the end of the Cold War, the new international environment has required a new model of relationship between major countries. The basis of the new relations is to safeguard one's own national interests while respecting the national interests of the other country. The process of establishing such rela-

  16. Cohabitation reaction-diffusion model for virus focal infections

    Science.gov (United States)

    Amor, Daniel R.; Fort, Joaquim

    2014-12-01

    The propagation of virus infection fronts has been typically modeled using a set of classical (noncohabitation) reaction-diffusion equations for interacting species. However, for some single-species systems it has been recently shown that noncohabitation reaction-diffusion equations may lead to unrealistic descriptions. We argue that previous virus infection models also have this limitation, because they assume that a virion can simultaneously reproduce inside a cell and diffuse away from it. For this reason, we build a several-species cohabitation model that does not have this limitation. Furthermore, we perform a sensitivity analysis for the most relevant parameters of the model, and we compare the predicted infection speed with observed data for two different strains of the T7 virus.

  17. Modeling violent reaction following low speed impact on confined explosives

    Science.gov (United States)

    Curtis, John Philip; Jones, Andrew; Hughes, Christopher; Reaugh, John

    2012-03-01

    To ensure the safe storage and deployment of explosives it is important to understand the mechanisms that give rise to ignition and reaction growth in low speed impacts. The High Explosive Response to Mechanical Stimulus (HERMES) material model, integrated in the Lagrangian code LSDYNA, has been developed to model the progress of the reaction after such an impact. The low speed impact characteristics of an HMX based formulation have been examined using the AWE Steven Test. Axisymmetric simulations of an HMX explosive in the AWE Steven Test have been performed. A sensitivity study included the influence of friction, mesh resolution, and confinement. By comparing the experimental and calculated results, key model parameters which determine the explosive's response in this configuration have been identified. The model qualitatively predicts the point of ignition within the vehicle. Future refinements are discussed.

  18. Longitudinal relations among parents' reactions to children's negative emotions, effortful control, and math achievement in early elementary school.

    Science.gov (United States)

    Swanson, Jodi; Valiente, Carlos; Lemery-Chalfant, Kathryn; Bradley, Robert H; Eggum-Wilkens, Natalie D

    2014-01-01

    Panel mediation models and fixed-effects models were used to explore longitudinal relations among parents' reactions to children's displays of negative emotions, children's effortful control (EC), and children's math achievement (N = 291; M age in fall of kindergarten = 5.66 years, SD = .39 year) across kindergarten through second grade. Parents reported their reactions and children's EC. Math achievement was assessed with a standardized achievement test. First-grade EC mediated the relation between parents' reactions at kindergarten and second-grade math achievement, beyond stability in constructs across study years. Panel mediation model results suggested that socialization of EC may be one method of promoting math achievement in early school; however, when all omitted time-invariant covariates of EC and math achievement were controlled, first-grade EC no longer predicted second-grade math achievement. © 2014 The Authors. Child Development © 2014 Society for Research in Child Development, Inc.

  19. Complex reaction noise in a molecular quasispecies model

    Science.gov (United States)

    Hochberg, David; Zorzano, María-Paz; Morán, Federico

    2006-05-01

    We have derived exact Langevin equations for a model of quasispecies dynamics. The inherent multiplicative reaction noise is complex and its statistical properties are specified completely. The numerical simulation of the complex Langevin equations is carried out using the Cholesky decomposition for the noise covariance matrix. This internal noise, which is due to diffusion-limited reactions, produces unavoidable spatio-temporal density fluctuations about the mean field value. In two dimensions, this noise strictly vanishes only in the perfectly mixed limit, a situation difficult to attain in practice.

  20. Latino/Hispanic Alzheimer’s caregivers experiencing dementia-related dressing issues: corroboration of the Preservation of Self model and reactions to a “smart dresser” computer-based dressing aid

    Science.gov (United States)

    Mahoney, Diane Feeney; Coon, David W; Lozano, Cecil

    2016-01-01

    Objective To gain an understanding of Latino/Hispanic caregivers’ dementia-related dressing issues, their impressions of using a “smart” context-aware dresser to coach dressing, and recommendations to improve its acceptability. Method The same Latina moderator conducted all the caregiver focus groups. She followed a semi-structured interview guide that was previously used with White and African American family caregivers who experienced Alzheimer’s disease related dressing challenges. From that study, the Preservation of Self model emerged. Using a deductive qualitative analytic approach, we applied the thematic domains from the Preservation of Self model to ascertain relevance to Latino/Hispanic caregivers. Results Twenty Latino/Hispanic experienced caregivers were recruited, enrolled, and participated in one of three focus groups. The majority were female (75%) and either the spouse (25%) or adult child (35%). Striking similarities occurred with the dressing challenges and alignment with the Preservation of Self model. Ethnic differences arose in concerns over assimilation weakening the Latino culture of family caregiving. Regional clothing preferences were noted. Technology improvement recommendations for our system, called DRESS, included developing bilingual prompting dialogs and video modules using the local vernacular to improve cultural sensitivity. Caregivers identified the potential for the technology to enable user privacy, empowerment, and exercise as well as offering respite time for themselves. Conclusion Findings suggest dementia-related dressing issues were shared in common by different racial/ethnic groups but the response to them was influenced by cultural dynamics. For the first time Latino/Hispanic voices are heard to reflect their positive technology impressions, concerns, and recommendations in order to begin to address the cultural digital disparities divide. PMID:27928511

  1. MetRxn: a knowledgebase of metabolites and reactions spanning metabolic models and databases

    Directory of Open Access Journals (Sweden)

    Kumar Akhil

    2012-01-01

    Full Text Available Abstract Background Increasingly, metabolite and reaction information is organized in the form of genome-scale metabolic reconstructions that describe the reaction stoichiometry, directionality, and gene to protein to reaction associations. A key bottleneck in the pace of reconstruction of new, high-quality metabolic models is the inability to directly make use of metabolite/reaction information from biological databases or other models due to incompatibilities in content representation (i.e., metabolites with multiple names across databases and models, stoichiometric errors such as elemental or charge imbalances, and incomplete atomistic detail (e.g., use of generic R-group or non-explicit specification of stereo-specificity. Description MetRxn is a knowledgebase that includes standardized metabolite and reaction descriptions by integrating information from BRENDA, KEGG, MetaCyc, Reactome.org and 44 metabolic models into a single unified data set. All metabolite entries have matched synonyms, resolved protonation states, and are linked to unique structures. All reaction entries are elementally and charge balanced. This is accomplished through the use of a workflow of lexicographic, phonetic, and structural comparison algorithms. MetRxn allows for the download of standardized versions of existing genome-scale metabolic models and the use of metabolic information for the rapid reconstruction of new ones. Conclusions The standardization in description allows for the direct comparison of the metabolite and reaction content between metabolic models and databases and the exhaustive prospecting of pathways for biotechnological production. This ever-growing dataset currently consists of over 76,000 metabolites participating in more than 72,000 reactions (including unresolved entries. MetRxn is hosted on a web-based platform that uses relational database models (MySQL.

  2. BlenX-based compositional modeling of complex reaction mechanisms

    CERN Document Server

    Zámborszky, Judit; 10.4204/EPTCS.19.6

    2010-01-01

    Molecular interactions are wired in a fascinating way resulting in complex behavior of biological systems. Theoretical modeling provides a useful framework for understanding the dynamics and the function of such networks. The complexity of the biological networks calls for conceptual tools that manage the combinatorial explosion of the set of possible interactions. A suitable conceptual tool to attack complexity is compositionality, already successfully used in the process algebra field to model computer systems. We rely on the BlenX programming language, originated by the beta-binders process calculus, to specify and simulate high-level descriptions of biological circuits. The Gillespie's stochastic framework of BlenX requires the decomposition of phenomenological functions into basic elementary reactions. Systematic unpacking of complex reaction mechanisms into BlenX templates is shown in this study. The estimation/derivation of missing parameters and the challenges emerging from compositional model buildin...

  3. Modelling biochemical reaction systems by stochastic differential equations with reflection.

    Science.gov (United States)

    Niu, Yuanling; Burrage, Kevin; Chen, Luonan

    2016-05-07

    In this paper, we gave a new framework for modelling and simulating biochemical reaction systems by stochastic differential equations with reflection not in a heuristic way but in a mathematical way. The model is computationally efficient compared with the discrete-state Markov chain approach, and it ensures that both analytic and numerical solutions remain in a biologically plausible region. Specifically, our model mathematically ensures that species numbers lie in the domain D, which is a physical constraint for biochemical reactions, in contrast to the previous models. The domain D is actually obtained according to the structure of the corresponding chemical Langevin equations, i.e., the boundary is inherent in the biochemical reaction system. A variant of projection method was employed to solve the reflected stochastic differential equation model, and it includes three simple steps, i.e., Euler-Maruyama method was applied to the equations first, and then check whether or not the point lies within the domain D, and if not perform an orthogonal projection. It is found that the projection onto the closure D¯ is the solution to a convex quadratic programming problem. Thus, existing methods for the convex quadratic programming problem can be employed for the orthogonal projection map. Numerical tests on several important problems in biological systems confirmed the efficiency and accuracy of this approach.

  4. EMPIRE: Nuclear Reaction Model Code System for Data Evaluation

    Science.gov (United States)

    Herman, M.; Capote, R.; Carlson, B. V.; Obložinský, P.; Sin, M.; Trkov, A.; Wienke, H.; Zerkin, V.

    2007-12-01

    EMPIRE is a modular system of nuclear reaction codes, comprising various nuclear models, and designed for calculations over a broad range of energies and incident particles. A projectile can be a neutron, proton, any ion (including heavy-ions) or a photon. The energy range extends from the beginning of the unresolved resonance region for neutron-induced reactions (∽ keV) and goes up to several hundred MeV for heavy-ion induced reactions. The code accounts for the major nuclear reaction mechanisms, including direct, pre-equilibrium and compound nucleus ones. Direct reactions are described by a generalized optical model (ECIS03) or by the simplified coupled-channels approach (CCFUS). The pre-equilibrium mechanism can be treated by a deformation dependent multi-step direct (ORION + TRISTAN) model, by a NVWY multi-step compound one or by either a pre-equilibrium exciton model with cluster emission (PCROSS) or by another with full angular momentum coupling (DEGAS). Finally, the compound nucleus decay is described by the full featured Hauser-Feshbach model with γ-cascade and width-fluctuations. Advanced treatment of the fission channel takes into account transmission through a multiple-humped fission barrier with absorption in the wells. The fission probability is derived in the WKB approximation within the optical model of fission. Several options for nuclear level densities include the EMPIRE-specific approach, which accounts for the effects of the dynamic deformation of a fast rotating nucleus, the classical Gilbert-Cameron approach and pre-calculated tables obtained with a microscopic model based on HFB single-particle level schemes with collective enhancement. A comprehensive library of input parameters covers nuclear masses, optical model parameters, ground state deformations, discrete levels and decay schemes, level densities, fission barriers, moments of inertia and γ-ray strength functions. The results can be converted into ENDF-6 formatted files using the

  5. A model study of sequential enzyme reactions and electrostatic channeling.

    Science.gov (United States)

    Eun, Changsun; Kekenes-Huskey, Peter M; Metzger, Vincent T; McCammon, J Andrew

    2014-03-14

    We study models of two sequential enzyme-catalyzed reactions as a basic functional building block for coupled biochemical networks. We investigate the influence of enzyme distributions and long-range molecular interactions on reaction kinetics, which have been exploited in biological systems to maximize metabolic efficiency and signaling effects. Specifically, we examine how the maximal rate of product generation in a series of sequential reactions is dependent on the enzyme distribution and the electrostatic composition of its participant enzymes and substrates. We find that close proximity between enzymes does not guarantee optimal reaction rates, as the benefit of decreasing enzyme separation is countered by the volume excluded by adjacent enzymes. We further quantify the extent to which the electrostatic potential increases the efficiency of transferring substrate between enzymes, which supports the existence of electrostatic channeling in nature. Here, a major finding is that the role of attractive electrostatic interactions in confining intermediate substrates in the vicinity of the enzymes can contribute more to net reactive throughput than the directional properties of the electrostatic fields. These findings shed light on the interplay of long-range interactions and enzyme distributions in coupled enzyme-catalyzed reactions, and their influence on signaling in biological systems.

  6. KINETIC MODELS STUDY OF HYDRODESULPHURIZATION VACUUM DISTILLATE REACTION

    Directory of Open Access Journals (Sweden)

    AbdulMunem A. Karim

    2013-05-01

    Full Text Available    This study deals with  kinetics of hydrodesulphurization (HDS reaction of vacuum gas oil (611-833 K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 - 650 K, medium vacuum gas oil (650-690 K, heavy vacuum gas oil (690-727 K and very heavy vacuum gas oil (727-833 K.   The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed reactor. The reaction temperature range (583-643 K,liquid hourly space velocity range (1.5-3.75 h-1 and hydrogen pressure was kept constant at 3.5 MPa with hydrogen to oil ratio about 250 lt/lt.           The conversion results for desulphurization reaction appeared to obey the second order reaction. According to this model, the rate constants for desulphurization reaction were determined. Finally, the apparent activation energy (Ea, enthalpy of activation ( H* and entropy ( S* were calculated based on the values of rate constant (k2 and were equal 80.3792 KJ/mole, 75.2974 KJ/mole and 197.493 J/mole, respectively.

  7. Modelling of structural effects on chemical reactions in turbulent flows

    Energy Technology Data Exchange (ETDEWEB)

    Gammelsaeter, H.R.

    1997-12-31

    Turbulence-chemistry interactions are analysed using algebraic moment closure for the chemical reaction term. The coupling between turbulence and chemical length and time scales generate a complex interaction process. This interaction process is called structural effects in this work. The structural effects are shown to take place on all scales between the largest scale of turbulence and the scales of the molecular motions. The set of equations describing turbulent correlations involved in turbulent reacting flows are derived. Interactions are shown schematically using interaction charts. Algebraic equations for the turbulent correlations in the reaction rate are given using the interaction charts to include the most significant couplings. In the frame of fundamental combustion physics, the structural effects appearing on the small scales of turbulence are proposed modelled using a discrete spectrum of turbulent scales. The well-known problem of averaging the Arrhenius law, the specific reaction rate, is proposed solved using a presumed single variable probability density function and a sub scale model for the reaction volume. Although some uncertainties are expected, the principles are addressed. Fast chemistry modelling is shown to be consistent in the frame of algebraic moment closure when the turbulence-chemistry interaction is accounted for in the turbulent diffusion. The modelling proposed in this thesis is compared with experimental data for an laboratory methane flame and advanced probability density function modelling. The results show promising features. Finally it is shown a comparison with full scale measurements for an industrial burner. All features of the burner are captured with the model. 41 refs., 33 figs.

  8. Thermochemical model for shock-induced chemical reactions in porous thermite: The heat detonation model

    Energy Technology Data Exchange (ETDEWEB)

    Boslough, M.B.

    1989-01-01

    A thermochemical model has been developed that treats a shock-induced solid state chemical reaction as a special type of detonation, called a ''heat detonation'' to distinguish it from an ordinary explosive detonation and describe the final form that the chemical energy takes. According to shock temperature measurements, chemical energy can be released from porous reactive solids on a time scale shorter than shock-transit times in laboratory samples. By comparing the experimental shock temperature for porous thermite to that calculated by the model, the amount of thermite reacted when shocked to about 4 GPa was estimated to be between 60 and 70%. Calculated shock temperatures are extremely strong functions of the extent of reaction, but are relatively insensitive to the initial porosity and amount of volatile impurities. Thus, shock temperature measurements are the most useful for real-time studies of shock-induced exothermic chemical reactions in solids. 11 refs., 5 figs., 1 tab.

  9. Optimization Models for Reaction Networks: Information Divergence, Quadratic Programming and Kirchhoff’s Laws

    Directory of Open Access Journals (Sweden)

    Julio Michael Stern

    2014-03-01

    Full Text Available This article presents a simple derivation of optimization models for reaction networks leading to a generalized form of the mass-action law, and compares the formal structure of Minimum Information Divergence, Quadratic Programming and Kirchhoff type network models. These optimization models are used in related articles to develop and illustrate the operation of ontology alignment algorithms and to discuss closely connected issues concerning the epistemological and statistical significance of sharp or precise hypotheses in empirical science.

  10. Spallation reactions. A successful interplay between modeling and applications

    CERN Document Server

    David, J -C

    2015-01-01

    The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improv...

  11. Towards many-body based nuclear reaction modelling

    Science.gov (United States)

    Hilaire, Stéphane; Goriely, Stéphane

    2016-06-01

    The increasing need for cross sections far from the valley of stability poses a challenge for nuclear reaction models. So far, predictions of cross sections have relied on more or less phenomenological approaches, depending on parameters adjusted to available experimental data or deduced from systematic expressions. While such predictions are expected to be reliable for nuclei not too far from the experimentally known regions, it is clearly preferable to use more fundamental approaches, based on sound physical principles, when dealing with very exotic nuclei. Thanks to the high computer power available today, all the ingredients required to model a nuclear reaction can now be (and have been) microscopically (or semi-microscopically) determined starting from the information provided by a nucleon-nucleon effective interaction. This concerns nuclear masses, optical model potential, nuclear level densities, photon strength functions, as well as fission barriers. All these nuclear model ingredients, traditionally given by phenomenological expressions, now have a microscopic counterpart implemented in the TALYS nuclear reaction code. We are thus now able to perform fully microscopic cross section calculations. The quality of these ingredients and the impact of using them instead of the usually adopted phenomenological parameters will be discussed. Perspectives for the coming years will be drawn on the improvements one can expect.

  12. Phenotyping Adverse Drug Reactions: Statin-Related Myotoxicity.

    Science.gov (United States)

    Wiley, Laura K; Moretz, Jeremy D; Denny, Joshua C; Peterson, Josh F; Bush, William S

    2015-01-01

    It is unclear the extent to which best practices for phenotyping disease states from electronic medical records (EMRs) translate to phenotyping adverse drug events. Here we use statin-induced myotoxicity as a case study to identify best practices in this area. We compared multiple phenotyping algorithms using administrative codes, laboratory measurements, and full-text keyword matching to identify statin-related myopathy from EMRs. Manual review of 300 deidentified EMRs with exposure to at least one statin, created a gold standard set of 124 cases and 176 controls. We tested algorithms using ICD-9 billing codes, laboratory measurements of creatine kinase (CK) and keyword searches of clinical notes and allergy lists. The combined keyword algorithms produced were the most accurate (PPV=86%, NPV=91%). Unlike in most disease phenotyping algorithms, addition of ICD9 codes or laboratory data did not appreciably increase algorithm accuracy. We conclude that phenotype algorithms for adverse drug events should consider text based approaches.

  13. Mathematical modeling of precipitation and dissolution reactions in microbiological systems.

    Science.gov (United States)

    Rittmann, Bruce E; Banaszak, James E; VanBriesen, Jeanne M; Reed, Donald T

    2002-01-01

    We expand the biogeochemical model CCBATCH to include a precipitation/dissolution sub-model that contains kinetic and equilibrium options. This advancement extends CCBATCH's usefulness to situations in which microbial reactions cause or are affected by formation or dissolution of a solid phase. The kinetic option employs a rate expression that explicitly includes the intrinsic kinetics for reaction or mass-transport control, the difference from thermodynamic equilibrium, and the aqueous concentration of the rate-limiting metal or ligand. The equilibrium feature can be used alone, and it also serves as check that the kinetic rate never is too fast and "overshoots" equilibrium. The features of the expanded CCBATCH are illustrated by an example in which the precipitation of Fe(OH)3(s) allows the biodegradation of citric acid, even though complexes are strong and not bioavailable. Precipitation releases citrate ligand, and biodegradation of the citrate increases the pH.

  14. A unifying kinetic framework for modeling oxidoreductase-catalyzed reactions

    OpenAIRE

    Chang, Ivan; Baldi, Pierre

    2013-01-01

    Motivation: Oxidoreductases are a fundamental class of enzymes responsible for the catalysis of oxidation–reduction reactions, crucial in most bioenergetic metabolic pathways. From their common root in the ancient prebiotic environment, oxidoreductases have evolved into diverse and elaborate protein structures with specific kinetic properties and mechanisms adapted to their individual functional roles and environmental conditions. While accurate kinetic modeling of oxidoreductases is thus imp...

  15. Reaction Networks as a Language for Systemic Modeling: On the Study of Structural Changes

    Directory of Open Access Journals (Sweden)

    Tomas Veloz

    2017-03-01

    Full Text Available Reaction Networks have been recently proposed as a framework for systems modeling due to its capability to describe many entities interacting in contextual ways and leading to the emergence of meta-structures. Since systems can be subjected to structural changes that not only alter their inner functioning, but also their underlying ontological features, a crucial issue is how to address these structural changes within a formal representational framework. When modeling systems using reaction networks, we find that three fundamentally different types of structural change are possible. The first corresponds to the usual notion of perturbation in dynamical systems, i.e., change in system’s state. The second corresponds to behavioral changes, i.e., changes not in the state of the system but on the properties of its behavioral rules. The third corresponds to radical structural changes, i.e., changes in the state-set structure and/or in reaction-set structure. In this article, we describe in detail the three types of structural changes that can occur in a reaction network, and how these changes relate to changes in the systems observable within this reaction network. In particular, we develop a decomposition theorem to partition a reaction network as a collection of dynamically independent modules, and show how such decomposition allows for precisely identifying the parts of the reaction network that are affected by a structural change.

  16. Kinetic modelling of GlmU reactions - prioritization of reaction for therapeutic application.

    Directory of Open Access Journals (Sweden)

    Vivek K Singh

    Full Text Available Mycobacterium tuberculosis(Mtu, a successful pathogen, has developed resistance against the existing anti-tubercular drugs necessitating discovery of drugs with novel action. Enzymes involved in peptidoglycan biosynthesis are attractive targets for antibacterial drug discovery. The bifunctional enzyme mycobacterial GlmU (Glucosamine 1-phosphate N-acetyltransferase/ N-acetylglucosamine-1-phosphate uridyltransferase has been a target enzyme for drug discovery. Its C- and N- terminal domains catalyze acetyltransferase (rxn-1 and uridyltransferase (rxn-2 activities respectively and the final product is involved in peptidoglycan synthesis. However, the bifunctional nature of GlmU poses difficulty in deciding which function to be intervened for therapeutic advantage. Genetic analysis showed this as an essential gene but it is still unclear whether any one or both of the activities are critical for cell survival. Often enzymatic activity with suitable high-throughput assay is chosen for random screening, which may not be the appropriate biological function inhibited for maximal effect. Prediction of rate-limiting function by dynamic network analysis of reactions could be an option to identify the appropriate function. With a view to provide insights into biochemical assays with appropriate activity for inhibitor screening, kinetic modelling studies on GlmU were undertaken. Kinetic model of Mtu GlmU-catalyzed reactions was built based on the available kinetic data on Mtu and deduction from Escherichia coli data. Several model variants were constructed including coupled/decoupled, varying metabolite concentrations and presence/absence of product inhibitions. This study demonstrates that in coupled model at low metabolite concentrations, inhibition of either of the GlmU reactions cause significant decrement in the overall GlmU rate. However at higher metabolite concentrations, rxn-2 showed higher decrement. Moreover, with available intracellular

  17. Mathematical Model of Synthesis Catalyst with Local Reaction Centers

    Directory of Open Access Journals (Sweden)

    I. V. Derevich

    2017-01-01

    Full Text Available The article considers a catalyst granule with a porous ceramic passive substrate and point active centers on which an exothermic synthesis reaction occurs. A rate of the chemical reaction depends on the temperature according to the Arrhenius law. Heat is removed from the pellet surface in products of synthesis due to heat transfer. In our work we first proposed a model for calculating the steady-state temperature of a catalyst pellet with local reaction centers. Calculation of active centers temperature is based on the idea of self-consistent field (mean-field theory. At first, it is considered that powers of the reaction heat release at the centers are known. On the basis of the found analytical solution, which describes temperature distribution inside the granule, the average temperature of the reaction centers is calculated, which then is inserted in the formula for heat release. The resulting system of transcendental algebraic equations is transformed into a system of ordinary differential equations of relaxation type and solved numerically to achieve a steady-state value. As a practical application, the article considers a Fischer-Tropsch synthesis catalyst granule with active cobalt metallic micro-particles. Cobalt micro-particles are the centers of the exothermic reaction of hydrocarbons macromolecular synthesis. Synthesis occurs as a result of absorption of the components of the synthesis gas on metallic cobalt. The temperature distribution inside the granule for a single local center and reaction centers located on the same granule diameter is found. It was found that there is a critical temperature of reactor exceeding of which leads to significant local overheating of the centers - thermal explosion. The temperature distribution with the local reaction centers is qualitatively different from the granule temperature, calculated in the homogeneous approximation. It is shown that, in contrast to the homogeneous approximation, the

  18. Turing instability in reaction-diffusion models on complex networks

    Science.gov (United States)

    Ide, Yusuke; Izuhara, Hirofumi; Machida, Takuya

    2016-09-01

    In this paper, the Turing instability in reaction-diffusion models defined on complex networks is studied. Here, we focus on three types of models which generate complex networks, i.e. the Erdős-Rényi, the Watts-Strogatz, and the threshold network models. From analysis of the Laplacian matrices of graphs generated by these models, we numerically reveal that stable and unstable regions of a homogeneous steady state on the parameter space of two diffusion coefficients completely differ, depending on the network architecture. In addition, we theoretically discuss the stable and unstable regions in the cases of regular enhanced ring lattices which include regular circles, and networks generated by the threshold network model when the number of vertices is large enough.

  19. Bayesian inference of chemical kinetic models from proposed reactions

    KAUST Repository

    Galagali, Nikhil

    2015-02-01

    © 2014 Elsevier Ltd. Bayesian inference provides a natural framework for combining experimental data with prior knowledge to develop chemical kinetic models and quantify the associated uncertainties, not only in parameter values but also in model structure. Most existing applications of Bayesian model selection methods to chemical kinetics have been limited to comparisons among a small set of models, however. The significant computational cost of evaluating posterior model probabilities renders traditional Bayesian methods infeasible when the model space becomes large. We present a new framework for tractable Bayesian model inference and uncertainty quantification using a large number of systematically generated model hypotheses. The approach involves imposing point-mass mixture priors over rate constants and exploring the resulting posterior distribution using an adaptive Markov chain Monte Carlo method. The posterior samples are used to identify plausible models, to quantify rate constant uncertainties, and to extract key diagnostic information about model structure-such as the reactions and operating pathways most strongly supported by the data. We provide numerical demonstrations of the proposed framework by inferring kinetic models for catalytic steam and dry reforming of methane using available experimental data.

  20. A New Geochemical Reaction Model for Groundwater Systems

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Through a survey of the literature on geology, hydrogeology and hydrogeochemistry, this paper presents a hydrogeochemical model for the groundwater system in a dross-dumping area of the Shandong Aluminium Plant. It is considered that the groundwater-bearing medium is a mineral aggregate and that the interactions between groundwater and the groundwater-bearing medium can be described as a series of geochemical reactions. On that basis, the principle of minimum energy and the equations of mass balance, electron balance and electric neutrality are applied to construct a linear programming mathematical model for the calculation of mass transfer between water and rock with the simplex method.

  1. Forced thermal cycling of catalytic reactions: experiments and modelling

    DEFF Research Database (Denmark)

    Jensen, Søren; Olsen, Jakob Lind; Thorsteinsson, Sune;

    2007-01-01

    Recent studies of catalytic reactions subjected to fast forced temperature oscillations have revealed a rate enhancement increasing with temperature oscillation frequency. We present detailed studies of the rate enhancement up to frequencies of 2.5 Hz. A maximum in the rate enhancement is observed...... at about 1 Hz. A model for the rate enhancement that includes the surface kinetics and the dynamic partial pressure variations in the reactor is introduced. The model predicts a levelling off of the rate enhancement with frequency at about 1 Hz. The experimentally observed decrease above 1 Hz is explained...... by dynamic thermal limitations of the reactor. (c) 2007 Elsevier B.V. All rights reserved....

  2. Universal model for exoergic bimolecular reactions and inelastic processes

    CERN Document Server

    Gao, Bo

    2010-01-01

    From a rigorous multichannel quantum-defect formulation of bimolecular processes, we derive a fully quantal and analytic model for the total rate of exoergic bimolecular reactions and/or inelastic processes that is applicable over a wide range of temperatures including the ultracold regime. The theory establishes a connection between the ultracold chemistry and the regular chemistry by showing that the same theory that gives the quantum threshold behavior agrees with the classical Gorin model at higher temperatures. In between, it predicts that the rates for identical bosonic molecules and distinguishable molecules would first decrease with temperature outside of the Wigner threshold region, before rising after a minimum is reached.

  3. Fundamental Heterogeneous Reaction Chemistry Related to Secondary Organic Aerosols (SOA) in the Atmosphere

    Science.gov (United States)

    Akimoto, H.

    2016-11-01

    Typical reaction pathways of formation of dicarboxylic acids, larger multifunctional compounds, oligomers, and organosulfur and organonitrogen compounds in secondary organic aerosols (SOA), revealed by laboratory experimental studies are reviewed with a short introduction to field observations. In most of the reactions forming these compounds, glyoxal, methyl glyoxal and related difunctional carbonyl compounds play an important role as precursors, and so their formation pathways in the gas phase are discussed first. A substantial discussion is then presented for the OH-initiated aqueous phase radical oxidation reactions of glyoxal and other carbonyls which form dicarboxylic acids, larger multifunctional compounds and oligomers, and aqueous-phase non-radical reactions which form oligomers, organosulfates and organonitrogen compounds. Finally, the heterogeneous oxidation reaction of gaseous O3, OH and NO3 with liquid and solid organic aerosols at the air-particle interface is discussed relating to the aging of SOA in the atmosphere.

  4. Reactions of Lignin Model Compounds in Ionic Liquids

    Energy Technology Data Exchange (ETDEWEB)

    Holladay, John E.; Binder, Joseph B.; Gray, Michel J.; White, James F.; Zhang, Z. Conrad

    2009-09-15

    Lignin, a readily available form of biomass, awaits novel chemistry for converting it to valuable aromatic chemicals. Recent work has demonstrated that ionic liquids are excellent solvents for processing woody biomass and lignin. Seeking to exploit ionic liquids as media for depolymerization of lignin, we investigated reactions of lignin model compounds in these solvents. Using Brønsted acid catalysts in 1-ethyl-3-methylimidazolium triflate at moderate temperatures, we obtained up to 11.6% yield of the dealkylation product guaiacol from the model compound eugenol and cleaved phenethyl phenyl ether, a model for lignin ethers. Despite these successes, acid catalysis failed in dealkylation of the unsaturated model compound 4-ethylguaiacol and did not produce monomeric products from organosolv lignin, demonstrating that further work is required to understand the complex chemistry of lignin depolymerization.

  5. A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan [ORNL; Yeh, Gour-Tsyh [University of Central Florida, Orlando; Parker, Jack C [ORNL; Brooks, Scott C [ORNL; Pace, Molly [ORNL; Kim, Young Jin [ORNL; Jardine, Philip M [ORNL; Watson, David B [ORNL

    2007-01-01

    This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

  6. A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

    Science.gov (United States)

    Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Brooks, Scott C.; Pace, Molly N.; Kim, Young-Jin; Jardine, Philip M.; Watson, David B.

    2007-06-01

    This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M- NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

  7. Mechanical reaction-diffusion model for bacterial population dynamics

    CERN Document Server

    Ngamsaad, Waipot

    2015-01-01

    The effect of mechanical interaction between cells on the spreading of bacterial population was investigated in one-dimensional space. A nonlinear reaction-diffusion equation has been formulated as a model for this dynamics. In this model, the bacterial cells are treated as the rod-like particles that interact, when contacting each other, through the hard-core repulsion. The repulsion introduces the exclusion process that causes the fast diffusion in bacterial population at high density. The propagation of the bacterial density as the traveling wave front in long time behavior has been analyzed. The analytical result reveals that the front speed is enhanced by the exclusion process---and its value depends on the packing fraction of cell. The numerical solutions of the model have been solved to confirm this prediction.

  8. Reaction times to weak test lights. [psychophysics biological model

    Science.gov (United States)

    Wandell, B. A.; Ahumada, P.; Welsh, D.

    1984-01-01

    Maloney and Wandell (1984) describe a model of the response of a single visual channel to weak test lights. The initial channel response is a linearly filtered version of the stimulus. The filter output is randomly sampled over time. Each time a sample occurs there is some probability increasing with the magnitude of the sampled response - that a discrete detection event is generated. Maloney and Wandell derive the statistics of the detection events. In this paper a test is conducted of the hypothesis that the reaction time responses to the presence of a weak test light are initiated at the first detection event. This makes it possible to extend the application of the model to lights that are slightly above threshold, but still within the linear operating range of the visual system. A parameter-free prediction of the model proposed by Maloney and Wandell for lights detected by this statistic is tested. The data are in agreement with the prediction.

  9. Modeling the Reactions of Energetic Materials in the Condensed Phase

    Energy Technology Data Exchange (ETDEWEB)

    Fried, L E; Manaa, M R; Lewis, J P

    2003-12-03

    High explosive (HE) materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. Although the history of HE materials is long, condensed-phase properties are poorly understood. Understanding the condensed-phase properties of HE materials is important for determining stability and performance. Information regarding HE material properties (for example, the physical, chemical, and mechanical behaviors of the constituents in plastic-bonded explosive, or PBX, formulations) is necessary in efficiently building the next generation of explosives as the quest for more powerful energetic materials (in terms of energy per volume) moves forward. In addition, understanding the reaction mechanisms has important ramifications in disposing of such materials safely and cheaply, as there exist vast stockpiles of HE materials with corresponding contamination of earth and groundwater at these sites, as well as a military testing sites The ability to model chemical reaction processes in condensed phase energetic materials is rapidly progressing. Chemical equilibrium modeling is a mature technique with some limitations. Progress in this area continues, but is hampered by a lack of knowledge of condensed phase reaction mechanisms and rates. Atomistic modeling is much more computationally intensive, and is currently limited to very short time scales. Nonetheless, this methodology promises to yield the first reliable insights into the condensed phase processes responsible for high explosive detonation. Further work is necessary to extend the timescales involved in atomistic simulations. Recent work in implementing thermostat methods appropriate to shocks may promise to overcome some of these difficulties. Most current work on energetic material reactivity assumes that electronically adiabatic processes dominate. The role of excited states is becoming clearer, however. These states are not accessible in perfect

  10. Systematic development of reduced reaction mechanisms for dynamic modeling

    Science.gov (United States)

    Frenklach, M.; Kailasanath, K.; Oran, E. S.

    1986-01-01

    A method for systematically developing a reduced chemical reaction mechanism for dynamic modeling of chemically reactive flows is presented. The method is based on the postulate that if a reduced reaction mechanism faithfully describes the time evolution of both thermal and chain reaction processes characteristic of a more complete mechanism, then the reduced mechanism will describe the chemical processes in a chemically reacting flow with approximately the same degree of accuracy. Here this postulate is tested by producing a series of mechanisms of reduced accuracy, which are derived from a full detailed mechanism for methane-oxygen combustion. These mechanisms were then tested in a series of reactive flow calculations in which a large-amplitude sinusoidal perturbation is applied to a system that is initially quiescent and whose temperature is high enough to start ignition processes. Comparison of the results for systems with and without convective flow show that this approach produces reduced mechanisms that are useful for calculations of explosions and detonations. Extensions and applicability to flames are discussed.

  11. BlenX-based compositional modeling of complex reaction mechanisms

    Directory of Open Access Journals (Sweden)

    Judit Zámborszky

    2010-02-01

    Full Text Available Molecular interactions are wired in a fascinating way resulting in complex behavior of biological systems. Theoretical modeling provides a useful framework for understanding the dynamics and the function of such networks. The complexity of the biological networks calls for conceptual tools that manage the combinatorial explosion of the set of possible interactions. A suitable conceptual tool to attack complexity is compositionality, already successfully used in the process algebra field to model computer systems. We rely on the BlenX programming language, originated by the beta-binders process calculus, to specify and simulate high-level descriptions of biological circuits. The Gillespie's stochastic framework of BlenX requires the decomposition of phenomenological functions into basic elementary reactions. Systematic unpacking of complex reaction mechanisms into BlenX templates is shown in this study. The estimation/derivation of missing parameters and the challenges emerging from compositional model building in stochastic process algebras are discussed. A biological example on circadian clock is presented as a case study of BlenX compositionality.

  12. Reaction-diffusion-branching models of stock price fluctuations

    Science.gov (United States)

    Tang, Lei-Han; Tian, Guang-Shan

    Several models of stock trading (Bak et al., Physica A 246 (1997) 430.) are analyzed in analogy with one-dimensional, two-species reaction-diffusion-branching processes. Using heuristic and scaling arguments, we show that the short-time market price variation is subdiffusive with a Hurst exponent H=1/4. Biased diffusion towards the market price and blind-eyed copying lead to crossovers to the empirically observed random-walk behavior ( H=1/2) at long times. The calculated crossover forms and diffusion constants are shown to agree well with simulation data.

  13. Parametric pattern selection in a reaction-diffusion model.

    Directory of Open Access Journals (Sweden)

    Michael Stich

    Full Text Available We compare spot patterns generated by Turing mechanisms with those generated by replication cascades, in a model one-dimensional reaction-diffusion system. We determine the stability region of spot solutions in parameter space as a function of a natural control parameter (feed-rate where degenerate patterns with different numbers of spots coexist for a fixed feed-rate. While it is possible to generate identical patterns via both mechanisms, we show that replication cascades lead to a wider choice of pattern profiles that can be selected through a tuning of the feed-rate, exploiting hysteresis and directionality effects of the different pattern pathways.

  14. Performance of Frozen Density Embedding for Modeling Hole Transfer Reactions

    CERN Document Server

    Ramos, Pablo; Pavanello, Michele

    2015-01-01

    We have carried out a thorough benchmark of the FDE-ET method for calculating hole transfer couplings. We have considered 10 exchange-correlation functionals, 3 non-additive kinetic energy functionals and 3 basis sets. Overall, we conclude that with a 7% mean relative unsigned error, the PBE functional coupled with the PW91k non-additive Kinetic energy functional and a TZP basis set constitutes the most stable, and accurate level of theory for hole-transfer coupling calculations. The FDE-ET method is found to be an excellent tool for computing diabatic couplings for hole transfer reactions.

  15. Stepwise kinetic equilibrium models of quantitative polymerase chain reaction

    Directory of Open Access Journals (Sweden)

    Cobbs Gary

    2012-08-01

    Full Text Available Abstract Background Numerous models for use in interpreting quantitative PCR (qPCR data are present in recent literature. The most commonly used models assume the amplification in qPCR is exponential and fit an exponential model with a constant rate of increase to a select part of the curve. Kinetic theory may be used to model the annealing phase and does not assume constant efficiency of amplification. Mechanistic models describing the annealing phase with kinetic theory offer the most potential for accurate interpretation of qPCR data. Even so, they have not been thoroughly investigated and are rarely used for interpretation of qPCR data. New results for kinetic modeling of qPCR are presented. Results Two models are presented in which the efficiency of amplification is based on equilibrium solutions for the annealing phase of the qPCR process. Model 1 assumes annealing of complementary targets strands and annealing of target and primers are both reversible reactions and reach a dynamic equilibrium. Model 2 assumes all annealing reactions are nonreversible and equilibrium is static. Both models include the effect of primer concentration during the annealing phase. Analytic formulae are given for the equilibrium values of all single and double stranded molecules at the end of the annealing step. The equilibrium values are then used in a stepwise method to describe the whole qPCR process. Rate constants of kinetic models are the same for solutions that are identical except for possibly having different initial target concentrations. Analysis of qPCR curves from such solutions are thus analyzed by simultaneous non-linear curve fitting with the same rate constant values applying to all curves and each curve having a unique value for initial target concentration. The models were fit to two data sets for which the true initial target concentrations are known. Both models give better fit to observed qPCR data than other kinetic models present in the

  16. Instability Criterion of One-Dimensional Detonation Wave with Three-Step Chain Branching Reaction Model

    Institute of Scientific and Technical Information of China (English)

    TENG Hong-Hui; JIANG Zong-Lin

    2011-01-01

    @@ One-dimensional detonation waves are simulated with the three-step chain branching reaction model, and the instability criterion is studied.The ratio of the induction zone length and the reaction zone length may be used to decide the instability, and the detonation becomes unstable with the high ratio.However, the ratio is not invariable with different heat release values.The critical ratio, corresponding to the transition from the stable detonation to the unstable detonation, has a negative correlation with the heat release.An empirical relation of the Chapman-Jouguet Mach number and the length ratio is proposed as the instability criterion.

  17. Chemical modelling of Alkali Silica reaction: Influence of the reactive aggregate size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Poyet, S. [CEA Saclay, DEN/DANS/DPC/SCCME/LECBA, F-91191 Gif Sur Yvette, (France); Sellier, A. [UPS, LMDC, INSA Toulouse, F-33077 Bordeaux 4, (France); Capra, B. [Oxand SA, F-77210 Avon (France); Foray, G. [Univ Lyon 1, L2MS, PETRA GC, F-69622 Villeurbanne (France); Torrenti, J.M. [IRSN, F-92262 Fontenay Aux Roses (France); Cognon, H. [EdF/DER Les Renardieres, F-77818 Moret Sur Loing (France); Bourdarot, E. [CIH Savoie Technolac, F-73373 Le Bourget du Lac (France)

    2007-07-01

    This article presents a new model which aims at predicting the expansion induced by Alkali Silica Reaction (ASR) and describing the chemical evolution of affected concretes. It is based on the description of the transport and reaction of alkalis and calcium ions within a Relative Elementary Volume (REV). It takes into account the influence of the reactive aggregate size grading on ASR, i.e. the effect of the simultaneous presence of different sized reactive aggregates within concrete. The constitutive equations are detailed and fitted using experimental results. Results from numerical simulations are presented and compared with experiments. (authors)

  18. The $^{136}$Xe + $^{208}$Pb reaction: A test of models of multi-nucleon transfer reactions

    CERN Document Server

    Barrett, J S; Loveland, W; Zhu, S; Ayangeakaa, A D; Carpenter, M P; Greene, J P; Janssens, R V F; Lauritsen, T; McCutchan, E A; Sonzogni, A A; Chiara, C J; Harker, J L; Walters, W B

    2015-01-01

    The yields of over 200 projectile-like fragments (PLFs) and target-like fragments (TLFs) from the interaction of (E$_{c.m.}$=450 MeV) $^{136}$Xe with a thick target of $^{208}$Pb were measured using Gammasphere and off-line $\\gamma$-ray spectroscopy, giving a comprehensive picture of the production cross sections in this reaction.The measured yields were compared to predictions of the GRAZING model and the predictions of Zagrebaev and Greiner using a quantitative metric, the theory evaluation factor, {\\bf tef}. The GRAZING model predictions are adequate for describing the yields of nuclei near the target or projectile but grossly underestimate the yields of all other products. The predictions of Zagrebaev and Greiner correctly describe the magnitude and maxima of the observed TLF transfer cross sections for a wide range of transfers ($\\Delta$Z = -8 to $\\Delta$Z = +2). However for $\\Delta$Z =+4, the observed position of the maximum in the distribution is four neutrons richer than the predicted maximum. The pre...

  19. Geochemical controls on shale groundwaters: Results of reaction path modeling

    Energy Technology Data Exchange (ETDEWEB)

    Von Damm, K.L.; VandenBrook, A.J.

    1989-03-01

    The EQ3NR/EQ6 geochemical modeling code was used to simulate the reaction of several shale mineralogies with different groundwater compositions in order to elucidate changes that may occur in both the groundwater compositions, and rock mineralogies and compositions under conditions which may be encountered in a high-level radioactive waste repository. Shales with primarily illitic or smectitic compositions were the focus of this study. The reactions were run at the ambient temperatures of the groundwaters and to temperatures as high as 250/degree/C, the approximate temperature maximum expected in a repository. All modeling assumed that equilibrium was achieved and treated the rock and water assemblage as a closed system. Graphite was used as a proxy mineral for organic matter in the shales. The results show that the presence of even a very small amount of reducing mineral has a large influence on the redox state of the groundwaters, and that either pyrite or graphite provides essentially the same results, with slight differences in dissolved C, Fe and S concentrations. The thermodynamic data base is inadequate at the present time to fully evaluate the speciation of dissolved carbon, due to the paucity of thermodynamic data for organic compounds. In the illitic cases the groundwaters resulting from interaction at elevated temperatures are acid, while the smectitic cases remain alkaline, although the final equilibrium mineral assemblages are quite similar. 10 refs., 8 figs., 15 tabs.

  20. Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kandel, Kapil [Ames Laboratory; Althaus, Stacey M [Ames Laboratory; Peeraphatdit, Chorthip [Ames Laboratory; Kobayashi, Takeshi [Ames Laboratory; Trewyn, Brian G [Ames Laboratory; Pruski, Marek [Ames Laboratory; Slowing, Igor I [Ames Laboratory

    2013-01-11

    The relative rates of the aldol reaction catalyzed by supported primary and secondary amines can be inverted by 2 orders of magnitude, depending on the use of hexane or water as a solvent. Our analyses suggest that this dramatic shift in the catalytic behavior of the supported amines does not involve differences in reaction mechanism, but is caused by activation of imine to enamine equilibria and stabilization of iminium species. The effects of solvent polarity and acidity were found to be important to the performance of the catalytic reaction. This study highlights the critical role of solvent in multicomponent heterogeneous catalytic processes.

  1. A robust methodology for kinetic model parameter estimation for biocatalytic reactions

    DEFF Research Database (Denmark)

    Al-Haque, Naweed; Andrade Santacoloma, Paloma de Gracia; Lima Afonso Neto, Watson;

    2012-01-01

    Effective estimation of parameters in biocatalytic reaction kinetic expressions are very important when building process models to enable evaluation of process technology options and alternative biocatalysts. The kinetic models used to describe enzyme-catalyzed reactions generally include several...

  2. Modelling of Serpentine Continuous Flow Polymerase Chain Reaction Microfluidics

    Directory of Open Access Journals (Sweden)

    Abubakar Mohammed

    2012-03-01

    Full Text Available The continuous flow Polymerase Chain Reaction (PCR microfluidics DNA amplification device is a recent discovery aimed at eliminating the cyclic hold experienced while using the alternative stationary device.The Application of Computational Fluid Dynamics is increasingly growing and can help achieve optimal designs before actual fabrication. This paper presents a CFD modelling of a continuous flow serpentine PCR device with narrow and wider channels. There are two temperature regions at 950C and 600C for denaturation and annealing respectively. Extension is achieved along the middle of the channel at 720C owing to temperature gradient. The model require a pressure of 42.6KPa for a 30 cycle amplification.

  3. A reaction-diffusion model of human brain development.

    Directory of Open Access Journals (Sweden)

    Julien Lefèvre

    2010-04-01

    Full Text Available Cortical folding exhibits both reproducibility and variability in the geometry and topology of its patterns. These two properties are obviously the result of the brain development that goes through local cellular and molecular interactions which have important consequences on the global shape of the cortex. Hypotheses to explain the convoluted aspect of the brain are still intensively debated and do not focus necessarily on the variability of folds. Here we propose a phenomenological model based on reaction-diffusion mechanisms involving Turing morphogens that are responsible for the differential growth of two types of areas, sulci (bottom of folds and gyri (top of folds. We use a finite element approach of our model that is able to compute the evolution of morphogens on any kind of surface and to deform it through an iterative process. Our model mimics the progressive folding of the cortical surface along foetal development. Moreover it reveals patterns of reproducibility when we look at several realizations of the model from a noisy initial condition. However this reproducibility must be tempered by the fact that a same fold engendered by the model can have different topological properties, in one or several parts. These two results on the reproducibility and variability of the model echo the sulcal roots theory that postulates the existence of anatomical entities around which the folding organizes itself. These sulcal roots would correspond to initial conditions in our model. Last but not least, the parameters of our model are able to produce different kinds of patterns that can be linked to developmental pathologies such as polymicrogyria and lissencephaly. The main significance of our model is that it proposes a first approach to the issue of reproducibility and variability of the cortical folding.

