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Sample records for vfth relation enthalpy

  1. The Relation between Vaporization Enthalpies and Viscosities: Eyring's Theory Applied to Selected Ionic Liquids.

    Science.gov (United States)

    Bonsa, Anne-Marie; Paschek, Dietmar; Zaitsau, Dzmitry H; Emel'yanenko, Vladimir N; Verevkin, Sergey P; Ludwig, Ralf

    2017-05-19

    Key properties for the use of ionic liquids as electrolytes in batteries are low viscosities, low vapor pressure and high vaporization enthalpies. Whereas the measurement of transport properties is well established, the determination of vaporization enthalpies of these extremely low volatile compounds is still a challenge. At a first glance both properties seem to describe different thermophysical phenomena. However, eighty years ago Eyring suggested a theory which related viscosities and vaporization enthalpies to each other. The model is based on Eyring's theory of absolute reaction rates. Recent attempts to apply Eyring's theory to ionic liquids failed. The motivation of our study is to show that Eyring's theory works, if the assumptions specific for ionic liquids are fulfilled. For that purpose we measured the viscosities of three well selected protic ionic liquids (PILs) at different temperatures. The temperature dependences of viscosities were approximated by the Vogel-Fulcher-Tamann (VFT) relation and extrapolated to the high-temperature regime up to 600 K. Then the VFT-data could be fitted to the Eyring-model. The values of vaporization enthalpies for the three selected PILs predicted by the Eyring model have been very close to the experimental values measured by well-established techniques. We conclude that the Eyring theory can be successfully applied to the chosen set of PILs, if the assumption that ionic pairs of the viscous flow in the liquid and the ionic pairs in the gas phase are similar is fulfilled. It was also noticed that proper transfer of energies can be only derived if the viscosities and the vaporization energies are known for temperatures close to the liquid-gas transition temperature. The idea to correlate easy measurable viscosities of ionic liquids with their vaporization enthalpies opens a new way for a reliable assessment of these thermodynamic properties for a broad range of ionic liquids. © 2017 Wiley-VCH Verlag GmbH & Co. KGa

  2. Enthalpy studies

    Energy Technology Data Exchange (ETDEWEB)

    Mathias, P.M.; Stein, F.P.

    1983-09-01

    This report describes the evaluation and enhancement of the enthalpy model developed for the SRC-I process (as well as other coal liquefaction processes). The enthalpy model has been described in a previous report (Mathias and Monks, 1982). A key feature of the model is the proposed extended corresponding-states framework, obtained through the introduction of a new parameter, termed the polar parameter. It is usual practice to treat the essentially continuous coal-fluid mixture as a set of pseudocomponents, each defined by a narrow range in normal boiling point. The model developed by Mathias and Monks (1982) characterizes each pseudocomponent with the normal boiling point, specific gravity, and polar parameter. Mathias and Monks found that the model provided an excellent description of existing coal-fluid enthalpy data - if the polar parameter was chosen to best fit the data. However, use of the model in process design requires a predictive method for the polar parameter. ICRC is conducting a program to obtain enthalpy measurements in order to provide verification of the current design conditions for the SRC-I Demonstration Plant and data for developing reliable correlations (Mehta, et al., 1983). A majority of the data has been received, analysis of which is described in this report. Comparison of the model to data on three SRC-I 50/sup 0/F boiling fractions indicates, again, that the data is well correlated if the optimum value of the polar parameter is used. More importantly, this analysis has provided a reasonable basis to predict the values of the polar parameters for all the pseudocomponents employed in the simulation of the SRC-I process. The proposed model has provided encouraging agreement with experimental data, but final conclusions must await analysis of the entire set of data.

  3. Active Thermochemical Tables: Sequential Bond Dissociation Enthalpies of Methane, Ethane, and Methanol and the Related Thermochemistry.

    Science.gov (United States)

    Ruscic, Branko

    2015-07-16

    Active Thermochemical Tables (ATcT) thermochemistry for the sequential bond dissociations of methane, ethane, and methanol systems were obtained by analyzing and solving a very large thermochemical network (TN). Values for all possible C-H, C-C, C-O, and O-H bond dissociation enthalpies at 298.15 K (BDE298) and bond dissociation energies at 0 K (D0) are presented. The corresponding ATcT standard gas-phase enthalpies of formation of the resulting CHn, n = 4-0 species (methane, methyl, methylene, methylidyne, and carbon atom), C2Hn, n = 6-0 species (ethane, ethyl, ethylene, ethylidene, vinyl, ethylidyne, acetylene, vinylidene, ethynyl, and ethynylene), and COHn, n = 4-0 species (methanol, hydroxymethyl, methoxy, formaldehyde, hydroxymethylene, formyl, isoformyl, and carbon monoxide) are also presented. The ATcT thermochemistry of carbon dioxide, water, hydroxyl, and carbon, oxygen, and hydrogen atoms is also included, together with the sequential BDEs of CO2 and H2O. The provenances of the ATcT enthalpies of formation, which are quite distributed and involve a large number of relevant determinations, are analyzed by variance decomposition and discussed in terms of principal contributions. The underlying reasons for periodic appearances of remarkably low and/or unusually high BDEs, alternating along the dissociation sequences, are analyzed and quantitatively rationalized. The present ATcT results are the most accurate thermochemical values currently available for these species.

  4. Relation Between the Adsorbed Quantity and the Immersion Enthalpy in Catechol Aqueous Solutions on Activated Carbons

    Science.gov (United States)

    Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

    2012-01-01

    An activated carbon, CarbochemTM—PS230, was modified by chemical and thermal treatment in flow of H2, in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pKa. The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g−1 for catechol aqueous solutions in a range of 20 at 1500 mg·L−1. PMID:22312237

  5. Nuclear enthalpies

    Directory of Open Access Journals (Sweden)

    Rozynek Jacek

    2015-01-01

    Full Text Available Even small departures from a nuclear equilibrium density with constant nucleon masses require an increase of a nucleon enthalpy. This process can be described as volume corrections to a nucleon rest energy, which are proportional to pressure and absent in a standard Relativistic Mean Field (RMF with point-like nucleons. Bag model and RMF calculations show the modifications of nucleon mass, nucleon radius and a Parton Distribution Function (PDF of Nuclear Matter (NM above the saturation point originated from the pressure correction.

  6. Enthalpy studies. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Mathias, P.M.; Stein, F.P.

    1984-05-01

    This report describes the evaluation and enhancement of the enthalpy model developed for the SRC-I process (as well as the other coal-liquefaction processes). A preliminary version of the model was used in the Post-Baseline review of the SRC-I process design (Duffy et al., 1983), and the final version will be employed by APCI in the ASPEN PLUS Model of the SRC-I Demonstration Plant (APCI, 1984). ICRC, recognizing the need for thermophysical data on coal liquids and coal-fluid model compounds, embarked upon a 2-year experimental program. Specifically, the overall program objectives were to obtain vapor/liquid equilibrium (VLE) and enthalpy data to develop correlations and verify the designs of several important pieces of process equipment in the SRC-I demonstration plant. The enthalpy model uses a modification of the Peng-Robinson (1976) equation of state proposed by Mathias ad Copeman (1983). It was developed mainly from publicly available data on coal fluids and related model compounds (Mathias and Monks, 1982). The generalized (predictive) model has provided good agreement with experimental data on coal fluids. Surprisingly, the agreement with the data on model-compound mixtures is not as good. The practical conclusion is that, within the frame work of the present model, it is better to lump various types of components within the same pseudocomponent. The enthalpy model has achieved the main objective of an improved model for the design of several key heat exchangers in the SRC-I process. Further, the work has identified deficiencies in existing models, which suggest the focus of future research. 24 references.

  7. Assessment of enveloping distribution sampling to calculate relative free enthalpies of binding for eight netropsin-DNA duplex complexes in aqueous solution.

    Science.gov (United States)

    Hansen, Niels; Dolenc, Jožica; Knecht, Matthias; Riniker, Sereina; van Gunsteren, Wilfred F

    2012-03-05

    The performance of enveloping distribution sampling (EDS) simulations to estimate free enthalpy differences associated with seven alchemical transformations of A-T into G-C base pairs at the netropsin binding site in the minor groove of a 13-base pair DNA duplex in aqueous solution is evaluated. It is demonstrated that sufficient sampling can be achieved with a two-state EDS Hamiltonian even for large perturbations such as the simultaneous transformation of up to three A-T into three G-C base pairs. The two parameters required to define the EDS reference state Hamiltonian are obtained automatically using a modified version of a scheme presented in earlier work. The sensitivity of the configurational sampling to a variation of these parameters is investigated in detail. Although for relatively small perturbations, that is, one base pair, the free enthalpy estimate depends only weakly on the EDS parameters, the sensitivity is stronger for the largest perturbation. Yet, EDS offers various convenient measures to evaluate the degree of sampling and thus the reliability of the free enthalpy estimate and appears to be an efficient alternative to the conventional thermodynamic integration methodology to obtain free energy differences for molecular systems. Copyright © 2012 Wiley Periodicals, Inc.

  8. High enthalpy gas dynamics

    CERN Document Server

    Rathakrishnan, Ethirajan

    2014-01-01

    This is an introductory level textbook which explains the elements of high temperature and high-speed gas dynamics. written in a clear and easy to follow style, the author covers all the latest developments in the field including basic thermodynamic principles, compressible flow regimes and waves propagation in one volume covers theoretical modeling of High Enthalpy Flows, with particular focus on problems in internal and external gas-dynamic flows, of interest in the fields of rockets propulsion and hypersonic aerodynamics High enthalpy gas dynamics is a compulsory course for aerospace engine

  9. Enthalpy screen of drug candidates.

    Science.gov (United States)

    Schön, Arne; Freire, Ernesto

    2016-11-15

    The enthalpic and entropic contributions to the binding affinity of drug candidates have been acknowledged to be important determinants of the quality of a drug molecule. These quantities, usually summarized in the thermodynamic signature, provide a rapid assessment of the forces that drive the binding of a ligand. Having access to the thermodynamic signature in the early stages of the drug discovery process will provide critical information towards the selection of the best drug candidates for development. In this paper, the Enthalpy Screen technique is presented. The enthalpy screen allows fast and accurate determination of the binding enthalpy for hundreds of ligands. As such, it appears to be ideally suited to aid in the ranking of the hundreds of hits that are usually identified after standard high throughput screening. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. An enthalpy-temperature hybrid method for solving phase change problems and its application to polymer pyrolysis and ignition

    OpenAIRE

    Zhou, Ying-Ying; Fernandez-Pello, Carlos

    2000-01-01

    In this work, an enthalpy-temperature hybrid method is proposed for the numerical solution of generalized phase change problems, and applied to the prediction of polymer pyrolysis and ignition. The basic idea of this method is to treat both enthalpy and temperature as independent variables, and to solve the conservation equations and the constitutive equations (enthalpy-temperature relations) simultaneously. The formula of the enthalpy-temperature relations are not necessary the same for diff...

  11. Enthalpies of sublimation of fullerenes by thermogravimetry

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Herrera, Melchor; Campos, Myriam; Torres, Luis Alfonso; Rojas, Aarón, E-mail: arojas@cinvestav.mx

    2015-12-20

    Graphical abstract: - Highlights: • Enthalpies of sublimation of fullerenes were measured by thermogravimetry. • Results of enthalpies of sublimation are comparable with data reported in literature. • Not previously reported enthalpy of sublimation of C{sub 78} is supplied in this work. • Enthalpies of sublimation show a strong dependence with the number of carbon atoms in the cluster. • Enthalpies of sublimation are congruent with dispersion forces ruling cohesion of solid fullerene. - Abstract: The enthalpies of sublimation of fullerenes, as measured in the interval of 810–1170 K by thermogravimetry and applying the Langmuir equation, are reported. The detailed experimental procedure and its application to fullerenes C{sub 60}, C{sub 70}, C{sub 76}, C{sub 78} and C{sub 84} are supplied. The accuracy and uncertainty associated with the experimental results of the enthalpy of sublimation of these fullerenes show that the reliability of the measurements is comparable to that of other indirect high-temperature methods. The results also indicate that the enthalpy of sublimation increases proportionally to the number of carbon atoms in the cluster but there is also a strong correlation between the enthalpy of sublimation and the polarizability of each fullerene.

  12. Polymer-Polymer Miscibility and Enthalpy Relaxations

    NARCIS (Netherlands)

    Bosma, Martin; Brinke, Gerrit ten; Ellis, Thomas S.

    Annealing of polymers below the glass transition temperature results in a decrease in enthalpy that is recovered during heating. The enthalpy recovery is visible as an endothermic peak in a differential scanning calorimetry (DSC) scan. The position of this peak depends on the thermal treatment given

  13. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    It is a challenge to calorimetrically determine the glass transition temperature (Tg) of vitreous silica. Here, we demonstrate that this challenge mainly arises from the extremely high sensitivity of the Tg to the hydroxyl content, but also from decrease of the Tg with repeating the calorimetric...... scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hyperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas...

  14. Split-step eigenvector-following technique for exploring enthalpy landscapes at absolute zero.

    Science.gov (United States)

    Mauro, John C; Loucks, Roger J; Balakrishnan, Jitendra

    2006-03-16

    The mapping of enthalpy landscapes is complicated by the coupling of particle position and volume coordinates. To address this issue, we have developed a new split-step eigenvector-following technique for locating minima and transition points in an enthalpy landscape at absolute zero. Each iteration is split into two steps in order to independently vary system volume and relative atomic coordinates. A separate Lagrange multiplier is used for each eigendirection in order to provide maximum flexibility in determining step sizes. This technique will be useful for mapping the enthalpy landscapes of bulk systems such as supercooled liquids and glasses.

  15. Behavior of the Enthalpy of Adsorption in Nanoporous Materials Close to Saturation Conditions.

    Science.gov (United States)

    Torres-Knoop, Ariana; Poursaeidesfahani, Ali; Vlugt, Thijs J H; Dubbeldam, David

    2017-07-11

    Many important industrial separation processes based on adsorption operate close to saturation. In this regime, the underlying adsorption processes are mostly driven by entropic forces. At equilibrium, the entropy of adsorption is closely related to the enthalpy of adsorption. Thus, studying the behavior of the enthalpy of adsorption as a function of loading is fundamental to understanding separation processes. Unfortunately, close to saturation, the enthalpy of adsorption is hard to measure experimentally and hard to compute in simulations. In simulations, the enthalpy of adsorption is usually obtained from energy/particle fluctuations in the grand-canonical ensemble, but this methodology is hampered by vanishing insertions/deletions at high loading. To investigate the fundamental behavior of the enthalpy and entropy of adsorption at high loading, we develop a simplistic model of adsorption in a channel and show that at saturation the enthalpy of adsorption diverges to large positive values due to repulsive intermolecular interactions. However, there are many systems that can avoid repulsive intermolecular interactions and hence do not show this drastic increase in enthalpy of adsorption close to saturation. We find that the conventional grand-canonical Monte Carlo method is incapable of determining the enthalpy of adsorption from energy/particle fluctuations at high loading. Here, we show that by using the continuous fractional component Monte Carlo, the enthalpy of adsorption close to saturation conditions can be reliably obtained from the energy/particle fluctuations in the grand-canonical ensemble. The best method to study properties at saturation is the NVT energy (local-) slope methodology.

  16. The Optimal Use of Entropy and Enthalpy

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 9. The Optimal Use of Entropy and Enthalpy. M S Ananth R Ravi. General Article Volume 6 Issue 9 ... Author Affiliations. M S Ananth1 R Ravi1. Department of Chemical Engineering, Indian Institute of Technology, Chennai 600 036, India.

  17. Modular enthalpy probe and gas analyzer for thermal plasma measurements

    Science.gov (United States)

    Swank, W. D.; Fincke, J. R.; Haggard, D. C.

    1993-01-01

    The enthalpy or calorimetric probe is a water-cooled stagnation/sampling probe for studying the temperature, velocity, and composition of hot-gas flow fields. In order to derive the thermodynamic properties of complex flow fields such as plasma arc jets or high-velocity oxygen fuel jets, the specie concentration must be known accurately. To this end a differentially pumped quadrapole mass spectrometer has been integrated with a fully automated enthalpy probe system. An inexpensive modular probe is described along with the system and its theory of operation. Calibration and error are also discussed. Typical results are presented for the system operating in an argon/helium plasma arc jet in atmospheric pressure air. The maximum temperature measured is 13434 K on the center line of the jet, 5 mm from the exit, with a corresponding velocity of 1295 m/s. The utility in integrating the mass spectrometer to the enthalpy probe system is not only an accurate measurement of the gas mixture components for obtaining the correct property information, but also valuable information can be obtained about demixing diffusion and chemical reaction taking place in the plasma plume. The relative amount of argon to helium is shown to deviate from the nominal mixture by as much as 40% at the center of the plume.

  18. Formation enthalpies by mixing GGA and GGA + U calculations

    Science.gov (United States)

    Jain, Anubhav; Hautier, Geoffroy; Ong, Shyue Ping; Moore, Charles J.; Fischer, Christopher C.; Persson, Kristin A.; Ceder, Gerbrand

    2011-07-01

    Standard approximations to the density functional theory exchange-correlation functional have been extraordinary successful, but calculating formation enthalpies of reactions involving compounds with both localized and delocalized electronic states remains challenging. In this work we examine the shortcomings of the generalized gradient approximation (GGA) and GGA+U in accurately characterizing such difficult reactions. We then outline a methodology that mixes GGA and GGA+U total energies (using known binary formation data for calibration) to more accurately predict formation enthalpies. We demonstrate that for a test set of 49 ternary oxides, our methodology can reduce the mean absolute relative error in calculated formation enthalpies from approximately 7.7-21% in GGA+U to under 2%. As another example we show that neither GGA nor GGA+U alone accurately reproduces the Fe-P-O phase diagram; however, our mixed methodology successfully predicts all known phases as stable by naturally stitching together GGA and GGA+U results. As a final example we demonstrate how our technique can be applied to the calculation of the Li-conversion voltage of LiFeF3. Our results indicate that mixing energies of several functionals represents one avenue to improve the accuracy of total energy computations without affecting the cost of calculation.

  19. Enthalpy of formation of natural amesite

    Science.gov (United States)

    Ogorodova, L. P.; Mel'chakova, L. V.; Vigasina, M. F.; Ksenofontov, D. A.; Bryzgalov, I. A.

    2015-02-01

    Natural amesite from the Saranovsk deposit of chromites (Perm krai, Russia) and characterized using a number of contemporary physicochemical methods is studied thermochemically on a Setaram high-temperature heat-flux Tian-Calvet microcalorimeter (France). The enthalpy of formation from the simple substances Δf H°(298.15 K) = -4518.3 ± 9.2 kJ/mol for Mg2Al[SiAlO5](OH)4 amesite is determined via melt dissolution calorimetry.

  20. Enthalpy Calculation for Pressurized Oxy- coal Combustion

    OpenAIRE

    Weihong Wu; Jingli Huang

    2012-01-01

    Oxy-fuel combustion is recognizing one of the most promising available technologies that zero emission accomplishment may be in the offing. With coal burned under the pressure of 6MPa and oxygen-enriched conditions, the high temperature and high pressure gaseous combustion product is composed of 95% CO2 and water-vapor, with the rest of O2, N2 and so on. However, once lauded as classic approach of resolving fuel gas enthalpy calculation pertaining to ideal gas at atmospheric pressure was rest...

  1. Partial molar enthalpies and reaction enthalpies from equilibrium molecular dynamics simulation

    NARCIS (Netherlands)

    Schnell, S.K.; Skorpa, R.; Bedeaux, D.; Kjelstrup, S.H.; Vlugt, T.J.H.; Simon, J.M.

    2014-01-01

    We present a new molecular simulation technique for determining partial molar enthalpies in mixtures of gases and liquids from single simulations, without relying on particle insertions, deletions, or identity changes. The method can also be applied to systems with chemical reactions. We demonstrate

  2. The relationship between discharge capacity of LaNi{sub 5} type hydrogen storage alloys and formation enthalpy

    Energy Technology Data Exchange (ETDEWEB)

    Ma Xiaobo; Wei Xuedong; Dong Hui [State Key Laboratory of Mechanical Behavior of Materials, School of Material Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Liu Yongning, E-mail: ynliu@mail.xjtu.edu.c [State Key Laboratory of Mechanical Behavior of Materials, School of Material Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)

    2010-02-04

    The formation enthalpy of LaNi{sub 5} type hydrogen storage alloys has been calculated using a semi-empirical formula that takes into account the electronegativities, the atomic size, and the electron concentration of each constituent element in the alloys. Through our calculations, it was found that the formation enthalpy of the alloys is directly related to the discharge capacities of the alloys. When the absolute value of formation enthalpy decreases, the discharge capacity increases. The result provides a valuable reference for alloy design.

  3. Measurement of the aerothermodynamic state in a high enthalpy plasma wind-tunnel flow

    Science.gov (United States)

    Hermann, Tobias; Löhle, Stefan; Zander, Fabian; Fasoulas, Stefanos

    2017-11-01

    This paper presents spatially resolved measurements of absolute particle densities of N2, N2+, N, O, N+ , O+ , e- and excitation temperatures of electronic, rotational and vibrational modes of an air plasma free stream. All results are based on optical emission spectroscopy data. The measured parameters are combined to determine the local mass-specific enthalpy of the free stream. The analysis of the radiative transport, relative and absolute intensities, and spectral shape is used to determine various thermochemical parameters. The model uncertainty of each analysis method is assessed. The plasma flow is shown to be close to equilibrium. The strongest deviations from equilibrium occur for N, N+ and N2+ number densities in the free stream. Additional measurements of the local mass-specific enthalpy are conducted using a mass injection probe as well as a heat flux and total pressure probe. The agreement between all methods of enthalpy determination is good.

  4. An Implicit Mixed Enthalpy-Temperature Method For Phase-Change Problems

    DEFF Research Database (Denmark)

    Krabbenhoft, Kristian; Damkilde, Lars; Nazem, M.

    2007-01-01

    Abstract A finite element procedure for phase-change problems is presented. Enthalpy and temperature are interpolated separately and subsequently linked via the appropriate relation in the nodes of the mesh during the solution phase. A novel technique is here used where, depending...... on the characteristics of the problem, either temperature or enthalpy may be considered as primary variable. The resulting algorithm is both efficient and robust and is further easy to implement and generalize to arbitrary finite elements. The capabilities of the method are illustrated by the solution both isothermal...... and nonisothermal phase-change problems....

  5. Calculation of partial enthalpies in argon-krypton mixtures by NPT molecular dynamics

    NARCIS (Netherlands)

    Sindzingre, P.; Massobrio, C.; Ciccotti, G.; Frenkel, D.

    1989-01-01

    In an earlier paper, we have indicated how, by using a particle-insertion technique, partial molar enthalpies and related quantities can be evaluated from simulations on a single state point. In the present paper we apply this method to a Lennard-Jones argon-krypton mixture. For this particular

  6. Molecular rigidity and enthalpy-entropy compensation in DNA melting.

    Science.gov (United States)

    Vargas-Lara, Fernando; Starr, Francis W; Douglas, Jack F

    2017-10-23

    Enthalpy-entropy compensation (EEC) is observed in diverse molecular binding processes of importance to living systems and manufacturing applications, but this widely occurring phenomenon is not sufficiently understood from a molecular physics standpoint. To gain insight into this fundamental problem, we focus on the melting of double-stranded DNA (dsDNA) since measurements exhibiting EEC are extensive for nucleic acid complexes and existing coarse-grained models of DNA allow us to explore the influence of changes in molecular parameters on the energetic parameters by using molecular dynamics simulations. Previous experimental and computational studies have indicated a correlation between EEC and changes in molecular rigidity in certain binding-unbinding processes, and, correspondingly, we estimate measures of DNA molecular rigidity under a wide range of conditions, along with resultant changes in the enthalpy and entropy of binding. In particular, we consider variations in dsDNA rigidity that arise from changes of intrinsic molecular rigidity such as varying the associative interaction strength between the DNA bases, the length of the DNA chains, and the bending stiffness of the individual DNA chains. We also consider extrinsic changes of molecular rigidity arising from the addition of polymer additives and geometrical confinement of DNA between parallel plates. All our computations confirm EEC and indicate that this phenomenon is indeed highly correlated with changes in molecular rigidity. However, two distinct patterns relating to how DNA rigidity influences the entropy of association emerge from our analysis. Increasing the intrinsic DNA rigidity increases the entropy of binding, but increases in molecular rigidity from external constraints decreases the entropy of binding. EEC arises in numerous synthetic and biological binding processes and we suggest that changes in molecular rigidity might provide a common origin of this ubiquitous phenomenon in the mutual

  7. Vapor pressures and enthalpies of vaporization of azides

    Energy Technology Data Exchange (ETDEWEB)

    Verevkin, Sergey P., E-mail: sergey.verevkin@uni-rostock.de [Department of Physical Chemistry, University of Rostock, Dr-Lorenz-Weg 1, D-18059 Rostock (Germany); Emel' yanenko, Vladimir N. [Department of Physical Chemistry, University of Rostock, Dr-Lorenz-Weg 1, D-18059 Rostock (Germany); Algarra, Manuel [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Manuel Lopez-Romero, J. [Department of Organic Chemistry, University of Malaga. Campus de Teatinos s/n, 29071 Malaga (Spain); Aguiar, Fabio; Enrique Rodriguez-Borges, J.; Esteves da Silva, Joaquim C.G. [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

    2011-11-15

    Highlights: > We prepared and measured vapor pressures and vaporization enthalpies of 7 azides. > We examined consistency of new and available in the literature data. > Data for geminal azides and azido-alkanes selected for thermochemical calculations. - Abstract: Vapor pressures of some azides have been determined by the transpiration method. The molar enthalpies of vaporization {Delta}{sub l}{sup g}H{sub m} of these compounds were derived from the temperature dependencies of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of similarly structured compounds.

  8. Coupling geophysical investigation with hydrothermal modeling to constrain the enthalpy classification of a potential geothermal resource.

    Science.gov (United States)

    White, Jeremy T.; Karakhanian, Arkadi; Connor, Chuck; Connor, Laura; Hughes, Joseph D.; Malservisi, Rocco; Wetmore, Paul

    2015-01-01

    An appreciable challenge in volcanology and geothermal resource development is to understand the relationships between volcanic systems and low-enthalpy geothermal resources. The enthalpy of an undeveloped geothermal resource in the Karckar region of Armenia is investigated by coupling geophysical and hydrothermal modeling. The results of 3-dimensional inversion of gravity data provide key inputs into a hydrothermal circulation model of the system and associated hot springs, which is used to evaluate possible geothermal system configurations. Hydraulic and thermal properties are specified using maximum a priori estimates. Limited constraints provided by temperature data collected from an existing down-gradient borehole indicate that the geothermal system can most likely be classified as low-enthalpy and liquid dominated. We find the heat source for the system is likely cooling quartz monzonite intrusions in the shallow subsurface and that meteoric recharge in the pull-apart basin circulates to depth, rises along basin-bounding faults and discharges at the hot springs. While other combinations of subsurface properties and geothermal system configurations may fit the temperature distribution equally well, we demonstrate that the low-enthalpy system is reasonably explained based largely on interpretation of surface geophysical data and relatively simple models.

  9. Hypersonic aerothermodynamic and scramjet research using high enthalpy shock tunnel

    Science.gov (United States)

    Itoh, K.; Ueda, S.; Tanno, H.; Komuro, T.; Sato, K.

    A high enthalpy shock tunnel is a potential facility for gaining knowledge to develop modern aerothermodynamic and propulsion technologies. The largest high enthalpy shock tunnel HIEST was built at NAL Kakuda in 1997, aiming for aerothermodynamic tests of Japan's space vehicle HOPE and scramjet propulsion systems. Selected topics from the experimental studies carried out using HIEST so far, such as the nonequilibrium aerodynamics of HOPE, the surface catalytic effect on aerodynamic heating and scramjet performance are described.

  10. Enthalpy-entropy compensation: the role of solvation.

    Science.gov (United States)

    Dragan, Anatoliy I; Read, Christopher M; Crane-Robinson, Colyn

    2017-05-01

    Structural modifications to interacting systems frequently lead to changes in both the enthalpy (heat) and entropy of the process that compensate each other, so that the Gibbs free energy is little changed: a major barrier to the development of lead compounds in drug discovery. The conventional explanation for such enthalpy-entropy compensation (EEC) is that tighter contacts lead to a more negative enthalpy but increased molecular constraints, i.e., a compensating conformational entropy reduction. Changes in solvation can also contribute to EEC but this contribution is infrequently discussed. We review long-established and recent cases of EEC and conclude that the large fluctuations in enthalpy and entropy observed are too great to be a result of only conformational changes and must result, to a considerable degree, from variations in the amounts of water immobilized or released on forming complexes. Two systems exhibiting EEC show a correlation between calorimetric entropies and local mobilities, interpreted to mean conformational control of the binding entropy/free energy. However, a substantial contribution from solvation gives the same effect, as a consequence of a structural link between the amount of bound water and the protein flexibility. Only by assuming substantial changes in solvation-an intrinsically compensatory process-can a more complete understanding of EEC be obtained. Faced with such large, and compensating, changes in the enthalpies and entropies of binding, the best approach to engineering elevated affinities must be through the addition of ionic links, as they generate increased entropy without affecting the enthalpy.

  11. Experimental formation enthalpies for intermetallic phases and other inorganic compounds

    Science.gov (United States)

    Kim, George; Meschel, S. V.; Nash, Philip; Chen, Wei

    2017-10-01

    The standard enthalpy of formation of a compound is the energy associated with the reaction to form the compound from its component elements. The standard enthalpy of formation is a fundamental thermodynamic property that determines its phase stability, which can be coupled with other thermodynamic data to calculate phase diagrams. Calorimetry provides the only direct method by which the standard enthalpy of formation is experimentally measured. However, the measurement is often a time and energy intensive process. We present a dataset of enthalpies of formation measured by high-temperature calorimetry. The phases measured in this dataset include intermetallic compounds with transition metal and rare-earth elements, metal borides, metal carbides, and metallic silicides. These measurements were collected from over 50 years of calorimetric experiments. The dataset contains 1,276 entries on experimental enthalpy of formation values and structural information. Most of the entries are for binary compounds but ternary and quaternary compounds are being added as they become available. The dataset also contains predictions of enthalpy of formation from first-principles calculations for comparison.

  12. Determinations of enthalpy and partial molar enthalpy in the alloys Bi–Cd–Ga–In–Zn, Bi–Cd–Ga–Zn and Au–Cu–Sn

    Energy Technology Data Exchange (ETDEWEB)

    Arslan, Hüseyin, E-mail: hseyin_arslan@yahoo.com

    2015-03-01

    In the present study, the relations of thermodynamic associated with Chou's general solution model (GSM), the models of Muggianu and Toop have been used in order to calculate the mixing enthalpy and partial molar mixing enthalpy of mixing of Bi–Cd–Ga–In–Zn, Bi–Cd–Ga–Zn with equimolar section at a temperature of 730 K and Au–Cu–Sn with the section x{sub Au}/x{sub Cu} = 1/1 on the entire molar fraction range as a function of alloy composition at a temperature of 900 K. Some negativities are reported in the selected alloys mentioned above, particularly at high temperatures for the human health as well as difficulties in experimental measurement and high costs. Moreover, aim of us is to close the current article gap seen in the literature. In order to close the current gap seen in the literature, the article on the thermodynamic properties of the Bi–Cd–Ga–In–Zn alloys are presented in this study. - Highlights: • Thermodynamic properties of alloys in the study in given conditions were treated. • The activity of Bi seen in all models shows greatly positive deviation from ideality. • The enthalpy of Sn shows small negative values in x{sub Au}/x{sub Cu} = 1 at 900 K. • The activity of Sn shows negative deviation from ideality in the same conditions.

  13. Free Energy, Enthalpy and Entropy from Implicit Solvent End-Point Simulations

    Directory of Open Access Journals (Sweden)

    Federico Fogolari

    2018-02-01

    Full Text Available Free energy is the key quantity to describe the thermodynamics of biological systems. In this perspective we consider the calculation of free energy, enthalpy and entropy from end-point molecular dynamics simulations. Since the enthalpy may be calculated as the ensemble average over equilibrated simulation snapshots the difficulties related to free energy calculation are ultimately related to the calculation of the entropy of the system and in particular of the solvent entropy. In the last two decades implicit solvent models have been used to circumvent the problem and to take into account solvent entropy implicitly in the solvation terms. More recently outstanding advancement in both implicit solvent models and in entropy calculations are making the goal of free energy estimation from end-point simulations more feasible than ever before. We review briefly the basic theory and discuss the advancements in light of practical applications.

  14. Formation enthalpies for transition metal alloys using machine learning

    Science.gov (United States)

    Ubaru, Shashanka; Miedlar, Agnieszka; Saad, Yousef; Chelikowsky, James R.

    2017-06-01

    The enthalpy of formation is an important thermodynamic property. Developing fast and accurate methods for its prediction is of practical interest in a variety of applications. Material informatics techniques based on machine learning have recently been introduced in the literature as an inexpensive means of exploiting materials data, and can be used to examine a variety of thermodynamics properties. We investigate the use of such machine learning tools for predicting the formation enthalpies of binary intermetallic compounds that contain at least one transition metal. We consider certain easily available properties of the constituting elements complemented by some basic properties of the compounds, to predict the formation enthalpies. We show how choosing these properties (input features) based on a literature study (using prior physics knowledge) seems to outperform machine learning based feature selection methods such as sensitivity analysis and LASSO (least absolute shrinkage and selection operator) based methods. A nonlinear kernel based support vector regression method is employed to perform the predictions. The predictive ability of our model is illustrated via several experiments on a dataset containing 648 binary alloys. We train and validate the model using the formation enthalpies calculated using a model by Miedema, which is a popular semiempirical model used for the prediction of formation enthalpies of metal alloys.

  15. Prediction of solvation enthalpy of gaseous organic compounds in propanol

    Science.gov (United States)

    Golmohammadi, Hassan; Dashtbozorgi, Zahra

    2016-09-01

    The purpose of this paper is to present a novel way for developing quantitative structure-property relationship (QSPR) models to predict the gas-to-propanol solvation enthalpy (Δ H solv) of 95 organic compounds. Different kinds of descriptors were calculated for each compound using the Dragon software package. The variable selection technique of replacement method (RM) was employed to select the optimal subset of solute descriptors. Our investigation reveals that the dependence of physical chemistry properties of solution on solvation enthalpy is nonlinear and that the RM method is unable to model the solvation enthalpy accurately. The results established that the calculated Δ H solv values by SVM were in good agreement with the experimental ones, and the performances of the SVM models were superior to those obtained by RM model.

  16. Accurate Computed Enthalpies of Spin Crossover in Iron and Cobalt Complexes

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta; Cirera, J

    2009-01-01

    Despite their importance in many chemical processes, the relative energies of spin states of transition metal complexes have so far been haunted by large computational errors. By the use of six functionals, B3LYP, BP86, TPSS, TPSSh, M06L, and M06L, this work studies nine complexes (seven with iron...... and two with cobalt) for which experimental enthalpies of spin crossover are available. It is shown that such enthalpies can be used as quantitative benchmarks of a functional's ability to balance electron correlation in both the involved states. TPSSh achieves an unprecedented mean absolute error...... effects of first-row transition metal systems. Furthermore, it is shown that given an experimental structure of an iron complex, TPSSh can predict the electronic state corresponding to that experimental structure. We recommend this functional as current state-of-the-art for studying spin crossover...

  17. Enthalpy of mixing of liquid Al-Cu-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Witusiewicz, V.T.; Arpshofen, I.; Seifert, H.-J.; Aldinger, F. [Max-Planck Inst. fur Metallforschung, Stuttgart (Germany). Inst. fur Nichtmetallische Anorganische Mater.

    2000-02-02

    The partial and the integral enthalpies of mixing of liquid Al-Cu-Si alloys have been measured by high temperature calorimetry at 1575{+-}3 K. Results for three sections with constant concentration ratios of Al and Si are given in tabular form. (orig.)

  18. Modified enthalpy method for the simulation of melting and ...

    Indian Academy of Sciences (India)

    face obtained is compared satisfactorily with the experimental results available in literature. Keywords. Melting; enthalpy method; wavy interface; mushy zone constant. 1. Introduction. The study of melting and solidification offers insights in the design of casting, welding, latent thermal energy storage systems, etc., and in the ...

  19. Enthalpy and void distributions in subchannels of PHWR fuel bundles

    Energy Technology Data Exchange (ETDEWEB)

    Park, J. W.; Choi, H.; Rhee, B. W. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1998-12-31

    Two different types of the CANDU fuel bundles have been modeled for the ASSERT-IV code subchannel analysis. From calculated values of mixture enthalpy and void fraction distribution in the fuel bundles, it is found that net buoyancy effect is pronounced in the central region of the DUPIC fuel bundle when compared with the standard CANDU fuel bundle. It is also found that the central region of the DUPIC fuel bundle can be cooled more efficiently than that of the standard fuel bundle. From the calculated mixture enthalpy distribution at the exit of the fuel channel, it is found that the mixture enthalpy and void fraction can be highest in the peripheral region of the DUPIC fuel bundle. On the other hand, the enthalpy and the void fraction were found to be highest in the central region of the standard CANDU fuel bundle at the exit of the fuel channel. This study shows that the subchannel analysis is very useful in assessing thermal behavior of the fuel bundle that could be used in CANDU reactors. 10 refs., 4 figs., 2 tabs. (Author)

  20. Influence of Countercation Hydration Enthalpies on the Formation of Molecular Complexes: A Thorium-Nitrate Example.

    Science.gov (United States)

    Jin, Geng Bang; Lin, Jian; Estes, Shanna L; Skanthakumar, S; Soderholm, L

    2017-12-13

    The influence of countercations (A n+ ) in directing the composition of monomeric metal-ligand (ML) complexes that precipitate from solution are often overlooked despite the wide usage of A n+ in materials synthesis. Herein, we describe a correlation between the composition of ML complexes and A + hydration enthalpies found for two related series of thorium (Th)-nitrate molecular compounds obtained by evaporating acidic aqueous Th-nitrate solutions in the presence of A + counterions. Analyses of their chemical composition and solid-state structures demonstrate that A + not only affects the overall solid-state packing of the Th-nitrato complexes but also influences the composition of the Th-nitrato monomeric anions themselves. Trends in composition and structure are found to correlate with A + hydration enthalpies, such that the A + with smaller hydration enthalpies associate with less hydrated and more anionic Th-nitrato complexes. This perspective, broader than the general assumption of size and charge as the dominant influence of A n+ , opens a new avenue for the design and synthesis of targeted metal-ligand complexes.

  1. Enthalpy measurement of coal-derived liquids. Technical progress report, November 1982-January 1983

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1983-02-22

    The objective of this research is to measure the enthalpy for representative coal-derived liquids and model compounds over the pressure and temperature regions most likely to be encountered in both liquefaction and processing systems, and to prepare from the data an enthalpy correlation suitable for process design calculations. The correlational effort this past quarter on the enthalpy of coal-derived syncrudes and model compounds has emphasized the experimental determination of a correlating factor for association in coal liquids. As in previous work, the degree of association is to be related to cryoscopic molecular weight determinations on the coal liquids. To this end, work on and an evaluationof a cryoscopic molecular weight apparatus was completed this quarter. Molecular weights of coal liquids determined by the standard Beckman freezing point depression apparatus were consistently low (5 to 10%). After modifications of the apparatus, it was tested with the following compounds: hexane, dodecane, m-xylene and naphthalene. Benzene was the solvent used. However, the molecular weight measurements were again consistently lower than the true values, and in many cases the experimental error was greater than that of the Beckman apparatus.

  2. The Optimal Use of Entropy and Enthalpy

    Indian Academy of Sciences (India)

    In order to apply these results to engineering systems we then describe the model for the Gibbs free energy of an ideal mixture. The calculation of the work of separation and the relative importance of enthalpic and entropic contributions are then illustrated using examples. The major component of the cost of many chemicals ...

  3. Low enthalpy geothermal energy: borehole heat exchangers (BHE). Geological and geothermal supervision during active construction in support of the energy certification of buildings - ESBE certification plan

    OpenAIRE

    Lorenzo Cadrobbi; Fioroni Daniele; Alessandro Bozzoli

    2012-01-01

    This article draws on the experience matured while working with low-enthalpy geothermic installations both in the design and executive phase as well as ongoing monitoring, within the scope of energy conservation as it relates to building and construction. The goal is to illustrate the feasibility of adopting the ESBE certification protocol (Certification of Energy Efficient Low-Enthalpy Probes) aimed at optimizing the harnessing of local geothermic resources to satisfy the energy requirements...

  4. Enthalpy restoration in geothermal energy processing system

    Science.gov (United States)

    Matthews, Hugh B.

    1983-01-01

    A geothermal deep well energy extraction system is provided of the general type in which solute-bearing hot water is pumped to the earth's surface from a relatively low temperature geothermal source by transferring thermal energy from the hot water to a working fluid for driving a primary turbine-motor and a primary electrical generator at the earth's surface. The superheated expanded exhaust from the primary turbine motor is conducted to a bubble tank where it bubbles through a layer of sub-cooled working fluid that has been condensed. The superheat and latent heat from the expanded exhaust of the turbine transfers thermal energy to the sub-cooled condensate. The desuperheated exhaust is then conducted to the condenser where it is condensed and sub-cooled, whereupon it is conducted back to the bubble tank via a barometric storage tank. The novel condensing process of this invention makes it possible to exploit geothermal sources which might otherwise be non-exploitable.

  5. Enthalpies of Vaporization of Organic and Organometallic Compounds, 1880–2002

    National Research Council Canada - National Science Library

    Chickos, James S; Acree, William E

    2003-01-01

    A compendium of vaporization enthalpies published within the period 1910–2002 is reported. A brief review of temperature adjustments of vaporization enthalpies from temperature of measurement to the standard reference temperature...

  6. Estimating the melting point, entropy of fusion, and enthalpy of ...

    Science.gov (United States)

    The entropies of fusion, enthalies of fusion, and melting points of organic compounds can be estimated through three models developed using the SPARC (SPARC Performs Automated Reasoning in Chemistry) platform. The entropy of fusion is modeled through a combination of interaction terms and physical descriptors. The enthalpy of fusion is modeled as a function of the entropy of fusion, boiling point, and fexibility of the molecule. The melting point model is the enthlapy of fusion divided by the entropy of fusion. These models were developed in part to improve SPARC's vapor pressure and solubility models. These models have been tested on 904 unique compounds. The entropy model has a RMS of 12.5 J mol-1K-1. The enthalpy model has a RMS of 4.87 kJ mol-1. The melting point model has a RMS of 54.4°C. Published in the journal, SAR and QSAR in Environmental Research

  7. Corollary from the Exact Expression for Enthalpy of Vaporization

    Directory of Open Access Journals (Sweden)

    A. A. Sobko

    2011-01-01

    Full Text Available A problem on determining effective volumes for atoms and molecules becomes actual due to rapidly developing nanotechnologies. In the present study an exact expression for enthalpy of vaporization is obtained, from which an exact expression is derived for effective volumes of atoms and molecules, and under certain assumptions on the form of an atom (molecule it is possible to find their linear dimensions. The accuracy is only determined by the accuracy of measurements of thermodynamic parameters at the critical point.

  8. A moderate enthalpy and a low pollution load in healthy buildings

    DEFF Research Database (Denmark)

    Fanger, Povl Ole

    1998-01-01

    For the design of healthy buildings with a comfortable indoor environment, some general recommendations are provided. New research highlights the importance of controlling the enthalpy of indoor air at a moderate level, i.e., by controlling air temperature and relative humidity at a rather low...... level, still compatible with thermal comfort. A decrement of air temperature or humidity improves the perceived air quality and may decrease the required ventilation rate. A moderate air temperature and humidity plus individual control by radiation and conduction is recommended in order to decrease...

  9. Enthalpy model for heating, melting, and vaporization in laser ablation

    Directory of Open Access Journals (Sweden)

    Vasilios Alexiades

    2010-09-01

    Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.

  10. Absolute ion hydration enthalpies from absolute hardness and some VBT relationships

    Science.gov (United States)

    Kaya, Savaş; Fernandes de Farias, Robson

    2018-01-01

    In the present work, absolute hydration enthalpies are calculated from ion absolute hardness for a series of +1 and -1 ions. The calculated values are compared with those previously reported (Housecroft, 2017) [2] and relationships between Vm-1/3 and absolute hardness are stablished. The following empirical equations have been derived, for cations and anions, respectively: ΔhydHo = -(9.645 η+ + 245.930) and ΔhydHo = -(64.601 η- + 12.321). In such equations, η+ and η- are the absolute hardness. It is shown that for d block monocations (Cu+, Ag+ and Au+), hydration enthalpy is closely related with Clementi effective nuclear charge by the equation: ΔhydHo = -(9.645 η+ + 245.930) (Zeff/(n - 1)), where n is the main quantum number. Furthermore, is shown that a typical VBT parameter (Vm-1/3) is related with η+ and η- values and so, with the energies of the frontier orbitals, that is, is stablished a direct relationship between a structural parameter available by X-ray data and the energy of atomic/molecular orbitals.

  11. Kinetics and enthalpy of crystallization of uric acid dihydrate

    Energy Technology Data Exchange (ETDEWEB)

    Sádovská, Galina, E-mail: galina.sadovska@upce.cz; Honcová, Pavla; Sádovský, Zdeněk

    2013-08-20

    Highlights: • The kinetic constant and growth order of crystallization of uric acid dihydrate was calculated. • The equation describing first-order crystal growth was derived. • The enthalpy of crystallization of uric acid dihydrate was determined. - Abstract: The kinetics of crystallization of uric acid dihydrate in aqueous solution with a constant ionic strength 0.3 mol dm{sup −3} NaCl and at thermodynamic and physiological temperature (25 and 37 °C) was studied using isoperibolic reaction twin calorimeter. The enthalpy of crystallization Δ{sub cr}H = −47.3 ± 0.9 and −46.2 ± 1.4 kJ mol{sup −1}and kinetic constant k{sub g} = 2.0 × 10{sup −8} and 9.6 × 10{sup −8} m{sup 4} s{sup −1} mol{sup −1} were determined at 25 and 37 °C, respectively.

  12. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, October-December 1985

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1986-01-31

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the sixth quarter, preliminary enthalpy measurements for the 1/3:2/3, 1/2:1/2, 2/3:1/3 m-cresol tetralin binary mixtures have been completed and are included in a section at the end of this report. Vapor liquid equilibria measurements for the m-cresol/tetralin system are in progress for four isotherms. Tetralin vapor pressures are reported in this report from both the VLE apparatus and the calorimeter. In addition, ongoing research into the modeling of polar systems has led to an approach for modifying the Soave equation of state. This equation of state introduces a polar parameter which appears to be related to the expected strength of polar interactions for different compounds. The appendix contains the paper on this work titled ''Approach for extending Van de Waals equations of state for polar, hydrogen bonding fluids applied to the Soave equation of state''. This article has been processed separately for inclusion in the Energy Data Base.

  13. Accounting for apparent deviations between calorimetric and van't Hoff enthalpies.

    Science.gov (United States)

    Kantonen, Samuel A; Henriksen, Niel M; Gilson, Michael K

    2017-12-05

    In theory, binding enthalpies directly obtained from calorimetry (such as ITC) and the temperature dependence of the binding free energy (van't Hoff method) should agree. However, previous studies have often found them to be discrepant. Experimental binding enthalpies (both calorimetric and van't Hoff) are obtained for two host-guest pairs using ITC, and the discrepancy between the two enthalpies is examined. Modeling of artificial ITC data is also used to examine how different sources of error propagate to both types of binding enthalpies. For the host-guest pairs examined here, good agreement, to within about 0.4kcal/mol, is obtained between the two enthalpies. Additionally, using artificial data, we find that different sources of error propagate to either enthalpy uniquely, with concentration error and heat error propagating primarily to calorimetric and van't Hoff enthalpies, respectively. With modern calorimeters, good agreement between van't Hoff and calorimetric enthalpies should be achievable, barring issues due to non-ideality or unanticipated measurement pathologies. Indeed, disagreement between the two can serve as a flag for error-prone datasets. A review of the underlying theory supports the expectation that these two quantities should be in agreement. We address and arguably resolve long-standing questions regarding the relationship between calorimetric and van't Hoff enthalpies. In addition, we show that comparison of these two quantities can be used as an internal consistency check of a calorimetry study. Copyright © 2017. Published by Elsevier B.V.

  14. Measurement and correlation of the enthalpy of coal-derived liquids

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, R.; Kidnay, A.J.; Yesavage, V.F.

    1982-03-01

    An apparatus termed the Freon 11 reference fluid boil-off calorimeter described in previous publication is illustrated, and enthalpy data obtained with the calorimeter for numerous coal-derived liquid samples are tabulated. Enthalpy data for certain model compounds representative of the coal-derived liquids are presented for comparison. Association of heteroatomic compounds in coal-derived liquids appeared to cause positive errors in the enthalpy data. A method of determining the degree of association from the slope of the molecular weight versus the concentration curve appears to be applicable to the correction of the enthalpy data. 17 refrerences. (BLM)

  15. Application of enthalpy model for floating zone silicon crystal growth

    Science.gov (United States)

    Krauze, A.; Bergfelds, K.; Virbulis, J.

    2017-09-01

    A 2D simplified crystal growth model based on the enthalpy method and coupled with a low-frequency harmonic electromagnetic model is developed to simulate the silicon crystal growth near the external triple point (ETP) and crystal melting on the open melting front of a polycrystalline feed rod in FZ crystal growth systems. Simulations of the crystal growth near the ETP show significant influence of the inhomogeneities of the EM power distribution on the crystal growth rate for a 4 in floating zone (FZ) system. The generated growth rate fluctuations are shown to be larger in the system with higher crystal pull rate. Simulations of crystal melting on the open melting front of the polycrystalline rod show the development of melt-filled grooves at the open melting front surface. The distance between the grooves is shown to grow with the increase of the skin-layer depth in the solid material.

  16. Changes of enthalpy slope in subcooled flow boiling

    Energy Technology Data Exchange (ETDEWEB)

    Collado, Francisco J.; Monne, Carlos [Universidad de Zaragoza-CPS, Departamento de Ingenieria Mecanica-Motores Termicos, Zaragoza (Spain); Pascau, Antonio [Universidad de Zaragoza-CPS, Departamento de Ciencia de los Materiales y Fluidos-Mecanica de Fluidos, Zaragoza (Spain)

    2006-03-01

    Void fraction data in subcooled flow boiling of water at low pressure measured by General Electric in the 1960s are analyzed following the classical model of Griffith et al. (in Proceedings of ASME-AIChE heat transfer conference, 58-HT-19, 1958). In addition, a new proposal for analyzing one-dimensional steady flow boiling is used. This is based on the physical fact that if the two phases have different velocities, they cannot cover the same distance - the control volume length - in the same time. So a slight modification of the heat balance is suggested, i.e., the explicit inclusion of the vapor-liquid velocity ratio or slip ratio as scaling time factor between the phases, which is successfully checked against the data. Finally, the prediction of void fraction using correlations of the net rate of change of vapor enthalpy in the fully developed regime of subcooled flow boiling is explored. (orig.)

  17. Temperature-dependent enthalpy of oxygenation in Antarctic fish hemoglobins

    DEFF Research Database (Denmark)

    Fago, A.; Wells, R.M.G.; Weber, Roy E.

    1997-01-01

    The effect of temperature on the oxygen-binding properties of the hemoglobins of three cold-adapted Antarctic fish species, Dissostichus mawsoni, Pagothenia borchgrevinki and Trematomus, sp., has been investigated under different pH values and buffer conditions. A clear non linear van't Hoff plot...... oxygen binding. The degree of the temperature dependence of the heat of oxygenation observed in these hemoglobins seems to reflect the differences in their allosteric effects rather than a specific molecular adaptation to low temperatures. Moreover, this study indicates that the disagreement between...... (logP(50) vs 1/T) of D. mawsoni hemoglobin indicates that the enthalpy of oxygenation (slope of the plot) is temperature dependent and that at high temperatures oxygen-binding becomes less exothermic. Nearly linear relationships were found in the hemoglobins of the other two species. The data were...

  18. Standard molar enthalpies of formation of hydroxy-, chlor-, and bromapatite

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, Fernando J.A.L. [Centro de Quimica Estrutural, Complexo Interdisciplinar, Instituto Superior Tecnico 1049-001 Lisbon (Portugal); Minas da Piedade, Manuel E. [Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade de Lisboa, 1749-016 Lisbon (Portugal); Calado, Jorge C.G. [Centro de Quimica Estrutural, Complexo Interdisciplinar, Instituto Superior Tecnico 1049-001 Lisbon (Portugal)]. E-mail: jcalado@ist.utl.pt

    2005-10-15

    The standard (p{sup 0} =0.1MPa) molar enthalpies of formation in the crystalline state of hydroxyapatite, chlorapatite and a preliminary value for bromapatite, at T=298.15K, were determined by reaction-solution calorimetry as: {delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2},cr]=-(13399+/-11)kJ.mol{sup -1},{delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}Cl{sub 2},cr]=-(13231+/-82)kJ.mol{sup -1},and{delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}Br{sub 2},cr]=-(13063+/-81)kJ.mol{sup -1}. A critical assessment of these results and of previously published data is made. Finally, the standard molar enthalpy of formation of iodapatite is estimated as {delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}I{sub 2},cr]=-12949kJ.mol{sup -1}, from a linear correlation of {delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}X{sub 2},cr] (X=OH, F, Cl, Br) against the corresponding {delta}{sub f}H{sub m}{sup 0} [CaX{sub 2},cr].

  19. Accuracy of the DLPNO-CCSD(T) method for non-covalent bond dissociation enthalpies from coinage metal cation complexes

    KAUST Repository

    Minenkov, Yury

    2015-08-27

    The performance of the domain based local pair-natural orbital coupled-cluster (DLPNO-CCSD(T)) method has been tested to reproduce the experimental gas phase ligand dissociation enthalpy in a series of Cu+, Ag+ and Au+ complexes. For 33 Cu+ - non-covalent ligand dissociation enthalpies all-electron calculations with the same method result in MUE below 2.2 kcal/mol, although a MSE of 1.4 kcal/mol indicates systematic underestimation of the experimental values. Inclusion of scalar relativistic effects for Cu either via effective core potential (ECP) or Douglass-Kroll-Hess Hamiltonian, reduces the MUE below 1.7 kcal/mol and the MSE to -1.0 kcal/mol. For 24 Ag+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) method results in a mean unsigned error (MUE) below 2.1 kcal/mol and vanishing mean signed error (MSE). For 15 Au+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) methods provides larger MUE and MSE, equal to 3.2 and 1.7 kcal/mol, which might be related to poor precision of the experimental measurements. Overall, for the combined dataset of 72 coinage metal ion complexes DLPNO-CCSD(T) results in a MUE below 2.2 kcal/mol and an almost vanishing MSE. As for a comparison with computationally cheaper density functional theory (DFT) methods, the routinely used M06 functional results in MUE and MSE equal to 3.6 and -1.7 kca/mol. Results converge already at CC-PVTZ quality basis set, making highly accurate DLPNO-CCSD(T) estimates to be affordable for routine calculations (single-point) on large transition metal complexes of > 100 atoms.

  20. Experimental study on an innovative enthalpy recovery technology based on indirect flash evaporative cooling

    DEFF Research Database (Denmark)

    Nie, Jinzhe; Yuan, Shu; Fang, Lei

    2018-01-01

    An indirect flash evaporative cooling enthalpy recovery technology used for building ventilation was proposed based on counter flow plate heat exchanger combing with ultrasonic atomizer. The technology is aimed at enhancing enthalpy recover efficiency and preventing contaminant transfer of heat r...

  1. Effect of cure cycle on enthalpy relaxation and post shrinkage in neat epoxy and epoxy composites

    DEFF Research Database (Denmark)

    Jensen, Martin; Jakobsen, Johnny

    2016-01-01

    The effect of cure cycle on enthalpy relaxation and warpage is studied for both neat epoxy and glass/epoxy composites. An approach for determining the enthalpy relaxation in the matrix of composite materials combining modulated differential scanning calorimetry and thermogravimetry is presented...

  2. Oxygen migration enthalpy likely limits oxide precipitate dissolution during tabula rasa

    Energy Technology Data Exchange (ETDEWEB)

    Looney, E. E.; Laine, H. S.; Youssef, A.; Jensen, M. A.; LaSalvia, V.; Stradins, P.; Buonassisi, T.

    2017-09-25

    In industrial silicon solar cells, oxygen-related defects lower device efficiencies by up to 20% (rel.). In order to mitigate these defects, a high-temperature homogenization anneal called tabula rasa (TR) that has been used in the electronics industry is now proposed for use in solar-grade wafers. This work addresses the kinetics of tabula rasa by elucidating the activation energy governing oxide precipitate dissolution, which is found to be 2.6 +/- 0.5 eV. This value is consistent within uncertainty to the migration enthalpy of oxygen interstitials in silicon, implying TR to be kinetically limited by oxygen point-defect diffusion. This large activation energy is observed to limit oxygen precipitate dissolution during standard TR conditions, suggesting that more aggressive annealing conditions than conventionally used are required for complete bulk microdefect mitigation.

  3. Implications of the enthalpy flux carried by powerful quasar jets

    Science.gov (United States)

    Schwartz, Daniel; Marshall, Herman L.; Worrall, Diana; Birkinshaw, Mark; Perlman, Eric; Lovell, James; Jauncey, David; Murphy, David; Gelbord, Jonathan; Godfrey, Leith; Bicknell, Geoffrey Vincent

    2015-08-01

    We have detected 31 X-ray jets as counterparts to radio jets observed in a survey of 54 quasars (Marshall et al., 2005; 2011). With the most likely interpretation that the X-rays result from inverse Compton boosting of the cosmic microwave background photons, one can estimate the rest frame magnetic field strength, and the particle energy density via the minimum total energy assumption. To reconcile these quantities so that the same spectrum of electrons produces the GHz radio synchrotron emission and its extension to lower energy produces the X-ray, the jets must be in relativistic motion. Another approximation, for example that the bulk Lorentz factor of the jet equals the Doppler factor, is needed to estimate the Lorentz factor. That cannot becorrect for individual jets, but for the ensemble of 31 objects it results in reasonable estimates for the angle of the jet to the line of sight. We can then calculate the enthalpy flux of these jets, which are typically (5--10) x 10^46 erg/s if protons balance the electron charge, and about 5 times smaller if the jets contain only electronsand positrons. Either case represents a signficant, and sometimes dominant, portion of the Eddington luminosity of the black hole.

  4. An automated flow calorimeter for heat capacity and enthalpy measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sandarusi, J.A.; Yesavage, V.F.

    1988-11-01

    An automated flow calorimeter has been developed for the measurement of heat capacity and latent enthalpies of fluids at elevated temperatures (300-700 K) and pressure (< 30 MPa) with a design accuracy of 0.1%. The method of measurement is the traditional electrical power input flow calorimeter, utilizing a precision metering pump, which eliminates the need for flow-rate monitoring. The calorimeter cell uses a unique concentric coil design with passive metal radiation shields and active guard heaters to minimize heat leakage, eliminate the traditional constant-temperature bath, and facilitate easy component replacement. An additional feature of the instrument is a complete automation system, greatly simplifying operation of the apparatus. A novel multitasking software scheme allows a single microcomputer simultaneously to control all system temperatures, provide continuous monitoring and updates on system status, and log data. Preliminary results for liquid water mean heat capacities show the equipment to be performing satisfactorily, with data accuracies of better than /plus minus/0.3%. Minor equipment modifications and better thermometry are required to reduce systemic errors and to achieve the designed operational range.

  5. Moderate point: Balanced entropy and enthalpy contributions in soft matter

    Science.gov (United States)

    He, Baoji; Wang, Yanting

    2017-03-01

    Various soft materials share some common features, such as significant entropic effect, large fluctuations, sensitivity to thermodynamic conditions, and mesoscopic characteristic spatial and temporal scales. However, no quantitative definitions have yet been provided for soft matter, and the intrinsic mechanisms leading to their common features are unclear. In this work, from the viewpoint of statistical mechanics, we show that soft matter works in the vicinity of a specific thermodynamic state named moderate point, at which entropy and enthalpy contributions among substates along a certain order parameter are well balanced or have a minimal difference. Around the moderate point, the order parameter fluctuation, the associated response function, and the spatial correlation length maximize, which explains the large fluctuation, the sensitivity to thermodynamic conditions, and mesoscopic spatial and temporal scales of soft matter, respectively. Possible applications to switching chemical bonds or allosteric biomachines determining their best working temperatures are also briefly discussed. Project supported by the National Basic Research Program of China (Grant No. 2013CB932804) and the National Natural Science Foundation of China (Grant Nos. 11274319 and 11421063).

  6. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Cheol; Douglas, Jack F. [Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

    2015-10-14

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ∼ M{sup β}, is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from −1.8 to −2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature T{sub g} where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔH{sub a} and entropy ΔS{sub a} of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a “critical” chain length, n ≈ 17. A close examination of this phenomenon indicates that a “buckling transition” from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔS{sub a} ∝ ΔH{sub a}, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔH{sub a} and ΔS{sub a} with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  7. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains

    Science.gov (United States)

    Jeong, Cheol; Douglas, Jack F.

    2015-10-01

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ˜ Mβ, is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from -1.8 to -2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature Tg where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔHa and entropy ΔSa of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a "critical" chain length, n ≈ 17. A close examination of this phenomenon indicates that a "buckling transition" from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔSa ∝ ΔHa, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔHa and ΔSa with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  8. Heat transport modeling for the design of a low enthalpy open-loop system

    Directory of Open Access Journals (Sweden)

    Leonardo Piccinini

    2012-12-01

    Full Text Available A case study of hydrogeological characterization and heat transport modeling for the design of a low enthalpy system in the Province of Treviso (Italy is here presented. It is an open loop system that pumps and re-injects groundwater from a confined aquifer of the high Veneto plain. This type of systems is the most efficient in terms of yield, but its construction is highly conditioned by the availability of groundwater resource and by the environmental laws related to groundwater exploitation. Groundwater flow modeling with MODFLOW 2005 led to a good aquifer parameters estimation, by means of the quantitative calibration of a pumping test made on the pumping well and an observation piezometer. Then, with the heat transport modeling with SEAWAT 4 the distance between pumping well and re-injecting well has been optimized, avoiding so the thermal feedback effect. The lack of sitespecific data for dispersivity parameters has been solved through a sensitivity analysis on the main dispersivity parameters of heat transport. Finally, in order to comply with the environmental laws, a long-term forecasting simulation (duration of 20 years has been set up in order to evaluate the open loop system thermal impact on the aquifer. The obtained results put in evidence that the design of low enthalpy systems strongly needs a detailed hydrogeological characterization of the aquifer interested by the pumping and that numerical modeling is the most effective tool in support of the definition of the optimal distance between pumping and re-injecting wells in the open loop systems.

  9. Simulated solvation of organic ions: protonated methylamines in water nanodroplets. Convergence toward bulk properties and the absolute proton solvation enthalpy.

    Science.gov (United States)

    Houriez, Céline; Meot-Ner Mautner, Michael; Masella, Michel

    2014-06-12

    We applied an alternative, purely theoretical route to estimate thermodynamical properties of organic ions in bulk solution. The method performs a large ensemble of simulations of ions solvated in water nanodroplets of different sizes, using a polarizable molecular dynamics approach. We consider protonated ammonia and methylamines, and K(+) for comparison, solvated in droplets of 50-1000 water molecules. The parameters of the model are assigned from high level quantum computations of small clusters. All the bulk phase results extrapolated from droplet simulations match, and confirm independently, the relative and absolute experiment-based ion solvation energies. Without using experiment-based parameters or assumptions, the results confirm independently the solvation enthalpy of the proton, as -270.3 ± 1.1 kcal mol(-1). The calculated relative solvation enthalpies of these ions are constant from small water clusters, where only the ionic headgroups are solvated, up to bulk solution. This agrees with experimental thermochemistry, that the relative solvation energies of alkylammonium ions by only four H2O molecules reproduce the relative bulk solvation energies, although the small clusters lack major bulk solvation factors. The droplet results also show a slow convergence of ion solvation properties toward their bulk limit, and predict that the stepwise solvation enthalpies of ion/water droplets are very close to those of pure neutral water droplets already after 50 water molecules. Both the ionic and neutral clusters approach the bulk condensation energy very gradually up to 10,000 water molecules, consistent with the macroscopic liquid drop model for pure water droplets. Compared to standard computational methods based on infinite periodic systems, our protocol represents a new purely theoretical approach to investigate the solvation properties of ions. It is applicable to the solvation of organic ions, which are pivotal in environmental, industrial, and

  10. Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Feller, David [Department; Bross, David H. [Chemical; Ruscic, Branko [Chemical; Computation

    2017-08-02

    In order to address the accuracy of the long-standing experimental enthalpy of formation of gas-phase hydrazine, fully confirmed in earlier versions of Active Thermochemical Tables (ATcT), the provenance of that value is re-examined in light of new high-end calculations of the Feller-Peterson-Dixon (FPD) variety. An overly optimistic determination of the vaporization enthalpy of hydrazine, which created an unrealistically strong connection between the gas phase thermochemistry and the calorimetric results defining the thermochemistry of liquid hydrazine was identified as the probable culprit. The new enthalpy of formation of gas-phase hydrazine, based on balancing all available knowledge, was determined to be 111.57 ± 0.47 kJ/mol at 0 K (97.41 kJ/mol at 298.15 K). Close agreement was found between the ATcT (even excluding the latest theoretical result) and FPD enthalpies.

  11. Characterization of Adsorption Enthalpy of Novel Water-Stable Zeolites and Metal-Organic Frameworks

    Science.gov (United States)

    Kim, Hyunho; Cho, H. Jeremy; Narayanan, Shankar; Yang, Sungwoo; Furukawa, Hiroyasu; Schiffres, Scott; Li, Xiansen; Zhang, Yue-Biao; Jiang, Juncong; Yaghi, Omar M.; Wang, Evelyn N.

    2016-01-01

    Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes.

  12. Effect of Calcium chloride and Cadmium chloride on the enthalpy of ...

    African Journals Online (AJOL)

    user

    This paper presents the effect of two dissolved inorganic salts, CaCl2 and CdCl2 on the enthalpy of mixing of the binary 1,4 dioxane + water system has been investigated at 303.15 .... liquid mixture taken in the calorimeter to obtain the enthalpy of mixing values in Joules per mole. The performance of the calorimeter and its ...

  13. Enthalpies of dissolution of n-alkanes in a mixture of methanol-formamide

    Science.gov (United States)

    Batov, D. V.; Kustov, A. V.; Antonova, O. A.; Smirnova, N. L.

    2015-06-01

    The enthalpies of dissolution of n-hexane, n-octane, and n-decane are determined thermochemically under standard conditions to describe nonspecific solvation in a mixed solvent of methanol-formamide. Experimental data are matched with the values obtained using model calculations. It is found that the differences between the experimental and calculated enthalpies of dissolution in the region with a high content of formamide could be due to the preferable solvation of n-alkanes by methanol.

  14. Standard molar enthalpies of formation of 2-, 3- and 4-cyanobenzoic acids

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro da Silva, Manuel A.V. [Centro de Investigacao em Quimica, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)], E-mail: risilva@fc.up.pt; Amaral, Luisa M.P.F.; Boaventura, Cristina R.P.; Gomes, Jose R.B. [Centro de Investigacao em Quimica, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)

    2008-08-15

    The standard (p{sup 0} = 0.1 MPa) molar enthalpies of formation of 2-, 3- and 4-cyanobenzoic acids were derived from their standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpies of sublimation of 2- and 3-cyanobenzoic acids. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the condensed phase and standard molar enthalpies for phase transition. The results obtained are -(150.7 {+-} 2.0) kJ . mol{sup -1}, -(153.6 {+-} 1.7) kJ . mol{sup -1} and -(157.1 {+-} 1.4) kJ . mol{sup -1} for 2-cyano, 3-cyano and 4-cyanobenzoic acids, respectively. Standard molar enthalpies of formation were also estimated by employing two different methodologies: one based on the Cox scheme and the other one based on several different computational approaches. The calculated values show a good agreement with the experimental values obtained in this work.

  15. Charged de Sitter-like black holes: quintessence-dependent enthalpy and new extreme solutions

    Energy Technology Data Exchange (ETDEWEB)

    Azreg-Ainou, Mustapha [Baskent University, Faculty of Engineering, Ankara (Turkey)

    2015-01-01

    We consider Reissner-Nordstroem black holes surrounded by quintessence where both a non-extremal event horizon and a cosmological horizon exist besides an inner horizon (-1 ≤ ω < -1/3). We determine new extreme black hole solutions that generalize the Nariai horizon to asymptotically de Sitter-like solutions for any order relation between the squares of the charge q{sup 2} and the mass parameter M{sup 2} provided q{sup 2} remains smaller than some limit, which is larger than M{sup 2}. In the limit case q{sup 2} = 9ω{sup 2}M{sup 2}/(9ω{sup 2}-1), we derive the general expression of the extreme cosmo-blackhole, where the three horizons merge, and we discuss some of its properties.We also show that the endpoint of the evaporation process is independent of any order relation between q{sup 2} and M{sup 2}. The Teitelboim energy and the Padmanabhan energy are related by a nonlinear expression and are shown to correspond to different ensembles. We also determine the enthalpy H of the event horizon, as well as the effective thermodynamic volume which is the conjugate variable of the negative quintessential pressure, and show that in general the mass parameter and the Teitelboim energy are different from the enthalpy and internal energy; only in the cosmological case, that is, for Reissner-Nordstroem-de Sitter black hole we have H = M. Generalized Smarr formulas are also derived. It is concluded that the internal energy has a universal expression for all static charged black holes, with possibly a variable mass parameter, but it is not a suitable thermodynamic potential for static-black-hole thermodynamics if M is constant. It is also shown that the reverse isoperimetric inequality holds. We generalize the results to the case of the Reissner-Nordstroem-de Sitter black hole surrounded by quintessence with two physical constants yielding two thermodynamic volumes. (orig.)

  16. REDUCTION OF ENTHALPY RELAXATION IN GELATINE FILMS BY ADDITION OF POLYOLS.

    Science.gov (United States)

    Díaz-Calderón, Paulo; MacNaughtan, Bill; Hill, Sandra; Mitchell, John; Enrione, Javier

    2017-12-16

    The aim of this study was to evaluate the effect of plasticisers with different molecular weights (glycerol and sorbitol) on the structural relaxation kinetics of bovine gelatine films stored under the glass transition temperature (Tg). Plasticisers were tested at weight fractions of 0.0, 0.06 and 0.10. Films conditioned in environments under ∼44% relative humidity gave moisture contents (w/w) in the range 0.14-0.18. The enthalpy relaxation (ΔH) was determined using differential scanning calorimetry (DSC). Samples used had Tg values in the range 24-49 °C. After removing the thermal history (30 °C above Tg, 15 minutes), samples were isothermally stored at 10 °C below Tg for between 2-80 hours. The addition of plasticisers induced a significant reduction in the rate of structural relaxation. The linearisation of ΔH by plotting against the logarithm of ageing time showed a reduction in the slope of samples plasticised with both polyols. The reduction in relaxation kinetics may be related to the ability of polyols to act as enhancers of molecular packing, as recently reported using positron spectroscopy (PALS). However, a direct correlation between the relaxation kinetics and the plasticiser's molecular weight could not be established, suggesting that this phenomenon may be governed by complex molecular gelatin-plasticiser-water interactions. Copyright © 2017. Published by Elsevier B.V.

  17. Enthalpy, Geometric Volume and Logarithmic correction to Entropy for Van-der-Waals Black Hole

    CERN Document Server

    Pradhan, Parthapratim

    2016-01-01

    If the negative cosmological constant is treated as a dynamical pressure and if the volume be its thermodynamically conjugate variable then the gravitational mass can be expressed as the total gravitational enthalpy rather than the energy. Under these circumstances, a new phenomena emerges in the context of extended phase space thermodynamics. We \\emph{examine} here these features for recently discovered Van-der-Waal (VDW) black hole (BH) \\cite{mann15} which is analogous to the VDW fluid. We show that the thermodynamic volume is \\emph{greater} than the naive geometric volume. We also show that the \\emph{Smarr-Gibbs-Duhem} relation is satisfied for this BH. Furthermore, by computing the thermal specific heat we find the local thermodynamic stability criterion for this BH. It has been observed that the BH does \\emph{not} possess any kind of second order phase transition. This is an interesting feature of VDW BH by its own right. Moreover, we also derive \\emph{Cosmic-Censorship-Inequality} for this class of BH. ...

  18. A Multichannel Calorimetric Simultaneous Assay Platform Using a Microampere Constant-Current Looped Enthalpy Sensor Array

    Directory of Open Access Journals (Sweden)

    Hsien-Chin Wei

    2017-02-01

    Full Text Available Calorimetric biochemical measurements offer various advantages such as low waste, low cost, low sample consumption, short operating time, and labor-savings. Multichannel calorimeters can enhance the possibility of performing higher-throughput biochemical measurements. An enthalpy sensor (ES array is a key device in multichannel calorimeters. Most ES arrays use Wheatstone bridge amplifiers to condition the sensor signals, but such an approach is only suitable for null detection and low resistance sensors. To overcome these limitations, we have developed a multichannel calorimetric simultaneous assay (MCSA platform. An adjustable microampere constant-current (AMCC source was designed for exciting the ES array using a microampere current loop measurement circuit topology. The MCSA platform comprises a measurement unit, which contains a multichannel calorimeter and an automatic simultaneous injector, and a signal processing unit, which contains multiple ES signal conditioners and a data processor. This study focused on the construction of the MCSA platform; in particular, construction of the measurement circuit and calorimeter array in a single block. The performance of the platform, including current stability, temperature sensitivity and heat sensitivity, was evaluated. The sensor response time and calorimeter constants were given. The capability of the platform to detect relative enzyme activity was also demonstrated. The experimental results show that the proposed MCSA is a flexible and powerful biochemical measurement device with higher throughput than existing alternatives.

  19. Enthalpies of solution of methylcalix[4]resorcinarene in non-aqueous solvents as a function of concentration and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Riveros, Diana C. [Laboratorio de Termodinamica de Soluciones, Departamento de Quimica, Facultad de Ciencias, Universidad de los Andes, Bogota D.C. (Colombia); Martinez, Fleming [Grupo de Investigaciones Farmaceutico-Fisicoquimicas, Departamento de Farmacia, Facultad de Ciencias, Universidad Nacional de Colombia, Bogota D.C. (Colombia); Vargas, Edgar F., E-mail: edvargas@uniandes.edu.co [Laboratorio de Termodinamica de Soluciones, Departamento de Quimica, Facultad de Ciencias, Universidad de los Andes, Bogota D.C. (Colombia)

    2012-11-20

    Highlights: Black-Right-Pointing-Pointer The solution enthalpies of methylcalix[4]resorcinarene in alcohols have been measured. Black-Right-Pointing-Pointer The solution enthalpies of methylcalix[4]resorcinarene in alcohols are endothermic. Black-Right-Pointing-Pointer Enthalpies of transference are interpreted in terms of proton donor capacity of alcohols. - Abstract: Enthalpies of solution of 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxyresorci[4]arene in methanol, ethanol and propanol as a function of molal concentration at (288.15, 298.15 and 308.15) K were measured calorimetrically. The enthalpies of solvation were estimated. Using propanol as the referent solvent, transfer properties to other alcohols were also calculated. In addition, temperature dependence of the enthalpy of solution at infinite dilution was also obtained. The data were interpreted in terms of solute-solvent interactions.

  20. From a network of computed reaction enthalpies to atom-based thermochemistry (NEAT).

    Science.gov (United States)

    Császár, Attila G; Furtenbacher, Tibor

    2010-04-26

    A simple and fast, weighted, linear least-squares refinement protocol and code is presented for inverting the information contained in a network of quantum chemically computed 0 K reaction enthalpies. This inversion yields internally consistent 0 K enthalpies of formation for the species of the network. The refinement takes advantage of the fact that the accuracy of computed enthalpies depends strongly on the quantum-chemical protocol employed for their determination. Different protocols suffer from different sources of error; thus, the reaction enthalpies computed by them have "random" residual errors. Since it is much more natural for quantum-chemical energy and enthalpy results, including reaction enthalpies, to be based on the electronic ground states of the atoms and not on the historically preferred elemental states, and since these two possible protocols can be converted into each other straightforwardly, it is proposed that first-principles thermochemistry should employ the ground electronic states of atoms. In this scheme, called atom-based thermochemistry (AT), the enthalpy of formation of a gaseous compound corresponds simply to the total atomization energy of the species; it is always positive, and it reflects the bonding strength within the molecule. The inversion protocol developed and based on AT is termed NEAT, which represents the fact that the protocol proceeds from a network of computed reaction enthalpies toward atom-based thermochemistry, most directly to atom-based enthalpies of formation. After assembling a database that consisted of 361 ab initio reactions and reaction enthalpies involving 188 species, collected from 31 literature sources, the following dependable 0 K atom-based enthalpies of formation, Delta(f)${H{{{\\rm AT}\\hfill \\atop 0\\hfill}}}$, all in kJ mol(-1), have been obtained by means of NEAT: H(2)=432.07(0), CH=334.61(15), NH=327.69(25), OH=425.93(21), HF=566.13(31), CO=1072.08(28), O(2)=493.51(34), CH(2)=752.40(21), H(2)O

  1. Enthalpy-Based Screening of Focused Combinatorial Libraries for the Identification of Potent and Selective Ligands.

    Science.gov (United States)

    Baggio, Carlo; Udompholkul, Parima; Barile, Elisa; Pellecchia, Maurizio

    2017-12-15

    In modern drug discovery, the ability of biophysical methods, including nuclear magnetic resonance spectroscopy or surface plasmon resonance, to detect and characterize ligand-protein interactions accurately and unambiguously makes these approaches preferred versus conventional biochemical high-throughput screening of large collections of compounds. Nonetheless, ligand screening strategies that address simultaneously potency and selectivity have not yet been fully developed. In this work, we propose a novel method for screening large collections of combinatorial libraries using enthalpy measurements as a primary screening technique. We demonstrate that selecting binders that are driven by enthalpy (ΔH) results in agents that are not only potent but also more selective for a given target. This general and novel approach, we termed ΔH screening of fPOS (enthalpy screening of focused positional scanning library), combines the principles of focused combinatorial chemistry with rapid calorimetry measurements to efficiently identify potent and selective inhibitors.

  2. A Reaction Method for Estimating Gibbs Energy and Enthalpy of Formation of Complex Minerals

    Science.gov (United States)

    Li, Ruibing; Zhang, Tingan; Liu, Yan; Kuang, Shibo

    2017-04-01

    New and updated thermodynamic data for simple binary compounds are readily available from both experimental measurements and theoretical calculations. Based on these available data, an approach is proposed to predict Gibbs energies and enthalpies of formation for complex minerals of metallurgical, chemical, and other industrial importance. The approach assumes that complex minerals are formed from binary composite oxides, which in turn, are formed from individual pure oxides. The validity of this approach is examined by comparing the calculated values of Gibbs energies and enthalpies against the experimentally measured ones reported in literature. The results show that for typical complex minerals with available experimental data, the calculated results exhibit an average residual of 0.51 pct for Gibbs energies and 0.52 pct for enthalpies, compared to the experimental results. This new approach thus correlates well with experimental approaches and can be applied to most of the complex minerals.

  3. Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

    Science.gov (United States)

    Do, D D; Do, H D; Nicholson, D

    2009-01-29

    We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

  4. Computational Investigation of Enthalpy-Entropy Compensation in Complexation of Glycoconjugated Bile Salts with β-Cyclodextrin and Analogs

    DEFF Research Database (Denmark)

    Tidemand, Kasper Damgaard; Schonbeck, Christian; Holm, Rene

    2014-01-01

    of water molecules in the cavity increased with the DS. Release of water from the cavity resulted in a positive enthalpy change, which correlates qualitatively with the experimentally determined increase in complexation enthalpy and contributes to the enthalpy-entropy compensation. The positive change...... in complexation entropy with DS was not able to compensate for this unfavorable change in enthalpy induced by the HP substituents, resulting in a destabilizing effect. This was found to originate from fixation of the HP substituents and decreased free rotation of the bile salts within the CD cavities....

  5. Enthalpy analysis and Heat Exchanger Sizing of an Air-cooled Proton Exchange Membrane Fuel Cell System

    DEFF Research Database (Denmark)

    Gao, Xin; Berning, Torsten; Kær, Søren Knudsen

    the warmer exhaust air is used to pre-heat and also humidify the incoming colder and dryer air stream using an enthalpy wheel. It is important to thermodynamically understand such a fuel cell system, and in this work the enthalpy streams and the humidity stream are followed throughout the fuel cell system...... simulations have been carried out to better understand the distribution of the reactant air over the fuel cell stack and the resulting temperature distribution across the stack. These results suggest that the humidifying function of the current enthalpy wheel is negligible and a smaller enthalpy wheel...

  6. Effect of the initial stage of annealing on modeling of enthalpy relaxation in a hyperquenched glass

    DEFF Research Database (Denmark)

    Zhang, Yanfei; Guo, Xiaoju; Yue, Yuanzheng

    2013-01-01

    One of the major challenges in glass relaxation study is to establish a universal model describing the enthalpy relaxation in both the hyperquenched glass (HQG) (i.e., far from equilibrium) and the partially annealed hyperquenched glass(AHQG). In particular, the detailed features of the enthalpy...... proposed composite relaxation function [L. Hornboell, et al., Chem. Phys. Lett. 1-3 (2010) 37] is a reasonable approach for describing those features. In addition, our modeling results imply that the structural heterogeneity plays a crucial role in relaxation of HQG....

  7. Covalent and ionic nature of the dative bond and account of accurate ammonia borane binding enthalpies.

    Science.gov (United States)

    Plumley, Joshua A; Evanseck, Jeffrey D

    2007-12-27

    The inherent difficulty in modeling the energetic character of the B-N dative bond has been investigated utilizing density functional theory and ab initio methods. The underlying influence of basis set size and functions, thermal corrections, and basis set superposition error (BSSE) on the predicted binding enthalpy of ammonia borane (H3B-NH3) and four methyl-substituted ammonia trimethylboranes ((CH3)3B-N(CH3)nH3-n; n = 0-3) has been evaluated and compared with experiment. HF, B3LYP, MPW1K, MP2, QCISD, and QCISD(T) have been utilized with a wide range of Pople and correlation-consistent basis sets, totaling 336 levels of theory. MPW1K, B3LYP, and HF result in less BSSE and converge to binding enthalpies with fewer basis functions than post-SCF techniques; however, the methods fail to model experimental binding enthalpies and trends accurately, producing mean absolute deviations (MADs) of 5.1, 10.8, and 16.3 kcal/mol, respectively. Despite slow convergence, MP2, QCISD, and QCISD(T) using the 6-311++G(3df,2p) basis set reproduce the experimental binding enthalpy trend and result in lower MADs of 2.2, 2.6, and 0.5 kcal/mol, respectively, when corrected for BSSE and a residual convergence error of ca. 1.3-1.6 kcal/mol. Accuracy of the predicted binding enthalpy is linked to correct determination of the bond's dative character given by charge-transfer frustration, QCTF = -(Delta QN + Delta QB). Frustration gauges the incompleteness of charge transfer between the donor and the acceptor. The binding enthalpy across ammonia borane and methylated complexes is correlated to its dative character (R2 = 0.91), where a more dative bond (less charge-transfer frustration) results in a weaker binding enthalpy. However, a balance of electronic and steric factors must be considered to explain trends in experimentally reported binding enthalpies. Dative bond descriptors, such as bond ionicity and covalency are important in the accurate characterization of the dative bond. The B

  8. Standard Practice for Measuring Plasma Arc Gas Enthalpy by Energy Balance

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This practice covers the measurement of total gas enthalpy of an electric-arc-heated gas stream by means of an overall system energy balance. This is sometimes referred to as a bulk enthalpy and represents an average energy content of the test stream which may differ from local values in the test stream. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  9. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, January-March 1986

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1986-04-30

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the seventh quarter, preliminary enthalpy measurements for the 5/6:1/6 m-cresol/tetralin binary mixture have been completed and are included in Appendix A at the end of this report. Vapor liquid equilibria VLE measurements for the m-cresol/tetralin system have been completed for four isotherms; 250, 275, 300, 325/sup 0/C. These results and a summary of progress to date for the VLE apparatus are in the appendix at the end of this report. 10 refs., 15 figs., 6 tabs.

  10. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, July-September 1985

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1985-10-31

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the fifth quarter, preliminary enthalpy measurements for the 50/50 mole percent m-cresol/tetralin binary mixture have almost been completed and figure illustrating the preliminary results have been included in this report. Vapor liquid equilibria measurements for the m-cresol/quinoline system have been completed for four isotherms. Results have been included in this report. 6 refs., 13 figs., 4 tabs.

  11. Isosteric Vapor Pressure – Temperature Data for Water Sorption in Hardened Cement Paste: Enthalpy, Entropy and Sorption Isotherms at Different Temperatures

    DEFF Research Database (Denmark)

    Radjy, Fariborz; Sellevold, Erik J.; Hansen, Kurt Kielsgaard

    . The accuracies for pressure, enthalpy and entropy are found to be 0.5% or less. PART II: The TPA-system has been used to generate water vapor pressure – temperature data for room temperature – and steam cured hardened cement pastes as well as porous vycor glass. The moisture contents range from saturated to dry...... and the temperatures range from 2 to 95 °C, differing for the specimen types. The data has been analyzed to yield differential enthalpy and entropy of adsorption, as well as the dependence of the relative vapor pressure on temperature at various constant moisture contents. The implications for the coefficient...... of thermal expansion have been explored....

  12. Estimativa por DSC das entalpias de sublimação da etilenouréia e da propilenouréia: algumas correlações empíricas envolvendo amidas e tioamidas Estimative by DSC data of the sublimation enthalpies for ethyleneurea and propyleneurea: some empirical correlations with amides and tioamides

    Directory of Open Access Journals (Sweden)

    Robson Fernandes de Farias

    1999-07-01

    Full Text Available By using DSC data, the enthaplies of sublimation for ethyleneurea and propyleneurea, are calculated as 84 and 89 kJ mol-1 respectively. Using the vaporization enthalpy values for dimethylethyleneurea and dimethylprophyleneurea, as obtained from literature, the empirical relation: Dcrg Hmo (1/ Dcrg Hmo (2 = Dlg Hmo (1/ Dlg Hmo(2 = constant, that relate sublimation or vaporization enthalpies of two different substances and of its methylated derivatives, is obtained. Correlations like that are found to another ureas and thioureas.

  13. Enthalpy-based equation of state for highly porous materials employing modified soft sphere fluid model

    Science.gov (United States)

    Nayak, Bishnupriya; Menon, S. V. G.

    2018-01-01

    Enthalpy-based equation of state based on a modified soft sphere model for the fluid phase, which includes vaporization and ionization effects, is formulated for highly porous materials. Earlier developments and applications of enthalpy-based approach had not accounted for the fact that shocked states of materials with high porosity (e.g., porosity more than two for Cu) are in the expanded fluid region. We supplement the well known soft sphere model with a generalized Lennard-Jones formula for the zero temperature isotherm, with parameters determined from cohesive energy, specific volume and bulk modulus of the solid at normal condition. Specific heats at constant pressure, ionic and electronic enthalpy parameters and thermal excitation effects are calculated using the modified approach and used in the enthalpy-based equation of state. We also incorporate energy loss from the shock due to expansion of shocked material in calculating porous Hugoniot. Results obtained for Cu, even up to initial porosities ten, show good agreement with experimental data.

  14. Fractured Anhydrite as a Geothermal Source in a Low Enthalpy Context (Southern Permian Basin, Netherlands)

    NARCIS (Netherlands)

    Daniilidis, Alexandros; Herber, Marinus

    2015-01-01

    Increased heat flow associated with the presence of salt domes could be beneficial for geothermal energy applications in a low enthalpy nvironment. Anhydrite layers within such salt domes could be a potential geothermal target. These layers are known to undergo brittle deformation, which in turn can

  15. The Correlation of Standard Entropy with Enthalpy Supplied from 0 to 298.15 K

    Science.gov (United States)

    Lambert, Frank L.; Leff, Harvey S.

    2009-01-01

    As a substance is heated at constant pressure from near 0 K to 298 K, each incremental enthalpy increase, dH, alters entropy by dH/T, bringing it from approximately zero to its standard molar entropy S degrees. Using heat capacity data for 32 solids and CODATA results for another 45, we found a roughly linear relationship between S degrees and…

  16. Enthalpies of mixing in binary liquid alloys of lutetium with 3d metals

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Michael; Berezutski, Vadim [National Academy of Sciences, Kyiv (Ukraine). I. Frantsevich Institute for Problems of Materials Science; Usenko, Natalia; Kotova, Natalia [Taras Shevchenko National Univ., Kyiv (Ukraine). Dept. of Chemistry

    2017-01-15

    The enthalpies of mixing in binary liquid alloys of lutetium with chromium, cobalt, nickel and copper were determined at 1 773 - 1 947 K by isoperibolic calorimetry. The enthalpies of mixing in the Lu-Cr melts (measured up to 40 at.% Cr) demonstrate endothermic effects (ΔH = 6.88 ± 0.66 kJ . mol{sup -1} at x{sub Lu} = 0.60), whereas significant exothermic enthalpies of mixing have been established within a wide composition region for the Co-Lu, Ni-Lu and Cu-Lu liquid alloys. Minimum values of the integral enthalpy of mixing are as follows: ΔH{sub min} = -23.57 ± 1.41 kJ . mol{sup -1} at x{sub Lu} = 0.38 for the Co-Lu system; ΔH{sub min} = -48.65 ± 2.83 kJ . mol{sup -1} at x{sub Lu} = 0.40 for the Ni-Lu system; ΔH{sub min} = -24.63 ± 1.52 kJ . mol{sup -1} at x{sub Lu} = 0.37 for the Cu-Lu system.

  17. An evaluation of interferences in heat production from low enthalpy geothermal doublets systems

    NARCIS (Netherlands)

    Willems, C.J.L.; Maghami Nick, Hamidreza M.; Weltje, G.J.; Bruhn, D.F.

    2017-01-01

    Required distance between doublet systems in low enthalpy geothermal heat exploitation is often not fully elucidated. The required distance aims to prevent negative interference influencing the utilisation efficiency of doublet systems. Currently production licence areas are often issued based on

  18. Enthalpy of mixing of liquid Cu-Fe-Hf alloys at 1873 K

    Energy Technology Data Exchange (ETDEWEB)

    Agraval, Pavel; Turchanin, Mikhail [Donbass State Engineering Academy, Kramatorsk (Ukraine). Metallurgical Dept.; Dreval, Liya [Donbass State Engineering Academy, Kramatorsk (Ukraine). Metallurgical Dept.; Materials Science International Services GmbH (MSI), Stuttgart (Germany)

    2016-12-15

    In the ternary Cu-Fe-Hf system, the mixing enthalpies of liquid alloys were investigated at 1873 K using a high-temperature isoperibolic calorimeter. The experiments were performed along the sections x{sub Cu}/x{sub Fe} = 3/1, 1/1 at x{sub Hf} = 0-0.47 and along the section x{sub Cu}/x{sub Fe} = 1/3 at x{sub Hf} = 0-0.13. The limiting partial enthalpies of mixing of undercooled liquid hafnium in liquid Cu-Fe alloys, Δ{sub mix} anti H{sub Hf}{sup ∞}, are (-122 ± 9) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 3/1), (-106 ± 9) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 1/1), and (-105 ± 2) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 1/3). In the investigated composition range, the integral mixing enthalpies are sign-changing. For the integral mixing enthalpy, an analytical expression was obtained by the least squares fit of the experimental results using the Redlich-Kister-Muggianu polynomial.