  4. Mediated priming in the lexical decision task : Evidence from event-related potentials and reaction time

    NARCIS (Netherlands)

    Chwilla, DJ; Kolk, HHJ; Mulder, G

    Mediated priming (e.g., from LION to STRIPES vis TIGER) is predicted by spreading activation models hut only by some integration model. The goal of the present research was to localize mediated priming by assessing two-step priming effects on N400 and reaction times (RT). We propose that the N400

  5. Mediated priming in the lexical decision task : Evidence from event-related potentials and reaction time

    NARCIS (Netherlands)

    Chwilla, DJ; Kolk, HHJ; Mulder, G

    2000-01-01

    Mediated priming (e.g., from LION to STRIPES vis TIGER) is predicted by spreading activation models hut only by some integration model. The goal of the present research was to localize mediated priming by assessing two-step priming effects on N400 and reaction times (RT). We propose that the N400 pr

  6. Me, Myself, Fairness, and I: On the Self-Related Aspects of Fairness Reactions

    NARCIS (Netherlands)

    Loseman, A.

    2011-01-01

    The current dissertation focuses on the psychology of justice as a self-related process. Six experiments within three justice domains are reported in which specific self-related aspects and their influence on fairness reactions are investigated. The construction of one’s self-image (i.e., the

  7. Latino/Hispanic Alzheimer’s caregivers experiencing dementia-related dressing issues: corroboration of the Preservation of Self model and reactions to a “smart dresser” computer-based dressing aid

    OpenAIRE

    Mahoney, Diane Feeney; Coon, David W; Lozano, Cecil

    2016-01-01

    Objective To gain an understanding of Latino/Hispanic caregivers’ dementia-related dressing issues, their impressions of using a “smart” context-aware dresser to coach dressing, and recommendations to improve its acceptability. Method The same Latina moderator conducted all the caregiver focus groups. She followed a semi-structured interview guide that was previously used with White and African American family caregivers who experienced Alzheimer’s disease related dressing challenges. From th...

  8. Emotional reactions to deviance in groups: the relation between number of angry reactions, felt rejection, and conformity

    Science.gov (United States)

    Heerdink, Marc W.; van Kleef, Gerben A.; Homan, Astrid C.; Fischer, Agneta H.

    2015-01-01

    How many members of a group need to express their anger in order to influence a deviant group member’s behavior? In two studies, we examine whether an increase in number of angry group members affects the extent to which a deviant individual feels rejected, and we investigate downstream effects on conformity. We show that each additional angry reaction linearly increases the extent to which a deviant individual feels rejected, and that this relation is independent of the total number of majority members (Study 1). This felt rejection is then shown to lead to anti-conformity unless two conditions are met: (1) the deviant is motivated to seek reacceptance in the group, and (2) conformity is instrumental in gaining reacceptance because it is observable by the majority (Study 2). These findings show that angry reactions are likely to trigger anti-conformity in a deviant, but they are also consistent with a motivational account of conformity, in which conformity is strategic behavior aimed at gaining reacceptance from the group. PMID:26124742

  9. Emotional reactions to deviance in groups: the relation between number of angry reactions, felt rejection, and conformity.

    Science.gov (United States)

    Heerdink, Marc W; van Kleef, Gerben A; Homan, Astrid C; Fischer, Agneta H

    2015-01-01

    How many members of a group need to express their anger in order to influence a deviant group member's behavior? In two studies, we examine whether an increase in number of angry group members affects the extent to which a deviant individual feels rejected, and we investigate downstream effects on conformity. We show that each additional angry reaction linearly increases the extent to which a deviant individual feels rejected, and that this relation is independent of the total number of majority members (Study 1). This felt rejection is then shown to lead to anti-conformity unless two conditions are met: (1) the deviant is motivated to seek reacceptance in the group, and (2) conformity is instrumental in gaining reacceptance because it is observable by the majority (Study 2). These findings show that angry reactions are likely to trigger anti-conformity in a deviant, but they are also consistent with a motivational account of conformity, in which conformity is strategic behavior aimed at gaining reacceptance from the group.

  10. Emotional Reactions to Deviance in Groups: The Relation between Number of Angry Reactions, Felt Rejection, and Conformity

    Directory of Open Access Journals (Sweden)

    Marc W. Heerdink

    2015-06-01

    Full Text Available How many members of a group need to express their anger in order to influence a deviant group member's behavior? In two studies, we examine whether an increase in number of angry group members affects the extent to which a deviant individual feels rejected, and we investigate downstream effects on conformity. We show that each additional angry reaction linearly increases the extent to which a deviant individual feels rejected, and that this relation is independent of the total number of majority members (Study 1. This felt rejection is then shown to lead to anti-conformity unless two conditions are met: (1 the deviant is motivated to seek reacceptance in the group, and (2 conformity is instrumental in gaining reacceptance because it is observable by the majority (Study 2. These findings show that angry reactions are likely to trigger anti-conformity in a deviant, but they are also consistent with a motivational account of conformity, in which conformity is strategic behavior aimed at gaining reacceptance from the group.

  11. Molecular simulations of RNA 2'-O-transesterification reaction models in solution.

    Science.gov (United States)

    Radak, Brian K; Harris, Michael E; York, Darrin M

    2013-01-10

    We employ quantum mechanical/molecular mechanical umbrella sampling simulations to probe the free energy surfaces of a series of increasingly complex reaction models of RNA 2'-O-transesterification in aqueous solution under alkaline conditions. Such models are valuable for understanding the uncatalyzed processes underlying catalytic cleavage of the phosphodiester backbone of RNA, a reaction of fundamental importance in biology. The chemically reactive atoms are modeled by the AM1/d-PhoT quantum model for phosphoryl transfer, whereas the aqueous solvation environment is modeled with a molecular mechanics force field. Several simulation protocols were compared that used different ionic conditions and force field models. The results provide insight into how variation of the structural environment of the nucleophile and leaving group affects the free energy profile for the transesterification reaction. Results for a simple RNA backbone model are compared with recent experiments by Harris et al. on the specific base-catalyzed cleavage of a UpG dinucleotide. The calculated and measured free energies of activation match extremely well (ΔF(‡) = 19.9-20.8 vs 19.9 kcal/mol). Solvation is seen to play a crucial role and is characterized by a network of hydrogen bonds that envelopes the pentacoordinate dianionic phosphorane transition state and provides preferential stabilization relative to the reactant state.

  12. Real-time monitoring of mass-transport-related enzymatic reaction kinetics in a nanochannel-array reactor.

    Science.gov (United States)

    Li, Su-Juan; Wang, Chen; Wu, Zeng-Qiang; Xu, Jing-Juan; Xia, Xing-Hua; Chen, Hong-Yuan

    2010-09-01

    To understand the fundamentals of enzymatic reactions confined in micro-/nanosystems, the construction of a small enzyme reactor coupled with an integrated real-time detection system for monitoring the kinetic information is a significant challenge. Nano-enzyme array reactors were fabricated by covalently linking enzymes to the inner channels of a porous anodic alumina (PAA) membrane. The mechanical stability of this nanodevice enables us to integrate an electrochemical detector for the real-time monitoring of the formation of the enzyme reaction product by sputtering a thin Pt film on one side of the PAA membrane. Because the enzymatic reaction is confined in a limited nanospace, the mass transport of the substrate would influence the reaction kinetics considerably. Therefore, the oxidation of glucose by dissolved oxygen catalyzed by immobilized glucose oxidase was used as a model to investigate the mass-transport-related enzymatic reaction kinetics in confined nanospaces. The activity and stability of the enzyme immobilized in the nanochannels was enhanced. In this nano-enzyme reactor, the enzymatic reaction was controlled by mass transport if the flux was low. With an increase in the flux (e.g., >50 microL min(-1)), the enzymatic reaction kinetics became the rate-determining step. This change resulted in the decrease in the conversion efficiency of the nano-enzyme reactor and the apparent Michaelis-Menten constant with an increase in substrate flux. This nanodevice integrated with an electrochemical detector could help to understand the fundamentals of enzymatic reactions confined in nanospaces and provide a platform for the design of highly efficient enzyme reactors. In addition, we believe that such nanodevices will find widespread applications in biosensing, drug screening, and biochemical synthesis.

  13. A Reaction-Diffusion Model of Cholinergic Retinal Waves

    Science.gov (United States)

    Lansdell, Benjamin; Ford, Kevin; Kutz, J. Nathan

    2014-01-01

    Prior to receiving visual stimuli, spontaneous, correlated activity in the retina, called retinal waves, drives activity-dependent developmental programs. Early-stage waves mediated by acetylcholine (ACh) manifest as slow, spreading bursts of action potentials. They are believed to be initiated by the spontaneous firing of Starburst Amacrine Cells (SACs), whose dense, recurrent connectivity then propagates this activity laterally. Their inter-wave interval and shifting wave boundaries are the result of the slow after-hyperpolarization of the SACs creating an evolving mosaic of recruitable and refractory cells, which can and cannot participate in waves, respectively. Recent evidence suggests that cholinergic waves may be modulated by the extracellular concentration of ACh. Here, we construct a simplified, biophysically consistent, reaction-diffusion model of cholinergic retinal waves capable of recapitulating wave dynamics observed in mice retina recordings. The dense, recurrent connectivity of SACs is modeled through local, excitatory coupling occurring via the volume release and diffusion of ACh. In addition to simulation, we are thus able to use non-linear wave theory to connect wave features to underlying physiological parameters, making the model useful in determining appropriate pharmacological manipulations to experimentally produce waves of a prescribed spatiotemporal character. The model is used to determine how ACh mediated connectivity may modulate wave activity, and how parameters such as the spontaneous activation rate and sAHP refractory period contribute to critical wave size variability. PMID:25474327

  14. Three-Body Model Analysis of Subbarrier alpha Transfer Reaction

    CERN Document Server

    Fukui, Tokuro; Yahiro, Masanobu

    2011-01-01

    Subbarrier alpha transfer reaction 13C(6Li,d)17O(6.356 MeV, 1/2+) at 3.6 MeV is analyzed with a alpha + d + 13C three-body model, and the asymptotic normalization coefficient (ANC) for alpha + 13C --> 17O(6.356 MeV, 1/2+), which essentially determines the reaction rate of 13C(alpha,n)16O, is extracted. Breakup effects of 6Li in the initial channel and those of 17O in the final channel are investigated with the continuum-discretized coupled-channels method (CDCC). The former is found to have a large back-coupling to the elastic channel, while the latter turns out significantly small. The transfer cross section calculated with Born approximation to the transition operator, including breakup states of 6Li, gives (C_{alpha 13C}{17O*})^2 =1.03 \\pm 0.29 fm^{-1}. This result is consistent with the value obtained by the previous DWBA calculation.

  15. A multi-pathway model for Photosynthetic reaction center

    CERN Document Server

    Qin, M; Yi, X X

    2015-01-01

    Charge separation in light-harvesting complexes occurs in a pair of tightly coupled chlorophylls at the heart of photosynthetic reaction centers of both plants and bacteria. Recently it has been shown that quantum coherence can, in principle, enhance the efficiency of a solar cell, working like a quantum heat engine (QHE). Here, we propose a biological quantum heat engine (BQHE) motivated by Photosystem {\\rm II} reaction center (PS{\\rm II} RC) to describe the charge separation. Our model mainly considers two charge-separation pathways more than that in the published literature. The two pathways can interfere via cross-couplings and work together to enhance the charge-separation yields. We explore how these cross-couplings increase the current and voltage of the charge separation and discuss the advantages of multiple pathways in terms of current and power. The robustness of the BQHE against the charge recombination in natural PS{\\rm II} RC and dephasing induced by environments is also explored, and extension ...

  16. The Relative Salience of Daily and Enduring Influences on Off-Job Reactions to Work Stress.

    Science.gov (United States)

    Calderwood, Charles; Ackerman, Phillip L

    2016-12-01

    Work stress is an important determinant of employee health and wellness. The occupational health community is recognizing that one contributor to these relationships may be the presence of negative off-job reactivity to work, which we argue involves continued thoughts directed towards work (cognitive reactivity), continued negative mood stemming from work (affective reactivity), and the alteration of post-work behaviours in response to work factors (behavioural reactivity). We explored the relative contributions of daily work stressors, affective traits, and subjective job stress perceptions to negative off-job reactivity. These relationships were evaluated in a study of hospital nurses (n = 75), who completed trait measures and then provided self-assessments of daily work stress and off-job reactions for four work days. The results of several multilevel analyses indicated that a main-effects model best described the data when predicting cognitive, affective, and behavioural reactivity from daily work stressors, affective traits, and subjective job stress perceptions. A series of multilevel dominance analyses revealed that subjective job stress perceptions dominated the prediction of behavioural reactivity, while trait negative affect dominated the prediction of affective reactivity. Theoretical implications and the relative salience of daily and enduring contributors to negative off-job reactivity are discussed. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  17. Small-scale behaviour in deterministic reaction models

    Energy Technology Data Exchange (ETDEWEB)

    Politi, Paolo [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Ben-Avraham, Daniel, E-mail: paolo.politi@isc.cnr.i, E-mail: benavraham@clarkson.ed [Physics Department, Clarkson University, Potsdam, NY 13699-5820 (United States)

    2010-10-08

    In a recent paper published in this journal (2009 J. Phys. A: Math. Theor. 42 495004) we studied a one-dimensional particles system where nearest particles attract with a force inversely proportional to a power {alpha} of their distance and coalesce upon encounter. Numerics yielded a distribution function h(z) for the gap between neighbouring particles, with h(z) {approx} z{sup {beta}({alpha})} for small z and {beta}({alpha}) > {alpha}. We can now prove analytically that in the strict limit of z {yields} 0, {beta} = {alpha} for {alpha} > 0, corresponding to the mean-field result, and we compute the length scale where the mean field breaks down. More generally, in that same limit correlations are negligible for any similar reaction model where attractive forces diverge with vanishing distance. The actual meaning of the measured exponent {beta}({alpha}) remains an open question.

  18. [Distribution model of aluminum species in drinking water basing on the reaction kinetics].

    Science.gov (United States)

    Wang, Wen-dong; Yang, Hong-wei; Wang, Xiao-chang; Jiang, Jing; Zhu, Wan-peng; Jiang, Zhan-peng

    2010-04-01

    The effects of excess aluminum on water distribution system and human health were mainly attributable to the presences of some aluminum species in drinking water. A prediction model for the concentrations of aluminum species was developed using three-layer front feedback artificial neural network method. Results showed that the reaction rates of both inorganic monomeric aluminum and soluble aluminum varied with reaction time and water quality parameters, such as water temperature, pH, total aluminum, fluoride, phosphate and silicate. Their reaction orders were both three. The reaction kinetic parameters of inorganic monomeric aluminum and soluble aluminum could be predicted effectively applying artificial neural network; the correlation coefficients of k and 1/C0(2) between calculated value and predicted value were both greater than 0.999. Aluminum species prediction results in the drinking water of City M showed that when the concentration of total aluminum was less than 0.05 mg x L(-1), the relative prediction error was large for inorganic monomeric aluminum. When the concentration of total aluminum was above 0.05 mg x L(-1), the model could predict inorganic monomeric aluminum and soluble aluminum concentrations effectively, with relative prediction errors of +/- 15% and +/- 10% respectively.

  19. a Model Study of Complex Behavior in the Belousov - Reaction.

    Science.gov (United States)

    Lindberg, David Mark

    1988-12-01

    We have studied the complex oscillatory behavior in a model of the Belousov-Zhabotinskii (BZ) reaction in a continuously-fed stirred tank reactor (CSTR). The model consisted of a set of nonlinear ordinary differential equations derived from a reduced mechanism of the chemical system. These equations were integrated numerically on a computer, which yielded the concentrations of the constituent chemicals as functions of time. In addition, solutions were tracked as functions of a single parameter, the stability of the solutions was determined, and bifurcations of the solutions were located and studied. The intent of this study was to use this BZ model to explore further a region of complex oscillatory behavior found in experimental investigations, the most thorough of which revealed an alternating periodic-chaotic (P-C) sequence of states. A P-C sequence was discovered in the model which showed the same qualitative features as the experimental sequence. In order to better understand the P-C sequence, a detailed study was conducted in the vicinity of the P-C sequence, with two experimentally accessible parameters as control variables. This study mapped out the bifurcation sets, and included examination of the dynamics of the stable periodic, unstable periodic, and chaotic oscillatory motion. Observations made from the model results revealed a rough symmetry which suggests a new way of looking at the P-C sequence. Other nonlinear phenomena uncovered in the model were boundary and interior crises, several codimension-two bifurcations, and similarities in the shapes of areas of stability for periodic orbits in two-parameter space. Each earlier model study of this complex region involved only a limited one-parameter scan and had limited success in producing agreement with experiments. In contrast, for those regions of complex behavior that have been studied experimentally, the observations agree qualitatively with our model results. Several new predictions of the model

  20. Multiphasic Reaction Modeling for Polypropylene Production in a Pilot-Scale Catalytic Reactor

    Directory of Open Access Journals (Sweden)

    Mohammad Jakir Hossain Khan

    2016-06-01

    related to the dynamic bed parameters for the separate phases and is also capable of computing the chemical reaction rate for every phase in the reaction. Our improved mutiphasic model revealed similar dynamic behaviour as the conventional model in the initial stages of the polymerization reaction; however, it diverged as time progressed.

  1. A Stefan model for mass transfer in a rotating disk reaction vessel

    KAUST Repository

    BOHUN, C. S.

    2015-05-04

    Copyright © Cambridge University Press 2015. In this paper, we focus on the process of mass transfer in the rotating disk apparatus formulated as a Stefan problem with consideration given to both the hydrodynamics of the process and the specific chemical reactions occurring in the bulk. The wide range in the reaction rates of the underlying chemistry allows for a natural decoupling of the problem into a simplified set of weakly coupled convective-reaction-diffusion equations for the slowly reacting chemical species and a set of algebraic relations for the species that react rapidly. An analysis of the chemical equilibrium conditions identifies an expansion parameter and a reduced model that remains valid for arbitrarily large times. Numerical solutions of the model are compared to an asymptotic analysis revealing three distinct time scales and chemical diffusion boundary layer that lies completely inside the hydrodynamic layer. Formulated as a Stefan problem, the model generalizes the work of Levich (Levich and Spalding (1962) Physicochemical hydrodynamics, vol. 689, Prentice-Hall Englewood Cliffs, NJ) and will help better understand the natural limitations of the rotating disk reaction vessel when consideration is made for the reacting chemical species.

  2. Uniform asymptotic approximation of diffusion to a small target: Generalized reaction models

    Science.gov (United States)

    Isaacson, Samuel A.; Mauro, Ava J.; Newby, Jay

    2016-10-01

    The diffusion of a reactant to a binding target plays a key role in many biological processes. The reaction radius at which the reactant and target may interact is often a small parameter relative to the diameter of the domain in which the reactant diffuses. We develop uniform in time asymptotic expansions in the reaction radius of the full solution to the corresponding diffusion equations for two separate reactant-target interaction mechanisms: the Doi or volume reactivity model and the Smoluchowski-Collins-Kimball partial-absorption surface reactivity model. In the former, the reactant and target react with a fixed probability per unit time when within a specified separation. In the latter, upon reaching a fixed separation, they probabilistically react or the reactant reflects away from the target. Expansions of the solution to each model are constructed by projecting out the contribution of the first eigenvalue and eigenfunction to the solution of the diffusion equation and then developing matched asymptotic expansions in Laplace-transform space. Our approach offers an equivalent, but alternative, method to the pseudopotential approach we previously employed [Isaacson and Newby, Phys. Rev. E 88, 012820 (2013), 10.1103/PhysRevE.88.012820] for the simpler Smoluchowski pure-absorption reaction mechanism. We find that the resulting asymptotic expansions of the diffusion equation solutions are identical with the exception of one parameter: the diffusion-limited reaction rates of the Doi and partial-absorption models. This demonstrates that for biological systems in which the reaction radius is a small parameter, properly calibrated Doi and partial-absorption models may be functionally equivalent.

  3. Chemical Reaction and Flow Modeling in Fullerene and Nanotube Production

    Science.gov (United States)

    Scott, Carl D.; Farhat, Samir; Greendyke, Robert B.

    2004-01-01

    The development of processes to produce fullerenes and carbon nanotubes has largely been empirical. Fullerenes were first discovered in the soot produced by laser ablation of graphite [1]and then in the soot of electric arc evaporated carbon. Techniques and conditions for producing larger and larger quantities of fullerenes depended mainly on trial and error empirical variations of these processes, with attempts to scale them up by using larger electrodes and targets and higher power. Various concepts of how fullerenes and carbon nanotubes were formed were put forth, but very little was done based on chemical kinetics of the reactions. This was mainly due to the complex mixture of species and complex nature of conditions in the reactors. Temperatures in the reactors varied from several thousand degrees Kelvin down to near room temperature. There are hundreds of species possible, ranging from atomic carbon to large clusters of carbonaceous soot, and metallic catalyst atoms to metal clusters, to complexes of metals and carbon. Most of the chemical kinetics of the reactions and the thermodynamic properties of clusters and complexes have only been approximated. In addition, flow conditions in the reactors are transient or unsteady, and three dimensional, with steep spatial gradients of temperature and species concentrations. All these factors make computational simulations of reactors very complex and challenging. This article addresses the development of the chemical reaction involved in fullerene production and extends this to production of carbon nanotubes by the laser ablation/oven process and by the electric arc evaporation process. In addition, the high-pressure carbon monoxide (HiPco) process is discussed. The article is in several parts. The first one addresses the thermochemical aspects of modeling; and considers the development of chemical rate equations, estimates of reaction rates, and thermodynamic properties where they are available. The second part

  4. Cerebral activation related to implicit sequence learning in a Double Serial Reaction Time task

    NARCIS (Netherlands)

    van der Graaf, FHCE; Maguire, RP; Leenders, KL; de Jong, BM

    2006-01-01

    Using functional magnetic resonance imaging (fMRI), we examined the distribution of cerebral activations related to implicitly learning a series of fixed stimulus-response combinations. In a novel - bimanual - variant of the Serial Reaction Time task (SRT), simultaneous finger movements of the two h

  5. The Relation Between Damping and Reaction Rates of Fermions in Hot Gauge Theories

    CERN Document Server

    Ayala, A P; Weber, A; Ayala, Alejandro; Olivo, Juan Carlos D'; Weber, Axel

    1998-01-01

    We examine the relation between the damping rate of a chiral fermion mode propagating in a hot plasma and the rate at which the mode approaches equilibrium. We show that these two quantities, obtained from the imaginary part of the fermion self-energy, are equal provided the reaction rate is defined using the appropriate wave function of the mode in the medium.

  6. Age-related accumulation of Maillard reaction products in human articular cartilage collagen

    NARCIS (Netherlands)

    Verzijl, N.; Groot, J. de; Oldehinkel, E.; Bank, R.A.; Thorpe, S.R.; Baynes, J.W.; Bayliss, M.T.; Bijlsma, J.W.J.; Lafeber, F.P.J.G.; TeKoppele, J.M.

    2000-01-01

    Non-enzymic modification of tissue proteins by reducing sugars, the so-called Maillard reaction, is a prominent feature of aging. In articular cartilage, relatively high levels of the advanced glycation end product (AGE) pentosidine accumulate with age. Higher pentosidine levels have been associated

  7. Adverse drug reaction-related hospitalisations: A nationwide study in The Netherlands

    NARCIS (Netherlands)

    C.S. van der Hooft (Cornelis); M.C.J.M. Sturkenboom (Miriam); K. van Grootheest (Kees); H.J. Kingma (Herre); B.H.Ch. Stricker (Bruno)

    2006-01-01

    textabstractBackground: The incidence of adverse drug reaction (ADR)-related hospitalisations has usually been assessed within hospitals. Because of the variability in results and methodology, it is difficult to extrapolate these results to a national level. Objectives: To evaluate the incidence and

  8. Cognitive-behavioral treatment for chronic nightmares in trauma-exposed persons: assessing physiological reactions to nightmare-related fear.

    Science.gov (United States)

    Rhudy, Jamie L; Davis, Joanne L; Williams, Amy E; McCabe, Klanci M; Bartley, Emily J; Byrd, Patricia M; Pruiksma, Kristi E

    2010-04-01

    Cognitive-behavioral treatments (CBTs) that target nightmares are efficacious for ameliorating self-reported sleep problems and psychological distress. However, it is important to determine whether these treatments influence objective markers of nightmare-related fear, because fear and concomitant physiological responses could promote nightmare chronicity and sleep disturbance. This randomized, controlled study (N=40) assessed physiological (skin conductance, heart rate, facial electromyogram) and subjective (displeasure, fear, anger, sadness, arousal) reactions to personally relevant nightmare imagery intended to evoke nightmare-related fear. Physiological assessments were conducted at pretreatment as well as 1-week, 3-months, and 6-months posttreatment. Results of mixed effects analysis of variance models suggested treatment reduced physiological and subjective reactions to nightmare imagery, gains that were generally maintained at the 6-month follow-up. Potential implications are discussed.

  9. Reactions to penalties for an offense in relation to authoritarianism, values, perceived responsibility, perceived seriousness, and deservingness.

    Science.gov (United States)

    Feather, N T

    1996-09-01

    Two studies involving participants from metropolitan Adelaide, South Australia (Study 1: N = 220, Study 2: N = 181) examined variables that were assumed to influence cognitive and affective reactions to penalties imposed for offenses relating to domestic violence, plagiarism, and shoplifting (in Study 1), and resisting a police order in a protest against logging (in Study 2). Results of path analyses supported a model that assumed paths linking perceived responsibility to the perceived seriousness of an offense; responsibility and seriousness to deservingness of the penalty; deservingness to the perceived harshness of the penalty, to reported positive affect about the penalty, and to reported sympathy for the offender; and perceived harshness of the penalty to reported positive affect and sympathy. Right-wing authoritarianism and relevant values had direct effects on perceived seriousness consistent with the assumption that values affect the way an offense is construed in relation to its negative valence or aversiveness. Deservingness had a central role as a mediator of reactions.

  10. Cosmological models in general relativity

    Indian Academy of Sciences (India)

    B B Paul

    2003-12-01

    LRS Bianchi type-I space-time filled with perfect fluid is considered here with deceleration parameter as variable. The metric potentials and are functions of as well as . Assuming '/=(), where prime denotes differentiation with respect to , it was found that =('/) and =(), where =() and is the scale factor which is a function of only. The value of Hubble’s constant 0 was found to be less than half for non-flat model and is equal to 1.3 for a flat model.

  11. Statistical Model Calculations for (n,γ Reactions

    Directory of Open Access Journals (Sweden)

    Beard Mary

    2015-01-01

    Full Text Available Hauser-Feshbach (HF cross sections are of enormous importance for a wide range of applications, from waste transmutation and nuclear technologies, to medical applications, and nuclear astrophysics. It is a well-observed result that different nuclear input models sensitively affect HF cross section calculations. Less well known however are the effects on calculations originating from model-specific implementation details (such as level density parameter, matching energy, back-shift and giant dipole parameters, as well as effects from non-model aspects, such as experimental data truncation and transmission function energy binning. To investigate the effects or these various aspects, Maxwellian-averaged neutron capture cross sections have been calculated for approximately 340 nuclei. The relative effects of these model details will be discussed.

  12. Modeling reaction noise with a desired accuracy by using the X level approach reaction noise estimator (XARNES) method.

    Science.gov (United States)

    Konkoli, Zoran

    2012-07-21

    A novel computational method for modeling reaction noise characteristics has been suggested. The method can be classified as a moment closure method. The approach is based on the concept of correlation forms which are used for describing spatially extended many body problems where particle numbers change in space and time. In here, it was shown how the formalism of spatially extended correlation forms can be adapted to study well mixed reaction systems. Stochastic fluctuations in particle numbers are described by selectively capturing correlation effects up to the desired order, ξ. The method is referred to as the ξ-level Approximation Reaction Noise Estimator method (XARNES). For example, the ξ=1 description is equivalent to the mean field theory (first-order effects), the ξ=2 case corresponds to the previously developed PARNES method (pair effects), etc. The main idea is that inclusion of higher order correlation effects should lead to better (more accurate) results. Several models were used to test the method, two versions of a simple complex formation model, the Michaelis-Menten model of enzymatic kinetics, the smallest bistable reaction network, a gene expression network with negative feedback, and a random large network. It was explicitly demonstrated that increase in ξ indeed improves accuracy in all cases investigated. The approach has been implemented as automatic software using the Mathematica programming language. The user only needs to input reaction rates, stoichiometry coefficients, and the desired level of computation ξ.

  13. Using the Training Reactions Questionnaire to Analyze the Reactions of University Students Undergoing Career-Related Training in Jordan: A Prospective Human Resource Development Approach

    Science.gov (United States)

    Khasawneh, Samer; Al-Zawahreh, Abdelghafour

    2015-01-01

    The primary purpose of the present study was to validate Morgan and Casper's training reactions questionnaire (TRQ) for use in Jordan. The study also investigated the reactions of university students to career-related training programs. Another purpose of the study was to determine the impact of certain aspects of training programs on the…

  14. Using the Training Reactions Questionnaire to Analyze the Reactions of University Students Undergoing Career-Related Training in Jordan: A Prospective Human Resource Development Approach

    Science.gov (United States)

    Khasawneh, Samer; Al-Zawahreh, Abdelghafour

    2015-01-01

    The primary purpose of the present study was to validate Morgan and Casper's training reactions questionnaire (TRQ) for use in Jordan. The study also investigated the reactions of university students to career-related training programs. Another purpose of the study was to determine the impact of certain aspects of training programs on the overall…

  15. Generic Model-Based Tailor-Made Design and Analysis of Biphasic Reaction Systems

    DEFF Research Database (Denmark)

    Anantpinijwatna, Amata

    contribution of this thesis is the development of a systematic modelling framework for the biphasic reaction system. The developed framework consists of three modules describing phase equilibria, reactions and mass transfer, and material balances of such processes. Correlative and predictive thermodynamic......-elementary reaction rate laws. Extents of reaction are used to calculate the species material balances. The resulting mathematical model contains temperature dependent reaction rate parameters,equilibrium constants, and partition coefficients; where only the reaction rates are to be regressed to a minimum of time...

  16. Statistical model analysis of α -induced reaction cross sections of 64Zn at low energies

    Science.gov (United States)

    Mohr, P.; Gyürky, Gy.; Fülöp, Zs.

    2017-01-01

    Background: α -nucleus potentials play an essential role in the calculation of α -induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions (typically at higher energies) and to the energy dependence of the effective α -nucleus potentials. Purpose: The present work studies cross sections of α -induced reactions for 64Zn at low energies and their dependence on the chosen input parameters of the statistical model calculations. The new experimental data from the recent Atomki experiments allow for a χ2-based estimate of the uncertainties of calculated cross sections at very low energies. Method: Recently measured data for the (α ,γ ), (α ,n ), and (α ,p ) reactions on 64Zn are compared to calculations in the statistical model. A survey of the parameter space of the widely used computer code talys is given, and the properties of the obtained χ2 landscape are discussed. Results: The best fit to the experimental data at low energies shows χ2/F ≈7.7 per data point, which corresponds to an average deviation of about 30% between the best fit and the experimental data. Several combinations of the various ingredients of the statistical model are able to reach a reasonably small χ2/F , not exceeding the best-fit result by more than a factor of 2. Conclusions: The present experimental data for 64Zn in combination with the statistical model calculations allow us to constrain the astrophysical reaction rate within about a factor of 2. However, the significant excess of χ2/F of the best fit from unity demands further improvement of the statistical model calculations and, in particular, the α -nucleus potential.

  17. A Semi-Empirical Two Step Carbon Corrosion Reaction Model in PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Young, Alan; Colbow, Vesna; Harvey, David; Rogers, Erin; Wessel, Silvia

    2013-01-01

    The cathode CL of a polymer electrolyte membrane fuel cell (PEMFC) was exposed to high potentials, 1.0 to 1.4 V versus a reversible hydrogen electrode (RHE), that are typically encountered during start up/shut down operation. While both platinum dissolution and carbon corrosion occurred, the carbon corrosion effects were isolated and modeled. The presented model separates the carbon corrosion process into two reaction steps; (1) oxidation of the carbon surface to carbon-oxygen groups, and (2) further corrosion of the oxidized surface to carbon dioxide/monoxide. To oxidize and corrode the cathode catalyst carbon support, the CL was subjected to an accelerated stress test cycled the potential from 0.6 VRHE to an upper potential limit (UPL) ranging from 0.9 to 1.4 VRHE at varying dwell times. The reaction rate constants and specific capacitances of carbon and platinum were fitted by evaluating the double layer capacitance (Cdl) trends. Carbon surface oxidation increased the Cdl due to increased specific capacitance for carbon surfaces with carbon-oxygen groups, while the second corrosion reaction decreased the Cdl due to loss of the overall carbon surface area. The first oxidation step differed between carbon types, while both reaction rate constants were found to have a dependency on UPL, temperature, and gas relative humidity.

  18. A coupled mechanical and chemical damage model for concrete affected by alkali–silica reaction

    Energy Technology Data Exchange (ETDEWEB)

    Pignatelli, Rossella, E-mail: rossellapignatelli@gmail.com [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Lombardi Ingegneria S.r.l., Via Giotto 36, 20145 Milano (Italy); Comi, Claudia, E-mail: comi@stru.polimi.it [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

    2013-11-15

    To model the complex degradation phenomena occurring in concrete affected by alkali–silica reaction (ASR), we formulate a poro-mechanical model with two isotropic internal variables: the chemical and the mechanical damage. The chemical damage, related to the evolution of the reaction, is caused by the pressure generated by the expanding ASR gel on the solid concrete skeleton. The mechanical damage describes the strength and stiffness degradation induced by the external loads. As suggested by experimental results, degradation due to ASR is considered to be localized around reactive sites. The effect of the degree of saturation and of the temperature on the reaction development is also modeled. The chemical damage evolution is calibrated using the value of the gel pressure estimated by applying the electrical diffuse double-layer theory to experimental values of the surface charge density in ASR gel specimens reported in the literature. The chemo-damage model is first validated by simulating expansion tests on reactive specimens and beams; the coupled chemo-mechanical damage model is then employed to simulate compression and flexure tests results also taken from the literature. -- Highlights: •Concrete degradation due to ASR in variable environmental conditions is modeled. •Two isotropic internal variables – chemical and mechanical damage – are introduced. •The value of the swelling pressure is estimated by the diffuse double layer theory. •A simplified scheme is proposed to relate macro- and microscopic properties. •The chemo-mechanical damage model is validated by simulating tests in literature.

  19. Sex differences in relations of muscle power, lung function, and reaction time in athletes.

    Science.gov (United States)

    Gursoy, Recep

    2010-06-01

    In an earlier study, relations of nonverbal abilities with several bodily measures such as height, weight, and lung capacity were observed. The present aim was estimation of associations of muscle power and lung function with simple eye-hand reaction time. Sex differences for muscle power were significant even with the covariates of height, weight, and age included; however, these disappeared for lung functions (forced vital capacity and peak expiratory flow) and reaction time. The effects of leg power, forced vital capacity, and peak expiratory flow on the left eye-hand reaction time were significant after adjustment for height, weight, right- and left-hand powers and age. The positive effect of exercise may be especially associated with the right brain activity or left hand speed.

  20. A reaction diffusion model of pattern formation in clustering of adatoms on silicon surfaces

    Directory of Open Access Journals (Sweden)

    Trilochan Bagarti

    2012-12-01

    Full Text Available We study a reaction diffusion model which describes the formation of patterns on surfaces having defects. Through this model, the primary goal is to study the growth process of Ge on Si surface. We consider a two species reaction diffusion process where the reacting species are assumed to diffuse on the two dimensional surface with first order interconversion reaction occuring at various defect sites which we call reaction centers. Two models of defects, namely a ring defect and a point defect are considered separately. As reaction centers are assumed to be strongly localized in space, the proposed reaction-diffusion model is found to be exactly solvable. We use Green's function method to study the dynamics of reaction diffusion processes. Further we explore this model through Monte Carlo (MC simulations to study the growth processes in the presence of a large number of defects. The first passage time statistics has been studied numerically.

  1. Emotional reactions to involuntary psychiatric hospitalization and stigma-related stress among people with mental illness.

    Science.gov (United States)

    Rüsch, Nicolas; Müller, Mario; Lay, Barbara; Corrigan, Patrick W; Zahn, Roland; Schönenberger, Thekla; Bleiker, Marco; Lengler, Silke; Blank, Christina; Rössler, Wulf

    2014-02-01

    Compulsory admission to psychiatric inpatient treatment can be experienced as disempowering and stigmatizing by people with serious mental illness. However, quantitative studies of stigma-related emotional and cognitive reactions to involuntary hospitalization and their impact on people with mental illness are scarce. Among 186 individuals with serious mental illness and a history of recent involuntary hospitalization, shame and self-contempt as emotional reactions to involuntary hospitalization, the cognitive appraisal of stigma as a stressor, self-stigma, empowerment as well as quality of life and self-esteem were assessed by self-report. Psychiatric symptoms were rated by the Brief Psychiatric Rating Scale. In multiple linear regressions, more self-stigma was predicted independently by higher levels of shame, self-contempt and stigma stress. A greater sense of empowerment was related to lower levels of stigma stress and self-contempt. These findings remained significant after controlling for psychiatric symptoms, diagnosis, age, gender and the number of lifetime involuntary hospitalizations. Increased self-stigma and reduced empowerment in turn predicted poorer quality of life and reduced self-esteem. The negative effect of emotional reactions and stigma stress on quality of life and self-esteem was largely mediated by increased self-stigma and reduced empowerment. Shame and self-contempt as reactions to involuntary hospitalization as well as stigma stress may lead to self-stigma, reduced empowerment and poor quality of life. Emotional and cognitive reactions to coercion may determine its impact more than the quantity of coercive experiences. Interventions to reduce the negative effects of compulsory admissions should address emotional reactions and stigma as a stressor.

  2. Stability Analysis of a Reaction-Diffusion System Modeling Atherogenesis

    KAUST Repository

    Ibragimov, Akif

    2010-01-01

    This paper presents a linear, asymptotic stability analysis for a reaction-diffusionconvection system modeling atherogenesis, the initiation of atherosclerosis, as an inflammatory instability. Motivated by the disease paradigm articulated by Ross, atherogenesis is viewed as an inflammatory spiral with a positive feedback loop involving key cellular and chemical species interacting and reacting within the intimal layer of muscular arteries. The inflammatory spiral is initiated as an instability from a healthy state which is defined to be an equilibrium state devoid of certain key inflammatory markers. Disease initiation is studied through a linear, asymptotic stability analysis of a healthy equilibrium state. Various theorems are proved, giving conditions on system parameters guaranteeing stability of the health state, and a general framework is developed for constructing perturbations from a healthy state that exhibit blow-up, which are interpreted as corresponding to disease initiation. The analysis reveals key features that arterial geometry, antioxidant levels, and the source of inflammatory components (through coupled third-kind boundary conditions or through body sources) play in disease initiation. © 2010 Society for Industrial and Applied Mathematics.

  3. Golden rule kinetics of transfer reactions in condensed phase: The microscopic model of electron transfer reactions in disordered solid matrices

    Energy Technology Data Exchange (ETDEWEB)

    Basilevsky, M. V.; Mitina, E. A. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); Odinokov, A. V. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); National Research Nuclear University “MEPhI,” 31, Kashirskoye shosse, Moscow (Russian Federation); Titov, S. V. [Karpov Institute of Physical Chemistry, 3-1/12, Building 6, Obuha pereulok, Moscow (Russian Federation)

    2013-12-21

    kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

  4. On the relative preference of enamine/iminium pathways in an organocatalytic Michael addition reaction.

    Science.gov (United States)

    Patil, Mahendra P; Sunoj, Raghavan B

    2009-05-04

    The mechanism of the organocatalyzed Michael addition between propanal and methyl vinyl ketone is investigated using the density functional and ab intio methods. Different modes of substrate activation offered by a secondary amine (pyrrolidine) organocatalyst are reported. The electrophilic activation of enone (P-I) through the formation of an iminium ion, and nucleophilic activation of propanal (P-II) in the form of enamine have been examined by identifying the corresponding transition states. The kinetic preference for the formation of key intermediates is established in an effort to identify the competing pathways associated with the title reaction. A comparison of barriers associated with different pathways as well as intermediate formation allows us to provide a suitable mechanistic rationale for Michael addition reactions catalyzed by a secondary amine. The overall barriers for the C-C bond formation pathways involving enol or iminium intermediates are identified as higher than the enamine pathway. Additionally, the generation of iminium is found to be less favored as compared to enamine formation. The effect of co-catalyst/protic solvent on the energetics of the overall reaction is also studied using the cluster continuum approach. Significant reduction in the activation energies for each step of the reaction is predicted for the solvent-assisted models. The co-catalyst assisted addition of propanal-enamine to methyl vinyl ketone is identified as the most preferred pathway (P-IV) for the Michael addition reaction. The results are in concurrence with the available experimental reports on the rate acceleration by the use of a co-catalyst in this reaction.

  5. Mass action realizations of reaction kinetic system models on various time scales

    Energy Technology Data Exchange (ETDEWEB)

    Hangos, K M; Szederkenyi, G, E-mail: hangos@scl.sztaki.hu, E-mail: szeder@scl.sztaki.hu [Process Control Research Group, Computer and Automation Reseach Institute, Kende u. 13-17, H-1111 Budapest (Hungary)

    2011-01-01

    Complex chemical reaction networks often exhibit different dynamic behaviour on different time scales. A combined approach is proposed in this work for determining physically meaningful mass action realizations of complex chemical reaction networks that describe its dynamic behaviour on different time scales. This is achieved by appropriately reducing the detailed overall mass action kinetic scheme using quasi steady state assumptions fit to the particular time scale, and then searching for an optimal realization using mixed integer linear programing. Furthermore, the relationship between the properties (reversibility, deficiency, stability) of the obtained realizations of the same system on different time scales are also investigated and related to the same properties of the detailed overall model. It is shown that the reduced models obtained by quasi steady state assumptions may show exotic nonlinear behaviour, such as oscillations, when the original detailed is globally asymptotically stable. The proposed methods are illustrated by using a simple Michaelis-Menten type reaction kinetic example. The simplified versions of the well known Brusselator model have also been investigated and presented as a case study.

  6. Constructing and visualizing chemical reaction networks from pi-calculus models

    OpenAIRE

    M. John; H.-J. Schulz; H. Schumann; A. M. Uhrmacher; Andrea Unger

    2013-01-01

    International audience; The pi-calculus, in particular its stochastic version the stochastic pi-calculus, is a common modeling formalism to concisely describe the chemical reactions occurring in biochemical systems. However, it remains largely unexplored how to transform a biochemical model expressed in the stochastic pi-calculus back into a set of meaningful reactions. To this end, we present a two step approach of first translating model states to reaction sets and then visualizing sequence...

  7. Relative risk regression models with inverse polynomials.

    Science.gov (United States)

    Ning, Yang; Woodward, Mark

    2013-08-30

    The proportional hazards model assumes that the log hazard ratio is a linear function of parameters. In the current paper, we model the log relative risk as an inverse polynomial, which is particularly suitable for modeling bounded and asymmetric functions. The parameters estimated by maximizing the partial likelihood are consistent and asymptotically normal. The advantages of the inverse polynomial model over the ordinary polynomial model and the fractional polynomial model for fitting various asymmetric log relative risk functions are shown by simulation. The utility of the method is further supported by analyzing two real data sets, addressing the specific question of the location of the minimum risk threshold.

  8. DL-ADR: a novel deep learning model for classifying genomic variants into adverse drug reactions.

    Science.gov (United States)

    Liang, Zhaohui; Huang, Jimmy Xiangji; Zeng, Xing; Zhang, Gang

    2016-08-10

    Genomic variations are associated with the metabolism and the occurrence of adverse reactions of many therapeutic agents. The polymorphisms on over 2000 locations of cytochrome P450 enzymes (CYP) due to many factors such as ethnicity, mutations, and inheritance attribute to the diversity of response and side effects of various drugs. The associations of the single nucleotide polymorphisms (SNPs), the internal pharmacokinetic patterns and the vulnerability of specific adverse reactions become one of the research interests of pharmacogenomics. The conventional genomewide association studies (GWAS) mainly focuses on the relation of single or multiple SNPs to a specific risk factors which are a one-to-many relation. However, there are no robust methods to establish a many-to-many network which can combine the direct and indirect associations between multiple SNPs and a serial of events (e.g. adverse reactions, metabolic patterns, prognostic factors etc.). In this paper, we present a novel deep learning model based on generative stochastic networks and hidden Markov chain to classify the observed samples with SNPs on five loci of two genes (CYP2D6 and CYP1A2) respectively to the vulnerable population of 14 types of adverse reactions. A supervised deep learning model is proposed in this study. The revised generative stochastic networks (GSN) model with transited by the hidden Markov chain is used. The data of the training set are collected from clinical observation. The training set is composed of 83 observations of blood samples with the genotypes respectively on CYP2D6*2, *10, *14 and CYP1A2*1C, *1 F. The samples are genotyped by the polymerase chain reaction (PCR) method. A hidden Markov chain is used as the transition operator to simulate the probabilistic distribution. The model can perform learning at lower cost compared to the conventional maximal likelihood method because the transition distribution is conditional on the previous state of the hidden Markov

  9. Modeling adsorption and reactions of organic molecules at metal surfaces.

    Science.gov (United States)

    Liu, Wei; Tkatchenko, Alexandre; Scheffler, Matthias

    2014-11-18

    CONSPECTUS: The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid inorganic/organic systems (HIOS) are relevant for many applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. Obviously, the predictive modeling and understanding of the structure and stability of such hybrid systems is an essential prerequisite for tuning their electronic properties and functions. At present, density-functional theory (DFT) is the most promising approach to study the structure, stability, and electronic properties of complex systems, because it can be applied to both molecules and solids comprising thousands of atoms. However, state-of-the-art approximations to DFT do not provide a consistent and reliable description for HIOS, which is largely due to two issues: (i) the self-interaction of the electrons with themselves arising from the Hartree term of the total energy that is not fully compensated in approximate exchange-correlation functionals, and (ii) the lack of long-range part of the ubiquitous van der Waals (vdW) interactions. The self-interaction errors sometimes lead to incorrect description of charge transfer and electronic level alignment in HIOS, although for molecules adsorbed on metals these effects will often cancel out in total energy differences. Regarding vdW interactions, several promising vdW-inclusive DFT-based methods have been recently demonstrated to yield remarkable accuracy for intermolecular interactions in the gas phase. However, the majority of these approaches neglect the nonlocal collective electron response in the vdW energy tail, an effect that is particularly strong in condensed phases and at interfaces between different materials. Here we show that the recently developed DFT+vdW(surf) method that accurately accounts for the collective electronic

  10. Atmospheric reaction systems as null-models to identify structural traces of evolution in metabolism.

    Directory of Open Access Journals (Sweden)

    Petter Holme

    Full Text Available The metabolism is the motor behind the biological complexity of an organism. One problem of characterizing its large-scale structure is that it is hard to know what to compare it to. All chemical reaction systems are shaped by the same physics that gives molecules their stability and affinity to react. These fundamental factors cannot be captured by standard null-models based on randomization. The unique property of organismal metabolism is that it is controlled, to some extent, by an enzymatic machinery that is subject to evolution. In this paper, we explore the possibility that reaction systems of planetary atmospheres can serve as a null-model against which we can define metabolic structure and trace the influence of evolution. We find that the two types of data can be distinguished by their respective degree distributions. This is especially clear when looking at the degree distribution of the reaction network (of reaction connected to each other if they involve the same molecular species. For the Earth's atmospheric network and the human metabolic network, we look into more detail for an underlying explanation of this deviation. However, we cannot pinpoint a single cause of the difference, rather there are several concurrent factors. By examining quantities relating to the modular-functional organization of the metabolism, we confirm that metabolic networks have a more complex modular organization than the atmospheric networks, but not much more. We interpret the more variegated modular arrangement of metabolism as a trace of evolved functionality. On the other hand, it is quite remarkable how similar the structures of these two types of networks are, which emphasizes that the constraints from the chemical properties of the molecules has a larger influence in shaping the reaction system than does natural selection.