  19. Excess Enthalpies of Mixing of Binary Mixtures of NaCl, KCl, NaBr ...

    African Journals Online (AJOL)

    NJD

    2004-07-01

    Jul 1, 2004 ... Excess enthalpies of mixing for six possible binary combinations of solutions of NaCl, KCl, NaBr and KBr in mixed ternary solvents composed of ... practical interest for industrial and geochemical applications. Interest in ... Pitzer,11–16 where the excess Gibbs energy of the system is repre- sented by a ...

  20. The Relationship between Lattice Enthalpy and Melting Point in Magnesium and Aluminium Oxides. Science Notes

    Science.gov (United States)

    Talbot, Christopher; Yap, Lydia

    2013-01-01

    This "Science Note" presents a study by Christopher Talbot and Lydia Yap, who teach IB Chemistry at Anglo-Chinese School (Independent), Republic of Singapore, to pre-university students. Pre-university students may postulate the correlation between the magnitude of the lattice enthalpy compound and its melting point, since both…

  1. Rapid estimation of activation enthalpies for cytochrome-P450-mediated hydroxylations.

    Science.gov (United States)

    Mayeno, Arthur N; Robinson, Jonathan L; Reisfeld, Brad

    2011-03-01

    Cytochrome P450 (CYP) enzymes play a critical role in detoxication and bioactivation of xenobiotics; thus, the ability to predict the biotransformation rates and regioselectivity of CYP enzymes toward substrates is an important goal in toxicology and pharmacology. Here, we present the use of the semiempirical quantum chemistry method SAM1 to rapidly estimate relative activation enthalpies (ΔH(‡)) for the hydroxylation of aliphatic carbon centers of various substrates. The ΔH(‡) were determined via a reaction path calculation, in the reverse direction (RRP), using the iron-hydroxo-porphine intermediate and the substrate radical. The SAM1 ΔH(‡) were calculated via unrestricted Hartree-Fock (UHF) and configuration interaction (CI) formalisms for both the doublet and quartet spin states. The SAM1 RRP ΔH(‡), after subtracting a correction factor, were compared with density functional theory (DFT) B3LYP activation energies for two sets of substrates and showed R(2) ranging from 0.69 to 0.89, and mean absolute differences ranging from 1.2 ± 1.0 to 1.7 ± 1.5 kcal/mol. SAM1 UHF and CI RRP calculation times were, on average, more than 200 times faster than those for the corresponding forward reaction path DFT calculations. Certain key transition-state (TS) geometry measurements, such as the forming O···H bond length, showed good correlation with the DFT values. These results suggest that the SAM1 RRP approach can be used to rapidly estimate the DFT activation energy and some key TS geometry measurements and can potentially be applied to estimate substrate hydroxylation rates and regioselectivity by CYP enzymes. Copyright © 2010 Wiley Periodicals, Inc.

  2. Der Weg ist Das Ziel: Enthalpy Relaxation Geospeedometry in Volcanic Facies

    Science.gov (United States)

    Dingwell, D. B.

    2006-12-01

    The advent of reliable high temperature scanning calorimetry has had a major impact on the analysis of the thermodynamics of geomaterials at high temperature. A relatively novel and unconventional use of scanning calorimetry - enthalpy relaxation geospeedometry - has been employed in volcanic facies in the past ten years. Using these techniques,information on the cooling of natural and synthetic glasses can be obtained. Reliable calibration of the technique on a wide range of glasses from various volcanic facies has led to the development of a fully quantitative method for the determination of effective cooling rate on pristine natural glasses. The evidence accumulated to date reveals an extraordinarily rich variation in volcanic cooling histories. The analysis of the glass transition region in volcanic glasses has yielded cooling rates over seven log units. The highest cooling rates are observed for explosively subaqueously erupted basalts from Loihi seamount. These filigran limu varieties are inferred to have cooled at up to >100,000 K/sec. The slowest effective cooling rates are observed in welded spatter-fed pantelleritic glasses from Mayor Island NZ for which values of several K/day have been inferred. Even whithin individual volcanic terrains, and individual eruptive events the span of thermal histories is impressive. At Teide, Tenerife, 4-5 orders of magnitude of variation have been recorded. Herein lies perhaps the real power of the technique - facies-specific thermal histories - whose employment in volcanology adds a useful tool to the understanding of pristine units. Finally, I observe that the calorimetric glass transition, once a nagging detail obstructing the interpretation of calorimetric results, has become a useful tool for understanding glass petrogenesis in nature.

  3. Preliminary Results from Electric Arc Furnace Off-Gas Enthalpy Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Nimbalkar, Sachin U [ORNL; Thekdi, Arvind [E3M Inc; Keiser, James R [ORNL; Storey, John Morse [ORNL

    2015-01-01

    This article describes electric arc furnace (EAF) off-gas enthalpy models developed at Oak Ridge National Laboratory (ORNL) to calculate overall heat availability (sensible and chemical enthalpy) and recoverable heat values (steam or power generation potential) for existing EAF operations and to test ORNL s new EAF waste heat recovery (WHR) concepts. ORNL s new EAF WHR concepts are: Regenerative Drop-out Box System and Fluidized Bed System. The two EAF off-gas enthalpy models described in this paper are: 1.Overall Waste Heat Recovery Model that calculates total heat availability in off-gases of existing EAF operations 2.Regenerative Drop-out Box System Model in which hot EAF off-gases alternately pass through one of two refractory heat sinks that store heat and then transfer it to another gaseous medium These models calculate the sensible and chemical enthalpy of EAF off-gases based on the off-gas chemical composition, temperature, and mass flow rate during tap to tap time, and variations in those parameters in terms of actual values over time. The models provide heat transfer analysis for the aforementioned concepts to confirm the overall system and major component sizing (preliminary) to assess the practicality of the systems. Real-time EAF off-gas composition (e.g., CO, CO2, H2, and H2O), volume flow, and temperature data from one EAF operation was used to test the validity and accuracy of the modeling work. The EAF off-gas data was used to calculate the sensible and chemical enthalpy of the EAF off-gases to generate steam and power. The article provides detailed results from the modeling work that are important to the success of ORNL s EAF WHR project. The EAF WHR project aims to develop and test new concepts and materials that allow cost-effective recovery of sensible and chemical heat from high-temperature gases discharged from EAFs.

  4. Downward-deployed tethered platforms for high enthalpy aerothermodynamic research

    Science.gov (United States)

    Wood, George M.; Siemers, Paul M.; Squires, R. Kenneth; Wolf, Henry; Carlomagno, Giovanni M.

    1988-01-01

    The data on aerothermodynamic and aerodynamic interactions at altitudes above 50 km is extremely limited because of the relative inaccessibility of the region to research vehicles of any sort. This paper addresses the practicability of using downward deployed satellites tethered to an orbiting host vehicle in order to obtain steady-state data in the upper reaches of the region above 80 or 90 km.

  5. Measuring the enthalpies of interaction between glycine, L-cysteine, glycylglycine, and sodium dodecyl sulfate in aqueous solutions

    Science.gov (United States)

    Badelin, V. G.; Mezhevoi, I. N.; Tyunina, E. Yu.

    2017-03-01

    Calorimetric measurements of enthalpies of solution Δsol H m for glycine, L-cysteine, and glycylglycine in aqueous solutions of sodium dodecyl sulfate (SDS) with concentrations of up to 0.05 mol kg-1 are made. Standard enthalpy of solution Δsol H 0 and enthalpy of transfer Δtr H 0 of the dipeptide from water into mixed solvent are calculated. The calculated enthalpy coefficients of paired interactions of amino acids and dipeptide with SDS prove to be positive. Hydrophobic interactions between the biomolecules and SDS are found to have a major impact on the enthalpies of interaction in the three-component systems under study, within the indicated range of concentrations.

  6. Accurate Reaction Enthalpies and Sources of Error in DFT Thermochemistry for Aldol, Mannich, and α-Aminoxylation Reactions

    Science.gov (United States)

    Wheeler, Steven E.; Moran, Antonio; Pieniazek, Susan N.

    2009-01-01

    Enthalpies for bond-forming reactions that are subject to organocatalysis have been predicted using the high-accuracy CBS-QB3 model chemistry and six DFT functionals. Reaction enthalpies were decomposed into contributions from changes in bonding and other intramolecular effects via the hierarchy of homodesmotic reactions. The order of the reaction exothermicities (aldol < Mannich ≈ α-aminoxylation) arises primarily from changes in formal bond types mediated by contributions from secondary intramolecular interactions. In each of these reaction types, methyl substitution at the β- and γ-positions stabilizes the products relative to the unsubstituted case. The performance of six DFT functionals (B3LYP, B3PW91, B1B95, MPW1PW91, PBE1PBE, and M06-2X), MP2, and SCS-MP2 has been assessed for the prediction of these reaction enthalpies. Even though the PBE1PBE and M06-2X functionals perform well for the aldol and Mannich reactions, errors roughly double when these functionals are applied to the α-aminoxylation reactions. On the other hand, B3PW91 and B1B95, which offer modest accuracy for the aldol and Mannich reactions, yield reliable predictions for the two α-aminoxylation reactions. The excellent performance of the M06-2X and PBE1PBE functionals for aldol and Mannich reactions stems from the cancellation of sizeable errors arising from inadequate descriptions of the underlying bond transformations and intramolecular interactions. SCS-MP2/cc-pVTZ performs most consistently across these three classes of reactions, although the reaction exothermicities are systematically underestimated by 1–3 kcal mol−1. Conventional MP2, when paired with the cc-pVTZ basis set, performs somewhat better than SCS-MP2 for some of these reactions, particularly the α-aminoxylations. Finally, the merits of benchmarking DFT functionals for the set of simple chemically meaningful transformations underlying all bond-forming reactions are discussed. PMID:19711937

  7. Case studies for utilizing groundwater-source and low-enthalpy geothermal resources in Korea

    Science.gov (United States)

    Kim, K.-H.; Shin, J.; Lee, K.-K.; Lee, T. J.

    2012-04-01

    As one of the top 10 oil-consuming countries in the world, Korea recently has had a great interest in extending the ways to utilize renewable energy. In this regard, geothermal energy resource is attracting more concerns from both of the government and the research field. Korea has neither active volcanic sites nor areas with abnormally higher heat flow. In spite of these natural conditions, many efforts have been exerted to utilize geothermal energy. Here, we introduce two case studies of using groundwater-source geothermal energy with relatively low-enthalpy: One is a riverbank filtration facility, which has been using some of its riverbank filtrate water for the indoor air-conditioning. The other is the first EGS plant planning site, where a few fault-related artesian wells reaching 70C were discovered lately. Numerical simulations to predict the temperature evolution of the two sites, which is dominated by several hydrogeologic factors, were carried out and compared. Simulation of temperature profile of riverbank filtrate water using HydroGeoSphere shows that the primary factor in determining filtrate water temperature is the pumping rate. It also shows that maintaining the facility operation with present pumping rate for the next 30 years will not cause any significant change of water temperature. However, following the new plan of the facility to install additional 37 wells with 6 times higher pumping rate than the current rate might cause about 2C decrease in filtrate water temperature in 10 years after the extension. Simulation for the temperature evolution in a faulted geothermal reservoir in EGS planning site under the supposed injection-extraction operating conditions were carried out using TOUGH2. A MINC model including a hydraulic discontinuity, which reflected the analysis from several geophysical explorations, was generated. Temperature distribution calculated from the simulation shows a rise of relatively hot geothermal water along the fault plane

  8. Generalized enthalpy based equation of state for multi-component mixtures

    Science.gov (United States)

    Nayak, Bishnupriya; Menon, S. V. G.

    2017-04-01

    An equation of state using pressure and temperature as independent variables, including non-equilibrium thermal energies of components and explicit accounting of thermal electron effects, is formulated for multi component mixtures. As pressure equilibration is faster in mixtures, this approach is more suited than earlier schemes using Mie-Gruneisen equation of state. Due to the reliance on enthalpy, in lieu of energy, it is directly applicable also to treat porosity effects. The formulation leads to an expression for mixture volume which consists of a term depended on enthalpy differences of components, in addition to those depending on average mixture parameters. A method to estimate non-equilibrium thermal effects, using component Hugoniot to compute non-equilibrium temperatures, is also proposed in this work. Results obtained for two and three component mixtures compare well with experimental Hugoniot data.

  9. The influence of facies heterogeneity on the doublet performance in low-enthalpy geothermal sedimentary reservoirs

    DEFF Research Database (Denmark)

    Crooijmans, R. A.; Willems, C. J L; Nick, Hamid

    2016-01-01

    A three-dimensional model is used to study the influence of facies heterogeneity on energy production under different operational conditions of low-enthalpy geothermal doublet systems. Process-based facies modelling is utilised for the Nieuwerkerk sedimentary formation in the West Netherlands Basin...... and the energy recovery rate for different discharge rates and the production temperature (Tmin) above which the doublet is working. With respect to the results, we propose a design model to estimate the life time and energy recovery rate of the geothermal doublet. The life time is estimated as a function of N...... errors in predicting the life time of low-enthalpy geothermal systems for N/G values below 70%....

  10. Generalized enthalpy model of a high-pressure shift freezing process

    KAUST Repository

    Smith, N. A. S.

    2012-05-02

    High-pressure freezing processes are a novel emerging technology in food processing, offering significant improvements to the quality of frozen foods. To be able to simulate plateau times and thermal history under different conditions, in this work, we present a generalized enthalpy model of the high-pressure shift freezing process. The model includes the effects of pressure on conservation of enthalpy and incorporates the freezing point depression of non-dilute food samples. In addition, the significant heat-transfer effects of convection in the pressurizing medium are accounted for by solving the two-dimensional Navier-Stokes equations. We run the model for several numerical tests where the food sample is agar gel, and find good agreement with experimental data from the literature. © 2012 The Royal Society.

  11. Air to air fixed plate enthalpy heat exchanger, performance variation and energy analysis

    Energy Technology Data Exchange (ETDEWEB)

    Nasif, Mohammad Shakir [Universiti Teknologi Petronas, Bandar Seri Iskandar (Malaysia); Alwaked, Rafat [Prince Mohammad Bin Fahd University, Al Khobar (Saudi Arabia); Behnia, Masud [University of Sydney, Sydney (Australia); Morrison, Graham [The University of New South Wales, Sydney (Australia)

    2013-11-15

    The thermal performance of a Z shape enthalpy heat exchanger utilising 70 gsm Kraft paper as the heat and moisture transfer surface has been investigated. Effects of different inlet air humidity ratio conditions on the heat exchanger effectiveness and on the energy recovered by the heat exchanger have been the main focus of this investigation. A typical air conditioning cooling coil which incorporates an enthalpy heat exchanger has been modelled for tropical climate. Under test conditions, results have shown that latent effectiveness and the moisture resistance coefficient have strong dependency on the inlet air humidity ratio. Moreover, the latent effectiveness has been found to be strongly dependent on the moisture resistance coefficient rather than the convective mass transfer coefficient. Finally, annual energy analysis for Singapore weather conditions have also shown that energy recovered under variable inlet air conditions is 15% less than that recovered under constant inlet air conditions for the same heat exchanger.

  12. Down-Hole Heat Exchangers: Modelling of a Low-Enthalpy Geothermal System for District Heating

    Directory of Open Access Journals (Sweden)

    M. Carlini

    2012-01-01

    Full Text Available In order to face the growing energy demands, renewable energy sources can provide an alternative to fossil fuels. Thus, low-enthalpy geothermal plants may play a fundamental role in those areas—such as the Province of Viterbo—where shallow groundwater basins occur and conventional geothermal plants cannot be developed. This may lead to being fuelled by locally available sources. The aim of the present paper is to exploit the heat coming from a low-enthalpy geothermal system. The experimental plant consists in a down-hole heat exchanger for civil purposes and can supply thermal needs by district heating. An implementation in MATLAB environment is provided in order to develop a mathematical model. As a consequence, the amount of withdrawable heat can be successfully calculated.

  13. Enthalpy of solution of biuret in various aqueous electrolyte solutions and in an urea solution

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Hisashi; Murakami, Sachio (Osaka City Univ. (Japan))

    1989-06-30

    Enthalpies of biuret which is simplest amido acid and does not have hydrophobic group, in various aqueous solutions and in urea solution were measured at 298.15K to clarify the influence of salt on polymer conformal changes of organism or structure and functions of membrane. The isoperibol calorimeter where the quartz thermometer was used as the thermal sensor, was used in the measurement. The performance of this calorimeter was tested by comparing measurements with values in references. From the analysis of enthalpies of biuret solutions, following results of solute-solute-solvent interactions could be obtained: the rate where biuret destroys water structure is smaller in salt solutions than in aqueous solutions and the tendency depends on the ion size; ion-water interaction weakens owing to the ion-biuret interaction in salt solution of biuret; and water molecules are made free. 25 refs., 4 figs., 5 tabs.

  14. Generalized enthalpy based equation of state for multi-component mixtures

    Directory of Open Access Journals (Sweden)

    Bishnupriya Nayak

    2017-04-01

    Full Text Available An equation of state using pressure and temperature as independent variables, including non-equilibrium thermal energies of components and explicit accounting of thermal electron effects, is formulated for multi component mixtures. As pressure equilibration is faster in mixtures, this approach is more suited than earlier schemes using Mie-Gruneisen equation of state. Due to the reliance on enthalpy, in lieu of energy, it is directly applicable also to treat porosity effects. The formulation leads to an expression for mixture volume which consists of a term depended on enthalpy differences of components, in addition to those depending on average mixture parameters. A method to estimate non-equilibrium thermal effects, using component Hugoniot to compute non-equilibrium temperatures, is also proposed in this work. Results obtained for two and three component mixtures compare well with experimental Hugoniot data.

  15. Excess enthalpy, density, and heat capacity for binary systems of alkylimidazolium-based ionic liquids + water

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Miaja, Gonzalo; Troncoso, Jacobo [Departamento de Fisica Aplicada, Universidad de Vigo, Facultad de Ciencias, Campus As Lagoas, 32004 Ourense (Spain); Romani, Luis [Departamento de Fisica Aplicada, Universidad de Vigo, Facultad de Ciencias, Campus As Lagoas, 32004 Ourense (Spain)], E-mail: romani@uvigo.es

    2009-02-15

    Experimental measurements of excess molar enthalpy, density, and isobaric molar heat capacity are presented for a set of binary systems ionic liquid + water as a function of temperature at atmospheric pressure. The studied ionic liquids are 1-butyl-3-methylpyridinium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. Excess molar enthalpy was measured at 303.15 K whereas density and heat capacity were determined within the temperature range (293.15 to 318.15) K. From experimental data, excess molar volume and excess molar isobaric heat capacity were calculated. The analysis of the excess properties reveals important differences between the studied ionic liquids which can be ascribed to their capability to form hydrogen bonds with water molecules.

  16. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, July-September 1980

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1980-09-15

    Equipment modifications to a Freon 11 boil-off type calorimeter are described. The calorimetric system was used to measure the enthalpies of thiophene experimentally. Data were taken over a temperature range of 100/sup 0/F to 750/sup 0/F at pressures of 50, 100, 200, 400, 600, 825.9 (the critical), 1000, and 1500 psia. Thermodynamic properties derived from the data are compared to values in the literature, and the agreement is exceptionally good. The data are then compared directly to results calculated by means of two correlations: a modification of the BWR equation of state by Kesler and Lee, and a modified SRK equation of state method. Both correlations are found to work well in predicting the enthalpy of thiophene.

  17. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, April-June 1986

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1986-07-31

    Enthalpy measurements for the m-cresol/tetralin binary system, and the quinoline/tertralin binary system have been completed and are included. A calibration check on the calorimeter was performed and is presented in Appendix C. Vapor liquid equilibria measurements for the quinoline/tetralin system have been completed for four isotherms; 250, 275, 300, and 325/sup 0/C. These results and a summary of progress to date for the VLE apparatus are in the appendix at the end of this report. Also, preliminary work has begun on the quinoline/m-cresol/tetralin ternary system. Correlational work has consisted of the development of mathematical expressions for fugacity and enthalpy using various combinations of mixing rules and equations of state discussed in earlier reports. Also maximum likelihood routines has been written to determine the necessary parameters for binary data obtained in this investigation.

  18. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, April-June 1985

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1985-07-31

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the fourth quarter enthalpy measurements and a preliminary analysis on tetralin data were completed. A new pump was installed eliminating the need for a pressure adjuster in the pressure system. This pump provides pulse free flow even at a pressure of 1500 psia. During the next quarter, measurements on the binary system m-cresol/tetralin will begin. Vapor liquid equilibria measurements for the m-cresol/quinoline system have begun for four isotherms. Preliminary results have been included in this report. These measurements will be completed in the next quarter and work will be started on the m-cresol/tetralin system. 12 refs., 5 figs., 4 tabs.

  19. Dehydration enthalpy of alkali-cations-exchanged montmorillonite from thermogravimetric analysis.

    Science.gov (United States)

    Kharroubi, M; Balme, S; Henn, F; Giuntini, J C; Belarbi, H; Haouzi, A

    2009-01-15

    Dehydration of a series of homoionic alkali-exchanged montmorillonites is studied at different treatment temperatures by means of thermogravimetric analysis. More specifically, we investigate the last stages of dehydration when the number of adsorbed water molecules corresponds, at maximum, to a monolayer. Weight losses are measured at several constant temperatures as a function of time. Application of Van't Hoff's law yields the dehydration enthalpy. Trends and data similar to those reported from other experimental conditions are found. Comparison with X-ray data and with the dissociation enthalpy of alkali cation/water complexes shows that dehydration of weakly hydrated homoionic alkali montmorillonites results from the competition between opposite energy contributions due to (i) the cation solvation, (ii) the hydration of the silicate interlayer surface, and (iii) the structural swelling. So, depending on the balance between these various energy contributions, different behaviors are observed according to the nature of the alkali cations.

  20. An evaluation of interferences in heat production from low enthalpy geothermal doublets systems

    DEFF Research Database (Denmark)

    Willems, Cees J. L.; Nick, Hamidreza M.; Weltje, Gert Jan

    2017-01-01

    Required distance between doublet systems in low enthalpy geothermal heat exploitation is often not fully elucidated. The required distance aims to prevent negative interference influencing the utilisation efficiency of doublet systems. Currently production licence areas are often issued based...... and minimal required production temperature. The results of this study can be used to minimize negative interference or optimise positive interference aiming at improving geothermal doublet deployment efficiency. (C) 2017 The Authors. Published by Elsevier Ltd....

  1. Large-scale calculations of gas phase thermochemistry : Enthalpy of formation, standard entropy, and heat capacity

    OpenAIRE

    Ghahremanpour, Mohammad M.; van Maaren, Paul J.; Ditz, Jonas C.; Lindh, Roland; van der Spoel, David

    2016-01-01

    Large scale quantum calculations for molar enthalpy of formation (Delta(f) H-0), standard entropy (S-0), and heat capacity (C-V) are presented. A large data set may help to evaluate quantum thermochemistry tools in order to uncover possible hidden shortcomings and also to find experimental data that might need to be reinvestigated, indeed we list and annotate approximately 200 problematic thermochemistry measurements. Quantum methods systematically underestimate S-0 for flexible molecules in ...

  2. Equivalent Temperature-Enthalpy Diagram for the Study of Ejector Refrigeration Systems

    Directory of Open Access Journals (Sweden)

    Mohammed Khennich

    2014-05-01

    Full Text Available The Carnot factor versus enthalpy variation (heat diagram has been used extensively for the second law analysis of heat transfer processes. With enthalpy variation (heat as the abscissa and the Carnot factor as the ordinate the area between the curves representing the heat exchanging media on this diagram illustrates the exergy losses due to the transfer. It is also possible to draw the paths of working fluids in steady-state, steady-flow thermodynamic cycles on this diagram using the definition of “the equivalent temperature” as the ratio between the variations of enthalpy and entropy in an analyzed process. Despite the usefulness of this approach two important shortcomings should be emphasized. First, the approach is not applicable for the processes of expansion and compression particularly for the isenthalpic processes taking place in expansion valves. Second, from the point of view of rigorous thermodynamics, the proposed ratio gives the temperature dimension for the isobaric processes only. The present paper proposes to overcome these shortcomings by replacing the actual processes of expansion and compression by combinations of two thermodynamic paths: isentropic and isobaric. As a result the actual (not ideal refrigeration and power cycles can be presented on equivalent temperature versus enthalpy variation diagrams. All the exergy losses, taking place in different equipments like pumps, turbines, compressors, expansion valves, condensers and evaporators are then clearly visualized. Moreover the exergies consumed and produced in each component of these cycles are also presented. The latter give the opportunity to also analyze the exergy efficiencies of the components. The proposed diagram is finally applied for the second law analysis of an ejector based refrigeration system.

  3. Kinetic evidence of an apparent negative activation enthalpy in an organocatalytic process

    KAUST Repository

    Han, Xiao

    2013-08-30

    A combined kinetic and computational study on our tryptophan-based bifunctional thiourea catalyzed asymmetric Mannich reactions reveals an apparent negative activation enthalpy. The formation of the pre-transition state complex has been unambiguously confirmed and these observations provide an experimental support for the formation of multiple hydrogen bonding network between the substrates and the catalyst. Such interactions allow the creation of a binding cavity, a key factor to install high enantioselectivity.

  4. Dominant Alcohol-Protein Interaction via Hydration-Enabled Enthalpy-Driven Binding Mechanism

    Science.gov (United States)

    Chong, Yuan; Kleinhammes, Alfred; Tang, Pei; Xu, Yan; Wu, Yue

    2015-01-01

    Water plays an important role in weak associations of small drug molecules with proteins. Intense focus has been on binding-induced structural changes in the water network surrounding protein binding sites, especially their contributions to binding thermodynamics. However, water is also tightly coupled to protein conformations and dynamics, and so far little is known about the influence of water-protein interactions on ligand binding. Alcohols are a type of low-affinity drugs, and it remains unclear how water affects alcohol-protein interactions. Here, we present alcohol adsorption isotherms under controlled protein hydration using in-situ NMR detection. As functions of hydration level, Gibbs free energy, enthalpy, and entropy of binding were determined from the temperature dependence of isotherms. Two types of alcohol binding were found. The dominant type is low-affinity nonspecific binding, which is strongly dependent on temperature and the level of hydration. At low hydration levels, this nonspecific binding only occurs above a threshold of alcohol vapor pressure. An increased hydration level reduces this threshold, with it finally disappearing at a hydration level of h~0.2 (g water/g protein), gradually shifting alcohol binding from an entropy-driven to an enthalpy-driven process. Water at charged and polar groups on the protein surface was found to be particularly important in enabling this binding. Although further increase in hydration has smaller effects on the changes of binding enthalpy and entropy, it results in significant negative change in Gibbs free energy due to unmatched enthalpy-entropy compensation. These results show the crucial role of water-protein interplay in alcohol binding. PMID:25856773

  5. Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

    Energy Technology Data Exchange (ETDEWEB)

    K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

    2005-05-11

    The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

  6. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, July-September 1984

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1984-10-30

    Work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. Calorimetric measurements were made on pure quinoline. These measurements extended the range of previous measurements which had been made on quinoline, and improved the accuracy of previously measured results in the vapor phase when the quinoline sample used was believed to contain considerable quantities of water. 5 figures, 4 tables.

  7. Simulations of Nanocrystals Under Pressure: Combining Electronic Enthalpy and Linear-Scaling Density-Functional Theory

    OpenAIRE

    Corsini, NR; Greco, A.; Hine, ND; Molteni, C.; Haynes, PD

    2013-01-01

    We present an implementation in a linear-scaling density-functional theory code of an electronic enthalpy method, which has been found to be natural and efficient for the ab initio calculation of finite systems under hydrostatic pressure. Based on a definition of the system volume as that enclosed within an electronic density isosurface [M. Cococcioni, F. Mauri, G. Ceder, and N. Marzari, Phys. Rev. Lett. 94, 145501 (2005)], it supports both geometry optimizations and molecular dynamics simula...

  8. Dissolution enthalpies of L-proline and its interactions with methanol, 2-propanol, ethylene glycol, and glycerin in aqueous solution at 298.15 K

    Science.gov (United States)

    Korolev, V. P.; Antonova, O. A.; Smirnova, N. L.

    2010-12-01

    The dissolution enthalpies of L-proline in mixtures of water with methanol, 2-propanol, ethylene glycol, and glycerin were measured calorimetrically at 298.15 K. The enthalpy coefficients of the interaction of proline with alcohols in aqueous solutions were determined. The enthalpy coefficients of the pair interaction of proline and glycine with alcohols were shown to be directly proportional.

  9. Constant enthalpy change value during pyrophosphate hydrolysis within the physiological limits of NaCl.

    Science.gov (United States)

    Wakai, Satoshi; Kidokoro, Shun-ichi; Masaki, Kazuo; Nakasone, Kaoru; Sambongi, Yoshihiro

    2013-10-11

    A decrease in water activity was thought to result in smaller enthalpy change values during PPi hydrolysis, indicating the importance of solvation for the reaction. However, the physiological significance of this phenomenon is unknown. Here, we combined biochemistry and calorimetry to solve this problem using NaCl, a physiologically occurring water activity-reducing reagent. The pyrophosphatase activities of extremely halophilic Haloarcula japonica, which can grow at ∼4 M NaCl, and non-halophilic Escherichia coli and Saccharomyces cerevisiae were maximal at 2.0 and 0.1 M NaCl, respectively. Thus, halophilic and non-halophilic pyrophosphatases exhibit distinct maximal activities at different NaCl concentration ranges. Upon calorimetry, the same exothermic enthalpy change of -35 kJ/mol was obtained for the halophile and non-halophiles at 1.5-4.0 and 0.1-2.0 M NaCl, respectively. These results show that solvation changes caused by up to 4.0 M NaCl (water activity of ∼0.84) do not affect the enthalpy change in PPi hydrolysis. It has been postulated that PPi is an ATP analog, having a so-called high energy phosphate bond, and that the hydrolysis of both compounds is enthalpically driven. Therefore, our results indicate that the hydrolysis of high energy phosphate compounds, which are responsible for biological energy conversion, is enthalpically driven within the physiological limits of NaCl.

  10. Spatial variability of enthalpy in broiler house during the heating phase

    Directory of Open Access Journals (Sweden)

    Patrícia F. P. Ferraz

    2016-06-01

    Full Text Available ABSTRACT The thermal environment inside a broiler house has a great influence on animal welfare and productivity during the production phase. Enthalpy is a thermodynamic property that has been proposed to evaluate the internal broiler house environment, for being an indicator of the amount of energy contained in a mixture of water vapor and dry air. Therefore, this study aimed to characterize the spatial variability of enthalpy in a broiler house during the heating phase using geostatistics. The experiment was conducted in the spring season, in a commercial broiler house with heating system consisting of two furnaces that heat the air indirectly, in the first 14 days of the birds' life. It was possible to characterize enthalpy variability using geostatistical techniques, which allowed observing the spatial dependence through kriging maps. The analyses of the maps allowed observing problems in the heating system in regions inside the broiler house, which may cause a thermal discomfort to the animals besides productive and economic losses.

  11. Low-enthalpy geothermal resources for electricity production: A demand-side management study for intelligent communities

    DEFF Research Database (Denmark)

    Xydis, George A.; Nanaki, Evanthia A.; Koroneos, Christopher J.

    2013-01-01

    The geological conditions in Greece contributed to the creation of important low-enthalpy geothermal energy resources (LEGERs). The resources are divided into low, medium and high enthalpy, or temperature, based on criteria that are generally based on the energy content of the fluid. LEGERs...... are those sources of the hot water whose temperature is between 25 and 100°C, which are used for heating residences and in the agricultural or industrial sector. The investigation for the exploitation of low-enthalpy geothermal fluids, which began around 1980, intensified in the last two decades. The low......-enthalpy geothermal potential in Greece is rather significant as most of the geothermal fields have been found in regions with favourable developmental conditions, and it seems that they do not present serious environmental or technical exploitation problems. LEGER areas are abundant in Greece, mainly in the eastern...

  12. Computations of Separated High-Enthalpy Hypersonic Flows: Development of RANS and Variable-Resolution PANS Approaches Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose the development of a high fidelity computational approach for unsteady calculations of strongly separated non-equilibrium high-enthalpy hypersonic flows....

  13. Solvation enthalpy and the thermodynamics of hydration of trans-cyclohexyl-1,4-diamine and cis-cyclohexyl-1,2-diamine

    Energy Technology Data Exchange (ETDEWEB)

    Tome, Luciana I.N.; Jesus, A.J. Lopes [Department of Chemistry, Rua Larga 3004-535, University of Coimbra (Portugal); Esteves de Castro, R.A. [Faculty of Pharmacy, Rua do Norte 3000-295, University of Coimbra (Portugal); Teixeira, M. Helena S.F. [Department of Chemistry, Rua Larga 3004-535, University of Coimbra (Portugal); Canotilho, Joao [Faculty of Pharmacy, Rua do Norte 3000-295, University of Coimbra (Portugal); Eusebio, M. Ermelinda S. [Department of Chemistry, Rua Larga 3004-535, University of Coimbra (Portugal)], E-mail: quierme@ci.uc.pt

    2007-10-15

    The enthalpy of solution of trans-cyclohexyl-1,4-diamine and cis-cyclohexyl-1,2-diamine in water was determined by calorimetry. The enthalpy of hydration was determined from this quantity and from the enthalpy of sublimation/vaporization presented in another paper by the authors. Considering the solvation process resulting from cavity creation in the solvent and variation of solute conformation transfer steps, the enthalpy corresponding to solute-solvent interaction was estimated. The entropies of solvation and interaction were calculated from the values given for the enthalpies in the present paper and those available for the Gibbs free energies.

  14. ENTHALPY EU PROJECT: ENABLING THE DRYING PROCESS TO SAVE ENERGY AND WATER, REALISING PROCESS EFFICIENCY IN THE DAIRY CHAIN

    Directory of Open Access Journals (Sweden)

    Berta ALVAREZ PENEDO

    2016-11-01

    Full Text Available The EU funded ENTHALPY project aims to significantly reduce the consumption of water and energy in milk powder production to increase efficiency in the dairy production chain. Using a systematic approach, ENTHALPY project focusses on innovations within the post-harvest chain representing the highest energy and water consumption such as RF heating, solar thermal energy, mono-disperse atomising, dryer modelling, inline monitoring, enzymatic cleaning and membrane technology,

  15. Low enthalpy geothermal energy: borehole heat exchangers (BHE. Geological and geothermal supervision during active construction in support of the energy certification of buildings - ESBE certification plan

    Directory of Open Access Journals (Sweden)

    Lorenzo Cadrobbi

    2012-12-01

    Full Text Available This article draws on the experience matured while working with low-enthalpy geothermic installations both in the design and executive phase as well as ongoing monitoring, within the scope of energy conservation as it relates to building and construction. The goal is to illustrate the feasibility of adopting the ESBE certification protocol (Certification of Energy Efficient Low-Enthalpy Probes aimed at optimizing the harnessing of local geothermic resources to satisfy the energy requirements of a building, measured against the initial investment. It is often the case, in fact, that during the course of a construction project for a given low-enthalpy installation, we verify incompa tibilities with the local geologic and geothermic models, which, if inadequate during construction, can compromise the proper functioning of the installation and its subsequent operation. To this end, the ESBE method, which adheres to the governing environmental regulations, and which takes its cue from technical statutes within the sector, permits us to validate via verification, simulations and tests, the geothermic field probes used in construction in an objective and standardized manner, thereby joining and supporting the most recent protocols for energy certification of buildings (LEED 2010, CASACLIMA 2011, UE 20120/31 Directive. ESBE certification operates through a dedicated Certifying Entity represented by the REET unit (Renewable Energies and Environmental Technologies of FBK (Bruno Kessler Foundation of Trento. The results obtained by applying the ESBE method to two concrete cases, relative to two complex geothermic systems, demonstrate how this protocol is able to guarantee, beyond the correct execution in the field of geothermic probes, an effective coverage of the energy requirements of the building during construction adopting the best optimization measures for the probes in keeping with the local geological and geothermic model.

  16. Fiber optic sensors based on hybrid phenyl-silica xerogel films to detect n-hexane: determination of the isosteric enthalpy of adsorption.

    Science.gov (United States)

    Echeverría, Jesús C; Calleja, Ignacio; Moriones, Paula; Garrido, Julián J

    2017-01-01

    We investigated the response of three fiber optic sensing elements prepared at pH 10 from phenyltriethoxysilane (PhTEOS) and tetraethylsilane (TEOS) mixtures with 30, 40, and 50% PhTEOS in the silicon precursor mixture. The sensing elements are referred to as Ph30, Ph40 and Ph50, respectively. The films were synthesized by the sol-gel method and affixed to the end of optical fibers by the dip-coating technique. Fourier transform infrared spectroscopy, N2 adsorption-desorption at 77 K and X-ray diffraction analysis were used to characterize the xerogels. At a given pressure of n-hexane, the response of each sensing element decreased with temperature, indicating an exothermic process that confirmed the role of adsorption in the overall performance of the sensing elements. The isosteric adsorption enthalpies were obtained from the calibration curves at different temperatures. The magnitude of the isosteric enthalpy of n-hexane increased with the relative response and reached a plateau that stabilized at approximately -31 kJ mol-1 for Ph40 and Ph50 and at approximately -37 kJ mol-1 for Ph30. This indicates that the adsorbate-adsorbent interaction was dominant at lower relative pressure and condensation of the adsorbate on the mesopores was dominant at higher relative pressure.

  17. Entropy–enthalpy compensation as a fundamental concept and analysis tool for systematical experimental data

    KAUST Repository

    Starikov, E.B.

    2012-06-01

    Enthalpy-entropy compensation (EEC) has a definite physical sense. Here, we review EEC from a new standpoint, using the notion of correlation. The latter has two basic meanings: (a) \\'A\\' is correlated to \\'B\\' means \\'A\\' results from \\'B\\' or vice versa; (b) this same means there is some real, but hidden \\'C\\' in connection to both \\'A\\' and \\'B\\'). In accordance with the interpretation (b), we try rationalizing EEC in terms of hidden, but physically real factors. © 2012 Elsevier B.V. All rights reserved.

  18. Association constants and enthalpies of formation of heteroassociates of anions of cresol red and thymol blue

    Science.gov (United States)

    Shapovalov, S. A.

    2011-01-01

    The tendency of anions of sulfophthaleine dyes to heteroassociation was studied in aqueous solutions of phenol red, cresol red, thymol blue, and non-substituted phenol red. It was spectrophotometrically determined that single (HAn-) and doubly charged anions (An2-) of sulfophthaleines can form stable heteroassociates of the composition Ct+ · HAn- and (Ct+)2 · An2- with cations (Ct+) of polymethine dyes, pinacyanol, and quinaldine red. The values of enthalpy formation of ions of dyes and heteroassociates were calculated semi-empirically and compared with experimentally determined values of the equilibrium association constants.

  19. Free-flight measurement technique in the free-piston high-enthalpy shock tunnel

    Science.gov (United States)

    Tanno, H.; Komuro, T.; Sato, K.; Fujita, K.; Laurence, S. J.

    2014-04-01

    A novel multi-component force-measurement technique has been developed and implemented at the impulse facility JAXA-HIEST, in which the test model is completely unrestrained during the test and thus experiences free-flight conditions for a period on the order of milliseconds. Advantages over conventional free-flight techniques include the complete absence of aerodynamic interference from a model support system and less variation in model position and attitude during the test itself. A miniature on-board data recorder, which was a key technology for this technique, was also developed in order to acquire and store the measured data. The technique was demonstrated in a HIEST wind-tunnel test campaign in which three-component aerodynamic force measurement was performed on a blunted cone of length 316 mm, total mass 19.75 kg, and moment of inertia 0.152 kgm2. During the test campaign, axial force, normal forces, and pitching moment coefficients were obtained at angles of attack from 14° to 32° under two conditions: H0 = 4 MJ/kg, P0 = 14 MPa; and H0 = 16 MJ/kg, P0 = 16 MPa. For the first, low-enthalpy condition, the test flow was considered a perfect gas; measurements were thus directly compared with those obtained in a conventional blow-down wind tunnel (JAXA-HWT2) to evaluate the accuracy of the technique. The second test condition was a high-enthalpy condition in which 85% of the oxygen molecules were expected to be dissociated; high-temperature real-gas effects were therefore evaluated by comparison with results obtained in perfect-gas conditions. The precision of the present measurements was evaluated through an uncertainty analysis, which showed the aerodynamic coefficients in the HIEST low enthalpy test agreeing well with those of JAXA-HWT2. The pitching-moment coefficient, however, showed significant differences between low- and high-enthalpy tests. These differences are thought to result from high-temperature real-gas effects.

  20. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, January-March 1985

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1985-04-30

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the third quarter modifications to both the calorimeter and the phase equilibria system were completed. The phase equilibria system was checked out against literature data for methanol/ethanol. Results of these tests are included in this report. The calorimeter was evaluated using previously confirmed heptane data and published data by Thinh, et al. These results are also reported. Initial calorimetry data have been obtained for tetralin and the data will be reported when the data set has been completed. 5 refs., 5 figs., 3 tabs.

  1. Experimental determination of enthalpies of solution of tetraphenyl porphyrin (TPP) and some metal derivatives, in chloroform: interpretation of the solvation processes at a molecular level.

    Science.gov (United States)

    Gamboa, Minerva; Campos, Myriam; Torres, Luis Alfonso

    2010-01-18

    The enthalpies of solution, Delta(sol)H(m), for 5,10,15,20-tetraphenylporphine (CA registry number 917-23-7, TPP), 5,10,15,20-tetraphenylporphine of Co(II), Ni(II), Cu(II), and Zn(II) (to be written as CoTPP, NiTPP, CuTPP, and ZnTPP) in chloroform, were calorimetrically measured at T = 298 K in the concentration ranging from 3.5 x 10(-5) to 2.8 x 10(-4) mol.kg(-1). Through the linear extrapolation of the experimental data, corresponding values at infinite dilution were determined as: Delta(sol)H(m) (ZnTPP) = (55.5 +/- 0.2) kJ x mol(-1), Delta(sol)H(m) (CoTPP) = (36.9 +/- 0.2) kJ x mol(-1), Delta(sol)H(m) (TPP) = (25.7 +/- 0.6) kJ x mol(-1), Delta(sol)H(m) (NiTPP) = (15.6 +/- 0.1) kJ x mol(-1), and Delta(sol)H(m) (CuTPP) = (15.6 +/- 0.1) kJ x mol(-1). The enthalpies of solvation for the five compounds were also determined using the previously published values for the enthalpy of sublimation, as well as complementary data from the literature. The values obtained are as follows: Delta(solv)H(m)(TPP) = -(158.3 +/- 2.1) kJ x mol(-1), Delta(solv)H(m)(CoTPP) = -(154.1 +/- 2.0) kJ x mol(-1), Delta(solv)H(m)(CuTPP) = -(149.4 +/- 5.0) kJ x mol(-1) Delta(solv)H(m)(NiTPP) = -(141.4 +/- 4.0) kJ x mol(-1), and Delta(solv)H(m)(ZnTPP) = -(140.5 +/- 3.0) kJ x mol(-1). The results are analyzed in relation to several molecular properties such as ionic radius, electronic spectra, and Connolly surface. An explanation of the observed trends for solvation enthalpies is proposed.

  2. Vapor pressures and sublimation enthalpies of seven heteroatomic aromatic hydrocarbons measured using the Knudsen effusion technique

    Energy Technology Data Exchange (ETDEWEB)

    Goldfarb, Jillian L., E-mail: JillianLGoldfarb@gmail.co [Division of Engineering, Brown University, Providence, RI 02912 (United States); Suuberg, Eric M., E-mail: Eric_Suuberg@brown.ed [Division of Engineering, Brown University, Providence, RI 02912 (United States)

    2010-06-15

    The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) g . mol{sup -1} were measured over the temperature range of (301 to 486) K using the isothermal Knudsen effusion technique. The compounds measured include: anthraquinone, 9-fluorenone, 9-fluorenone oxime, phenoxazine, phenoxathiin, and 9H-pyrido[3,4-b]indole. These solid-state sublimation measurements provided values that are compared to vapor pressures of parent aromatic compounds (anthracene and fluorene) and to others with substituent groups in order to examine the effects of alcohol, ketone, pyridine, and pyrrole functionality on this property. The enthalpies and entropies of sublimation for each compound were determined from the Clausius-Clapeyron equation. Though there is no consistent trend in terms of the effects of substitutions on changes in the enthalpy or entropy of sublimation, we note that the prevalence of enthalpic or entropic driving forces on vapor pressure depend on molecule-specific factors and not merely molecular weight of the substituents.

  3. Hydrate thermal dissociation behavior and dissociation enthalpies in methane-carbon dioxide swapping process

    DEFF Research Database (Denmark)

    Mu, Liang; von Solms, Nicolas

    2018-01-01

    The swapping of methane with carbon dioxide in hydrate has been proposed as a potential strategy for geologic sequestration of carbon dioxide and production of methane from natural hydrate deposits. However, this strategy requires a better understanding of the thermodynamic characteristics of CH4...... and CO2 hydrate as well as (CH4 + CO2) or (CH4 + CO2 + N2) mixed hydrates (since (CO2 + N2) gas mixture is often used as the swapping gas), along with the thermal physics property changes during gas exchange. In this study, a high pressure micro-differential scanning calorimetry (HP μ-DSC) was performed...... on synthesized gas hydrates to investigate the dissociation behavior of various hydrates. The hydrate dissociation enthalpies were determined by both μ-DSC measurement and Clapeyron equation. For the single guest molecule hydrate system, the average dissociation enthalpies of CH4 hydrate and CO2 hydrate measured...