  11. Empirical valence bond model of an SN2 reaction in polar and nonpolar solvents

    Science.gov (United States)

    Benjamin, Ilan

    2008-08-01

    A new model for the substitution nucleophilic reaction (SN2) in solution is described using the empirical valence bond (EVB) method. The model includes a generalization to three dimensions of a collinear gas phase EVB model developed by Mathis et al. [J. Mol. Liq. 61, 81 (1994)] and a parametrization of solute-solvent interactions of four different solvents (water, ethanol, chloroform, and carbon tetrachloride). The model is used to compute (in these four solvents) reaction free energy profiles, reaction and solvent dynamics, a two-dimensional reaction/solvent free energy map, as well as a number of other properties that in the past have mostly been estimated.

  12. Modelling of reaction cross sections and prompt neutron emission

    Science.gov (United States)

    Hambsch, F.-J.; Tudora, A.; Oberstedt, S.

    2010-10-01

    Accurate nuclear data concerning reaction cross sections and the emission of prompt fission neutrons (i.e. multiplicity and spectra) as well as other fission fragment data are of great importance for reactor physics design, especially for the new Generation IV nuclear energy systems. During the past years for several actinides (238U(n, f) and 237Np(n, f)) both the reaction cross sections and prompt neutron multiplicities and spectra have been calculated within the frame of the EFNUDAT project.

  13. Comparison of a Reaction Front Model and a Finite Difference Model for the Simulation of Solid Absorption Process

    Institute of Scientific and Technical Information of China (English)

    ZikangWu; ArneJakobsen; 等

    1994-01-01

    The pupose of this paper is to investigate the validity of a lumped model,i.e.a reaction front model,for the simulation of solid absorption process.A distributed model is developed for solid absorption process,and a dimensionless RF number is suggested to predict the qualitative shape of reaction degree profile.The simulation results from the reaction front model are compared with those from the distributed model solved by a finite difference scheme,and it is shown that they are in good agreement in almost all cased.no matter whether there is reaction front or not.

  14. A general paradigm to model reaction-based biogeochemical processes in batch systems

    Science.gov (United States)

    Fang, Yilin; Yeh, Gour-Tsyh; Burgos, William D.

    2003-04-01

    This paper presents the development and illustration of a numerical model of reaction-based geochemical and biochemical processes with mixed equilibrium and kinetic reactions. The objective is to provide a general paradigm for modeling reactive chemicals in batch systems, with expectations that it is applicable to reactive chemical transport problems. The unique aspects of the paradigm are to simultaneously (1) facilitate the segregation (isolation) of linearly independent kinetic reactions and thus enable the formulation and parameterization of individual rates one reaction by one reaction when linearly dependent kinetic reactions are absent, (2) enable the inclusion of virtually any type of equilibrium expressions and kinetic rates users want to specify, (3) reduce problem stiffness by eliminating all fast reactions from the set of ordinary differential equations governing the evolution of kinetic variables, (4) perform systematic operations to remove redundant fast reactions and irrelevant kinetic reactions, (5) systematically define chemical components and explicitly enforce mass conservation, (6) accomplish automation in decoupling fast reactions from slow reactions, and (7) increase the robustness of numerical integration of the governing equations with species switching schemes. None of the existing models to our knowledge has included these scopes simultaneously. This model (BIOGEOCHEM) is a general computer code to simulate biogeochemical processes in batch systems from a reaction-based mechanistic standpoint, and is designed to be easily coupled with transport models. To make the model applicable to a wide range of problems, programmed reaction types include aqueous complexation, adsorption-desorption, ion-exchange, oxidation-reduction, precipitation-dissolution, acid-base reactions, and microbial mediated reactions. In addition, user-specified reaction types can be programmed into the model. Any reaction can be treated as fast/equilibrium or slow

  15. A reaction-based river/stream water quality model: Model development and numerical schemes

    Science.gov (United States)

    Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Jardine, Philip M.

    2008-01-01

    SummaryThis paper presents the conceptual and mathematical development of a numerical model of sediment and reactive chemical transport in rivers and streams. The distribution of mobile suspended sediments and immobile bed sediments is controlled by hydrologic transport as well as erosion and deposition processes. The fate and transport of water quality constituents involving a variety of chemical and physical processes is mathematically described by a system of reaction equations for immobile constituents and advective-dispersive-reactive transport equations for mobile constituents. To circumvent stiffness associated with equilibrium reactions, matrix decomposition is performed via Gauss-Jordan column reduction. After matrix decomposition, the system of water quality constituent reactive transport equations is transformed into a set of thermodynamic equations representing equilibrium reactions and a set of transport equations involving no equilibrium reactions. The decoupling of equilibrium and kinetic reactions enables robust numerical integration of the partial differential equations (PDEs) for non-equilibrium-variables. Solving non-equilibrium-variable transport equations instead of individual water quality constituent transport equations also reduces the number of PDEs. A variety of numerical methods are investigated for solving the mixed differential and algebraic equations. Two verification examples are compared with analytical solutions to demonstrate the correctness of the code and to illustrate the importance of employing application-dependent numerical methods to solve specific problems.

  16. Theoretical reaction rates of the $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O reaction from the potential model

    CERN Document Server

    Katsuma, M

    2015-01-01

    The radiative capture cross sections of $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O and derived reaction rates are calculated from the direct capture potential model. The resulting $S$-factor at low energies is found to be dominated by $E$2 transition to the $^{16}$O ground state. The $E$1 and $E$2 $S$-factors at $E_{c.m.}=0.3$ MeV are $S_{E1}\\approx3$ keV~b and $S_{E2}=150^{+41}_{-17}$ keV~b, respectively. The sum of the cascade transition through the excited state of $^{16}$O is $S_{\\rm casc}= 18\\pm4.5$ keV~b. The derived reaction rates at low temperatures seem to be concordant with those from the previous evaluation. For astrophysical applications, our reaction rates below $T_9=3$ are provided in an analytic expression.

  17. Lifted Inference for Relational Continuous Models

    CERN Document Server

    Choi, Jaesik; Hill, David J

    2012-01-01

    Relational Continuous Models (RCMs) represent joint probability densities over attributes of objects, when the attributes have continuous domains. With relational representations, they can model joint probability distributions over large numbers of variables compactly in a natural way. This paper presents a new exact lifted inference algorithm for RCMs, thus it scales up to large models of real world applications. The algorithm applies to Relational Pairwise Models which are (relational) products of potentials of arity 2. Our algorithm is unique in two ways. First, it substantially improves the efficiency of lifted inference with variables of continuous domains. When a relational model has Gaussian potentials, it takes only linear-time compared to cubic time of previous methods. Second, it is the first exact inference algorithm which handles RCMs in a lifted way. The algorithm is illustrated over an example from econometrics. Experimental results show that our algorithm outperforms both a groundlevel inferenc...

  18. A priori modeling of chemical reactions on computational grid platforms: Workflows and data models

    Energy Technology Data Exchange (ETDEWEB)

    Rampino, S., E-mail: ser_ram@dyn.unipg.it [Dipartimento di Chimica, Universita degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia (Italy); Monari, A. [SRSMC-Equipe de Chimie et Biochimie Theoriques, Nancy-Universite et CNRS, Bp70239 Boulevard des Aiguilettes, 54506 Vandoeuvre-les-Nancy Cedex (France); Rossi, E. [CINECA, Via Manganelli 6/3, 40033 Casalecchio di Reno, Bologna (Italy); Evangelisti, S. [Laboratoire de Chimie et de Physique Quantiques, Universite Paul Sabatier Toulouse III et CNRS, 118 Route de Narbonne, 31062 Toulouse Cedex 4 (France); Lagana, A. [Dipartimento di Chimica, Universita degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia (Italy)

    2012-04-04

    Graphical abstract: The quantum framework of the Grid Empowered Molecular Simulator GEMS assembled on the European Grid allows the ab initio evaluation of the dynamics of small systems starting from the calculation of the electronic properties. Highlights: Black-Right-Pointing-Pointer The grid based GEMS simulator accurately models small chemical systems. Black-Right-Pointing-Pointer Q5Cost and D5Cost file formats provide interoperability in the workflow. Black-Right-Pointing-Pointer Benchmark runs on H + H{sub 2} highlight the Grid empowering. Black-Right-Pointing-Pointer O + O{sub 2} and N + N{sub 2} calculated k (T)'s fall within the error bars of the experiment. - Abstract: The quantum framework of the Grid Empowered Molecular Simulator GEMS has been assembled on the segment of the European Grid devoted to the Computational Chemistry Virtual Organization. The related grid based workflow allows the ab initio evaluation of the dynamics of small systems starting from the calculation of the electronic properties. Interoperability between computational codes across the different stages of the workflow was made possible by the use of the common data formats Q5Cost and D5Cost. Illustrative benchmark runs have been performed on the prototype H + H{sub 2}, N + N{sub 2} and O + O{sub 2} gas phase exchange reactions and thermal rate coefficients have been calculated for the last two. Results are discussed in terms of the modeling of the interaction and advantages of using the Grid is highlighted.

  19. Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems.

    Science.gov (United States)

    Zhang, Wei; Lai, Wenzhen; Cao, Rui

    2017-02-22

    Globally increasing energy demands and environmental concerns related to the use of fossil fuels have stimulated extensive research to identify new energy systems and economies that are sustainable, clean, low cost, and environmentally benign. Hydrogen generation from solar-driven water splitting is a promising strategy to store solar energy in chemical bonds. The subsequent combustion of hydrogen in fuel cells produces electric energy, and the only exhaust is water. These two reactions compose an ideal process to provide clean and sustainable energy. In such a process, a hydrogen evolution reaction (HER), an oxygen evolution reaction (OER) during water splitting, and an oxygen reduction reaction (ORR) as a fuel cell cathodic reaction are key steps that affect the efficiency of the overall energy conversion. Catalysts play key roles in this process by improving the kinetics of these reactions. Porphyrin-based and corrole-based systems are versatile and can efficiently catalyze the ORR, OER, and HER. Because of the significance of energy-related small molecule activation, this review covers recent progress in hydrogen evolution, oxygen evolution, and oxygen reduction reactions catalyzed by porphyrins and corroles.

  20. Body-Fitted Detonation Shock Dynamics and the Pseudo-Reaction-Zone Energy Release Model

    Science.gov (United States)

    Meyer, Chad; Quirk, James; Short, Mark; Chqiuete, Carlos

    2016-11-01

    Programmed-burn methods are a class of models used to propagate a detonation wave, without the high resolution cost associated with a direct numerical simulation. They separate the detonation evolution calculation into two components: timing and energy release. The timing component is usually calculated with a Detonation Shock Dynamics model, a surface evolution representation that relates the normal velocity of the surface (Dn) to its local curvature. The energy release component must appropriately capture the degree of energy change associated with chemical reaction while simultaneously remaining synchronized with the timing component. The Pseudo-Reaction-Zone (PRZ) model is a reactive burn like energy release model, converting reactants into products, but with a conversion rate that is a function of the DSD surface Dn field. As such, it requires the DSD calculation produce smooth Dn fields, a challenge in complex geometries. We describe a new body-fitted approach to the Detonation Shock Dynamics calculation which produces the required smooth Dn fields, and a method for calibrating the PRZ model such that the rate of energy release remains as synced as possible with the timing component. We show results for slab, rate-stick and arc geometries.

  1. A Model of Egoistical Relative Deprivation

    Science.gov (United States)

    Crosby, Faye

    1976-01-01

    Examines the theory of relative deprivation. This theory states, basically, that objective and subjective well-being are not isomorphically related, so that sometimes the better-off one is, the worse-off one feels subjectively. After a brief review of work in the area of relative deprivation, a formal model is developed. (Editor/RK)

  2. A three-variable model of deterministic chaos in the Belousov-Zhabotinsky reaction

    Science.gov (United States)

    Györgyi, László; Field, Richard J.

    1992-02-01

    CHAOS is exhibited by a wide variety of systems governed by nonlinear dynamic laws1-3. Its most striking feature is an apparent randomness which seems to contradict its deterministic origin. The best-studied chaotic chemical system is the Belousov-Zhabotinsky (BZ) reaction4-6 in a continuous-flow stirred-tank reactor (CSTR). Here we present a simple mechanism for the BZ reaction which allows us to develop a description in terms of a set of differential equations containing only three variables, the minimum number required to generate chaos in a continuous (non-iterative) dynamical system2. In common with experiments, our model shows aperiodicity and transitions between periodicity and chaos near bifurcations between oscillatory and steady-state behaviour, which occur at both low and high CSTR flow rates. While remaining closely related to a real chaotic chemical system, our model is sufficiently simple to allow detailed mathematical analysis. It also reproduces many other features of the BZ reaction better than does the simple Oregonator7 (which cannot produce chaos).

  3. Multicompartment/CFD modelling of transport and reaction processes in Couette-Taylor photobioreactor

    Directory of Open Access Journals (Sweden)

    Papáček Š.

    2007-11-01

    Full Text Available A hybrid multicompartment/CFD modelling approach, introduced by Bezzo et al. (2003, describing processes with much faster fluid dynamics time-scale than the reaction rate, is used to characterise microalgal growth in a photobioreactor. Our system of interest, the Couette-Taylor bioreactor (CTBR, is divided into a network of wellmixed compartments. Photosynthetic reactions and other related phenomena are described in each compartment by an ordinary differential equation (ODE. The flow of neutrally-buoyant particles, representing a continuous mass flow of microalgal cells inside CTBR, is simulated by a steady-state computational fluid dynamics (CFD computations. The flow rates between adjacent compartments are derived from several thousand predicted trajectories, post-processed using MATLAB, accordingly to our original method. The resulting governing equations are formed as a system of n_c (total number of compartments ODE’s, which are easier to handle than the large system of equations rising from a reaction phenomena incorporated in CFD models.

  4. Nicotiana tabacum as model for ozone - plant surface reactions

    Science.gov (United States)

    Jud, Werner; Fischer, Lukas; Wohlfahrt, Georg; Tissier, Alain; Canaval, Eva; Hansel, Armin

    2015-04-01

    Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. The ensuing injuries have been related to the uptake of ozone through the stomatal pores and oxidative effects damaging the internal leaf tissue. A striking question of current research is the environment and plant specific partitioning of ozone loss between gas phase, stomatal or plant surface sink terms. Here we show results from ozone fumigation experiments using various Nicotiana Tabacum varieties, whose surfaces are covered with different amounts of unsaturated diterpenoids exuded by their glandular trichomes. Exposure to elevated ozone levels (50 to 150 ppbv) for 5 to 15 hours in an exceptionally clean cuvette system did neither result in a reduction of photosynthesis nor caused any visible leaf damage. Both these ozone induced stress effects have been observed previously in ozone fumigation experiments with the ozone sensitive tobacco line Bel-W3. In our case ozone fumigation was accompanied by a continuous release of oxygenated volatile organic compounds, which could be clearly associated to their condensed phase precursors for the first time. Gas phase reactions of ozone were avoided by choosing a high enough gas exchange rate of the plant cuvette system. In the case of the Ambalema variety, that is known to exude only the diterpenoid cis-abienol, ozone fumigation experiments yield the volatiles formaldehyde and methyl vinyl ketone (MVK). The latter could be unequivocally separated from isomeric methacrolein (MACR) by the aid of a Selective Reagent Ion Time-of-Flight Mass Spectrometer (SRI-ToF-MS), which was switched every six minutes from H3O+ to NO+ primary ion mode and vice versa. Consistent with the picture of an ozone protection mechanism caused by reactive diterpenoids at the leaf surface are the results from dark-light experiments. The ozone loss obtained from the

  5. Modelling of reaction cross sections and prompt neutron emission

    Directory of Open Access Journals (Sweden)

    Oberstedt S.

    2010-10-01

    Full Text Available Accurate nuclear data concerning reaction cross sections and the emission of prompt fission neutrons (i.e. multiplicity and spectra as well as other fission fragment data are of great importance for reactor physics design, especially for the new Generation IV nuclear energy systems. During the past years for several actinides (238U(n, f and 237Np(n, f both the reaction cross sections and prompt neutron multiplicities and spectra have been calculated within the frame of the EFNUDAT project.

  6. Anticoagulant-related hospital admissions: serious adverse reactions identified through hospital databases.

    Science.gov (United States)

    Heng, Charles; Rybarczyk-Vigouret, Marie Christine; Michel, Bruno

    2015-02-01

    A growing number of patients today receive anticoagulants. These drugs can cause serious adverse reactions leading to patients' hospitalization. The present study aimed to assess the number of hospital admissions as a result of anticoagulant adverse reactions in Alsace, a French region of 1.8 million inhabitants, and to estimate the economic burden associated with their management. A retrospective analysis was performed using data extracted from the regional and anonymous hospital Programme de Médicalisation des Systèmes d'Information (PMSI) database to assess the number of hospital admissions and the associated costs. Stays from public and private hospitals were extracted from the database using two International Classification of Diseases, 10th revision, codes referring to anticoagulant drugs: 'T45.5-Poisoning by anticoagulants' and 'Y44.2-Anticoagulants' adverse effect in therapeutic use'. Costs were calculated from official French tariffs. Within a 2-year period from 1 Januray 2010 to 31 December 2011, 462 anticoagulant-related hospital admissions, predominantly in elderly patients, were identified in Alsace. These stays, as a result of anticoagulant adverse reactions, represented a cost of 2 050 127.86 euros (including hospitalization and expensive drugs). Regional PMSI database constitutes an effective tool to explore anticoagulant-related hospital admissions. Based on our study, one can state that the cost of anticoagulation therapies lies not only in the price of the drugs but also in the cost of adverse reaction management. Policy makers should be aware of this reality and should focus on better medication supervision in order to improve patient safety and reduce expenses. Copyright © 2014 John Wiley & Sons, Ltd.

  7. Reaction-subdiffusion front propagation in a comblike model of spiny dendrites

    Science.gov (United States)

    Iomin, A.; Méndez, V.

    2013-07-01

    Fractional reaction-diffusion equations are derived by exploiting the geometrical similarities between a comb structure and a spiny dendrite. In the framework of the obtained equations, two scenarios of reaction transport in spiny dendrites are explored, where both a linear reaction in spines and nonlinear Fisher-Kolmogorov-Petrovskii-Piskunov reactions along dendrites are considered. In the framework of fractional subdiffusive comb model, we develop a Hamilton-Jacobi approach to estimate the overall velocity of the reaction front propagation. One of the main effects observed is the failure of the front propagation for both scenarios due to either the reaction inside the spines or the interaction of the reaction with the spines. In the first case the spines are the source of reactions, while in the latter case, the spines are a source of a damping mechanism.

  8. A Macro-Micro-Symbolic Teaching to Promote Relational Understanding of Chemical Reactions

    Science.gov (United States)

    Ziad Jaber, Lama; BouJaoude, Saouma

    2012-05-01

    The purpose of this research is threefold: (1) to identify the difficulties that Grade 10 students in a Lebanese school have that hinder their conceptual understanding at the micro-macro-symbolic interface in chemistry, (2) to investigate the effect of a macro-micro-symbolic teaching approach on students' relational understanding of chemical reactions, and (3) to characterize students' conceptual profiles regarding their understanding of chemical reactions in terms of macro, micro, symbolic levels and the relations among them, at the end of the teaching sequence. Forty six 10th graders from two sections participated in the study. A student-centered approach was followed in both sections based on constructivist pedagogy. Hence the teacher played the role of a facilitator who guided students in a meaning making inductive learning process, through questioning, monitoring, validating, and clarifying ideas. Instruction in the experimental group was characterized by macro-micro-symbolic teaching that focuses on the interplay between the levels, integrates various representations, and engages students in an epistemic discourse about the nature of knowing in chemistry. Data sources for the study included a pre-test and two post-intervention tasks: a post-test and a concept map task, in addition to interviews with selected students from both sections. Findings indicated that macro-micro-symbolic teaching enhanced students' conceptual understanding and relational learning of chemical reactions. Besides, four assertions related to students' conceptual and epistemological thinking in response to the different teaching approaches are presented. Implications for instruction and for teacher education programs, as well as recommendations for further research, are discussed in light of these findings.

  9. Study of n-Butyl Acrylate Self-Initiation Reaction Experimentally and via Macroscopic Mechanistic Modeling

    Directory of Open Access Journals (Sweden)

    Ahmad Arabi Shamsabadi

    2016-04-01

    Full Text Available This paper presents an experimental study of the self-initiation reaction of n-butyl acrylate (n-BA in free-radical polymerization. For the first time, the frequency factor and activation energy of the monomer self-initiation reaction are estimated from measurements of n-BA conversion in free-radical homo-polymerization initiated only by the monomer. The estimation was carried out using a macroscopic mechanistic mathematical model of the reactor. In addition to already-known reactions that contribute to the polymerization, the model considers a n-BA self-initiation reaction mechanism that is based on our previous electronic-level first-principles theoretical study of the self-initiation reaction. Reaction rate equations are derived using the method of moments. The reaction-rate parameter estimates obtained from conversion measurements agree well with estimates obtained via our purely-theoretical quantum chemical calculations.

  10. Methods of modelling relative growth rate

    Institute of Scientific and Technical Information of China (English)

    Arne Pommerening; Anders Muszta

    2015-01-01

    Background:Analysing and modelling plant growth is an important interdisciplinary field of plant science. The use of relative growth rates, involving the analysis of plant growth relative to plant size, has more or less independently emerged in different research groups and at different times and has provided powerful tools for assessing the growth performance and growth efficiency of plants and plant populations. In this paper, we explore how these isolated methods can be combined to form a consistent methodology for modelling relative growth rates. Methods:We review and combine existing methods of analysing and modelling relative growth rates and apply a combination of methods to Sitka spruce (Picea sitchensis (Bong.) Carr.) stem-analysis data from North Wales (UK) and British Douglas fir (Pseudotsuga menziesi (Mirb.) Franco) yield table data. Results:The results indicate that, by combining the approaches of different plant-growth analysis laboratories and using them simultaneously, we can advance and standardise the concept of relative plant growth. Particularly the growth multiplier plays an important role in modelling relative growth rates. Another useful technique has been the recent introduction of size-standardised relative growth rates. Conclusions:Modelling relative growth rates mainly serves two purposes, 1) an improved analysis of growth performance and efficiency and 2) the prediction of future or past growth rates. This makes the concept of relative growth ideally suited to growth reconstruction as required in dendrochronology, climate change and forest decline research and for interdisciplinary research projects beyond the realm of plant science.

  11. Methods of modelling relative growth rate

    Directory of Open Access Journals (Sweden)

    Arne Pommerening

    2015-03-01

    Full Text Available Background Analysing and modelling plant growth is an important interdisciplinary field of plant science. The use of relative growth rates, involving the analysis of plant growth relative to plant size, has more or less independently emerged in different research groups and at different times and has provided powerful tools for assessing the growth performance and growth efficiency of plants and plant populations. In this paper, we explore how these isolated methods can be combined to form a consistent methodology for modelling relative growth rates. Methods We review and combine existing methods of analysing and modelling relative growth rates and apply a combination of methods to Sitka spruce (Picea sitchensis (Bong. Carr. stem-analysis data from North Wales (UK and British Douglas fir (Pseudotsuga menziesii (Mirb. Franco yield table data. Results The results indicate that, by combining the approaches of different plant-growth analysis laboratories and using them simultaneously, we can advance and standardise the concept of relative plant growth. Particularly the growth multiplier plays an important role in modelling relative growth rates. Another useful technique has been the recent introduction of size-standardised relative growth rates. Conclusions Modelling relative growth rates mainly serves two purposes, 1 an improved analysis of growth performance and efficiency and 2 the prediction of future or past growth rates. This makes the concept of relative growth ideally suited to growth reconstruction as required in dendrochronology, climate change and forest decline research and for interdisciplinary research projects beyond the realm of plant science.

  12. Modeling subsurface contaminant reactions and transport at the watershed scale

    Energy Technology Data Exchange (ETDEWEB)

    Gwo, J.P.; Jardine, P.M.; D`Azevedo, E.F. [Oak Ridge National Lab., TN (United States); Wilson, G.V. [Desert Research Inst., Las Vegas, NV (United States). Water Resources Center

    1997-12-01

    The objectives of this research are: (1) to numerically examine the multiscale effects of physical and chemical mass transfer processes on watershed scale, variably saturated subsurface contaminant transport, and (2) to conduct numerical simulations on watershed scale reactive solute transport and evaluate their implications to uncertainty characterization and cost benefit analysis. Concurrent physical and chemical nonequilibrium caused by inter aggregate gradients of pressure head and solute concentration and intra-aggregate geochemical and microbiological processes, respectively, may arise at various scales and flowpaths. To this date, experimental investigations of these complex processes at watershed scale remain a challenge and numerical studies are often needed for guidance of water resources management and decision making. This research integrates the knowledge bases developed during previous experimental and numerical investigations at a proposed waste disposal site at the Oak Ridge National Laboratory to study the concurrent effects of physical and chemical nonequilibrium. Comparison of numerical results with field data indicates that: (1) multiregion, preferential flow and solute transport exist under partially saturated condition and can be confirmed theoretically, and that (2) mass transfer between pore regions is an important process influencing contaminant movement in the subsurface. Simulations of watershed scale, multi species reactive solute transport suggest that dominance of geochemistry and hydrodynamics may occur simultaneously at different locales and influence the movement of one species relative to another. Execution times on the simulations of the reactive solute transport model also indicate that the model is ready to assist the selection of important parameters for site characterization.

  13. MODEL STUDIES OF MODE-SPECIFICITY IN UNIMOLECULAR REACTION DYNAMICS

    Energy Technology Data Exchange (ETDEWEB)

    Waite, Boyd A.; Miller, William H.

    1980-06-01

    Essentially exact quantum mechanical calculations are carried out to determine the energies and lifetimes of the quasi-bound states for a system of two (non~linearly) coupled oscillators (one of which is harmonic, the other being able to dissociate). For weak coupling the system displays mode-specificity, i.e., the unimolecular rate constants are not a monotonic function of the total energy, but increased coupling and frequency degeneracy tends to destroy mode-specificity. A somewhat surprising result is that for a given coupling the degree of modespecificity is roughly independent of the energy, in marked contrast to the fact that there is an energetic threshold for the onset of "stochastic trajectories" of the corresponding classical system; i.e., there seems to be no relation between statistical/mode-specific behavior of the unimolecular rate constants and stochastic/regular classical trajectories. In order to be able to treat more physically relevant models--i.e., those with more than two degrees of freedom--a semiclassical model is constructed and seen to be able to reproduce the accurate quantum mechanical rates reasonably well.

  14. Modeling subsurface contaminant reactions and transport at the watershed scale

    Energy Technology Data Exchange (ETDEWEB)

    Gwo, J.P.; Jardine, P.M.; D`Azevedo, E.F. [Oak Ridge National Lab., TN (United States); Wilson, G.V. [Desert Research Inst., Las Vegas, NV (United States). Water Resources Center

    1997-12-01

    The objectives of this research are: (1) to numerically examine the multiscale effects of physical and chemical mass transfer processes on watershed scale, variably saturated subsurface contaminant transport, and (2) to conduct numerical simulations on watershed scale reactive solute transport and evaluate their implications to uncertainty characterization and cost benefit analysis. Concurrent physical and chemical nonequilibrium caused by inter aggregate gradients of pressure head and solute concentration and intra-aggregate geochemical and microbiological processes, respectively, may arise at various scales and flowpaths. To this date, experimental investigations of these complex processes at watershed scale remain a challenge and numerical studies are often needed for guidance of water resources management and decision making. This research integrates the knowledge bases developed during previous experimental and numerical investigations at a proposed waste disposal site at the Oak Ridge National Laboratory to study the concurrent effects of physical and chemical nonequilibrium. Comparison of numerical results with field data indicates that: (1) multiregion, preferential flow and solute transport exist under partially saturated condition and can be confirmed theoretically, and that (2) mass transfer between pore regions is an important process influencing contaminant movement in the subsurface. Simulations of watershed scale, multi species reactive solute transport suggest that dominance of geochemistry and hydrodynamics may occur simultaneously at different locales and influence the movement of one species relative to another. Execution times on the simulations of the reactive solute transport model also indicate that the model is ready to assist the selection of important parameters for site characterization.

  15. A Note on a Nonlocal Nonlinear Reaction-Diffusion Model

    OpenAIRE

    Walker, Christoph

    2011-01-01

    We give an application of the Crandall-Rabinowitz theorem on local bifurcation to a system of nonlinear parabolic equations with nonlocal reaction and cross-diffusion terms as well as nonlocal initial conditions. The system arises as steady-state equations of two interacting age-structured populations.

  16. Competitive reaction- and feedback effects based on VARX models of pooled store data

    NARCIS (Netherlands)

    Horvath, C; Leeflang, PSH; Wieringa, JE; Wittink, DR

    2005-01-01

    We apply a model that accommodates dynamic phenomena in demand- and reaction functions. The latter functions capture reactions to actions as well as to consequences of actions. We estimate a fixed effects VARX model with dynamic and interactive effects for multiple brands based on pooled time series

  17. Spreading Speed for a Periodic Reaction-diffusion Model with Nonmonotone Birth Function

    Institute of Scientific and Technical Information of China (English)

    HUANG Ye-hui; WENG Pei-xuan

    2012-01-01

    A reaction-diffusion model for a single spccies with age structure and nonlocal reaction for periodic time t is derived.Some results about the model with monotone birth function are firstly introduced,and then by constructing two auxiliary equations and squeezing method,the spreading speed for the system with nonmonotone birth function is obtained.

  18. A new mathematical model to simulate AVA cold-induced vasodilation reaction to local cooling

    Science.gov (United States)

    Rida, Mohamad; Karaki, Wafaa; Ghaddar, Nesreen; Ghali, Kamel; Hoballah, Jamal

    2014-01-01

    The purpose of this work was to integrate a new mathematical model with a bioheat model, based on physiology and first principles, to predict thermoregulatory arterio-venous anastomoses (AVA) and cold-induced vasodilation (CIVD) reaction to local cooling. The transient energy balance equations of body segments constrained by thermoregulatory controls were solved numerically to predict segmental core and skin temperatures, and arterial blood flow for given metabolic rate and environmental conditions. Two similar AVA-CIVD mechanisms were incorporated. The first was activated during drop in local skin temperature (hand immersions in cold fluid. When compared with published data, the model predicted accurately the onset time of CIVD at 25 min and T CIVD,min at 10 °C for hand exposure to still air at 0 °C. Good agreement was also obtained between predicted finger skin temperature and experimentally published values for repeated immersion in cold water at environmental conditions of 30, 25, and 20 °C. The CIVD thermal response was found related to core body temperature, finger skin temperature, and initial finger sensible heat loss rate upon exposure to cold fluid. The model captured central and local stimulations of the CIVD and accommodated observed variability reported in literature of onset time of CIVD reaction and T CIVD,min.

  19. The Fixed-Links Model in Combination with the Polynomial Function as a Tool for Investigating Choice Reaction Time Data

    Science.gov (United States)

    Schweizer, Karl

    2006-01-01

    A model with fixed relations between manifest and latent variables is presented for investigating choice reaction time data. The numbers for fixation originate from the polynomial function. Two options are considered: the component-based (1 latent variable for each component of the polynomial function) and composite-based options (1 latent…

  20. Becoming the denigrated other: Group relations perspectives on initial reactions to a bipolar disorder diagnosis

    Directory of Open Access Journals (Sweden)

    Susan G. Goldberg

    2012-09-01

    Full Text Available The initial reactions to a bipolar disorder diagnosis of research participants in a small, qualitative study consisted of astonishment, dread of being mad, and extremely negative associations. All had prior mental health diagnoses, including episodes of severe depression (all but one and alcoholism (one. All participants reported mental health histories prediagnosis and most had spent years contending with mental health labels, medications, symptoms, and hospitalizations. In addition, most participants were highly educated health professionals, quite familiar with the behaviors that the medical system considered to comprise bipolar disorder. Their negative associations to the initial bipolar disorder diagnosis, therefore, appeared inconsistent with their mental health histories and professional knowledge. This article contextualizes these initial reactions of shock and distress and proposes interpretations of these findings from societal and psychodynamic group relations perspectives. The participants’ initial negative reactions are conceptualized as involving the terror of being transported from the group of normal people into the group of mad or crazy people, i.e., people with mental illnesses, who may constitute a societal denigrated other.

  1. Valproate-related erythrodermia with reversible encephalopathy: a rare but serious adverse reaction, case report.

    Science.gov (United States)

    Rener-Primec, Zvonka; Balkovec, Valerija

    2014-01-01

    Cutaneous adverse reactions to antiepileptic drugs (AEDs) are usually easily recognized in daily clinical practice when they manifest as a morbilliform or maculopapular rash within the first few weeks after introducing an AED. Valproate (VPA)-induced encephalopathy is a rare but serious complication, presenting with impaired consciousness, with or without hyperammonemia, normal liver enzymes, and normal serum level of VPA. A 2-year-old Caucasian boy with severe developmental disability and pharmacoresistant epilepsy presented with fever, generalized erythrodermia, and encephalopathy, which resolved after discontinuation of valproate. Sodium valproate (30 mg/kg/day) was introduced 5 months previously, as the third drug in combination with vigabatrin and levetiracetam, due to frequent daily seizures. The clinical condition of generalized erythrodermia and encephalopathy was recognized by the treating physician as a possible adverse reaction to VPA: with the Naranjo scale it was probably associated with VPA (six points) and possibly associated with vigabatrin and levetiracetam (three and two points, respectively). After valproate withdrawal, the patient recovered completely. This case is of interest because erythrodermia was a clue to the recognition of valproate-related adverse reaction with severe central nervous system involvement without hyperammonemia and with normal liver enzymes--a very rare occurrence.

  2. Bias Modeling for Distantly Supervised Relation Extraction

    Directory of Open Access Journals (Sweden)

    Yang Xiang

    2015-01-01

    Full Text Available Distant supervision (DS automatically annotates free text with relation mentions from existing knowledge bases (KBs, providing a way to alleviate the problem of insufficient training data for relation extraction in natural language processing (NLP. However, the heuristic annotation process does not guarantee the correctness of the generated labels, promoting a hot research issue on how to efficiently make use of the noisy training data. In this paper, we model two types of biases to reduce noise: (1 bias-dist to model the relative distance between points (instances and classes (relation centers; (2 bias-reward to model the possibility of each heuristically generated label being incorrect. Based on the biases, we propose three noise tolerant models: MIML-dist, MIML-dist-classify, and MIML-reward, building on top of a state-of-the-art distantly supervised learning algorithm. Experimental evaluations compared with three landmark methods on the KBP dataset validate the effectiveness of the proposed methods.

  3. Relating structure and dynamics in organisation models

    NARCIS (Netherlands)

    Jonkers, C.M.; Treur, J.

    To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems,

  4. Negative reactions of men to the loss of power in gender relations: Lilith vs. Eve

    OpenAIRE

    Miguel Moya; Francisca Expósito; M. Carmen Herrera

    2012-01-01

    This paper examines the reaction of the man when he sees he is losing power and authority over a woman and it relation with men’s sexist ideology. 83 men participated in the study and were led to believe they were interacting via computer with a woman, and answered a decision-making task about family relationships. All of them were assigned the role of someone with authority and power. In half the cases, the woman accepted the man's decisions, and, in the other half, she did not accept. The r...

  5. The direct oxidative diene cyclization and related reactions in natural product synthesis

    Directory of Open Access Journals (Sweden)

    Juliane Adrian

    2016-09-01

    Full Text Available The direct oxidative cyclization of 1,5-dienes is a valuable synthetic method for the (diastereoselective preparation of substituted tetrahydrofurans. Closely related reactions start from 5,6-dihydroxy or 5-hydroxyalkenes to generate similar products in a mechanistically analogous manner. After a brief overview on the history of this group of transformations and a survey on mechanistic and stereochemical aspects, this review article provides a summary on applications in natural product synthesis. Moreover, current limitations and future directions in this area of chemistry are discussed.

  6. Accurate eikonal-curvature relation for wave fronts in locally anisotropic reaction-diffusion systems.

    Science.gov (United States)

    Dierckx, Hans; Bernus, Olivier; Verschelde, Henri

    2011-09-02

    The dependency of wave velocity in reaction-diffusion (RD) systems on the local front curvature determines not only the stability of wave propagation, but also the fundamental properties of other spatial configurations such as vortices. This Letter gives the first derivation of a covariant eikonal-curvature relation applicable to general RD systems with spatially varying anisotropic diffusion properties, such as cardiac tissue. The theoretical prediction that waves which seem planar can nevertheless possess a nonvanishing geometrical curvature induced by local anisotropy is confirmed by numerical simulations, which reveal deviations up to 20% from the nominal plane wave speed.

  7. Work-related post-traumatic stress reactions: the hidden dimension

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, B.Z.

    A variety of occupational health hazards can cause employees to experience feelings of victimization and to develop work-related post-traumatic stress responses. The author presents assessment guidelines developed in work with people suffering from toxic exposures to help identify factors that can place employees at high risk for such stress responses. These guidelines can be adapted to evaluate employee reactions to any type of occupational injury. Clinicians also need to move beyond individual treatment approaches to address workplace and policy interventions.

  8. Delineating pMDI model reactions with loblolly pine via solution-state NMR spectroscopy. Part 1, Catalyzed reactions with wood models and wood polymers

    Science.gov (United States)

    Daniel J. Yelle; John Ralph; Charles R. Frihart

    2011-01-01

    To better understand adhesive interactions with wood, reactions between model compounds of wood and a model compound of polymeric methylene diphenyl diisocyanate (pMDI) were characterized by solution-state NMR spectroscopy. For comparison, finely ground loblolly pine sapwood, milled-wood lignin and holocellulose from the same wood were isolated and derivatized with...

  9. Kinetic modeling for thermal dehydration of ferrous oxalate dihydrate polymorphs: a combined model for induction period-surface reaction-phase boundary reaction.

    Science.gov (United States)

    Ogasawara, Haruka; Koga, Nobuyoshi

    2014-04-03

    In this study, ferrous oxalate dihydrate polymorph particles, α- and β-phases, with square bipyramidal and quadratic prismatic shapes, respectively, were synthesized. Thermal dehydration of the samples was subjected to kinetic study as a typical reaction that indicates a significant induction period and a sigmoidal mass-loss behavior. On the basis of the formal kinetic analysis of the mass-loss traces recorded under isothermal, nonisothermal, and constant transformation rate conditions and the morphological observations of the surface textures of the partially reacted sample particles, a combined kinetic model for the induction period-surface reaction-phase boundary reaction was developed. The sigmoidal mass-loss behavior after the significant induction period under isothermal conditions was satisfactorily simulated by the combined kinetic model. The kinetic parameters for the component processes of induction period, surface reaction, and phase boundary reaction were separately determined from the kinetic simulation. The differences in the kinetic behaviors of the induction period and the phase boundary reaction between α- and β-phase samples were well described by the kinetic parameters. The applicability of the combined kinetic model to practical systems was demonstrated through characterizing the physicogeometrical kinetics of the thermal dehydration of ferrous oxalate dihydrate polymorphs.

  10. Modeling of Chemical Reactions in Afterburning for the Reduction of N2O

    DEFF Research Database (Denmark)

    Gustavsson, Lennart; Glarborg, Peter; Leckner, Bo

    1996-01-01

    Full scale tests in a 12 MW fluidized bed combustor on reduction of N2O by secondary fuel injection are analyzed in terms a model that involves a detailed reaction mechanism for the gas phase chemistry as well as a description of gas-solid reactions.......Full scale tests in a 12 MW fluidized bed combustor on reduction of N2O by secondary fuel injection are analyzed in terms a model that involves a detailed reaction mechanism for the gas phase chemistry as well as a description of gas-solid reactions....

  11. Thermodynamic Data for Geochemical Modeling of Carbonate Reactions Associated with CO2 Sequestration – Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, Kenneth M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McGrail, B. Peter [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2010-09-01

    Permanent storage of anthropogenic CO2 in deep geologic formations is being considered as a means to reduce the concentration of atmospheric CO2 and thus its contribution to global climate change. To ensure safe and effective geologic sequestration, numerous studies have been completed of the extent to which the CO2 migrates within geologic formations and what physical and geochemical changes occur in these formations when CO2 is injected. Sophisticated, computerized reservoir simulations are used as part of field site and laboratory CO2 sequestration studies. These simulations use coupled multiphase flow-reactive chemical transport models and/or standalone (i.e., no coupled fluid transport) geochemical models to calculate gas solubility, aqueous complexation, reduction/oxidation (redox), and/or mineral solubility reactions related to CO2 injection and sequestration. Thermodynamic data are critical inputs to modeling geochemical processes. The adequacy of thermodynamic data for carbonate compounds has been identified as an important data requirement for the successful application of these geochemical reaction models to CO2 sequestration. A review of thermodynamic data for CO2 gas and carbonate aqueous species and minerals present in published data compilations and databases used in geochemical reaction models was therefore completed. Published studies that describe mineralogical analyses from CO2 sequestration field and natural analogue sites and laboratory studies were also reviewed to identify specific carbonate minerals that are important to CO2 sequestration reactions and therefore require thermodynamic data. The results of the literature review indicated that an extensive thermodynamic database exists for CO2 and CH4 gases, carbonate aqueous species, and carbonate minerals. Values of ΔfG298° and/or log Kr,298° are available for essentially all of these compounds. However, log Kr,T° or heat capacity values at temperatures above 298 K exist for less than

  12. Relating business modelling and enterprise architecture

    NARCIS (Netherlands)

    Meertens, Lucas Onno

    2013-01-01

    This thesis proposes a methodology for creating business models, evaluating them, and relating them to enterprise architecture. The methodology consists of several steps, leading from an organization’s current situation to a target situation, via business models and enterprise architecture. Current

  13. Models and relations in economics and econometrics

    DEFF Research Database (Denmark)

    Juselius, Katarina

    1999-01-01

    Based on a money market analysis using the cointegrated VAR model the paper demonstrates some possible pitfalls in macroeconomic inference as a direct consequence of inadequate stochastic model formulation. A number of questions related to concepts such as empirical and theoretical steady-states,...

  14. Relating business modelling and enterprise architecture

    NARCIS (Netherlands)

    Meertens, Lucas Onno

    2013-01-01

    This thesis proposes a methodology for creating business models, evaluating them, and relating them to enterprise architecture. The methodology consists of several steps, leading from an organization’s current situation to a target situation, via business models and enterprise architecture.

  15. Random incidence absorption coefficients of porous absorbers based on local and extended reaction models

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2011-01-01

    Room surfaces have been extensively modeled as locally reacting in room acoustic predictions although such modeling could yield significant errors under certain conditions. Therefore, this study aims to propose a guideline for adopting the local reaction assumption by comparing predicted random...... incidence acoustical characteristics of typical building elements made of porous materials assuming extended and local reaction. For each surface reaction, five well-established wave propagation models, the Delany-Bazley, Miki, Beranek, Allard-Champoux, and Biot model, are employed. Effects of the flow...

  16. The generic model of General Relativity

    Energy Technology Data Exchange (ETDEWEB)

    Tsamparlis, Michael, E-mail: mtsampa@phys.uoa.g [Department of Physics, Section Astrophysics Astronomy Mechanics, University of Athens, University of Athens, Zografos 15783, Athens (Greece)

    2009-10-01

    We develop a generic spacetime model in General Relativity from which all existing model results are produced under specific assumptions, depending on the case. We classify each type of possible assumption, especially the role of observers and that of symmetries, and discuss their role in the development of a model. We apply the results in a step by step approach to the case of a Bianchi I spacetime and a string fluid.

  17. Consumers’ Health-Related Motive Orientations and Reactions to Claims about Dietary Calcium

    Science.gov (United States)

    Hoefkens, Christine; Verbeke, Wim

    2013-01-01

    Health claims may contribute to better informed and healthier food choices and to improved industrial competitiveness by marketing foods that support healthier lifestyles in line with consumer preferences. With the more stringent European Union regulation of nutrition and health claims, insights into consumers’ health-related goal patterns and their reactions towards such claims are needed to influence the content of lawful claims. This study investigated how consumers’ explicit and implicit health-related motive orientations (HRMOs) together with the type of calcium-claim (nutrition claim, health claim and reduction of disease risk claim) influence perceived credibility and purchasing intention of calcium-enriched fruit juice. Data were collected in April 2006 through a consumer survey with 341 Belgian adults. The findings indicate that stronger implicit HRMOs (i.e., indirect benefits of calcium for personal health) are associated with higher perceived credibility, which is not (yet) translated into a higher purchasing intention. Consumers’ explicit HRMOs, which refer to direct benefits or physiological functions of calcium in the body—as legally permitted in current calcium-claims in the EU—do not associate with reactions to the claims. Independently of consumers’ HRMOs, the claim type significantly affects the perceived credibility and purchasing intention of the product. Implications for nutrition policy makers and food industries are discussed. PMID:23306190

  18. Consumers’ Health-Related Motive Orientations and Reactions to Claims about Dietary Calcium

    Directory of Open Access Journals (Sweden)

    Christine Hoefkens

    2013-01-01

    Full Text Available Health claims may contribute to better informed and healthier food choices and to improved industrial competitiveness by marketing foods that support healthier lifestyles in line with consumer preferences. With the more stringent European Union regulation of nutrition and health claims, insights into consumers’ health-related goal patterns and their reactions towards such claims are needed to influence the content of lawful claims. This study investigated how consumers’ explicit and implicit health-related motive orientations (HRMOs together with the type of calcium-claim (nutrition claim, health claim and reduction of disease risk claim influence perceived credibility and purchasing intention of calcium-enriched fruit juice. Data were collected in April 2006 through a consumer survey with 341 Belgian adults. The findings indicate that stronger implicit HRMOs (i.e., indirect benefits of calcium for personal health are associated with higher perceived credibility, which is not (yet translated into a higher purchasing intention. Consumers’ explicit HRMOs, which refer to direct benefits or physiological functions of calcium in the body — as legally permitted in current calcium-claims in the EU — do not associate with reactions to the claims. Independently of consumers’ HRMOs, the claim type significantly affects the perceived credibility and purchasing intention of the product. Implications for nutrition policy makers and food industries are discussed.

  19. Relative effectiveness of pretreatments on performance of Rhizomucor miehei lipase in nonpolar reaction media.

    Science.gov (United States)

    Garcia, Rafael A; Riley, Mark R

    2005-02-01

    Enzymes can be used in nonpolar reaction media to modify water-insoluble substrates. A variety of pretreatments, applied to the enzyme prior to introduction to the nonpolar media, can improve enzyme activity. However, the various pretreatments have not been studied using directly comparable conditions, nor have they been applied simultaneously to test for interactive effects. This work evaluates pretreatment of lipase with various classes of additives. The pretreated lipase is used to catalyze esterification between citronellol and acetic acid in a medium of n-hexane. The effectiveness of a particular pretreatment is presented in terms of relative performance (RP), which is equal to the number of times faster the pretreated lipase catalyzes the reaction relative to untreated lipase. The individual and interactive effects of the pretreatment factors were studied and compared. Buffer salts had a much stronger performance-enhancing effect than nonbuffer salts; pretreatment with 90% (w/w) sodium phosphate yielded lipase with an RP of approx 64. A strong interaction was found between the treatments with sodium phosphate and pH adjustment. These treatments may mitigate the inhibitory effect of acetic acid. Activating effects of phase interfaces and active-site protectants are shown to be complementary to other treatments, demonstrating that they likely act by distinct mechanisms.

  20. SurfKin: an ab initio kinetic code for modeling surface reactions.

    Science.gov (United States)

    Le, Thong Nguyen-Minh; Liu, Bin; Huynh, Lam K

    2014-10-05

    In this article, we describe a C/C++ program called SurfKin (Surface Kinetics) to construct microkinetic mechanisms for modeling gas-surface reactions. Thermodynamic properties of reaction species are estimated based on density functional theory calculations and statistical mechanics. Rate constants for elementary steps (including adsorption, desorption, and chemical reactions on surfaces) are calculated using the classical collision theory and transition state theory. Methane decomposition and water-gas shift reaction on Ni(111) surface were chosen as test cases to validate the code implementations. The good agreement with literature data suggests this is a powerful tool to facilitate the analysis of complex reactions on surfaces, and thus it helps to effectively construct detailed microkinetic mechanisms for such surface reactions. SurfKin also opens a possibility for designing nanoscale model catalysts.

  1. Structural Equation Modeling Applied to the Reaction to Stock Dividends and Stock Splits: integrating signaling, liquidity and optimal price level

    Directory of Open Access Journals (Sweden)

    Kelmara Mendes Vieira

    2011-03-01

    Full Text Available This work develops a hybrid model of structural equations able to take simultaneously the hypotheses of signaling, liquidity, and optimal price level to explain the reaction to the stock dividends and stock splits. In the measurement model four constructs were defined: trading activity, spread, size, and price. The structural model defines extant relations from the proposition of 22 sub-hypotheses. A sample of 321 splits performed in the Brazilian market between 1990 and 2004 was used for assessing the model. Confirmatory factor analysis revealed the validity and coherence of the four constructs. The structural model confirmed 9 original sub-hypotheses.

  2. A Gibbs Energy Minimization Approach for Modeling of Chemical Reactions in a Basic Oxygen Furnace

    Science.gov (United States)

    Kruskopf, Ari; Visuri, Ville-Valtteri

    2017-08-01

    In modern steelmaking, the decarburization of hot metal is converted into steel primarily in converter processes, such as the basic oxygen furnace. The objective of this work was to develop a new mathematical model for top blown steel converter, which accounts for the complex reaction equilibria in the impact zone, also known as the hot spot, as well as the associated mass and heat transport. An in-house computer code of the model has been developed in Matlab. The main assumption of the model is that all reactions take place in a specified reaction zone. The mass transfer between the reaction volume, bulk slag, and metal determine the reaction rates for the species. The thermodynamic equilibrium is calculated using the partitioning of Gibbs energy (PGE) method. The activity model for the liquid metal is the unified interaction parameter model and for the liquid slag the modified quasichemical model (MQM). The MQM was validated by calculating iso-activity lines for the liquid slag components. The PGE method together with the MQM was validated by calculating liquidus lines for solid components. The results were compared with measurements from literature. The full chemical reaction model was validated by comparing the metal and slag compositions to measurements from industrial scale converter. The predictions were found to be in good agreement with the measured values. Furthermore, the accuracy of the model was found to compare favorably with the models proposed in the literature. The real-time capability of the proposed model was confirmed in test calculations.

  3. Reactions of Trimethylaluminium: Modelling the Chemical Degradation of Synthetic Lubricants.

    Science.gov (United States)

    Slaughter, Jonathan; Peel, Andrew J; Wheatley, Andrew E H

    2017-01-01

    In investigating and seeking to mimic the reactivity of trimethylaluminium (TMA) with synthetic, ester-based lubricating oils, the reaction of methyl propionate 1 was explored with 1, 2 and 3 equivalents of the organoaluminium reagent. Spectroscopic analysis points to the formation of the adduct 1(TMA) accompanied only by the low level 1:1 production of Me2 AlOCEtMe2 2 and Me2 AlOMe 3 when an equimolar amount of TMA is applied. The deployment of excess TMA favours reaction to give 2 and 3 over 1(TMA) adduct formation and spectroscopy reveals that in hydrocarbon solution substitution product 2 traps unreacted TMA to yield 2(TMA). The (1) H NMR spectroscopic observation of two Al-Me signals not attributable to free TMA and in the ratio 1:4 suggests the formation of a previously only postulated, symmetrical metallacycle in Me4 Al2 (μ(2) -Me)(μ(2) -OCEtMe2 ). In the presence of 3, 2(TMA) undergoes thermally induced exchange to yield Me4 Al2 (μ(2) -OMe)(μ(2) -OCEtMe2 ) 4 and TMA. The reaction of methyl phenylacetate 5 with TMA allows isolation of the crystalline product Me2 AlOCBnMe2 (TMA) 6(TMA), which allows the first observation of the Me4 Al2 (μ(2) -Me)(μ(2) -OR) motif in the solid state. Distances of 2.133(3) Å (Al-Mebridging ) and 1.951 Å (mean Al-Meterminal ) are recorded. The abstraction of TMA from 6(TMA) by the introduction of Et2 O has yielded 6, which exists as a dimer.

  4. Reactions to Discrimination, Stigmatization, Ostracism, and Other Forms of Interpersonal Rejection: A Multimotive Model

    OpenAIRE

    Richman, Laura Smart; Leary, Mark R.

    2009-01-01

    This article describes a new model that provides a framework for understanding people’s reactions to threats to social acceptance and belonging as they occur in the context of diverse phenomena such as rejection, discrimination, ostracism, betrayal, and stigmatization. People’s immediate reactions are quite similar across different forms of rejection in terms of negative affect and lowered self-esteem. However, following these immediate responses, people’s reactions are influenced by construa...

  5. Molecular Simulations of RNA 2’-O-Transesterification Reaction Models in Solution

    OpenAIRE

    Radak, Brian K.; Harris, Michael E.; York, Darrin M.

    2012-01-01

    We employ quantum mechanical/molecular mechanical umbrella sampling simulations to probe the free energy surfaces of a series of increasingly complex reaction models of RNA 2’-O-transesterification in aqueous solution under alkaline conditions. Such models are valuable for understanding the uncatalyzed processes underlying catalytic cleavage of the phosphodiester backbone of RNA, a reaction of fundamental importance in biology. The chemically reactive atoms are modeled by the AM1/d-PhoT quant...

  6. Stability of Posttraumatic Stress Reaction Factors and Their Relation to General Mental Health Problems in Children: A Longitudinal Study

    Science.gov (United States)

    Nygaard, Egil; Jensen, Tine K.; Dyb, Grete

    2012-01-01

    The aim of this study was to evaluate the structure of posttraumatic stress reaction factors and their relation to general mental health problems in Norwegian children exposed to the tsunami on December 26, 2004. A total of 133 children and adolescents (ages 6-17) were interviewed 10 months posttsunami using the UCLA PTSD Reaction Index, and 104…

  7. Modelling and simulation of a direct ethanol fuel cell considering multistep electrochemical reactions, transport processes and mixed potentials

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Marco [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Melke, Julia, E-mail: julia.melke@gmail.co [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Gerteisen, Dietmar [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany)

    2011-04-15

    Highlights: A DEFC model considering the mixed potential formation at cathode and anode. The low cell voltage at open circuit is due to the parasitic reaction of ethanol and oxygen. Under load, only the parasitic oxidation of ethanol is significant. Inhibiting the parasitic reactions can approximately double the current density. - Abstract: In this work a one-dimensional mathematical model of a direct ethanol fuel cell (DEFC) is presented. The electrochemical oxidation of ethanol in the catalyst layers is described by several reaction steps leading to surface coverage with adsorbed intermediates (CH{sub 3}CO, CO, CH{sub 3} and OH) and to the final products acetaldehyde, acetic acid and CO{sub 2}. A bifunctional reaction mechanism is assumed for the activation of water on a binary catalyst favouring the further oxidation of adsorbates blocking active catalyst sites. The chemical reactions are highly coupled with the charge and reactant transport. The model accounts for crossover of the reactants through the membrane leading to the phenomenon of cathode and anode mixed potentials due to the parasitic oxidation and reduction of ethanol and oxygen, respectively. Polarisation curves of a DEFC were recorded for various ethanol feed concentrations and were used as reference data for the simulation. Based on one set of model parameters the characteristic of electronic and protonic potential, the relative surface coverage and the parasitic current densities in the catalyst layers were studied.

  8. Modelling combustion reactions for gas flaring and its resulting emissions

    Directory of Open Access Journals (Sweden)

    O. Saheed Ismail

    2016-07-01

    Full Text Available Flaring of associated petroleum gas is an age long environmental concern which remains unabated. Flaring of gas maybe a very efficient combustion process especially steam/air assisted flare and more economical than utilization in some oil fields. However, it has serious implications for the environment. This study considered different reaction types and operating conditions for gas flaring. Six combustion equations were generated using the mass balance concept with varying air and combustion efficiency. These equations were coded with a computer program using 12 natural gas samples of different chemical composition and origin to predict the pattern of emission species from gas flaring. The effect of key parameters on the emission output is also shown. CO2, CO, NO, NO2 and SO2 are the anticipated non-hydrocarbon emissions of environmental concern. Results show that the quantity and pattern of these chemical species depended on percentage excess/deficiency of stoichiometric air, natural gas type, reaction type, carbon mass content, impurities, combustion efficiency of the flare system etc. These emissions degrade the environment and human life, so knowing the emission types, pattern and flaring conditions that this study predicts is of paramount importance to governments, environmental agencies and the oil and gas industry.

  9. A relativistic toy model for back-reaction

    CERN Document Server

    Plunien, G; Schützhold, R; Ruser, Marcus; Sch\\"utzhold, Ralf

    2004-01-01

    We consider a quantized massless and minimally coupled scalar field on a circular closed string with a time-dependent radius $R(t)$, whose undisturbed dynamics is governed by the Nambu-Goto action. Within the semi-classical treatment, the back-reaction of the quantum field onto the string dynamics is taken into account in terms of the renormalized expectation value of the energy-momentum tensor including the trace anomaly. The results indicate that the back-reaction could prevent the collapse of the circle $R\\downarrow0$ -- however, the semi-classical picture fails to describe the string dynamics at the turning point (i.e., possible bounce) at finite values of $R$ and $\\dot R$. The fate of the closed string after that point (e.g., oscillation or eternal acceleration) cannot be determined within the semi-classical picture and thus probably requires the full quantum treatment. PACS: 04.62.+v, 03.70.+k, 11.15.Kc, 04.60.-m.

  10. Structure-reactivity modeling using mixture-based representation of chemical reactions

    Science.gov (United States)

    Polishchuk, Pavel; Madzhidov, Timur; Gimadiev, Timur; Bodrov, Andrey; Nugmanov, Ramil; Varnek, Alexandre

    2017-07-01

    We describe a novel approach of reaction representation as a combination of two mixtures: a mixture of reactants and a mixture of products. In turn, each mixture can be encoded using an earlier reported approach involving simplex descriptors (SiRMS). The feature vector representing these two mixtures results from either concatenated product and reactant descriptors or the difference between descriptors of products and reactants. This reaction representation doesn't need an explicit labeling of a reaction center. The rigorous "product-out" cross-validation (CV) strategy has been suggested. Unlike the naïve "reaction-out" CV approach based on a random selection of items, the proposed one provides with more realistic estimation of prediction accuracy for reactions resulting in novel products. The new methodology has been applied to model rate constants of E2 reactions. It has been demonstrated that the use of the fragment control domain applicability approach significantly increases prediction accuracy of the models. The models obtained with new "mixture" approach performed better than those required either explicit (Condensed Graph of Reaction) or implicit (reaction fingerprints) reaction center labeling.

  11. PhreeqcRM: A reaction module for transport simulators based on the geochemical model PHREEQC

    Science.gov (United States)

    Parkhurst, David L.; Wissmeier, Laurin

    2015-09-01

    PhreeqcRM is a geochemical reaction module designed specifically to perform equilibrium and kinetic reaction calculations for reactive transport simulators that use an operator-splitting approach. The basic function of the reaction module is to take component concentrations from the model cells of the transport simulator, run geochemical reactions, and return updated component concentrations to the transport simulator. If multicomponent diffusion is modeled (e.g., Nernst-Planck equation), then aqueous species concentrations can be used instead of component concentrations. The reaction capabilities are a complete implementation of the reaction capabilities of PHREEQC. In each cell, the reaction module maintains the composition of all of the reactants, which may include minerals, exchangers, surface complexers, gas phases, solid solutions, and user-defined kinetic reactants. PhreeqcRM assigns initial and boundary conditions for model cells based on standard PHREEQC input definitions (files or strings) of chemical compositions of solutions and reactants. Additional PhreeqcRM capabilities include methods to eliminate reaction calculations for inactive parts of a model domain, transfer concentrations and other model properties, and retrieve selected results. The module demonstrates good scalability for parallel processing by using multiprocessing with MPI (message passing interface) on distributed memory systems, and limited scalability using multithreading with OpenMP on shared memory systems. PhreeqcRM is written in C++, but interfaces allow methods to be called from C or Fortran. By using the PhreeqcRM reaction module, an existing multicomponent transport simulator can be extended to simulate a wide range of geochemical reactions. Results of the implementation of PhreeqcRM as the reaction engine for transport simulators PHAST and FEFLOW are shown by using an analytical solution and the reactive transport benchmark of MoMaS.

  12. 初始pH值对果糖-赖氨酸模型美拉德产物抑制香蕉酶促褐变相关性质的影响%Effect of Initial pH in a Fructose-Lysine Model System on the Properties of Maillard Reaction Products Related to the Inhibitory Effect on Banana Enzymatic Browning

    Institute of Scientific and Technical Information of China (English)

    郑杰琼; 李芬芳; 袁德保; 王必尊; 金志强; 丁武; 寇丽萍; 何应对

    2012-01-01

    This study focused on the effect of initial pH in a fructose-lysine model system on the properties of Maillard reaction products(MRPs) related to the inhibitory effect on banana enzymatic browning.MRPs were prepared through the reaction of 0.5 mol/L fructose and 0.5 mol/L lysine at a pH ranging from 2 to 11,110 ℃ for 1 h.Then,their antioxidant activity(including DPPH free radical scavenging ability and reducing power),chelating copper activity and the inhibitory effect on polyphenoloxidase banana were evaluated.The results showed that the Maillard reaction between fructose and lysine could be accelerated at alkaline conditions,however,MRPs prepared from acidic conditions(especially at pH 2 or 3),were more effective in inhibiting banana polyphenoloxidase and scavenging DPPH free radicals.The reducing power of MRPs prepared at pH 9 was highest,while those prepared at pH 2 had the lowest reducing power.Chelating copper activity of MRPs prepared at pH 2—4 or pH 11 was predominant.Generally,initial pH showed a significant effect on the efficacy of MRPs for inhibiting banana enzymatic browning,and the properties related to the inhibitory effect of MRPs prepared at different initial pHs were much different from each other,such as DPPH radical scavenging ability,reducing power,chelating copper activity and the inhibitory effect on banana polyphenoloxidase.It could also be deduced that early stage MRPs may play key roles in inhibiting banana polyphenoloxidase.%研究初始pH值对果糖-赖氨酸模型体系美拉德反应产物(MRPs)抑制香蕉酶促褐变相关性质的影响。通过调节初始pH值(2~11),于110℃条件下反应1h得到MRPs,对产物DPPH自由基清除能力、还原力、螯合Cu2+能力、抑制多酚氧化酶酶活能力进行考察。结果表明:碱性条件促使美拉德反应加剧,酸性条件MRPs能更有效抑制香蕉多酚氧化酶酶活力及清除DPPH自由基;pH9时的MRPs具有最好的还原力,而pH2时的MRPs

  13. Hydrochemical reactions and origin of offshore relatively fresh pore water from core samples in Hong Kong

    Science.gov (United States)

    Kwong, Hiu Tung; Jiao, Jiu Jimmy

    2016-06-01

    The existence of relatively fresh pore water offshore has been well recognised over the globe but studies on the chemistry of the pore water from offshore geological formations are extremely limited. This study aims to characterize the hydrochemistry of the submarine groundwater body in Hong Kong. It looks into the major ion concentrations and the stable isotopic compositions of pore water extracted from core samples from an offshore 42.30-m vibrocore in the southwestern Hong Kong waters. A minimum Cl- level of about one-third of that in typical seawater was noted in the terrestrial sediments, suggesting the presence of offshore relatively fresh water. Unexpectedly high NH4+ levels are attributed to organic matter decomposition in the terrestrial sediments. The leaching of shells due to exposure of marine sediments at sea-level low stands raises the Mg2+ and Ca2+ concentrations. Base Exchange Indices show weak cation exchange reactions in which Na+ and K+ are released while Mg2+ and Ca2+ are adsorbed. Isotopic compositions of pore water reveal that the low-salinity water is probably the relic water sequestered in fluvial systems during relative sea-level low stands. Cores properly stored in a freezer for a long time has been used to study the pore water chemistry. For the first time, this study introduces an approach to correct the measured data by considering the possible evaporation effect during the transportation and storage of the samples. Corrections for evaporation were applied to the major ion concentrations and the stable isotopic compositions of pore water measured. It is found that the corrections determined by the Cl- mass balance approach are more reliable. The corrected measurements give more reasonable observations and hence allow sensible conclusions on the hydrochemical reactions and the origin of pore water.

  14. Stability of convective patterns in reaction fronts: a comparison of three models.

    Science.gov (United States)

    Vasquez, Desiderio A; Coroian, Dan I

    2010-09-01

    Autocatalytic reaction fronts generate density gradients that may lead to convection. Fronts propagating in vertical tubes can be flat, axisymmetric, or nonaxisymmetric, depending on the diameter of the tube. In this paper, we study the transitions to convection as well as the stability of different types of fronts. We analyze the stability of the convective reaction fronts using three different models for front propagation. We use a model based on a reaction-diffusion-advection equation coupled to the Navier-Stokes equations to account for fluid flow. A second model replaces the reaction-diffusion equation with a thin front approximation where the front speed depends on the front curvature. We also introduce a new low-dimensional model based on a finite mode truncation. This model allows a complete analysis of all stable and unstable fronts.

  15. Modeling of the symmetry factor of electrochemical proton discharge via the Volmer reaction

    DEFF Research Database (Denmark)

    Björketun, Mårten E.; Tripkovic, Vladimir; Skúlason, Egill

    2013-01-01

    A scheme for evaluating symmetry factors of elementary electrode reactions using a density functional theory (DFT) based model of the electrochemical double layer is presented. As an illustration, the symmetry factor is determined for hydrogen adsorption via the electrochemical Volmer reaction. T...

  16. Reactions to Discrimination, Stigmatization, Ostracism, and Other Forms of Interpersonal Rejection: A Multimotive Model

    Science.gov (United States)

    Richman, Laura Smart; Leary, Mark R.

    2009-01-01

    This article describes a new model that provides a framework for understanding people's reactions to threats to social acceptance and belonging as they occur in the context of diverse phenomena such as rejection, discrimination, ostracism, betrayal, and stigmatization. People's immediate reactions are quite similar across different forms of…

  17. New tools in modulating Maillard reaction from model systems to food

    NARCIS (Netherlands)

    Troise, A.D.

    2015-01-01

    New tools in modulating Maillard reaction from model systems to food
    The Maillard reaction (MR) supervises the final quality of foods and occupies a prominent place in food science. The first stable compounds, the Amadori rearrangement products (

  18. Modeling Proton- and Light Ion-Induced Reactions at Low Energies in the MARS15 Code

    Energy Technology Data Exchange (ETDEWEB)

    Rakhno, I. L. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Mokhov, N. V. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Gudima, K. K. [National Academy of Sciences, Cisineu (Moldova)

    2015-04-25

    An implementation of both ALICE code and TENDL evaluated nuclear data library in order to describe nuclear reactions induced by low-energy projectiles in the Monte Carlo code MARS15 is presented. Comparisons between results of modeling and experimental data on reaction cross sections and secondary particle distributions are shown.

  19. Stochastic modeling of biochemical systems with multistep reactions using state-dependent time delay.

    Science.gov (United States)

    Wu, Qianqian; Tian, Tianhai

    2016-08-24

    To deal with the growing scale of molecular systems, sophisticated modelling techniques have been designed in recent years to reduce the complexity of mathematical models. Among them, a widely used approach is delayed reaction for simplifying multistep reactions. However, recent research results suggest that a delayed reaction with constant time delay is unable to describe multistep reactions accurately. To address this issue, we propose a novel approach using state-dependent time delay to approximate multistep reactions. We first use stochastic simulations to calculate time delay arising from multistep reactions exactly. Then we design algorithms to calculate time delay based on system dynamics precisely. To demonstrate the power of proposed method, two processes of mRNA degradation are used to investigate the function of time delay in determining system dynamics. In addition, a multistep pathway of metabolic synthesis is used to explore the potential of the proposed method to simplify multistep reactions with nonlinear reaction rates. Simulation results suggest that the state-dependent time delay is a promising and accurate approach to reduce model complexity and decrease the number of unknown parameters in the models.

  20. A model for void-induced back reaction between radiolytic products in NaCl

    NARCIS (Netherlands)

    Turkin, A.A.; Dubinko, V.I.; Vainshtein, D.I.; Hartog, H.W. den

    2002-01-01

    A kinetic model is formulated for the chemical reaction between radiolytic sodium colloids and gas bubbles, which are brought into contact with each other during the exposure to ionising radiation by the growing voids. The reaction starts with the evaporation of Na atoms into the void due to the loc

  1. New tools in modulating Maillard reaction from model systems to food

    NARCIS (Netherlands)

    Troise, A.D.

    2015-01-01

    New tools in modulating Maillard reaction from model systems to food
    The Maillard reaction (MR) supervises the final quality of foods and occupies a prominent place in food science. The first stable compounds, the Amadori rearrangement products (

  2. A measurement model for general noise reaction in response to aircraft noise

    NARCIS (Netherlands)

    Kroesen, M.; Schreckenberg, D.

    2011-01-01

    In this paper a measurement model for general noise reaction (GNR) in response to aircraft noise is developed to assess the performance of aircraft noise annoyance and a direct measure of general reaction as indicators of this concept. For this purpose GNR is conceptualized as a superordinate latent

  3. Consistent post-reaction vibrational energy redistribution in DSMC simulations using TCE model

    Science.gov (United States)

    Borges Sebastião, Israel; Alexeenko, Alina

    2016-10-01

    The direct simulation Monte Carlo (DSMC) method has been widely applied to study shockwaves, hypersonic reentry flows, and other nonequilibrium flow phenomena. Although there is currently active research on high-fidelity models based on ab initio data, the total collision energy (TCE) and Larsen-Borgnakke (LB) models remain the most often used chemistry and relaxation models in DSMC simulations, respectively. The conventional implementation of the discrete LB model, however, may not satisfy detailed balance when recombination and exchange reactions play an important role in the flow energy balance. This issue can become even more critical in reacting mixtures involving polyatomic molecules, such as in combustion. In this work, this important shortcoming is addressed and an empirical approach to consistently specify the post-reaction vibrational states close to thermochemical equilibrium conditions is proposed within the TCE framework. Following Bird's quantum-kinetic (QK) methodology for populating post-reaction states, the new TCE-based approach involves two main steps. The state-specific TCE reaction probabilities for a forward reaction are first pre-computed from equilibrium 0-D simulations. These probabilities are then employed to populate the post-reaction vibrational states of the corresponding reverse reaction. The new approach is illustrated by application to exchange and recombination reactions relevant to H2-O2 combustion processes.

  4. Importance of cytochromes in cyclization reactions: quantum chemical study on a model reaction of proguanil to cycloguanil.

    Science.gov (United States)

    Arfeen, Minhajul; Patel, Dhilon S; Abbat, Sheenu; Taxak, Nikhil; Bharatam, Prasad V

    2014-10-30

    Proguanil, an anti-malarial prodrug, undergoes cytochrome P450 catalyzed biotransformation to the pharmacologically active triazine metabolite (cycloguanil), which inhibits plasmodial dihydrofolate reductase. This cyclization is catalyzed by CYP2C19 and many anti-malarial lead compounds are being designed and synthesized to exploit this pathway. Quantum chemical calculations were performed using the model species (Cpd I for active species of cytochrome and N4-isopropyl-N6-methylbiguanide for proguanil) to elucidate the mechanism of the cyclization pathway. The overall reaction involves the loss of a water molecule, and is exothermic by approximately 55 kcal/mol, and involves a barrier of approximately 17 kcal/mol. The plausible reaction pathway involves the initial H-radical abstraction from the isopropyl group by Cpd I, followed by two alternative paths- (i) oxygen rebound to provide hydroxyl derivative and (ii) loss of additional H-radical to yield 1,3,5-triazatriene, which undergoes cyclization. This study helped in understanding the role of the active species of cytochromes in this important cyclization reaction. Copyright © 2014 Wiley Periodicals, Inc.

  5. Transition state models for probing stereoinduction in Evans chiral auxiliary-based asymmetric aldol reactions.

    Science.gov (United States)

    Shinisha, C B; Sunoj, Raghavan B

    2010-09-08

    The use of chiral auxiliaries is one of the most fundamental protocols employed in asymmetric synthesis. In the present study, stereoselectivity-determining factors in a chiral auxiliary-based asymmetric aldol reaction promoted by TiCl(4) are investigated by using density functional theory methods. The aldol reaction between chiral titanium enolate [derived from Evans propionyl oxazolidinone (1a) and its variants oxazolidinethione (1b) and thiazolidinethione (1c)] and benzaldehyde is examined by using transition-state modeling. Different stereochemical possibilities for the addition of titanium enolates to aldehyde are compared. On the basis of the coordination of the carbonyl/thiocarbonyl group of the chiral auxiliary with titanium, both pathways involving nonchelated and chelated transition states (TSs) are considered. The computed relative energies of the stereoselectivity-determining C-C bond formation TSs in the nonchelated pathway, for both 1a and 1c, indicate a preference toward Evans syn aldol product. The presence of a ring carbonyl or thiocarbonyl group in the chiral auxiliary renders the formation of neutral TiCl(3)-enolate, which otherwise is energetically less favored as compared to the anionic TiCl(4)-enolate. Hence, under suitable conditions, the reaction between titanium enolate and aldehyde is expected to be viable through chelated TSs leading to the selective formation of non-Evans syn aldol product. Experimentally known high stereoselectivity toward Evans syn aldol product is effectively rationalized by using the larger energy differences between the corresponding diastereomeric TSs. In both chelated and nonchelated pathways, the attack by the less hindered face of the enolate on aldehyde through a chair-like TS with an equatorial disposition of the aldehydic substituent is identified as the preferred mode. The steric hindrance offered by the isopropyl group and the possible chelation are identified as the key reasons behind the interesting

  6. Social contexts of exclusionary reactions: study on Muslim and Christian relation in the city of Ambon

    Directory of Open Access Journals (Sweden)

    Cahyo Pamungkas

    2017-06-01

    Full Text Available This study aims to answer the question of what social context related to atti- tudes of exclusionary reactions between Muslims and Christians. The data used in this research is resulted from interviews in the city of Ambon. The conceptual framework used to analyze findings of fieldwork is about relation- ship between ethno-religious identification and exclusionary reactions. In addition, actual or symbolic competition in the political, economic, social and cultural behaviour contributes to exclusionary attitudes. Likewise, the collective memory of the conflict led individuals to have prejudices against out-group members. Based on interview data, this study indicates that exclu- sionary reactions present in the city of Ambon in the form of social avoidance between Muslim and Christian students and the support for residential segre- gation. Both of these phenomena related to political and symbolic competi- tion in public institutions such as public universities. Also, social processes of implanting ethno-religious identity in their families have roles in the creation of prejudicial attitudes against out-group members. The collective memory of the conflict also contributes unto the phenomena of social avoidance and support for residential segregation. Studi ini bertujuan untuk menjawab pertanyaan konteks sosial apa yang berkaitan dengan meningkatnya fenomena eksklusivisme sosial antara umat Islam dan Kristen. Data yang digunakan sebagai basis untuk menjawab pertayaan ini tersebut berasal dari sejumlah wawancara di Kota Ambon. Kerangka konsep yang digunakan untuk menganalisis temuan lapangan adalah tentang hubungan identifikasi terhadap identitas kelompok etnik dan agama dengan perilaku mengecualikan kelompok lain. Selain itu, kompetisi aktual maupun simbolik dalam bidang politik, ekonomi, dan sosial budaya ikut memberikan kontribusi pada perilaku mengecualikan kelompok lain. Demikian juga memori kolektif mengenai konflik di masa lalu menjadikan

  7. Geometrical Models of the Phase Space Structures Governing Reaction Dynamics

    CERN Document Server

    Waalkens, Holger

    2009-01-01

    Hamiltonian dynamical systems possessing equilibria of ${saddle} \\times {centre} \\times...\\times {centre}$ stability type display \\emph{reaction-type dynamics} for energies close to the energy of such equilibria; entrance and exit from certain regions of the phase space is only possible via narrow \\emph{bottlenecks} created by the influence of the equilibrium points. In this paper we provide a thorough pedagogical description of the phase space structures that are responsible for controlling transport in these problems. Of central importance is the existence of a \\emph{Normally Hyperbolic Invariant Manifold (NHIM)}, whose \\emph{stable and unstable manifolds} have sufficient dimensionality to act as separatrices, partitioning energy surfaces into regions of qualitatively distinct behavior. This NHIM forms the natural (dynamical) equator of a (spherical) \\emph{dividing surface} which locally divides an energy surface into two components (`reactants' and `products'), one on either side of the bottleneck. This di...

  8. Interindividual reaction time variability is related to resting-state network topology: an electroencephalogram study.

    Science.gov (United States)

    Zhou, G; Liu, P; He, J; Dong, M; Yang, X; Hou, B; Von Deneen, K M; Qin, W; Tian, J

    2012-01-27

    Both anatomical and functional brain network studies have drawn great attention recently. Previous studies have suggested the significant impacts of brain network topology on cognitive function. However, the relationship between non-task-related resting-state functional brain network topology and overall efficiency of sensorimotor processing has not been well identified. In the present study, we investigated the relationship between non-task-related resting-state functional brain network topology and reaction time (RT) in a Go/Nogo task using an electroencephalogram (EEG). After estimating the functional connectivity between each pair of electrodes, graph analysis was applied to characterize the network topology. Two fundamental measures, clustering coefficient (functional segregation) and characteristic path length (functional integration), as well as "small-world-ness" (the ratio between the clustering coefficient and characteristic path length) were calculated in five frequency bands. Then, the correlations between the network measures and RT were evaluated in each band separately. The present results showed that increased overall functional connectivity in alpha and gamma frequency bands was correlated with a longer RT. Furthermore, shorter RT was correlated with a shorter characteristic path length in the gamma band. This result suggested that human RTs were likely to be related to the efficiency of the brain integrating information across distributed brain regions. The results also showed that a longer RT was related to an increased gamma clustering coefficient and decreased small-world-ness. These results provided further evidence of the association between the resting-state functional brain network and cognitive function.

  9. White and grey matter relations to simple, choice, and cognitive reaction time in spina bifida.

    Science.gov (United States)

    Dennis, Maureen; Cirino, Paul T; Simic, Nevena; Juranek, Jenifer; Taylor, W Pat; Fletcher, Jack M

    2016-03-01

    Elevated reaction time (RT) is common in brain disorders. We studied three forms of RT in a neurodevelopmental disorder, spina bifida myelomeningocele (SBM), characterized by regional alterations of both white and grey matter, and typically developing individuals aged 8 to 48 years, in order to establish the nature of the lifespan-relations of RT and brain variables. Cognitive accuracy and RT speed and variability were all impaired in SBM relative to the typically developing group, but the most important effects of SBM on RT are seen on tasks that require a cognitive decision rule. Individuals with SBM are impaired not only in speeded performance, but also in the consistency of their performance on tasks that extend over time, which may contribute to poor performance on a range of cognitive tasks. The group with SBM showed smaller corrected corpus callosum proportions, larger corrected cerebellar white matter proportions, and larger corrected proportions for grey matter in the Central Executive and Salience networks. There were clear negative relations between RT measures and corpus callosum, Central Executive, and Default Mode networks in the group with SBM; relations were not observed in typically developing age peers. Statistical mediation analyses indicated that corpus callosum and Central Executive Network were important mediators. While RT is known to rely heavily on white matter under conditions of typical development and in individuals with adult-onset brain injury, we add the new information that additional involvement of grey matter may be important for a key neuropsychological function in a common neurodevelopmental disorder.

  10. Modelling anisotropic fluid spheres in general relativity

    CERN Document Server

    Boonserm, Petarpa; Visser, Matt

    2015-01-01

    We argue that an arbitrary general relativistic anisotropic fluid sphere, (spherically symmetric but with transverse pressure not equal to radial pressure), can nevertheless be successfully modelled by suitable linear combinations of quite ordinary classical matter: an isotropic perfect fluid, a classical electromagnetic field, and a classical (minimally coupled) scalar field. While the most general decomposition is not unique, a preferred minimal decomposition can be constructed that is unique. We show how the classical energy conditions for the anisotropic fluid sphere can be related to energy conditions for the isotropic perfect fluid, electromagnetic field, and scalar field components of the model. Furthermore we show how this decomposition relates to the distribution of electric charge density and scalar charge density throughout the model that is used to mimic the anisotropic fluid sphere. Consequently, we can build physically reasonable matter models for almost any spherically symmetric spacetime.

  11. Modeling Relational Data via Latent Factor Blockmodel

    CERN Document Server

    Gao, Sheng; Gallinari, Patrick

    2012-01-01

    In this paper we address the problem of modeling relational data, which appear in many applications such as social network analysis, recommender systems and bioinformatics. Previous studies either consider latent feature based models but disregarding local structure in the network, or focus exclusively on capturing local structure of objects based on latent blockmodels without coupling with latent characteristics of objects. To combine the benefits of the previous work, we propose a novel model that can simultaneously incorporate the effect of latent features and covariates if any, as well as the effect of latent structure that may exist in the data. To achieve this, we model the relation graph as a function of both latent feature factors and latent cluster memberships of objects to collectively discover globally predictive intrinsic properties of objects and capture latent block structure in the network to improve prediction performance. We also develop an optimization transfer algorithm based on the general...

  12. Abortion: a review of women's perception in relation to their partner's reactions in two Brazilians cities.

    Science.gov (United States)

    Nonnenmacher, Daniele; Benute, Gláucia Rosana Guerra; Nomura, Roseli Mieko Yamamoto; Azevedo, George Dantas de; Dutra, Elza Maria do Socorro; Rebouças, Melina Séfora Souza; Luci, Mara Cristina Souza de; Francisco, Rossana Pulcineli Vieira

    2014-07-01

    to analyze women's perception in relation to their partner's reaction and behavior during the abortion process in two Brazilian capitals, associating the variables from women who suffered a spontaneous abortion with those from women who induced it. semi-structured, questionnaire-based interviews were conducted with 285 women who underwent spontaneous abortion and 31 who reported having induced it. The data were analyzed using the thematic analysis technique, and, subsequently, by the IBM SPSS Statistics Standard Edition software program. The significance level was set at p abortion referred to the partner as the person who could not find out about the abortion (pabortion was associated with the partner's absence at the time pregnancy was confirmed (p = 0.02) and, in Sao Paulo-SP, with their negative reaction to news of the pregnancy (p = 0.04) and lack of participation in the abortion process (p abortion process as an important factor. The specifics of each capital denote the influence of the geographic and cultural dimension, indicating the need to take into account the particulars of each region in Brazil while considering a holistic approach to women's health.

  13. Micellar Effects on Nucleophilic Addition Reaction and Applicability of Enzyme Catalysis Model

    Directory of Open Access Journals (Sweden)

    R. K. London Singh

    2012-01-01

    Full Text Available This study describes the effect of anionic and cationic micelles on nucleophilic addition reaction of rosaniline hydrochloride (RH with hydroxide under pseudo-first order condition. Strong inhibitory effect is observed due to SDS micelle, whereas CTAB catalysed the reaction. This is explained on the basis of electrostatic and hydrophobic interactions which are simultaneously operating in the reaction system. The kinetic data obtained is quantitatively analysed by applying the positive cooperativity model of enzyme catalysis. Binding constants and influence of counterions on the reaction have also been investigated.

  14. Model Calculation of n + 6Li Reactions Below 20 MeV

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jing-Shang; HAN Yin-Lu

    2001-01-01

    Based on the unified Hauser-Feshbach and exciton model for light nuclei, the calculations of reaction cross sections and the double-differential cross sections for n + 6Li are performed. Since all of the first-particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism must be taken into account. The fitting of the measured data indicates that the three-body break-up process needs to be involved, and the pre-equilibrium reaction mechanism dominates the reaction processes. In light nucleus reactions the recoil effect must be taken into account.``

  15. Modeling the Electrochemical Hydrogen Oxidation and Evolution Reactions on the Basis of Density Functional Theory Calculations

    DEFF Research Database (Denmark)

    Skulason, Egill; Tripkovic, Vladimir; Björketun, Mårten

    2010-01-01

    Density functional theory calculations have been performed for the three elementary steps―Tafel, Heyrovsky, and Volmer―involved in the hydrogen oxidation reaction (HOR) and its reverse, the hydrogen evolution reaction (HER). For the Pt(111) surface a detailed model consisting of a negatively...... charged Pt(111) slab and solvated protons in up to three water bilayers is considered and reaction energies and activation barriers are determined by using a newly developed computational scheme where the potential can be kept constant during a charge transfer reaction. We determine the rate limiting...

  16. Animal models of age related macular degeneration

    OpenAIRE

    Pennesi, Mark E.; Neuringer, Martha; Courtney, Robert J.

    2012-01-01

    Age related macular degeneration (AMD) is the leading cause of vision loss of those over the age of 65 in the industrialized world. The prevalence and need to develop effective treatments for AMD has lead to the development of multiple animal models. AMD is a complex and heterogeneous disease that involves the interaction of both genetic and environmental factors with the unique anatomy of the human macula. Models in mice, rats, rabbits, pigs and non-human primates have recreated many of the ...

  17. Bias Modeling for Distantly Supervised Relation Extraction

    OpenAIRE

    Yang Xiang; Yaoyun Zhang; Xiaolong Wang; Yang Qin; Wenying Han

    2015-01-01

    Distant supervision (DS) automatically annotates free text with relation mentions from existing knowledge bases (KBs), providing a way to alleviate the problem of insufficient training data for relation extraction in natural language processing (NLP). However, the heuristic annotation process does not guarantee the correctness of the generated labels, promoting a hot research issue on how to efficiently make use of the noisy training data. In this paper, we model two types of biases to reduce...

  18. Longitudinal Relations among Parents' Reactions to Children's Negative Emotions, Effortful Control, and Math Achievement in Early Elementary School

    Science.gov (United States)

    Swanson, Jodi; Valiente, Carlos; Lemery-Chalfant, Kathryn; Bradley, Robert H.; Eggum-Wilkens, Natalie D.

    2014-01-01

    Panel mediation models and fixed-effects models were used to explore longitudinal relations among parents' reactions to children's displays of negative emotions, children's effortful control (EC), and children's math achievement (N = 291; M age in fall of kindergarten = 5.66 years, SD = 0.39 year) across kindergarten through…

  19. (Process Models of Counselor Judgment: Proposal and Reactions.)

    Science.gov (United States)

    Strohmer, Douglas C.; And Others

    1982-01-01

    Studied competing process models of counselors' clinical judgment for their capacity to account for variance in prognostic judgments and further tested for parsimony. Patton discusses problems of logic and data analysis in the model's formulation. Provides Stromer's response to the critique. (RC)

  20. (Process Models of Counselor Judgment: Proposal and Reactions.)

    Science.gov (United States)

    Strohmer, Douglas C.; And Others

    1982-01-01

    Studied competing process models of counselors' clinical judgment for their capacity to account for variance in prognostic judgments and further tested for parsimony. Patton discusses problems of logic and data analysis in the model's formulation. Provides Stromer's response to the critique. (RC)

  1. Piecewise linear and Boolean models of chemical reaction networks

    Science.gov (United States)

    Veliz-Cuba, Alan; Kumar, Ajit; Josić, Krešimir

    2014-01-01

    Models of biochemical networks are frequently complex and high-dimensional. Reduction methods that preserve important dynamical properties are therefore essential for their study. Interactions in biochemical networks are frequently modeled using Hill functions (xn/(Jn + xn)). Reduced ODEs and Boolean approximations of such model networks have been studied extensively when the exponent n is large. However, while the case of small constant J appears in practice, it is not well understood. We provide a mathematical analysis of this limit, and show that a reduction to a set of piecewise linear ODEs and Boolean networks can be mathematically justified. The piecewise linear systems have closed form solutions that closely track those of the fully nonlinear model. The simpler, Boolean network can be used to study the qualitative behavior of the original system. We justify the reduction using geometric singular perturbation theory and compact convergence, and illustrate the results in network models of a toggle switch and an oscillator. PMID:25412739

  2. Piecewise linear and Boolean models of chemical reaction networks.

    Science.gov (United States)

    Veliz-Cuba, Alan; Kumar, Ajit; Josić, Krešimir

    2014-12-01

    Models of biochemical networks are frequently complex and high-dimensional. Reduction methods that preserve important dynamical properties are therefore essential for their study. Interactions in biochemical networks are frequently modeled using Hill functions ([Formula: see text]). Reduced ODEs and Boolean approximations of such model networks have been studied extensively when the exponent [Formula: see text] is large. However, while the case of small constant [Formula: see text] appears in practice, it is not well understood. We provide a mathematical analysis of this limit and show that a reduction to a set of piecewise linear ODEs and Boolean networks can be mathematically justified. The piecewise linear systems have closed-form solutions that closely track those of the fully nonlinear model. The simpler, Boolean network can be used to study the qualitative behavior of the original system. We justify the reduction using geometric singular perturbation theory and compact convergence, and illustrate the results in network models of a toggle switch and an oscillator.

  3. Application of click chemistry conditions for 5-bromo-2'-deoxyuridine determination through Fenton and related reactions.

    Science.gov (United States)

    Cappella, Paolo; Pulici, Maurizio; Gasparri, Fabio

    2015-01-05

    Mixtures of ascorbate and copper used in certain click chemistry experimental conditions act as oxidizing agents, catalyzing the formation of reactive oxygen species through Fenton and related reactions. Hydroxyl radicals act as chemical nucleases, introducing DNA strand breaks that can be exploited for BrdU immunostaining in place of acid denaturation. This procedure is readily applicable to high content analysis and flow cytometry assays, and provides results comparable to click chemistry EdU cycloaddition and classical BrdU immunodetection. Importantly, this approach allows preservation of labile epitopes such as phosphoproteins. This unit describes an optimized method that successfully employs Fenton chemistry for simultaneous detection of phosphoproteins and BrdU in intact cells.

  4. Mechanical Models of Fault-Related Folding

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, A. M.

    2003-01-09

    The subject of the proposed research is fault-related folding and ground deformation. The results are relevant to oil-producing structures throughout the world, to understanding of damage that has been observed along and near earthquake ruptures, and to earthquake-producing structures in California and other tectonically-active areas. The objectives of the proposed research were to provide both a unified, mechanical infrastructure for studies of fault-related foldings and to present the results in computer programs that have graphical users interfaces (GUIs) so that structural geologists and geophysicists can model a wide variety of fault-related folds (FaRFs).

  5. A comparison of quantum and quasiclassical statistical models for reactions of electronically excited atoms with molecular hydrogen.

    Science.gov (United States)

    Aoiz, F J; González-Lezana, T; Sáez Rábanos, V

    2008-09-01

    A detailed comparison of statistical models based on the quasiclassical trajectory (SQCT) and quantum mechanical (SQM) methods is presented in this work for the C((1)D)+H(2), S((1)D)+H(2), O((1)D)+H(2) and N((2)D)+H(2) insertion reactions. Reaction probabilities, integral (ICS) and differential (DCS) cross sections at different levels of product's state resolution are shown and discussed for these reactions. The agreement is in most cases excellent and indicates that the effect of tunneling through the centrifugal barrier is negligible. However, if there exists a dynamical barrier, as in the case of the N((2)D)+H(2) reaction, some of the SQM results can be slightly different than those calculated with the SQCT model. The rationale of the observed similarities and discrepancies can be traced back to the specific topologies of the potential energy surfaces for each of the reactions examined. The SQCT model is sensitive enough to show the relatively small inaccuracies resulting from the decoupling inherent to the centrifugal sudden approximation when used in the SQM calculations. In addition, the effect of ignoring the parity conservation is also examined. This effect is in general minor except in particular cases such as the DCS from initial rotational state j=0, which requires, in order to reproduce the sharp forward and backward peaks, the explicit conservation of parity.

  6. A hydrodynamics-reaction kinetics coupled model for evaluating bioreactors derived from CFD simulation.

    Science.gov (United States)

    Wang, Xu; Ding, Jie; Guo, Wan-Qian; Ren, Nan-Qi

    2010-12-01

    Investigating how a bioreactor functions is a necessary precursor for successful reactor design and operation. Traditional methods used to investigate flow-field cannot meet this challenge accurately and economically. Hydrodynamics model can solve this problem, but to understand a bioreactor in sufficient depth, it is often insufficient. In this paper, a coupled hydrodynamics-reaction kinetics model was formulated from computational fluid dynamics (CFD) code to simulate a gas-liquid-solid three-phase biotreatment system for the first time. The hydrodynamics model is used to formulate prediction of the flow field and the reaction kinetics model then portrays the reaction conversion process. The coupled model is verified and used to simulate the behavior of an expanded granular sludge bed (EGSB) reactor for biohydrogen production. The flow patterns were visualized and analyzed. The coupled model also demonstrates a qualitative relationship between hydrodynamics and biohydrogen production. The advantages and limitations of applying this coupled model are discussed.

  7. Chaos in the Showalter-Noyes-Bar-Eli model of the Belousov-Zhabotinskii reaction

    Science.gov (United States)

    Lindberg, David; Turner, Jack S.; Barkley, Dwight

    1990-03-01

    The observation of robust, large-scale chaos in the Showalter-Noyes-Bar-Eli model of the Belousov-Zhabotinskii reaction is reported. The chaos observed is comparable to that found in CSTR experiments at low flow rates.

  8. Porphyrin-quinone compounds as synthetic models of the reaction centre in photosynthesis

    Science.gov (United States)

    Borovkov, V. V.; Evstigneeva, Rima P.; Strekova, L. N.; Filippovich, E. I.

    1989-06-01

    Data on the synthesis, steric structure, and photochemical properties of porphyrin-quinone compounds as synthetic models of the reaction centre in photosynthesis are examined and described systematically. The bibliography includes 113 references.

  9. Transport dissipative particle dynamics model for mesoscopic advection- diffusion-reaction problems

    Energy Technology Data Exchange (ETDEWEB)

    Zhen, Li; Yazdani, Alireza; Tartakovsky, Alexandre M.; Karniadakis, George E.

    2015-07-07

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic DPD framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between particles, and an analytical formula is proposed to relate the mesoscopic concentration friction to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  10. A discrete solvent reaction field model for calculating frequency-dependent hyperpolarizabilities of molecules in solution

    Science.gov (United States)

    Jensen, Lasse; van Duijnen, Piet Th.; Snijders, Jaap G.

    2003-12-01

    We present a discrete solvent reaction field (DRF) model for the calculation of frequency-dependent hyperpolarizabilities of molecules in solution. In this model the solute is described using density functional theory (DFT) and the discrete solvent molecules are described with a classical polarizable model. The first hyperpolarizability is obtained in an efficient way using time-dependent DFT and the (2n+1) rule. The method was tested for liquid water using a model in which a water molecule is embedded in a cluster of 127 classical water molecules. The frequency-dependent first and second hyperpolarizabilities related to the electric field induced second harmonic generation (EFISH) experiment, were calculated both in the gas phase and in the liquid phase. For water in the gas phase, results are obtained in good agreement with correlated wave function methods and experiments by using the so-called shape-corrected exchange correlation (xc)-potentials. In the liquid phase the effect of using asymptotically correct functionals is discussed. The model reproduced the experimentally observed sign change in the first hyperpolarizaibility when going from the gas phase to the liquid phase. Furthermore, it is shown that the first hyperpolarizability is more sensitive to damping of the solvent-solute interactions at short range than the second hyperpolarizability.