  4. Oil presence in an evaporator: experimental validation of a refrigerant/oil mixture enthalpy calculation model

    Energy Technology Data Exchange (ETDEWEB)

    Youbi-Idrissi, M.; Bonjour, J.; Terrier, M.-F.; Meunier, F. [Laboratoire du Froid, Paris Cedex (France); Marvillet, C. [GRETh, CEA Grenoble (France)

    2004-05-01

    In this paper, the impact of the oil presence on the performance of a refrigerating machine is investigated both experimentally and numerically. To highlight the effect of oil, particularly on the evaporator behaviour, a theoretical model of enthalpy calculation for a refrigerant/oil mixture has been previously developed [Int J Refrigeration, 26(2003), 284]. In order to validate this model, tests were carried out on an industrial refrigerating machine working with R-407C. The lubricant is a polyol-ester oil whose solubility curves are given by the oil manufacturer. The oil circulating mass fraction is measured by a sampling technique and by an on-line density measurement method, whose advantages and drawbacks are presented. Both the model and the experiments show that the ratio of enthalpy change through the evaporator with to without the oil presence increases when the apparent superheat at the evaporator outlet increases. This is due to the presence of a non-evaporated amount of liquid refrigerant dissolved in the oil at this location, which is confirmed by visual observations. The numerical and experimental results are found to be in a good agreement as the maximum deviation is about 2.2%. (author)

  5. High precision calorimetry to determine the enthalpy of combustion of methane

    Energy Technology Data Exchange (ETDEWEB)

    Dale, Andrew; Lythall, Christopher; Aucott, John; Sayer, Courtnay [Office of Gas and Electricity Markets, Technical Directorate, 3 Tigers Road, South Wigston, LE18 4UX Leicester (United Kingdom)

    2002-01-31

    The enthalpy of combustion of methane is the most important property used in the determination of the calorific value of natural gas. Only two sets of values with high accuracy and precision and measured under appropriate conditions have been published since it was first determined in 1848. These studies were done by Rossini, at the National Bureau of Standards in the USA in 1931, and Pittam and Pilcher, at the University of Manchester in 1972. This report details the design and operation of a high precision constant-pressure gas burning calorimeter, based on the design of those used in the previous studies, to measure the superior enthalpy of combustion of ultra-high purity methane at 25C.The use of modern equipment and automatic data collection leads to a value, traceable to national standards, of 890.61kJmol{sup -1} with a combined standard uncertainty of 0.21kJmol{sup -1}. This is in full accord with the value of 890.63kJmol{sup -1} calculated from the average of Rossini's and Pittam and Pilcher's work (with a random uncertainty based on 1 S.D. of 0.53kJmol{sup -1})

  6. Adsorption sites, adsorption enthalpies and potential removal of terpenoids by atmospheric ice

    Science.gov (United States)

    Czech, Christian; Hammer, Sonja M.; Bonn, Boris; Schmidt, Martin U.

    2011-01-01

    Ice crystal formation and its effect on atmospheric trace gases are currently an important area of research because of its radiation and climate effects. However, the processes of adsorption of trace gases on ice surfaces and absorption into ice crystals are poorly understood. Both processes are investigated by lattice-energy minimisation for a selected number of atmospherically relevant volatile organic compounds, i.e. isoprene, methacrolein, acetone, methylbutenol, perillyl alcohol and 2,10-pinanediol, which can be considered as exemplary substances for similar structured compounds. Adsorption and absorption geometries and enthalpies are computed and the potential uptake strength is approximated. According to our calculations non-polar terpenes like isoprene are not significantly adsorbed by ice crystals. Oxidized terpenoids have stronger interactions with the ice surface (at least two hydrogen bonds) leading to larger adsorption enthalpies. Absorption into the ice crystal plays only a minor role. Correspondingly, in the atmosphere terpenoid compounds are increasingly adsorbed to ice surfaces with increasing oxygen numbers. Subsequently this process can contribute to the wet removal of terpenoids by ice, which is so far ignored in global transport models.

  7. Enthalpy measurement of coal-derived liquids. Technical progress report, August-October 1982

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1982-11-30

    The correlational effort on the coal syncrudes and model compounds has been proceeding along two fronts. The first involves experimental work on a correlating factor for association in the liquids and the second involves an investigation of the modeling capabilities of cubic equations of state. The first area of investigation is the experimental measurement of a correlating factor for assocition in coal liquids. The procedure involves molecular weight measurement by freezing point depression. To facilitate these measurements, a simple Beckman freezing point depression apparatus is being currently modified to increase the accuracy, speed, and ease of measurement. The second area of effort has involved establishing a set of cubic equations of state which can adequately model the enthalpy departures of quinoline and m-cresol. To this effort, a number of standard and association specific equations of state have been tested against a data base of previously measured enthalpy departures of m-cresol and quinoline. It has been found that these equations do quantitatively a poor job on m-cresol and quinoline. These problems are probably due to the highly polar nature of m-cresol and to a lesser extent quinoline, and to the poor quality of critical parameters for quinoline.

  8. Enthalpy and phase behavior of coal derived liquid mixtures. Technical progress report, October-December 1984

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1985-01-31

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the second quarter efforts were limited to ordering and installing equipment to improve the operability of the calorimeter and phase behavior system. The program is now up to full staffing levels and data collection will begin this next quarter. The objectives of this program are to study the enthalpy and phase behavior of a selected ternary model compound system, representative of interactions present in coal derived liquids. Measurements will be made in a Freon 11 reference fluid boil off calorimeter, and an equilibrium flash vaporization apparatus. These experimental systems have already been developed. Previous studies have indicated that existing data and correlations developed for petroleum fluids are not applicable to coal derived liquids. This is due to the presence of significant concentrations of polar associating heteroatomics in the predominantly aromatic coal liquids. Thus, the ternary system will include an aromatic, a basic nitrogen compound, and a cresol. It is presently planned to study the tetralin/quinoline/m-cresol ternary mixture. Measurements will be made over a wide range of temperature (200 to 700/sup 0/C) and pressure (20 to 1500 psia), for the three pure compounds.

  9. The available-enthalpy (flow-exergy) cycle. Part-II: applications to idealized baroclinic waves

    CERN Document Server

    Marquet, Pascal

    2014-01-01

    The local available-enthalpy cycle proposed in Part I of this paper is applied to document energetics of three numerical simulations, representing life cycles of idealized baroclinic waves. An improved temporal numerical scheme defined in Part I is used in this study, together with the Arpege-IFS model using a T42 triangular truncation. A 45{\\deg}N and 200 hPa dry unstable jet is constructed with the most unstable mode at zonal wave number 8. Energetic impacts of both horizontal and vertical diffusion schemes are determined separately. The role of ageostrophic winds within the Ekman layer is investigated, leading to an explanation for large observed values for the dissipation terms and to a new formulation of the potential-energy conversions. The magnitudes of these new conversion terms are compared with those of the usual barotropic and baroclinic conversions. A new version for the available-enthalpy cycle is proposed. It is suitable for open systems and it includes explicitly the potential-energy component ...

  10. Fixed-bed drying simulation with constant enthalpy, using the improved Michigan State University model - doi: 10.4025/actascitechnol.v34i2.7812

    Directory of Open Access Journals (Sweden)

    Valdecir Antoninho Dalpasquale

    2012-03-01

    Full Text Available Drying of agricultural products at high temperatures can be simulated by mathematical models, which intend to describe the drying process close to commercial patterns. They are based on simultaneous heat and mass transfer between the product that is losing moisture, and the air that is supplying energy to the process. All models use these balances, never allowing values of relative humidity of the air to be greater than 100%. However, it has not been common to evaluate air enthalpy, which should not have significant variation during the entire process, accepted as adiabatic. In this work, a mathematical model is proposed for fixed-bed corn (Zea mays L. drying simulation, according to the Michigan State University (MSU model. In the numerical solution, the enthalpy of the drying air was maintained constant as a quantitative physical indicator for correction of the heat and mass exchange in each step of the process, in order to obtain more real evaluations in all drying stages, and in the results for final moisture of the grain. As a result, greater space and time intervals for the simulation were possible. The simulation was validated by comparisons with literature results.  

  11. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, July-September, 1978. [148 to 459/sup 0/F; 100 to 300 psia

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1978-12-01

    Experimental measurements were completed on a naphtha sample (1046) furnished by the Pittsburg and Midway Coal Mining Company. A total of 38 measurements were made in the temperature region 148 to 459/sup 0/F, and at pressures of 100 and 300 psia. Additional analytical work was also completed on the SRC-I naphtha whose enthalpy measurements were reported in previous progress reports. Comparisons are given between the experimental SRC-I naphtha enthalpies and the available petroleum enthalpy correlations.

  12. Enthalpies of the reaction of N-methylpyrrolidone with C/sub 9/-C/sub 12/ arenes

    Energy Technology Data Exchange (ETDEWEB)

    Yanbukhtina, R.A.; Gaile, A.A.; Semenov, L.V.

    1988-07-20

    Mixing of N-methylpyrrolidone with monocycloaromatic hydrocarbons takes place with an endothermic effect and mixing with bicycloaromatic hydrocarbons occurs with an exothermic effect. This is due to an increase in the proportion of the specific reaction in going from systems with mono- and bicycloaromatic hydrocarbons from 30 to 50-60% of the total enthalpy of the reaction. The enthalpies of the specific reaction of arenes with N-methylpyrrolidone are correlated with the donor numbers of the hydrocarbons. The difference in the enthalpies of solvation of saturated and aromatic hydrocarbons by N-methylpyrrolidone is greater than with dimethylformamide and furfural, which is in agreement with the higher selectivity of N-methylpyrrolidone.

  13. Enthalpies of solution of tetramethyl-bis-urea (Mebicarum) in amides and acetone at 298.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Evgeniy V. [Laboratory of Thermodynamics of Solutions of Non-electrolytes and Biologically Active Substances, Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Str., 153045 Ivanovo (Russian Federation)], E-mail: evi@isc-ras.ru; Abrosimov, Vladimir K.; Smirnov, Valeriy I. [Laboratory of Thermodynamics of Solutions of Non-electrolytes and Biologically Active Substances, Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Str., 153045 Ivanovo (Russian Federation)

    2007-10-25

    The enthalpies of solution of 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione or tetramethyl-bis-urea (the drug Mebicarum) in formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N,N',N'-tetramethylurea, and acetone were measured at 298.15 K. Standard enthalpies of solution and transfer from one solvent to another were computed. The enthalpies of solution of the solute were found to be endothermic and weak depending on the nature of methylation in an amide molecule. It was concluded that the solvent proton-donor ability and existing steric hindrances for H-bonding and other interparticle interactions play the key role in solvation of tetramethyl-bis-urea.

  14. Enthalpy and phase behavior of coal derived liquid mixtures: Technical progress report for the period July-September 1987

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1987-10-31

    The objectives of this program are to study the enthalpy and phase behavior of a selected ternary model compound system, representative of interactions present in coal derived liquids. Measurements were made in a Freon 11 reference fluid boil-off calorimeter, and an equilibrium flash vaporization apparatus. The ternary system included an aromatic, a basic nitrogen compound, and a cresol: the m-cresol/quinoline/tetralin ternary mixture. Measurements were made over a wide range of temperature (200 to 750/sup 0/F) and pressure (20 to 1500 psia), for the three pure compounds, the three binary mixtures and selected compositions of the ternary. Both enthalpy and phase behavior measurements were made. Equation of state parameters obtained from binary enthalpy data are more reliable when extrapolated to the ternary system, than parameters obtained from vapor liquid equilibrium data. Furthermore, the more complex mixing rules generally gave poorer predictions when extrapolated to ternary systems. 17 refs., 7 figs., 4 tabs.

  15. Extremes temperatures and enthalpy in Finland and Sweden in a changing climate

    Energy Technology Data Exchange (ETDEWEB)

    Venaelaeinen, A.; Saku, S.; Jylhae, K. (Finnish Meteorological Institute (Finland)); Nikulin, G.; Kjellstroem, E.; Baerring, L. (Swedish Meteorological Institute (Sweden))

    2009-06-15

    Though risks caused by harsh weather conditions are taken into account in the planning of nuclear power plants, some exceptional weather events or combination of different events may prevent normal power operation and simultaneously endanger safe shutdown of the plant. Extreme weather events could influence, for example, the external power grid connection, emergency diesel generators (blockage of air intakes), ventilation and cooling of electric and electronics equipment rooms and the seawater intake. Due to the influence of an intensified greenhouse effect the climate is changing rapidly during the coming decades and this change is expected to have an influence also on the occurrence of extreme weather events. In this report we have examined extreme temperatures. Enthalpy is a parameter that combines air temperature and air humidity and it is used in the design of air conditioning systems. Therefore, we have included also return levels of enthalpy in our analysis. The influence of climate change on extreme temperatures is analysed based on regional climate model simulations. The reoccurrence times of high temperatures combined with high air humidity was analysed based on measurements made at five Finnish and three Swedish meteorological stations. Based on the observational records we find the 10 year return level of daily maximum temperature to be around 32 deg. C and the 100 year return level around 35 deg. C. If we look the return levels of warm and humid conditions then for example in Helsinki the 10 year return level of one week mean temperature in case mean air humidity is above 80% is 20.1 deg. C. The 10 year return level of daily maximum enthalpy is around 60 kJ/kg and the 100 year return level almost 70 kJ/kg. According to the climate model simulations the largest increase of 50-year return level of daily maximum temperature is found in southern Sweden and south-western Finland. By the end of this century the increase can be 3-5 deg. C. The largest change

  16. Calorimetric determination of enthalpy changes for the proton ionization of 3-[N-morpholino]propanesulfonic acid (MOPS), 4-[N-morpholino]butanesulfonic acid (MOBS) and 3-[N-morpholino]-2-hydroxypropanesulfonic acid (MOPSO) in water-methanol mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Jumean, F.H., E-mail: fjumean@aus.edu [Department of Biology, Chemistry and Environmental Sciences, American University of Sharjah, POB 26666, Sharjah (United Arab Emirates); Abdo, N.M. [Department of Biology, Chemistry and Environmental Sciences, American University of Sharjah, POB 26666, Sharjah (United Arab Emirates); Khamis, M.I. [Department of Chemistry and Chemical Technology, Al-Quds University, Jerusalem, Palestine (Country Unknown)

    2011-09-20

    Highlights: {yields} Two-stage proton ionizations for three N-substituted sulfonic acid derivatives of morpholine. {yields} {Delta}H{sub 1} and {Delta}H{sub 2} in x{sub methanol} = 0-0.360 measured for MOPS, MOBS and MOPSO. {yields} In water, {Delta}H{sub 1} = {+-}1.2 kJ mol{sup -1}, {Delta}H{sub 2} range 20.7-26.3 kJ mol{sup -1}. {yields} Methanol addition had little effect on {Delta}H{sub 1} but {Delta}H{sub 2} rose steadily to 32.2 kJ mol{sup -1}. {yields} Results related to molecular and solvent parameters. - Abstract: Proton ionization enthalpies for three structurally related biological buffers, each with two ionizable protons, were determined using solution calorimetry. These buffers are 3-[N-morpholino]propanesulfonic acid (MOPS), 4-[N-morpholino]butanesulfonic acid (MOBS) and 3-[N-morpholino]-2-hydroxypropanesulfonic acid (MOPSO). Enthalpies were obtained in water-methanol mixtures with methanol mole fraction (X{sub m}) from 0 to 0.360. The first ionization enthalpy ({Delta}H{sub 1}) of all buffers was small ({+-}1.2 kJ mol{sup -1}) at all solvent compositions. The second ionization enthalpy ({Delta}H{sub 2}) increased steadily with X{sub m}, rising from 20.7 to 25.6 kJ mol{sup -1} for MOPS, 26.3-31.0 kJ mol{sup -1} for MOBS and 23.5-32.2 kJ mol{sup -1} for MOPSO. The results were compared to those for related biological buffers. The observed variations were interpreted in terms of solvent-solvent and solvent-solute interactions.

  17. Enthalpy measurement of coal-derived liquids. Combined quarterly technical progress reports, April-June 1979 and July-September 1979. [Effect of association

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1979-01-01

    Enthalpy measurements on a coal-derived naphtha and middle distillate, both produced by the SRC-II process, were made using flow calorimetry. The accuracy of the measurements, as reported by Omid, was within +- 1% of the measured enthalpy differences, ..delta..H. Experimental data for the naphtha were obtained over a pressure range of 100-300 psia and temperatures from 148/sup 0/ to 456/sup 0/F. The middle distillate enthalpy measurements were made in the pressure and temperature ranges of 130 to 1000 psia, and 157/sup 0/ to 675/sup 0/F, respectively. The methods of prediction of enthalpy developed for petroleum fractions were unsatisfactory when applied to the above data. A negative bias was observed in the predicted enthalpy values for several of the coal-liquids. Based on these results, it was theorized that the high experimental enthalpy values for coal-liquids were due to an energy of association attributed, primarily, to hydrogen-bonding effects. The petroleum-fraction enthalpy correlations were then tested on the experimental data for pure compounds, both associating and non-associating. The predicted values compared very well with the experimental results for non-associating model compounds. However, for associating model compounds the predicted enthalpy values were considerably lower than their experimental data. This served to confirm the basic premise that the high experimental enthalpy values, for model compounds and coal liquids, were a direct consequence of an energy of association attributed, primarily, to hydrogen-bonding effects.

  18. Direct determination of the enthalpy of formation of MoB in synthesis from simple substances in an SHS system

    Science.gov (United States)

    Lavut, E. G.; Chelovskaya, N. V.; Kashireninov, O. E.

    1993-10-01

    In a calorimetric bomb equipped with an electric microfurnace for heating a sample, self-propagating high-temperature synthesis (SHS) of molybdenum boride is realized in accordance with the reaction Mo (c) +B (amorph.)=MoB (c); the enthalpy of this reaction is measured, and the standard enthalpy of formation of molybdenum boride from metal molybdenum and crystaline boron is calculated: Δf H 0 (MoB,c,δ,β)=103.9α1.2kJ/mole.

  19. Enthalpy and phase behavior of coal derived liquid mixtures. Ninth quarterly technical progress report, July-September 1986

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1986-10-31

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid moedl compound mixtures. During the ninth quarter, enthalpy measurements on the pure component 1-methylnaphthalene were obtained. Also, during this quarter ternary vapor liquid equilibrium measurements for m-cresol/quinoline/tetralin have begun for the isotherms; 250, 275, 300, 325/sup 0/C. A maximum likelihood algorithm applicable for implicit constraints has been developed. The method was applied to the determination of interaction parameters for temperature and density dependent mixing rules from our binary vapor liquid equilibrium data. 16 refs., 51 figs., 14 tabs.

  20. A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems

    DEFF Research Database (Denmark)

    krabbenhøft, Kristian; Damkilde, Lars

    2003-01-01

    In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground ...... freezing and solar energy storage. The phase-change problem is characterized by an abrupt change in enthalpy per unit temperature in a narrow temperature range around the freezing point.......In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground...

  1. Sub-Tg enthalpy relaxation in an unstable oxide glass former: insights into the structural heterogeneity

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Zhang, Yanfei

    Structural heterogeneity plays a crucial role in determining functionality of glasses. In this work we have found that the sub-Tg enthalpy relaxation pattern in a hyperquenched glass is highly sensitive to structural heterogeneity. As a consequence, the former can be used as an effective approach...... we chose the glass compositions with very different glass stabilities to crystallization. By using hyperquenching-annealing-calorimetry approach, we have observed that the pattern of calorimetric response below Tg dramatically varies with glass composition. The variations are attributed to different...... to detect and quantify the structural heterogeneity in glass-forming liquids. However, the chemical nature of structural heterogeneity should be revealed by other means such as high resolution microscopic and spectroscopic methods. To study the impact of the structural heterogeneity on the sub-Tg relaxation...

  2. Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets

    Science.gov (United States)

    Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

    2013-01-01

    Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

  3. Measurements and analysis of excess enthalpies of ester + n-alkane using the UNIFAC model

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, J. (Escuela Superior de Ingenieros Industriales, Las Palmas (Spain). Catedra de Termodinamica y Fisicoquimica); Legido, J.L.; Fernandez, J.; Pias, L.; Paz Andrade, M.I. (Universidad de Santiago de Compostela (Spain). Dept. de Fisica Aplicada)

    1991-02-01

    We present new experimental data of the excess molar enthalpies at 298.15 K for eighteen different binary mixtures of nine methyl alkanoates (ethanoate to decanoate) with n-heptane and n-undecane. The results show that all the systems are endothermic, h{sup E} values increase with the length of the n-alkane and decrease with the length of the methyl ester. The data have been analysed with a version of the UNIFAC model, and the parameters corresponding to the CH{sub 2}/COOC interaction have been recalculated using a larger base of experimental data. New values for the CH{sub 2}/COO interaction parameters have been obtained. (orig.).

  4. Communication: Enthalpy relaxation in a metal-organic zeolite imidazole framework (ZIF-4) glass-former

    Science.gov (United States)

    Xu, Di; Liu, Yingdan; Tian, Yongjun; Wang, Li-Min

    2017-03-01

    Amorphization in metal-organic framework materials initiated by the collapsed crystal offers new access to glasses; however, the understanding of such glasses remains to be clarified. Here, we studied the glass transition thermodynamics and kinetics in a zeolitic imidazolate framework ZIF-4 utilizing enthalpy relaxation measurements. The calorimetric glass transition profile and relaxation behaviors in ZIF-4 are found to reproduce the basic features and correlations manifested by conventional melt-quenched glasses. A comparison with various melt-quenched glasses suggests that the low fragility of ZIF-4 is ascribed to the low thermal-pressure coefficient due to the directional tetrahedral bond, partly leading to the low vibrational entropy in the melt-crystal entropy difference.

  5. Enthalpy Relaxation of a DGEBA Epoxy as a function of Time, Temperature, and Cooling Rate

    Science.gov (United States)

    Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.

    2015-03-01

    Enthalpy relaxation resulting from physical aging of a DGEBA epoxy, Epon 828, cross-linked with an amine curative, Jeffamine T-403, was studied for two isothermal aging temperatures at sequential aging times up to two weeks. Results were analyzed using the peak shift method to obtain the relaxation parameters β, δ (H*), and χ. The individual effects of cooling rate from the equilibrated state, aging time, and aging temperature were isolated to understand the initial state of the glassy epoxy and its evolution during physical aging. [Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  6. Experimental study on mass transfer of contaminants through an enthalpy recovery unit with polymer membrane foils

    DEFF Research Database (Denmark)

    Nie, Jinzhe; Fang, Lei

    2014-01-01

    recovery unit with polymer membrane foils was used as refeering unit in this study. The experiments were conducted with different outdoor thermal climates e.g. warm-humid and cold-dry climates; isothermal and non isothermal as well as equal humidity and non equal humidity with indoor climate. Three......Laboratory experimental studies were conducted to investigate the mass transfer of contaminants through a total heat recovery unit with polymer membranes foils. The studies were conducted in twin climate chambers which simulated outdoor and indoor thermal climates. One manufacturd total heat...... could transfer from exhaust air to supply air through the enthalpy recovery unit. The mass transfer efficiency of contaminants was independent of the hygro-thermal differences between indoor and outdoor climate conditions. The mass transfer ratio of the chemical contaminants in the total heat recovery...

  7. New estimators for calculating solvation entropy and enthalpy and comparative assessments of their accuracy and precision.

    Science.gov (United States)

    Wyczalkowski, Matthew A; Vitalis, Andreas; Pappu, Rohit V

    2010-06-24

    We present two new methods for estimating the entropy and enthalpy decomposition of free energy calculations. These methods are based on temperature derivatives of the Bennett Acceptance Ratio and the Multistate Bennett Acceptance Ratio estimators, respectively. We test the accuracy of these new estimators using a simple one-dimensional model. A detailed assessment of their performance is reported by studying the solvation of N-methylacetamide. Finally, we quantify the free energies of solvation for 11 model compounds using the OPLS-AA force field and a variation of this force field. Thermodynamic decompositions of these calculated free energies are obtained to highlight the utility of these quantities for refining force field parameters by comparing computed free energies and their decompositions to their experimental counterparts.

  8. Enthalpy measurements of a syncrude and a distillate derived from Western Kentucky coal

    Energy Technology Data Exchange (ETDEWEB)

    Omid, H.; Andrew, J.R.; Kidnay, A.J.; Yesavage, V.F.

    1984-04-01

    Enthalpy data at pressures of 690, 3450, 6895, and 10340 kPa (100, 500, 1000, 1500 psia) for temperatures between 18.3 and 375/sup 0/C (65 to 705/sup 0/F) are presented for a Western Kentucky syncrude produced by the Char-Oil-Energy-Development (COED) process, and for a combined distillate of the Western Kentucky syncrude for pressures of 690, 3450, and 6895 kPa (60, 100, 500 psia) and temperatures between 18.3 and 402/sup 0/C (65 to 765/sup 0/F). The data were obtained in a boil-off calorimeter with Freon 11 (CFCl/sub 3/) as a reference fluid.

  9. Measuring Enthalpy of Sublimation of Volatiles by Means of Piezoelectric Crystal Microbalances

    Science.gov (United States)

    Dirri, Fabrizio; Palomba, Ernesto; Longobardo, Andrea; Zampetti, Emiliano

    2017-12-01

    Piezoelectric Crystal Microbalances (PCM's) are widely used to study the chemical processes involving volatile compounds in any environment, such as condensation process. Since PCM's are miniaturized sensor, they are very suitable for planetary in situ missions, where can be used to detect and to measure the mass amount of astrobiologically significant compounds, such as water and organics. This work focuses on the realization and testing of a new experimental setup, able to characterize volatiles which can be found in a planetary environment. In particular the enthalpy of sublimation of some dicarboxylic acids has been measured. The importance of dicarboxylic acids in planetology and astrobiology is due to the fact that they have been detected in carbonaceous chondritic material (e.g. Murchinson), among the most pristine material present in our Solar System. In this work, a sample of acid was heated in an effusion cell up to its sublimation. For a set of temperatures (from 30 °C to 75 °C), the deposition rate on the PCM surface has been measured. From these measurements, it has been possible to infer the enthalpy of sublimation of Adipic acid, i.e. ΔH = 141.6 ± 0.8 kJ/mol and Succinic acid, i.e. ΔH = 113.3 ± 1.3 kJ/mol. This technique has so demonstrated to be a good choice to recognise a single compound or a mixture (with an analysis upstream) even if some improvements concerning the thermal stabilization of the system will be implemented in order to enhance the results' accuracy. The experiment has been performed in support of the VISTA (Volatile In Situ Thermogravimetry Analyzer) project, which is included in the scientific payload of the ESA MarcoPolo-R mission study.

  10. An evaluation for harnessing low-enthalpy geothermal energy in the Limpopo Province, South Africa

    Directory of Open Access Journals (Sweden)

    Taufeeq Dhansay

    2014-03-01

    Full Text Available South Africa generates most of its energy requirements from coal, and is now the leading carbon emitter in Africa, and has one of the highest rates of emissions of all nations in the world. In an attempt to decrease its CO2 emissions, South Africa continues to research and develop alternative forms of energy, expand on the development of nuclear and has began to explore potentially vast shale gas reserves. In this mix, geothermal has not been considered to date as an alternative energy source. This omission appears to stem largely from the popular belief that South Africa is tectonically too stable. In this study, we investigated low-enthalpy geothermal energy from one of a number of anomalously elevated heat flow regions in South Africa. Here, we consider a 75-MW enhanced geothermal systems plant in the Limpopo Province, sustainable over a 30-year period. All parameters were inculcated within a levelised cost of electricity model that calculates the single unit cost of electricity and tests its viability and potential impact toward South Africa's future energy security and CO2 reduction. The cost of electricity produced is estimated at 14 USc/KWh, almost double that of coal-generated energy. However, a USD25/MWh renewable energy tax incentive has the potential of making enhanced geothermal systems comparable with other renewable energy sources. It also has the potential of CO2 mitigation by up to 1.5 gCO2/KWh. Considering the aggressive nature of the global climate change combat and South Africa's need for a larger renewable energy base, low-enthalpy geothermal energy could potentially form another energy option in South Africa's alternative energy basket.

  11. Evaluation of the ground surface Enthalpy balance from bedrock temperatures (Livingston Island, Maritime Antarctic

    Directory of Open Access Journals (Sweden)

    M. Ramos

    2009-05-01

    Full Text Available The annual evolution of the ground temperatures from Incinerador borehole in Livingston Island (South Shetlands, Antarctic is studied. The borehole is 2.4 m deep and is located in a massive quartzite outcrop with negligible water content, in the proximity of the Spanish Antarctic Station Juan Carlos I. In order to model the movement of the 0°C isotherm (velocity and maximum depth hourly temperature profiles from: (i the cooling periods of the frost season of 2000 to 2005, and (ii the warming periods of the thaw season of 2002–2003, 2003–2004 and 2004–2005, were studied. In this modelling approach, heat gains and losses across the ground surface are assumed to be the causes for the 0°C isotherm movement. A methodological approach to calculate the ground Enthalpy change based on the thermodynamic analysis of the ground during the cooling and warming periods is proposed. The Enthalpy change into the rock is equivalent to the heat exchange through the ground surface during each season, thus enabling to describe the interaction ground-atmosphere and providing valuable data for studies on permafrost and periglacial processes. The bedrock density and thermal conductivity are considered to be constant and initial isothermal conditions at 0°C are assumed (based in collected data and local meteorological conditions in this area to run the model in the beginning of each season. The final stages correspond to the temperatures at the end of the cooling and warming periods (annual minima and maxima. The application of this method avoids error propagation induced by the heat exchange calculations from multiple sensors using the Fourier method.

  12. Enthalpy-Driven RNA Folding: Single-Molecule Thermodynamics of Tetraloop–Receptor Tertiary Interaction†

    Science.gov (United States)

    Fiore, Julie L.; Kraemer, Benedikt; Koberling, Felix; Edmann, Rainer; Nesbitt, David J.

    2010-01-01

    RNA folding thermodynamics are crucial for structure prediction, which requires characterization of both enthalpic and entropic contributions of tertiary motifs to conformational stability. We explore the temperature dependence of RNA folding due to the ubiquitous GAAA tetraloop–receptor docking interaction, exploiting immobilized and freely diffusing single-molecule fluorescence resonance energy transfer (smFRET) methods. The equilibrium constant for intramolecular docking is obtained as a function of temperature (T = 21–47 °C), from which a van’t Hoff analysis yields the enthalpy (ΔH°) and entropy (ΔS°) of docking. Tetraloop–receptor docking is significantly exothermic and entropically unfavorable in 1 mM MgCl2 and 100 mM NaCl, with excellent agreement between immobilized (ΔH° = −17.4 ± 1.6 kcal/mol, and ΔS° = −56.2 ± 5.4 cal mol−1 K−1) and freely diffusing (ΔH° = −17.2 ± 1.6 kcal/mol, and ΔS° = −55.9 ± 5.2 cal mol−1 K−1) species. Kinetic heterogeneity in the tetraloop–receptor construct is unaffected over the temperature range investigated, indicating a large energy barrier for interconversion between the actively docking and nondocking subpopulations. Formation of the tetraloop–receptor interaction can account for ~60% of the ΔH° and ΔS° of P4–P6 domain folding in the Tetrahymena ribozyme, suggesting that it may act as a thermodynamic clamp for the domain. Comparison of the isolated tetraloop–receptor and other tertiary folding thermodynamics supports a theme that enthalpy- versus entropy-driven folding is determined by the number of hydrogen bonding and base stacking interactions. PMID:19186984

  13. Thermochemical properties and bond dissociation enthalpies of 3- to 5-member ring cyclic ether hydroperoxides, alcohols, and peroxy radicals: cyclic ether radical + (3)O(2) reaction thermochemistry.

    Science.gov (United States)

    Auzmendi-Murua, Itsaso; Bozzelli, Joseph W

    2014-05-01

    The formation of cyclic ethers is a major product in the oxidation of hydrocarbons, and the oxidation of biomass derived alcohols. Cyclic ethers are formed in the initial reactions of alkyl radicals with dioxygen in combustion and precombustion processes that occur at moderate temperatures. They represent a significant part of the oxygenated pollutants found in the exhaust gases of engines. Cyclic ethers can also be formed from atmospheric reactions of olefins. Additionally, cyclic ethers have been linked to the formation of the secondary organic aerosol (SOA) in the atmosphere. In combustion and thermal oxidation processes these cyclic ethers will form radicals that react with (3)O2 to form peroxy radicals. Density functional theory and higher level ab initio calculations are used to calculate thermochemical properties and bond dissociation enthalpies of 3 to 5 member ring cyclic ethers (oxirane, yC2O, oxetane, yC3O, and oxolane, yC4O), corresponding hydroperoxides, alcohols, hydroperoxy alkyl, and alkyl radicals which are formed in these oxidation reaction systems. Trends in carbon-hydrogen bond dissociation energies for the ring and hydroperoxide group relative to ring size and to distance from the ether group are determined. Bond dissociation energies are calculated for use in understanding effects of the ether oxygen in the cyclic ethers, their stability, and kinetic properties. Geometries, vibration frequencies, and enthalpies of formation, ΔH°f,298, are calculated at the B3LYP/6-31G(d,p), B3LYP/6-31G(2d,2p), the composite CBS-QB3, and G3MP2B3 methods. Entropy and heat capacities, S°(T) and Cp°(T) (5 K ≤ T ≤ 5000), are determined using geometric parameters and frequencies from the B3LYP/6-31G(d,p) calculations. The strong effects of ring strain on the bond dissociation energies in these peroxy systems are also of fundamental interest. Oxetane and oxolane exhibit a significant stabilization, 10 kcal mol(-1), lower ΔfH°298 when an oxygen group is on

  14. Determination of saturation pressure and enthalpy of vaporization of semi-volatile aerosols: the integrated volume mentod

    Science.gov (United States)

    This study presents the integrated volume method for estimating saturation pressure and enthalpy of vaporization of a whole aerosol distribution. We measure the change of total volume of an aerosol distribution between a reference state and several heated states, with the heating...

  15. Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

    Science.gov (United States)

    Fan, Chao; Pashley, Richard M.

    2016-01-01

    The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a…

  16. Measurements of high-pressure steam-water enthalpy/void migration in unequally heated horizontal twin subchannels

    Energy Technology Data Exchange (ETDEWEB)

    Sutradhar, S.C. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)]. E-mail: sutradhars@aecl.ca; Yin, S.T. [Consultant, Toronto, Ontario (Canada)]. E-mail: yinst@sympatico.ca; Tain, R.M. [Industrial Technology Research Inst., Chutung, Hsinchu, Taiwan (China)]. E-mail: rtain@itri.org.tw

    2006-07-01

    An experimental study of enthalpy/void migration in two interconnected, unequally heated horizontal subchannels was conducted using high-pressure steam-water as the operating medium. The cross-sectional geometry of the twin subchannels simulated two adjacent, top-to-bottom aligned inner subchannels of a 37-element CANDU fuel bundle. The effect of unequal heating on enthalpy/void migration was measured using three different heat flux ratios of 1.00, 1.11 and 1.21, with the higher heat flux in the top subchannel. The test results indicated that under similar flow conditions, the unequal heat flux set-up enhanced the enthalpy/void migration from the bottom to the top subchannel compared to the equal heat flux set up. This study quantifies and characterizes the buoyancy-induced enthalpy/void migration between two interconnected horizontal subchannels subject to different heat fluxes. The database will be used to validate and improve the flow-mixing models in subchannel codes. (author)

  17. Enthalpy changes during photosynthetic water oxidation tracked by time-resolved calorimetry using a photothermal beam deflection technique.

    Science.gov (United States)

    Krivanek, Roland; Dau, Holger; Haumann, Michael

    2008-03-01

    The energetics of the individual reaction steps in the catalytic cycle of photosynthetic water oxidation at the Mn(4)Ca complex of photosystem II (PSII) are of prime interest. We studied the electron transfer reactions in oxygen-evolving PSII membrane particles from spinach by a photothermal beam deflection technique, allowing for time-resolved calorimetry in the micro- to millisecond domain. For an ideal quantum yield of 100%, the enthalpy change, DeltaH, coupled to the formation of the radical pair Y(Z)(.+)Q(A)(-) (where Y(Z) is Tyr-161 of the D1 subunit of PSII) is estimated as -820 +/- 250 meV. For a lower quantum yield of 70%, the enthalpy change is estimated to be -400 +/- 250 meV. The observed nonthermal signal possibly is due to a contraction of the PSII protein volume (apparent DeltaV of about -13 A(3)). For the first time, the enthalpy change of the O(2)-evolving transition of the S-state cycle was monitored directly. Surprisingly, the reaction is only slightly exergonic. A value of DeltaH(S(3)-->S(0)) of -210 meV is estimated, but also an enthalpy change of zero is within the error range. A prominent nonthermal photothermal beam deflection signal (apparent DeltaV of about +42 A(3)) may reflect O(2) and proton release from the manganese complex, but also reorganization of the protein matrix.

  18. Enthalpy and phase behavior of coal derived liquid mixtures: Technical progress report for the period April-June 1987. [1-methylnaphthalene

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1987-07-31

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. During the twelfth quarter, enthalpy measurements for the compound of 1-methylnaphthalene have been completed and are included in Table 1. 16 refs., 5 figs., 4 tabs.

  19. Accurate Gas Phase Formation Enthalpies of Alloys and Refractories Decomposition Products.

    Science.gov (United States)

    Minenkov, Yury; Sliznev, Valery V; Cavallo, Luigi

    2017-02-06

    Accurate gas phase formation enthalpies, ΔHf, of metal oxides and halides are critical for the prediction of the stability of high temperature materials used in the aerospace and nuclear industries. Unfortunately, the experimental ΔHf values of these compounds in the most used databases, such as the NIST-JANAF database, are often reported with large inaccuracy, while some other ΔHf values clearly differ from the value predicted by CCSD(T) methods. To address this point, in this work we systematically predicted the ΔHf values of a series of these compounds having a group 4, 6, or 14 metal. The ΔHf values in question were derived within a composite Feller-Dixon-Peterson (FDP) scheme based protocol that combines the DLPNO-CCSD(T) enthalpy of ad hoc designed reactions and the experimental ΔHf values of few reference complexes. In agreement with other theoretical studies, we predict the ΔHf values for TiOCl2, TiOF2, GeF2, and SnF4 to be significantly different from the values tabulated in NIST-JANAF and other sources, which suggests that the tabulated experimental values are inaccurate. Similarly, the predicted ΔHf values for HfCl2, HfBr2, HfI2, MoOF4, MoCl6, WOF4, WOCl4, GeO2, SnO2, PbBr4, PbI4, and PbO2 also clearly differ from the tabulated experimental values, again suggesting large inaccuracy in the experimental values. In the case when largely different experimental values are available, we point to the value that is in better agreement with our results. We expect the ΔHf values reported in this work to be quite accurate, and thus, they might be used in thermodynamic calculations, because the effects from core correlation, relativistic effects, and basis set incompleteness were included in the DLPNO-CCSD(T) calculations. T1 and T2 values were thoroughly monitored as indicators of the quality of the reference Hartree-Fock orbitals (T1) and potential multireference character of the systems (T2).

  20. Accurate Gas Phase Formation Enthalpies of Alloys and Refractories Decomposition Products

    KAUST Repository

    Minenkov, Yury

    2017-01-17

    Accurate gas phase formation enthalpies, ΔHf, of metal oxides and halides are critical for the prediction of the stability of high temperature materials used in the aerospace and nuclear industries. Unfortunately, the experimental ΔHf values of these compounds in the most used databases, such as the NIST-JANAF database, are often reported with large inaccuracy, while some other ΔHf values clearly differ from the value predicted by CCSD(T) methods. To address this point, in this work we systematically predicted the ΔHf values of a series of these compounds having a group 4, 6, or 14 metal. The ΔHf values in question were derived within a composite Feller-Dixon-Peterson (FDP) scheme based protocol that combines the DLPNO-CCSD(T) enthalpy of ad hoc designed reactions and the experimental ΔHf values of few reference complexes. In agreement with other theoretical studies, we predict the ΔHf values for TiOCl2, TiOF2, GeF2, and SnF4 to be significantly different from the values tabulated in NIST-JANAF and other sources, which suggests that the tabulated experimental values are inaccurate. Similarly, the predicted ΔHf values for HfCl2, HfBr2, HfI2, MoOF4, MoCl6, WOF4, WOCl4, GeO2, SnO2, PbBr4, PbI4, and PbO2 also clearly differ from the tabulated experimental values, again suggesting large inaccuracy in the experimental values. In the case when largely different experimental values are available, we point to the value that is in better agreement with our results. We expect the ΔHf values reported in this work to be quite accurate, and thus, they might be used in thermodynamic calculations, because the effects from core correlation, relativistic effects, and basis set incompleteness were included in the DLPNO-CCSD(T) calculations. T1 and T2 values were thoroughly monitored as indicators of the quality of the reference Hartree-Fock orbitals (T1) and potential multireference character of the systems (T2).

  1. Systematic search for low-enthalpy sp3 carbon allotropes using evolutionary metadynamics

    Science.gov (United States)

    Zhu, Qiang; Zeng, Qingfeng; Oganov, Artem R.

    2012-05-01

    We present a systematic search for low-energy metastable superhard carbon allotropes by using the recently developed evolutionary metadynamics technique. It is known that cold compression of graphite produces an allotrope at 15-20 GPa. Here we look for all low-enthalpy structures accessible from graphite. Starting from 2H- or 3R-graphite and applying a pressure of 20 GPa, a large variety of intermediate sp3 carbon allotropes were observed in evolutionary metadynamics simulation. Our calculation not only found all the previous proposed candidates for “superhard graphite,” but also predicted two allotropes (X-carbon and Y-carbon) showing unusual types of 5+7 and 4+8 topologies. These superhard carbon allotropes can be classified into five families based on 6 (diamond/lonsdaleite), 5+7 (M- and W-carbon), 5+7 (X-carbon), 4+8 (bct-C4), and 4+8 (Y-carbon) topologies. This study shows that evolutionary metadynamics is a powerful approach both to find the global minima and systematically search for low-energy metastable phases reachable from given starting materials.

  2. Blunt-Body Aerothermodynamic Database from High-Enthalpy CO2 Testing in an Expansion Tunnel

    Science.gov (United States)

    Hollis, Brian R.; Prabhu, Dinesh K.; Maclean, Matthew; Dufrene, Aaron

    2016-01-01

    An extensive database of heating, pressure, and flow field measurements on a 70-deg sphere-cone blunt body geometry in high-enthalpy, CO2 flow has been generated through testing in an expansion tunnel. This database is intended to support development and validation of computational tools and methods to be employed in the design of future Mars missions. The test was conducted in an expansion tunnel in order to avoid uncertainties in the definition of free stream conditions noted in previous studies performed in reflected shock tunnels. Data were obtained across a wide range of test velocity/density conditions that produced various physical phenomena of interest, including laminar and transitional/turbulent boundary layers, non-reacting to completely dissociated post-shock gas composition and shock-layer radiation. Flow field computations were performed at the test conditions and comparisons were made with the experimental data. Based on these comparisons, it is recommended that computational uncertainties on surface heating and pressure, for laminar, reacting-gas environments can be reduced to +/-10% and +/-5%, respectively. However, for flows with turbulence and shock-layer radiation, there were not sufficient validation-quality data obtained in this study to make any conclusions with respect to uncertainties, which highlights the need for further research in these areas.

  3. Analysis of experimental routines of high enthalpy steam discharge in subcooled water

    Energy Technology Data Exchange (ETDEWEB)

    Pacheco, Rafael R., E-mail: Rafael.rade@ctmsp.mar.mil.br [Centro Tecnologico da Marinha em Sao Paulo (CTMSP), SP (Brazil); Andrade, Delvonei A., E-mail: delvonei@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The discharge of high enthalpy steam through safety release valves out from pressurizers in PWR's needs to be condensed in order to allow the treatment of possibly present radwaste within. The Direct Contact Condensation is used in a relief tank to achieve the condensation. Care must be taken to avoid the bypass of the steam through the subcooled water, what would increase the peak of pressure and the necessity of structural reinforcement of the relief tank. An experiment to determine the optimal set up of the relief tank components and their characteristics (type of sprinkler, level of water, volume of tank, discharge direction, pressure in the pressurizer among others) was executed in 2000, in the CTE 150 facility, in CTMSP. In a total, 144 routines varying its components and characteristics were made, although no comprehensive analysis of its results were yet made, since the mass of data was too big to be readily analyzed. In order to comprehensively analyze it, a VBA program is being made to compile and graphically represent the mass of data. The current state of this program allowed conclusions over the peak pressure, adiabatic assumption of the experiment, and the quality of the steam generated due to the discharge. (author)

  4. A Non-Isothermal Chemical Lattice Boltzmann Model Incorporating Thermal Reaction Kinetics and Enthalpy Changes

    Directory of Open Access Journals (Sweden)

    Stuart Bartlett

    2017-08-01

    Full Text Available The lattice Boltzmann method is an efficient computational fluid dynamics technique that can accurately model a broad range of complex systems. As well as single-phase fluids, it can simulate thermohydrodynamic systems and passive scalar advection. In recent years, it also gained attention as a means of simulating chemical phenomena, as interest in self-organization processes increased. This paper will present a widely-used and versatile lattice Boltzmann model that can simultaneously incorporate fluid dynamics, heat transfer, buoyancy-driven convection, passive scalar advection, chemical reactions and enthalpy changes. All of these effects interact in a physically accurate framework that is simple to code and readily parallelizable. As well as a complete description of the model equations, several example systems will be presented in order to demonstrate the accuracy and versatility of the method. New simulations, which analyzed the effect of a reversible reaction on the transport properties of a convecting fluid, will also be described in detail. This extra chemical degree of freedom was utilized by the system to augment its net heat flux. The numerical method outlined in this paper can be readily deployed for a vast range of complex flow problems, spanning a variety of scientific disciplines.