  11. Automatic Activity and Reaction Time in Relation to Extraversion and Behavioral Impulsivity in Children and Adolescents.

    Science.gov (United States)

    Zahn, Theodore P.; And Others

    1994-01-01

    Forty-five children and adolescents had skin conductance recorded during a presentation of tones and a reaction time test and were assessed for extraversion. Found that extraversion was negatively correlated with skin conductance response magnitudes to all stimuli--somewhat more strongly for reaction-time stimuli--and with reaction time. (HTH)

  12. Relating structure and dynamics in organisation models

    NARCIS (Netherlands)

    Jonkers, C.M.; Treur, J.

    2008-01-01

    To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems, on t

  13. Impact of Nuclear Reaction Uncertainties on AGB Nucleosynthesis Models

    CERN Document Server

    Bisterzo, S; Kaeppeler, F; Wiescher, M; Travaglio, C

    2012-01-01

    Asymptotic giant branch (AGB) stars with low initial mass (1 - 3 Msun) are responsible for the production of neutron-capture elements through the main s-process (main slow neutron capture process). The major neutron source is 13C(alpha, n)16O, which burns radiatively during the interpulse periods at about 8 keV and produces a rather low neutron density (10^7 n/cm^3). The second neutron source 22Ne(alpha, n)25Mg, partially activated during the convective thermal pulses when the energy reaches about 23 keV, gives rise to a small neutron exposure but a peaked neutron density (Nn(peak) > 10^11 n/cm^3). At metallicities close to solar, it does not substantially change the final s-process abundances, but mainly affects the isotopic ratios near s-path branchings sensitive to the neutron density. We examine the effect of the present uncertainties of the two neutron sources operating in AGB stars, as well as the competition with the 22Ne(alpha, gamma)26Mg reaction. The analysis is carried out on AGB the main-s process...

  14. Dynamical Coupled-Channel Model of Meson Production Reactions in the Nucleon Resonance Region

    Energy Technology Data Exchange (ETDEWEB)

    T.-S. H. Lee; A. Matsuyama; T. Sato

    2006-11-15

    A dynamical coupled-channel model is presented for investigating the nucleon resonances (N*) in the meson production reactions induced by pions and photons. Our objective is to extract the N* parameters and to investigate the meson production reaction mechanisms for mapping out the quark-gluon substructure of N* from the data. The model is based on an energy-independent Hamiltonian which is derived from a set of Lagrangians by using a unitary transformation method.

  15. AUTO-DARBOUX TRANSFORMATION AND EXACT SOLUTIONS OF THE BRUSSELATOR REACTION DIFFUSION MODEL

    Institute of Scientific and Technical Information of China (English)

    闫振亚; 张鸿庆

    2001-01-01

    Firstly, using the improved homogeneous balance method, an auto-Darboux transformation (ADT) for the Brusselator reaction diffusion model is found. Based on the ADT, several exact solutions are obtained which contain some authors' results known.Secondly, by using a series of transformations, the model is reduced into a nonlinear reaction diffusion equation and then through using sine- cosine method, more exact solutions are found which contain soliton solutions.

  16. Evidence for a transition state model compound of in-plane vinylic SN2 reaction.

    Science.gov (United States)

    Yamaguchi, Torahiko; Yamamoto, Yohsuke; Fujiwara, Yoshihisa; Tanimoto, Yoshifumi

    2005-06-23

    [reaction: see text] To isolate a transition state model compound of an in-plane vinylic S(N)2 reaction, vinyl bromide 6 bearing a newly synthesized tridentate ligand derived from 1,8-dimethoxythioxanthen-9-one (5) was prepared as a precursor. Although irradiation of 6 gave demethylated benzofuran 12, a transient broad peak which indicates formation of the desired transition state model compound was observed in the laser flash photolytic study.

  17. A model SN2 reaction ‘on water’ does not show rate enhancement

    Science.gov (United States)

    Nelson, Katherine V.; Benjamin, Ilan

    2011-05-01

    Molecular dynamics calculations of the benchmark nucleophilic substitution reaction (SN2) Cl- + CH3Cl are carried out at the water liquid/vapor interface. The reaction free energy profile and the activation free energy are determined as a function of the reactants' location normal to the surface. The activation free energy remains almost constant relative to that in bulk water, despite the fact that the barrier is expected to significantly decrease as the reaction is carried out near the vapor phase. We show that this is due to the combined effects of a clustering of water molecules around the nucleophile and a relatively weak hydration of the transition state.

  18. Learning, Behaviour and Reaction Framework: A Model for Training Raters to Improve Assessment Quality

    Science.gov (United States)

    Chen, Chung-Yang; Chang, Huiju; Hsu, Wen-Chin; Sheen, Gwo-Ji

    2017-01-01

    This paper proposes a training model for raters, with the goal to improve the intra- and inter-consistency of evaluation quality for higher education curricula. The model, termed the learning, behaviour and reaction (LBR) circular training model, is an interdisciplinary application from the business and organisational training domain. The…

  19. Reaction invariant-based reduction of the activated sludge model ASM1 for batch applications

    DEFF Research Database (Denmark)

    Santa Cruz, Judith A.; Mussati, Sergio F.; Scenna, Nicolás J.

    2016-01-01

    that are unaffected by the reaction progress, i.e. so-called reaction invariants. The reaction invariant concept can be used to reduce the number of ordinary differential equations (ODEs) involved in batch bioreactor models. In this paper, a systematic methodology of model reduction based on this concept is applied...... to batch activated sludge processes described by the Activated Sludge Model No. 1 (ASM1) for carbon and nitrogen removal. The objective of the model reduction is to describe the exact dynamics of the states predicted by the original model with a lower number of ODEs. This leads to a reduction...... of the numerical complexity as nonlinear ODEs are replaced by linear algebraic relationships predicting the exact dynamics of the original model....

  20. Coarse-graining the calcium dynamics on a stochastic reaction-diffusion lattice model

    CERN Document Server

    Shen, Chuansheng

    2013-01-01

    We develop a coarse grained (CG) approach for efficiently simulating calcium dynamics in the endoplasmic reticulum membrane based on a fine stochastic lattice gas model. By grouping neighboring microscopic sites together into CG cells and deriving CG reaction rates using local mean field approximation, we perform CG kinetic Monte Carlo (kMC) simulations and find the results of CG-kMC simulations are in excellent agreement with that of the microscopic ones. Strikingly, there is an appropriate range of coarse proportion $m$, corresponding to the minimal deviation of the phase transition point compared to the microscopic one. For fixed $m$, the critical point increases monotonously as the system size increases, especially, there exists scaling law between the deviations of the phase transition point and the system size. Moreover, the CG approach provides significantly faster Monte Carlo simulations which are easy to implement and are directly related to the microscopics, so that one can study the system size eff...

  1. A soil diffusion-reaction model for surface COS flux: COSSM v1

    Directory of Open Access Journals (Sweden)

    W. Sun

    2015-07-01

    Full Text Available Soil exchange of carbonyl sulfide (COS is the second largest COS flux in terrestrial ecosystems. A novel application of COS is the separation of gross primary productivity (GPP from concomitant respiration. This method requires that soil COS exchange is relatively small and can be well quantified. Existing models for soil COS flux have incorporated empirical temperature and moisture functions derived from laboratory experiments, but not explicitly resolved diffusion in the soil column. We developed a 1-D diffusion-reaction model for soil COS exchange that accounts for COS uptake and production, relates source-sink terms to environmental variables, and has an option to enable surface litter layers. We evaluated the model with field data from a wheat field (Southern Great Plains (SGP, OK, USA and an oak woodland (Stunt Ranch Reserve, CA, USA. The model was able to reproduce all observed features of soil COS exchange such as diurnal variations and sink-source transitions. We found that soil COS uptake is strongly diffusion controlled, and limited by low COS concentrations in the soil if there is COS uptake in the litter layer. The model provides novel insights into the balance between soil COS uptake and production: a higher COS production capacity was required despite lower COS emissions during the growing season compared to the post-senescence period at SGP, and unchanged COS uptake capacity despite the dominant role of COS emissions after senescence. Once there is a database of soil COS parameters for key biomes, we expect the model will also be useful to simulate soil COS exchange at regional to global scales.

  2. A soil diffusion-reaction model for surface COS flux: COSSM v1

    Science.gov (United States)

    Sun, W.; Maseyk, K.; Lett, C.; Seibt, U.

    2015-10-01

    Soil exchange of carbonyl sulfide (COS) is the second largest COS flux in terrestrial ecosystems. A novel application of COS is the separation of gross primary productivity (GPP) from concomitant respiration. This method requires that soil COS exchange is relatively small and can be well quantified. Existing models for soil COS flux have incorporated empirical temperature and moisture functions derived from laboratory experiments but not explicitly resolved diffusion in the soil column. We developed a mechanistic diffusion-reaction model for soil COS exchange that accounts for COS uptake and production, relates source-sink terms to environmental variables, and has an option to enable surface litter layers. We evaluated the model with field data from a wheat field (Southern Great Plains (SGP), OK, USA) and an oak woodland (Stunt Ranch Reserve, CA, USA). The model was able to reproduce all observed features of soil COS exchange such as diurnal variations and sink-source transitions. We found that soil COS uptake is strongly diffusion controlled and limited by low COS concentrations in the soil if there is COS uptake in the litter layer. The model provides novel insights into the balance between soil COS uptake and production: a higher COS production capacity was required despite lower COS emissions during the growing season compared to the post-senescence period at SGP, and unchanged COS uptake capacity despite the dominant role of COS emissions after senescence. Once there is a database of soil COS parameters for key biomes, we expect the model will also be useful to simulate soil COS exchange at regional to global scales.

  3. Comparisons of late vaginal mucosal reactions between interstitial and conventional intracavitary brachytherapy in patients with gynecological cancer: speculation on the relation between pallor reaction and stenosis.

    Science.gov (United States)

    Yoshida, Ken; Yamazaki, Hideya; Nakamura, Satoaki; Masui, Koji; Kotsuma, Tadayuki; Baek, Sung Jae; Akiyama, Hironori; Tanaka, Eiichi; Yoshioka, Yasuo

    2013-09-01

    To examine late vaginal mucosal reactions in patients following interstitial brachytherapy (ISBT) compared with that of intracavitary brachytherapy (ICBT). We introduced a modified Dische score to examine late reactions in vaginal mucosa of patients with gynecological cancer who underwent vaginal brachytherapy at 6, 12, 18, 24, 36, and 60 months after treatment. A comparison was made between patients who underwent ISBT (n=37) and those under conventional ICBT (n=63) with a median follow-up time of 41 months. The ICBT group included only patients with newly diagnosed cervical cancer, whereas the ISBT group included 17 patients with recurrent and 20 with newly-diagnosed cancer. Grade 1 reactions of bleeding and discharge were exhibited by <12% of patients. Erythema was detected in approximately 30% (mainly grade 1) of the patients. A total of two (3%) patients developed superficial ulceration after ICBT, whereas three (8%) grade 1 ulcers were detected in patients after ISBT. Telangiectasias were detected in approximately 70% (60% grade 1 and 10% grade 2) of patients. No statistically significant difference was found between the patients after ISBT and ICBT. After ISBT, patients have a higher stenosis rate than after ICBT (p=0.003). The pallor scores showed a strong correlation with stenosis (p<0.0001) and were higher in patients after ICBT than in patients after ISBT (p=0.006). After ISBT, patients exhibited milder but similar late mucosal reactions compared to those after ICBT, except the fact that the stenosis was more severe and the pallor reaction was milder in these patients. It can be, therefore, concluded that the pallor reaction is related to stenosis.

  4. Mechanistic insights into RNA transphosphorylation from kinetic isotope effects and linear free energy relationships of model reactions.

    Science.gov (United States)

    Chen, Haoyuan; Giese, Timothy J; Huang, Ming; Wong, Kin-Yiu; Harris, Michael E; York, Darrin M

    2014-10-27

    Phosphoryl transfer reactions are ubiquitous in biology and the understanding of the mechanisms whereby these reactions are catalyzed by protein and RNA enzymes is central to reveal design principles for new therapeutics. Two of the most powerful experimental probes of chemical mechanism involve the analysis of linear free energy relations (LFERs) and the measurement of kinetic isotope effects (KIEs). These experimental data report directly on differences in bonding between the ground state and the rate-controlling transition state, which is the most critical point along the reaction free energy pathway. However, interpretation of LFER and KIE data in terms of transition-state structure and bonding optimally requires the use of theoretical models. In this work, we apply density-functional calculations to determine KIEs for a series of phosphoryl transfer reactions of direct relevance to the 2'-O-transphosphorylation that leads to cleavage of the phosphodiester backbone of RNA. We first examine a well-studied series of phosphate and phosphorothioate mono-, di- and triesters that are useful as mechanistic probes and for which KIEs have been measured. Close agreement is demonstrated between the calculated and measured KIEs, establishing the reliability of our quantum model calculations. Next, we examine a series of RNA transesterification model reactions with a wide range of leaving groups in order to provide a direct connection between observed Brønsted coefficients and KIEs with the structure and bonding in the transition state. These relations can be used for prediction or to aid in the interpretation of experimental data for similar non-enzymatic and enzymatic reactions. Finally, we apply these relations to RNA phosphoryl transfer catalyzed by ribonuclease A, and demonstrate the reaction coordinate-KIE correlation is reasonably preserved. A prediction of the secondary deuterium KIE in this reaction is also provided. These results demonstrate the utility of

  5. Genome-scale Metabolic Reaction Modeling: a New Approach to Geomicrobial Kinetics

    Science.gov (United States)

    McKernan, S. E.; Shapiro, B.; Jin, Q.

    2014-12-01

    Geomicrobial rates, rates of microbial metabolism in natural environments, are a key parameter of theoretical and practical problems in geobiology and biogeochemistry. Both laboratory- and field-based approaches have been applied to study rates of geomicrobial processes. Laboratory-based approaches analyze geomicrobial kinetics by incubating environmental samples under controlled laboratory conditions. Field methods quantify geomicrobial rates by observing the progress of geomicrobial processes. To take advantage of recent development in biogeochemical modeling and genome-scale metabolic modeling, we suggest that geomicrobial rates can also be predicted by simulating metabolic reaction networks of microbes. To predict geomicrobial rates, we developed a genome-scale metabolic model that describes enzyme reaction networks of microbial metabolism, and simulated the network model by accounting for the kinetics and thermodynamics of enzyme reactions. The model is simulated numerically to solve cellular enzyme abundance and hence metabolic rates under the constraints of cellular physiology. The new modeling approach differs from flux balance analysis of system biology in that it accounts for the thermodynamics and kinetics of enzymatic reactions. It builds on subcellular metabolic reaction networks, and hence also differs from classical biogeochemical reaction modeling. We applied the new approach to Methanosarcina acetivorans, an anaerobic, marine methanogen capable of disproportionating acetate to carbon dioxide and methane. The input of the new model includes (1) enzyme reaction network of acetoclastic methanogenesis, and (2) representative geochemical conditions of freshwater sedimentary environments. The output of the simulation includes the proteomics, metabolomics, and energy and matter fluxes of M. acetivorans. Our simulation results demonstrate the predictive power of the new modeling approach. Specifically, the results illustrate how methanogenesis rates vary

  6. Kinetic modeling of mechanisms of industrially important organic reactions in gas and liquid phase

    Energy Technology Data Exchange (ETDEWEB)

    Vahteristo, K.

    2010-07-01

    -trans and skeletal isomerization. Minor side reaction were dimerization and fragmentation. Monomolecular and bimolecular reaction mechanisms for skeletal isomerization explained experimental results almost equally well. Pseudohomogeneous kinetic parameters of reactions 1 and 2 were estimated by usual least squares fitting. Concerning reactions 3 and 4 kinetic parameters were estimated by the leastsquares method, but also the possible cross-correlation and identifiability of parameters were determined using Markov chain Monte Carlo (MCMC) method. Finally using MCMC method, the estimation of model parameters and predictions were performed according to the Bayesian paradigm. According to the fitting results suggested reaction mechanisms explained experimental results rather well. When the possible cross-correlation and identifiability of parameters (Reactions 3 and 4) were determined using MCMC method, the parameters identified well, and no pathological cross-correlation could be seen between any parameter pair. (orig.)

  7. Trends of adverse drug reactions related-hospitalizations in Spain (2001-2006

    Directory of Open Access Journals (Sweden)

    de Miguel Gil

    2010-10-01

    Full Text Available Abstract Background Adverse drug reactions (ADR are a substantial cause of hospital admissions. We conducted a nationwide study to estimate the burden of hospital admissions for ADRs in Spain during a six-year period (2001-2006 along with the associated total health cost. Methods Data were obtained from the national surveillance system for hospital data (Minimum Basic Data Set maintained by the Ministry of Health and Consumer Affairs, and covering more than 95% of Spanish hospitals. From these admissions we selected all hospitalization that were code as drug-related (ICD-9-CM codes E, but intended forms of overdoses, errors in administration and therapeutics failure were excluded. The average number of hospitalizations per year, annual incidence of hospital admissions, average length of stay in the hospital, and case-fatality rate, were calculated. Results During the 2001-2006 periods, the total number of hospitalized patients with ADR diagnosis was 350,835 subjects, 1.69% of all acute hospital admissions in Spain. The estimated incidence of admissions due to ADR decreased during the period 2001-2006 (p Conclusions Approximately 1.69% of all acute hospital admissions were associated with ADRs. The rates were much higher for elderly patients. The total cost of ADR-related hospitalization to the Spanish health system is high and has increased between 2001 and 2006. ADRs are an important cause of admission, resulting in considerable use of national health system beds and a significant number of deaths.

  8. Heterogeneous Reactions of Acetic Acid with Oxide Surfaces: Effects of Mineralogy and Relative Humidity.

    Science.gov (United States)

    Tang, Mingjin; Larish, Whitney A; Fang, Yuan; Gankanda, Aruni; Grassian, Vicki H

    2016-07-21

    We have investigated the heterogeneous uptake of gaseous acetic acid on different oxides including γ-Al2O3, SiO2, and CaO under a range of relative humidity conditions. Under dry conditions, the uptake of acetic acid leads to the formation of both acetate and molecularly adsorbed acetic acid on γ-Al2O3 and CaO and only molecularly adsorbed acetic acid on SiO2. More importantly, under the conditions of this study, dimers are the major form for molecularly adsorbed acetic acid on all three particle surfaces investigated, even at low acetic acid pressures under which monomers are the dominant species in the gas phase. We have also determined saturation surface coverages for acetic acid adsorption on these three oxides under dry conditions as well as Langmuir adsorption constants in some cases. Kinetic analysis shows that the reaction rate of acetic acid increases by a factor of 3-5 for γ-Al2O3 when relative humidity increases from 0% to 15%, whereas for SiO2 particles, acetic acid and water are found to compete for surface adsorption sites.

  9. A Model to Predict Shopper Reaction to Commissary Stockouts

    Science.gov (United States)

    1989-12-01

    38). For these reasons, many firms such as British Airways, Coca - Cola , Domino’s Pizza, Four Seasons Hotels, General Electric (GE), and General Motors...causes consumers to switch brands . Researchers have analyzed response time, inflation, sales promotions, and brand loyalty in hopes of determining...review is Wernerfelt’s study on brand loyalty . The author attempted to develop a model which illustrates why a consumer remains loyal to a brand although

  10. Gynostemma pentaphyllum decreases allergic reactions in a murine asthmatic model.

    Science.gov (United States)

    Huang, Wen-Chung; Kuo, Ming-Ling; Li, Ming-Liang; Yang, Rong-Chi; Liou, Chian-Jiun; Shen, Jiann-Jong

    2008-01-01

    The increasing incidence of asthma in developing countries emphasizes the importance of identifying more effective treatments that have low cost. Gynostemma pentaphyllum (Thunb.) Makino (Cucurbitaceae), a common herbal tea in China, has been used to treat lung inflammation. Since the Th2 cytokines are the major mediators in the pathogenesis of asthma, Th1-biased immune responses caused by G. pentaphyllum might have the potential to relieve asthmatic symptoms. We hypothesized that oral administration of G. pentaphyllum extracts might suppress Th2 cytokine-induced airway inflammation responses in ovalbumin (OVA)-sensitive mice. BALB/c mice were sensitized with intraperitoneal injection and challenged 3 times with OVA inhalation (IH) (the IH3 model). G. pentaphyllum was orally administered for 7 consecutive days before the end of the OVA challenge. In the IH5 model, 2 more OVA challenges were administered to mimic the encounter with an allergen after drug treatment. G. pentaphyllum extracts significantly attenuated airway hyperresponsiveness (AHR) and inhibited eosinophil infiltration in mice in both models. Serum OVA-specific antibodies were also reduced with the treatment. Decreased Th2-type cytokines and increased IFN-gamma were detected in the cultures of OVA-activated splenocytes from treated mice. Our results suggest that G. pentaphyllum extracts might be beneficial for asthma airway inflammation through the suppression of Th2 activity.

  11. Animal models of age related macular degeneration.

    Science.gov (United States)

    Pennesi, Mark E; Neuringer, Martha; Courtney, Robert J

    2012-08-01

    Age related macular degeneration (AMD) is the leading cause of vision loss of those over the age of 65 in the industrialized world. The prevalence and need to develop effective treatments for AMD has lead to the development of multiple animal models. AMD is a complex and heterogeneous disease that involves the interaction of both genetic and environmental factors with the unique anatomy of the human macula. Models in mice, rats, rabbits, pigs and non-human primates have recreated many of the histological features of AMD and provided much insight into the underlying pathological mechanisms of this disease. In spite of the large number of models developed, no one model yet recapitulates all of the features of human AMD. However, these models have helped reveal the roles of chronic oxidative damage, inflammation and immune dysregulation, and lipid metabolism in the development of AMD. Models for induced choroidal neovascularization have served as the backbone for testing new therapies. This article will review the diversity of animal models that exist for AMD as well as their strengths and limitations.

  12. Modelling the effect of the radiation reaction force on the acceleration of ultra-thin foils

    Science.gov (United States)

    Duff, M. J.; Capdessus, R.; King, M.; Del Sorbo, D.; Ridgers, C. P.; McKenna, P.

    2017-05-01

    An investigation of the effects of the radiation reaction force on radiation pressure acceleration is presented. Through 1D(3V) PIC code simulations, it is found that radiation reaction causes a decrease in the target velocity during the interaction of an ultra-intense laser pulse with a solid density thin foil of varying thickness. This change in the target velocity can be related to the loss of backwards-directed electrons due to cooling and reflection in the laser field. The loss of this electron population changes the distribution of the emitted synchrotron radiation. We demonstrate that it is the emission of radiation which leads to the observed decrease in target velocity. Through a modification to the light sail equation of motion (which is used to describe radiation pressure acceleration in thin foils), which accounts for the conversion of laser energy to synchrotron radiation, we can describe this change in target velocity. This model can be tested in future experiments with ultra-high intensity lasers, and will lead to a better understanding of the process of relativistically induced transparency in the new intensity regime.

  13. The kinetic model for slow photoinduced electron transport in the reaction centers of purple bacteria

    Science.gov (United States)

    Serdenko, T. V.; Barabash, Y. M.; Knox, P. P.; Seifullina, N. Kh.

    2016-06-01

    The present work is related to the investigation of slow kinetics of electron transport in the reaction centers (RCs) of Rhodobacter sphaeroides. Experimental data on the absorption kinetics of aqueous solutions of reaction centers at different modes of photoexcitation are given. It is shown that the kinetics of oxidation and reduction of RCs are well described by the sum of three exponential functions. This allows to suggest a two-level kinetic model for electron transport in the RC as a system of four electron-conformational states which correspond to three balance differential equations combined with state equation. The solution of inverse problem made it possible to obtain the rate constant values in kinetic equations for different times and intensities of exciting light. Analysis of rate constant values in different modes of RC excitation allowed to suggest that two mechanisms of structural changes are involved in RC photo-oxidation. One mechanism leads to the increment of the rate of electron return, another one—to its drop. Structural changes were found out to occur in the RCs under incident light. After light was turned off, the reduction of RCs was determined by the second mechanism.

  14. Propagation of neutron-reaction uncertainties through multi-physics models of novel LWR's

    Directory of Open Access Journals (Sweden)

    Hernandez-Solis Augusto

    2017-01-01

    Full Text Available The novel design of the renewable boiling water reactor (RBWR allows a breeding ratio greater than unity and thus, it aims at providing for a self-sustained fuel cycle. The neutron reactions that compose the different microscopic cross-sections and angular distributions are uncertain, so when they are employed in the determination of the spatial distribution of the neutron flux in a nuclear reactor, a methodology should be employed to account for these associated uncertainties. In this work, the Total Monte Carlo (TMC method is used to propagate the different neutron-reactions (as well as angular distributions covariances that are part of the TENDL-2014 nuclear data (ND library. The main objective is to propagate them through coupled neutronic and thermal-hydraulic models in order to assess the uncertainty of important safety parameters related to multi-physics, such as peak cladding temperature along the axial direction of an RBWR fuel assembly. The objective of this study is to quantify the impact that ND covariances of important nuclides such as U-235, U-238, Pu-239 and the thermal scattering of hydrogen in H2O have in the deterministic safety analysis of novel nuclear reactors designs.

  15. Modelling of Turbulent Scalar Fluxes in the Broken Reaction Zones Regime

    Science.gov (United States)

    Im, Hong G.; Chakraborty, Nilanjan; Klein, Markus; Kasten, Christian; Arias, Paul

    2016-11-01

    The LES filtered species transport equation in turbulent reacting flow simulations contains the unclosed turbulent scalar flux that needs to be modelled. It is well known that the statistical behavior of this term and its alignment characteristics with resolved scalar gradient depend on the relative importance of heat release and turbulent velocity fluctuations. Counter-gradient transport has been reported in several earlier studies where the flames under investigation were located either in the corrugated flamelets or thin reaction zones regime of premixed turbulent combustion. Therefore it is useful to understand the statistical behavior of turbulent scalar fluxes if the flame represents the broken reaction zones regime (BRZR). The present analysis aims to provide improved understanding on this subject through an a-priori analysis of a detailed chemistry database consisting of three freely-propagating statistically planar turbulent H2-air premixed flames representing three different regimes of combustion. Results indicate that heat release effects weaken with increasing Karlovitz number, but that counter-gradient transport can still occur for large LES filter size in the BRZR. Furthermore the behaviour of the flux and in particular its sign are different for reactant and product species. KAUST, EPSRC, KAUST Supercomputing Lab, N8, Archer.

  16. Dominant particles and reactions in a two-temperature chemical kinetic model of a decaying SF6 arc

    Science.gov (United States)

    Wang, Xiaohua; Gao, Qingqing; Fu, Yuwei; Yang, Aijun; Rong, Mingzhe; Wu, Yi; Niu, Chunping; Murphy, Anthony B.

    2016-03-01

    reactions by a factor of about 2, while providing results that agree closely with the full model. Thus, the physicochemical processes of SF6 arc can be characterized by relatively few species and reactions in each temperature range. It is noted that the simplified models can also be applied to a wide range of pressures, 1-16 atm, conditions which cover most circuit breaker applications. The simplified species and reactions will allow the computing time of multi-dimensional models, taking into account departures from both thermal and chemical equilibrium, to be decreased dramatically while capturing the main physicochemical processes in SF6 arcs.

  17. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    Science.gov (United States)

    Cyburt, R. H.; Amthor, A. M.; Heger, A.; Johnson, E.; Keek, L.; Meisel, Z.; Schatz, H.; Smith, K.

    2016-10-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p, γ), (α, γ), and (α, p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the Kepler stellar evolution code. All relevant reaction rates on neutron-deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 changes in reaction rate with the highest impact were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape observables from X-ray bursts, and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.

  18. Droplet Reaction and Evaporation of Agents Model (DREAM). Glass model results; Sand model plans

    NARCIS (Netherlands)

    Hin, A.R.T.

    2006-01-01

    The Agent Fate Program is generating an extensive set of quality agent fate data which is being used to develop highly accurate secondary evaporation predictive models. Models are being developed that cover a wide range of traditional chemical warfare agents deposited onto surfaces routinely found o

  19. A GPU Reaction Diffusion Soil-Microbial Model

    Science.gov (United States)

    Falconer, Ruth; Houston, Alasdair; Schmidt, Sonja; Otten, Wilfred

    2014-05-01

    Parallelised algorithms are frequent in bioinformatics as a consequence of the close link to informatics - however in the field of soil science and ecology they are less prevalent. A current challenge in soil ecology is to link habitat structure to microbial dynamics. Soil science is therefore entering the 'big data' paradigm as a consequence of integrating data pertinent to the physical soil environment obtained via imaging and theoretical models describing growth and development of microbial dynamics permitting accurate analyses of spatio-temporal properties of different soil microenvironments. The microenvironment is often captured by 3D imaging (CT tomography) which yields large datasets and when used in computational studies the physical sizes of the samples that are amenable to computation are less than 1 cm3. Today's commodity graphics cards are programmable and possess a data parallel architecture that in many cases is capable of out-performing the CPU in terms of computational rates. The programmable aspect is achieved via a low-level parallel programming language (CUDA, OpenCL and DirectX). We ported a Soil-Microbial Model onto the GPU using the DirectX Compute API. We noted a significant computational speed up as well as an increase in the physical size that can be simulated. Some of the drawbacks of such an approach were concerned with numerical precision and the steep learning curve associated with GPGPU technologies.

  20. Neutron-induced reactions on AlF{sub 3} studied using the optical model

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chun-Wang, E-mail: machunwang@126.com [Institute of Particle and Nuclear Physics, Henan Normal University, Xinxiang 453007 (China); Lv, Cui-Juan [Institute of Particle and Nuclear Physics, Henan Normal University, Xinxiang 453007 (China); Zhang, Guo-Qiang; Wang, Hong-Wei [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zuo, Jia-Xu [Department of Nuclear and Radiation Safety Research, Nuclear and Radiation Safety Center (MEP), Beijing 100082 (China)

    2015-08-01

    Neutron-induced reactions on {sup 27}Al and {sup 19}F nuclei are investigated using the optical model implemented in the TALYS 1.4 toolkit. Incident neutron energies in a wide range from 0.1 keV to 30 MeV are calculated. The cross sections for the main channels (n, np), (n, p), (n, α), (n, 2n), and (n, γ) and the total reaction cross section (n, tot) of the reactions are obtained. When the default parameters in TALYS 1.4 are adopted, the calculated results agree with the measured results. Based on the calculated results for the n + {sup 27}Al and n + {sup 19}F reactions, the results of the n + {sup 27}Al{sup 19}F reactions are predicted. These results are useful both for the design of thorium-based molten salt reactors and for neutron activation analysis techniques.

  1. Combustion of Bimodal Nano/Micro Aluminum Suspension with New Reaction Rate Model

    Directory of Open Access Journals (Sweden)

    M. Bidabadi

    2008-01-01

    Full Text Available In this study a mathematical model for combustion of bimodal particle in lean flow was developed. The difference between structure of flame in this work and previous ones was that, in those flame was divided by five zones and reaction rate was considered to be constant in reaction zones and also zero in post flame zone. In reality it was obvious with respect to shape and size of different particles in dust, reaction didn't end suddenly. In the present research the heat loss term, which was assumed to be linearly proportional to temperature difference, was added to the energy conservation equation and reaction rate was considered proportional to available amount of fuel, leading to exponentially decreasing of reaction rate. The flame speed and temperature distribution were obtained by solving the energy equation in each zone and matching the temperature and heat flux at the interfacial boundaries. Calculated values of flame speed were in good agreement with experimental data.

  2. One-dimensional isothermal multicomponent diffusion-reaction model and its application to methanol synthesis over commercial Cu-based catalyst

    Directory of Open Access Journals (Sweden)

    Lei Kun

    2015-03-01

    Full Text Available The present work was a study on global reaction rate of methanol synthesis. We measured experimentally the global reaction rate in the internal recycle gradientless reactor over catalyst SC309. The diffusion-reaction model of methanol synthesis was suggested. For model we chose the hydrogenation of CO and CO2 as key reaction. CO and CO2 were key components in our model. The internal diffusion effectiveness factors of CO and CO2 in the catalyst were calculated by the numerical integration. A comparison with the experiment showed that all the absolute values of the relative error were less than 10%. The simulation results showed that decreasing reaction temperature and catalyst diameter were conducive to reduce the influence of the internal diffusion on the methanol synthesis.

  3. Constitutive relations for multiphase flow modeling

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, H.; Vaeth, L.; Thurnay, K. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik

    1998-01-01

    The constitutive relations that are used in the three-field fluid dynamics code IVA-KA for determining the drag in three-phase mixtures and the heat transferred by radiation are described together with some comparisons of calculational results with experiments. In these experiments (QUEOS), large quantities of solid particles are injected into water. Potential deficiencies of the present drag model are discussed. (author)

  4. A Retrospective Analysis of Spontaneous Adverse Drug Reactions Reports Relating to Paediatric Patients.

    Directory of Open Access Journals (Sweden)

    Rosliana Rosli

    Full Text Available Spontaneous reporting on adverse drug reactions (ADR has been established in Malaysia since 1987, and although these reports are monitored by the Malaysia drug monitoring authority, the National Pharmaceutical Control Bureau, information about ADRs in the paediatric patient population still remains unexplored. The aims of this study, therefore, were to characterize the ADRs reported in respect to the Malaysian paediatric population and to relate the data to specific paediatric age groups.Data on all ADRs reported to the National Pharmaceutical Control Bureau between 2000 and 2013 for individuals aged from birth to 17 years old were analysed with respect to age and gender, type of reporter, suspected medicines (using the Anatomical Therapeutic Chemical classification, category of ADR (according to system organ class as well as the severity of the ADR.In total, 11,523 ADR reports corresponding to 22,237 ADRs were analysed, with half of these reporting one ADR per report. Vaccines comprised 55.7% of the 11,523 ADR reports with the remaining being drug related ADRs. Overall, 63.9% of ADRs were reported for paediatric patients between 12 and 17 years of age, with the majority of ADRs reported in females (70.7%. The most common ADRs reported were from the following system organ classes: application site disorders (32.2%, skin and appendages disorders (20.6%, body as a whole general disorders (12.8% and central and peripheral nervous system disorders (11.2%. Meanwhile, ADRs in respect to anti-infectives for systemic use (2194/5106; 43.0% were the most frequently reported across all age groups, followed by drugs from the nervous system (1095/5106; 21.4%. Only 0.28% of the ADR cases were reported as fatal. A large proportion of the reports were received from healthcare providers in government health facilities.ADR reports concerning vaccines and anti-infectives were the most commonly reported in children, and are mainly seen in adolescents, with most of

  5. Empirical relation and establishment of shell effects in (, 2) reaction cross-sections at 14 MeV

    Indian Academy of Sciences (India)

    Sneh Lata Goyal; Pratibha Gur

    2009-02-01

    The experimental data for (, 2) reaction cross-sections around 14 MeV neutron energy have been collected from the literature and analysed for the isotopes having 1 ≤ ≤ 82. The empirical relations for the reaction cross-sections have been obtained, which show fairly good fits with the experimental values. The shell effects have been established at magic nucleon numbers for (, 2) reaction cross-sections around 14 MeV neutron energy. The odd–even effects have also been observed as the cross-sections for odd-mass nuclei are higher than their neighbouring even–even nuclei.

  6. A meson-exchange isobar model for the {pi}{sup +}d {r_reversible} pp reaction

    Energy Technology Data Exchange (ETDEWEB)

    Canton, L.; Cattapan, G.; Dortmans, P.J.; Pisent, G. [Istituto Nazionale di Fisica Nucleare, Padua (Italy); Svenne, J.P. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Physics]|[Winnipeg Inst. for Theoretical Physics, Winnipeg, MB (Canada)

    1994-10-10

    A broad set of observables are calculated for the {pi}{sup +} d {r_reversible} pp reaction with a relatively simple meson-exchange isobar model. The comparison between the calculated results and experimental data (including spin observables), shows that the model gives an overall phenomenologically acceptable description of the reaction around the {Delta} resonance. The effects due to the inclusion of Galilei invariant (pseudovector) recoil term in the {pi}NN vertex, of relativistic corrections to the {rho}-exchange component of the {Delta}N transition potential, and of NN final state interaction in the {pi}{sup +}d {yields} p+p process are also discussed. It is estimated that the model is sufficiently simple to be extended to the case of pion absorption on other light nuclei, in particular {sup 3}He (or tritium). 32 refs., 13 figs.

  7. Mathematical modeling of an exothermic leaching reaction system: pressure oxidation of wide size arsenopyrite participates

    Science.gov (United States)

    Papangelakis, V. G.; Berk, D.; Demopoulos, G. P.

    1990-10-01

    In the design of processes involving exothermic reactions, as is the case of several sulfide leaching systems, it is desirable to utilize the energy liberated by the reaction to drive the reactor toward autogenous operation. For optimal reactor design, models which couple leaching kinetics and heat effects are needed. In this paper, the principles of modeling exothermic leaching reactions are outlined. The system investigated is the high-temperature (160 °C to 200 °C) pressure (O2) oxidation of arsenopyrite (FeAsS). The reaction system is characterized by three consecutive reactions: (1) heterogeneous dissolution of arsenopyrite particles, (2) homogeneous oxidation of iron(II) to iron(III), and (3) precipitation of scorodite (FeAsO4-2H2O). The overall kinetics is controlled by the arsenopyrite surface reaction. There was good agreement between laboratory-scale batch tests and model predictions. The model was expanded to simulate the performance of large-scale batch and single-stage continuous stirred tank reactor (CSTR) for the same rate-limiting regime. Emphasis is given to the identification of steady-state temperatures for autogenous processing. The effects of operating variables, such as feed temperature, slurry density, and retention time, on reactor operation and yield of leaching products are discussed.

  8. Lattice Boltzmann Model for Numerical Relativity

    CERN Document Server

    Ilseven, E

    2015-01-01

    In the Bona-Masso formulation, Einstein equations are written as a set of flux conservative first order hyperbolic equations that resemble fluid dynamics equations. Based on this formulation, we construct a lattice Boltzmann model for Numerical Relativity. Our model is validated with well-established tests, showing good agreement with analytical solutions. Furthermore, we show that by increasing the relaxation time, we gain stability at the cost of losing accuracy, and by decreasing the lattice spacings while keeping a constant numerical diffusivity, the accuracy and stability of our simulations improves. Finally, in order to show the potential of our approach a linear scaling law for parallelisation with respect to number of CPU cores is demonstrated. Our model represents the first step in using lattice kinetic theory to solve gravitational problems.

  9. Presenting a new kinetic model for methanol to light olefins reactions over a hierarchical SAPO-34 catalyst using the Langmuir–Hinshelwood–Hougen–Watson mechanism

    Science.gov (United States)

    Javad Azarhoosh, Mohammad; Halladj, Rouein; Askari, Sima

    2017-10-01

    In this study, a new kinetic model for methanol to light olefins (MTO) reactions over a hierarchical SAPO-34 catalyst using the Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism was presented and the kinetic parameters was obtained using a genetic algorithm (GA) and genetic programming (GP). Several kinetic models for the MTO reactions have been presented. However, due to the complexity of the reactions, most reactions are considered lumped and elementary, which cannot be deemed a completely accurate kinetic model of the process. Therefore, in this study, the LHHW mechanism is presented as kinetic models of MTO reactions. Because of the non-linearity of the kinetic models and existence of many local optimal points, evolutionary algorithms (GA and GP) are used in this study to estimate the kinetic parameters in the rate equations. Via the simultaneous connection of the code related to modelling the reactor and the GA and GP codes in the MATLAB R2013a software, optimization of the kinetic models parameters was performed such that the least difference between the results from the kinetic models and experiential results was obtained and the best kinetic parameters of MTO process reactions were achieved. A comparison of the results from the model with experiential results showed that the present model possesses good accuracy.

  10. Presenting a new kinetic model for methanol to light olefins reactions over a hierarchical SAPO-34 catalyst using the Langmuir-Hinshelwood-Hougen-Watson mechanism.

    Science.gov (United States)

    Azarhoosh, Mohammad Javad; Halladj, Rouein; Askari, Sima

    2017-10-25

    In this study, a new kinetic model for methanol to light olefins (MTO) reactions over a hierarchical SAPO-34 catalyst using the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was presented and the kinetic parameters was obtained using a genetic algorithm (GA) and genetic programming (GP). Several kinetic models for the MTO reactions have been presented. However, due to the complexity of the reactions, most reactions are considered lumped and elementary, which cannot be deemed a completely accurate kinetic model of the process. Therefore, in this study, the LHHW mechanism is presented as kinetic models of MTO reactions. Because of the non-linearity of the kinetic models and existence of many local optimal points, evolutionary algorithms (GA and GP) are used in this study to estimate the kinetic parameters in the rate equations. Via the simultaneous connection of the code related to modelling the reactor and the GA and GP codes in the MATLAB R2013a software, optimization of the kinetic models parameters was performed such that the least difference between the results from the kinetic models and experiential results was obtained and the best kinetic parameters of MTO process reactions were achieved. A comparison of the results from the model with experiential results showed that the present model possesses good accuracy.

  11. Thermodynamic forward modeling of retrogressive hydration reactions induced by geofluid infiltration

    Science.gov (United States)

    Kuwatani, Tatsu; Toriumi, Mitsuhiro

    2017-01-01

    We have developed a new methodology for forward analysis of retrogressive hydration (rehydration) reactions by an improved thermodynamic forward modeling technique based on a differential thermodynamic approach (Gibbs' method). Based on natural observations and theoretical considerations, the progress of a rehydration reaction is modeled by incorporating a change in the effective bulk composition on account of the breakdown of the non-equilibrated phase and the amount of water infiltration into the system. Forward analyses of rehydration reactions under greenschist-facies conditions show that (1) the reaction progress of rehydration is proportional to the external water supply, and (2) the mineral compositions of equilibrated minerals are mainly controlled by P- T conditions and are similar to those in the global equilibrium model. Calculated results are in accordance with natural observations of rehydration reactions in greenschist-facies rocks, which supports the validity of the proposed model. The proposed model can be used as a basic forward model for various inversion analyses and numerical simulations and thus to understand the distribution and behavior of geofluids.[Figure not available: see fulltext.

  12. Stigma-related stress, shame and avoidant coping reactions among members of the general population with elevated symptom levels.

    Science.gov (United States)

    Schibalski, J V; Müller, M; Ajdacic-Gross, V; Vetter, S; Rodgers, S; Oexle, N; Corrigan, P W; Rössler, W; Rüsch, N

    2017-04-01

    It is unclear whether mental illness stigma affects individuals with subthreshold syndromes outside clinical settings. We therefore investigated the role of different stigma variables, including stigma-related stress and shame reactions, for avoidant stigma coping among members of the general population with elevated symptom levels. Based on a representative population survey, general stress resilience, stigma variables, shame about having a mental illness as well as avoidant stigma coping (secrecy and social withdrawal) were assessed by self-report among 676 participants with elevated symptom levels. Stigma variables and resilience were examined as predictors of avoidant stigma coping in a path model. Increased stigma stress was predicted by lower general stress resilience as well as by higher levels of perceived stigma, group identification and perceived legitimacy of discrimination. More shame was associated with higher perceived legitimacy. Lower resilience as well as more perceived stigma, group identification and perceived legitimacy predicted avoidant coping. Stigma stress partly mediated effects of resilience, perceived stigma and group identification on avoidant coping; shame partly mediated effects of perceived legitimacy on coping. Stigma stress and shame were also directly and positively related to avoidant stigma coping. Analyses were adjusted for symptoms, neuroticism and sociodemographic variables. Stigma may affect a larger proportion of the population than previously thought because stigma variables predicted secrecy and withdrawal among members of the general population with elevated, but overall mild symptom levels. Avoidant stigma coping likely has harmful effects, potentially exacerbating pre-existing psychological distress and undermining social networks. This highlights the need to reduce public stigma as well as to support individuals with subthreshold syndromes in their coping with stigma stress and shame reactions. Copyright © 2017

  13. Geochemical modeling of diagenetic reactions in Snorre Field reservoir sandstones: a comparative study of computer codes

    Directory of Open Access Journals (Sweden)

    Marcos Antonio Klunk

    Full Text Available ABSTRACTDiagenetic reactions, characterized by the dissolution and precipitation of minerals at low temperatures, control the quality of sedimentary rocks as hydrocarbon reservoirs. Geochemical modeling, a tool used to understand diagenetic processes, is performed through computer codes based on thermodynamic and kinetic parameters. In a comparative study, we reproduced the diagenetic reactions observed in Snorre Field reservoir sandstones, Norwegian North Sea. These reactions had been previously modeled in the literature using DISSOL-THERMAL code. In this study, we modeled the diagenetic reactions in the reservoirs using Geochemist's Workbench (GWB and TOUGHREACT software, based on a convective-diffusive-reactive model and on the thermodynamic and kinetic parameters compiled for each reaction. TOUGHREACT and DISSOL-THERMAL modeling showed dissolution of quartz, K-feldspar and plagioclase in a similar temperature range from 25 to 80°C. In contrast, GWB modeling showed dissolution of albite, plagioclase and illite, as well as precipitation of quartz, K-feldspar and kaolinite in the same temperature range. The modeling generated by the different software for temperatures of 100, 120 and 140°C showed similarly the dissolution of quartz, K-feldspar, plagioclase and kaolinite, but differed in the precipitation of albite and illite. At temperatures of 150 and 160°C, GWB and TOUGHREACT produced different results from the DISSOL-THERMAL, except for the dissolution of quartz, plagioclase and kaolinite. The comparative study allows choosing the numerical modeling software whose results are closer to the diagenetic reactions observed in the petrographic analysis of the modeled reservoirs.

  14. Generative models: Human embryonic stem cells and multiple modeling relations.

    Science.gov (United States)

    Fagan, Melinda Bonnie

    2016-04-01

    Model organisms are at once scientific models and concrete living things. It is widely assumed by philosophers of science that (1) model organisms function much like other kinds of models, and (2) that insofar as their scientific role is distinctive, it is in virtue of representing a wide range of biological species and providing a basis for generalizations about those targets. This paper uses the case of human embryonic stem cells (hESC) to challenge both assumptions. I first argue that hESC can be considered model organisms, analogous to classic examples such as Escherichia coli and Drosophila melanogaster. I then discuss four contrasts between the epistemic role of hESC in practice, and the assumptions about model organisms noted above. These contrasts motivate an alternative view of model organisms as a network of systems related constructively and developmentally to one another. I conclude by relating this result to other accounts of model organisms in recent philosophy of science. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Monte Carlo analysis of uncertainty propagation in a stratospheric model. 2: Uncertainties due to reaction rates

    Science.gov (United States)

    Stolarski, R. S.; Butler, D. M.; Rundel, R. D.

    1977-01-01

    A concise stratospheric model was used in a Monte-Carlo analysis of the propagation of reaction rate uncertainties through the calculation of an ozone perturbation due to the addition of chlorine. Two thousand Monte-Carlo cases were run with 55 reaction rates being varied. Excellent convergence was obtained in the output distributions because the model is sensitive to the uncertainties in only about 10 reactions. For a 1 ppby chlorine perturbation added to a 1.5 ppby chlorine background, the resultant 1 sigma uncertainty on the ozone perturbation is a factor of 1.69 on the high side and 1.80 on the low side. The corresponding 2 sigma factors are 2.86 and 3.23. Results are also given for the uncertainties, due to reaction rates, in the ambient concentrations of stratospheric species.

  16. Dynamic Analysis of a Reaction-Diffusion Rumor Propagation Model

    Science.gov (United States)

    Zhao, Hongyong; Zhu, Linhe

    2016-06-01

    The rapid development of the Internet, especially the emergence of the social networks, leads rumor propagation into a new media era. Rumor propagation in social networks has brought new challenges to network security and social stability. This paper, based on partial differential equations (PDEs), proposes a new SIS rumor propagation model by considering the effect of the communication between the different rumor infected users on rumor propagation. The stabilities of a nonrumor equilibrium point and a rumor-spreading equilibrium point are discussed by linearization technique and the upper and lower solutions method, and the existence of a traveling wave solution is established by the cross-iteration scheme accompanied by the technique of upper and lower solutions and Schauder’s fixed point theorem. Furthermore, we add the time delay to rumor propagation and deduce the conditions of Hopf bifurcation and stability switches for the rumor-spreading equilibrium point by taking the time delay as the bifurcation parameter. Finally, numerical simulations are performed to illustrate the theoretical results.