  5. Computational modelling of the gas flow from a high-enthalpy blast simulator

    Science.gov (United States)

    Edwards, D. G.; Phan, K. C.; Hurdle, C. V.

    1990-07-01

    An Eulerian computer code based on the Flux-Corrected Transport algorithm has been develped to model the flow within and in the immediate vicinity of the RARDE (UK) High-Enthalpy Blast Simulator. The code incorporates a fully-second-order solution-scheme incorporating operator-splitting in the solution of multi-dimensional time-dependent flows. The computing mesh has been refined to make efficient use of the limited computing memory and processing power available to this project. The flow is one-dimensional in much the greater part of the facility: two-dimensional axi-symmetric flow is confined to the junctions between long tubes of constant diameter, and the computing mesh is configured accordingly. Early runs of the code have been based on a coarse computing mesh, for reasons of expedinency. Even so, results to date have confirmed may of the qualitative predictions concerning the behavior of the HEBSIM; comparisons with existing experimental data on wall-pressure histories at various stations within the facility show an encouraging measure of accord. Later runs will feature a more refined mesh, and it is hoped that design-recommendations will result from this more-realistic simulation exercise as an aid to the further developement of the HEBSIM facility.

  6. An automated flow calorimeter for heat capacity and enthalpy measurements at elevated temperatures and pressures

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.

    1990-08-31

    The need for highly accurate thermal property data for a broad range of new application fluids is well documented. To facilitate expansion of the current thermophysical database, an automated flow calorimeter was developed for the measurement of highly accurate isobaric heat capacities and enthalpies of fluids at elevated temperatures and pressures. The experimental technique utilizes traditional electrical power input, adiabatic flow calorimetry with a precision metering pump that eliminates the need for on-line flow rate monitoring. In addition, a complete automation system, greatly simplifies the operation of the apparatus and increases the rapidity of the measurement process. The range over which the instrument was tested, was 300--600 K and 0--12 Mpa, although the calorimeter should perform up to the original design goals of 700 K and 30 MPa. The new flow calorimeter was evaluated by measuring the mean, isobaric, specific heat capacities of liquid water and n-pentane. These experiments yielded an average deviation from the standard literature data of +0.02% and a total variation of 0.05%. Additional data analysis indicated that the overall measurement uncertainty was conservatively estimated as 0.2% with an anticipated precision of 0.1--0.15% at all operating conditions. 44 refs., 27 figs., 2 tabs.

  7. The C-H bond dissociation enthalpies in fused N-heterocyclic compounds

    Science.gov (United States)

    Wang, Ying-Xing; Zheng, Wen-Rui; Ding, Lan-Lan

    2016-03-01

    The C-H bond dissociation enthalpies (BDEs) of the 26 N, O, S-containing mono-heterocyclic compounds were evaluated using the composite high-level ab initio methods G3 and G4. The C-H BDEs for 32 heterocyclic compounds were calculated using 8 types of density functional theory (DFT) methods. Comparing with the experimental values, the BMK method gave the lowest root mean square error (RMSE) of 7.2 kJ/mol. Therefore, the C-H BDEs of N-fused-heterocyclic compounds at different positions were investigated by the BMK method. By NBO analysis two linear relationships between the C-H BDEs of quinoline and isoquinoline with natural charges qC/ e in molecules and with natural charges qC/ e in radicals were found. The substituent effects on C(α)-H BDEs in N-fused-heterocyclic compounds were also discussed. It was found that there are two linear relationships between the C(α)-H BDEs of quinoline and isoquinoline derivatives with natural charges qC(α)/ e for the EDGs and CEGs substituents.

  8. The Atmospherically Important Reaction of Hydroxyl Radicals with Methyl Nitrate: A Theoretical Study Involving the Calculation of Reaction Mechanisms, Enthalpies, Activation Energies, and Rate Coefficients.

    Science.gov (United States)

    Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M

    2017-09-07

    A theoretical study, involving the calculation of reaction enthalpies, activation energies, mechanisms, and rate coefficients, was made of the reaction of hydroxyl radicals with methyl nitrate, an important process for methyl nitrate removal in the earth's atmosphere. Four reaction channels were considered: formation of H 2 O + CH 2 ONO 2 , CH 3 OOH + NO 2 , CH 3 OH + NO 3 , and CH 3 O + HNO 3 . For all channels, geometry optimization and frequency calculations were performed at the M06-2X/6-31+G** level, while relative energies were improved at the UCCSD(T*)-F12/CBS level. The major channel is found to be the H abstraction channel, to give the products H 2 O + CH 2 ONO 2 . The reaction enthalpy (ΔH 298 K RX ) of this channel is computed as -17.90 kcal mol -1 . Although the other reaction channels are also exothermic, their reaction barriers are high (>24 kcal mol -1 ), and therefore these reactions do not contribute to the overall rate coefficient in the temperature range considered (200-400 K). Pathways via three transition states were identified for the H abstraction channel. Rate coefficients were calculated for these pathways at various levels of variational transition state theory including tunneling. The results obtained are used to distinguish between two sets of experimental rate coefficients, measured in the temperature range of 200-400 K, one of which is approximately an order of magnitude greater than the other. This comparison, as well as the temperature dependence of the computed rate coefficients, shows that the lower experimental values are favored. The implications of the results to atmospheric chemistry are discussed.

  9. Excess enthalpies of binary mixtures of 1-hexene with some branched alkanes at the temperature 298.15 K[Excess enthalpy; Binary mixture; 1-Hexene; Branched alkanes; Liebermann-Fried model

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhaohui; Benson, George C.; Lu, Benjamin C.-Y. E-mail: lu@eng.uottawa.ca

    2004-01-01

    Measurements of excess molar enthalpies at the temperature 298.15 K in a flow microcalorimeter are reported for the five binary mixtures formed by mixing 1-hexene with the branched alkanes: 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, and 2,2,4-trimethylpentane. Smooth Redlich-Kister representations of the results are described. It was found that the Liebermann-Fried model also provided good representations of the results.

  10. Evaluation of the Gibbs Free Energy Changes and Melting Temperatures of DNA/DNA Duplexes Using Hybridization Enthalpy Calculated by Molecular Dynamics Simulation.

    Science.gov (United States)

    Lomzov, Alexander A; Vorobjev, Yury N; Pyshnyi, Dmitrii V

    2015-12-10

    A molecular dynamics simulation approach was applied for the prediction of the thermal stability of oligonucleotide duplexes. It was shown that the enthalpy of the DNA/DNA complex formation could be calculated using this approach. We have studied the influence of various simulation parameters on the secondary structure and the hybridization enthalpy value of Dickerson-Drew dodecamer. The optimal simulation parameters for the most reliable prediction of the enthalpy values were determined. The thermodynamic parameters (enthalpy and entropy changes) of a duplex formation were obtained experimentally for 305 oligonucleotides of various lengths and GC-content. The resulting database was studied with molecular dynamics (MD) simulation using the optimized simulation parameters. Gibbs free energy changes and the melting temperatures were evaluated using the experimental correlation between enthalpy and entropy changes of the duplex formation and the enthalpy values calculated by the MD simulation. The average errors in the predictions of enthalpy, the Gibbs free energy change, and the melting temperature of oligonucleotide complexes were 11%, 10%, and 4.4 °C, respectively. We have shown that the molecular dynamics simulation gives a possibility to calculate the thermal stability of native DNA/DNA complexes a priori with an unexpectedly high accuracy.

  11. Enthalpy measurement of coal-derived liquids. Final report, April 1981-September 1983. [517 to 10342 kPa; 340 to 664 K

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1983-11-10

    This report summarizes the results of experimental measurements of enthalpies for quinoline using a freon boil-off flow calorimeter, and an investigation of the applicability of cubic equations of state to correlating the enthalpy of coal-liquids. In Part A the compound quinoline is discussed. Process flow in the flow calorimeter, operational problems, and equipment modifications are described. Procedural modifications, including a new sample purification procedure, are described. Part B discusses the correlational effort. This includes a discussion of past correlational work and the difficulties associated with a general correlation for coal liquid enthalpy. In addition experimental data and computer generated predictions are presented. Three equations of state were used to predict vapor pressures and enthalpies for ten pure component systems previously studied in the lab. In general, the results were encouraging. All three equations were found to be effective in predicting both enthalpies and vapor pressures. In addition, the equations worked well when fit to mixture enthalpies. The Modified SRK equation was found to be superior to the other equations and modeled all properties for both associating and nonassociating systems well. The Modified SRK equation did have a drawback in that it was not readily generalized since it required two parameters which must be fit to data for best results. In sum, it was shown that a four parameter equation of state could be used successfully to correlate the enthalpy of coal-liquid model compounds.

  12. Non-equilibrium theory employing enthalpy-based equation of state for binary solid and porous mixtures

    Science.gov (United States)

    Nayak, B.; Menon, S. V. G.

    2017-04-01

    A generalized enthalpy-based equation of state, which includes thermal electron excitations and non-equilibrium thermal energies, is formulated for binary solid and porous mixtures. Our approach gives rise to an extra contribution to mixture volume, in addition to those corresponding to average mixture parameters. This excess term involves the difference of thermal enthalpies of the two components, which depend on their individual temperatures. We propose to use the Hugoniot of the components to compute non-equilibrium temperatures in the mixture. These are then compared with the average temperature obtained from the mixture Hugoniot, thereby giving an estimate of non-equilibrium effects. The Birch-Murnaghan model for the zero-temperature isotherm and a linear thermal model are then used for applying the method to several mixtures, including one porous case. Comparison with experimental data on the pressure-volume Hugoniot and shock speed versus particle speed shows good agreement.

  13. Enthalpy and phase behavior of coal derived liquid mixtures: Technical progress report for the period October-December 1986

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1987-01-01

    The objectives of this program are to study the enthalpy and phase behavior of a selected ternary model compound system, representative of interactions present in coal derived liquids. Measurements have been made in a Freon 11 reference fluid-boil-off calorimeter, and an equilibrium flash vaporization apparatus. During the tenth quarter, enthalpy measurements for the m-cresol/quinoline/tetralin ternary system have been initiated and are included in Appendix A. Vapor liquid equilibria measurements for the m-cresol/quinoline/tetralin ternary system have been completed for four isotherms: 250, 275, 300, 325/sup 0/C, at various pressures. These results and a summary of progress to date for the VLE apparatus are in Appendix B. Also, predictions for the ternary system using the binary interaction parameters generated from previously obtained binary data were completed, and these results are also presented in Appendix B.

  14. Enthalpies of transfer of N-methylformamide, formamide, and N,N-dimethylformamide from methanol to methanol + dimethylsulfoxide mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Feakins, D.; O' Duinn, C.C.; Waghorne, W.E.

    1987-11-01

    The enthalpies of transfer of formamide, N-methylformamide and N,N-dimethylformamide from methanol to methanol + dimethylsulfoxide solvent systems have been measured. These data are analyzed in terms of a recently developed model of solvation in mixed solvents. The results of the data analyses indicate that preferential solvation of the different functional groups of the amides differs, the carbonyl oxygen being preferentially solvated by methanol and the nitrogen protons are by dimethylsulfoxide.

  15. Research of Workflow Efficiency in HighEnthalpy Air Flow Compact Generators

    Directory of Open Access Journals (Sweden)

    V. Yu. Aleksandrov

    2015-01-01

    Full Text Available To test the combustion chambers (CC of high-speed ramjet engine (ramjet it is necessary to create the inlet conditions as realistic as possible, including the stagnation temperature T0, the Mach number M0, and the total airflow pressure p0. To achieve T0 = 1000 ... 2000 K is possible using a high-enthalpy airflow generator (HAG providing the fired air-heating and oxygen balance compensation.Due to strict weight and size restrictions imposed by the test conditions of the ramjet CC and bench equipment, there is a need to reduce HAG size and weight. For small HAG the relevant tasks are to organize effective workflow and ensure combustion stability, which can be solved directly at the developmental testing stage.The characteristic criterion of the workflow efficiency in HAG is the completed physicochemical combustion processes of the working fluid components. This is due to the fact that in the testing process a possible after-burning component of the working fluid in the flow path of the ramjet CC has a significant impact on the studied characteristics of the engine, thereby having a detrimental effect on the quality of the experiment.The examination of the workflow efficiency in HAG showed that the use of hydrogen as a fuel allows us to achieve a high degree of completing the physicochemical processes and reaching the specified conditions at the CC inlet to the ramjet under test. The use of hydrocarbon fuels reduces the completion degree of the workflow process in HAG and is accompanied by the development of pressure pulsations.The data obtained can be used when developing various HAGs, including those intended for testing the CC of ramjets for the prospective aircrafts.

  16. Enthalpy measurement of coal-derived liquids. Technical progress report, February 1983-April 1983

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1983-05-31

    This quarter's work has concentrated on two primary areas. The first was the completion of experimental measurements of the associated factor. The second area was a look at current equation of state application. The work has progressed smoothly so far and should in future emphasize the computational work. The significant systems looked at this quarter were the C/sub 2/-C/sub 6/ alcohols, cresol, quinoline, and cresol-quinoline mixtures. The alcohols and cresols are important because the hydroxyl hydrogen bonding which is believed to be the primary association mechanism in coal liquids. Quinoline is significant because it is an excellent model for nitrogen containing constituents of coal liquids. The cresol-quinoline system, which was measured for range of system compositions, was studied because enthalpy data for a similar range of compositions was available. The results for most of these systems were reasonable and make important additions to previous data. The results for the quinoline-cresol mixture systems were curious and very different from anything previous to these measurements. The causes of these results are currently not well understood. Clearly they are due to complex interaction phenomena occurring in these systems. Since this behavior is not generally seen in complex mixtures, it is felt that the behavior is due to the fact that the cresol-quinoline system is a simple binary system which allows complex composition dependent solute-solute-solvent interactions to occur. This effect would also probably occur in ternary, quartenary, and maybe even higher systems. This behavior would tend to washout in coal liquids which have hundreds of components. As a result, it is felt that pure component systems are more valid models for coal liquid associations and that binary, etc., systems are too great a complexity to be currently understood.

  17. Enthalpy-Based Thermal Evolution of Loops: II. Improvements to the Model

    Science.gov (United States)

    Cargill, P. J.; Bradshaw, S. J.; Klimchuk, J. A.

    2011-01-01

    This paper further develops the zero-dimensional (0D) hydrodynamic coronal loop model "Enthalpy-based Thermal Evolution of Loops" (EBTEL) originally proposed by Klimchuk et al (2008), which studies the plasma response to evolving coronal heating. It has typically been applied to impulsive heating events. The basis of EBTEL is the modelling of mass exchange between the corona and transition region and chromosphere in response to heating variations, with the key parameter being the ratio of transition region to coronal radiation. We develop new models for this parameter that now include gravitational stratification and a physically motivated approach to radiative cooling. A number of examples are presented, including nanoflares in short and long loops, and a small flare. It is found that while the evolution of the loop temperature is rather insensitive to the details of the model, accurate tracking of the density requires the inclusion of our new features. In particular, we are able to now obtain highly over-dense loops in the late cooling phase and decreases to the coronal density arising due to stratification. The 0D results are compared to a 1D hydro code (Hydrad). The agreement is acceptable, with the exception of the flare case where some versions of Hydrad can give significantly lower densities. This is attributed to the method used to model the chromosphere in a flare. EBTEL is suitable for general use as a tool for (a) quick-look results of loop evolution in response to a given heating function and (b) situations where the modelling of hundreds or thousands of elemental loops is needed. A single run takes a few seconds on a contemporary laptop.

  18. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, July--September 1978. [148 to 459/sup 0/F and 100 to 300 psia

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1978-12-01

    Experimental measurements were completed on a naphtha sample (1046) furnished by the Pittsburgh and Midway Coal Mining Company. A total of 38 measurements were made in the temperature region 148 to 459/sup 0/F, and at pressures of 100 and 300 psia. Additional analytical work was completed on the SRC-I naphtha whose enthalpy measurements were reported previously. Comparisons are given between the experimental SRC-I naphtha enthalpies and the available enthalpy data on petroleum fractions, including Kesler and Lee's correlation of these data. (LTN)

  19. Standard molar Gibbs free energy and enthalpy of solvation of low polar solutes in formamide derivatives at 298 K

    Energy Technology Data Exchange (ETDEWEB)

    Sedov, I.A., E-mail: igor_sedov@inbox.ru; Magsumov, T.I.; Stolov, M.A.; Solomonov, B.N.

    2016-01-10

    Highlights: • Standard molar enthalpies of solution of low polar solutes in NMF were measured. • Limiting activity coefficients in NMF were measured. • The solvophobic effects are present but weaker in NMF than in formamide. • We can tune the solvophobic effects by mixing NMF or formamide with other solvents. - Abstract: Novel experimental values of the limiting activity coefficients and standard molar enthalpies of solution in N-methylformamide at 298.15 K are reported and used to calculate the thermodynamic functions of solvation. We compare the plots of the standard molar Gibbs free energy against the standard molar enthalpy of solvation of low polar molecules in N-methylformamide, N,N-dimethylformamide, and formamide. The solvophobic effect is responsible for the deviations of the data points from the straight line corresponding to a correlation between thermodynamic functions of solvation in aprotic solvents. It is shown that the solvophobic effects are strong in formamide solutions, significantly weaker in N-methylformamide, and very weak in N,N-dimethylformamide, which coincides with the average number of intermolecular hydrogen bonds per unit volume of these solvents. Behavior of solutions in binary solvents composed of N-methylformamide or formamide mixed with water and ethylene glycol and a possibility to tune the solvophobic effect by changing the solvent composition are also considered.

  20. Comparison and verification of enthalpy schemes for polythermal glaciers and ice sheets with a one-dimensional model

    CERN Document Server

    Blatter, Heinz

    2014-01-01

    The enthalpy method for the thermodynamics of polythermal glaciers and ice sheets is tested and verified by a one-dimensional problem (parallel-sided slab). The enthalpy method alone does not include explicitly the Stefan-type energy- and mass-flux matching conditions at the cold-temperate transition surface (CTS) that separates the upper cold from the lower temperate layer. However, these transition conditions are important for correctly determining the position of the CTS. For the numerical solution of the polythermal slab problem, we consider a two-layer front-tracking scheme as well as three different one-layer schemes that feature a single grid for both layers. Computed steady-state temperature and moisture profiles are verified with exact solutions, and transient solutions computed by the one-layer schemes are compared with those of the two-layer scheme, considered to be a reliable reference. While the conventional one-layer enthalpy scheme (that does not include the transition conditions at the CTS) ca...

  1. Impact of Flight Enthalpy, Fuel Simulant, and Chemical Reactions on the Mixing Characteristics of Several Injectors at Hypervelocity Flow Conditions

    Science.gov (United States)

    Drozda, Tomasz G.; Baurle, Robert A.; Drummond, J. Philip

    2016-01-01

    The high total temperatures or total enthalpies required to duplicate the high-speed flight conditions in ground experiments often place stringent requirements on the material selection and cooling needs for the test articles and intrusive flow diagnostic equipment. Furthermore, for internal flows, these conditions often complicate the use of nonintrusive diagnostics that need optical access to the test section and interior portions of the flowpath. Because of the technical challenges and increased costs associated with experimentation at high values of total enthalpy, an attempt is often made to reduce it. This is the case for the Enhanced Injection and Mixing Project (EIMP) currently underway in the Arc-Heated Scramjet Test Facility at the NASA Langley Research Center. The EIMP aims to investigate supersonic combustion ramjet (scramjet) fuel injection and mixing physics, improve the understanding of underlying physical processes, and develop enhancement strategies and functional relationships between mixing performance and losses relevant to flight Mach numbers greater than 8. The experiments will consider a "direct-connect" approach and utilize a Mach 6 nozzle to simulate the combustor entrance flow of a scramjet engine. However, while the value of the Mach number is matched to that expected at the combustor entrance in flight, the maximum value of the total enthalpy for these experiments is limited by the thermal-structural limits of the uncooled experimental hardware. Furthermore, the fuel simulant is helium, not hydrogen. The use of "cold" flows and non-reacting mixtures of fuel simulants for mixing experiments is not new and has been extensively utilized as a screening technique for scramjet fuel injectors. In this study, Reynolds-averaged simulations are utilized (RAS) to systematically verify the implicit assumptions used by the EIMP. This is accomplished by first performing RAS of mixing for two injector configurations at planned nominal experimental

  2. The reaction enthalpy of hydrogen dissociation calculated with the Small System Method from simulation of molecular fluctuations.

    Science.gov (United States)

    Skorpa, Ragnhild; Simon, Jean-Marc; Bedeaux, Dick; Kjelstrup, Signe

    2014-09-28

    We show how we can find the enthalpy of a chemical reaction under non-ideal conditions using the Small System Method to sample molecular dynamics simulation data for fluctuating variables. This method, created with Hill's thermodynamic analysis, is used to find properties in the thermodynamic limit, such as thermodynamic correction factors, partial enthalpies, volumes, heat capacities and compressibility. The values in the thermodynamic limit at (T,V, μj) are then easily transformed into other ensembles, (T,V,Nj) and (T,P,Nj), where the last ensemble gives the partial molar properties which are of interest to chemists. The dissociation of hydrogen from molecules to atoms was used as a convenient model system. Molecular dynamics simulations were performed with three densities; ρ = 0.0052 g cm(-3) (gas), ρ = 0.0191 g cm(-3) (compressed gas) and ρ = 0.0695 g cm(-3) (liquid), and temperatures in the range; T = 3640-20,800 K. The enthalpy of reaction was observed to follow a quadratic trend as a function of temperature for all densities. The enthalpy of reaction was observed to only have a small pressure dependence. With a reference point close to an ideal state (T = 3640 K and ρ = 0.0052 g cm(-3)), we were able to calculate the thermodynamic equilibrium constant, and thus the deviation from ideal conditions for the lowest density. We found the thermodynamic equilibrium constant to increase with increasing temperature, and to have a negligible pressure dependence. Taking the enthalpy variation into account in the calculation of the thermodynamic equilibrium constant, we found the ratio of activity coefficients to be in the order of 0.7-1.0 for the lowest density, indicating repulsive forces between H and H2. This study shows that the compressed gas- and liquid density values at higher temperatures are far from those calculated under ideal conditions. It is important to have a method that can give access to partial molar properties, independent of the ideality of

  3. The effect of a fourth element (Co, Cu, Fe, Pd) on the standard enthalpy of formation of the Heusler compound Ni{sub 2}MnSn

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Ming, E-mail: myin1@hawk.iit.edu; Nash, Philip

    2016-05-15

    The standard enthalpies of formation of quaternary Heusler compounds (X, Ni){sub 2}MnSn (X = Co, Cu, Fe, Pd) were investigated experimentally using high temperature direct reaction calorimetry. Lattice parameters of these compounds were determined using X-ray diffraction analysis. Microstructures were identified using scanning electron microscopy and energy dispersive spectroscopy. The effect of an additional X element on the standard enthalpy of formation of the Heusler compound Ni{sub 2}MnSn is discussed. - Highlights: • Enthalpies of formation of (X,Ni){sub 2}YZ (X = Co, Cu, Fe, Pd) were measured by drop calorimeters. • Magnetic contribution to enthalpy of formation plays an important role. • Introducing a fourth element could stabilize an unstable Heusler structure. • Lattice parameters do not necessarily obey the Vegard's law. • It is possible to tailor properties of Heusler compounds with enough background information.

  4. Self-diffusion in crystalline silicon: A single diffusion activation enthalpy down to 755°

    Science.gov (United States)

    Südkamp, Tobias; Bracht, Hartmut

    2016-09-01

    Self-diffusion in silicon and the contribution of vacancies and self-interstitials have been controversially discussed for 50 yr. Most recent results show that the intrinsic silicon self-diffusion coefficient deviates from an Arrhenius-type, single exponential function for temperatures below 950° [Y. Shimizu, M. Uematsu, and K. M. Itoh, Phys. Rev. Lett. 98, 095901 (2007), 10.1103/PhysRevLett.98.095901; R. Kube, H. Bracht, E. Hüger, H. Schmidt, J. L. Hansen, A. N. Larsen, J. W. Ager, E. E. Haller, T. Geue, and J. Stahn, Phys. Rev. B 88, 085206 (2013), 10.1103/PhysRevB.88.085206]. This led us to propose temperature-dependent thermodynamic properties of vacancies in order to achieve full consistency to vacancy-mediated dopant diffusion in silicon. Concepts of temperature-dependent properties of native defects or distinct forms of defects with different formation entropies suggested by Cowern et al. [N. E. B. Cowern, S. Simdyankin, C. Ahn, N. S. Bennett, J. P. Goss, J.-M. Hartmann, A. Pakfar, S. Hamm, J. Valentin, E. Napolitani, D. De Salvador, E. Bruno, and S. Mirabella, Phys. Rev. Lett. 110, 155501 (2013), 10.1103/PhysRevLett.110.155501] question the present understanding on atomic transport in semiconductors. To verify these concepts, additional self-diffusion experiments under particular gettering conditions were performed. As a result, silicon self-diffusion was found to be accurately described by one single diffusion activation enthalpy of (4.73 ±0.02 ) eV down to 755°C. This provides full consistency to dopant diffusion without claiming native-defect concepts that were originally proposed by Seeger and Chik in 1968 [A. Seeger and K. P. Chik, Phys. Stat. Sol. 29, 455 (1968), 10.1002/pssb.19680290202] and confirms most recent density functional theory calculations on the activation energy of self-diffusion via vacancies and self-interstitials. Overall, this unravels the old debate of self-diffusion in silicon with the supposed intrinsic temperature dependence.

  5. Effect of halogen substitution on the enthalpies of solvation and hydrogen bonding of organic solutes in chlorobenzene and 1,2-dichlorobenzene derived using multi-parameter correlations

    Energy Technology Data Exchange (ETDEWEB)

    Varfolomeev, Mikhail A.; Rakipov, Ilnaz T.; Khachatrian, Artashes A. [Department of Physical Chemistry, Kazan Federal University, Kremlevskaya 18, Kazan 420008 (Russian Federation); Acree, William E., E-mail: acree@unt.edu [Department of Chemistry, 1155 Union Circle # 305070, University of North Texas, Denton, TX 76203-5017 (United States); Brumfield, Michela [Department of Chemistry, 1155 Union Circle # 305070, University of North Texas, Denton, TX 76203-5017 (United States); Abraham, Michael H. [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2015-10-10

    Graphical abstract: - Highlights: • Enthalpies of solution measured for 43 solutes dissolved in chlorobenzene. • Enthalpies of solution measured for 72 solutes dissolved in 1,2-dichlorobenzene. • Mathematical expressions derived for predicting enthalpies of solvation of solutes in chlorobenzene. • Mathematical expressions derived for predicting enthalpies of solvation of solutes in 1,2-chlorobenzene. - Abstract: Enthalpies of solution at infinite dilution at 298 K, Δ{sub soln}H{sup A/Solvent}, have been measured by isothermal solution calorimetry for 43 and 72 organic solutes dissolved in chlorobenzene and 1,2-dichlorobenzene, respectively. The measured Δ{sub soln}H{sup A/Solvent} data, along with published Δ{sub soln}H{sup A/Solvent} values taken from the published literature for solutes dissolved in both chlorobenzene solvents, were converted to enthalpies of solvation, Δ{sub solv}H{sup A/Solvent}, using standard thermodynamic equations. Abraham model correlations were developed from the experimental Δ{sub solv}H{sup A/Solvent} data. The best derived correlations describe the experimental gas-to-chlorobenzene and gas-to-1,2-dichlorobenzene enthalpies of solvation to within standard deviations of 1.5 kJ mol{sup −1} and 1.9 kJ mol{sup −1}, respectively. Enthalpies of X−H…π (X – O, N, and C) hydrogen bond formation of proton donor solutes (alcohols, amines, chlorinated hydrocarbons, etc.) with chlorobenzene and 1,2-dichlorobenzene were calculated based on the Abraham solvation equation. Obtained values are in good agreement with the results determined using conventional methods.

  6. A compilation of correlation parameters for predicting the enthalpy and thermal conductivity of solid foods within the temperature range of -40 C to +40 C

    Energy Technology Data Exchange (ETDEWEB)

    Amos, N.D. [Comvita New Zealand Limited, Private Bag 1, Te Puke 3153 (New Zealand); Willix, J.; North, M.F. [AgResearch Limited, MIRINZ Centre, Ruakura Campus, East Street, Private Bag 3123, Hamilton (New Zealand); Chadderton, T. [Crop and Food Research Ltd, PO Box 5114, Nelson (New Zealand)

    2008-11-15

    This paper presents thermal conductivity data for 40 foods, enthalpy data for 58 foods and density data for nine foods, along with the compositions of the foods. Measurements cover a range of solid food types (including meats, fats, offal, fish, dairy products and horticultural products). Some measurements reported are for foods that have never before been studied, others have been published elsewhere, but are included here for convenience. Thermal conductivity was measured using a guarded hot-plate apparatus, enthalpy using an adiabatic calorimeter and density using a water displacement meter. Thermal conductivity and enthalpy values were measured within the temperature range of -40 C to +40 C. (author) [French] Cette publication presente des donnes sur la conductivite thermique, l'enthalpie et la densite respectivement de 40, 58 et 9 produits alimentaires, ainsi que leurs compositions. Les mesures couvrent une variete de types de produits alimentaires (viande, matieres grasses, abats, poisson, produits laitiers, produits horticoles). Certaines sont rapportees pour des produits qui n 'ant jamais ete etudie auparavant, d'autres ant ete publie ailleurs mais sont aussi inclues pour plus de commodite. La conductivite thermique a ete mesure avec un appareil a plaque electrique protegee, l'enthalpie avec un calorimetre adiabatique et la densite avec un appareil mesurant Ie deplacement d'eau. La conductivite thermique et l'enthalpie ont ete toutes les mesures pour une fourchette de temperatures allant de -40 C a 40 C. (orig.)

  7. Field tests for the comparative evaluation of heat and enthalpy exchangers in compact ventilation units; Feldvergleich von Waerme- und Enthalpieuebertragern in Kompakt-Lueftungsgeraeten - Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Frei, B.

    2007-07-01

    In an efficiency review on low energy buildings promoted by the Swiss Federal Office of Energy, low air humidity has been measured during thousands of annual hours. Modern compact ventilation units are being increasingly offered with transmission of heat and moisture. One possibility to raise the air humidity level is an enthalpy exchanger with steam-permeable membranes. With an enthalpy exchanger you can not only recover heat but also a good part of the humidity of the return air. In a comparative field study alternate applications with enthalpy or heat exchangers have been analysed at four different locations. Also calculations have been made to estimate how a rotating heat exchanger with ion-exchange resin would have performed. The comparative field study has shown that the enthalpy exchanger is able to raise the humidity level. Conditions for this are internal humidity loads, balanced air volume rates which correspond to occupancy as well as low leakages of the ventilation unit. Over-moistening due to the system with enthalpy exchanger was not found. The measurements have been affected by a sequence of winter months which have been partially warmer than usual. Otherwise the difference between enthalpy and heat exchangers would have been more significant. (author)

  8. Boundary Layer Transition and Trip Effectiveness on an Apollo Capsule in the JAXA High Enthalpy Shock Tunnel (HIEST) Facility

    Science.gov (United States)

    Kirk, Lindsay C.; Lillard, Randolph P.; Olejniczak, Joseph; Tanno, Hideyuki

    2015-01-01

    Computational assessments were performed to size boundary layer trips for a scaled Apollo capsule model in the High Enthalpy Shock Tunnel (HIEST) facility at the JAXA Kakuda Space Center in Japan. For stagnation conditions between 2 MJ/kg and 20 MJ/kg and between 10 MPa and 60 MPa, the appropriate trips were determined to be between 0.2 mm and 1.3 mm high, which provided kappa/delta values on the heatshield from 0.15 to 2.25. The tripped configuration consisted of an insert with a series of diamond shaped trips along the heatshield downstream of the stagnation point. Surface heat flux measurements were obtained on a capsule with a 250 mm diameter, 6.4% scale model, and pressure measurements were taken at axial stations along the nozzle walls. At low enthalpy conditions, the computational predictions agree favorably to the test data along the heatshield centerline. However, agreement becomes less favorable as the enthalpy increases conditions. The measured surface heat flux on the heatshield from the HIEST facility was under-predicted by the computations in these cases. Both smooth and tripped configurations were tested for comparison, and a post-test computational analysis showed that kappa/delta values based on the as-measured stagnation conditions ranged between 0.5 and 1.2. Tripped configurations for both 0.6 mm and 0.8 mm trip heights were able to effectively trip the flow to fully turbulent for a range of freestream conditions.

  9. Capacitive Detection of Low-Enthalpy, Higher-Order Phase Transitions in Synthetic and Natural Composition Lipid Membranes.

    Science.gov (United States)

    Taylor, Graham J; Heberle, Frederick A; Seinfeld, Jason S; Katsaras, John; Collier, C Patrick; Sarles, Stephen A

    2017-09-26

    In-plane lipid organization and phase separation in natural membranes play key roles in regulating many cellular processes. Highly cooperative, first-order phase transitions in model membranes consisting of few lipid components are well understood and readily detectable via calorimetry, densitometry, and fluorescence. However, far less is known about natural membranes containing numerous lipid species and high concentrations of cholesterol, for which thermotropic transitions are undetectable by the above-mentioned techniques. We demonstrate that membrane capacitance is highly sensitive to low-enthalpy thermotropic transitions taking place in complex lipid membranes. Specifically, we measured the electrical capacitance as a function of temperature for droplet interface bilayer model membranes of increasing compositional complexity, namely, (a) a single lipid species, (b) domain-forming ternary mixtures, and (c) natural brain total lipid extract (bTLE). We observed that, for single-species lipid bilayers and some ternary compositions, capacitance exhibited an abrupt, temperature-dependent change that coincided with the transition detected by other techniques. In addition, capacitance measurements revealed transitions in mixed-lipid membranes that were not detected by the other techniques. Most notably, capacitance measurements of bTLE bilayers indicated a transition at ∼38 °C not seen with any other method. Likewise, capacitance measurements detected transitions in some well-studied ternary mixtures that, while known to yield coexisting lipid phases, are not detected with calorimetry or densitometry. These results indicate that capacitance is exquisitely sensitive to low-enthalpy membrane transitions because of its sensitivity to changes in bilayer thickness that occur when lipids and excess solvent undergo subtle rearrangements near a phase transition. Our findings also suggest that heterogeneity confers stability to natural membranes that function near

  10. Facing the challenge of predicting the standard formation enthalpies of n-butyl-phosphate species with ab initio methods.

    Science.gov (United States)

    Saab, Mohamad; Réal, Florent; Šulka, Martin; Cantrel, Laurent; Virot, François; Vallet, Valérie

    2017-06-28

    Tributyl-phosphate (TBP), a ligand used in the PUREX liquid-liquid separation process of spent nuclear fuel, can form an explosive mixture in contact with nitric acid that might lead to a violent explosive thermal runaway. In the context of safety of a nuclear reprocessing plant facility, it is crucial to predict the stability of TBP at elevated temperatures. So far, only the enthalpies of formation of TBP are available in the literature with rather large uncertainties, while those of its degradation products, di-(HDBP) and mono-(H2MBP), are unknown. In this goal, we have used state-of-the art quantum chemical methods to compute the formation enthalpies and entropies of TBP and its degradation products di-(HDBP) and mono-(H2MBP) in gas and liquid phases. Comparisons of levels of quantum chemical theory revealed that there are significant effects of correlation on their electronic structures, pushing for the need of not only high level of electronic correlation treatment, namely, local coupled cluster with single and double excitation operators and perturbative treatment of triple excitations, but also extrapolations to the complete basis to produce reliable and accurate thermodynamics data. Solvation enthalpies were computed with the conductor-like screening model for real solvents [COSMO-RS], for which we observe errors not exceeding 22 kJ mol(-1). We thus propose with final uncertainty of about 20 kJ mol(-1) standard enthalpies of formation of TBP, HDBP, and H2MBP which amounts to -1281.7 ± 24.4, -1229.4 ± 19.6, and -1176.7 ± 14.8 kJ mol(-1), respectively, in the gas phase. In the liquid phase, the predicted values are -1367.3 ± 24.4, -1348.7 ± 19.6, and -1323.8± 14.8 kJ mol(-1), to which we may add about -22 kJ mol(-1) error from the COSMO-RS solvent model. From these data, the complete hydrolysis of TBP is predicted as an exothermic phenomena but showing a slightly endergonic process.

  11. Facing the challenge of predicting the standard formation enthalpies of n-butyl-phosphate species with ab initio methods

    Science.gov (United States)

    Saab, Mohamad; Réal, Florent; Šulka, Martin; Cantrel, Laurent; Virot, François; Vallet, Valérie

    2017-06-01

    Tributyl-phosphate (TBP), a ligand used in the PUREX liquid-liquid separation process of spent nuclear fuel, can form an explosive mixture in contact with nitric acid that might lead to a violent explosive thermal runaway. In the context of safety of a nuclear reprocessing plant facility, it is crucial to predict the stability of TBP at elevated temperatures. So far, only the enthalpies of formation of TBP are available in the literature with rather large uncertainties, while those of its degradation products, di-(HDBP) and mono-(H2MBP), are unknown. In this goal, we have used state-of-the art quantum chemical methods to compute the formation enthalpies and entropies of TBP and its degradation products di-(HDBP) and mono-(H2MBP) in gas and liquid phases. Comparisons of levels of quantum chemical theory revealed that there are significant effects of correlation on their electronic structures, pushing for the need of not only high level of electronic correlation treatment, namely, local coupled cluster with single and double excitation operators and perturbative treatment of triple excitations, but also extrapolations to the complete basis to produce reliable and accurate thermodynamics data. Solvation enthalpies were computed with the conductor-like screening model for real solvents [COSMO-RS], for which we observe errors not exceeding 22 kJ mol-1. We thus propose with final uncertainty of about 20 kJ mol-1 standard enthalpies of formation of TBP, HDBP, and H2MBP which amounts to -1281.7 ± 24.4, -1229.4 ± 19.6, and -1176.7 ± 14.8 kJ mol-1, respectively, in the gas phase. In the liquid phase, the predicted values are -1367.3 ± 24.4, -1348.7 ± 19.6, and -1323.8± 14.8 kJ mol-1, to which we may add about -22 kJ mol-1 error from the COSMO-RS solvent model. From these data, the complete hydrolysis of TBP is predicted as an exothermic phenomena but showing a slightly endergonic process.

  12. A novel predictive model for formation enthalpies of Si and Ge hydrides with propane- and butane-like structures.

    Science.gov (United States)

    Weng, C; Kouvetakis, J; Chizmeshya, A V G

    2011-04-15

    Butane- and propane-like silicon-germanium hydrides and chlorinated derivatives represent a new class of precursors for the fabrication of novel metastable materials at low-temperature regimes compatible with selective growth and commensurate with the emerging demand for the reduced thermal budgets of complementary metal oxide semiconductor integration. However, predictive simulation studies of the growth process and reaction mechanisms of these new compounds, needed to accelerate their deployment and fine-tune the unprecedented low-temperature and low-pressure synthesis protocols, require experimental thermodynamic data, which are currently unavailable. Furthermore, traditional quantum chemistry approaches lack the accuracy needed to treat large molecules containing third-row elements such as Ge. Accordingly, here we develop a method to accurately predict the formation enthalpy of these compounds using atom-wise corrections for Si, Ge, Cl, and H. For a test set of 15 well-known hydrides of Si and Ge and their chlorides, such as Si(3)H(8), Ge(2)H(6), SiGeH(6), SiHCl(3), and GeCl(4), our approach reduces the deviations between the experimental and predicted formation enthalpies obtained from complete basis set (CBS-QB3), G2, and B3LPY thermochemistry to levels of 1-3 kcal/mol, or a factor of ∼5 over the corresponding uncorrected values. We show that our approach yields results comparable or better than those obtained using homodesmic reactions while circumventing the need for thermochemical data of the associated reaction species. Optimized atom-wise corrections are then used to generate accurate enthalpies of formation for 39 pure Si-Ge hydrides and a selected group of 20 chlorinated analogs, of which some have recently been synthesized for the first time. Our corrected enthalpies perfectly reproduce the experimental stability trends of heavy butane-like compounds containing Ge. This is in contrast to the direct application of the CBS-QB3 method, which yields

  13. Numerical simulation of casting processes: coupled mould filling and solidification using VOF and enthalpy-porosity method

    Science.gov (United States)

    Richter, Ole; Turnow, Johann; Kornev, Nikolai; Hassel, Egon

    2017-06-01

    Within the scope of industrial casting applications a numerical model for the simultaneous mould filling and solidification process has been formulated, implemented in a finite volume code and successfully validated using analytical and experimental data. In order to account for the developing of free surface flow and the liquid/solid phase change, respectively, the volume-of-fluid and enthalpy-porosity method have been coupled under a volume averaging framework on a fixed Eulerian grid. The coupled method captures the basic physical effects of a combined mould filling and solidification process and provides a trustful method for comprehensive casting simulations.

  14. Enthalpy-Entropy Compensation in the Binding of Modulators at Ionotropic Glutamate Receptor GluA2

    DEFF Research Database (Denmark)

    Krintel, Christian; Francotte, Pierre; Pickering, Darryl S

    2016-01-01

    ligand binding domains and act by stabilizing the agonist-bound open-channel conformation. The driving forces behind the binding of these modulators can be significantly altered with only minor substitutions to the parent molecules. In this study, we show that changing the 7-fluorine substituent...... of 5 was examined with x-ray crystallography, showing that the only change compared to that of earlier compounds was the orientation of Ser-497 pointing toward the hydroxyl group of 5. The favorable enthalpy can be explained by the formation of a hydrogen bond from the side-chain hydroxyl group of Ser...

  15. Experimental characterization of meteoric material exposed to a high enthalpy flow in the Plasmatron

    Science.gov (United States)

    Zavalan, Luiza; Bariselli, Federico; Barros Dias, Bruno; Helber, Bernd; Magin, Thierry

    2017-04-01

    Meteoroids, disintegrated during their entry in the atmosphere, contribute massively to the input of cosmic metals to Earth. Yet, this phenomenon is not well understood. Experimental studies on meteor material degradation in high enthalpy facilities are scarce and often do not provide quantitative data which are necessary for the validation of the simulation tools. In this work, we tried to duplicate typical meteor flight conditions in a ground testing facility to analyze the thermo-chemical degradation mechanisms by reproducing the stagnation point region conditions. The VKI Plasmatron is one of the most powerful induction-coupled plasma wind-tunnels in the world. It represents an important tool for the characterization of ceramic and ablative materials employed in the fabrication of Thermal Protection Systems (TPS) of spacecraft. The testing methodology and measurement techniques used for TPS characterization were adapted for the investigation of evaporation and melting in samples of basalt (meteorite surrogate) and ordinary chondrite. The materials were exposed to stagnation point heat fluxes of 1 MW/m2 and 3 MW/m2. During the test, numerous local pockets were formed at the surface of the samples by the emergence of gas bubbles. Images recorded through a digital 14bit CCD camera system clearly revealed the frothing of the surface for both tested materials. This process appeared to be more heterogeneous for the basaltic samples than for the ordinary chondritic material. Surface temperature measurements obtained via a two-color pyrometer showed a maximum surface temperature in the range between 2160 and 2490 Kelvins. Some of the basaltic samples fractured during the tests. This is probably due to the strong thermal gradients experienced by the material in these harsh conditions. Therefore, the surface temperature measurements suffered sudden drops in correspondence with the fracturing time. Emission spectra of air and ablated species were collected with resolution

  16. A thermodynamic study of glucose and related oligomers in aqueous solution: Vapor pressures and enthalpies of mixing

    DEFF Research Database (Denmark)

    Cooke, S.A.; Jonsdottir, Svava Osk; Westh, Peter

    2002-01-01

    -mentioned systems at 318.15 K. A theoretical model is examined in which existing interaction parameters, calculated for the water + 1,2-ethanediol system by using a molecular mechanical approach, are incorporated into the UNIQUAC equation to describe the vapor pressures of the aforementioned series of saccharides...

  17. The CPA Equation of State and an Activity Coefficient Model for Accurate Molar Enthalpy Calculations of Mixtures with Carbon Dioxide and Water/Brine

    Energy Technology Data Exchange (ETDEWEB)

    Myint, P. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hao, Y. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Firoozabadi, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-03-27

    Thermodynamic property calculations of mixtures containing carbon dioxide (CO2) and water, including brines, are essential in theoretical models of many natural and industrial processes. The properties of greatest practical interest are density, solubility, and enthalpy. Many models for density and solubility calculations have been presented in the literature, but there exists only one study, by Spycher and Pruess, that has compared theoretical molar enthalpy predictions with experimental data [1]. In this report, we recommend two different models for enthalpy calculations: the CPA equation of state by Li and Firoozabadi [2], and the CO2 activity coefficient model by Duan and Sun [3]. We show that the CPA equation of state, which has been demonstrated to provide good agreement with density and solubility data, also accurately calculates molar enthalpies of pure CO2, pure water, and both CO2-rich and aqueous (H2O-rich) mixtures of the two species. It is applicable to a wider range of conditions than the Spycher and Pruess model. In aqueous sodium chloride (NaCl) mixtures, we show that Duan and Sun’s model yields accurate results for the partial molar enthalpy of CO2. It can be combined with another model for the brine enthalpy to calculate the molar enthalpy of H2O-CO2-NaCl mixtures. We conclude by explaining how the CPA equation of state may be modified to further improve agreement with experiments. This generalized CPA is the basis of our future work on this topic.

  18. Low-cost low-enthalpy geothermal heat for freshwater production: Innovative applications using thermal desalination processes

    KAUST Repository

    Bundschuh, Jochen

    2015-03-01

    The study is dedicated to exploring different types of low-cost low-enthalpy geothermal and their potential integration with conventional thermal-based water desalination and treatment technologies to deliver energy efficient, environmentally friendly solutions for water desalination and treatment, addressing global water crises. Our in-depth investigation through reviews of various low-enthalpy geothermal and conventional thermal-based technologies suggest that the geothermal option is superior to the solar option if low-cost geothermal heat is available because it provides a constant heat source in contrast to solar. Importantly, the stable heat source further allows up-scaling (> 1000 m3/day), which is not currently possible with solar. Solar-geothermal hybrid constellations may also be suitable in areas where both sources are available. The review also discovers that the innovative Membrane distillation (MD) process is very promising as it can be used for many different water compositions, salinity and temperature ranges. Either the geothermal water itself can be desalinated/treated or the geothermal heat can be used to heat feed water from other sources using heat exchangers. However, there are only few economic analyses for large-scale MD units and these are based on theoretical models using often uncertain assumptions resulting in a large variety of results.

  19. Interaction enthalpies of solid human serum albumin with water-dioxane mixtures: comparison with water and organic solvent vapor sorption

    Energy Technology Data Exchange (ETDEWEB)

    Sirotkin, Vladimir A.; Faizullin, Djihanguir A

    2004-06-07

    Enthalpy changes ({delta}H{sub tot}) on the immersion of dehydrated human serum albumin (HSA) into water-dioxane mixtures have been measured using a Setaram BT-2.15 calorimeter at 298 K. Thermodynamic activity of water was varied from 0 to 1. Calorimetric results are discussed together with the FTIR-spectroscopic data on water and organic solvent vapor adsorption/desorption isotherms on solid HSA. Dioxane sorption exhibits a pronounced hysteresis. Calorimetric and dioxane desorption dependencies consist of two parts. No dioxane sorption was observed in low water activity region (a{sub w}<0.5). At low water activities, the {delta}H{sub tot} values are close to zero. At water activity about 0.5 the sharp exothermic drop of the interaction enthalpy values was observed. This exothermic drop is accompanied by the sharp increase in the amount of sorbed dioxane and additional water sorption (compared with that for pure water). Dioxane adsorption branch resembles a smooth curve. In this case, solid HSA binds more than 300 mol dioxane/mol HSA at low water activities. By using a water activity-based comparison we distinguished between dioxane-assisted and dioxane-competitive effect on water sorption. The obtained results demonstrate that the hydration 'history' of solid protein is an important factor that controls as the state of protein macromolecule as well as the sorption of low-molecular organic molecules.

  20. Influence of tribomechanical micronization and hydrocolloids addition on enthalpy and apparent specific heat of whey protein model solutions

    Directory of Open Access Journals (Sweden)

    Zoran Herceg

    2002-01-01

    Full Text Available Knowledge of thermophysical properties, especially the phase transitions temperature, specific heat and enthalpy, are essential in defining the freezing process parameters as well as storage conditions of frozen food. In this work thermophysical properties of 10% model solutions prepared with 60% whey protein concentrate (WPC with various hydrocolloids addition (HVEP, YO-EH, YO-L i YO-M were investigated. Powdered whey protein concentrate was treated in equipment for tribomechanical micronization and activation at 40000 rpm (Patent: PCT/1B99/00757 just before model solutions preparation. Particle size analysis was performed using Frich –laser particle sizer “analysette 22”. The phase transition temperatures were determined by differential thermal analysis (DTA, while specific heat and enthalpy were calculated according to several mathematical equations. The results have shown that, due to tribomechanical treatment, certain changes in thermophysical and energetic properties of materials occurred. Tribomechanical treatment affects changes in granulometrical composition of WPC which result in higher abilities of reactions with hydrocolloids in model solutions and significant changes in thermophysical properties of the mentioned models.

  1. Development of an enthalpy-based frozen soil model and its validation in a cold region in China

    Science.gov (United States)

    Bao, Huiyi; Koike, Toshio; Yang, Kun; Wang, Lei; Shrestha, Maheswor; Lawford, Peter

    2016-05-01

    An enthalpy-based frozen soil model was developed for the simulation of water and energy transfer in cold regions. To simulate the soil freezing/thawing processes stably and efficiently, a three-step algorithm was applied to solve the nonlinear governing equations: (1) a thermal diffusion equation was implemented to simulate the heat conduction between soil layers; (2) a freezing/thawing scheme used a critical temperature criterion to judge the phase status and introduced enthalpy and total water mass into freezing depression equation to represent ice formation/melt and corresponding latent heat release/absorption; and (3) a water flow scheme was employed to describe the liquid movement within frozen soil. In addition, a parameterization set of hydraulic and thermal properties was updated by considering the frozen soil effect. The performance of the frozen soil model was validated at point scale in a typical mountainous permafrost basin of China. An ice profile initialization method is proposed for permafrost modeling. Results show that the model can achieve a convergent solution at a time step of hourly and a surface layer thickness of centimeters that are typically used in current land surface models. The simulated profiles of soil temperature, liquid water content, ice content and thawing front depth are in good agreement with the observations and the characteristics of permafrost. The model is capable of continuously reproducing the diurnal and seasonal freeze-thaw cycle and simulating frozen soil hydrological processes.

  2. Development of a Water and Enthalpy Budget-based Glacier mass balance Model (WEB-GM) and its preliminary validation

    Science.gov (United States)

    Ding, Baohong; Yang, Kun; Yang, Wei; He, Xiaobo; Chen, Yingying; Lazhu; Guo, Xiaofeng; Wang, Lei; Wu, Hui; Yao, Tandong

    2017-04-01

    This paper presents a new water and energy budget-based glacier mass balance model. Enthalpy, rather than temperature, is used in the energy balance equations to simplify the computation of the energy transfers through the water phase change and the movement of liquid water in the snow. A new parameterization for albedo estimation and state-of-the-art parameterization schemes for rainfall/snowfall type identification and surface turbulent heat flux calculations are implemented in the model. This model was driven with meteorological data and evaluated using mass balance and turbulent flux data collected during a field experiment implemented in the ablation zone of the Parlung No. 4 Glacier on the Southeast Tibetan Plateau during 2009 and 2015-2016. The evaluation shows that the model can reproduce the observed glacier ablation depth, surface albedo, surface temperature, sensible heat flux, and latent heat flux with high accuracy. Comparing with a traditional energy budget-based glacier mass balance model, this enthalpy-based model shows a superior capacity in simulation accuracy. Therefore, this model can reasonably simulate the energy budget and mass balance of glacier melting in this region and be used as a component of land surface models and hydrological models.

  3. Gas-phase standard enthalpies of formation of urea-derived compounds: A quantum-chemical study

    Science.gov (United States)

    Gratzfeld, Dennis; Olzmann, Matthias

    2017-07-01

    Gas-phase standard enthalpies of formation of selected ureas and s-triazines were calculated at the CCSD(F12∗)(T)/cc-pVTZ-F12//ωB97X-D/cc-pVTZ level of theory by employing isodesmic reactions. The following values were obtained (T = 298.15 K, units: kJ mol-1, estimated confidence interval 95%): urea, -231.9 ± 2.8; biuret, -430.0 ± 4.5; triuret, -620.3 ± 6.3; cyanuric acid, -451.6 ± 6.3; ammelide, -303.9 ± 6.4; ammeline, -106.5 ± 6.2; melamine, 70.1 ± 7.0. The standard enthalpies of formation of methanimine and methylamine, which were required for the isodesmic reactions, were calculated from atomization reactions by using several variants of the HEAT approach. The following results were considered most reliable (T = 298.15 K, units: kJ mol-1, estimated confidence interval 95%): methanimine, 89.0 ± 1.0; methylamine, -20.7 ± 1.0.

  4. Formation enthalpies of LaLn'O3 (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

    Science.gov (United States)

    Qi, Jianqi; Guo, Xiaofeng; Mielewczyk-Gryn, Aleksandra; Navrotsky, Alexandra

    2015-07-01

    High-temperature oxide melt solution calorimetry using 3Na2O·MoO3 at 802 °C was performed for interlanthanide perovskites LaLn'O3 (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be -8.3±3.4 kJ/mol for LaHoO3, -9.9±3.0 kJ/mol for LaErO3, -10.8±2.7 kJ/mol for LaTmO3 and -12.3±2.9 kJ/mol for LaYbO3. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM3+O3 (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds.

  5. Low temperature heat capacities and standard molar enthalpy of formation of sodium benzoate C{sub 6}H{sub 5}COONa (s)

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Yu-Xia [College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, Shandong Province (China); Di, You-Ying, E-mail: yydi@lcu.edu.cn [College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, Shandong Province (China); Qi, Yu-Dong; Yang, Wei-Wei [College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, Shandong Province (China); Tan, Zhi-Cheng [Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2009-05-05

    Sodium benzoate was synthesized by the method of liquid phase synthesis, in which benzoic acid and anhydrous sodium carbonate were chosen as the reactants. The structure and composition of the compound were characterized by FTIR, chemical analysis, elemental analysis and X-ray powder diffraction techniques. Low temperature heat capacities of the compound were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of the heat capacities as a function of the temperature was fitted by least square method. The smoothed heat capacities and the thermodynamic functions of the compound relative to 298.15 K have been calculated based on the equation. In accordance with Hess law, the standard molar enthalpy of formation of the title compound C{sub 6}H{sub 5}COONa (s) was determined to be {Delta}{sub f}H{sup o}{sub m}[C{sub 6}H{sub 5}COONa,s]=-(642.56{+-}0.64)kJmol{sup -1} by using an isoperibol solution-reaction calorimeter.

  6. Spectroscopic investigation of the effect of salt on binding of tartrazine with two homologous serum albumins: quantification by use of the Debye-Hückel limiting law and observation of enthalpy-entropy compensation.

    Science.gov (United States)

    Bolel, Priyanka; Datta, Shubhashis; Mahapatra, Niharendu; Halder, Mintu

    2012-08-30

    Formation of ion pair between charged molecule and protein can lead to interesting biochemical phenomena. We report the evolution of thermodynamics of the binding of tartrazine, a negatively charged azo colorant, and serum albumins with salt. The dye binds predominantly electrostatically in low buffer strengths; however, on increasing salt concentration, affinity decreases considerably. The calculated thermodynamic parameters in high salt indicate manifestation of nonelectrostatic interactions, namely, van der Waals force and hydrogen bonding. Site-marker competitive binding studies and docking simulations indicate that the dye binds with HSA in the warfarin site and with BSA at the interface of warfarin and ibuprofen binding sites. The docked poses indicate nearby amino acid positive side chains, which are possibly responsible for electrostatic interaction. Using the Debye-Hückel interionic attraction theory for binding equilibria, it is shown that, for electrostatic binding the calculated free energy change increases linearly with square root of ionic strength. Also UV-vis, fluorescence, CD data indicate a decrease of interaction with salt concentration. This study quantitatively relates how ionic strength modulates the strength of the protein-ligand electrostatic interaction. The binding enthalpy and entropy have been found to compensate one another. The enthalpy-entropy compensation (EEC), general property of weak intermolecular interactions, has been discussed.

  7. Enthalpies of formation of layered LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} (0 ≤ x ≤ 0.5) compounds as lithium ion battery cathode materials

    Energy Technology Data Exchange (ETDEWEB)

    Masoumi, Maryam; Cupid, Damian M.; Reichmann, Thomas L.; Seifert, Hans J. [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Applied Materials - Applied Materials Physics; Chang, Keke; Music, Denis; Schneider, Jochen M. [RWTH Aachen Univ. (Germany). Materials Chemistry

    2017-11-15

    Layer-structured mixed transition metal oxides with the formula LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} (0 ≤ x ≤ 0.5) are considered as important cathode materials for lithium-ion batteries. In an effort to evaluate the relative thermodynamic stabilities of individual compositions in this series, the enthalpies of formation of selected stoichiometries are determined by high temperature oxide melt drop solution calorimetry and verified by ab-initio calculations. The measured and calculated data are in good agreement with each other, and the results show that LiCoO{sub 2}-LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} solid solution approaches ideal behavior. By increasing x, i.e. by equimolar substitution of Mn{sup 4+} and Ni{sup 2+} for Co{sup 3+}, the enthalpy of formation of LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} from the elements becomes more exothermic, implying increased energetic stability. This conclusion is in agreement with the literature results showing improved structural stability and cycling performance of Ni/Mn-rich LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} compounds cycled to higher cut-off voltages.

  8. Enthalpy and phase behavior of coal derived liquid mixtures: Technical progress report for the period January-March 1987. [M-cresol/quinoline/tetralin ternary mixture

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.

    1987-04-30

    On July 15, 1984, work was initiated on a program to study the enthalpy and phase behavior of coal derived liquid model compound mixtures. The objectives of this program are to study the enthalpy and phase behavior of a selected ternary model compound system, representative of interactions present in coal derived liquids. Measurements will be made in a Freon 11 reference fluid boil-off calorimeter, and an equilibrium flash vaporization apparatus. These experimental systems have already been developed. Previous studies have indicated that existing data and correlations developed for petroleum fluids are not applicable to coal derived liquids. This is due to the presence of significant concentrations of polar associating heteroatomics in the predominantly aromatic coal liquids. Thus, the ternary system will include an aromatic, a basic nitrogen compound, and a cresol. It is presently planned to study the m-cresol/quinoline/tetralin ternary mixture. Measurements will be made over a wide range of temperature (200 to 750/sup 0/F) and pressure (20 to 1500 psia), for the three pure compounds, the three binary mixtures and selected compositions of the ternary. Both enthalpy and phase behavior measurements will be made. This set of data will be useful as a standard for fitting and evaluating thermodynamic correlations and equations of state that are applicable to associating fluid mixtures, and thus to coal derived liquids. In particular we will attempt to fit both the enthalpy and phase behavior data with a single equation of state using local composition mixing rules and common interaction parameters. During the eleventh quarter, enthalpy measurements have been obtained for the ternary mixtures of m-cresol/quinoline/tetralin with molar ratios 2/3:1/6:1/6 and 1/6:2/3:1/6 m-cresol:quinoline:tetralin. The results are presented in Appendix A. The project has progressed very will during this quarter, and the enthalpy measurements have been completed. 2 refs., 2 figs., 2 tabs.

  9. Excess enthalpy, density, and speed of sound determination for the ternary mixture (methyl tert-butyl ether + 1-butanol + n-hexane)

    Energy Technology Data Exchange (ETDEWEB)

    Mascato, Eva [Departamento de Fisica Aplicada, Facultade de Ciencias, Universidade de Vigo, E-36310 Vigo (Spain); Mariano, Alejandra [Laboratorio de Fisicoquimica, Departamento de Quimica, Facultad de Ingenieria, Universidad Nacional del Comahue, 8300 Neuquen (Argentina); Pineiro, Manuel M. [Departamento de Fisica Aplicada, Facultade de Ciencias, Universidade de Vigo, E-36310 Vigo (Spain)], E-mail: mmpineiro@uvigo.es; Legido, Jose Luis [Departamento de Fisica Aplicada, Facultade de Ciencias, Universidade de Vigo, E-36310 Vigo (Spain); Paz Andrade, M.I. [Departamento de Fisica Aplicada, Facultade de Fisica, Universidade de Santiago de Compostela, E-15706 Santiago de Compostela (Spain)

    2007-09-15

    Density, ({rho}), and speed of sound, (u), from T = 288.15 to T = 308.15 K, and excess molar enthalpies, (h{sup E}) at T = 298.15 K, have been measured over the entire composition range for (methyl tert-butyl ether + 1-butanol + n-hexane). In addition, excess molar volumes, V{sup E}, and excess isentropic compressibility, {kappa}{sub s}{sup E}, were calculated from experimental data. Finally, experimental excess enthalpies results are compared with the estimations obtained by applying the group-contribution models of UNIFAC (in the versions of Dang and Tassios, Larsen et al., Gmehling et al.), and DISQUAC.

  10. Numerical study of the short pre-arcing time in high breaking capacity fuses via an enthalpy formulation

    Energy Technology Data Exchange (ETDEWEB)

    Rochette, David [Laboratoire Arc Electrique et Plasmas thermiques, CNRS UMR 6069, Universite Blaise Pascal-IUT de Montlucon, Avenue Aristide Briand, BP 2235, 03101 Montlucon Cedex (France); Touzani, Rachid [Laboratoire de Mathematiques, CNRS UMR 6620, Universite Blaise Pascal (Clermont-Ferrand II), Campus Universitaire des Cezeaux, 63177 Aubiere Cedex (France); Bussiere, William [Laboratoire Arc Electrique et Plasmas thermiques, CNRS UMR 6069, Universite Blaise Pascal-IUT de Montlucon, Avenue Aristide Briand, BP 2235, 03101 Montlucon Cedex (France)

    2007-08-07

    In order to study the short pre-arcing time in high breaking capacity (HBC) fuses, we use a mathematical model including the phase change of the fuse-element heating coupled with the Laplace equation for the potential and Ohm's law. The thermal model is based on the enthalpy formulation of the heat equation with a source term representing the Joule heating. For the time range considered (up to 10 ms), we assume no heat transfer between the fuse-element and the surrounding sand. To solve numerically the governing equations, we employ a semi-implicit scheme for time integration and a finite element method for space discretization. Using electrical and thermal properties of the silver fuse-element, we present pre-arcing characteristics (temperature, current density, potential) for a fuse-element used in industrial protection circuits.

  11. Thermal-Economic Modularization of Small, Organic Rankine Cycle Power Plants for Mid-Enthalpy Geothermal Fields

    Directory of Open Access Journals (Sweden)

    Yodha Y. Nusiaputra

    2014-07-01

    Full Text Available The costs of the surface infrastructure in mid-enthalpy geothermal power systems, especially in remote areas, could be reduced by using small, modular Organic Rankine Cycle (ORC power plants. Thermal-economic criteria have been devised to standardize ORC plant dimensions for such applications. We designed a modular ORC to utilize various wellhead temperatures (120–170 °C, mass flow rates and ambient temperatures (−10–40 °C. A control strategy was developed using steady-state optimization, in order to maximize net power production at off-design conditions. Optimum component sizes were determined using specific investment cost (SIC minimization and mean cashflow (MCF maximization for three different climate scenarios. Minimizing SIC did not yield significant benefits, but MCF proved to be a much better optimization function.

  12. Ground Thermal Diffusivity Calculation by Direct Soil Temperature Measurement. Application to very Low Enthalpy Geothermal Energy Systems.

    Science.gov (United States)

    Andújar Márquez, José Manuel; Martínez Bohórquez, Miguel Ángel; Gómez Melgar, Sergio

    2016-02-29

    This paper presents a methodology and instrumentation system for the indirect measurement of the thermal diffusivity of a soil at a given depth from measuring its temperature at that depth. The development has been carried out considering its application to the design and sizing of very low enthalpy geothermal energy (VLEGE) systems, but it can has many other applications, for example in construction, agriculture or biology. The methodology is simple and inexpensive because it can take advantage of the prescriptive geotechnical drilling prior to the construction of a house or building, to take at the same time temperature measurements that will allow get the actual temperature and ground thermal diffusivity to the depth of interest. The methodology and developed system have been tested and used in the design of a VLEGE facility for a chalet with basement at the outskirts of Huelva (a city in the southwest of Spain). Experimental results validate the proposed approach.

  13. Enthalpy of Formation of CH3SO and CH3SO2: A Difficult Case in Quantum Chemistry

    Directory of Open Access Journals (Sweden)

    Resende Stella M.

    2002-01-01

    Full Text Available The enthalpies of formation of CH3SO and CH3SO2 at 298.15 K were determined at a high level of electronic correlation, CCSD(T, and with the use of Woon and Dunning's procedure to reach the complete basis set limit. This study led to values of fraction three-quarters16.7 kcal mol-1 and fraction three-quarters53.1 kcal mol-1, respectively, for CH3SO and CH3SO2, which are expected to be the most accurate ones to date. Analysis of existing calculations at various levels of theory clearly shows the need of large basis sets and a high level of electronic correlation treatment to produce reliable and accurate results.

  14. Measurement of the enthalpy of formation of an iron pico-hydride and of its main properties

    Science.gov (United States)

    Dufour, Jacques; Dufour, Xavier; Dioury, Fabienne; Vinko, Jenny D.

    2017-10-01

    Chemical reactions result from the outside shell electrons of the reacting species being shared in various types of combinations. Typical distances involved are tenths of nm, resulting in binding energies typically in the order of hundreds of kJ/mole (eV/atom). The synthesis of a novel “atomic system” formed from Iron and di-Hydrogen has been achieved. The measured enthalpy of formation is some 40 MJ/moleFe and the distance between the hydrogen proton and the iron nucleus is some 8 pm, hence the proposed name: Iron Pico-Hydride. This compound is a permanent electric dipole of atomic size. Pico-Hydrides could, thus, play a significant role in HT superconductivity and in super-capacitors. The synthesis is compatible with the standard model.

  15. Calculation methods for sorption heat pumps using enthalpy-concentration charts. Beraekningsmetoder foer sorptionsvaermepumpar i entalpi-koncentrationsdiagram

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, K.; Jernqvist, Aa.

    1986-06-01

    Calculation methods for absorption heat pumps and heat transformers are described and graphically demonstrated in enthalpy-concentration charts. Special attention is payed to the estimation of pressures, temperatures, heat factor and circulation ratio. Every unit involved - generator/rectifier, absorber, condenser, heat exchangers, pumps and expansion valves - described in detail. Mass- and energy flows are graphically calculated. Efficiencies, especially for absorber and generator, are based only on temperatures. These efficiencies take into consideration the varying absorber and generator temperatures which should be exploited. Approximate values of temperature differences, circulation ratio, heat factor and efficiencies for different running conditions are given. Calculation examples for the absorption heat pump as well as the heat transformer illustrate the graphical method, which is especially suitable for preliminary calculations such as for instance pre-projecting. (authors).

  16. Ground Thermal Diffusivity Calculation by Direct Soil Temperature Measurement. Application to very Low Enthalpy Geothermal Energy Systems

    Directory of Open Access Journals (Sweden)

    José Manuel Andújar Márquez

    2016-02-01

    Full Text Available This paper presents a methodology and instrumentation system for the indirect measurement of the thermal diffusivity of a soil at a given depth from measuring its temperature at that depth. The development has been carried out considering its application to the design and sizing of very low enthalpy geothermal energy (VLEGE systems, but it can has many other applications, for example in construction, agriculture or biology. The methodology is simple and inexpensive because it can take advantage of the prescriptive geotechnical drilling prior to the construction of a house or building, to take at the same time temperature measurements that will allow get the actual temperature and ground thermal diffusivity to the depth of interest. The methodology and developed system have been tested and used in the design of a VLEGE facility for a chalet with basement at the outskirts of Huelva (a city in the southwest of Spain. Experimental results validate the proposed approach.

  17. Fundamental and overtone vibrational spectroscopy, enthalpy of hydrogen bond formation and equilibrium constant determination of the methanol-dimethylamine complex.

    Science.gov (United States)

    Du, Lin; Mackeprang, Kasper; Kjaergaard, Henrik G

    2013-07-07

    We have measured gas phase vibrational spectra of the bimolecular complex formed between methanol (MeOH) and dimethylamine (DMA) up to about 9800 cm(-1). In addition to the strong fundamental OH-stretching transition we have also detected the weak second overtone NH-stretching transition. The spectra of the complex are obtained by spectral subtraction of the monomer spectra from spectra recorded for the mixture. For comparison, we also measured the fundamental OH-stretching transition in the bimolecular complex between MeOH and trimethylamine (TMA). The enthalpies of hydrogen bond formation (ΔH) for the MeOH-DMA and MeOH-TMA complexes have been determined by measurements of the fundamental OH-stretching transition in the temperature range from 298 to 358 K. The enthalpy of formation is found to be -35.8 ± 3.9 and -38.2 ± 3.3 kJ mol(-1) for MeOH-DMA and MeOH-TMA, respectively, in the 298 to 358 K region. The equilibrium constant (Kp) for the formation of the MeOH-DMA complex has been determined from the measured and calculated transition intensities of the OH-stretching fundamental transition and the NH-stretching second overtone transition. The transition intensities were calculated using an anharmonic oscillator local mode model with dipole moment and potential energy curves calculated using explicitly correlated coupled cluster methods. The equilibrium constant for formation of the MeOH-DMA complex was determined to be 0.2 ± 0.1 atm(-1), corresponding to a ΔG value of about 4.0 kJ mol(-1).

  18. Predicting permeability of low enthalpy geothermal reservoirs: A case study from the Upper Triassic − Lower Jurassic Gassum Formation, Norwegian–Danish Basin

    DEFF Research Database (Denmark)

    Weibel, Rikke; Olivarius, Mette; Kristensen, Lars

    2017-01-01

    This paper aims at improving the predictability of permeability in low enthalpy geothermal reser-voirs by investigating the effect of diagenesis on sandstone permeability. Applying the best fittedporosity–permeability trend lines, obtained from conventional core analysis, to log-interpreted poros...

  19. Standard Test Method for Calculation of Stagnation Enthalpy from Heat Transfer Theory and Experimental Measurements of Stagnation-Point Heat Transfer and Pressure

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This test method covers the calculation from heat transfer theory of the stagnation enthalpy from experimental measurements of the stagnation-point heat transfer and stagnation pressure. 1.2 Advantages 1.2.1 A value of stagnation enthalpy can be obtained at the location in the stream where the model is tested. This value gives a consistent set of data, along with heat transfer and stagnation pressure, for ablation computations. 1.2.2 This computation of stagnation enthalpy does not require the measurement of any arc heater parameters. 1.3 Limitations and ConsiderationsThere are many factors that may contribute to an error using this type of approach to calculate stagnation enthalpy, including: 1.3.1 TurbulenceThe turbulence generated by adding energy to the stream may cause deviation from the laminar equilibrium heat transfer theory. 1.3.2 Equilibrium, Nonequilibrium, or Frozen State of GasThe reaction rates and expansions may be such that the gas is far from thermodynamic equilibrium. 1.3.3 Noncat...

  20. Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k

    Directory of Open Access Journals (Sweden)

    K. L. Shivabasappa

    2008-03-01

    Full Text Available The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data obtained was in very good agreement with literature values. Experiments were then conducted for mixtures of Ethyl Acetate with Benzene and Toluene. The experimental data was fitted to the standard correlations and the constants were evaluated. Heat of vaporization data were obtained from a static apparatus and tested for accuracy by conducting experiments with a known system Benzene - n-Hexane and the data obtained were found to be in agreement with literature values. Experiments were then conducted to measure heat of vaporization for the mixtures of Ethyl Acetate with Benzene and Toluene. Using experimental data of enthalpy of mixing from the first phase, and heat capacity data, the heat of vaporization were calculated.

  1. Enthalpy measurement of coal-derived liquids. Final technical progress report. [200 to 740/sup 0/F and 200 to 1500 psia

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1981-05-01

    This final report presents the results of the enthalpy measurements on the model compound m-cresol. The measurements cover the temperature range 200 to 740/sup 0/F and the pressure range 200 to 1500 psia. These data are compared with earlier data taken on m-cresol and with other thermophysical properties taken from the literature.

  2. Properties of mixed-crystalline organic material prepared by zone levelling IV. Melting properties and excess enthalpies of (trans-azobenzene + trans-stilbene)

    NARCIS (Netherlands)

    Bouwstra, J.A.; Leeuw, V.V. de; Miltenburg, J.C.

    1985-01-01

    Homogeneous mixed crystals of (trans-azobenzene + trans-stilbene) were prepared. Molar heat capacities of the pure substances and the mixed crystals were determined at temperatures from 300 to 400 K. The melting temperatures and molar enthalpies of fusion were measured for trans-stilbene and

  3. Modelo de simulação de secagem de produtos agrícolas usando entalpia do ar constante Drying simulation model of agricultural products with constant air enthalpy

    Directory of Open Access Journals (Sweden)

    Valdecir A. Dalpasquale

    2010-08-01

    Full Text Available A simulação matemática de secagem de produtos agrícolas teve seu auge nas décadas de 1960 e 1970, com destaque para os modelos de Thompson e de Michigan. Entretanto, nenhum deles abordou a condição de entalpia constante do ar de secagem durante o processo, limitando-se a conferir se a umidade relativa do ar não excedia 100%. Estudos conduzidos na Universidade Estadual de Maringá permitiram concluir que os balanços de energia e de massa de um processo de secagem estão incluídos no uso da mesma entalpia do ar durante a secagem, ajustando-se, com ela, a umidade absoluta do ar em função da umidade removida do produto. Com essa nova razão da mistura do ar e com a entalpia constante, avalia-se a nova temperatura do ar de secagem na saída da camada e, com essas duas propriedades psicrométricas, a umidade relativa do ar. Se ela atingir a condição saturada, encerra-se o processo de secagem naquele tempo, a partir daquela posição. Os resultados obtidos por simulação foram conferidos com resultados experimentais de secagem de milho em camadas fixas, com elevada concordância entre eles.Mathematical drying simulation of agricultural products reached its highest point in the decades of 1960 and 1970, with prominence for MSU and Thompson's models. However, none of them used the constant enthalpy condition of drying air during the process, being limited to checking if the relative humidity of the air did not exceed 100%. Studies conducted in the State University of Maringá allowed to conclude that energy and mass balances of a drying process are included when using the same air enthalpy in such process. The absolute humidity of the air is adjusted as a function of the removed humidity of the product. With that new absolute humidity of the air and with the constant enthalpy, the new temperature of the drying air is evaluated in the exit of the layer and, with those two psychrometric properties, the relative humidity of the air. If it

  4. Enthalpy of dilution of poly(ethylene glycol) monomethyl ether in 1-butanol

    Science.gov (United States)

    Wohlfarth, Ch.

    This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

  5. Enthalpy of dilution of poly(ethylene glycol) in 1-butanol

    Science.gov (United States)

    Wohlfarth, Ch.

    This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

  6. Enthalpy of dilution of poly(1-vinyl-2-pyrrolidinone) in 1-butanol

    Science.gov (United States)

    Wohlfarth, Ch.

    This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

  7. The Link between Fluid Flow, Structure and Hydrothermal Inputs in Central Chile: An Interdisciplinary Approach for Low-Enthalpy Andean Hydrogeothermal Modeling

    Science.gov (United States)

    Arancibia, G.; Daniele, L.; Navarro, L.; Astudillo, F.; Vázquez, M.; Morata, D.

    2014-12-01

    The interaction between fault zones and hydrogeological domains are an open challenge and require the understanding of the complex relationship between structure, fluid flow and hydrothermal transport and processes. Faults stimulate hydraulic conductivity when acting as conduit, but it can also be a barrier by mineral precipitation and comminution. Structural heterogeneity of fractured lithology induces a flow partition within the aquifer system creating preferential flows paths and some fracture connectivity. We propose an interdisciplinary approach from hydrogeological and structural point of view, in a low-enthalpy aquifer system in the central valley of Central Chile, where several low-temperature thermal springs are spatially related to regional long-lived fault zone (Pocuro Fault Zone). Pocuro Fault zone is a kilometric NS-striking steeply dipping fault zone, with at least 50 km long. Metric wide fault core includes gouge and cataclastic rocks, whereas decametric damage zone consists of intensely fractured and hydrothermal altered Meso-Cenozoic volcanic and volcaniclastic host rocks, crossed by centimetric to milimetric subvertical NE-striking veins. Preliminary results of vein infill clays minerals and zeolites from damage zone, suggest P-T conditions interpreted as an exhumed fossil high-temperature (120º-230ºC) geothermal system. Currently, only low-temperature thermal springs are discharging with different geochemical patterns (bicarbonate to chlorine and sulphate dominant ions) and a homogeneous temperature range (20º-25ºC). This is an interesting study case, to better understand the permeability evolution of geothermal system and the link between internal fault architecture, hydrogeology and hydrothermal inputs.

  8. Determination of the free enthalpies of formation of borosilicate glasses; Determination des enthalpies libres de formation des verres borosilicates. Application a l'etude de l'alteration des verres de confinement de dechets radioactifs

    Energy Technology Data Exchange (ETDEWEB)

    Linard, Y

    2000-07-01

    This work contributes to the study of the thermochemical properties of nuclear waste glasses. Results are used to discuss mechanisms and parameters integrated in alteration models of conditioning materials. Glass is a disordered material defined thermodynamically as a non-equilibrium state. Taking into account one order parameter to characterise its configurational state, the metastable equilibrium for the glass was considered and the main thermochemical properties were determined. Calorimetric techniques were used to measure heat capacities and formation enthalpies of borosilicate glasses (from 3 to 8 constitutive oxides). Formation Entropies were measured too, using the entropy theory of relaxation processes proposed by Adam and Gibbs (1965). The configurational entropy contribution were determined from viscosity measurements. This set of data has allowed the calculation of Gibb's free energies of dissolution of glasses in pure water. By comparison with leaching experiments, it has been demonstrated that the decreasing of the dissolution rate at high reaction progress cannot be associated to the approach of an equilibrium between the sound glass and the aqueous solution. The composition changes of the reaction area at the glass surface need to be considered too. To achieve a complete description of the thermodynamic stability, the equilibrium between hydrated de-alkalinized glass and/or the gel layer with the aqueous solution should also be evaluated. (author)

  9. Entropy and enthalpy of interaction between amino acid side chains in nanopores

    CERN Document Server

    Vaitheeswaran, S

    2014-01-01

    Understanding the stabilities of proteins in nanopores requires a quantitative description of confinement induced interactions between amino acid side chains. We use molecular dynamics simulations to study the nature of interactions between the side chain pairs ALA-PHE, SER-ASN and LYS-GLU in bulk water and in water-filled nanopores. The temperature dependence of the bulk solvent potentials of mean force and the interaction free energies in cylindrical and spherical nanopores is used to identify the corresponding entropic and enthalpic components. The entropically stabilized hydrophobic interaction between ALA and PHE in bulk water is enthalpically dominated upon confinement depending on the relative orientations between the side chains. In the case of SER-ASN, hydrogen bonded configurations that are similar in bulk water are thermodynamically distinct in a cylindrical pore, thus making rotamer distributions different from those in the bulk. Remarkably, salt bridge formation between LYS-GLU is stabilized by e...

  10. Excess enthalpies of the ternary mixtures: {l_brace}tetrahydrofuran + 3-methylpentane + (octane or decane){r_brace} at the temperature 298.15 K[Excess enthalpy; Ternary mixture; Tetrahydrofuran; 3-Methylpentane; n-Octane; n-Decane; Liebermann-Fried model

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhaohui; Benson, George C. E-mail: gbenson@eng.uottawa.ca; Lu, Benjamin C.-Y

    2003-10-01

    Measurements of excess molar enthalpies at the temperature 298.15 K in a flow microcalorimeter, are reported for the two ternary mixtures {l_brace}X{sub 1}C{sub 4}H{sub 8}O + X{sub 2}CH{sub 3}CH{sub 2}CH(CH{sub 3})CH{sub 2}CH{sub 3} + (1-X{sub 1}-X{sub 2})CH{sub 3}(CH{sub 2}){sub v-2}CH{sub 3}{r_brace} with v=8 and 10. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann-Fried model, using only the physical properties of the components and their binary mixtures.

  11. Incineration of animal by-products--The impact of selected parameters on the flux of flue gas enthalpy.

    Science.gov (United States)

    Bujak, Janusz; Sitarz, Piotr

    2016-04-01

    This paper presents model analyses and tests of animal by-product waste thermal treatment plants. A schedule of tests was prepared, and 62,024 cases of system operation were analysed. A map/work field of the tested plant was drawn up on the basis thereof. Calculations were made following an algorithm described by Bujak (2015a) written in the VBA (Visual Basic for Application) language. The tests showed that when incinerating animal waste, the flux of physical enthalpy of the flue gas from the afterburner chamber depends on numerous design and operating parameters. The most important include the following: humidity and flux of the waste, concentration of oxygen in the flue gas in the afterburner chamber and loss of heat flux to the atmosphere through the external surfaces of the plant. Individual design and operating parameters can be selected so that the process of incineration is ensured without additional fuel. The performed analyses were verified against the actual object at the industrial scale using a meat plant that manufactures ham and processes beef, pork and poultry with a capacity of 150 tonnes/day. The production process waste included mainly bones and - in much smaller quantities - meat and bone meal, at 17 tonnes/day. The performed tests and analyses can be used to optimise the operation of the waste thermal treatment plant at the stages of design and operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Calorimetric vs. van't Hoff binding enthalpies from isothermal titration calorimetry: Ba2+-crown ether complexation.

    Science.gov (United States)

    Mizoue, Laura S; Tellinghuisen, Joel

    2004-07-01

    The 1:1 complexation reaction between Ba(2+) and 18-crown-6 ether is re-examined using isothermal titration calorimetry (ITC), with the goal of clarifying previously reported discrepancies between reaction enthalpies estimated directly (calorimetric) and indirectly, from the temperature dependence of the reaction equilibrium constant K (van't Hoff). The ITC thermograms are analyzed using three different non-linear fit models based on different assumptions about the data error: constant, proportional to the heat and proportional but correlated. The statistics of the fitting indicate a preference for the proportional error model, in agreement with expectations for the conditions of the experiment, where uncertainties in the delivered titrant volume should dominate. With attention to proper procedures for propagating statistical error in the van't Hoff analysis, the differences between Delta H(cal) and Delta H(vH) are deemed statistically significant. In addition, statistically significant differences are observed for the Delta H(cal) estimates obtained for two different sources of Ba(2+), BaCl(2) and Ba(NO(3))(2). The effects are tentatively attributed to deficiencies in the standard procedure in ITC of subtracting a blank obtained for pure titrant from the thermogram obtained for the sample.

  13. Excess enthalpies of mixing of piperidinium ionic liquids with short-chain alcohols: measurements and PC-SAFT modeling.

    Science.gov (United States)

    Paduszyński, Kamil; Królikowski, Marek; Domańska, Urszula

    2013-04-11

    This work is a continuation of our systematic study on thermodynamic properties of 1-n-alkyl-1-methylpiperdinium bis[(trifluoromethyl)sulfonyl]imides homologous series of ionic liquids ([CnC1Pip][NTf2]). Excess enthalpies of mixing (H(E)) of four binary systems containing two ionic liquids, namely [C4C1Pip][NTf2] and [C6C1Pip][NTf2], and two short-chain alcohols, namely ethanol and 1-propanol, were measured by isothermal titration calorimetry. Alcohol-to-ionic liquid and ionic liquid-to-alcohol titration experiments were carried out at temperature T = 298.15 K and atmospheric pressure. The experimental data were modeled in terms of perturbed-chain statistical associating fluid theory (PC-SAFT). Wolbach-Sandler combining rules were adopted in order to account for ionic liquid-alcohol cross-association. The model was applied in a conventional manner (i.e., without any binary corrections) as well as in a novel predictive mode developed previously by our group [Paduszyński, K.; Domańska, U. J. Phys. Chem. B 2012, 116, 5002-5018; Domańska et al. J. Phys. Chem. B 2012, 116, 8191-8200]. The latter approach employs temperature-dependent binary correction fitted to experimental limiting activity coefficient of alcohol in ionic liquid.

  14. Enthalpy and phase behavior of coal derived liquid mixtures: Final technical report. [Tetralin/m-cresol/quinoline

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Kidnay, A.J.; Flanigan, D.A.; Niesen, V.G.; DiGiacinto, S.S.; Joyce, T.P.; Yanaki, J.S.

    1988-04-15

    Measurements were made in a Freon 11, reference fluid, boil-off calorimeter, and an equilibrium flash vaporization apparatus, experimental systems which had already been developed. Previous studies had indicated that existing data and correlations developed for petroleum fluids are not applicable to coal derived liquids. This was due to the presence of significant concentrations of polar associating heteroatomics in the predominantly aromatic coal liquids. Thus, the ternary system was selected to include an aromatic, a basic nitrogen compound, and a cresol. Measurements were made over a wide range of temperature (200 to 700/degrees/) and pressure (20 to 1500 psia), for the three pure compounds, the three binary mixtures and selected compositions of the ternary. Both enthalpy and phase behavior measurements were made. This set of data will be useful as a standard for fitting and evaluating thermodynamic correlations and equations of state that are applicable to associating fluid mixtures, and thus to coal derived liquids. In addition efforts were and continue to be made at developing equation of state correlations which are applicable to these highly nonideal mixtures. 46 refs., 43 figs., 41 tabs.

  15. Degradation of carbon-based materials under ablative conditions produced by a high enthalpy plasma jet

    Directory of Open Access Journals (Sweden)

    Gilberto Petraconi

    2010-04-01

    Full Text Available A stationary experiment was performed to study the degradation of carbon-based materials by immersion in a plasma jet. In the experiment, graphite and C/C composite were chosen as the target materials, and the reactive plasma jet was generated by an air plasma torch. For macroscopic study of the material degradation, the sample’s mass losses were measured as function of the exposure time under various temperatures on the sample surface. A microscopic analysis was then carried out for the study of microscopic aspects of the erosion of material surface. These experiments showed that the mass loss per unit area is approximately proportional to the exposure time and strongly depends on the temperature of the material surface. The mass erosion rate of graphite was appreciably higher than the C/C composite. The ablation rate in the carbon matrix region in C/C composite was also noticeably higher than that in the fiber region. In addition, the latter varied according to the orientation of fibers relatively to the flow direction. These tests indicated an excellent ablation resistance of the C/C composite, thus being a reliable material for rocket nozzles and heat shielding elements of the protection systems of hypersonic apparatuses from aerodynamic heating.

  16. Cholesterol-induced variations in the volume and enthalpy fluctuations of lipid bilayers.

    Science.gov (United States)

    Halstenberg, S; Heimburg, T; Hianik, T; Kaatze, U; Krivanek, R

    1998-07-01

    The sound velocity and density of suspensions of large unilamellar liposomes from dimyristoylphosphatidylcholine with admixed cholesterol have been measured as a function of temperature around the chain melting temperature of the phospholipid. The cholesterol-to-phospholipid molar ratio xc has been varied over a wide range (0 relation between the compressibility and the excess heat capacity of the bilayer system has been derived. Comparison of the compressibilities (and sound velocity numbers) with heat capacity traces display the close correlation between these quantities for bilayer systems. This correlation appears to be very useful as it allows some of the mechanical properties of membrane systems to be calculated from the specific heat capacity data and vice versa.

  17. Controlling the adsorption enthalpy of CO(2) in zeolites by framework topology and composition.

    Science.gov (United States)

    Grajciar, Lukáš; Čejka, Jiří; Zukal, Arnošt; Otero Areán, Carlos; Turnes Palomino, Gemma; Nachtigall, Petr

    2012-10-01

    Zeolites are often investigated as potential adsorbents for CO(2) adsorption and separation. Depending on the zeolite topology and composition (Si/Al ratio and extra-framework cations), the CO(2) adsorption heats at low coverages vary from -20 to -60 kJ mol(-1), and with increasing surface coverage adsorption heats either stay approximately constant or they quickly drop down. Experimental adsorption heats obtained for purely siliceous porous solids and for ion-exchanged zeolites of the structural type MFI, FER, FAU, LTA, TUN, IMF, and -SVR are discussed in light of results of periodic density functional theory calculations corrected for the description of dispersion interactions. Key factors influencing the stability of CO(2) adsorption complexes are identified and discussed at the molecular level. A general model for CO(2) adsorption in zeolites and related materials is proposed and data reported in literature are evaluated with regard to the proposed model. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Enthalpy-entropy compensation for the solubility of drugs in solvent mixtures: paracetamol, acetanilide, and nalidixic acid in dioxane-water.

    Science.gov (United States)

    Bustamante, P; Romero, S; Pena, A; Escalera, B; Reillo, A

    1998-12-01

    In earlier work, a nonlinear enthalpy-entropy compensation was observed for the solubility of phenacetin in dioxane-water mixtures. This effect had not been earlier reported for the solubility of drugs in solvent mixtures. To gain insight into the compensation effect, the behavior of the apparent thermodynamic magnitudes for the solubility of paracetamol, acetanilide, and nalidixic acid is studied in this work. The solubility of these drugs was measured at several temperatures in dioxane-water mixtures. DSC analysis was performed on the original powders and on the solid phases after equilibration with the solvent mixture. The thermal properties of the solid phases did not show significant changes. The three drugs display a solubility maximum against the cosolvent ratio. The solubility peaks of acetanilide and nalidixic acid shift to a more polar region at the higher temperatures. Nonlinear van't Hoff plots were observed for nalidixic acid whereas acetanilide and paracetamol show linear behavior at the temperature range studied. The apparent enthalpies of solution are endothermic going through a maximum at 50% dioxane. Two different mechanisms, entropy and enthalpy, are suggested to be the driving forces that increase the solubility of the three drugs. Solubility is entropy controlled at the water-rich region (0-50% dioxane) and enthalpy controlled at the dioxane-rich region (50-100% dioxane). The enthalpy-entropy compensation analysis also suggests that two different mechanisms, dependent on cosolvent ratio, are involved in the solubility enhancement of the three drugs. The plots of deltaH versus deltaG are nonlinear, and the slope changes from positive to negative above 50% dioxane. The compensation effect for the thermodynamic magnitudes of transfer from water to the aqueous mixtures can be described by a common empirical nonlinear relationship, with the exception of paracetamol, which follows a separate linear relationship at dioxane ratios above 50%. The

  19. Economical Efficiency of Combined Cooling Heating and Power Systems Based on an Enthalpy Method

    Directory of Open Access Journals (Sweden)

    Yan Xu

    2017-11-01

    Full Text Available As the living standards of Chinese people have been improving, the energy demand for cooling and heating, mainly in the form of electricity, has also expanded. Since an integrated cooling, heating and power supply system (CCHP will serve this demand better, the government is now attaching more importance to the application of CCHP energy systems. Based on the characteristics of the combined cooling heating and power supply system, and the method of levelized cost of energy, two calculation methods for the evaluation of the economical efficiency of the system are employed when the energy production in the system is dealt with from the perspective of exergy. According to the first method, fuel costs account for about 75% of the total cost. In the second method, the profits from heating and cooling are converted to fuel costs, resulting in a significant reduction of fuel costs, accounting for 60% of the total cost. Then the heating and cooling parameters of gas turbine exhaust, heat recovery boiler, lithium-bromide heat-cooler and commercial tariff of provincial capitals were set as benchmark based on geographic differences among provinces, and the economical efficiency of combined cooling heating and power systems in each province were evaluated. The results shows that the combined cooling heating and power system is economical in the developed areas of central and eastern China, especially in Hubei and Zhejiang provinces, while in other regions it is not. The sensitivity analysis was also made on related influencing factors of fuel cost, demand intensity in heating and cooling energy, and bank loans ratio. The analysis shows that the levelized cost of energy of combined cooling heating and power systems is very sensitive to exergy consumption and fuel costs. When the consumption of heating and cooling energy increases, the unit cost decreases by 0.1 yuan/kWh, and when the on-grid power ratio decreases by 20%, the cost may increase by 0.1 yuan

  20. Experimental and Theoretical Study of the Enthalpy of Formation of 3,6-Diphenyl-1,2,4,5-Tetroxane Molecule

    Directory of Open Access Journals (Sweden)

    N.L. Jorge

    2002-01-01

    Full Text Available We report the results obtained for the experimental determination and the theoretical calculation of the enthalpy of formation of 3,6-diphenyl-1,2,4,5-tetroxane molecule. The experimental work was performed using a macrocalorimeter to measure the combustion heat, and the sublimation enthalpy was determined via the measurement of the vapor pressure at equilibrium with the vapor phase at different temperatures resorting to the Clapeyron-Claussius equation. Theoretical calculations were performed using semiempirical AM1 and PM3 methods as well as ab initio techniques at the 3-21, 6-31G(d,p, and 6-311G(d,p basis set levels.