  17. Squatting-Related Tibiofemoral Shear Reaction Forces and a Biomechanical Rationale for Femoral Component Loosening

    Directory of Open Access Journals (Sweden)

    Ashvin Thambyah

    2014-01-01

    Full Text Available Previous gait studies on squatting have described a rapid reversal in the direction of the tibiofemoral joint shear reaction force when going into a full weight-bearing deep knee flexion squat. The effects of such a shear reversal have not been considered with regard to the loading demand on knee implants in patients whose activities of daily living require frequent squatting. In this paper, the shear reversal effect is discussed and simulated in a finite element knee implant-bone model, to evaluate the possible biomechanical significance of this effect on femoral component loosening of high flexion implants as reported in the literature. The analysis shows that one of the effects of the shear reversal was a switch between large compressive and large tensile principal strains, from knee extension to flexion, respectively, in the region of the anterior flange of the femoral component. Together with the known material limits of cement and bone, this large mismatch in strains as a function of knee position provides new insight into how and why knee implants may fail in patients who perform frequent squatting.

  18. Structures and reaction mechanisms of the two related enzymes, PurN and PurU.

    Science.gov (United States)

    Sampei, Gen-ichi; Kanagawa, Mayumi; Baba, Seiki; Shimasaki, Toshiaki; Taka, Hiroyuki; Mitsui, Shohei; Fujiwara, Shinji; Yanagida, Yuki; Kusano, Mayumi; Suzuki, Sakiko; Terao, Kayoko; Kawai, Hiroya; Fukai, Yoko; Nakagawa, Noriko; Ebihara, Akio; Kuramitsu, Seiki; Yokoyama, Shigeyuki; Kawai, Gota

    2013-12-01

    The crystal structures of glycinamide ribonucleotide transformylases (PurNs) from Aquifex aeolicus (Aa), Geobacillus kaustophilus (Gk) and Symbiobacterium toebii (St), and of formyltetrahydrofolate hydrolase (PurU) from Thermus thermophilus (Tt) were determined. The monomer structures of the determined PurN and PurU were very similar to the known structure of PurN, but oligomeric states were different; AaPurN and StPurN formed dimers, GkPurN formed monomer and PurU formed tetramer in the crystals. PurU had a regulatory ACT domain in its N-terminal side. So far several structures of PurUs have been determined, yet, the mechanisms of the catalysis and the regulation of PurU have not been elucidated. We, therefore, modelled ligand-bound structures of PurN and PurU, and performed molecular dynamics simulations to elucidate the reaction mechanisms. The evolutionary relationship of the two enzymes is discussed based on the comparisons of the structures and the catalytic mechanisms.

  19. Combustion of Bimodal Nano/Micro Aluminum Suspension with New Reaction Rate Model

    OpenAIRE

    M. Bidabadi; N. Moallemi; I. Shafieenejad; M. Jadidi

    2008-01-01

    In this study a mathematical model for combustion of bimodal particle in lean flow was developed. The difference between structure of flame in this work and previous ones was that, in those flame was divided by five zones and reaction rate was considered to be constant in reaction zones and also zero in post flame zone. In reality it was obvious with respect to shape and size of different particles in dust, reaction didn't end suddenly. In the present research the heat loss term, which was as...

  20. The mineralogic evolution of the Martian surface through time: Implications from chemical reaction path modeling studies

    Science.gov (United States)

    Plumlee, G. S.; Ridley, W. I.; Debraal, J. D.; Reed, M. H.

    1993-01-01

    Chemical reaction path calculations were used to model the minerals that might have formed at or near the Martian surface as a result of volcano or meteorite impact driven hydrothermal systems; weathering at the Martian surface during an early warm, wet climate; and near-zero or sub-zero C brine-regolith reactions in the current cold climate. Although the chemical reaction path calculations carried out do not define the exact mineralogical evolution of the Martian surface over time, they do place valuable geochemical constraints on the types of minerals that formed from an aqueous phase under various surficial and geochemically complex conditions.

  1. Catalytic conversion reactions in nanoporous systems with concentration-dependent selectivity: Statistical mechanical modeling

    Science.gov (United States)

    García, Andrés; Wang, Jing; Windus, Theresa L.; Sadow, Aaron D.; Evans, James W.

    2016-05-01

    Statistical mechanical modeling is developed to describe a catalytic conversion reaction A →Bc or Bt with concentration-dependent selectivity of the products, Bc or Bt, where reaction occurs inside catalytic particles traversed by narrow linear nanopores. The associated restricted diffusive transport, which in the extreme case is described by single-file diffusion, naturally induces strong concentration gradients. Furthermore, by comparing kinetic Monte Carlo simulation results with analytic treatments, selectivity is shown to be impacted by strong spatial correlations induced by restricted diffusivity in the presence of reaction and also by a subtle clustering of reactants, A .

  2. Negative reactions of men to the loss of power in gender relations: Lilith vs. Eve

    Directory of Open Access Journals (Sweden)

    Miguel Moya

    2012-01-01

    Full Text Available This paper examines the reaction of the man when he sees he is losing power and authority over a woman and it relation with men’s sexist ideology. 83 men participated in the study and were led to believe they were interacting via computer with a woman, and answered a decision-making task about family relationships. All of them were assigned the role of someone with authority and power. In half the cases, the woman accepted the man's decisions, and, in the other half, she did not accept. The results showed that when woman did not accept the decisions of the man, she was perceived more negatively. Moreover, the more hostile sexist participants were, the more they rated negatively their female partner, especially when the woman did not accept their decisions. Hostile sexism acts as a corrective tool against those women who defy the traditionally higher status accorded to men. The valuation that woman receive in their interaction with man is determined by what man feel threatened. These results are of great interest in the field of gender violence, since it is one more step towards explaining why some men use violence to attempt to regain their threatened or lost power.

  3. J/$\\psi$ azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon

    CERN Document Server

    Prino, F; Alexa, C; Arnaldi, R; Atayan, M; Beolè, S; Boldea, V; Bordalo, P; Borges, G; Castanier, C; Castor, J; Chaurand, B; Cheynis, B; Chiavassa, E; Cicalo, C; Comets, M P; Constantinescu, S; Cortese, P; De Falco, A; De Marco, N; Dellacasa, G; Devaux, A; Dita, S; Fargeix, J; Force, P; Gallio, M; Gerschel, C; Giubellino, P; Golubeva, M B; Grigoryan, A A; Grigoryan, S; Guber, F F; Guichard, A; Gulkanyan, H; Idzik, M; Jouan, D; Karavicheva, T L; Kluberg, L; Kurepin, A B; Le Bornec, Y; Lourenço, C; Mac Cormick, M; Marzari-Chiesa, A; Masera, M; Masoni, A; Monteno, M; Musso, A; Petiau, P; Piccotti, A; Pizzi, J R; Puddu, G; Quintans, C; Ramello, L; Ramos, S; Riccati, L; Santos, H; Saturnini, P; Scomparin, E; Serci, S; Shahoyan, R; Sigaudo, F; Sitta, M; Sonderegger, P; Tarrago, X; Topilskaya, N S; Usai, G L; Vercellin, E; Villatte, L; Willis, N; Wu, T

    2009-01-01

    The J/$\\psi$ azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/$\\psi$ mesons at SPS energies. Hence, the measurement of J/$\\psi$ elliptic anisotropy, quantified by the Fourier coefficient v$_2$ of the J/$\\psi$ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/$\\psi$ suppression observed in Pb-Pb collisions. We present the measured J/$\\psi$ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v$_{2}$ as a function of the collision centrality and of the J/$\\psi$ transverse momentum. The reaction plane has been estimated from the azimuthal distribution of the ...

  4. Extension of the Li\\`ege Intranuclear-Cascade model to reactions induced by light nuclei

    CERN Document Server

    Mancusi, Davide; Cugnon, Joseph; David, Jean-Christophe; Kaitaniemi, Pekka; Leray, Sylvie

    2014-01-01

    The purpose of this paper is twofold. First, we present the extension of the Li\\`ege Intranuclear Cascade model to reactions induced by light ions. Second, we describe the C++ version of the code, which it is physics-wise equivalent to the legacy version, is available in Geant4 and will serve as the basis for all future development of the model. We describe the ideas upon which we built our treatment of nucleus-nucleus reactions and we compare the model predictions against a vast set of heterogeneous experimental data. In spite of the discussed limitations of the intranuclear-cascade scheme, we find that our model yields valid predictions for a number of observables and positions itself as one of the most attractive alternatives available to Geant4 users for the simulation of light-ion-induced reactions.

  5. Optimal Homotopy Asymptotic Solution for Exothermic Reactions Model with Constant Heat Source in a Porous Medium

    Directory of Open Access Journals (Sweden)

    Fazle Mabood

    2015-01-01

    Full Text Available The heat flow patterns profiles are required for heat transfer simulation in each type of the thermal insulation. The exothermic reaction models in porous medium can prescribe the problems in the form of nonlinear ordinary differential equations. In this research, the driving force model due to the temperature gradients is considered. A governing equation of the model is restricted into an energy balance equation that provides the temperature profile in conduction state with constant heat source on the steady state. The proposed optimal homotopy asymptotic method (OHAM is used to compute the solutions of the exothermic reactions equation.

  6. Numerical aspects of modelling of coupled chemical reactions and fluid flow in sedimentary basins

    Energy Technology Data Exchange (ETDEWEB)

    Holstad, Astrid

    1998-01-01

    Simulation of coupled chemical reactions and fluid flow in porous sedimentary basins, through long time periods, is a numerical challenge. In most models available today the equations representing such a physical problem are solved as PDEs (Partial Differential Equation) where efficient time-stepping with controlled error is very difficult. The DAE (Differential Algebraic Equation) system approach is used where robust adaptive time-stepping algorithms are available in solvers. In this report mathematical and numerical models are derived for coupled chemical reactions and fluid flow. The models have several interesting properties which are discussed. The performance of code is tested. 20 refs., 6 figs., 2 tabs.

  7. Reactions of aqueous chlorine and chlorine dioxide with model food compounds.

    OpenAIRE

    Fukayama, M Y; Tan, H; Wheeler, W B; Wei, C I

    1986-01-01

    Chlorine and chlorine dioxide (ClO2), common disinfecting and bleaching chemicals used in the food industry, are potent oxidizing and chlorinating agents. Unfortunately, little is known about the nature of the reactions of chlorine with organic food constituents. This presentation reviews published information concerning the reactions of chlorine gas (Cl2[g]), aqueous chlorine, and ClO2 with model food compounds, the fate of chlorine during the chlorination of specific food products, and the ...

  8. Modified landfill gas generation rate model of first-order kinetics and two-stage reaction

    Institute of Scientific and Technical Information of China (English)

    Jiajun CHEN; Hao WANG; Na ZHANG

    2009-01-01

    This investigation was carried out to establish a new domestic landfill gas (LFG) generation rate model that takes into account the impact ofleachate recirculation. The first-order kinetics and two-stage reaction (FKTSR) model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages. In this study, the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate. Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model. The model calibration was then calculated by using the experimental data. The results suggested that the new model was in line with the experimental data. The main parameters of the modified FKTSR model, including the LFG production potential (L0), the reaction rate constant in the first stage (K1), and the reaction rate constant in the second stage (K2) of 64.746 L, 0.202 d-1, and 0.338 d-1,respectively, were comparable to the old ones of 42.069 L,0.231 d-1, and 0.231 d-1. The new model is better able to explain the mechanisms involved in LFG generation.

  9. The modelling of counter-rotating twin screw extruders as reactors for single-component reactions

    NARCIS (Netherlands)

    Ganzeveld, K.J.; Capel, J.E.; Wal, D.J. van der; Janssen, L.P.B.M.

    1994-01-01

    Numerical models are useful to study the behaviour of the extruder as a polymerization reactor. With a correct numerical model a theoretical analysis of the influence of several reaction and extruder parameters can be made, the limitations of the use of the extruder reactor can be determined and the

  10. A model for the [gamma]p[yields][pi][sup +][pi][sup -]p reactions

    Energy Technology Data Exchange (ETDEWEB)

    Gomez Tejedor, J.A. (Dept. de Fisica Teorica, Centro Mixto Universidad de Valencia-CSIC, Burjassot (Spain) IFIC, Centro Mixto Universidad de Valencia-CSIC, Burjassot (Spain)); Oset, E. (Dept. de Fisica Teorica, Centro Mixto Universidad de Valencia-CSIC, Burjassot (Spain) IFIC, Centro Mixto Universidad de Valencia-CSIC, Burjassot (Spain))

    1994-05-09

    We have studied the [gamma]p[yields][pi][sup +][pi][sup -]p reaction using a model which includes N, [Delta](1232), N[sup *](1440) and N[sup *](1520) intermediate baryonic states and the [rho]-meson as intermediate 2[pi]-resonance. The model reproduces fairly well experimental cross sections below E[sub [gamma

  11. Bifurcation Analysis of Gene Propagation Model Governed by Reaction-Diffusion Equations

    Directory of Open Access Journals (Sweden)

    Guichen Lu

    2016-01-01

    Full Text Available We present a theoretical analysis of the attractor bifurcation for gene propagation model governed by reaction-diffusion equations. We investigate the dynamical transition problems of the model under the homogeneous boundary conditions. By using the dynamical transition theory, we give a complete characterization of the bifurcated objects in terms of the biological parameters of the problem.

  12. A kinetic model for the glucose/glycine Maillard reaction pathways

    NARCIS (Netherlands)

    Martins, S.I.F.S.; Boekel, van M.A.J.S.

    2005-01-01

    A comprehensive kinetic model for the glucose/glycine Maillard reaction is proposed based on an approach called multiresponse kinetic modelling. Special attention was paid to reactants, intermediates and end products: -fructose, N-(1-deoxy--fructos-1-yl)-glycine (DFG), 1-deoxy-2,3-hexodiulose and

  13. The modelling of counter-rotating twin screw extruders as reactors for single-component reactions

    NARCIS (Netherlands)

    Ganzeveld, K.J.; Capel, J.E.; Wal, D.J. van der; Janssen, L.P.B.M.

    1994-01-01

    Numerical models are useful to study the behaviour of the extruder as a polymerization reactor. With a correct numerical model a theoretical analysis of the influence of several reaction and extruder parameters can be made, the limitations of the use of the extruder reactor can be determined and the

  14. A discrete solvent reaction field model for calculating molecular linear response properties in solution

    NARCIS (Netherlands)

    Jensen, L; van Duijnen, PT; Snijders, JG

    2003-01-01

    A discrete solvent reaction field model for calculating frequency-dependent molecular linear response properties of molecules in solution is presented. The model combines a time-dependent density functional theory (QM) description of the solute molecule with a classical (MM) description of the discr

  15. Models for identification of erroneous atom-to-atom mapping of reactions performed by automated algorithms.

    Science.gov (United States)

    Muller, Christophe; Marcou, Gilles; Horvath, Dragos; Aires-de-Sousa, João; Varnek, Alexandre

    2012-12-21

    Machine learning (SVM and JRip rule learner) methods have been used in conjunction with the Condensed Graph of Reaction (CGR) approach to identify errors in the atom-to-atom mapping of chemical reactions produced by an automated mapping tool by ChemAxon. The modeling has been performed on the three first enzymatic classes of metabolic reactions from the KEGG database. Each reaction has been converted into a CGR representing a pseudomolecule with conventional (single, double, aromatic, etc.) bonds and dynamic bonds characterizing chemical transformations. The ChemAxon tool was used to automatically detect the matching atom pairs in reagents and products. These automated mappings were analyzed by the human expert and classified as "correct" or "wrong". ISIDA fragment descriptors generated for CGRs for both correct and wrong mappings were used as attributes in machine learning. The learned models have been validated in n-fold cross-validation on the training set followed by a challenge to detect correct and wrong mappings within an external test set of reactions, never used for learning. Results show that both SVM and JRip models detect most of the wrongly mapped reactions. We believe that this approach could be used to identify erroneous atom-to-atom mapping performed by any automated algorithm.

  16. Modelling of chalcopyrite oxidation reactions in the Outokumpu flash smelting process

    Energy Technology Data Exchange (ETDEWEB)

    Ahokainen, T.; Jokilaakso, A. [Helsinki Univ. of Technology, Otaniemi (Finland)

    1996-12-31

    A mathematical model for simulating oxidation reactions of chalcopyrite particles together with momentum, heat and mass transfer between particle and gas phase in a flash smelting furnace reaction shaft is presented. In simulation, the equations governing the gas flow are solved numerically with a commercial fluid flow package, Phoenics. The particle phase is introduced into the gas flow by a Particle Source In Cell (PSIC) - technique, where a number of discrete particles is tracked in a gas flow and the relevant source terms for momentum, mass, and heat transfer are added to the gas phase equations. The gas phase equations used are elliptic in nature and the fluid turbulence is described by the (k-{epsilon}) -model. Thermal gas phase radiation is simulated with a six-flux radiation model. The chemical reactions of concentrate particles are assumed to happen at two sharp interfaces, and a shrinking core model is applied to describe the mass transfer of chemical species through the reaction product layer. In a molten state, the oxygen consumption is controlled by a film penetration concept. The reacting concentrate particles are a mixture of chalcopyrite and silica. Also a certain amount of pure inert silica is fed to the process as flux. In the simulations the calculation domain includes the concentrate burner and a cylindrical reaction shaft of an industrial scale flash smelting furnace. Some examples about the simulations carried out by the combustion model are presented. (author)

  17. THE ASYMPTOTIC LIMIT FOR A COMBUSTION MODEL IN REGARD TO INFINITE REACTION RATE

    Institute of Scientific and Technical Information of China (English)

    Ying Longan

    2008-01-01

    The Zeldovich-von Neumann-Doring model and the Chapman-Jouguet model for a simplified combustion model-Majda's model is studied. The author proves a uniform maximum norm estimate, then proves that as the rate of chemical reaction tends to infinity the solutions to the Zeldovich-von Neumann-Doring model tend to that of the Chapman-Jouguet model. The type of combustion waves is studied. This result is compared with the result of the projection and finite difference method for the same model.

  18. Transient kinetics of electron transfer reactions of flavodoxin: ionic strength dependence of semiquinone oxidation by cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid and computer modeling of reaction complexes.

    Science.gov (United States)

    Simondsen, R P; Weber, P C; Salemme, F R; Tollin, G

    1982-12-07

    Electron transfer reactions between Clostridum pasteurianum flavodoxin semiquinone and various oxidants [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid (EDTA)] have been studied as a function of ionic strength by using stopped-flow spectrophotometry. The cytochrome c reaction is complicated by the existence of two cytochrome species which react at different rates and whose relative concentrations are ionic strength dependent. Only the faster of these two reactions is considered here. At low ionic strength, complex formation between cytochrome c and flavodoxin is indicated by a leveling off of the pseudo-first-order rate constant at high cytochrome c concentration. This is not observed for either ferricyanide or ferric EDTA. For cytochrome c, the rate and association constants for complex formation were found to increase with decreasing ionic strength, consistent with negative charges on flavodoxin interacting with the positively charged cytochrome electron transfer site. Both ferricyanide and ferric EDTA are negatively charged oxidants, and the rate data respond to ionic strength changes as would be predicted for reactants of the same charge sign. These results demonstrate that electrostatic interactions involving negatively charged groups are important in orienting flavodoxin with respect to oxidants during electron transfer. We have also carried out computer modeling studies of putative complexes of flavodoxin with cytochrome c and ferricyanide, which relate their structural properties to both the observed kinetic behavior and some more general features of physiological electron transfer processes. The results of this study are consistent with the ionic strength behavior described above.

  19. Image guided personalization of reaction-diffusion type tumor growth models using modified anisotropic eikonal equations.

    Science.gov (United States)

    Konukoglu, Ender; Clatz, Olivier; Menze, Bjoern H; Stieltjes, Bram; Weber, Marc-André; Mandonnet, Emmanuel; Delingette, Hervé; Ayache, Nicholas

    2010-01-01

    Reaction-diffusion based tumor growth models have been widely used in the literature for modeling the growth of brain gliomas. Lately, recent models have started integrating medical images in their formulation. Including different tissue types, geometry of the brain and the directions of white matter fiber tracts improved the spatial accuracy of reaction-diffusion models. The adaptation of the general model to the specific patient cases on the other hand has not been studied thoroughly yet. In this paper, we address this adaptation. We propose a parameter estimation method for reaction-diffusion tumor growth models using time series of medical images. This method estimates the patient specific parameters of the model using the images of the patient taken at successive time instances. The proposed method formulates the evolution of the tumor delineation visible in the images based on the reaction-diffusion dynamics; therefore, it remains consistent with the information available. We perform thorough analysis of the method using synthetic tumors and show important couplings between parameters of the reaction-diffusion model. We show that several parameters can be uniquely identified in the case of fixing one parameter, namely the proliferation rate of tumor cells. Moreover, regardless of the value the proliferation rate is fixed to, the speed of growth of the tumor can be estimated in terms of the model parameters with accuracy. We also show that using the model-based speed, we can simulate the evolution of the tumor for the specific patient case. Finally, we apply our method to two real cases and show promising preliminary results.

  20. Study of apoptosis in skin lesions of leprosy in relation to treatment and lepra reactions.

    Science.gov (United States)

    Ajith, C; Gupta, Sachin; Radotra, Bishan D; Arora, Sunil K; Kumar, Bhushan; Dogra, Sunil; Kaur, Inderjeet

    2005-12-01

    In leprosy on treatment, one factor contributing to the healing of skin lesions with minimal fibrosis may be apoptosis of inflammatory cells, even though apoptosis is sparse in leprosy as compared to tuberculosis. The degree of apoptosis in skin lesions of leprosy was studied by histopathologic examination (HPE) and by DNA fragmentation and electrophoresis. The effect of various parameters on apoptosis was noted in untreated disease, during treatment at 3 and 6 months, and in lepra reactions in different parts of the spectrum of leprosy. Of the 31 patients, 13 had paucibacillary (PB) and 18 multibacillary (MB) disease. Twenty one patients were in reaction: 16 had type 1 reaction and 5 had type 2 reaction. The controls included patients with non-granulomatous skin diseases; there were no normal controls, and no separate controls for cases with reaction. Apoptosis occurred more frequently in patients with leprosy as compared to the controls. In both PB & MB lesions, apoptosis was observed to increase progressively with treatment at 3 and 6 months, and was more prominent in the MB cases at 6 months of treatment. When lesions in either type 1 or type 2 reaction were compared to lesions not in reaction, a significant increase in apoptosis (p = 0.014) was found only in lesions with type 2 reaction and those which were at 6 months of treatment. The type of treatment regimen, or oral steroids given for reactions, did not significantly alter the degree of apoptosis. Our observations indicate that increased apoptosis is present in leprosy lesions and that in leprosy it progressively increases with anti-leprosy treatment up to 6 months. If the process of apoptosis in skin lesions is followed up for a longer period of time, the degree of apoptosis may be expected to decline. The study of apoptosis may help to understand the mechanism of clearance of bacilli and resolution of granulomas in leprosy patients.

  1. Lattice Boltzmann model for numerical relativity.

    Science.gov (United States)

    Ilseven, E; Mendoza, M

    2016-02-01

    In the Z4 formulation, Einstein equations are written as a set of flux conservative first-order hyperbolic equations that resemble fluid dynamics equations. Based on this formulation, we construct a lattice Boltzmann model for numerical relativity and validate it with well-established tests, also known as "apples with apples." Furthermore, we find that by increasing the relaxation time, we gain stability at the cost of losing accuracy, and by decreasing the lattice spacings while keeping a constant numerical diffusivity, the accuracy and stability of our simulations improve. Finally, in order to show the potential of our approach, a linear scaling law for parallelization with respect to number of CPU cores is demonstrated. Our model represents the first step in using lattice kinetic theory to solve gravitational problems.

  2. Relation between the complex Ginzburg-Landau equation and reaction-diffusion System

    Institute of Scientific and Technical Information of China (English)

    Shao Xin; Ren Yi; Ouyang Qi

    2006-01-01

    The complex Ginzburg-Landau equation(CGLE)has been used to describe the travelling wave behaviour in reaction-diffusion (RD) systems. We argue that this description is valid only when the RD system is close to the Hopf bifurcation,and is not valid when a RD system is away from the onset.To test this,we study spirals and anti-spirals in the chlorite-iodide-malonic acid (CIMA) reaction and the corresponding CGLE.Numerical simulations confirm that the CGLE can only be applied to the CIMA reaction when it is very near the Hopf onset.

  3. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems

    Science.gov (United States)

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-07-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  4. Phase transitions in a holographic s + p model with back-reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Zhang-Yu [Kunming University of Science and Technology, Kunming (China); Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Shanghai Jiao Tong University, INPAC, Department of Physics, and Shanghai Key Laboratory of Particle Physics and Cosmology, Shanghai (China); Cai, Rong-Gen [Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Gao, Xin [Virginia Tech, Department of Physics, Blacksburg, VA (United States); Li, Li [University of Crete, Department of Physics, Crete Center for Theoretical Physics, Heraklion (Greece); Zeng, Hui [Kunming University of Science and Technology, Kunming (China); Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China)

    2015-11-15

    In a previous paper (Nie et al. in JHEP 1311:087, arXiv:1309.2204 [hep-th], 2013), we presented a holographic s + p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. We also study the competition and coexistence of the s-wave and p-wave orders in the probe limit. In this work we continue to study the model by considering the full back-reaction. The model shows a rich phase structure and various condensate behaviors such as the ''n-type'' and ''u-type'' ones, which are also known as reentrant phase transitions in condensed matter physics. The phase transitions to the p-wave phase or s + p coexisting phase become first order in strong back-reaction cases. In these first order phase transitions, the free energy curve always forms a swallow tail shape, in which the unstable s + p solution can also play an important role. The phase diagrams of this model are given in terms of the dimension of the scalar order and the temperature in the cases of eight different values of the back-reaction parameter, which show that the region for the s + p coexisting phase is enlarged with a small or medium back-reaction parameter but is reduced in the strong back-reaction cases. (orig.)

  5. Extended kinetic model of real-time polymerase chain reaction process

    Science.gov (United States)

    Fedorov, A. A.; Sochivko, D. G.; Varlamov, D. A.; Kurochkin, V. E.

    2016-11-01

    Real-time polymerase chain reaction (real-time PCR) is the main molecular genetic method used for qualitative and quantitative analysis of specific nucleic acid sequences in many areas of biomedical research. Theoretical study of pCr models allows to estimate the influence of various reaction components and parameters, and to determine the unknown parameter values by approximating the experimental real-time PCR curves. An extended kinetic model of real-time PCR is presented. The model takes into account the enzyme activity based on Michaelis-Menten kinetics, the hybridization of complementary DNA fragments, the presence of a fluorescent probe used for detection of the reaction products, and the temperature dependence of primers and probe hybridization.

  6. Random incidence absorption coefficients of porous absorbers based on local and extended reaction models

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2011-01-01

    resistivity doubles, a decrease in the required thickness by 25 mm is observed to achieve the same amount of error. For an absorber backed by an air gap, the thickness ratio between the material and air cavity is important. If the absorber thickness is approximately 40% of the cavity depth, the local reaction...... resistivity and the absorber thickness on the difference between the two surface reaction models are examined and discussed. For a porous absorber backed by a rigid surface, the local reaction models give errors of less than 10% if the thickness exceeds 120 mm for a flow resistivity of 5000 Nm-4s. As the flow...... models give errors below 10% even for a low flow resistivity case....

  7. Mode specificity and product energy disposal in unimolecular reactions: insights from the sudden vector projection model.

    Science.gov (United States)

    Li, Jun; Guo, Hua

    2014-04-03

    A simple model is proposed to predict mode specificity and product energy disposal in unimolecular dissociation reactions. This so-called Sudden Vector Projection (SVP) model quantifies the coupling of a reactant or product mode with the reaction coordinate at the transition state by projecting the corresponding normal mode vector onto the imaginary frequency mode at the saddle point. Due to the sudden assumption, SVP predictions for mode specificity are expected to be valid only when the reactant molecule has weak intermodal coupling. On the other hand, the sudden limit is generally satisfied for its predictions of product energy disposal in unimolecular reactions with a tight barrier. The SVP model is applied to several prototypical systems and the agreement with available experimental and theoretical results is satisfactory.

  8. TEOS-based SiO{sub 2} chemical vapor deposition: Reaction kinetics and related surface chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Bartram, M.E.; Moffat, H.K.

    1995-11-01

    We have developed a comprehensive understanding of thermal TEOS (tetracthylorthosificate, Si(OCH{sub 2}CH{sub 3}){sub 4}) surface chemistry at CVD (chemical vapor deposition) temperatures and pressures. This was accomplished by examining how TEOS reaction rate are influenced by factors critical to the heterogeneous reaction. This includes determining the TEOS pressure dependence, testing if reaction by-products inhibit TEOS decomposition, identifying reaction sites on the surface, and establishing the reaction sites coverage dependencies. We evaluated the pressure dependencies and by-product inhibition with GCMS. The experiments in a cold-wall research reactor revealed that the TEOS surface reaction at 1000K (1) was first-order with respect to TEOS pressure (0.10 to 1.50Torr) and (2) was not inhibited by surface reaction by-products (ethylene, ethanol, and water). Reactivities of surface sites and their coverage dependencies were compared with FTIR. Our experiments demonstrated that two-membered siloxane ((Si-O){sub 2}) rings on the SiO{sub 2} surface were consumed almost instantaneously when exposed to TEOS. Our FTIR experiments also revealed that TEOS decomposition was zero-order with respect to coverages of hydroxyl groups and (by indirect evidence) three-membered siloxane ((Si-O){sub 3}) rings. This type of site-independent reactivity is consistent with TEOS reacting with hydroxyl groups and (Si-O){sub 3} rings via a common rate-determining step at 1000K. With respect to deposition uniformity, our results predict that deposition rates will be insensitive to the relative coverages of (Si-O){sub 3} rings and hydroxyls on SiO{sub 2} as well as the re-adsorbed by-products of the surface reaction. Therefore, it is likely that nonuniform SiO{sub 2} depositions from TEOS reactions are due to depletion of TEOS in the gas-phase and/or thermal gradients.

  9. The Role of Psychological Stress Reactions in the Longitudinal Relation Between Workplace Bullying and Turnover

    DEFF Research Database (Denmark)

    Nabe-Nielsen, Kirsten; Grynderup, Matias Brødsgaard; Conway, Paul Maurice

    2017-01-01

    OBJECTIVES: To investigate the association between workplace bullying and change of job/unemployment, and to investigate whether psychological stress reactions constitute a potential pathway linking workplace bullying and change of job/unemployment. METHODS: We used questionnaire data on workplace...... bullying and psychological stress reactions and register data on change of job/unemployment. We applied a multiple pathway approach to estimate the proportion of the association between workplace bullying and subsequent change of job/unemployment that was potentially mediated by psychological stress...... reactions. RESULTS: Workplace bullying was associated with risk of change of job (odds ratio [OR] = 1.35; 95% confidence interval [CI]: 1.06-1.72; 24% potentially mediated by psychological stress reactions) and unemployment (OR = 4.90; 95% CI: 3.18-7.55; 19% potentially mediated by psychological stress...

  10. Effects of midazolam and phenobarbital on brain oxidative reactions induced by pentylenetetrazole in a convulsion model.

    Science.gov (United States)

    Arai, Yukiko; Maeda, Shigeru; Higuchi, Hitoshi; Tomoyasu, Yumiko; Shimada, Masahiko; Miyawaki, Takuya

    2012-04-01

    Brain oxidative reactions are involved in epilepsy as well as neurodegenerative diseases. In animal convulsion models, some anticonvulsants have been found to suppress oxidative reactions associated with convulsions. However, the effect of anticonvulsants on brain oxidative reactions has not fully been clarified. Midazolam and phenobarbital are often used as an intravenous anesthetic, and are known to have anticonvulsive effect, but antioxidative effect of these drugs has rarely been studied. Thus, the purpose of this study was to evaluate the effects of these drugs on the degree of convulsions and brain oxidative reactions in an animal convulsion model. In order to evaluate brain oxidative reactions, we measured malondialdehyde (MDA) level and heme oxygenase (HO)-1 mRNA expression level in the brain of mice in a convulsion model generated by a single injection of pentylenetetrazole (PTZ). We evaluated the effects of midazolam and phenobarbital on the degree of PTZ-induced convulsions and on the changes in brain MDA level and HO-1 mRNA expression level. After PTZ injection, severe convulsions were observed in all mice. MDA level was increased in the whole brain, while HO-1 mRNA expression level was increased only in the hippocampus. Both midazolam and phenobarbital prevented the convulsions and suppressed the increase in both MDA level and HO-1 mRNA expression level in the brain. In this study, both midazolam and phenobarbital suppressed PTZ-induced MDA and HO-1 reactions in the brain, suggesting that these drugs inhibit brain oxidative reactions in a convulsion model.

  11. [Age-related dynamics of the motion reaction in school children].

    Science.gov (United States)

    Makarenko, M V; Petrenko, Iu O; Baĭda, O H; Men'shykh, O E

    2009-01-01

    We studied functional state of the central nervous system of boys and girls aged from 7 to 17 years old. Peculiarities of age-dependent dynamics of functional level of the central nervous system, stability of the reactions, levels of functional possibilities were described. The age-dependent periods of strengthening and weakening of correlation between the indexes of motive reaction and the criteria of the functional state of central nervous system were determined.

  12. Stress reactions after a patient suicide and their relations to the profile of mental health professionals

    OpenAIRE

    Castelli Dransart, Dolores Angela; Heeb, Jean-Luc; Gulfi, Alida; Gutjahr, Elisabeth M.

    2015-01-01

    Background Patient suicide is a professional hazard for mental health professionals and an event likely to trigger stress reactions among them. This study aimed to identify typical profiles of professionals after a patient suicide to address the severity of stress reactions and its discriminant variables. Methods Mental health professionals (N = 666) working in institutional settings or private practice in the French-speaking part of Switzerland filled out a self-administered questionnaire in...

  13. Ontology aided modeling of organic reaction mechanisms with flexible and fragment based XML markup procedures.

    Science.gov (United States)

    Sankar, Punnaivanam; Aghila, Gnanasekaran

    2007-01-01

    The mechanism models for primary organic reactions encoding the structural fragments undergoing substitution, addition, elimination, and rearrangements are developed. In the proposed models, each and every structural component of mechanistic pathways is represented with flexible and fragment based markup technique in XML syntax. A significant feature of the system is the encoding of the electron movements along with the other components like charges, partial charges, half bonded species, lone pair electrons, free radicals, reaction arrows, etc. needed for a complete representation of reaction mechanism. The rendering of reaction schemes described with the proposed methodology is achieved with a concise XML extension language interoperating with the structure markup. The reaction scheme is visualized as 2D graphics in a browser by converting them into SVG documents enabling the desired layouts normally perceived by the chemists conventionally. An automatic representation of the complex patterns of the reaction mechanism is achieved by reusing the knowledge in chemical ontologies and developing artificial intelligence components in terms of axioms.

  14. Application of a non-equilibrium reaction model for describing horizontal well performance in foamy oil

    Energy Technology Data Exchange (ETDEWEB)

    Luigi, A.; Saputelli, B.; Carlas, M.; Canache, P.; Lopez, E. [DPVS Exploracion y Produccion (Venezuela)

    1998-12-31

    This study was designed to determine the activation energy ranges and frequency factor ranges in chemical reactions in heavy oils of the Orinoco Belt in Venezuela, in order to account for the kinetics of physical changes that occur in the morphology of gas-oil dispersion. A non-equilibrium reaction model was used to model foamy oil behaviour observed at SDZ-182 horizontal well in the Zuata field. Results showed that activation energy for the first reaction ranged from 0 to 0.01 BTU/lb-mol and frequency factor from 0.001 to 1000 l/day. For the second reaction the activation energy was 50x10{sub 3} BTU/lb-mol and the frequency factor 2.75x10{sub 1}2 l/day. The second reaction was highly sensitive to the modifications in activation energy and frequency factor. However, both the activation energy and frequency factor were independent of variations for the first reaction. In the case of the activation energy, the results showed that the high sensitivity of this parameter reflected the impact that temperature has on the representation of foamy oil behaviour. 8 refs., 2 tabs., 6 figs.

  15. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    CERN Document Server

    Cyburt, R H; Heger, A; Johnson, E; Keek, L; Meisel, Z; Schatz, H; Smith, K

    2016-01-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p,$\\gamma$), ($\\alpha$,$\\gamma$), and ($\\alpha$,p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the {\\Kepler} stellar evolution code. All relevant reaction rates on neutron deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 highest impact reaction rate changes were then repeated in the 1D multi-zone model. We find a number of uncertain reac...

  16. Characteristics of the probability function for three random-walk models of reaction--diffusion processes

    Energy Technology Data Exchange (ETDEWEB)

    Musho, M.K.; Kozak, J.J.

    1984-10-01

    A method is presented for calculating exactly the relative width (sigma/sup 2/)/sup 1/2//, the skewness ..gamma../sub 1/, and the kurtosis ..gamma../sub 2/ characterizing the probability distribution function for three random-walk models of diffusion-controlled processes. For processes in which a diffusing coreactant A reacts irreversibly with a target molecule B situated at a reaction center, three models are considered. The first is the traditional one of an unbiased, nearest-neighbor random walk on a d-dimensional periodic/confining lattice with traps; the second involves the consideration of unbiased, non-nearest-neigh bor (i.e., variable-step length) walks on the same d-dimensional lattice; and, the third deals with the case of a biased, nearest-neighbor walk on a d-dimensional lattice (wherein a walker experiences a potential centered at the deep trap site of the lattice). Our method, which has been described in detail elsewhere (P.A. Politowicz and J. J. Kozak, Phys. Rev. B 28, 5549 (1983)) is based on the use of group theoretic arguments within the framework of the theory of finite Markov processes.

  17. Bifurcation analysis of a delay reaction-diffusion malware propagation model with feedback control

    Science.gov (United States)

    Zhu, Linhe; Zhao, Hongyong; Wang, Xiaoming

    2015-05-01

    With the rapid development of network information technology, information networks security has become a very critical issue in our work and daily life. This paper attempts to develop a delay reaction-diffusion model with a state feedback controller to describe the process of malware propagation in mobile wireless sensor networks (MWSNs). By analyzing the stability and Hopf bifurcation, we show that the state feedback method can successfully be used to control unstable steady states or periodic oscillations. Moreover, formulas for determining the properties of the bifurcating periodic oscillations are derived by applying the normal form method and center manifold theorem. Finally, we conduct extensive simulations on large-scale MWSNs to evaluate the proposed model. Numerical evidences show that the linear term of the controller is enough to delay the onset of the Hopf bifurcation and the properties of the bifurcation can be regulated to achieve some desirable behaviors by choosing the appropriate higher terms of the controller. Furthermore, we obtain that the spatial-temporal dynamic characteristics of malware propagation are closely related to the rate constant for nodes leaving the infective class for recovered class and the mobile behavior of nodes.

  18. Exhaustive study of the noise-induced phase transition in a stochastic model of self-catalyzed reactions

    Science.gov (United States)

    Pham, T. M.; Virchenko, Yu. P.

    2016-08-01

    We completely investigate the stationary distribution density in the space of relative concentrations for the three-parameter stochastic Horsthemke-Lefever model of a binary self-catalyzed cyclic chemical reaction with perturbations produced by thermal fluctuations of reagents taken into account. This model is a stationary diffusion random process generated by a stochastic equation with the Stratonovich differential, whose marginal distribution density admits a bifurcation restructuring from the unimodal to the bimodal phase with increasing noise intensity, which is interpreted physically as a dynamical phase transition induced by fluctuations in the system.

  19. Interaction of genotype-environment Nellore cattle using models of reaction

    Directory of Open Access Journals (Sweden)

    Wéverton José Lima Fonseca

    2015-06-01

    Full Text Available The objective of this review was to discuss the importance of bovine genotype-environment iteration Nellore using models of reaction norms. The beef cattle has been outstanding with one of the main activities of Brazilian agribusiness, including in the international arena. One way to assess the genotype-environment interaction for various traits in beef cattle as milk is the use of models of reaction norms. Thus, the conduct of research involving the effect of genotype-environment interaction allows for an assessment of the animals in the production environment and management of genetically superior animals.

  20. Nanolithographic Fabrication and Heterogeneous Reaction Studies ofTwo-Dimensional Platinum Model Catalyst Systems

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, Anthony Marshall [Univ. of California, Berkeley, CA (United States)

    2006-05-20

    In order to better understand the fundamental components that govern catalytic activity, two-dimensional model platinum nanocatalyst arrays have been designed and fabricated. These catalysts arrays are meant to model the interplay of the metal and support important to industrial heterogeneous catalytic reactions. Photolithography and sub-lithographic techniques such as electron beam lithography, size reduction lithography and nanoimprint lithography have been employed to create these platinum nanoarrays. Both in-situ and ex-situ surface science techniques and catalytic reaction measurements were used to correlate the structural parameters of the system to catalytic activity.

  1. Modeling of alkali-silica reaction in concrete:a review

    Institute of Scientific and Technical Information of China (English)

    D.R.J.OWEN

    2012-01-01

    This paper presents a comprehensive review of modeling of alkali-silica reaction (ASR) in concrete.Such modeling is essential for investigating the chemical expansion mechanism and the subsequent influence on the mechanical aspects of the material.The concept of ASR and the mechanism of expansion are first outlined,and the stateof-the-art of modeling for ASR,the focus of the paper,is then presented in detail.The modeling includes theoretical approaches,meso-and macroscopic models for ASR analysis.The theoretical approaches dealt with the chemical reaction mechanism and were used for predicting pessimum size of aggregate.Mesoscopic models have attempted to explain the mechanism of mechanical deterioration of ASR-affected concrete at material scale.The macroscopic models,chemomechanical coupling models,have been generally developed by combining the chemical reaction kinetics with linear or nonlinear mechanical constitutive,and were applied to reproduce and predict the long-term behavior of structures suffering from ASR.Finally,a conclusion and discussion of the modeling are given.

  2. Quantitative models of hydrothermal fluid-mineral reaction: The Ischia case

    Science.gov (United States)

    Di Napoli, Rossella; Federico, Cinzia; Aiuppa, Alessandro; D'Antonio, Massimo; Valenza, Mariano

    2013-03-01

    The intricate pathways of fluid-mineral reactions occurring underneath active hydrothermal systems are explored in this study by applying reaction path modelling to the Ischia case study. Ischia Island, in Southern Italy, hosts a well-developed and structurally complex hydrothermal system which, because of its heterogeneity in chemical and physical properties, is an ideal test sites for evaluating potentialities/limitations of quantitative geochemical models of hydrothermal reactions. We used the EQ3/6 software package, version 7.2b, to model reaction of infiltrating waters (mixtures of meteoric water and seawater in variable proportions) with Ischia's reservoir rocks (the Mount Epomeo Green Tuff units; MEGT). The mineral assemblage and composition of such MEGT units were initially characterised by ad hoc designed optical microscopy and electron microprobe analysis, showing that phenocrysts (dominantly alkali-feldspars and plagioclase) are set in a pervasively altered (with abundant clay minerals and zeolites) groundmass. Reaction of infiltrating waters with MEGT minerals was simulated over a range of realistic (for Ischia) temperatures (95-260 °C) and CO2 fugacities (10-0.2 to 100.5) bar. During the model runs, a set of secondary minerals (selected based on independent information from alteration minerals' studies) was allowed to precipitate from model solutions, when saturation was achieved. The compositional evolution of model solutions obtained in the 95-260 °C runs were finally compared with compositions of Ischia's thermal groundwaters, demonstrating an overall agreement. Our simulations, in particular, well reproduce the Mg-depleting maturation path of hydrothermal solutions, and have end-of-run model solutions whose Na-K-Mg compositions well reflect attainment of full-equilibrium conditions at run temperature. High-temperature (180-260 °C) model runs are those best matching the Na-K-Mg compositions of Ischia's most chemically mature water samples

  3. VR-SCOSMO: A smooth conductor-like screening model with charge-dependent radii for modeling chemical reactions.

    Science.gov (United States)

    Kuechler, Erich R; Giese, Timothy J; York, Darrin M

    2016-04-28

    To better represent the solvation effects observed along reaction pathways, and of ionic species in general, a charge-dependent variable-radii smooth conductor-like screening model (VR-SCOSMO) is developed. This model is implemented and parameterized with a third order density-functional tight binding quantum model, DFTB3/3OB-OPhyd, a quantum method which was developed for organic and biological compounds, utilizing a specific parameterization for phosphate hydrolysis reactions. Unlike most other applications with the DFTB3/3OB model, an auxiliary set of atomic multipoles is constructed from the underlying DFTB3 density matrix which is used to interact the solute with the solvent response surface. The resulting method is variational, produces smooth energies, and has analytic gradients. As a baseline, a conventional SCOSMO model with fixed radii is also parameterized. The SCOSMO and VR-SCOSMO models shown have comparable accuracy in reproducing neutral-molecule absolute solvation free energies; however, the VR-SCOSMO model is shown to reduce the mean unsigned errors (MUEs) of ionic compounds by half (about 2-3 kcal/mol). The VR-SCOSMO model presents similar accuracy as a charge-dependent Poisson-Boltzmann model introduced by Hou et al. [J. Chem. Theory Comput. 6, 2303 (2010)]. VR-SCOSMO is then used to examine the hydrolysis of trimethylphosphate and seven other phosphoryl transesterification reactions with different leaving groups. Two-dimensional energy landscapes are constructed for these reactions and calculated barriers are compared to those obtained from ab initio polarizable continuum calculations and experiment. Results of the VR-SCOSMO model are in good agreement in both cases, capturing the rate-limiting reaction barrier and the nature of the transition state.

  4. VR-SCOSMO: A smooth conductor-like screening model with charge-dependent radii for modeling chemical reactions

    Science.gov (United States)

    Kuechler, Erich R.; Giese, Timothy J.; York, Darrin M.

    2016-04-01

    To better represent the solvation effects observed along reaction pathways, and of ionic species in general, a charge-dependent variable-radii smooth conductor-like screening model (VR-SCOSMO) is developed. This model is implemented and parameterized with a third order density-functional tight binding quantum model, DFTB3/3OB-OPhyd, a quantum method which was developed for organic and biological compounds, utilizing a specific parameterization for phosphate hydrolysis reactions. Unlike most other applications with the DFTB3/3OB model, an auxiliary set of atomic multipoles is constructed from the underlying DFTB3 density matrix which is used to interact the solute with the solvent response surface. The resulting method is variational, produces smooth energies, and has analytic gradients. As a baseline, a conventional SCOSMO model with fixed radii is also parameterized. The SCOSMO and VR-SCOSMO models shown have comparable accuracy in reproducing neutral-molecule absolute solvation free energies; however, the VR-SCOSMO model is shown to reduce the mean unsigned errors (MUEs) of ionic compounds by half (about 2-3 kcal/mol). The VR-SCOSMO model presents similar accuracy as a charge-dependent Poisson-Boltzmann model introduced by Hou et al. [J. Chem. Theory Comput. 6, 2303 (2010)]. VR-SCOSMO is then used to examine the hydrolysis of trimethylphosphate and seven other phosphoryl transesterification reactions with different leaving groups. Two-dimensional energy landscapes are constructed for these reactions and calculated barriers are compared to those obtained from ab initio polarizable continuum calculations and experiment. Results of the VR-SCOSMO model are in good agreement in both cases, capturing the rate-limiting reaction barrier and the nature of the transition state.

  5. A numerical evaluation of prediction accuracy of CO2 absorber model for various reaction rate coefficients

    Directory of Open Access Journals (Sweden)

    Shim S.M.