  1. Subcontracted R and D final report: SRC-I phase equilibrium and enthalpy data for coal liquefaction and solvent recovery areas. Vol. 3

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, D.C.; Chu, I.C.; Kidnay, A.J.; Yesavage, V.F.

    1984-03-01

    The Enthalpy Program was a 20-month project initiated on January 18, 1982 by the International Coal Refining Company (ICRC) and under the technical direction of Professor Arthur J. Kidnay and Professor V.F. Yesavage at the Colorado School of Mines (CSM), Golden, Colorado. The objective of the program was to gather enthalpy data on representative pure model compounds, mixtures of model compounds, and selected coal-derived liquid samples furnished by ICRC. A copy of the technical agreement between ICRC and CSM is included in this report as Appendix A. This final report contains a complete description of the calorimeter and the experimental procedures used, separate data sections for each experimental task, and a copy of the technical agreement between ICRC and CSM. Data are presented for 11 coal liquid fractions. Each section of this report is organized to stand alone; thus, there are no general lists of references, tables of notation, or overall data tables.

  2. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, July--September 1977. [155 to 742 degrees F and 150, 200, 500, 1000 and 1500 psia

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1977-10-15

    Coal-derived liquids are a new and vital class of industrial compounds, but have thermodynamic properties that are largely unknown and, presently, unpredictable. The objective of this research is to measure one of the most important thermodynamic properties, the enthalpy, for representative coal-derived liquids over the pressure and temperature regions most likely to be encountered in both liquefaction and processing systems. Experimental measurements were made on a distillate from a coal-derived liquid sample produced with the Synthoil process. The measurements extend from 155 to 742/sup 0/F at pressures of 150, 200, 500, 1000, and 1500 psia. Enthalpy measurements were also started on a naphtha cut from a coal-derived liquid produced by the SRC-I process. These naphtha measurements are approximately 60 percent complete.

  3. Vapor-liquid equilibria and excess enthalpies for octane + N-methylacetamide, cyclooctane + N-methylacetamide, and octane + acetic acid anhydride at 125 C

    Energy Technology Data Exchange (ETDEWEB)

    Haan, A.B. de [DSM-Research, Geleen (Netherlands); Heine, A.; Fischer, K.; Gmehling, J. [Univ. Oldenburg (Germany)

    1995-11-01

    Isothermal P-x data and excess enthalpies have been measured at approximately 125 C for the binary mixtures of octane + N-methylacetamide, cyclooctane + N-methylacetamide, and octane + acetic anhydride. For each binary system linear temperature dependent interaction parameters were fitted to experimental data using the NRTL model. Activity coefficients at infinite dilution were derived from the P-x data at low concentrations using a flexible Legendre polynomial.

  4. Enthalpy Changes during Photosynthetic Water Oxidation Tracked by Time-Resolved Calorimetry Using a Photothermal Beam Deflection Technique☆☆☆

    Science.gov (United States)

    Krivanek, Roland; Dau, Holger; Haumann, Michael

    2008-01-01

    The energetics of the individual reaction steps in the catalytic cycle of photosynthetic water oxidation at the Mn4Ca complex of photosystem II (PSII) are of prime interest. We studied the electron transfer reactions in oxygen-evolving PSII membrane particles from spinach by a photothermal beam deflection technique, allowing for time-resolved calorimetry in the micro- to millisecond domain. For an ideal quantum yield of 100%, the enthalpy change, ΔH, coupled to the formation of the radical pair YZ⋅+QA− (where YZ is Tyr-161 of the D1 subunit of PSII) is estimated as −820 ± 250 meV. For a lower quantum yield of 70%, the enthalpy change is estimated to be −400 ± 250 meV. The observed nonthermal signal possibly is due to a contraction of the PSII protein volume (apparent ΔV of about −13 Å3). For the first time, the enthalpy change of the O2-evolving transition of the S-state cycle was monitored directly. Surprisingly, the reaction is only slightly exergonic. A value of ΔH(S3 ⇒ S0) of −210 meV is estimated, but also an enthalpy change of zero is within the error range. A prominent nonthermal photothermal beam deflection signal (apparent ΔV of about +42 Å3) may reflect O2 and proton release from the manganese complex, but also reorganization of the protein matrix. PMID:17993488

  5. Enthalpy and entropy changes for the intercalation of small molecules to DNA. I. substituted naphthalene monoimides and naphthalene diimides

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, H.P.; Stevenson, K.A.; Wilson, W.D.

    1986-07-01

    Calorimetric studies have been performed on the intercalation of a series of nitro and amino substituted naphthalene monoimide cations to calf thymus DNA. For comparison, we also included in the study the unsubstituted naphthalene diimide dication. All of the substituted naphthalene monoimides formed dimers at the concentrations used in the calorimetric titrations, and dimerization constants for these compounds were derived from spectroscopic studies and used in calculating the ..delta..H /SUP o/ /SUB B/ parameters from the calorimetric data. The dimerization constants increase in the order 3-NO/sub 2/MI = 4-NO/sub 2/MI > 3-NH/sub 2/MI > 4-NH/sub 2/MI. For the unsubstituted naphthalene monoimide and 3-NO/sub 2/MI and 4-NO/sub 2/MI, the ..delta..H /SUP o/ /SUB B/ parameters are within experimental error equal to that found for the naphthalene diimide, i.e., -4.3 kcal-mol/sup -1/. Thus, changes in entropy cause the K /SUB B/ for the diimide to be 40 times larger than that for the monoimide. This observation is consistent with the current electrostatic theory for counterion binding to DNA: a dication should cause the release of more counterions than a monocation and produce a more positive ..delta..S /SUP O/ /SUB B/ . For the amino substituted naphthalene monoimides, the K /SUB B/ values are similar to the other monoimides, but ..delta..H /SUP O/ /SUB B/ = -6.7 kcal-mol/sup -1/. We propose that a hydrogen bond is responsible for the unusual enthalpy and entropy effects seen for 3-NH/sub 2/MI and 4-NH/sub 2/MI.

  6. Elucidation of hydroxyl groups-antioxidant relationship in mono- and dihydroxyflavones based on O-H bond dissociation enthalpies.

    Science.gov (United States)

    Treesuwan, Witcha; Suramitr, Songwut; Hannongbua, Supa

    2015-06-01

    Radical scavenging potential is the key to anti-oxidation of hydroxyflavones which generally found in fruits and vegetables. The objective of this work was to investigate the influence of hydroxyl group on the O-H bond dissociation enthalpies (BDE) from a series of mono- and dihydroxyflavones. Calculation at the B3LYP/6-31G(d,p) level reveals the important roles of an additional one hydroxyl group to boost the BDE of hydroxyflavones that were a stabilization of the generated radicals through attractive H-bond interactions, an ortho- and para-dihydroxyl effect, and a presence of the 3-OH in dihydroxyflavones. On the other hand, the meta-dihydroxyl effect and range-hydroxyl effect especially associated with the either 5-OH or 8-OH promoted greater BDE. Results did not only confirm that dihydroxyflavones had lower BDE than monohydroxyflavones but also suggest the selective potent hydroxyflavone molecules that are the 6'-hydroxyflavone (for monohydroxyflavone) and the 5',6'-, 7,8- and 3',4'-dihydroxyflavone which the corresponding radical preferable generated at C6'-O•, C8-O• and C4'-O•, respectively. Electron distribution was limited only over the two connected rings of hydroxyflavones while the expansion distribution into C-ring could be enhanced if the radical was formed especially for the 2',3'- and 5',6'dihydroxyflavone radicals. The delocalized bonds were strengthened after radical was generated. However the 5-O• in 5,6-dihydroxyflavone and the 3-O• in 3,6'-dihydroxyflavone increased the bond order at C4-O11 which might interrupt the conjugated delocalized bonds at the keto group.

  7. Particle Size (Sieving) and Enthalpy (Acid Calorimetry) Analysis of Single-Pull K East Basin Floor and Pit Sludges

    Energy Technology Data Exchange (ETDEWEB)

    PR Bredt; CH Delegard; AJ Schmidt; KL Silvers; BM Thornton; S Gano

    2000-12-22

    This report presents the results of particle size analyses and calorimetry testing performed on selected single-pull sludge samples collected from the Hanford K East Basin between December 1998 and June 1999. The samples were collected as isolated cores predominantly from areas that had not been previously sampled (e.g., North Loadout Pit, Dummy Elevator Pit, Tech View Pit), or from areas in which the sludge composition had been altered since the last sampling (e.g., Weasel Pit). Particle size analyses were performed by washing wet sludge samples through a series of four sieves with openings of 250, 500, 1410, and 4000 {micro}m. The loaded sieves were weighed before and after drying to obtain wet and dry particle size distributions. Knowledge of the particle size distribution is needed to design and predict the performance of the systems that will be used to retrieve, transport, and recover sludge. Also, sieving provides an opportunity to observe the components in the sludge. For example, during sieving of the sludge sample from the North Loadout Pit, significant quantities of organic ion exchange beads were observed. The uranium metal content and the particle size of the uranium metal in the K Basin sludge will largely determine the chemical reactivity of the sludge. In turn, the designs for the sludge handling and storage systems must be compatible with the reactivity of the sludge. Therefore, acid calorimetry was performed to estimate the uranium metal content of the sludge. For this testing, sludge samples were dissolved in nitric acid within a calibrated adiabatic calorimeter. The resulting dissolution enthalpy data were then used to discriminate between metallic uranium ({minus}3750 J/g in nitric acid) and uranium oxide ({minus}394 J/g in nitric acid). Results from this testing showed that the single-pull sludge samples contained little or no uranium metal.

  8. Enthalpies of solution of N,N,N',N'-tetramethylurea in amides, dimethylsulphoxide, and acetone at 298.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Evgeniy V. [Laboratory of Thermodynamics of Solutions of Non-electrolytes and Biologically Active Substances, Institute of Solution Chemistry, Russian Academy of Sciences, Akademicheskaya Str., 153045 Ivanovo (Russian Federation)], E-mail: evi@isc-ras.ru; Smirnov, Valeriy I. [Laboratory of Thermodynamics of Solutions of Non-electrolytes and Biologically Active Substances, Institute of Solution Chemistry, Russian Academy of Sciences, Akademicheskaya Str., 153045 Ivanovo (Russian Federation)

    2008-09-15

    The enthalpies of solution {delta}{sub sol}H{sub m}{sup m} were determined for N,N,N',N'-tetramethylurea in formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, and acetone. Measurements were made at 298.15 K and molalities m = (0.004 to 0.031) mol . kg{sup -1} with a precise isoperibol ampoule-type calorimeter. Standard enthalpies of solution {delta}{sub sol}H{sub m}{sup 0} and transfer {delta}{sub tr}H{sub m}{sup 0} from one solvent to another were computed. The enthalpies of solution of the solute in the hydrogen-non-bonding media were found to be endothermic and weak depending on the nature of methylation in a solvent molecule. It was concluded that the solvent proton-donor ability and existing steric hindrances for hydrogen bonding and other intermolecular interactions play the key role in solvation of tetramethylurea.

  9. Relativity

    CERN Document Server

    Einstein, Albert

    2013-01-01

    Time magazine's ""Man of the Century"", Albert Einstein is the founder of modern physics and his theory of relativity is the most important scientific idea of the modern era. In this short book, Einstein explains, using the minimum of mathematical terms, the basic ideas and principles of the theory that has shaped the world we live in today. Unsurpassed by any subsequent books on relativity, this remains the most popular and useful exposition of Einstein's immense contribution to human knowledge.With a new foreword by Derek Raine.

  10. Comment on ``The enthalpy of the O H homolytic dissociation: Basis-set extrapolated density functional theory and coupled cluster calculations'' by B.J. Costa Cabral and S. Canuto [Chem. Phys. Lett. 406 (2005) 300 305

    Science.gov (United States)

    DiLabio, Gino A.; Mulder, Peter

    2006-01-01

    Costa Cabral and Canuto [B.J. Costa Cabral, S. Canuto, Chem. Phys. Lett. 406 (2005) 300] have studied the O-H bond dissociation enthalpy in water, hydrogen peroxide, methanol, phenol and catechol using a number of theoretical methods. Their choice of experimental O-H bond dissociation enthalpies for phenol and catechol are not the best available values and led them to several erroneous conclusions about the performance of methodologies they tested. In this work, we present more rigorous experimental O-H bond dissociation enthalpies for phenol and catechol and discuss the implications these data have on the conclusions presented by Costa Cabral and Canuto. We also demonstrate the importance of the inclusion of higher-order excitations in the coupled-cluster treatment of bond dissociation enthalpy of the O-H bond in H 2O 2 and HOO rad .

  11. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, April--June 1978. [SRC process distillate; 157 to 675/sup 0/C and 130 to 1000 psia

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1978-08-01

    Experimental measurements were completed on a middle distillate furnished by Pittsburg and Midway Coal Mining Company. A total of 52 enthalpy measurements were made covering the ranges 157 to 675/sup 0/F and 130 to 1000 psia.

  12. Accurate experimental and theoretical enthalpies of association of TiCl4with typical Lewis bases used in heterogeneous Ziegler-Natta catalysis.

    Science.gov (United States)

    Credendino, R; Minenkov, Y; Liguori, D; Piemontesi, F; Melchior, A; Morini, G; Tolazzi, M; Cavallo, L

    2017-10-11

    Adducts of TiCl 4 with Lewis bases used as internal or external donors in heterogeneous Ziegler-Natta (ZN) catalysis represent a fundamental interaction contributing to the final composition of MgCl 2 supported ZN-catalysts. This study presents the accurate experimental evaluation, from titration calorimetry, of the formation enthalpy of TiCl 4 adducts with 15 Lewis bases of industrial interest. In addition, we report the accurate energies of association of TiCl 4 with the same Lewis bases from calculations at the DLPNO-CCSD(T) level of theory. These accurate experimental and theoretical association values are compared with selected methods based on density functional theory (DFT) in combination with popular continuum solvation models. Calculations suggest that the PBE-D3, and M06 functionals in combination with a triple-ζ plus polarization quality basis set provide the best performance when the basis set superposition error (BSSE) is not removed from the association energies. Cleaning the association energies with the BSSE with the counterpoise protocol suggests B3LYP-D3, TPSS-D3 and M06L as the best performing functionals. The introduction of solvent effects with the PCM and SMD continuum solvation models allows the DFT-based association enthalpies to be compared with the experimental values obtained from titration calorimetry. Both solvation models in combination with the PBE-D3, PBE0-D3, B3LYP-D3, TPSS-D3, M06L, and M06 functionals provide association enthalpies close to the experimental values with MUEs in the range of 10-15 kJ mol -1 .

  13. Accurate Experimental and Theoretical Enthalpies of Association of TiCl4 with Typical Lewis Bases Used in Heterogeneous Ziegler-Natta Catalysis

    KAUST Repository

    Credendino, Raffaele

    2017-09-18

    Adducts of TiCl4 with Lewis bases used as internal or external donors in heterogeneous Ziegler-Natta (ZN) catalysis represents a fundamental interaction contributing to the final composition of MgCl2 supported ZN-catalysts. This study presents the accurate experimental evaluation, from titration calorimetry, of the formation enthalpy of TiCl4 adducts with 15 Lewis bases of industrial interests. In addition, we report accurate energies of association of TiCl4 with the same Lewis bases from calculations at the DLPNO-CCSD(T) level of theory. These accurate experimental and theoretical association values are compared with selected methods based on density functional theory (DFT) in combination with popular continuum solvation models. Calculations suggest that the PBE-D3, and M06 functionals in combination with a triple-ζ plus polarization quality basis set provide the best performance when the basis set superposition error (BSSE) is not removed from the association energies. Cleaning the association energies by the BSSE with the counterpoise protocol suggests the B3LYP-D3, TPSS-D3 and M06L as the best performing functionals. Introducing solvent effects with the PCM and SMD continuum solvation models allows comparing the DFT based association enthalpies with the experimental values obtained from titration calorimetry. Both solvation models in combination with the PBE-D3, PBE0-D3, B3LYP-D3, TPSS-D3, M06L, and M06 functionals provide association enthalpies close to the experimental values with MUEs in range 10 – 15 kJ/mol.

  14. Thermodynamics of biofuels: Excess enthalpies for binary mixtures involving ethyl 1,1-dimethylethyl ether and hydrocarbons at different temperatures using a new flow calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Segovia, Jose J. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, E.T.S. de Ingenieros Industriales, Paseo del Cauce s/n 47011, Valladolid (Spain)], E-mail: josseg@eis.uva.es; Carmen Martin, M. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, E.T.S. de Ingenieros Industriales, Paseo del Cauce s/n 47011, Valladolid (Spain)], E-mail: mcmg@eis.uva.es; Vega-Maza, David [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, E.T.S. de Ingenieros Industriales, Paseo del Cauce s/n 47011, Valladolid (Spain)], E-mail: davveg@eis.uva.es; Chamorro, Cesar R. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, E.T.S. de Ingenieros Industriales, Paseo del Cauce s/n 47011, Valladolid (Spain)], E-mail: cescha@eis.uva.es; Villamanan, Miguel A. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, E.T.S. de Ingenieros Industriales, Paseo del Cauce s/n 47011, Valladolid (Spain)], E-mail: miguel.villamanan@eis.uva.es

    2009-06-15

    Excess molar enthalpies for the binary systems: (ethyl 1,1-dimethylethyl ether + heptane); (ethyl 1,1-dimethylethyl ether + cyclohexane); (ethyl 1,1-dimethylethyl ether + toluene); (cyclohexane + toluene), and (toluene + heptane) have been measured at T = (298.15 and 313.15) K using a new isothermal flow calorimeter developed in the laboratory. The technique was previously checked by measuring test systems. The experimental results have been correlated with the Redlich-Kister polynomial equation. The mixing effects observed and the influence of the temperature are discussed.

  15. Excess enthalpies of binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol, and heptane at T = 298.15 K and 313.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar, Fernando; Alaoui, Fatima E.M. [Departamento de Ingenieria Electromecanica, Escuela Politecnica Superior, Universidad de Burgos, E-09006 Burgos (Spain); Segovia, Jose J.; Villamanan, Miguel A. [Grupo de Termodinamica y Calibracion TERMOCAL, E.T.S. de Ingenieros Industriales, Universidad de Valladolid, E-47071 Valladolid (Spain); Montero, Eduardo A., E-mail: emontero@ubu.e [Departamento de Ingenieria Electromecanica, Escuela Politecnica Superior, Universidad de Burgos, E-09006 Burgos (Spain)

    2010-01-15

    Experimental excess molar enthalpies of the ternary systems left bracedibutyl ether (DBE) + 1-butanol + heptaneright brace and the corresponding binary systems at T = 298.15 K and T = 313.15 K at atmospheric pressure are reported. A quasi-isothermal flow calorimeter has been used to make the measurements. All the binary and the ternary systems show endothermic character. The experimental data for the binary and ternary systems have been fitted using the Redlich-Kister equation, the NRTL and UNIQUAC models. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equations.

  16. Experimental determinations of the enthalpy of a coal-derived (138/sup 0/)-373(/sup 0/F) naphtha fraction produced by the solvent-refined coal process

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.; Andrew, J.R.; Sharma, R.; Kidnay, A.J.

    1978-01-01

    Experimental determinations of the enthalpy of a coal-derived 138/sup 0/-373/sup 0/F naphtha fraction produced by the solvent refined coal process were made with a Freon 11 reference fluid boiloff calorimeter at inlet temperatures of 160/sup 0/-719/sup 0/F, pressures of 30-1500 psia, and an outlet temperature of 65/sup 0/F; 145 measurements were obtained over the liquid, vapor, two-phase, and critical regions. The estimated accuracy of the data was (PLUS OF MINUS)0.5%. Although the experimental data for this particular system were in fair agreement with prediction methods developed for petroleum fractions.

  17. Experimental determinations of the enthalpy of a coal-derived (138-373 F) naphtha fraction produced by the solvent-refined coal process

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F; Andrew, J.R.; Sharma, R.; Kidnay, A.J.

    1978-01-01

    Experimental determination of the enthalpy of a coal-derived 138-373 F naphtha fraction produced by the solvent refined coal process were made with a Freon 11 reference fluid boiloff calorimeter at inlet temperatures of 160-719 F, pressures of 30-1500 psia, and an outlet temperature of 65 F; 145 measurements were obtained over the liquid, vapor, two-phase, and critical regions. The estimated accuracy of the data was (plus or minus) 0.5%. Although the experimental data for this particular system were in fair agreement with prediction methods developed for petroleum fractions.

  18. MSTor: A program for calculating partition functions, free energies, enthalpies, entropies, and heat capacities of complex molecules including torsional anharmonicity

    Science.gov (United States)

    Zheng, Jingjing; Mielke, Steven L.; Clarkson, Kenneth L.; Truhlar, Donald G.

    2012-08-01

    processors) Operating system: Linux/Unix/Mac OS RAM: 2 Mbytes Classification: 16.3, 16.12, 23 Nature of problem: Calculation of the partition functions and thermodynamic functions (standard-state energy, enthalpy, entropy, and free energy as functions of temperatures) of complex molecules involving multiple torsional motions. Solution method: The multi-structural approximation with torsional anharmonicity (MS-T). The program also provides results for the multi-structural local harmonic approximation [1]. Restrictions: There is no limit on the number of torsions that can be included in either the Voronoi calculation or the full MS-T calculation. In practice, the range of problems that can be addressed with the present method consists of all multi-torsional problems for which one can afford to calculate all the conformations and their frequencies. Unusual features: The method can be applied to transition states as well as stable molecules. The program package also includes the hull program for the calculation of Voronoi volumes and six utility codes that can be used as stand-alone programs to calculate reduced moment-of-inertia matrices by the method of Kilpatrick and Pitzer, to generate conformational structures, to calculate, either analytically or by Monte Carlo sampling, volumes for torsional subdomain defined by Voronoi tessellation of the conformational subspace, to generate template input files, and to calculate one-dimensional torsional partition functions using the torsional eigenvalue summation method. Additional comments: The program package includes a manual, installation script, and input and output files for a test suite. Running time: There are 24 test runs. The running time of the test runs on a single processor of the Itasca computer is less than 2 seconds. J. Zheng, T. Yu, E. Papajak, I.M. Alecu, S.L. Mielke, D.G. Truhlar, Practical methods for including torsional anharmonicity in thermochemical calculations of complex molecules: The internal-coordinate multi

  19. DFT study of the effect of hydrostatic pressure on formation and migration enthalpies of intrinsic point defects in single crystal Si

    Energy Technology Data Exchange (ETDEWEB)

    Sueoka, Koji; Kamiyama, Eiji; Kariyazaki, Hiroaki [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); Vanhellemont, Jan [Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent (Belgium)

    2012-10-15

    The dependence of the formation enthalpy (H{sub f}) of the self-interstitial I and the vacancy V on the hydrostatic pressure P was obtained by calculating the formation energy (E{sub f}) and the relaxation volume (v{sub f}). The dependence of the migration enthalpy (H{sub m}) of I and V on the pressure P was also obtained by calculating the change of H{sub f} during the migration. Density functional theory calculations were used with 216-atom supercells and with special attention for the convergence of the calculations. The neutral I and V are found to have quasi constant formation energies E{sub f}{sup I} and E{sub f}{sup V} for pressures between - 1 GPa to 1 GPa. For the relaxation volume, v{sub f}{sup I} is almost constant while v{sub f}{sup V} decreases with increasing pressure P. The formation and migration enthalpies H{sub f}{sup I} and H{sub m}{sup I}, respectively, at the [110] dumbbell site are given by H{sub f}{sup I} = 3.425 - 0.055 x P (eV) and H{sub m}{sup I} = 0.981 - 0.039 x P (eV) with hydrostatic pressure P given in GPa. The H{sub f}{sup V} and H{sub m}{sup V} dependencies on P are given by H{sub f}{sup V} =3.543 - 0.024 x P{sup 2}- 0.009 x P (eV) and H{sub m}{sup V} = 0.249 + 0.005 x P{sup 2} - 0.030 x P (eV). These results indicate that hydrostatic pressure leads to a slight increase of the equilibrium concentration and diffusion of vacancies but this increase is considerably smaller than that of self-interstitials (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Structural identification by differential mass spectrometry as a criterion for selecting the best quantum chemical calculation of formation enthalpy for tetrachlorinated biphenyls.

    Science.gov (United States)

    Dinca, Nicolae; Covaci, Adrian

    2012-09-15

    The assignment of correct structures for isomers with similar mass spectra (e.g. polyhalogenated aromatic compounds) is not always successful when spectral libraries alone are employed or, even worse, when the compounds are not present in commercial spectral libraries. We present a computational method based on differential mass spectrometry (Diff-MS) for the validation of formation enthalpy (Δ(f)H) series calculated using quantum chemistry for the fragments produced in electron ionization (EI)-MS. The method simulates the chemical structure identification (CSI) of isomers with similar mass spectra using differential mass spectra and Δ(f)H series. The best Δ(f)H values were those from which the correct structures could be derived. We have used six tetrachlorinated biphenyl isomers (TeCBs 44, 46, 52, 66, 74, 77). Their EI mass spectra were acquired at 70 eV and, for the principal ions, five series of Δ(f) H values were computed by the semi-empirical methods, AM1, MINDO3, MNDO, PM3, and RM1. The generation of differential mass spectra and the correlation with the Δ(f)H series for the calculation of probabilities from the list of structural assignments were carried out with the ordering algorithm (ORD) of the CSI-Diff-MS Data Analysis 3.1.1 program. Intelligent software, used for structural elucidation based on MS and QCC, was employed to select the best values of the formation enthalpies of TeCBs. The advantages and disadvantages of the semi-empirical methods for the calculation of Δ(f)H values for different TeCB ions are critically presented. The best semi-empirical methods were RM1, AM1 and MINDO3, which can be used to calculate the Δ(f)H database necessary to identify TeCB isomers. This approach allowed the correct assignment of structures for isomers with very similar mass spectra and demonstrated the reliability of the correlation between differential mass spectra and the formation enthalpies of the fragment ions. Copyright © 2012 John Wiley & Sons, Ltd.

  1. HypCal, a general-purpose computer program for the determination of standard reaction enthalpy and binding constant values by means of calorimetry.

    Science.gov (United States)

    Arena, Giuseppe; Gans, Peter; Sgarlata, Carmelo

    2016-09-01

    The program HypCal has been developed to provide a means for the simultaneous determination, from data obtained by isothermal titration calorimetry, of both standard enthalpy of reaction and binding constant values. The chemical system is defined in terms of species of given stoichiometry rather than in terms of binding models (e.g., independent or cooperative). The program does not impose any limits on the complexity of the chemical systems that can be treated, including competing ligand systems. Many titration curves may be treated simultaneously. HypCal can also be used as a simulation program when designing experiments. The use of the program is illustrated with data obtained with nicotinic acid (niacin, pyridine-3 carboxylic acid). Preliminary experiments were used to establish the rather different titration conditions for the two sets of titration curves that are needed to determine the parameters for protonation of the carboxylate and amine groups.

  2. An isoperibol micro-bomb calorimeter for measurement of the enthalpy of combustion of organic compounds. Application to the study of succinic acid and acetanilide

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Aaron. E-mail: arojas@mail.cinvestav.mx; Valdes, Alejandro

    2003-08-01

    A micro static-bomb combustion calorimeter, developed from a 1107 Parr semi-micro bomb, has been provided with a new micro-bomb and calorimetric bucket. In the best conditions of operation, the energy equivalent of this calorimetric arrangement is just {epsilon}(calor)=(731.82 {+-} 0.22) J {center_dot} K{sup -1}, which means an uncertainty of 0.03 per cent for the calibration with benzoic acid NIST 39j. This combustion calorimeter has been used in the measurement of the enthalpy of combustion of the succinic acid and acetanilide, giving -(1489.3 {+-} 1.6) kJ {center_dot} mol{sup -1} and -(4222.5 {+-} 1.1) kJ {center_dot} mol{sup -1}, respectively, for these substances.

  3. A numerical investigation into the effects of compressibility and total enthalpy difference on the development of a laminar free shear layer.

    Science.gov (United States)

    Carpenter, P. W.

    1971-01-01

    A method is presented for integrating numerically the equations of motion for a compressible free shear layer developing from a boundary-layer profile of arbitrary shape. Sutherland's law is used to determine the coefficient of viscosity and the Prandtl number is taken as 0.72. Calculated results are reported for free-stream Mach numbers ranging from 0 to 10 and for stagnation-enthalpy ratios ranging from 0 to 5.0. The effects of varying the initial boundary-layer profile and of a discontinuity in temperature at the origin are also studied. The results include graphs showing the development of dividing-streamline velocity, of local Nusselt number, and of dividing-streamline location.

  4. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, April-June 1980. [107 references; effect and extent of assoiation

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1980-09-15

    Cryoscopic molecular weight determinations were made on 5 pure compounds and 7 coal liquids. The accuracy of the measurements, based on the data for pure compounds, was estimated to be within +- 10% of the actual value. A linear relationship between the molecular weight and concentration of sample in the benzene solvent was observed. It was found that the slope of the line correlated directly with the absolute error, between the predicted and experimental enthalpy values, for all the liquids studied. As the slope increased, the absolute error also increased. Thus, the cryoscopic molecular weight determinations, as a function of concentration, were found to be an excellent indication of the extent and effect of association in any given fluid; and, as such, should be preferred as a characterizing tool, over the viscosity measurements, or any combination of the two.

  5. Activation-energy for the reaction h+oh--]eaq- - kinetic determination of the enthalpy and entropy of solvation of the hydrated electron

    DEFF Research Database (Denmark)

    Hickle, B.; Sehested, Knud

    1985-01-01

    The reaction between atomic hydrogen and hydroxide ion in aqueous solutions H + OH- - eaq- + H20 has been studied by pulse radiolysis. The rate constant was measured at pH 11.7 and 12 by following the growth of the hydrated electron absorption at 600 nm. The activation energy of the reaction has...... been determined over the temperature range 15-60 "C as 6.3 f 0.6 kcal/mol(26.4 f 2.5 kJ/mol). From this value and the activation energy of the reverse reaction, the ea; enthalpy of formation AHf = -32.6 f 1.6 kcal/mol (-136.4 f 6.7 kJ/mol) and its standard entropy So = 16.7 f 5.4 cal/(mol deg) (69.8 f...

  6. Enthalpy-based multiple-relaxation-time lattice Boltzmann method for solid-liquid phase-change heat transfer in metal foams.

    Science.gov (United States)

    Liu, Qing; He, Ya-Ling; Li, Qing

    2017-08-01

    In this paper, an enthalpy-based multiple-relaxation-time (MRT) lattice Boltzmann (LB) method is developed for solid-liquid phase-change heat transfer in metal foams under the local thermal nonequilibrium (LTNE) condition. The enthalpy-based MRT-LB method consists of three different MRT-LB models: one for flow field based on the generalized non-Darcy model, and the other two for phase-change material (PCM) and metal-foam temperature fields described by the LTNE model. The moving solid-liquid phase interface is implicitly tracked through the liquid fraction, which is simultaneously obtained when the energy equations of PCM and metal foam are solved. The present method has several distinctive features. First, as compared with previous studies, the present method avoids the iteration procedure; thus it retains the inherent merits of the standard LB method and is superior to the iteration method in terms of accuracy and computational efficiency. Second, a volumetric LB scheme instead of the bounce-back scheme is employed to realize the no-slip velocity condition in the interface and solid phase regions, which is consistent with the actual situation. Last but not least, the MRT collision model is employed, and with additional degrees of freedom, it has the ability to reduce the numerical diffusion across the phase interface induced by solid-liquid phase change. Numerical tests demonstrate that the present method can serve as an accurate and efficient numerical tool for studying metal-foam enhanced solid-liquid phase-change heat transfer in latent heat storage. Finally, comparisons and discussions are made to offer useful information for practical applications of the present method.

  7. Dispersion-correcting potentials can significantly improve the bond dissociation enthalpies and noncovalent binding energies predicted by density-functional theory

    Science.gov (United States)

    DiLabio, Gino A.; Koleini, Mohammad

    2014-05-01

    Dispersion-correcting potentials (DCPs) are atom-centered Gaussian functions that are applied in a manner that is similar to effective core potentials. Previous work on DCPs has focussed on their use as a simple means of improving the ability of conventional density-functional theory methods to predict the binding energies of noncovalently bonded molecular dimers. We show in this work that DCPs developed for use with the LC-ωPBE functional along with 6-31+G(2d,2p) basis sets are capable of simultaneously improving predicted noncovalent binding energies of van der Waals dimer complexes and covalent bond dissociation enthalpies in molecules. Specifically, the DCPs developed herein for the C, H, N, and O atoms provide binding energies for a set of 66 noncovalently bonded molecular dimers (the "S66" set) with a mean absolute error (MAE) of 0.21 kcal/mol, which represents an improvement of more than a factor of 10 over unadorned LC-ωPBE/6-31+G(2d,2p) and almost a factor of two improvement over LC-ωPBE/6-31+G(2d,2p) used in conjunction with the "D3" pairwise dispersion energy corrections. In addition, the DCPs reduce the MAE of calculated X-H and X-Y (X,Y = C, H, N, O) bond dissociation enthalpies for a set of 40 species from 3.2 kcal/mol obtained with unadorned LC-ωPBE/6-31+G(2d,2p) to 1.6 kcal/mol. Our findings demonstrate that broad improvements to the performance of DFT methods may be achievable through the use of DCPs.

  8. Enthalpy-based multiple-relaxation-time lattice Boltzmann method for solid-liquid phase-change heat transfer in metal foams

    Science.gov (United States)

    Liu, Qing; He, Ya-Ling; Li, Qing

    2017-08-01

    In this paper, an enthalpy-based multiple-relaxation-time (MRT) lattice Boltzmann (LB) method is developed for solid-liquid phase-change heat transfer in metal foams under the local thermal nonequilibrium (LTNE) condition. The enthalpy-based MRT-LB method consists of three different MRT-LB models: one for flow field based on the generalized non-Darcy model, and the other two for phase-change material (PCM) and metal-foam temperature fields described by the LTNE model. The moving solid-liquid phase interface is implicitly tracked through the liquid fraction, which is simultaneously obtained when the energy equations of PCM and metal foam are solved. The present method has several distinctive features. First, as compared with previous studies, the present method avoids the iteration procedure; thus it retains the inherent merits of the standard LB method and is superior to the iteration method in terms of accuracy and computational efficiency. Second, a volumetric LB scheme instead of the bounce-back scheme is employed to realize the no-slip velocity condition in the interface and solid phase regions, which is consistent with the actual situation. Last but not least, the MRT collision model is employed, and with additional degrees of freedom, it has the ability to reduce the numerical diffusion across the phase interface induced by solid-liquid phase change. Numerical tests demonstrate that the present method can serve as an accurate and efficient numerical tool for studying metal-foam enhanced solid-liquid phase-change heat transfer in latent heat storage. Finally, comparisons and discussions are made to offer useful information for practical applications of the present method.

  9. Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4 : Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra

    NARCIS (Netherlands)

    Marashdeh, A.; Frankcombe, T.J.

    2008-01-01

    The dehydrogenation enthalpies of Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4 have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski’s direct method. The

  10. Enthalpy-entropy compensation based on isotherms of mango Compensação entalpia-entropia baseada nas isotermas de mango

    Directory of Open Access Journals (Sweden)

    Javier Telis-Romero

    2005-06-01

    Full Text Available Moisture equilibrium data of mango pulp were determined using the static gravimetric method. Adsorption and desorption isotherms were obtained in the range of 30-70 ºC, to water activities (a w from 0.02 to 0.97. The application of the GAB model to the experimental results, using direct nonlinear regression analysis, provided agreement between experimental and calculated values. The net isosteric heat of sorption was estimated from equilibrium sorption data, using the Clausius-Clapeyron equation. Isosteric heats of sorption were found to increase with increasing temperature and could be well adjusted by an exponential relationship. The enthalpy-entropy compensation theory was applied to sorption isotherms and plots of deltaH versus deltaS provided the isokinetic temperatures, indicating an enthalpy controlled sorption process.Dados de equilíbrio da umidade da polpa de manga foram determinados utilizando-se o método estático gravimétrico. As isotermas de adsorção e dessorção foram obtidas na faixa de 30-70 ºC e as atividades de água (a w de 0,02 a 0,97. A utilização do modelo de GAB nos resultados experimentais, através da análise de regressão não linear, proporcionou um bom ajuste entre os dados experimentais e os valores calculados. O calor isostérico de sorção foi estimado a partir dos dados de equilíbrio de sorção, utilizando-se a equação de Clausius-Clayperon. Notou-se que os calores isostéricos de sorção crescem com o aumento da temperatura e pode ser bem ajustado através de uma relação exponencial. A teoria da compensação entalpia-entropia foi aplicada às isotermas de sorção e gráficos deltaH versus deltaS forneceram as temperaturas isocinéticas, indicando um processo de sorção entalpicamente controlado.

  11. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant

    Science.gov (United States)

    2011-01-01

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  12. Mass spectrometric gas composition measurements associated with jet interaction tests in a high-enthalpy wind tunnel

    Science.gov (United States)

    Lewis, B. W.; Brown, K. G.; Wood, G. M., Jr.; Puster, R. L.; Paulin, P. A.; Fishel, C. E.; Ellerbe, D. A.

    1986-01-01

    Knowledge of test gas composition is important in wind-tunnel experiments measuring aerothermodynamic interactions. This paper describes measurements made by sampling the top of the test section during runs of the Langley 7-Inch High-Temperature Tunnel. The tests were conducted to determine the mixing of gas injected from a flat-plate model into a combustion-heated hypervelocity test stream and to monitor the CO2 produced in the combustion. The Mass Spectrometric (MS) measurements yield the mole fraction of N2 or He and CO2 reaching the sample inlets. The data obtained for several tunnel run conditions are related to the pressures measured in the tunnel test section and at the MS ionizer inlet. The apparent distributions of injected gas species and tunnel gas (CO2) are discussed relative to the sampling techniques. The measurements provided significant real-time data for the distribution of injected gases in the test section. The jet N2 diffused readily from the test stream, but the jet He was mostly entrained. The amounts of CO2 and Ar diffusing upward in the test section for several run conditions indicated the variability of the combustion-gas test-stream composition.

  13. Sub-Tg enthalpy relaxation in an extremely unstable oxide glass and its implication for structural heterogeneity

    DEFF Research Database (Denmark)

    Zhang, Yanfei; Hu, L.N.; Liu, S.J.

    2013-01-01

    We study the sub-Tg relaxation in an extremely unstable glass former, i.e., 65SiO2-35Al2O3, and its relation to structural heterogeneity (e.g., structurally ordered domains in glass matrix). This is done by hyperquenching (~106 K/s) the liquid, then annealing the hyperquenched glass below Tg...... and subsequently scanning the annealed hyperquenched glass in a differential scanning calorimeter. The results show that structural ordering can take place even below Tg. An endothermic pre-peak is observed when the hyperquenched sample is annealed at 0.75Tg for sufficiently long time, which is, however, much...... weaker compared to that of stable glass formers subjected to same annealing conditions. We also investigate the effect of the sub-Tg annealing on crystallization above Tg. The results imply that some structurally ordered domains exist already in the liquid state. The ordered domains lower the activation...

  14. Entropy-enthalpy compensation may be a useful interpretation tool for complex systems like protein-DNA complexes: An appeal to experimentalists

    KAUST Repository

    Starikov, E. B.

    2012-01-01

    In various chemical systems, enthalpy-entropy compensation (EEC) is a well-known rule of behavior, although the physical roots of it are still not completely understood. It has been frequently questioned whether EEC is a truly physical phenomenon or a coincidence due to trivial mathematical connections between statistical-mechanical parameters-or even simpler: A phantom effect resulting from the misinterpretation of experimental data. Here, we review EEC from another standpoint using the notion of correlation, which is essential for the method of factor analysis but is not conventional in physics and chemistry. We conclude that the EEC may be rationalized in terms of hidden (not directly measurable with the help of the current experimental set-up) but physically real factors, implying a Carnot-cycle model in which a micro-phase transition (MPT) plays a crucial role. Examples of such MPTs underlying physically valid EEC should be typically cooperative processes in supramolecular aggregates, like changes of structured water at hydrophobic surfaces, conformational transitions upon ligand-biopolymer binding, and so on. The MPT notion could help rationalize the occurrence of EEC in connection with hydration and folding of proteins, enzymatic reactions, functioning of molecular motors, DNA de- and rehybridization, as well as similar phenomena. © 2012 American Institute of Physics.

  15. The chemistry and isotopic composition of waters in the low-enthalpy geothermal system of Cimino-Vico Volcanic District, Italy

    DEFF Research Database (Denmark)

    Battistel, Maria; Hurwitz, Shaul; Evans, William C.

    2016-01-01

    Geothermal energy exploration is based in part on interpretation of the chemistry, temperature, and discharge rate of thermal springs. Here we present the major element chemistry and the δD, δ18O, 87Sr/86Sr and δ11B isotopic ratio of groundwater from the low-enthalpy geothermal system near the city...... of Viterbo in the Cimino-Vico volcanic district of west-Central Italy. The geothermal system hosts many thermal springs and gas vents, but the resource is still unexploited. Water chemistry is controlled by mixing between low salinity,HCO3-rich fresh waters (... and SO4-rich thermal waters (25.3 °C to 62.2 °C) ascending from deep, high permeability Mesozoic limestones. The (equivalent) SO4/Cl (0.01–0.02), Na/Cl (2.82–5.83) and B/Cl ratios (0.02–0.38) of thermal waters differs from the ratios in other geothermal systems from Central Italy, probably implying...

  16. Structures and standard molar enthalpies of formation of a series of Ln(III)-Cu(II) heteronuclear compounds with pyrazine-2,3-dicarboxylic acid

    Science.gov (United States)

    Yang, Qi; Xie, Gang; Wei, Qing; Chen, Sanping; Gao, Shengli

    2014-07-01

    Fifteen lanthanide-copper heteronuclear compounds, formulated as [CuLn2(pzdc)4(H2O)6]·xH2O (1-6(x=2), 8(x=3), 9-10(x=4); [CuLn2(pzdc)4(H2O)4]·xH2O (7, 12-13, 15(x=4), 14(x=5), 11(x=8) (Ln(III)=La(1); Ce(2); Pr(3); Nd(4); Sm(5); Eu(6); Gd(7); Tb(8); Dy(9); Ho(10); Er(11); Tm(12); Yb(13); Lu(14); Y(15); H2pzdc (C6H4N2O4)=pyrazine-2,3-dicarboxylic acid) have been hydrothermally synthesized. All compounds were characterized by element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analyses confirm that all compounds are isostructural and feature a 3D brick-like framework structure with {4.62}2{42.62.82}{63}2{65.8}2 topology. Using 1 mol cm-3 HCl(aq) as calorimetric solvent, with an isoperibol solution-reaction calorimeter, the standard molar enthalpies of formation of all compounds were determined by a designed thermochemical cycle. In addition, solid state luminescence properties of compounds 5, 6, 8 and 9 were studied in the solid state.

  17. Determining the number of isomers in X-, XY-, XYZ-, and XYZU-substituted D2 d allenes: Additive schemes for calculating enthalpies of vaporization

    Science.gov (United States)

    Nilov, D. Yu.; Smolyakov, V. M.

    2015-02-01

    Using Pólya's theorem, cycle indices are derived that identify the chiral and achiral substitution isomers of an allene (1,2-propadiene). Equations of symmetry that allow us to determine the number of isomers in a series and arrange the isomers according to families, depending on the number of substitution sites, are obtained. Eight- and nine-constant additive schemes based on the similarity between subgraphs in the molecular graphs (MGs) of a series of 120 molecules of X-, XY-, XYZ-, and XYZU-substituted allenes and the expansion of polygonal numbers (triangular, tetrahedral, and others) of a Pascal triangle are devised. Enthalpies of vaporization L NBP are calculated for 21 XY- and 120 XYZU-substituted allenes, respectively, not yet studied experimentally. It is shown that each coefficient of the scheme (the number of ways for superpositioning subgraphs with lengths i 1, i 2, ⋯ on molecular graphs of allene) is a result of partitioning triangular, tetrahedral, or four-dimensional tetrahedral numbers of a Pascal triangle.