    2012-01-01

    Full Text Available The performance of the CO2 absorber column using mono-ethanolamine (MEA solution as chemical solvent are predicted by a One-Dimensional (1-D rate based model in the present study. 1-D Mass and heat balance equations of vapor and liquid phase are coupled with interfacial mass transfer model and vapor-liquid equilibrium model. The two-film theory is used to estimate the mass transfer between the vapor and liquid film. Chemical reactions in MEA-CO2-H2O system are considered to predict the equilibrium pressure of CO2 in the MEA solution. The mathematical and reaction kinetics models used in this work are calculated by using in-house code. The numerical results are validated in the comparison of simulation results with experimental and simulation data given in the literature. The performance of CO2 absorber column is evaluated by the 1-D rate based model using various reaction rate coefficients suggested by various researchers. When the rate of liquid to gas mass flow rate is about 8.3, 6.6, 4.5 and 3.1, the error of CO2 loading and the CO2 removal efficiency using the reaction rate coefficients of Aboudheir et al. is within about 4.9 % and 5.2 %, respectively. Therefore, the reaction rate coefficient suggested by Aboudheir et al. among the various reaction rate coefficients used in this study is appropriate to predict the performance of CO2 absorber column using MEA solution. [Acknowledgement. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF, funded by the Ministry of Education, Science and Technology (2011-0017220].

  6. Supercritical water oxidation of quinazoline: Reaction kinetics and modeling.

    Science.gov (United States)

    Gong, Yanmeng; Guo, Yang; Wang, Shuzhong; Song, Wenhan; Xu, Donghai

    2017-03-01

    This paper presents a first quantitative kinetic model for supercritical water oxidation (SCWO) of quinazoline that describes the formation and interconversion of intermediates and final products at 673-873 K. The set of 11 reaction pathways for phenol, pyrimidine, naphthalene, NH3, etc, involved in the simplified reaction network proved sufficient for fitting the experimental results satisfactorily. We validated the model prediction ability on CO2 yields at initial quinazoline loading not used in the parameter estimation. Reaction rate analysis and sensitivity analysis indicate that nearly all reactions reach their thermodynamic equilibrium within 300 s. The pyrimidine yielding from quinazoline is the dominant ring-opening pathway and provides a significant contribution to CO2 formation. Low sensitivity of NH3 decomposition rate to concentration confirms its refractory nature in SCWO. Nitrogen content in liquid products decreases whereas that in gaseous phase increases as reaction time prolonged. The nitrogen predicted by the model in gaseous phase combined with the experimental nitrogen in liquid products gives an accurate nitrogen balance of conversion process.

  7. Reactions of aqueous chlorine and chlorine dioxide with model food compounds.

    Science.gov (United States)

    Fukayama, M Y; Tan, H; Wheeler, W B; Wei, C I

    1986-01-01

    Chlorine and chlorine dioxide (ClO2), common disinfecting and bleaching chemicals used in the food industry, are potent oxidizing and chlorinating agents. Unfortunately, little is known about the nature of the reactions of chlorine with organic food constituents. This presentation reviews published information concerning the reactions of chlorine gas (Cl2[g]), aqueous chlorine, and ClO2 with model food compounds, the fate of chlorine during the chlorination of specific food products, and the potential toxicity of the reaction products. Fatty acids and their methyl esters react with chlorine with the degree of incorporation corresponding to their degree of unsaturation. Aqueous chlorine oxidizes and chlorinates lipids and amino acids much more readily than ClO2. Several amino acids are highly susceptible to oxidation and chlorination by chlorine compounds. Reactions of chlorine and ClO2 with several food products, including flour and shrimp, have also been characterized. In one model system, 99% of Cl2(g) either reacted with components of flour or was consumed by oxidation/chlorination reactions. The lipids extracted from the chlorinated flour contained significant amounts of chlorine. Exposure of shrimp to hypochlorous acid (HOCl) solution resulted in significant incorporation of chlorine into the edible portion. Although significant quantities of chlorine can be incorporated into specific model compounds and food products, the health risks associated with exposure to chlorinated organic products are unknown. Preliminary studies using the Ames Salmonella/microsome mutagenicity assay indicate that the reaction products from mixtures of aqueous chlorine and various lipids or tryptophan are nonmutagenic. Nevertheless, additional studies are warranted, so that the toxicological significance of these reaction products can be understood more fully. PMID:3545804

  8. Practical enhancement factor model based on GM for multiple parallel reactions: Piperazine (PZ) CO2 capture

    DEFF Research Database (Denmark)

    Gaspar, Jozsef; Fosbøl, Philip Loldrup

    2017-01-01

    Reactive absorption is a key process for gas separation and purification and it is the main technology for CO2 capture. Thus, reliable and simple mathematical models for mass transfer rate calculation are essential. Models which apply to parallel interacting and non-interacting reactions, for all......, desorption and pinch conditions.In this work, we apply the GM model to multiple parallel reactions. We deduce the model for piperazine (PZ) CO2 capture and we validate it against wetted-wall column measurements using 2, 5 and 8 molal PZ for temperatures between 40 °C and 100 °C and CO2 loadings between 0.......23 and 0.41 mol CO2/2 mol PZ. We show that overall second order kinetics describes well the reaction between CO2 and PZ accounting for the carbamate and bicarbamate reactions. Here we prove the GM model for piperazine and MEA but we expect that this practical approach is applicable for various amines...

  9. Bayesian analysis of the linear reaction norm model with unknown covariates.

    Science.gov (United States)

    Su, G; Madsen, P; Lund, M S; Sorensen, D; Korsgaard, I R; Jensen, J

    2006-07-01

    The reaction norm model is becoming a popular approach for the analysis of genotype x environment interactions. In a classical reaction norm model, the expression of a genotype in different environments is described as a linear function (a reaction norm) of an environmental gradient or value. An environmental value is typically defined as the mean performance of all genotypes in the environment, which is usually unknown. One approximation is to estimate the mean phenotypic performance in each environment and then treat these estimates as known covariates in the model. However, a more satisfactory alternative is to infer environmental values simultaneously with the other parameters of the model. This study describes a method and its Bayesian Markov Chain Monte Carlo implementation that makes this possible. Frequentist properties of the proposed method are tested in a simulation study. Estimates of parameters of interest agree well with the true values. Further, inferences about genetic parameters from the proposed method are similar to those derived from a reaction norm model using true environmental values. On the other hand, using phenotypic means as proxies for environmental values results in poor inferences.

  10. Hansen's disease (Leprosy): current and future pharmacotherapy and treatment of disease-related immunologic reactions.

    Science.gov (United States)

    Legendre, Davey P; Muzny, Christina A; Swiatlo, Edwin

    2012-01-01

    Hansen's disease, also known as leprosy, remains an important public health problem throughout the world, including North America. The causative microbe in Hansen's disease is Mycobacterium leprae, an acid-fast organism that is difficult to grow in vitro. The nine-banded armadillo is the major animal reservoir in the United States. Manifestations of disease vary based on host immune response and can range from tuberculoid to lepromatous leprosy (paucibacillary to multibacillary disease). Hansen's disease typically affects the skin, nerves, and eyes, and patients may present with skin lesions, weakness, numbness, eye pain, or loss of vision. Definitive diagnosis is based on a combination of physical examination findings and skin biopsy and/or smear. Modern antibacterial therapy typically consists of combinations of dapsone and rifampin with or without clofazimine. Clofazimine is available only as an investigational drug through the National Hansen's Disease Program. Other options include moxifloxacin, ofloxacin, minocycline, and clarithromycin. Hansen's disease is associated with type 1 (reversal) and type 2 (erythema nodosum leprosum) immunologic reactions, during which the disease process appears to worsen dramatically. These reactions may occur at any time before, during, or after treatment. Antibacterial therapy should usually be continued during these reactions. Treatment options for these reactions differ based on clinical manifestations and include corticosteroids, thalidomide, pentoxiphylline, tumor necrosis factor inhibitors, and T cell inhibitors. Prompt diagnosis, antimicrobial therapy, and treatment of reactions dramatically reduce complications of the disease. © 2012, Pharmacotherapy Publications, Inc.

  11. Mass Transfer with Chemical Reaction.

    Science.gov (United States)

    DeCoursey, W. J.

    1987-01-01

    Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

  12. Mass Transfer with Chemical Reaction.

    Science.gov (United States)

    DeCoursey, W. J.

    1987-01-01

    Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

  13. Reaction kinetic model of the surface-mediated formation of PCDD/F from pyrolysis of 2-chlorophenol on a CuP/Silica suface

    Energy Technology Data Exchange (ETDEWEB)

    Lomnicki, S.; Khachatryan, L.; Dellinger, B. [Louisiana State Univ., Baton Rouge (United States). Dept. of Chemistry

    2004-09-15

    One of the major challenges in developing predictive models of the surface mediated pollutant formation and fuel combustion is the construction of reliable reaction kinetic mechanisms and models. While the homogeneous, gas-phase chemistry of various light fuels such as hydrogen and methane is relatively well-known large uncertainties exist in the reaction paths of surface mediated reaction mechanisms for even these very simple species. To date, no detailed kinetic consideration of the surface mechanisms of formation of complex organics such as PCDD/F have been developed. In addition to the complexity of the mechanism, a major difficulty is the lack of reaction kinetic parameters (pre-exponential factor and activation energy) of surface reactions, Consequently, numerical studies of the surface-mediated formation of PCDD/F have often been incorporated only a few reactions. We report the development of a numerical multiple-step surface model based on experimental data of surface mediated (5% CuO/SiO2) conversion of 2-monochlorphenol (2-MCP) to PCDD/F under pyrolytic or oxidative conditions. A reaction kinetic model of the catalytic conversion of 2-MCP on the copper oxide catalyst under pyrolytic conditions was developed based on a detailed multistep surface reaction mechanism developed in our laboratory. The performance of the chemical model is assessed by comparing the numerical predictions with experimental measurements. SURFACE CHEMKIN (version 3.7.1) software was used for modeling. Our results confirm the validity of previously published mechanism of the reaction and provides new insight concerning the formation of PCDD/F formation in combustion processes. This model successfully explains the high yields of PCDD/F at low temperatures that cannot be explained using a purely gas-phase mode.

  14. Comment on: ``Chaos in the Showalter-Noyes-Bar-Eli model of the Belousov-Zhabotinskii reaction''

    Science.gov (United States)

    Györgyi, László; Field, Richard J.

    1990-08-01

    The recent numerical work of Lindberg et al. convincingly demonstrates that chemical chaos in a continuous flow, stirred tank reactor (CSTR) can be reproduced by a spatially homogeneous, accurate model of the kinetics of the Belousov-Zhabotinskii(BZ) reaction. However, some problems remain. The chaos in this model and two others, one using an accurate model of the chemical kinetics in conjunction with spatial inhomogeneity resulting from the finite CSTR mixing time and the other using a flawed model of the BZ chemical kinetics, results from coupling of two cycles coexisting within the complex dynamic model. The second cycle in the case of the homogeneous models involves a product of the main chemical limit cycle which is present at a high average concentration. In the Lindberg et al. model this product is assumed to be HOBr. It is clear, however, that a large [HOBr] does not accumulate in the real system because of its rapid reaction with Br-. We suggest that while the Lindberg et al. results are clearly important, this process still needs to be accounted for. Furthermore, the rate parameter values used by Lindberg et al. are not those currently thought to be correct, and the chaos disappears if the accurate rate constant values are used. We discuss why this is so. It is further argued that the Lindberg et al. results do not eliminate the possibility that at least part of the experimentally observed CSTR chaos results from effects related to incomplete mixing.

  15. Kinetic study of CO2 reaction with CaO by a modified random pore model

    Directory of Open Access Journals (Sweden)

    Nouri S.M.M.

    2016-03-01

    Full Text Available In this work, a modified random pore model was developed to study the kinetics of the carbonation reaction of CaO. Pore size distributions of the CaO pellets were measured by nitrogen adsorption and mercury porosimetry methods. The experiments were carried out in a thermogravimeter at different isothermal temperatures and CO2 partial pressures. A fractional concentration dependency function showed the best accuracy for predicting the intrinsic rate of reaction. The activation energy was determined as 11 kcal/mole between 550–700°C. The effect of product layer formation was also taken into account by using the variable product layer diffusivity. Also, the model was successfully predicted the natural lime carbonation reaction data extracted from the literature.

  16. A Series Solution of the Cauchy Problem for Turing Reaction-diffusion Model

    Directory of Open Access Journals (Sweden)

    L. Päivärinta

    2011-12-01

    Full Text Available In this paper, the series pattern solution of the Cauchy problem for Turing reaction-diffusion model is obtained by using the homotopy analysis method (HAM. Turing reaction-diffusion model is nonlinear reaction-diffusion system which usually has power-law nonlinearities or may be rewritten in the form of power-law nonlinearities. Using the HAM, it is possible to find the exact solution or an approximate solution of the problem. This technique provides a series of functions which converges rapidly to the exact solution of the problem. The efficiency of the approach will be shown by applying the procedure on two problems. Furthermore, the so-called homotopy-Pade technique (HPT is applied to enlarge the convergence region and rate of solution series given by the HAM.

  17. $K^{+}$ momentum spectrum from $(K^{-},K^{+})$ reactions in intranuclear cascade model

    CERN Document Server

    Nara, Y; Harada, T; Engel, A

    1996-01-01

    In a framework of intranuclear cascade (INC) type calculation, we study a momentum spectrum in reactions \\KK at a beam momentum of 1.65 GeV/c. INC model calculations are compared with the relativistic impulse approximation (RIA) calculations to perform the detailed study of the reaction mechanism. We find that the INC model can reproduce the experimental data on various targets. Especially, in the low-momentum region, the forward-angle cross sections of the $(K^-,K^+)$ reaction on from light to heavy targets are consistently explained with the two-step strangeness exchange and production processes with various intermediate mesons, and $\\phi$, $a_0$ and $f_0$ productions and their decay into $K^+K^-$. In the two-step processes, inclusion of meson and hyperon resonances is found to be essential.

  18. Application of diffusion-reaction equations to model carious lesion progress

    Science.gov (United States)

    Lewandowska, Katarzyna D.; Kosztołowicz, Tadeusz

    2012-04-01

    Nonlinear equations that describe the diffusion-reaction process with one static and one mobile substance are used to model a carious lesion process. The system under consideration consists of two initially separated substances A (an acid causing caries) and C (a static enamel mineral) which react chemically according to the formula A+C→0̸(inert). The so-called surface layer, which is formed in this process and in which chemical reactions can be neglected, is also included in this model. Changes in the substance concentrations are calculated approximately using the perturbation method. We show that the experimental data on the enamel mineral concentrations are well described by the analytical solutions of the diffusion-reaction equations.

  19. Immunotherapy improves health-related quality of life of adult patients with dermal reactions following yellow jacket stings

    NARCIS (Netherlands)

    Oude Elberink, J. N. G.; van der Heide, S.; Guyatt, G. H.; Dubois, A. E. J.

    In many European centers insect venom allergic patients with a reaction confined to the skin are only offered an epinephrine auto-injector and not venom immunotherapy (VIT). Previously we showed that VIT improves health-related quality of life (HRQL) of yellow jacket allergic patients with more than

  20. Health-related quality of life in children and emotional reactions of parents following completion of cancer treatment.

    NARCIS (Netherlands)

    Stam, H.; Grootenhuis, M.A.; Brons, P.P.T.; Caron, H.N.; Last, B.F.

    2006-01-01

    BACKGROUND: Completing therapy is one of the major transitions in care in the practice of pediatric oncology and, therefore, deserves special consideration. The purpose of the study was to investigate health-related quality of life (HRQOL) of pediatric patients, and emotional reactions of their

  1. Child Physical Abuse and the Related PTSD in Taiwan: The Role of Chinese Cultural Background and Victims' Subjective Reactions

    Science.gov (United States)

    Chou, Chia-Ying; Su, Yi-Jen; Wu, Ho-Mao; Chen, Sue-Huei

    2011-01-01

    Objective: This study aimed to investigate child physical abuse (CPA) while taking into account the more rigorous definitions of CPA in the Chinese societies. The prevalence of CPA and CPA-related PTSD were estimated, together with the examination of peri-traumatic subjective reactions and their impacts on PTSD. Methods: In a Taiwanese sample of…

  2. Diagnosis of ventricular drainage-related bacterial meningitis by broad-range real-time polymerase chain reaction

    DEFF Research Database (Denmark)

    Deutch, Susanna; Dahlberg, Daniel; Hedegaard, Jesper;

    2007-01-01

    OBJECTIVE: To compare a broad-range real-time polymerase chain reaction (PCR) diagnostic strategy with culture to evaluate additional effects on the etiological diagnosis and the quantification of the bacterial load during the course of ventricular drainage-related bacterial meningitis (VR...

  3. Immunotherapy improves health-related quality of life of adult patients with dermal reactions following yellow jacket stings

    NARCIS (Netherlands)

    Oude Elberink, J. N. G.; van der Heide, S.; Guyatt, G. H.; Dubois, A. E. J.

    2009-01-01

    In many European centers insect venom allergic patients with a reaction confined to the skin are only offered an epinephrine auto-injector and not venom immunotherapy (VIT). Previously we showed that VIT improves health-related quality of life (HRQL) of yellow jacket allergic patients with more than

  4. Health-related quality of life in children and emotional reactions of parents following completion of cancer treatment

    NARCIS (Netherlands)

    H. Stam; M.A. Grootenhuis; P.P.T. Brons; H.N. Caron; B.F. Last

    2006-01-01

    Background. Completing therapy is one of the major transitions in care in the practice of pediatric oncology and, therefore, deserves special consideration. The purpose of the study was to investigate health-related quality of life. (HRQOL) of pediatric patients, and emotional reactions of their par

  5. Health-related quality of life in children and emotional reactions of parents following completion of cancer treatment.

    NARCIS (Netherlands)

    Stam, H.; Grootenhuis, M.A.; Brons, P.P.T.; Caron, H.N.; Last, B.F.

    2006-01-01

    BACKGROUND: Completing therapy is one of the major transitions in care in the practice of pediatric oncology and, therefore, deserves special consideration. The purpose of the study was to investigate health-related quality of life (HRQOL) of pediatric patients, and emotional reactions of their pare

  6. Mercury content in amalgam tattoos of human oral mucosa and its relation to local tissue reactions

    Energy Technology Data Exchange (ETDEWEB)

    Forsell, M.; Larsson, B.; Ljungqvist, A.; Carlmark, B.; Johansson, O

    1998-02-01

    Mucosal biopsies from 48 patients with and 9 without amalgam tattoos were analysed with respect to their mercury content, distribution of mercury in the tissue, and histological tissue reactions. The distribution of mercury was assessed by auto-metallography (AMG), a silver amplification technique. The mercury content was determined by energy dispersive X-ray fluorescence (EDXRF), a multielemental analysis. Mercury was observed in connective tissue where it was confined to fibroblasts and macrophages, in vessel walls and in structures with the histological character of nerve fibres. A correlation was found between the histopathological tissue reaction, the type of mercury deposition, the intensity of the AMG reaction, and the mercury content. Mercury was also found in patients with amalgam dental fittings but without amalgam tattoos. (au) 24 refs.

  7. Nonsteroidal, antiinflammatory drug-induced gastrointestinal injuries and related adverse reactions: Epidemiology, pathogenesis and management

    Directory of Open Access Journals (Sweden)

    Al Mofleh Ibrahim

    2007-01-01

    Full Text Available A large proportion of the population all over the world consumes acetylsalicylic acid (ASA: aspirin or other nonsteroidal, antiinflammatory drugs (NSAIDs. This is associated with a considerable morbidity and mortality. Elderly patients, patients with prior history of peptic ulcer disease (PUD or its complications, those who require high doses of NSAIDs and those undergoing concomitant therapy with corticosteroids or anticoagulants, are at particularly high risk of developing gastroduodenal injuries and related adverse reactions. Gastroduodenal mucosal injuries induced by NSAIDs vary from subtle microscopic to gross macroscopic changes including ulcers. These injuries are induced by both topical and systemic actions of NSAIDs. Inhibition of gastroduodenal cyclooxygenase (COX enzyme by NSAIDs is considered to be a major pathogenetic factor. Reactive oxygen species (ROS appear also to play a significant role in the pathogenesis of mucosal injury. Withdrawal of NSAIDs is preferably the first therapeutic option; however, it is not feasible in the majority of patients. Therefore, several drugs including antisecretory drugs (ASDs-proton pump inhibitors and Histamine-2 receptor antagonists and misoprostol, a prostaglandin analog are used for the prevention and treatment of NSAID-induced gastroduodenal injuries. Among ASDs, proton pump inhibitors (PPIs are the most commonly used drugs. The antiulcerogenic effect of PPIs is similar to that of misoprostol and superior to standard doses of histamine-2 receptor antagonists (H2-RAs. The adverse effects of m,isoprostol such as diarrhea, abdominal pain, nausea, flatulence, headache, dyspepsia, vomiting, constipation, abortifacient and teratogenicity limit its general use. Aside from their antisecretory action, PPIs also possess an antioxidative effect. PPI maintenance is recommended in chronic NSAID treatment in those with an increased risk of complications and is more effective than Helicobacter pylori

  8. Sequence related amplified polymorphism (SRAP) reaction system optimization and its application

    Institute of Scientific and Technical Information of China (English)

    Li Li

    2006-01-01

    In this study, three methods such as CTAB,SDS and Shanlichun methods were used to extract genomic DNA from the seedling of rape to find the best method. The principle, characters and application of SRAP were introduced. In order to obtain the optimal SRAP reaction system, the factors including concentrations of DNA, dNTP, etc. of reaction system were modified to better the system of rape. The result showed that the optimum concentrations were15ng DNA template, 0.2mM dNTP, 1.0μM primer and 2.0U Taq enzyme in this 25μL SRAP-PCR system.

  9. Reaction dynamics analysis of a reconstituted Escherichia coli protein translation system by computational modeling.

    Science.gov (United States)

    Matsuura, Tomoaki; Tanimura, Naoki; Hosoda, Kazufumi; Yomo, Tetsuya; Shimizu, Yoshihiro

    2017-02-21

    To elucidate the dynamic features of a biologically relevant large-scale reaction network, we constructed a computational model of minimal protein synthesis consisting of 241 components and 968 reactions that synthesize the Met-Gly-Gly (MGG) peptide based on an Escherichia coli-based reconstituted in vitro protein synthesis system. We performed a simulation using parameters collected primarily from the literature and found that the rate of MGG peptide synthesis becomes nearly constant in minutes, thus achieving a steady state similar to experimental observations. In addition, concentration changes to 70% of the components, including intermediates, reached a plateau in a few minutes. However, the concentration change of each component exhibits several temporal plateaus, or a quasi-stationary state (QSS), before reaching the final plateau. To understand these complex dynamics, we focused on whether the components reached a QSS, mapped the arrangement of components in a QSS in the entire reaction network structure, and investigated time-dependent changes. We found that components in a QSS form clusters that grow over time but not in a linear fashion, and that this process involves the collapse and regrowth of clusters before the formation of a final large single cluster. These observations might commonly occur in other large-scale biological reaction networks. This developed analysis might be useful for understanding large-scale biological reactions by visualizing complex dynamics, thereby extracting the characteristics of the reaction network, including phase transitions.

  10. Pertanggungjawaban Sosial Universitas: Implementasi Model Cycle Relations

    Directory of Open Access Journals (Sweden)

    Lina Sinatra Wijaya

    2016-10-01

    Full Text Available The competition among Higher Education is getting tougher. They need to do their best in order to maintain their existence and getting more students coming to their institutions. One way to achieve that goal is through carrying out Corporate Social Responsibility (CSR programs or University Social Responsibility (USR for university. This study tries to investigate the implementation of ‘Cycle Relations’ model in CSR to increase the intake of Higher Education. This study involved seven Higher Educations and nineteen High schools in Central Java. In collecting the data, it used a depth-interview method with all the related parties in this study. The result showed that most of the Higher Education institutions have implemented Corporate Social Responsibility program in various ways. Their target audience included the high schools, society, and parents.  From the model implementation, it showed that the CSR program did have an impact towards the intake in their institution. However, one important thing to consider is that the role of the teachers at schools was quite significant in influencing the students to choose which university to go.  This reflects that although the Higher Education institution have planned and carried out CSR programs according to what the target audiences’ need, it does not guarantee that it will have direct impact towards their intake because the influence of teacher is quite significant. It may have a bigger impact in long term as the target audiences know the quality and contribution of the Higher Education institutions.

  11. Pertanggungjawaban Sosial Universitas: Implementasi Model Cycle Relations

    Directory of Open Access Journals (Sweden)

    Lina Sinatra Wijaya

    2016-08-01

    Full Text Available The competition among Higher Education is getting tougher. They need to do their best in order to maintain their existence and getting more students coming to their institutions. One way to achieve that goal is through carrying out Corporate Social Responsibility (CSR programs or University Social Responsibility (USR for university. This study tries to investigate the implementation of ‘Cycle Relations’ model in CSR to increase the intake of Higher Education. This study involved seven Higher Educations and nineteen High schools in Central Java. In collecting the data, it used a depth-interview method with all the related parties in this study. The result showed that most of the Higher Education institutions have implemented Corporate Social Responsibility program in various ways. Their target audience included the high schools, society, and parents. From the model implementation, it showed that the CSR program did have an impact towards the intake in their institution. However, one important thing to consider is that the role of the teachers at schools was quite significant in influencing the students to choose which university to go. This reflects that although the Higher Education institution have planned and carried out CSR programs according to what the target audiences’ need, it does not guarantee that it will have direct impact towards their intake because the influence of teacher is quite significant. It may have a bigger impact in long term as the target audiences know the quality and contribution of the Higher Education institutions.

  12. An eikonal approach for the initiation of reentrant cardiac propagation in reaction-diffusion models.

    Science.gov (United States)

    Jacquemet, Vincent

    2010-09-01

    Microscale electrical propagation in the heart can be modeled by a reaction-diffusion system, describing cell and tissue electrophysiology. Macroscale features of wavefront propagation can be reproduced by an eikonal model, a reduced formulation involving only wavefront shape. In this paper, these two approaches are combined to incorporate global information about reentrant pathways into a reaction-diffusion model. The eikonal-diffusion formulation is generalized to handle reentrant activation patterns and wavefront collisions. Boundary conditions are used to specify pathways of reentry. Finite-element-based numerical methods are presented to solve this nonlinear equation on a coarse triangular mesh. The macroscale eikonal model serves to construct an initial condition for the microscale reaction-diffusion model. Electrical propagation simulated from this initial condition is then compared to the isochrones predicted by the eikonal model. Results in 2-D and thin 3-D test-case geometries demonstrate the ability of this technique to initiate anatomical and functional reentries along prescribed pathways, thus facilitating the development of dedicated models aimed at better understanding clinical case reports.

  13. Population-reaction model and microbial experimental ecosystems for understanding hierarchical dynamics of ecosystems.

    Science.gov (United States)

    Hosoda, Kazufumi; Tsuda, Soichiro; Kadowaki, Kohmei; Nakamura, Yutaka; Nakano, Tadashi; Ishii, Kojiro

    2016-02-01

    Understanding ecosystem dynamics is crucial as contemporary human societies face ecosystem degradation. One of the challenges that needs to be recognized is the complex hierarchical dynamics. Conventional dynamic models in ecology often represent only the population level and have yet to include the dynamics of the sub-organism level, which makes an ecosystem a complex adaptive system that shows characteristic behaviors such as resilience and regime shifts. The neglect of the sub-organism level in the conventional dynamic models would be because integrating multiple hierarchical levels makes the models unnecessarily complex unless supporting experimental data are present. Now that large amounts of molecular and ecological data are increasingly accessible in microbial experimental ecosystems, it is worthwhile to tackle the questions of their complex hierarchical dynamics. Here, we propose an approach that combines microbial experimental ecosystems and a hierarchical dynamic model named population-reaction model. We present a simple microbial experimental ecosystem as an example and show how the system can be analyzed by a population-reaction model. We also show that population-reaction models can be applied to various ecological concepts, such as predator-prey interactions, climate change, evolution, and stability of diversity. Our approach will reveal a path to the general understanding of various ecosystems and organisms. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  14. Reaction dynamics of {sup 34-38}Mg projectile with carbon target using Glauber model

    Energy Technology Data Exchange (ETDEWEB)

    Shama, Mahesh K., E-mail: maheshphy82@gmail.com [School of Physics and Material Sciences, Thapar University Patiala-147004 (India); Department of Applied Sciences, Chandigarh Engineering College, Landran Mohali-140307 (India); Panda, R. N. [Department of Physics, ITER, Shiksha O Anusandhan University, Bhubaneswar-751030 (India); Sharma, Manoj K. [School of Physics and Material Sciences, Thapar University Patiala-147004 (India); Patra, S. K. [Institute of Physics, Sachivalaya marg Bhubneswar-751005 (India)

    2015-08-28

    We have studied nuclear reaction cross-sections for {sup 34-38}Mg isotopes as projectile with {sup 12}C target at projectile energy 240AMeV using Glauber model with the conjunction of densities from relativistic mean filed formalism. We found good agreement with the available experimental data. The halo status of {sup 37}Mg is also investigated.

  15. Extended Intranuclear Cascade model for pickup reactions induced by 50-MeV-range protons

    Directory of Open Access Journals (Sweden)

    Uozumi Yusuke

    2016-01-01

    Full Text Available The intranuclear cascade model was investigated to explain (p, dx and (p, ax reactions at incident energies of around 50 MeV. Since these reactions are governed mainly by the direct pickup process, the model was expanded to include exclusive pickup processes leading to hole-state-excitations. The energy of the outgoing clusters is determined with single-particle energies of transferred nucleons, the reaction Q-value, and the recoil of the residual nucleus. The rescattering of the produced cluster inside the nucleus is treated within the intranuclear cascade model. The emission angle is given by the sum of momentum vectors of transferred nucleons in addition to the deflection at the nuclear surface, which was introduced to explain angular distributions of elastic scattering. Double differential cross sections of reactions were calculated and compared with experimental data. The proposed model showed a high predictive power over the wide range of emission energies and angles. The treatment ofthe cluster transport inside the nucleus was also verified.

  16. Surface reaction network of CO oxidation on CeO2/Au(110) inverse model catalysts.

    Science.gov (United States)

    Ding, Liangbing; Xiong, Feng; Jin, Yuekang; Wang, Zhengming; Sun, Guanghui; Huang, Weixin

    2016-11-30

    CeO2/Au(110) inverse model catalysts were prepared and their activity toward the adsorption and co-adsorption of O2, CO, CO2 and water was studied by means of X-ray photoelectron spectroscopy, low energy electron diffraction, thermal desorption spectra and temperature-programmed reaction spectra. The Au surface of CeO2/Au(110) inverse model catalysts molecularly adsorbs CO, CO2 and water, and the polycrystalline CeO2 surface of CeO2/Au(110) inverse model catalysts molecularly adsorbs O2, and molecularly and reactively adsorbs CO, CO2 and water. By controllably preparing co-adsorbed surface species on CeO2/Au(110) inverse model catalysts, we successfully identified various surface reaction pathways of CO oxidation to produce CO2 with different barriers both on the CeO2 surface and at the Au-CeO2 interface, including CO oxidation by various oxygen species, and water/hydroxyl group-involved CO oxidation. These results establish a surface reaction network of CO oxidation catalyzed by Au/CeO2 catalysts, greatly advancing the fundamental understandings of catalytic CO oxidation reactions.

  17. Toward a Kinetic Model for Acrylamide Formation in a Glucose-Asparagine Reaction System

    NARCIS (Netherlands)

    Knol, J.J.; Loon, W.A.M.; Linssen, J.P.H.; Ruck, A.L.; Boekel, van M.A.J.S.

    2005-01-01

    A kinetic model for the formation of acrylamide in a glucose-asparagine reaction system is pro-posed. Equimolar solutions (0.2 M) of glucose and asparagine were heated at different tempera-tures (120-200 C) at pH 6.8. Besides the reactants, acrylamide, fructose, and melanoidins were quantified after

  18. Neutrino nucleus reactions at high energies within the GiBUU model

    CERN Document Server

    Lalakulich, O; Leitner, T; Mosel, U

    2011-01-01

    The GiBUU model, which implements all reaction channels relevant at medium neutrino energy, is used to investigate the neutrino and antineutrino scattering on iron. Results for integrated cross sections are compared with NOMAD and MINOS data. It is shown, that final state interaction can noticeably change the spectra of the outgoing hadrons. Predictions for the Miner$\

  19. Molecular Modeling as a Self-Taught Component of a Conventional Undergraduate Chemical Reaction Engineering Course

    Science.gov (United States)

    Rothe, Erhard W.; Zygmunt, William E.

    2016-01-01

    We inserted a self-taught molecular modeling project into an otherwise conventional undergraduate chemical-reaction-engineering course. Our objectives were that students should (a) learn with minimal instructor intervention, (b) gain an appreciation for the relationship between molecular structure and, first, macroscopic state functions in…

  20. A reduced model for the ICF Gamma-Ray reaction history diagnostic

    Science.gov (United States)

    Schmitt, M. J.; Wilson, D. C.; Hoffman, N. M.; Langenbrunner, J. R.; Herrmann, H. W.; Kim, Y. H.; Young, C. S.; Evans, S. C.; Cerjan, C. J.; Stoeffl, Wolfgang; Munro, D. H.; Dauffy, L. S.; Miller, K. M.; Horsfield, C. J.; Rubery, M. S.

    2010-08-01

    An analytic model for the gamma reaction history (GRH) diagnostic to be fielded on the National Ignition Facility is described. The application of the GRH diagnostic for the measurement of capsule rho-R during burn using 4.4 MeV carbon gamma rays is demonstrated by simulation.

  1. A reduced model for the ICF gamma-ray reaction history diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Mark J [Los Alamos National Laboratory; Wilson, Douglas C [Los Alamos National Laboratory; Hoffman, Nelson M [Los Alamos National Laboratory; Langenbrunner, Jamie R [Los Alamos National Laboratory; Hermann, H W [Los Alamos National Laboratory; Kim, Y H [Los Alamos National Laboratory; Young, C S [Los Alamos National Laboratory; Evans, S C [Los Alamos National Laboratory; Cerjan, C J [LLNL; Stoeffl, Wolfgang [LLNL; Munro, D H [LLNL; Dauffy, L S [LLNL; Miller, K M [LIVERMORE; Horsfield, C J [AWE; Rubery, M S [AWE

    2009-01-01

    An analytic model for the gamma reaction history (GRH) diagnostic to be fielded on the National Ignition Facility is described. The application of the GRH diagnostic for the measurement of capsule rho-R during burn using 4.4 MeV carbon gamma rays is demonstrated by simulation.

  2. Modeling Mechanism and Growth Reactions for New Nanofabrication Processes by Atomic Layer Deposition.

    Science.gov (United States)

    Elliott, Simon D; Dey, Gangotri; Maimaiti, Yasheng; Ablat, Hayrensa; Filatova, Ekaterina A; Fomengia, Glen N

    2016-07-01

    Recent progress in the simulation of the chemistry of atomic layer deposition (ALD) is presented for technologically important materials such as alumina, silica, and copper metal. Self-limiting chemisorption of precursors onto substrates is studied using density functional theory so as to determine reaction pathways and aid process development. The main challenges for the future of ALD modeling are outlined.

  3. Modelling and simulation of a transketolase mediated reaction: Sensitivity analysis of kinetic parameters

    DEFF Research Database (Denmark)

    Sayar, N.A.; Chen, B.H.; Lye, G.J.

    2009-01-01

    In this paper we have used a proposed mathematical model, describing the carbon-carbon bond format ion reaction between beta-hydroxypyruvate and glycolaldehyde to synthesise L-erythrulose, catalysed by the enzyme transketolase, for the analysis of the sensitivity of the process to its kinetic par....... (C) 2009 Elsevier B.V. All rights reserved....

  4. Reactions of aqueous chlorine and chlorine dioxide with model food compounds

    Energy Technology Data Exchange (ETDEWEB)

    Fukayama, M.Y.; Tan, H.; Wheeler, W.B.; Wei, C.

    1986-11-01

    This presentation reviews published information concerning the reactions of chlorine gas (CL/sub 2/(g)), aqueous chlorine, and ClO/sub 2/ with model food compounds, the fate of chlorine during the chlorination of specific food products, and the potential toxicity of the reaction products. Fatty acids and their methyl esters react with chlorine with the degree of incorporation corresponding to their degree of unsaturation. Aqueous chlorine oxidizes and chlorinates lipids and amino acids much more readily than ClO/sub 2/. Several amino acids are highly susceptible to oxidation and chlorination by chlorine compounds. Reactions of chlorine and ClO/sub 2/ with several food products, including flour and shrimp, have also been characterized. Although significant quantities of chlorine can be incorporated into specific model compounds and food products, the health risks associated with exposure to chlorinated organic products are unknown. Preliminary studies using the Ames Salmonella/microsome mutagenicity assay indicate that the reaction products from mixtures of aqueous chlorine and various lipids or tryptophan are nonmutagenic. Nevertheless, additional studies are warranted, so that the toxicological significance of these reaction products can be understood more fully.

  5. AN ABSTRACT RELATIONAL MODEL AND NATURAL JOIN FUNCTORS

    OpenAIRE

    Kato, Akihiko

    1983-01-01

    A meta-model for database models called an abstract relational model which is obtained by a categorical abstraction of a relational model is proposed. This meta-model represents various database models, e.g. relational, network, hierarchical models as special cases. It is proved that a natural join is the right adjoint of a decomposition in the relational model. On the other hand, in our abstract relational model a natural join is defined as the right adjoint of a decomposition. A sufficient ...

  6. Modeling of hydrogen evolution reaction on the surface of GaInP2

    Science.gov (United States)

    Choi, Woon Ih; Wood, Brandon; Schwegler, Eric; Ogitsu, Tadashi

    2012-02-01

    GaInP2 is promising candidate material for hydrogen production using sunlight. It reduces solvated proton into hydrogen molecule using light-induced excited electrons in the photoelectrochemical cell. However, it is challenging to model hydrogen evolution reaction (HER) using first-principles molecular dynamics. Instead, we use Anderson-Newns model and generalized solvent coordinate in Marcus-Hush theory to describe adiabatic free energy surface of HER. Model parameters are fitted from the DFT calculations. We model Volmer-Heyrovsky reaction path on the surfaces of CuPt phase of GaInP2. We also discuss effects of surface oxide and catalyst atoms that exist on top of bare surfaces in experimental circumstances.

  7. Heterogeneous chemistry related to Antarctic ozone depletion: Reaction of ClONO2 and N2O5 on ice surfaces

    Science.gov (United States)

    Tolbert, Margaret A.; Rossi, Michel J.; Golden, David M.

    1988-01-01

    Laboratory studies of heterogeneous reactions of possible importance for Antarctic ozone depletion were performed. In particular, the reactions of chlorine nitrate (ClONO2) and dinitrogen pentoxide (N2O5) were investigated on ice and HCl/ice surfaces. These reactions occur on the surfaces of polar stratospheric clouds (PSCs) over Antarctica. One reaction transforms the stable chlorine reservoir species (ClONO2 and HCl) into photochemically active chlorine in the form of HOCl and Cl2. Condensation of HNO3 in the reactions removes odd nitrogen from the stratosphere, a requirement in nearly all models of Antarctic ozone depletion. Other reactions may also be important for Antarctic ozone depletion. Like the reactions of chlorine nitrate, these reactions deplete odd nitrogen through HNO3 condensation. In addition, one reaction converts a stable chlorine reservior species (HCl) into photochemically active chlorine (ClNO2). These reactions were studied with a modified version of a Knudsen cell flow reactor.

  8. Effects of visual-field and matching instruction on event-related potentials and reaction time.

    NARCIS (Netherlands)

    A. Kok; R. van de Vijver; A. Bouma

    1985-01-01

    Vertical letter pairs were presented randomly in the left and right visual hemifields of 20 right-handed male undergraduates in physical-identity match and name-identity match conditions. Reaction times (RTs) showed a right visual-field superiority for name matches and a left visual-field superiorit

  9. Kinetics analysis for development of a rate constant estimation model for ultrasonic degradation reaction of methylene blue.

    Science.gov (United States)

    Kobayashi, Daisuke; Honma, Chiemi; Matsumoto, Hideyuki; Takahashi, Tomoki; Kuroda, Chiaki; Otake, Katsuto; Shono, Atsushi

    2014-07-01

    Ultrasound has been used as an advanced oxidation method for wastewater treatment. Sonochemical degradation of organic compounds in aqueous solution occurs by pyrolysis and/or reaction with hydroxyl radicals. Moreover, kinetics of sonochemical degradation has been proposed. However, the effect of ultrasonic frequency on degradation rate has not been investigated. In our previous study, a simple model for estimating the apparent degradation rate of methylene blue was proposed. In this study, sonochemical degradation of methylene blue was performed at various frequencies. Apparent degradation rate constant was evaluated assuming that sonochemical degradation of methylene blue was a first-order reaction. Specifically, we focused on effects of ultrasonic frequency and power on rate constant, and the applicability of our proposed model was demonstrated. Using this approach, maximum sonochemical degradation rate was observed at 490 kHz, which agrees with a previous investigation into the effect of frequency on the sonochemical efficiency value evaluated by KI oxidation dosimetry. Degradation rate increased with ultrasonic power at every frequency. It was also observed that threshold power must be reached for the degradation reaction to progress. The initial methylene blue concentration and the apparent degradation rate constant have a relation of an inverse proportion. Our proposed model for estimating the apparent degradation rate constant using ultrasonic power and sonochemical efficiency value can apply to this study which extended the frequency and initial concentration range.

  10. Traveling Wave Solutions of Reaction-Diffusion Equations Arising in Atherosclerosis Models

    Directory of Open Access Journals (Sweden)

    Narcisa Apreutesei

    2014-05-01

    Full Text Available In this short review article, two atherosclerosis models are presented, one as a scalar equation and the other one as a system of two equations. They are given in terms of reaction-diffusion equations in an infinite strip with nonlinear boundary conditions. The existence of traveling wave solutions is studied for these models. The monostable and bistable cases are introduced and analyzed.

  11. Resonance model for the three-body states of the A=6 reactions

    Directory of Open Access Journals (Sweden)

    Paris Mark W.

    2016-01-01

    Full Text Available We present an R-matrix-based model for three-body final states that has aspects of the Faddeev approach to three-particle scattering. The model is applied to describing the nucleon spectra for breakup reactions in the A = 6 systems. Calculations using a charge-symmetric parametrization agree fairly well with the experimental data, although they indicate larger contributions from the 5He or 5Li ground state are necessary.

  12. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems

    OpenAIRE

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-01-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux a...

  13. Separation of time-scales and model reduction for stochastic reaction networks

    CERN Document Server

    Kang, Hye-Won

    2010-01-01

    A stochastic model for a chemical reaction network is embedded in a one-parameter family of models with species numbers and rate constants scaled by powers of the parameter. A systematic approach is developed for determining appropriate choices of the exponents that can be applied to large complex networks. When the scaling implies subnetworks have different time-scales, the subnetworks can be approximated separately providing insight into the behavior of the full network through the analysis of these lower dimensional approximations.

  14. Modeling of the interplay between single-file diffusion and conversion reaction in mesoporous systems

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing [Iowa State Univ., Ames, IA (United States)

    2013-01-11

    We analyze the spatiotemporal behavior of species concentrations in a diffusion-mediated conversion reaction which occurs at catalytic sites within linear pores of nanometer diameter. A strict single-file (no passing) constraint occurs in the diffusion within such narrow pores. Both transient and steady-state behavior is precisely characterized by kinetic Monte Carlo simulations of a spatially discrete lattice–gas model for this reaction–diffusion process considering various distributions of catalytic sites. Exact hierarchical master equations can also be developed for this model. Their analysis, after application of mean-field type truncation approximations, produces discrete reaction–diffusion type equations (mf-RDE). For slowly varying concentrations, we further develop coarse-grained continuum hydrodynamic reaction–diffusion equations (h-RDE) incorporating a precise treatment of single-file diffusion (SFD) in this multispecies system. Noting the shortcomings of mf-RDE and h-RDE, we then develop a generalized hydrodynamic (GH) formulation of appropriate gh-RDE which incorporates an unconventional description of chemical diffusion in mixed-component quasi-single-file systems based on a refined picture of tracer diffusion for finite-length pores. The gh-RDE elucidate the non-exponential decay of the steady-state reactant concentration into the pore and the non-mean-field scaling of the reactant penetration depth. Then an extended model of a catalytic conversion reaction within a functionalized nanoporous material is developed to assess the effect of varying the reaction product – pore interior interaction from attractive to repulsive. The analysis is performed utilizing the generalized hydrodynamic formulation of the reaction-diffusion equations which can reliably capture the complex interplay between reaction and restricted transport for both irreversible and reversible reactions.

  15. A thermochemical model for shock-induced reactions (heat detonations) in solids

    Energy Technology Data Exchange (ETDEWEB)

    Boslough, M.B. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (US))

    1990-02-01

    Recent advances in studies of shock-induced chemistry in reactive solids have led to the recognition of a new class of energetic materials which are unique in their response to shock waves. Experimental work has shown that chemical energy can be released on a time scale shorter than shock-transit times in laboratory samples. However, for many compositions, the reaction products remain in the condensed state upon release from high pressure, and no sudden expansion takes place. Nevertheless, if such a reaction is sufficiently rapid, it can be modeled as a type of detonation, termed heat detonation'' in the present paper. It is shown that unlike an explosive detonation, an unsupported heat detonation will decay to zero unless certain conditions are met. An example of such a reaction is Fe{sub 2}O{sub 3} +2Al+shock{r arrow}Al{sub 2} O{sub 3} +2Fe (the standard thermite reaction). A shock-wave equation of state is determined from a mixture theory for reacted and unreacted porous thermite. The calculated shock temperatures are compared to experimentally measured shock temperatures, demonstrating that a shock-induced reaction takes place. Interpretation of the measured temperature history in the context of the thermochemical model implies that the principal rate-controlling kinetic mechanism is dynamic mixing at the shock front. Despite the similarity in thermochemical modeling of heat detonations to explosive detonations, the two processes are qualitatively very different in reaction mechanism as well as in the form the energy takes upon release, with explosives producing mostly work and heat detonations producing mostly heat.

  16. Synthesis of superheavy elements: Uncertainty analysis to improve the predictive power of reaction models

    Science.gov (United States)

    Lü, Hongliang; Boilley, David; Abe, Yasuhisa; Shen, Caiwan

    2016-09-01

    Background: Synthesis of superheavy elements is performed by heavy-ion fusion-evaporation reactions. However, fusion is known to be hindered with respect to what can be observed with lighter ions. Thus some delicate ambiguities remain on the fusion mechanism that eventually lead to severe discrepancies in the calculated formation probabilities coming from different fusion models. Purpose: In the present work, we propose a general framework based upon uncertainty analysis in the hope of constraining fusion models. Method: To quantify uncertainty associated with the formation probability, we propose to propagate uncertainties in data and parameters using the Monte Carlo method in combination with a cascade code called kewpie2, with the aim of determining the associated uncertainty, namely the 95 % confidence interval. We also investigate the impact of different models or options, which cannot be modeled by continuous probability distributions, on the final results. An illustrative example is presented in detail and then a systematic study is carried out for a selected set of cold-fusion reactions. Results: It is rigorously shown that, at the 95 % confidence level, the total uncertainty of the empirical formation probability appears comparable to the discrepancy between calculated values. Conclusions: The results obtained from the present study provide direct evidence for predictive limitations of the existing fusion-evaporation models. It is thus necessary to find other ways to assess such models for the purpose of establishing a more reliable reaction theory, which is expected to guide future experiments on the production of superheavy elements.

  17. Scaffolding Students' Online Critiquing of Expert- and Peer-generated Molecular Models of Chemical Reactions

    Science.gov (United States)

    Chang, Hsin-Yi; Chang, Hsiang-Chi

    2013-08-01

    In this study, we developed online critiquing activities using an open-source computer learning environment. We investigated how well the activities scaffolded students to critique molecular models of chemical reactions made by scientists, peers, and a fictitious peer, and whether the activities enhanced the students' understanding of science models and chemical reactions. The activities were implemented in an eighth-grade class with 28 students in a public junior high school in southern Taiwan. The study employed mixed research methods. Data collected included pre- and post-instructional assessments, post-instructional interviews, and students' electronic written responses and oral discussions during the critiquing activities. The results indicated that these activities guided the students to produce overall quality critiques. Also, the students developed a more sophisticated understanding of chemical reactions and scientific models as a result of the intervention. Design considerations for effective model critiquing activities are discussed based on observational results, including the use of peer-generated artefacts for critiquing to promote motivation and collaboration, coupled with critiques of scientific models to enhance students' epistemological understanding of model purpose and communication.

  18. Reaction mechanisms in the radiolysis of peptides, polypeptides and proteins II reactions at side-chain loci in model systems

    Energy Technology Data Exchange (ETDEWEB)

    Garrison, W.M.

    1983-11-01

    The major emphasis in radiation biology at the molecular level has been on the nucleic acid component of the nucleic acid-protein complex because of its primary genetic importance. But there is increasing evidence that radiation damage to the protein component also has important biological implications. Damage to capsid protein now appears to be a major factor in the radiation inactivation of phage and other viruses. And, there is increasing evidence that radiation-chemical change in the protein component of chromation leads to changes in the stability of the repressor-operator complexes involved in gene expression. Knowledge of the radiation chemistry of protein is also of importance in other fields such as the application of radiation sterilization to foods and drugs. Recent findings that a class of compounds, the ..cap alpha..,..cap alpha..'-diaminodicarboxylic acids, not normally present in food proteins, are formed in protein radiolysis is of particular significance since certain of their peptide derivatives have been showing to exhibit immunological activity. The purpose of this review is to bring together and to correlate our present knowledge of products and mechanisms in the radiolysis of peptides, polypeptides and proteins both aqueous and solid-state. In part 1 we presented a discussion of the radiation-induced reactions of the peptide main-chain in model peptide and polypeptide systems. Here in part 2 the emphasis is on the competing radiation chemistry at side-chain loci of peptide derivatives of aliphatic, aromatic-unsaturated and sulfur-containing amino acids in similar systems. Information obtained with the various experimental techniques of product analysis, competition kinetics, spin-trapping, pulse radiolysis, and ESR spectroscopy are included.

  19. Cholesterol photo-oxidation: A chemical reaction network for kinetic modeling.

    Science.gov (United States)

    Barnaba, Carlo; Rodríguez-Estrada, Maria Teresa; Lercker, Giovanni; García, Hugo Sergio; Medina-Meza, Ilce Gabriela

    2016-12-01

    In this work we studied the effect of polyunsaturated fatty acids (PUFAs) methyl esters on cholesterol photo-induced oxidation. The oxidative routes were modeled with a chemical reaction network (CRN), which represents the first application of CRN to the oxidative degradation of a food-related lipid matrix. Docosahexaenoic acid (DHA, T-I), eicosapentaenoic acid (EPA, T-II) and a mixture of both (T-III) were added to cholesterol using hematoporphyrin as sensitizer, and were exposed to a fluorescent lamp for 48h. High amounts of Type I cholesterol oxidation products (COPs) were recovered (epimers 7α- and 7β-OH, 7-keto and 25-OH), as well as 5β,6β-epoxy. Fitting the experimental data with the CRN allowed characterizing the associated kinetics. DHA and EPA exerted different effects on the oxidative process. DHA showed a protective effect to 7-hydroxy derivatives, whereas EPA enhanced side-chain oxidation and 7β-OH kinetic rates. The mixture of PUFAs increased the kinetic rates several fold, particularly for 25-OH. With respect to the control, the formation of β-epoxy was reduced, suggesting potential inhibition in the presence of PUFAs.

  20. Studies of the Atmospheric Chemsitry of Energy-Related Volatile Organic Compounds and of their Atmospheric Reaction Products

    Energy Technology Data Exchange (ETDEWEB)

    Roger Atkinson; Janet Arey

    2007-04-14

    The focus of this contract was to investigate selected aspects of the atmospheric chemistry of volatile organic compounds (VOCs) emitted into the atmosphere from energy-related sources as well as from biogenic sources. The classes of VOCs studied were polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs, the biogenic VOCs isoprene, 2-methyl-3-buten-2-ol and cis-3-hexen-1-ol, alkenes (including alkenes emitted from vegetation) and their oxygenated atmospheric reaction products, and a series of oxygenated carbonyl and hydroxycarbonyl compounds formed as atmospheric reaction products of aromatic hydrocarbons and other VOCs. Large volume reaction chambers were used to investigate the kinetics and/or products of photolysis and of the gas-phase reactions of these organic compounds with hydroxyl (OH) radicals, nitrate (NO3) radicals, and ozone (O3), using an array of analytical instrumentation to analyze the reactants and products (including gas chromatography, in situ Fourier transform infrared spectroscopy, and direct air sampling atmospheric pressure ionization tandem mass spectrometry). The following studies were carried out. The photolysis rates of 1- and 2-nitronaphthalene and of eleven isomeric methylnitronaphthalenes were measured indoors using blacklamp irradiation and outdoors using natural sunlight. Rate constants were measured for the gas-phase reactions of OH radicals, Cl atoms and NO3 radicals with naphthalene, 1- and 2-methylnaphthalene, 1- and 2-ethylnaphthalene and the ten dimethylnaphthalene isomers. Rate constants were measured for the gas-phase reactions of OH radicals with four unsaturated carbonyls and with a series of hydroxyaldehydes formed as atmospheric reaction products of other VOCs, and for the gas-phase reactions of O3 with a series of cycloalkenes. Products of the gas-phase reactions of OH radicals and O3 with a series of biogenically emitted VOCs were identified and quantified. Ambient atmospheric measurements of the concentrations of a

  1. Modeling of multiphase flow with solidification and chemical reaction in materials processing

    Science.gov (United States)

    Wei, Jiuan

    Understanding of multiphase flow and related heat transfer and chemical reactions are the keys to increase the productivity and efficiency in industrial processes. The objective of this thesis is to utilize the computational approaches to investigate the multiphase flow and its application in the materials processes, especially in the following two areas: directional solidification, and pyrolysis and synthesis. In this thesis, numerical simulations will be performed for crystal growth of several III-V and II-VI compounds. The effects of Prandtl and Grashof numbers on the axial temperature profile, the solidification interface shape, and melt flow are investigated. For the material with high Prandtl and Grashof numbers, temperature field and growth interface will be significantly influenced by melt flow, resulting in the complicated temperature distribution and curved interface shape, so it will encounter tremendous difficulty using a traditional Bridgman growth system. A new design is proposed to reduce the melt convection. The geometric configuration of top cold and bottom hot in the melt will dramatically reduce the melt convection. The new design has been employed to simulate the melt flow and heat transfer in crystal growth with large Prandtl and Grashof numbers and the design parameters have been adjusted. Over 90% of commercial solar cells are made from silicon and directional solidification system is the one of the most important method to produce multi-crystalline silicon ingots due to its tolerance to feedstock impurities and lower manufacturing cost. A numerical model is developed to simulate the silicon ingot directional solidification process. Temperature distribution and solidification interface location are presented. Heat transfer and solidification analysis are performed to determine the energy efficiency of the silicon production furnace. Possible improvements are identified. The silicon growth process is controlled by adjusting heating power and

  2. Mean Field Model of Coagulation and Annihilation Reactions in a Medium of Quenched Traps: Subdiffusion

    OpenAIRE

    I. M. Sokolov; Yuste, S. B.; Ruiz-Lorenzo, J. J.; Lindenberg, Katja

    2008-01-01

    We present a mean field model for coagulation ($A+A\\to A$) and annihilation ($A+A\\to 0$) reactions on lattices of traps with a distribution of depths reflected in a distribution of mean escape times. The escape time from each trap is exponentially distributed about the mean for that trap, and the distribution of mean escape times is a power law. Even in the absence of reactions, the distribution of particles over sites changes with time as particles are caught in ever deeper traps, that is, t...

  3. Mathematical modelling of light-induced electric reaction of Cucurbita pepo L. leaves

    Directory of Open Access Journals (Sweden)

    Jan Stolarek

    2014-01-01

    Full Text Available The bioelectRIc reactions of 14-16 day old plants of pumpkin (Cucurbita pepo L. and internodal cells of Nitellopsis obtusa to the action of visible and ultraviolet light (UV-C were studied. The possibility of analyzing the bioelectric reaction of pumpkin plants induced by visible light by means of mathematical modelling using a linear differential equation of the second order was considered. The solution of this equation (positive and negative functions can, in a sufficient way, reflect the participation of H+ and CI- ions in the generation of the photoelectric response in green plant cells.

  4. Accuracy of Reaction Cross Section for Exotic Nuclei in Glauber Model Based on MCMC Diagnostics

    Science.gov (United States)

    Rueter, Keiti; Novikov, Ivan

    2017-01-01

    Parameters of a nuclear density distribution for an exotic nuclei with halo or skin structures can be determined from the experimentally measured reaction cross-section. In the presented work, to extract parameters such as nuclear size information for a halo and core, we compare experimental data on reaction cross-sections with values obtained using expressions of the Glauber Model. These calculations are performed using a Markov Chain Monte Carlo algorithm. We discuss the accuracy of the Monte Carlo approach and its dependence on k*, the power law turnover point in the discreet power spectrum of the random number sequence and on the lag-1 autocorrelation time of the random number sequence.

  5. Required Levels of Catalysis for Emergence of Autocatalytic Sets in Models of Chemical Reaction Systems

    OpenAIRE

    2011-01-01

    The formation of a self-sustaining autocatalytic chemical network is a necessary but not sufficient condition for the origin of life. The question of whether such a network could form “by chance” within a sufficiently complex suite of molecules and reactions is one that we have investigated for a simple chemical reaction model based on polymer ligation and cleavage. In this paper, we extend this work in several further directions. In particular, we investigate in more detail the levels of cat...

  6. Modeling cardiac mechano-electrical feedback using reaction-diffusion-mechanics systems

    Science.gov (United States)

    Keldermann, R. H.; Nash, M. P.; Panfilov, A. V.

    2009-06-01

    In many practically important cases, wave propagation described by the reaction-diffusion equation initiates deformation of the medium. Mathematically, such processes are described by coupled reaction-diffusion-mechanics (RDM) systems. RDM systems were recently used to study the effects of deformation on wave propagation in cardiac tissue, so called mechano-electrical feedback (MEF). In this article, we review the results of some of these studies, in particular those relating to the effects of deformation on pacemaker activity and spiral wave dynamics in the heart. We also provide brief descriptions of the numerical methods used, and the underlying cardiac physiology.

  7. DYNAMIC MATHEMATICAL MODELLING OF REACTION KINETICS FOR CYCLODEXTRINS PRODUCTION FROM DIFFERENT STARCH SOURCES USING BACILLUS MACERANS CYCLODEXTRIN GLUCANOTRANSFERASE

    Directory of Open Access Journals (Sweden)

    Syahinaz Shahrazi

    2013-01-01

    Full Text Available This study relates to the mathematical modelling of enzymatic production of Cyclodextrins (CDs by Cyclodextrin Glucanotransferase (CGTase from Bacillus macerans. The experiments were carried out in batch mode using different starch sources and the results were used to estimate unknown parameters using linearization and dynamic simulation methods. α- and β-CD produced from tapioca were found to give the highest Michaelis-Menten constant, KM,i of 58.23 and 54.07 g L-1, respectively and maximum velocity, Vmax,i of 3.45 and 2.76 g L-1.min, respectively, while sago resulted in the highest KM,i and Vmax,i values of 342.35 g L-1 and 5.97 g L-1.min, respectively, for γ-CD obtained by the linearization method. Value of product inhibition, K1,i and CD degradation coefficient rate, δCD,i, were estimated using dynamic simulation, indicating that exponential reaction kinetics could be fitted better with the experimental data. Sensitivity analysis revealed that the product inhibition parameter in the exponential reaction kinetic equation is more significant in the process. For validation, the production of CDs by fed batch method was undertaken and starch and enzyme were added into the reaction medium. Then, the predicted profiles generated by simulation were compared with the experimental values. The proposed exponential reaction kinetics shows good fitting with the experimental data.

  8. Comparison between phenomenological and ab-initio reaction and relaxation models in DSMC

    Science.gov (United States)

    Sebastião, Israel B.; Kulakhmetov, Marat; Alexeenko, Alina

    2016-11-01

    New state-specific vibrational-translational energy exchange and dissociation models, based on ab-initio data, are implemented in direct simulation Monte Carlo (DSMC) method and compared to the established Larsen-Borgnakke (LB) and total collision energy (TCE) phenomenological models. For consistency, both the LB and TCE models are calibrated with QCT-calculated O2+O data. The model comparison test cases include 0-D thermochemical relaxation under adiabatic conditions and 1-D normal shockwave calculations. The results show that both the ME-QCT-VT and LB models can reproduce vibrational relaxation accurately but the TCE model is unable to reproduce nonequilibrium rates even when it is calibrated to accurate equilibrium rates. The new reaction model does capture QCT-calculated nonequilibrium rates. For all investigated cases, we discuss the prediction differences based on the new model features.

  9. Modeling and Fuzzy Logic Control of an Active Reaction Compensating Platform System

    Directory of Open Access Journals (Sweden)

    Y.J. Lin

    1995-01-01

    Full Text Available This article presents the application of the fuzzy logic (FL concept to the active control of a multiple degree of freedom reaction compensating platform system that is designed and used for isolating vibratory disturbances of space-based devices. The physical model used is a scaled down two-plate platform system. In this work, simulation is performed and presented. According to the desired performance specifications, a full range of investigation regarding the development of an FL stabilization controller for the system is conducted. Specifically, the study includes four stages: comprehensive dynamic modeling of the reaction compensating system; analysis of the dynamic responses of the platform system when it is subjected to various disturbances; design of an FL controller capable of filtering the vibratory disturbances transmitted to the bottom plate of the platform system; performance evaluation of the developed FL controller through computer simulations. To simplify the simulation work, the system model is linearized and the system component parameter variations are not considered. The performance of the FL controller is tested by exciting the system with an impulsive force applied at an arbitrarily chosen point on the top plate. It is shown that the proposed FL controller is robust in that the resultant active system is well stabilized when subjected to a random external disturbance. The comparative study of the performances of the FL controlled active reaction and passive reaction compensating systems also reveals that the FL controlled system achieves significant improvements in reducing vibratory accelerations over passive systems.

  10. Antioxidant and antimicrobial activity of Maillard reaction products from xylan with chitosan/chitooligomer/glucosamine hydrochloride/taurine model systems.

    Science.gov (United States)

    Wu, Shuping; Hu, Jiao; Wei, Liuting; Du, Yumin; Shi, Xiaowen; Zhang, Lina

    2014-04-01

    The structure, UV absorbance, browning intensity, fluorescence changes, antioxidant activity and antimicrobial assessment of Maillard reaction products (MRPs) derived from xylan with chitosan, chitooligomer, glucosamine hydrochloride and taurine model systems were evaluated. The results revealed that all MRPs had similar infrared spectra and molecular structures. MRPs from different model systems on the UV absorbance at 294 nm after heated 90 min and browning intensity at 420 nm showed the similar law: xylan-taurine > xylan-glucosamine hydrochloride > xylan-chitooligomer > xylan-chitosan, and the order of DPPH scavenging activity of MRPs was as follows: xylan-chitosan > xylan-chitooligomer > xylan-glucosamine hydrochloride > xylan-taurine, which revealed that the properties of MRPs were closely related to molecular weight of model systems. Moreover, the highest radical scavenging activity of MRPs from xylan with chitosan/chitooligomer/glucosamine hydrochloride/taurine model systems was 65.9%, 63.7%, 46.4% and 42.5%, respectively.

  11. Elevated creatinine after ingestion of model aviation fuel: interference with the Jaffe reaction by nitromethane.

    Science.gov (United States)

    Booth, C; Naidoo, D; Rosenberg, A; Kainer, G

    1999-10-01

    A 2 years 9 month-old-boy who ingested model aviation fuel was found to have an elevated serum creatinine concentration of 0.53 mmol/L (normal range 0.02-0.05 mmol/L) by the Jaffe (alkaline picrate) reaction. However, when the creatinine concentration was measured using a specific enzymatic assay, it was within the normal range. It was shown that nitromethane, a constituent of aviation fuel, interferes with the Jaffe reaction, leading to a falsely elevated creatinine reading. This phenomenon has been reported only once previously and, despite its potential clinical importance, nitromethane does not appear in published lists of substances that interfere with the Jaffe reaction.

  12. Description of the proton and neutron radiative capture reactions in the Gamow shell model

    CERN Document Server

    Fossez, K; Płoszajczak, M; Jaganathen, Y

    2015-01-01

    We formulate the Gamow shell model (GSM) in coupled-channel (CC) representation for the description of proton/neutron radiative capture reactions and present the first application of this new formalism for the calculation of cross-sections in mirror reactions 7Be(p,gamma)8B and 7Li(n,gamma)8Li. The GSM-CC formalism is applied to a translationally-invariant Hamiltonian with an effective finite-range two-body interaction. Reactions channels are built by GSM wave functions for the ground state 3/2- and the first excited state 1/2- of 7Be/7Li and the proton/neutron wave function expanded in different partial waves.

  13. A simple model for lamellar peritectic coupled growth with peritectic reaction

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The lamellar peritectic coupled growth in Fe-Ni peritectic system was investigated using the equilibrium Boettinger-Jackson-Hunt model.It was found that the slope of the undercooling vs.lamellar spacing is very near zero around the minimum overheating,and the coupled growth can exist under this condition even if the slope of the undercooling vs.lamellar spacing curve is slightly smaller than zero.In addition,the peritectic reaction can never reach completion during the peritectic coupled growth.So the equilibrium peritectic coupled growth was modified by considering the incompletion of the peritectic reaction.It was shown that when the fractions of the peritectic reaction reach 60%-80% completion,the calculated undercooling vs.lamellar spacing curves agree well with the experimental obser-vations in the directionally solidified Fe-Ni alloys.

  14. Joint Symptoms, Aromatase Inhibitor-Related Adverse Reactions, Are Indirectly Associated with Decreased Serum Estradiol

    OpenAIRE

    Junko Honda; Miyuki Kanematsu; Misako Nakagawa; Masako Takahashi; Taeko Nagao; Akira Tangoku; Mitsunori Sasa

    2011-01-01

    Background. Joint symptoms (JSs) are problematic adverse drug reactions (ADRs) of aromatase inhibitors (AIs). Involvement of decreased serum estradiol (SE) has been suggested. Patients and Methods. 104 postmenopausal breast cancer patients administered an AI were prospectively investigated regarding various clinical parameters, JS and hot flashes as ADRs, and the SE level. Results. JS manifested in 31.7% of patients and hot flashes in 18.3%. Chi-square testing showed a significantly hig...

  15. Modeling Bimolecular Reactions and Transport in Porous Media Via Particle Tracking

    Energy Technology Data Exchange (ETDEWEB)

    Dong Ding; David Benson; Amir Paster; Diogo Bolster

    2012-01-01

    We use a particle-tracking method to simulate several one-dimensional bimolecular reactive transport experiments. In this numerical method, the reactants are represented by particles: advection and dispersion dominate the flow, and molecular diffusion dictates, in large part, the reactions. The particle/particle reactions are determined by a combination of two probabilities dictated by the physics of transport and energetics of reaction. The first is that reactant particles occupy the same volume over a short time interval. The second is the conditional probability that two collocated particles favorably transform into a reaction. The first probability is a direct physical representation of the degree of mixing in an advancing displacement front, and as such lacks empirical parameters except for the user-defined number of particles. This number can be determined analytically from concentration autocovariance, if this type of data is available. The simulations compare favorably to two physical experiments. In one, the concentration of product, 1,2-naphthoquinoe-4-aminobenzene (NQAB) from reaction between 1,2-naphthoquinone-4-sulfonic acid (NQS) and aniline (AN), was measured at the outflow of a column filled with glass beads at different times. In the other, the concentration distribution of reactants (CuSO_4 and EDTA^{4-}) and products (CuEDTA^{4-}) were quantified by snapshots of transmitted light through a column packed with cryloite sand. The thermodynamic rate coefficient in the latter experiment was 10^7 times greater than the former experiment, making it essentially instantaneous. When compared to the solution of the advection-dispersion-reaction equation (ADRE) with the well-mixed reaction coefficient, the experiments and the particle-tracking simulations showed on the order of 20% to 40% less overall product, which is attributed to poor mixing. The poor mixing also leads to higher product concentrations on the edges of the mixing zones, which the particle

  16. Extended Parker-Sochacki method for Michaelis-Menten enzymatic reaction model.

    Science.gov (United States)

    Abdelrazik, Ismail M; Elkaranshawy, Hesham A

    2016-03-01

    In this article, a new approach--namely, the extended Parker-Sochacki method (EPSM)--is presented for solving the Michaelis-Menten nonlinear enzymatic reaction model. The Parker-Sochacki method (PSM) is combined with a new resummation method called the Sumudu-Padé resummation method to obtain approximate analytical solutions for the model. The obtained solutions by the proposed approach are compared with the solutions of PSM and the Runge-Kutta numerical method (RKM). The comparison proves the practicality, efficiency, and correctness of the presented approach. It serves as a basis for solving other nonlinear biochemical reaction models in the future. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways

    Science.gov (United States)

    Mathew, Kiran; Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Arias, T. A.; Hennig, Richard G.

    2014-02-01

    Solid-liquid interfaces are at the heart of many modern-day technologies and provide a challenge to many materials simulation methods. A realistic first-principles computational study of such systems entails the inclusion of solvent effects. In this work, we implement an implicit solvation model that has a firm theoretical foundation into the widely used density-functional code Vienna ab initio Software Package. The implicit solvation model follows the framework of joint density functional theory. We describe the framework, our algorithm and implementation, and benchmarks for small molecular systems. We apply the solvation model to study the surface energies of different facets of semiconducting and metallic nanocrystals and the SN2 reaction pathway. We find that solvation reduces the surface energies of the nanocrystals, especially for the semiconducting ones and increases the energy barrier of the SN2 reaction.

  18. Generalized phenomenological model for the effect of electromigration on interfacial reaction

    Science.gov (United States)

    Hsu, Chia-Ming; Wong, David Shan-Hill; Chen, Sinn-Wen

    2007-07-01

    Intermetallic compound (IMC) formation is important for the reliability of microelectronic devices. In this work, a generalized phenomenological model was developed to explain the effects of electromigration on IMC growth by considering reaction and diffusion of two species. When both reaction and mass transfer are important, the model predicts cathode enhancement and anode thinning if the electromigration effect on the dominant diffusion species is more pronounced. Cathode suppression and anode enhancement occur when the electromigration effect on the minor diffusion species is more pronounced. Simultaneous cathode and anode suppressions happen when there are two diffusion species and the diffusion and electromigration fluxes are comparable. Simultaneous cathode and anode enhancements occur when mass transfer is the limiting step and diffusion flux is negligible compared to electromigration. This model was found to be consistent with experiment data on IMC growth in the literature given the limited amount of information on effective charge of various species.

  19. Handbook of latent variable and related models

    CERN Document Server

    Lee, Sik-Yum

    2011-01-01

    This Handbook covers latent variable models, which are a flexible class of models for modeling multivariate data to explore relationships among observed and latent variables.- Covers a wide class of important models- Models and statistical methods described provide tools for analyzing a wide spectrum of complicated data- Includes illustrative examples with real data sets from business, education, medicine, public health and sociology.- Demonstrates the use of a wide variety of statistical, computational, and mathematical techniques.

  20. An analytical model of hydrogen evolution and oxidation reactions on electrodes partially covered with a catalyst.

    Science.gov (United States)

    Kemppainen, Erno; Halme, Janne; Lund, Peter D

    2016-05-11

    Our previous theoretical study on the performance limits of the platinum (Pt) nanoparticle catalyst for the hydrogen evolution reaction (HER) had shown that the mass transport losses at a partially catalyst-covered planar electrode are independent of the catalyst loading. This suggests that the two-dimensional (2D) numerical model used could be simplified to a one-dimensional (1D) model to provide an easier but equally accurate description of the operation of these HER electrodes. In this article, we derive an analytical 1D model and show that it indeed gives results that are practically identical to the 2D numerical simulations. We discuss the general principles of the model and how it can be used to extend the applicability of existing electrochemical models of planar electrodes to low catalyst loadings suitable for operating photoelectrochemical devices under unconcentrated sunlight. Since the mass transport losses of the HER are often very sensitive to the H2 concentration, we also discuss the limiting current density of the hydrogen oxidation reaction (HOR) and how it is not necessarily independent of the reaction kinetics. The results give insight into the interplay of kinetic and mass-transport limitations at HER/HOR electrodes with implications for the design of kinetic experiments and the optimization of catalyst loadings in the photoelectrochemical cells.

  1. Transport-reaction model for defect and carrier behavior within displacement cascades in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, William R.; Myers, Samuel Maxwell,

    2014-02-01

    A model is presented for recombination of charge carriers at displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers and defects within a representative spherically symmetric cluster. The initial radial defect profiles within the cluster were chosen through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Charging of the defects can produce high electric fields within the cluster which may influence transport and reaction of carriers and defects, and which may enhance carrier recombination through band-to-trap tunneling. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to pulsed neutron irradiation.

  2. Parallel iterative reaction path optimization in ab initio quantum mechanical/molecular mechanical modeling of enzyme reactions.

    Science.gov (United States)

    Liu, Haiyan; Lu, Zhenyu; Cisneros, G Andres; Yang, Weitao

    2004-07-08

    The determination of reaction paths for enzyme systems remains a great challenge for current computational methods. In this paper we present an efficient method for the determination of minimum energy reaction paths with the ab initio quantum mechanical/molecular mechanical approach. Our method is based on an adaptation of the path optimization procedure by Ayala and Schlegel for small molecules in gas phase, the iterative quantum mechanical/molecular mechanical (QM/MM) optimization method developed earlier in our laboratory and the introduction of a new metric defining the distance between different structures in the configuration space. In this method we represent the reaction path by a discrete set of structures. For each structure we partition the atoms into a core set that usually includes the QM subsystem and an environment set that usually includes the MM subsystem. These two sets are optimized iteratively: the core set is optimized to approximate the reaction path while the environment set is optimized to the corresponding energy minimum. In the optimization of the core set of atoms for the reaction path, we introduce a new metric to define the distances between the points on the reaction path, which excludes the soft degrees of freedom from the environment set and includes extra weights on coordinates describing chemical changes. Because the reaction path is represented by discrete structures and the optimization for each can be performed individually with very limited coupling, our method can be executed in a natural and efficient parallelization, with each processor handling one of the structures. We demonstrate the applicability and efficiency of our method by testing it on two systems previously studied by our group, triosephosphate isomerase and 4-oxalocrotonate tautomerase. In both cases the minimum energy paths for both enzymes agree with the previously reported paths.

  3. First-principles modeling of catalysts: novel algorithms and reaction mechanisms

    Science.gov (United States)

    Richard, Bryan Goldsmith

    A molecular level understanding of a reaction mechanism and the computation of rates requires knowledge of the stable structures and the corresponding transition states that connect them. Temperature, pressure, and environment effects must be included to bridge the 'materials gap' so one can reasonably compare ab initio (first-principles, i.e., having no empirical parameters) predictions with experimental measurements. In this thesis, a few critical problems pertaining to ab initio modeling of catalytic systems are addressed; namely, 1) the issue of building representative models of isolated metal atoms grafted on amorphous supports, 2) modeling inorganic catalytic reactions in non-ideal solutions where the solvent participates in the reaction mechanism, and 3) bridging the materials gap using ab initio thermodynamics to predict the stability of supported nanoparticles under experimental reaction conditions. In Chapter I, a background on first-principles modeling of heterogeneous and homogenous catalysts is provided. Subsequently, to address the problem of modeling catalysis by isolated metal atoms on amorphous supports, we present in Chapter II a sequential-quadratic programming algorithm that systematically predicts the structure and reactivity of isolated active sites on insulating amorphous supports. Modeling solution phase reactions is also a considerable challenge for first-principles modeling, yet when done correctly it can yield critical kinetic and mechanistic insight that can guide experimental investigations. In Chapter III, we examine the formation of peroxorhenium complexes by activation of H2O2, which is key in selective oxidation reactions catalyzed by CH3ReO3 (methyltrioxorhenium, MTO). New experiments and density functional theory (DFT) calculations were conducted to better understand the activation of H2O2 by MTO and to provide a strong experimental foundation for benchmarking computational studies involving MTO and its derivatives. It was found

  4. Radiative capture reaction for 17Ne formation within a full three-body model

    Science.gov (United States)

    Casal, J.; Garrido, E.; de Diego, R.; Arias, J. M.; Rodríguez-Gallardo, M.

    2016-11-01

    Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can trigger the rp-process in type I x-ray bursts. In this environment, a competition between 15O(α ,γ )19Ne and the two-proton capture reaction 15O(2 p ,γ )17Ne is expected. Purpose: Determine the three-body radiative capture reaction rate for 17Ne formation including sequential and direct, resonant and nonresonant contributions on an equal footing. Method: Two different discretization methods have been applied to generate 17Ne states in a full three-body model: the analytical transformed harmonic oscillator method and the hyperspherical adiabatic expansion method. The binary p -15O interaction has been adjusted to reproduce the known spectrum of the unbound 16F nucleus. The dominant E 1 contributions to the 15O(2 p ,γ )17Ne reaction rate have been calculated from the inverse photodissociation process. Results: Three-body calculations provide a reliable description of 17Ne states. The agreement with the available experimental data on 17Ne is discussed. It is shown that the 15O(2 p ,γ )17Ne reaction rates computed within the two methods agree in a broad range of temperatures. The present calculations are compared with a previous theoretical estimation of the reaction rate. Conclusions: It is found that the full three-body model provides a reaction rate several orders of magnitude larger than the only previous estimation. The implications for the rp-process in type I x-ray bursts should be investigated.

  5. Multi-reaction-channel fitting calculations in a coupled-channel model: Photoinduced strangeness production

    Indian Academy of Sciences (India)

    O Scholten; A Usov

    2010-08-01

    To describe photo- and meson-induced reactions on the nucleon, one is faced with a rather extensive coupled-channel problem. Ignoring the effects of channel coupling, as one would do in describing a certain reaction at the tree level, invariably creates a large inconsistency between the different reactions that are described. In addition, the imaginary parts of the amplitude, which are related through the optical theorem, to total cross-sections, are directly reflected in certain polarization observables. Performing a full coupled-channel calculation thus offers the possibility to implement the maximum number of constraints. The drawback one is faced with is to arrive at a simultaneous fit of a large number of reaction channels. While some of the parameters are common to many reactions, one is still faced with the challenge to optimize a large number of parameters in a highly non-linear calculation. Here we show that such an approach is possible and present some results for photoinduced strangeness production.

  6. They made you perfect: A test of the Social Reaction Model of Perfectionism.

    Science.gov (United States)

    Wilson, Claire; Hunter, Simon C; Rasmussen, Susan; McGowan, Allison

    2015-01-01

    Perfectionism serves as a mediator in the relationship between difficult life experiences and psychological distress, but to date no research has examined the effect of recalled peer victimization on perfectionism and adult depressive symptomatology (DS). The present study assessed the Social Reaction Model of Perfectionism (SRMP; Flett, Hewitt, Oliver, & Macdonald (2002b). Perfectionism in children and their parents: A developmental analysis. In G. L. Flett and P. L. Hewitt (Eds.), Perfectionism: Theory, research, and treatment (pp. 89-132). Washington: American Psychological Association), which proposes that perfectionism (self-oriented, other-oriented and socially prescribed perfectionism) results from harsh experiences. This may include experiences of peer victimization (physical, verbal and indirect). The model was extended to also include adult DS and rumination (brooding and reflection). Self-report questionnaires measuring recalled childhood experiences of peer victimization (Owens, Daly, & Slee (2005). Aggressive Behavior, 31, 1-12. doi: 10.1002/ab.20045), current trait perfectionism (Hewitt & Flett (1991). Journal of Personality and Social Psychology, 60, 456-470. http://dx.doi.org/10.1037//0022-3514.60.3.456), rumination (Nolen-Hoeksema & Morrow (1991). Journal of Personality and Social Psychology, 61, 115-121. doi: 10.1037/0022-3514.61.1.115) and DS (Radloff (1977). Applied Psychological Measurement, 1, 386-401. http://dx.doi.org/10.1177/014662167700100306) were completed by 338 adult participants (54% female). Path-analyses revealed recalled indirect victimization to be associated with adults' self-oriented and socially prescribed perfectionism. However, only socially prescribed perfectionism mediated the relation between recalled indirect victimization and adult DS. Brooding rumination also mediated the effect of socially prescribed perfectionism upon DS. The findings support the SRMP, and extend the theory to include the effects of perfectionism on

  7. AURORA: A FORTRAN program for modeling well stirred plasma and thermal reactors with gas and surface reactions

    Energy Technology Data Exchange (ETDEWEB)

    Meeks, E.; Grcar, J.F.; Kee, R.J. [Sandia National Labs., Livermore, CA (United States). Thermal and Plasma Processes Dept.; Moffat, H.K. [Sandia National Labs., Albuquerque, NM (United States). Surface Processing Sciences Dept.

    1996-02-01

    The AURORA Software is a FORTRAN computer program that predicts the steady-state or time-averaged properties of a well mixed or perfectly stirred reactor for plasma or thermal chemistry systems. The software was based on the previously released software, SURFACE PSR which was written for application to thermal CVD reactor systems. AURORA allows modeling of non-thermal, plasma reactors with the determination of ion and electron concentrations and the electron temperature, in addition to the neutral radical species concentrations. Well stirred reactors are characterized by a reactor volume, residence time or mass flow rate, heat loss or gas temperature, surface area, surface temperature, the incoming temperature and mixture composition, as well as the power deposited into the plasma for non-thermal systems. The model described here accounts for finite-rate elementary chemical reactions both in the gas phase and on the surface. The governing equations are a system of nonlinear algebraic relations. The program solves these equations using a hybrid Newton/time-integration method embodied by the software package TWOPNT. The program runs in conjunction with the new CHEMKIN-III and SURFACE CHEMKIN-III packages, which handle the chemical reaction mechanisms for thermal and non-thermal systems. CHEMKIN-III allows for specification of electron-impact reactions, excitation losses, and elastic-collision losses for electrons.

  8. Reaction-Multi Diffusion Model for Nutrient Release and Autocatalytic Degradation of PLA-Coated Controlled-Release Fertilizer

    Directory of Open Access Journals (Sweden)

    Sayed Ameenuddin Irfan

    2017-03-01

    Full Text Available A mathematical model for the reaction-diffusion equation is developed to describe the nutrient release profiles and degradation of poly(lactic acid (PLA-coated controlled-release fertilizer. A multi-diffusion model that consists of coupled partial differential equations is used to study the diffusion and chemical reaction (autocatalytic degradation simultaneously. The model is solved using an analytical-numerical method. Firstly, the model equation is transformed using the Laplace transformation as the Laplace transform cannot be inverted analytically. Numerical inversion of the Laplace transform is used by employing the Zakian method. The solution is useful in predicting the nutrient release profiles at various diffusivity, concentration of extraction medium, and reaction rates. It also helps in explaining the transformation of autocatalytic concentration in the coating material for various reaction rates, times of reaction, and reaction-multi diffusion. The solution is also applicable to the other biodegradable polymer-coated controlled-release fertilizers.

  9. A more robust model of the biodiesel reaction, allowing identification of process conditions for significantly enhanced rate and water tolerance.

    Science.gov (United States)

    Eze, Valentine C; Phan, Anh N; Harvey, Adam P

    2014-03-01

    A more robust kinetic model of base-catalysed transesterification than the conventional reaction scheme has been developed. All the relevant reactions in the base-catalysed transesterification of rapeseed oil (RSO) to fatty acid methyl ester (FAME) were investigated experimentally, and validated numerically in a model implemented using MATLAB. It was found that including the saponification of RSO and FAME side reactions and hydroxide-methoxide equilibrium data explained various effects that are not captured by simpler conventional models. Both the experiment and modelling showed that the "biodiesel reaction" can reach the desired level of conversion (>95%) in less than 2min. Given the right set of conditions, the transesterification can reach over 95% conversion, before the saponification losses become significant. This means that the reaction must be performed in a reactor exhibiting good mixing and good control of residence time, and the reaction mixture must be quenched rapidly as it leaves the reactor.

  10. Improved Quantum Molecular Dynamics Model and its Application to Fusion Reaction Near Barrier

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An improved quantum molecular dynamics model is proposed. By using this model, the properties of ground state of nuclei from 6Li to 208Pb can be described very well with one set of parameters. The fusion reactions for 40Ca+90Zr, 40Ca+96Zr and 48Ca+90Zr at the energy near the barrier are studied by this model. The experimental data of the fusion cross sections for 40Ca+90,96Zr at the energy near the barrier can be reproduced remarkably well without introducing any new parameters. The mechanism

  11. An Interface Stretching-Diffusion Model for Mixing-Limited Reactions During Convective Mixing

    Science.gov (United States)

    Hidalgo, J. J.; Dentz, M.; Cabeza, Y.; Carrera, J.

    2014-12-01

    We study the behavior of mixing-limited dissolution reactions under the unstable flow conditions caused by a Rayleigh-Bénard convective instability in a two fluids system. The reactions produce a dissolution pattern that follows the ascending fluids's interface where the largest concentration gradients and maximum mixing are found. Contrary to other chemical systems, the mixing history engraved by the dissolution does not map out the fingering geometry of the unstable flow. The temporal scaling of the mixing Χ and the reaction rate r are explained by a stretching-diffusion model of the interface between the fluids. The model accurately reproduces the three observed regimes: a diffusive regime at which Χ, r ~ t-1/2; a convective regime of at which the interface contracts to the Batchelor scale resulting in a constant Χf and r independent of the Rayleigh number; and an attenuated convection regime in which Χ and r decay faster than diffusion as t-3/2 and t-1, respectevely, because of the decompression of the interface and weakened reactions caused by the accumulation of dissolved fluid below the interface.

  12. Beyond frontier molecular orbital theory: a systematic electron transfer model (ETM) for polar bimolecular organic reactions.

    Science.gov (United States)

    Cahill, Katharine J; Johnson, Richard P

    2013-03-01

    Polar bimolecular reactions often begin as charge-transfer complexes and may proceed with a high degree of electron transfer character. Frontier molecular orbital (FMO) theory is predicated in part on this concept. We have developed an electron transfer model (ETM) in which we systematically transfer one electron between reactants and then use density functional methods to model the resultant radical or radical ion intermediates. Sites of higher reactivity are revealed by a composite spin density map (SDM) of odd electron character on the electron density surface, assuming that a new two-electron bond would occur preferentially at these sites. ETM correctly predicts regio- and stereoselectivity for a broad array of reactions, including Diels-Alder, dipolar and ketene cycloadditions, Birch reduction, many types of nucleophilic additions, and electrophilic addition to aromatic rings and polyenes. Conformational analysis of radical ions is often necessary to predict reaction stereochemistry. The electronic and geometric changes due to one-electron oxidation or reduction parallel the reaction coordinate for electrophilic or nucleophilic addition, respectively. The effect is more dramatic for one-electron reduction.

  13. A fractional model of a dynamical Brusselator reaction-diffusion system arising in triple collision and enzymatic reactions

    Science.gov (United States)

    Singh, Jagdev; Rashidi, M. M.; Kumar, Devendra; Swroop, Ram

    2016-12-01

    In this paper, we study a dynamical Brusselator reaction-diffusion system arising in triple collision and enzymatic reactions with time fractional Caputo derivative. The present article involves a more generalized effective approach, proposed for the Brusselator system say q-homotopy analysis transform method (q-HATM), providing the family of series solutions with nonlocal generalized effects. The convergence of the q-HATM series solution is adjusted and controlled by auxiliary parameter ℏ and asymptotic parameter n. The numerical results are demonstrated graphically. The outcomes of the study show that the q-HATM is computationally very effective and accurate to analyze nonlinear fractional differential equations.

  14. The effect of learning models and emotional intelligence toward students learning outcomes on reaction rate

    Science.gov (United States)

    Sutiani, Ani; Silitonga, Mei Y.

    2017-08-01

    This research focused on the effect of learning models and emotional intelligence in students' chemistry learning outcomes on reaction rate teaching topic. In order to achieve the objectives of the research, with 2x2 factorial research design was used. There were two factors tested, namely: the learning models (factor A), and emotional intelligence (factor B) factors. Then, two learning models were used; problem-based learning/PBL (A1), and project-based learning/PjBL (A2). While, the emotional intelligence was divided into higher and lower types. The number of population was six classes containing 243 grade X students of SMAN 10 Medan, Indonesia. There were 15 students of each class were chosen as the sample of the research by applying purposive sampling technique. The data were analyzed by applying two-ways analysis of variance (2X2) at the level of significant α = 0.05. Based on hypothesis testing, there was the interaction between learning models and emotional intelligence in students' chemistry learning outcomes. Then, the finding of the research showed that students' learning outcomes in reaction rate taught by using PBL with higher emotional intelligence is higher than those who were taught by using PjBL. There was no significant effect between students with lower emotional intelligence taught by using both PBL and PjBL in reaction rate topic. Based on the finding, the students with lower emotional intelligence were quite hard to get in touch with other students in group discussion.

  15. Microsolvated transition state models for improved insight into chemical properties and reaction mechanisms.

    Science.gov (United States)

    Sunoj, Raghavan B; Anand, Megha

    2012-10-05

    Over the years, several methods have been developed to effectively represent the chemical behavior of solutes in solvents. The environmental effects arising due to solvation can generally be achieved either through inclusion of discrete solvent molecules or by inscribing into a cavity in a homogeneous and continuum dielectric medium. In both these approaches of computational origin, the perturbations on the solute induced by the surrounding solvent are at the focus of the problem. While the rigor and method of inclusion of solvent effects vary, such solvation models have found widespread applications, as evident from modern chemical literature. A hybrid method, commonly referred to as cluster-continuum model (CCM), brings together the key advantages of discrete and continuum models. In this perspective, we intend to highlight the latent potential of CCM toward obtaining accurate estimates on a number of properties as well as reactions of contemporary significance. The objective has generally been achieved by choosing illustrative examples from the literature, besides expending efforts to bring out the complementary advantages of CCM as compared to continuum or discrete solvation models. The majority of examples emanate from the prevalent applications of CCM to organic reactions, although a handful of interesting organometallic reactions have also been discussed. In addition, increasingly accurate computations of properties like pK(a) and solvation of ions obtained using the CCM protocol are also presented.

  16. Mathematical Modeling and Dynamic Simulation of Metabolic Reaction Systems Using Metabolome Time Series Data

    Directory of Open Access Journals (Sweden)

    Kansuporn eSriyudthsak

    2016-05-01

    Full Text Available The high-throughput acquisition of metabolome data is greatly anticipated for the complete understanding of cellular metabolism in living organisms. A variety of analytical technologies have been developed to acquire large-scale metabolic profiles under different biological or environmental conditions. Time series data are useful for predicting the most likely metabolic pathways because they provide important information regarding the accumulation of metabolites, which implies causal relationships in the metabolic reaction network. Considerable effort has been undertaken to utilize these data for constructing a mathematical model merging system properties and quantitatively characterizing a whole metabolic system in toto. However, there are technical difficulties between benchmarking the provision and utilization of data. Although hundreds of metabolites can be measured, which provide information on the metabolic reaction system, simultaneous measurement of thousands of metabolites is still challenging. In addition, it is nontrivial to logically predict the dynamic behaviors of unmeasurable metabolite concentrations without sufficient information on the metabolic reaction network. Yet, consolidating the advantages of advancements in both metabolomics and mathematical modeling remain to be accomplished. This review outlines the conceptual basis of and recent advances in technologies in both the research fields. It also highlights the potential for constructing a large-scale mathematical model by estimating model parameters from time series metabolome data in order to comprehensively understand metabolism at the systems level.

  17. Static and dynamical critical behavior of the monomer-monomer reaction model with desorption

    Science.gov (United States)

    da Costa, E. C.; Rusch, Flávio Roberto

    2016-06-01

    We studied in this work the monomer-monomer reaction model on a linear chain. The model is described by the following reaction: A + B → AB, where A and B are two monomers that arrive at the surface with probabilities yA and yB, respectively, and we have considered desorption of the monomer B with probability α. The model is studied in the adsorption controlled limit where the reaction rate is infinitely larger than the adsorption rate. We employ site and pair mean-field approximations as well as static and dynamical Monte Carlo simulations. We show that the model exhibits a continuous phase transition between an active steady state and an A-absorbing state, when the parameter yA is varied through a critical value, which depends on the value of α. Monte Carlo simulations and finite-size scaling analysis near the critical point are used to determine the static critical exponents β and ν⊥ and the dynamical critical exponents ν∥ and z. The results found for the monomer-monomer reaction model with B desorption, in the linear chain, are different from those found by E. V. Albano (Albano, 1992) and are in accordance with the values obtained by Jun Zhuo and Sidney Redner (Zhuo and Redner, 1993), and endorse the conjecture of Grassberger, which states that any system undergoing a continuous phase transition from an active steady state to a single absorbing state, exhibits the same critical behavior of the directed percolation universality class.

  18. Boundary Relations, Unitary Colligations, and Functional Models

    NARCIS (Netherlands)

    Behrndt, Jussi; Hassi, Seppo; de Snoo, Henk

    2009-01-01

    Recently a new notion, the so-called boundary relation, has been introduced involving an analytic object, the so-called Weyl family. Weyl families and boundary relations establish a link between the class of Nevanlinna families and unitary relations acting from one Krein in space, a basic (state) sp

  19. Reaction norm model with unknown environmental covariate to analyze heterosis by environment interaction.

    Science.gov (United States)

    Su, G; Madsen, P; Lund, M S

    2009-05-01

    Crossbreeding is currently increasing in dairy cattle production. Several studies have shown an environment-dependent heterosis [i.e., an interaction between heterosis and environment (H x E)]. An H x E interaction is usually estimated from a few discrete environment levels. The present study proposes a reaction norm model to describe H x E interaction, which can deal with a large number of environment levels using few parameters. In the proposed model, total heterosis consists of an environment-independent part, which is described as a function of heterozygosity, and an environment-dependent part, which is described as a function of heterozygosity and environmental value (e.g., herd-year effect). A Bayesian approach is developed to estimate the environmental covariates, the regression coefficients of the reaction norm, and other parameters of the model simultaneously in both linear and nonlinear reaction norms. In the nonlinear reaction norm model, the H x E is approximated using linear splines. The approach was tested using simulated data, which were generated using an animal model with a reaction norm for heterosis. The simulation study includes 4 scenarios (the combinations of moderate vs. low heritability and moderate vs. low herd-year variation) of H x E interaction in a nonlinear form. In all scenarios, the proposed model predicted total heterosis very well. The correlation between true heterosis and predicted heterosis was 0.98 in the scenarios with low herd-year variation and 0.99 in the scenarios with moderate herd-year variation. This suggests that the proposed model and method could be a good approach to analyze H x E interactions and predict breeding values in situations in which heterosis changes gradually and continuously over an environmental gradient. On the other hand, it was found that a model ignoring H x E interaction did not significantly harm the prediction of breeding value under the simulated scenarios in which the variance for environment

  20. Li production in alpha-alpha reactions. [relation to gamma ray observation

    Science.gov (United States)

    Kozlovsky, B.; Ramaty, R.

    1974-01-01

    The cross section for Li-7 production in alpha-alpha reactions is shown to be increased by about a factor of 2 due to the excitation levels of Li-7 and Be-7 at 478 keV and 431 keV, respectively. The cross section for Li-6 production, however, remains the same as calculated on the basis of the detailed balance principle. The lines at 478 keV and 431 keV may link Li-7 production to feasible gamma-ray observations.