  18. Excess enthalpies of mixing, effect of temperature and composition on the density, and viscosity and thermodynamic properties of binary systems of {ammonium-based ionic liquid + alkanediol}.

    Science.gov (United States)

    Domańska, Urszula; Papis, Paulina; Szydłowski, Jerzy; Królikowska, Marta; Królikowski, Marek

    2014-11-06

    In the present work the excess enthalpies of butyltrimethylammonium bis(trifluoromethyl-sulfonyl)imide, [N1114][NTf2], with 1,2-propanediol, or 1,2-butanediol, or 2,3-butanediol have been measured at T = 298.15 K. Additionally, the density, ρ, and dynamic viscosity, η, for binary solutions containing ionic liquids (ILs) and alkanedioles, {butyltrimethylammonium bis(trifluoromethyl-sulfonyl)imide, [N1114][NTf2], + 1,2-propanediol, 1,2-butanediol, 2,3-butanediol} and {(2-hydroxyethyl)trimethylammonium bis(trifluoro-methylsulfonyl)imide, [N1112OH][NTf2], + 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol}, at wide temperature and composition ranges at ambient pressure have been investigated. From experimental values of the density, ρ, and dynamic viscosity, η, the excess molar volumes, V(E), and dynamic viscosity deviations, Δη, were calculated and correlated using the Redlich-Kister polynomial equation. The temperature dependence of density and viscosity for the tested binary systems was described by an empirical second-order polynomial and by the Vogel-Fucher-Tammann equation, respectively. The variation of density and viscosity as a function of composition has been described by the polynomial correlations. Comparison of the experimental results for the binary mixtures tested in this work allows us to determine the influence of alkanediol carbon chain length, the position of the hydroxyl group in the alcohol, and the influence of the structure of the cation of the ionic liquid on the presented properties.

  19. Volume and enthalpy relaxation in Zr{sub 55}Cu{sub 30}Ni{sub 5}Al{sub 10} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Haruyama, O., E-mail: haruyama@ph.noda.tus.ac.jp [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Noda 278-8510 (Japan); Nakayama, Y.; Wada, R. [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Noda 278-8510 (Japan); Tokunaga, H. [Department of Mechanical Engineering, Ube National College of Technology, Ube 755-8555 (Japan); Okada, J.; Ishikawa, T. [Institute of Space and Astronautical Science, Japan Aerospace, Exploration Agency, Tsukuba 305-8505 (Japan); Yokoyama, Y. [Institute of Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2010-03-15

    The structural relaxation in a Zr{sub 55}Cu{sub 30}Ni{sub 5}Al{sub 10} bulk metallic glass was investigated by volume and enthalpy relaxation at various temperatures. The relaxation kinetics was well described by a stretched exponential relaxation function, {Phi}(t)=exp[-(t/{tau}){sup {beta}}]. The Kohlrausch index, {beta}, ranged from 0.35 to 0.69, while the temperature dependence of relaxation time, {tau} was best fitted by the Vogel-Fulcher-Tanmmann formula, {tau}(T)={tau}{sub 0}exp[D{sup *}T{sub 0}/(T-T{sub 0})], with {tau}{sub 0} = 1.1 x 10{sup -14} s, D{sup *} = 44.2 and T{sub 0} = 311 K. Atomic volumes in the equilibrium liquid region were measured by the electrostatic levitation method and these volumes, together with volumes of relaxed glasses, were better described by the Cohen-Grest model than by the Cohen-Turnbull model.

  20. Calorimetry investigations of milled α-tricalcium phosphate (α-TCP) powders to determine the formation enthalpies of α-TCP and X-ray amorphous tricalcium phosphate.

    Science.gov (United States)

    Hurle, Katrin; Neubauer, Juergen; Bohner, Marc; Doebelin, Nicola; Goetz-Neunhoeffer, Friedlinde

    2015-09-01

    One α-tricalcium phosphate (α-TCP) powder was either calcined at 500°C to obtain fully crystalline α-TCP or milled for different durations to obtain α-TCP powders containing various amounts of X-ray amorphous tricalcium phosphate (ATCP). These powders containing between 0 and 71wt.% ATCP and up to 2.0±0.1wt.% β-TCP as minor phase were then hydrated in 0.1M Na2HPO4 aqueous solution and the resulting heat flows were measured by isothermal calorimetry. Additionally, the evolution of the phase composition during hydration was determined by in situ XRD combined with the G-factor method, an external standard method which facilitates the indirect quantification of amorphous phases. Maximum ATCP hydration was reached after about 1h, while that of crystalline α-TCP hydration occurred between 4 and 11h, depending on the ATCP content. An enthalpy of formation of -4065±6kJ/mol (T=23°C) was calculated for ATCP (Ca3(PO4)2), while for crystalline α-TCP (α-Ca3(PO4)2) a value of -4113±6kJ/mol (T=23°C) was determined. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  1. An automated flow calorimeter for heat capacity and enthalpy measurements at elevated temperatures and pressures: Progress report for period March 1, 1988--February 29, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.

    1988-10-30

    The need for thermal property data at process conditions has been well documented in applications such as development of atmospherically inert refrigerants and design of petrochemical and synfuel plants. As such, the primary objective of this work is to construct an automated flow calorimeter to measure isobaric heat capacities and enthalpies of vaporization over the range 0--30MPa and 300--700K with an anticipated accuracy of 0.1%. The method of measurement is an adiabatic electrical power input technique with a unique calorimeter design utilizing a concentric coil/radiation shield structure which minimizes heat loss errors and simplifies the replacement of plugged components. Flow generation is accomplished with a precision Ruska pump eliminating the need for on-line flow rate measurement. In addition, the proposed instrument will be fully automated minimizing the need for highly skilled operators which had previously been a severe limitation with this type of instrument. Assembly of all hardware and implementation of the necessary software was completed within the past year. In addition, water was used as a heat capacity standard to evaluate overall system performance. Preliminary indications are that the apparatus is operating near expectations (+//minus/0.2%) although some additional hardware refinements may be necessary achieve the design goals of +//minus/0.1%. 15 refs., 4 figs., 1 tab.

  2. An automated flow calorimeter for heat capacity and enthalpy measurements at elevated temperatures and pressures: Progress report, March 1, 1987-February 29, 1988

    Energy Technology Data Exchange (ETDEWEB)

    Yesavage, V.F.

    1987-10-01

    The need for thermal property data at process conditions in the design of petrochemical and synfuel plants has been well documented. As such, the primary objective of this work is to construct an automated flow calorimeter to measure isobaric heat capacities and enthalpies of vaporization over the range 0 to 30MPa and 300 to 700K with an anticipated accuracy of 0.1%. The method of measurement is by the traditional electrical power input technique with a unique calorimeter design utilizing a concentric coil/radiation shield structure which minimizes heat loss errors and simplifies the replacement of plugged components. Flow generation is accomplished with a precision Ruska pump eliminating the need for on-line flow rate measurement. In addition, the proposed instrument will be fully automated minimizing the need for highly skilled operators which had previously been a severe limitation with this type of instrument. Significant progress has been made on the project this last year with the completion of construction of all major system hardware components and the associated automation electronics. Initial tests of the equipment are encouraging and no significant delays are foreseen in the completion of the apparatus. During the next year the automation and data acquisition software will be written and the completed unit will be tested with water. 7 figs.

  3. Enthalpy measurement of coal-derived liquids. Technical progress report, August-January 1982. [Isobars of 517. 1, 689. 5, 1034. 2, 1379. 1, and 10342. 5 kPa temperature range of 340 to 664/sup 0/K

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1982-04-01

    The compound quinoline is discussed. Process flow in the flow calorimeter, operational problems, and equipment modifications are described. Procedural modifications, including a new sample purification procedure, are described. Quinoline enthalpy data are presented along the isobars of 517.1, 689.5, 1034.2, 1379.0, 3799.1, and 10342.5 kPa over a temperature range of 340 to 664/sup 0/K. Experimental enthalpy values and thermodynamic properties derived from this data are compared to corresponding values found in the literature, and to values predicted using computer aided calculations involving three correlations. The three correlations are: the SRK equation of state, and two modifications of the BWR equation of state by Kesler et al. and Starling, respectively. In general, the correlations do not accurately predict the thermodynamic behavior of quinoline. However, the experimental data compare well with available literature data for quinoline vapor pressures.

  4. Theoretical investigation on the bond dissociation enthalpies of phenolic compounds extracted from Artocarpus altilis using ONIOM(ROB3LYP/6-311++G(2df,2p):PM6) method

    Science.gov (United States)

    Thong, Nguyen Minh; Duong, Tran; Pham, Linh Thuy; Nam, Pham Cam

    2014-10-01

    Theoretical calculations have been performed to predict the antioxidant property of phenolic compounds extracted from Artocarpus altilis. The Osbnd H bond dissociation enthalpy (BDE), ionization energy (IE), and proton dissociation enthalpy (PDE) of the phenolic compounds have been computed. The ONIOM(ROB3LYP/6-311++G(2df,2p):PM6) method is able to provide reliable evaluation for the BDE(Osbnd H) in phenolic compounds. An important property of antioxidants is determined via the BDE(Osbnd H) of those compounds extracted from A. altilis. Based on the BDE(Osbnd H), compound 12 is considered as a potential antioxidant with the estimated BDE value of 77.3 kcal/mol in the gas phase.

  5. Pair natural orbital and canonical coupled cluster reaction enthalpies involving light to heavy alkali and alkaline earth metals: the importance of sub-valence correlation

    KAUST Repository

    Minenkov, Yury

    2017-03-07

    In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes of Li, Be, Na, Mg, Ca, Sr, Ba and Pb(ii). Two strategies were investigated: in the former, only valence electrons were included in the correlation treatment, giving rise to the computationally very efficient FC (frozen core) approach; in the latter, all non-ECP electrons were included in the correlation treatment, giving rise to the AE (all electron) approach. Apart from reactions involving Li and Be, the FC approach resulted in non-homogeneous performance. The FC approach leads to very small errors (<2 kcal mol-1) for some reactions of Na, Mg, Ca, Sr, Ba and Pb, while for a few reactions of Ca and Ba deviations up to 40 kcal mol-1 have been obtained. Large errors are both due to artificial mixing of the core (sub-valence) orbitals of metals and the valence orbitals of oxygen and halogens in the molecular orbitals treated as core, and due to neglecting core-core and core-valence correlation effects. These large errors are reduced to a few kcal mol-1 if the AE approach is used or the sub-valence orbitals of metals are included in the correlation treatment. On the technical side, the CCSD(T) and DLPNO-CCSD(T) results differ by a fraction of kcal mol-1, indicating the latter method as the perfect choice when the CPU efficiency is essential. For completely black-box applications, as requested in catalysis or thermochemical calculations, we recommend the DLPNO-CCSD(T) method with all electrons that are not covered by effective core potentials included in the correlation treatment and correlation-consistent polarized core valence basis sets of cc-pwCVQZ(-PP) quality.

  6. Solvation molar enthalpies and heat capacities of n-alkanes and n-alkylbenzenes on stationary phases of wide-ranging polarity.

    Science.gov (United States)

    Lebrón-Aguilar, Rosa; Quintanilla-López, Jesús Eduardo; Santiuste, José María

    2010-12-03

    A comparison of the most usual gas chromatographic methods for the calculation of partial molar enthalpies of solvation (Δ(sol)H(o)) has been carried out. Those methods based on the fitting of lnV(g) or ln(k/T) vs. 1/T and ln(k/T) vs. (1/T and the temperature arrangement, T(a)) are the most adequate ones for obtaining Δ(sol)H(o) values. However, the latter is the only reliable option for Δ(sol)H(o) estimation when commercial WCOT capillary columns are used, since in this case the estimation of some variables involved in the V(g) determination is less accurate or even impossible. Consequently, in this paper, Δ(sol)H(o) obtained from ln(k/T) vs. (1/T+T(a)) fitting at 373.15 and 298.15K for n-alkanes and n-alkylbenzenes on 12 commercial capillary columns coated with stationary phases covering the 203-3608 McReynolds polarity range are reported. Moreover, molar heat capacities of solvation at constant pressure (Δ(sol)C(p)(o)) have also been calculated using this method. A clear influence on Δ(sol)H(o) of the type and content of the substitution group in the stationary phase was observed. In addition, a linear relationship of Δ(sol)C(p)(o) with the van der Waals volume of the n-alkanes and the temperature gradient of density of the stationary phase was found. The effect of the size of the hydrocarbon on both thermodynamic variables was also investigated. Copyright © 2010 Elsevier B.V. All rights reserved.

  7. Hydration Enthalpies of Ba(2+)(H2O)x, x = 1-8: A Threshold Collision-Induced Dissociation and Computational Investigation.

    Science.gov (United States)

    Wheeler, Oscar W; Carl, Damon R; Hofstetter, Theresa E; Armentrout, P B

    2015-04-23

    The sequential bond dissociation energies (BDEs) of Ba(2+)(H2O)x complexes, where x = 1-8, are determined using threshold collision-induced dissociation (TCID) in a guided ion beam tandem mass spectrometer. The electrospray ionization source generates complexes ranging in size from x = 6 to x = 8 with smaller complexes, x = 1-5, formed by an in-source fragmentation technique. The only products observed result from sequential loss of water ligands. Charge separation, a process in which both hydrated singly charged barium hydroxide and hydronium ion are formed, was not observed except for Ba(2+)(H2O)3 yielding BaOH(+) + H5O2(+). Modeling of the kinetic energy-dependent cross sections, taking into account the number of collisions, energy distributions, and lifetime effects for both primary and secondary water loss, provides 0 K BDEs. Experimental thermochemistry for the x = 1-3 complexes is obtained here for the first time. Hydration enthalpies and reaction coordinate pathways for charge separation are also examined computationally at several levels of theory. Our experimental and computational work are in excellent agreement in the x = 1-6 range. The present experimental values and theoretical calculations are also in reasonable agreement with the available literature values for experiment, x = 4-8, and theory, x = 1-6. Of the numerous calculations performed in the current study, B3LYP/DHF/def2-TZVPP calculations including counterpoise corrections reproduce our experimental values the best, although MP2(full)/DHF/def2-TZVPP//B3LYP/DHF/def2-TZVPP results are comparable.

  8. Direct measurements of the total rate constant of the reaction NCN + H and implications for the product branching ratio and the enthalpy of formation of NCN.

    Science.gov (United States)

    Fassheber, Nancy; Dammeier, Johannes; Friedrichs, Gernot

    2014-06-21

    The overall rate constant of the reaction (2), NCN + H, which plays a key role in prompt-NO formation in flames, has been directly measured at temperatures 962 K rate constants are best represented by the combination of two Arrhenius expressions, k2/(cm(3) mol(-1) s(-1)) = 3.49 × 10(14) exp(-33.3 kJ mol(-1)/RT) + 1.07 × 10(13) exp(+10.0 kJ mol(-1)/RT), with a small uncertainty of ±20% at T = 1600 K and ±30% at the upper and lower experimental temperature limits.The two Arrhenius terms basically can be attributed to the contributions of reaction channel (2a) yielding CH + N2 and channel (2b) yielding HCN + N as the products. A more refined analysis taking into account experimental and theoretical literature data provided a consistent rate constant set for k2a, its reverse reaction k1a (CH + N2 → NCN + H), k2b as well as a value for the controversial enthalpy of formation of NCN, ΔfH = 450 kJ mol(-1). The analysis verifies the expected strong temperature dependence of the branching fraction ϕ = k2b/k2 with reaction channel (2b) dominating at the experimental high-temperature limit. In contrast, reaction (2a) dominates at the low-temperature limit with a possible minor contribution of the HNCN forming recombination channel (2d) at T < 1150 K.

  9. Improved methods for Feynman path integral calculations and their application to calculate converged vibrational-rotational partition functions, free energies, enthalpies, entropies, and heat capacities for methane.

    Science.gov (United States)

    Mielke, Steven L; Truhlar, Donald G

    2015-01-28

    We present an improved version of our "path-by-path" enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P(-6)) to O(P(-12)), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational-rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan-Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ∼1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300-3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities.

  10. The chemistry and isotopic composition of waters in the low-enthalpy geothermal system of Cimino-Vico Volcanic District, Italy

    Science.gov (United States)

    Battistel, Maria; Hurwitz, Shaul; Evans, William; Barbieri, Maurizio

    2017-01-01

    Geothermal energy exploration is based in part on interpretation of the chemistry, temperature, and discharge rate of thermal springs. Here we present the major element chemistry and the δD, δ18O, 87Sr/86Sr and δ11B isotopic ratio of groundwater from the low-enthalpy geothermal system near the city of Viterbo in the Cimino-Vico volcanic district of west-Central Italy. The geothermal system hosts many thermal springs and gas vents, but the resource is still unexploited. Water chemistry is controlled by mixing between low salinity,HCO3-rich fresh waters (<24.2°C) flowing in shallow volcanic rocks and SO4-rich thermal waters (25.3°C to 62.2°C) ascending from deep, high permeability Mesozoic limestones. The (equivalent) SO4/Cl (0.01–0.02), Na/Cl (2.82–5.83) and B/Cl ratios (0.02–0.38) of thermal waters differs from the ratios in other geothermal systems from Central Italy, probably implying a lack of hydraulic continuity across the region. The δ18O (−6.6‰ to −5.9‰) and δD (−40.60‰ to −36.30‰) isotopic composition of spring water suggest that the recharge area for the geothermal system is the summit region of Mount Cimino. The strontium isotope ratios (87Sr/86Sr) of thermal waters (0.70797–0.70805) are consistent with dissolution of the Mesozoic evaporite-carbonate units that constitute the reservoir, and the ratios of cold fresh waters mainly reflect shallow circulation through the volcanic cover and some minor admixture (<10%) of thermal water as well. The boron isotopic composition (δ11B) of fresh waters (−5.00 and 6.12‰) is similar to that of the volcanic cover, but the δ11B of thermal waters (−8.37‰ to −4.12‰) is a mismatch for the Mesozoic reservoir rocks and instead reflects dissolution of secondary boron minerals during fluid ascent through flysch units that overlie the reservoir. A slow and tortuous ascent enhances extraction of boron but also promotes conductive cooling, partially masking the heat present in the

  11. Characteristics of combustion and heat transfer of excess enthalpy flames stabilized in a stagnation flow. 2nd Report. ; Heat flux at high flow rate and effects of Lewis number. Yodomi nagarechu ni anteika sareta choka enthalpy kaen no nensho oyobi etsudentatsu tokusei. 2. ; Koryuryo ni okeru netsuryusoku oyobi Lewis su no koka

    Energy Technology Data Exchange (ETDEWEB)

    Ito, S. (Daido Institute of Technology, Nagoya (Japan)); Asato, K.; Kawamura, T. (Gifu University, Gifu (Japan). Faculty of Engineerirng); Mazaki, T. (Daido Senior High School, Nagoya (Japan)); Umemura, H. (Mitsubishi Electric Corp., Tokyo (Japan))

    1993-08-25

    For the purpose of developing small-sized combustors of high heat transfer efficiency for household and business uses, a study has been carried out on the characteristics of an excess enthalpy flame stabilized in a stagnant flow, the maximum heat flux utilizable from flames through a heat receiver wall, the heat transfer characteristics near the extinction limits, and the effects of Lewis number (Le). Even when heat is drawn from the heat receiver wall in the downstream of flames, stable flames are kept until they extremely approach the heat receiver wall by the effect of preheating for lean methane-air flames of Le[approx equal]1.0 and lean propane-air flames of Le>1.0 and by the effect of preheating and Lewis effect for lean hydrogen-air flames of Le<1.0. In any flames, therefore, the heat flux to the heat receiver wall increases abruptly with the increase of stagnant velocity gradient and thereby the heat transfer characteristics at the heat receiver wall are improved. Heat transfer in the cases where flames exist on the outside and inside of the temperature boundary layer depend not on the thickness of the temperature boundary layer but on the position of flames. 6 refs., 9 figs.

  12. First determination of volume changes and enthalpies of the high-pressure decomposition reaction of the structure H methane hydrate to the cubic structure I methane hydrate and fluid methane.

    Science.gov (United States)

    Ogienko, Andrey G; Tkacz, Marek; Manakov, Andrey Yu; Lipkowski, Janusz

    2007-11-08

    Pressure-temperature (P-T) conditions of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane were studied with a piston-cylinder apparatus at room temperature. For the first time, volume changes accompanying this reaction were determined. With the use of the Clausius-Clapeyron equation the enthalpies of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane have been calculated.

  13. GASP: A computer code for calculating the thermodynamic and transport properties for ten fluids: Parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. [enthalpy, entropy, thermal conductivity, and specific heat

    Science.gov (United States)

    Hendricks, R. C.; Baron, A. K.; Peller, I. C.

    1975-01-01

    A FORTRAN IV subprogram called GASP is discussed which calculates the thermodynamic and transport properties for 10 pure fluids: parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. The pressure range is generally from 0.1 to 400 atmospheres (to 100 atm for helium and to 1000 atm for hydrogen). The temperature ranges are from the triple point to 300 K for neon; to 500 K for carbon monoxide, oxygen, and fluorine; to 600 K for methane and nitrogen; to 1000 K for argon and carbon dioxide; to 2000 K for hydrogen; and from 6 to 500 K for helium. GASP accepts any two of pressure, temperature and density as input conditions along with pressure, and either entropy or enthalpy. The properties available in any combination as output include temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, and surface tension. The subprogram design is modular so that the user can choose only those subroutines necessary to the calculations.

  14. Enthalpy of formation of selected mixed oxides in a CaO-SrO-Bi{sub 2}O{sub 3}-Nb{sub 2}O{sub 5} system

    Energy Technology Data Exchange (ETDEWEB)

    Leitner, J., E-mail: Jindrich.Leitner@vscht.cz [Department of Solid State Engineering, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic); Nevriva, M.; Sedmidubsky, D. [Department of Inorganic Chemistry, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic); Vonka, P. [Department of Physical Chemistry, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic)

    2011-04-14

    Research highlights: > Heats of drop-solution in 3Na2O + 4MoO3 melt. > Enthalpy of formation for CaNb2O6, Ca2Nb2O7, SrNb2O6, Sr2Nb2O7 and BiNbO4. > Estimation of the enthalpy of formation for calcium, strontium and bismuth niobates. - Abstract: The heats of drop-solution in 3Na{sub 2}O + 4MoO{sub 3} melt at 973 K and 1073 K for calcium and strontium carbonates, Bi{sub 2}O{sub 3}, Nb{sub 2}O{sub 5} and several stoichiometric mixed oxides in CaO-Nb{sub 2}O{sub 5}, SrO-Nb{sub 2}O{sub 5} and Bi{sub 2}O{sub 3}-Nb{sub 2}O{sub 5} systems were measured using a Setaram Multi HTC-96 calorimeter. The values of enthalpy of formation from constituent binary oxides at 298 K, {Delta}{sub ox}H, were derived for the mixed oxides under investigation: {Delta}{sub ox}H(CaNb{sub 2}O{sub 6}) = -132.0 {+-} 23.8 kJ mol{sup -1}, {Delta}{sub ox}H(Ca{sub 2}Nb{sub 2}O{sub 7}) = -208.0 {+-} 31.9 kJ mol{sup -1}, {Delta}{sub ox}H(SrNb{sub 2}O{sub 6}) = -167.9 {+-} 19.1 kJ mol{sup -1}, {Delta}{sub ox}H(Sr{sub 2}Nb{sub 2}O{sub 7}) = -289.2 {+-} 37.5 kJ mol{sup -1} and {Delta}{sub ox}H(BiNbO{sub 4}) = -41.9 {+-} 11.1 kJ mol{sup -1}. Additionally, the values {Delta}{sub ox}H for other mixed oxides with different stoichiometries were estimated on the basis of these experimental results.

  15. Enthalpy measurement of coal-derived liquids. Quarterly technical progress report, October-December 1980. [2,6-dimethylpyridine; 105 to 705/sup 0/F; 50 to 1500 psia

    Energy Technology Data Exchange (ETDEWEB)

    Kidnay, A.J.; Yesavage, V.F.

    1981-02-15

    Equipment modifications to the Freon flow system of a reference fluid boil-off calorimeter are described. These modifications, along with a new equipment start-up procedure, have resulted in enhanced system stability, and consequently, better accuracy in the measurements. A thorough check of equipment calibration and operation was conducted to assure the validity of the experimental data. Using the flow calorimeter, enthalpy measurements were made for 2,6-dimethylpyridine. The data were taken over a temperature range of 105 to 745/sup 0/F along 50, 100, 200, 400, 576, 750, 1000, and 1500 psia isobars. Thermodynamic properties derived from the data were successfully compared to corresponding literature values. The measured quantities were also compared to those calculated from correlations using the SRK equation of state and a modification of the BWR equation of state by Kesler and Lee, and there is good agreement. However, comparisons between measured and calculated quantities are limited by the lack of ideal gas heat capacity data.

  16. Determination of the enthalpy of formation of Ni-Al intermetallic compounds using differential scanning calorimetry technique; Determinacao das entalpias de formacao de intermetalicos do sistema Ni-Al atraves da tecnica de calorimetria diferencial de varredura

    Energy Technology Data Exchange (ETDEWEB)

    Kubaski, Evaldo Toniolo; Capocchi, Jose Deodoro Trani, E-mail: evaldotk@usp.br, E-mail: jdtcapoc@usp.br [Universidade de Sao Paulo (EP/USP), Sao Paulo, SP (Brazil). Escola Politecnica. Dept. de Engenharia Metalurgica e de Materiais; Cintho, Osvaldo Mitsuyuki, E-mail: omcintho@uepg.br [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    The compositions Ni20Al80, Ni25Al75, Ni40Al60, Ni50Al50, Ni60Al40 and Ni75Al25 (at. %) were heated in a calibrated thermal analysis equipment. All runs were conducted at a heating rate of 10 deg C/min under a dynamic argon atmosphere. Each composition was heated until the completion of the corresponding exothermic reaction responsible for intermetallic compound formation, and, also heated to 1480 deg C. The products obtained were characterized using X ray diffraction in order to identify the intermetallic compounds that were synthesized. Moreover, the results were evaluated using variance analysis. As a result, enthalpies of formation of Ni{sub 2}Al{sub 3} and Ni{sub 3}Al compounds were determined by means of this methodology. Experimental values were 167 kJ/mol and 93 kJ/mol for Ni{sub 2}Al{sub 3} and Ni{sub 3}Al, respectively. The former is 18% lower than the value found on literature, while the latter is 6% greater. (author)

  17. Desenvolvimento de um equipamento para avaliação do efeito do etanol na pressão de vapor e entalpia de vaporização em gasolinas automotivas Development of a device to valuate the effect of ethanol on the vapor pressure and vaporization enthalpy of fuel gasolines

    Directory of Open Access Journals (Sweden)

    Renato Cataluña

    2006-06-01

    Full Text Available The quality of the gasoline utilized for fueling internal combustion engines with spark ignition is directly affected by the gasoline's properties. Thus, the fuel's properties must be in perfect equilibrium to allow the engine to perform optimally, not only insofar as fuel consumption is concerned, but also in order to reduce the emission of pollutants. Vapor pressure and vaporization enthalpy are important properties of a gasoline determining the fuel's behavior under different operating conditions in internal combustion engines. The study reported here involved the development of a device to determine the vapor pressure and the vaporization enthalpy of formulations containing volumes of 5, 15 and 25% of ethanol in four base gasolines (G1, G2, G3 and G4. The chemical composition of these gasolines was determined using a gas chromatographer equipped with a flame ionization detector (FID.

  18. Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

    Science.gov (United States)

    Pal, Rumpa; Reddy, M B Madhusudana; Dinesh, Bhimareddy; Balaram, Padmanabhan; Guru Row, Tayur N

    2014-10-09

    Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components. The thermal behavior of the dipeptide crystals was characterized by differential scanning calorimetry experiments. Visual changes in birefringence of the sample during heating and cooling cycles on a hot-stage microscope with polarized light supported the phase transition. Variable-temperature unit cell check measurements from 300 to 100 K showed discontinuity in the volume and cell parameters near the transition temperature, supporting the first-order behavior. A detailed comparison of the room-temperature orthorhombic form with the low-temperature (100 K) monoclinic form revealed that the strong hydrogen-bonding motif is retained in both crystal systems, whereas the non-covalent interactions involving side chains of the dipeptide differ significantly, leading to a small change in molecular conformation in the monoclinic form as well as a small reorientation of the molecules along the ac plane. A rigid-body thermal motion analysis (translation, libration, screw; correlation of translation and libration) was performed to study the crystal entropy. The reversible nature of the phase transition is probably the result of an interplay between enthalpy and entropy: the low-temperature monoclinic form is enthalpically favored, whereas the room-temperature orthorhombic form is entropically favored.

  19. Enthalpy - Improved Dielectric Insulation for Superconducting Wires.

    Science.gov (United States)

    1982-05-01

    NbTi at -350 0 C; (3) SC-3 materials, which might be hot-extruded onto NbSn atcw 600’C; and (4) Composites of powders of the SC-I ceramics cast into...which might be hot-extruded onto NbSn at Z 600’C; and (4) Composites of powders of the SC-I ceramics cast into glass and varnish matrices. Thermal...it is :itci tlit the composites with SC-I C have somewhat smaller porno It ,,, iartiii!,irv at the lower powder contents. Specific Heat

  20. Low enthalpy convective system in Western Ohio

    Energy Technology Data Exchange (ETDEWEB)

    Cannon, M.S.; Tabet, C.A.; Eckstein, Y.

    1980-01-01

    A distinct positive anomaly in the temperatures of the shallow (Pleistocene) aquifers along the Cincinnati-Findlay Arch in Western Ohio coincides with a low geothermal gradient. A conceptual model of convective currents associated with a tensional fault and/or fracture system along the crest of the Arch is suggested as an explanation of the anomaly. Hydrochemical information indicates that various quantities of warmer ground water, with the composition characteristics of deep bedrock aquifers, is present as an admixture in the shallow aquifers. This confirms the conceptual model of convection in fractures.

  1. Predicting formation enthalpies of metal hydrides

    DEFF Research Database (Denmark)

    Andreasen, A.

    2004-01-01

    In order for the hydrogen based society viz. a society in which hydrogen is the primary energy carrier to become realizable an efficient way of storing hydrogen is required. For this purpose metal hydrides are serious candidates. Metal hydrides are formedby chemical reaction between hydrogen...

  2. Relativity made relatively easy

    CERN Document Server

    Steane, Andrew M

    2012-01-01

    Relativity Made Relatively Easy presents an extensive study of Special Relativity and a gentle (but exact) introduction to General Relativity for undergraduate students of physics. Assuming almost no prior knowledge, it allows the student to handle all the Relativity needed for a university course, with explanations as simple, thorough, and engaging as possible.The aim is to make manageable what would otherwise be regarded as hard; to make derivations as simple as possible and physical ideas as transparent as possible. Lorentz invariants and four-vectors are introduced early on, but tensor not

  3. The Relation between Immersion Calorimetry and the Parameters of the Water Adsorption Isotherm on Active Carbons

    OpenAIRE

    Kraehenbuehl, Francis; Quellet, Christian; Schmitter, Beat; Stoeckli, Fritz

    2007-01-01

    It is shown that for active carbons with a single type of hydrophilic adsorption sites, the enthalpy of immersion into water is related to the number of sites, a0, and to a parameter, c, both of which appear in the Dubinin–Serpinskii equation for the water adsorption isotherm. The correlation was established on the basis of data for 13 different active carbons whose sites were either acidic or of the carbonyl type. It follows that the adsorption branch of the water isotherm can be calculated ...

  4. Determinação da entalpia de vaporização de líquidos pelo método do isoteniscópio de Smith e Menzies Determination of the enthalpy of vaporization of liquid compounds by the Smith Menzies (isoteniscope method

    Directory of Open Access Journals (Sweden)

    Adriana Passarella Gerola

    2010-01-01

    Full Text Available This article proposes an experimental procedure to determine the enthalpy (and entropy of vaporization of organic liquid compounds, by the Smith-Menzies (isoteniscope method. The values of vapor pressure at different temperatures were obtained and ΔvH (and ΔvS were graphically determined, using the Clausius-Clapeyron equation. The results for diethyl-ether, propanone, ethanol and n-hexane are in very good agreement with those from literature. A historical and thermodynamic discussion on equations that correlates vapor pressures and temperature precedes the experimental proposition.

  5. Relational databases

    CERN Document Server

    Bell, D A

    1986-01-01

    Relational Databases explores the major advances in relational databases and provides a balanced analysis of the state of the art in relational databases. Topics covered include capture and analysis of data placement requirements; distributed relational database systems; data dependency manipulation in database schemata; and relational database support for computer graphics and computer aided design. This book is divided into three sections and begins with an overview of the theory and practice of distributed systems, using the example of INGRES from Relational Technology as illustration. The

  6. Social relations

    DEFF Research Database (Denmark)

    Due, P; Holstein, B; Lund, R

    1999-01-01

    We introduce a conceptual framework with social relations as the main concept and the structure and the function of social relations as subconcepts. The structure of social relations covers aspects of formal relations and social network. The function of social relations covers social support......, social anchorage and relational strain. We use this conceptual framework to describe social relations in the Danish population, with questionnaire data from the Danish Longitudinal Health Behaviour Study including a random sample of each of the age groups 25-, 50-, 60-and 70-year olds, N = 2......,011. The postal questionnaires were answered by a random sample in each of the age groups. The results show marked age and gender differences in both the structure and the function of social relations. The social network, measured as weekly contacts, weakens with age and so does instrumental support. Emotional...

  7. Relational Leadership

    DEFF Research Database (Denmark)

    Madsen, Charlotte Øland; Rasmussen, Jørgen Gulddahl

    2015-01-01

    In this chapter, we emphasise what we have outlined as interesting areas of relational leadership and present some ideas on how to facilitate a broader understanding of relational leadership practice. This involves the interpretations that create connections between practice and ontology. We...... elaborate on how leadership in everyday situations can be understood from a relational perspective. The chapter will focus on outlining and inspiring the reader to co-operate with other people to develop further relational understandings of leading....

  8. Numerical relativity

    CERN Document Server

    Shibata, Masaru

    2016-01-01

    This book is composed of two parts: First part describes basics in numerical relativity, that is, the formulations and methods for a solution of Einstein's equation and general relativistic matter field equations. This part will be helpful for beginners of numerical relativity who would like to understand the content of numerical relativity and its background. The second part focuses on the application of numerical relativity. A wide variety of scientific numerical results are introduced focusing in particular on the merger of binary neutron stars and black holes.

  9. The Thermodynamics of the Krebs Cycle and Related Compounds

    Science.gov (United States)

    Miller, Stanley L.; Smith-Magowan, David

    1990-07-01

    A survey is made of the enthalpies of formation, third law entropies and Gibbs energies available for Krebs cycle and related compounds. These include formate, acetate, succinate, fumarate, glycine, alanine, aspartate and glutamate. The potential of the NAD+/NADH couple is recalculated based on the ethanol/acetaldehyde and isopropanol/acetone equilibria. The reported enzyme catalyzed equilibrium constants of the Krebs cycle reactions are evaluated with estimated errors. These 28 equilibria form a network of reactions that is solved by a least squares regression procedure giving Gibbs energies of formation for 21 Krebs cycle and related compounds. They appear to be accurate to ±0.4 kJṡmol-1 for some compounds but ±1 kJṡmol-1 in less favorable cases. This procedure indicates which third law ΔfG and enzyme equilibria are inaccurate, and allows very accurate ΔfG to be determined for compounds related to the Krebs cycle by measuring enzyme equilibrium constants.

  10. Numerical Relativity

    Science.gov (United States)

    Baker, John G.

    2009-01-01

    Recent advances in numerical relativity have fueled an explosion of progress in understanding the predictions of Einstein's theory of gravity, General Relativity, for the strong field dynamics, the gravitational radiation wave forms, and consequently the state of the remnant produced from the merger of compact binary objects. I will review recent results from the field, focusing on mergers of two black holes.

  11. View relations

    DEFF Research Database (Denmark)

    Knudsen, Søren; Carpendale, Sheelagh

    2016-01-01

    In this paper, we explore the potential of using visual representations to support people in managing, organizing, and understanding relations between multiple visualization views. Multiple views can help people understand different facets of data and data processing, and are a crucial part of data...... analysis particularly when it is done collaboratively. Both the growing use of multiple views and the increasing display sizes have amplified the need to explore how to better help people to understand the relations between many views. To improve our understanding of how to visualize view relations, we...... invited visualization and interaction designers to critique and sketch representations of view relations. The participants provided design critiques, and sketched their own relation representations. Our findings expand the range and palette of ways of visually linking visualization views and suggest new...

  12. Relational Blackboard

    Energy Technology Data Exchange (ETDEWEB)

    2012-09-11

    The Relational Blackboard (RBB) is an extension of the H2 Relational Database to support discrete events and timeseries data. The original motivation for RBB is as a knowledge base for cognitive systems and simulations. It is useful wherever there is a need for persistent storage of timeseries (i.e. samples of a continuous process generating numerical data) and semantic labels for the data. The RBB is an extension to the H2 Relational Database, which is open-source. RBB is a set of stored procedures for H2 allowing data to be labeled, queried, and resampled.

  13. Discourses of relations and relational

    NARCIS (Netherlands)

    Hosking, D.M.

    2006-01-01

    This is a story of relations and relating. There is no wolf, no Little Red Riding Hood; there are no bears, nor little piggies. It is not a heroic tale of how one particular discourse proves its superiority by vanquishing other discourses; it is not a tale told from behind the wings, the

  14. Relational diversity.

    Science.gov (United States)

    Gregorius, Hans-Rolf

    2009-03-07

    In biology, the measurement of diversity traditionally focusses on reporting number of unambiguously distinguishable types, thus referring to qualitative (discontinuously varying) traits. Inclusion of frequencies or other weights has produced a large variety of diversity indices. Quantitative (continuously varying) traits do not readily fit into this perspective. In fact, in the context of quantitative traits, the concept of diversity is not always clearly distinguished from the (statistical) notion of dispersion. In many cases the ambiguity even extends to qualitative traits. This is at variance with the broad spectrum of diversity issues ranging, e.g., from ecological and genetic aspects of diversity to functional, structural, systematic, or evolutionary (including phylogenetic) aspects. In view of the urgent need for a more consistent perspective, it is called to attention that all of these aspects, whether of qualitative or quantitative nature, can be gathered under the common roof of binary relations (for qualitative traits two objects are related, for example, if they share the same trait state). A comprehensive concept of (relational) diversity can be developed in two steps: (1) determine the number of unrelated pairs of objects among all admissible pairs as a measure of implicit (relative) diversity, (2) invoke the concept of effective number to transform the implicit measure of diversity into an explicit (absolute) measure. The transformation operates by equating the observed implicit diversity to the implicit diversity obtained for the ideal model of an equivalence relation with classes of equal size. The number of these classes specifies the effective number as an explicit measure of diversity. The wealth of problems that can be treated from this unified perspective is briefly addressed by classifying and interpreting established diversity indices in the light of relational diversity. Desirable applications to the above-mentioned aspects are specified

  15. Relational Leading

    DEFF Research Database (Denmark)

    Larsen, Mette Vinther; Rasmussen, Jørgen Gulddahl

    2015-01-01

    This first chapter presents the exploratory and curious approach to leading as relational processes – an approach that pervades the entire book. We explore leading from a perspective that emphasises the unpredictable challenges and triviality of everyday life, which we consider an interesting......, relevant and realistic way to examine leading. The chapter brings up a number of concepts and contexts as formulated by researchers within the field, and in this way seeks to construct a first understanding of relational leading....

  16. Linguistic relativity.

    Science.gov (United States)

    Wolff, Phillip; Holmes, Kevin J

    2011-05-01

    The central question in research on linguistic relativity, or the Whorfian hypothesis, is whether people who speak different languages think differently. The recent resurgence of research on this question can be attributed, in part, to new insights about the ways in which language might impact thought. We identify seven categories of hypotheses about the possible effects of language on thought across a wide range of domains, including motion, color, spatial relations, number, and false belief understanding. While we do not find support for the idea that language determines the basic categories of thought or that it overwrites preexisting conceptual distinctions, we do find support for the proposal that language can make some distinctions difficult to avoid, as well as for the proposal that language can augment certain types of thinking. Further, we highlight recent evidence suggesting that language may induce a relatively schematic mode of thinking. Although the literature on linguistic relativity remains contentious, there is growing support for the view that language has a profound effect on thought. WIREs Cogni Sci 2011 2 253-265 DOI: 10.1002/wcs.104 For further resources related to this article, please visit the WIREs website. Copyright © 2010 John Wiley & Sons, Ltd.

  17. Weak relativity

    CERN Document Server

    Selleri, Franco

    2015-01-01

    Weak Relativity is an equivalent theory to Special Relativity according to Reichenbach’s definition, where the parameter epsilon equals to 0. It formulates a Neo-Lorentzian approach by replacing the Lorentz transformations with a new set named “Inertial Transformations”, thus explaining the Sagnac effect, the twin paradox and the trip from the future to the past in an easy and elegant way. The cosmic microwave background is suggested as a possible privileged reference system. Most importantly, being a theory based on experimental proofs, rather than mutual consensus, it offers a physical description of reality independent of the human observation.

  18. General Relativity

    CERN Document Server

    Straumann, Norbert

    2013-01-01

    This book provides a completely revised and expanded version of the previous classic edition ‘General Relativity and Relativistic Astrophysics’. In Part I the foundations of general relativity are thoroughly developed, while Part II is devoted to tests of general relativity and many of its applications. Binary pulsars – our best laboratories for general relativity – are studied in considerable detail. An introduction to gravitational lensing theory is included as well, so as to make the current literature on the subject accessible to readers. Considerable attention is devoted to the study of compact objects, especially to black holes. This includes a detailed derivation of the Kerr solution, Israel’s proof of his uniqueness theorem, and a derivation of the basic laws of black hole physics. Part II ends with Witten’s proof of the positive energy theorem, which is presented in detail, together with the required tools on spin structures and spinor analysis. In Part III, all of the differential geomet...

  19. Training Relations

    DEFF Research Database (Denmark)

    Smith, Aja

    contribution of the thesis is to illustrate the analytical and ethical importance of rendering these sensorial, bodily and affective dimensions of phenomena sensible. The thesis also contributes to the charting of Denmark ethnographically, sketching the relations between perceptions of “proper sociality...

  20. Readable relativity

    CERN Document Server

    Durell, Clement V

    2003-01-01

    Concise and practical, this text by a renowned teacher sketches the mathematical background essential to understanding the fundamentals of relativity theory. Subjects include the velocity of light, measurement of time and distance, and properties of mass and momentum, with numerous diagrams, formulas, and examples, plus exercises and solutions. 1960 edition.

  1. Readable relativity

    CERN Document Server

    Durell, Clement V

    1962-01-01

    Concise and practical, this text by a renowned teacher sketches the mathematical background essential to understanding the fundamentals of relativity theory. Subjects include the velocity of light, measurement of time and distance, and properties of mass and momentum, with numerous diagrams, formulas, and examples, plus exercises and solutions. 1960 edition.

  2. International Relations:

    DEFF Research Database (Denmark)

    This is the textbook for the Open University module International Relations: Continuity and Change in Global Politics. Instead of leading with a succession of theoretical 'isms', the module structures its presentation of the subject around six teaching ‘blocks’, each of which explores a dilemma......, or dimension of variation. The dilemmas in question were chosen for the way they capture key themes in the field of International Studies (IR) as well as central aspects of the ‘international’ itself (ir). The six Blocks are: • Block 1: Co-operation or conflict? Introducing international relations • Block 2......: Flat or uneven? Change and transformation in the international system • Block 3: Just or unjust? Intervention and inequality in the international system • Block 4: Top-down or bottom-up? Governance in the international system • Block 5: Secure or insecure? Pursuing security in the international system...

  3. Distant Relations

    DEFF Research Database (Denmark)

    Søndergaard, Morten

    2011-01-01

    Art EntrepreneurshipIvo Zander Mikael Scherdin This project is funded and sponsored by the Knowledge Foundation, the Bank of Sweden Tercentenary Foundation, and the Department of Business Studies, Uppsala University2008-2009This cutting edge project asks what art and artistic processes can contri......) Entrepreneurship on the art arena - An ecological perspective (Mikael Scherdin and Ivo Zander) Distant relations - Art practice in a global culture (Morten Søndergaard) Art entrepreneurship - A commentary (Daved Barry) Summary and policy implications (Mikael Scherdin and Ivo Zander)...

  4. Basic relativity

    CERN Document Server

    Mould, Richard A

    1994-01-01

    This comprehensive textbook develops in a logical and coherent way both the formalism and the physical ideas of special and general relativity. Part one focuses on the special theory and begins with the study of relativistic kinematics from three points of view. Part two begins with a chapter introducing differential geometry. Subsequent chapters cover: rotation, the electromagnetic field, and material media. A second chapter on differential geometry provides the background for Einstein's gravitational-field equation and Schwarzschild's solution. The book is aimed at advanced undergraduates and beginning graduate students in physics or astrophysics.

  5. General Relativity

    CERN Document Server

    Canuto, V

    2015-01-01

    This is an English translation of the Italian version of an encyclopedia chapter that appeared in the Italian Encyclopedia of the Physical Sciences, edited by Bruno Bertotti (1994). Following requests from colleagues we have decided to make it available to a more general readership. We present the motivation for constructing General Relativity, provide a short discussion of tensor algebra, and follow the set up of Einstein equations. We discuss briefly the initial value problem, the linear approximation and how should non gravitational physics be described in curved spacetime.

  6. Modified enthalpy method for the simulation of melting and ...

    Indian Academy of Sciences (India)

    While simulatingmelting with natural convection, in order to impose no-slip and impermeability boundary conditions, momentum sink terms are used with some arbitrary constants called mushy zone constants. The values of these are very large and have no physical basis. Further, the chosen values affect the predictions ...

  7. Determination of Differential Enthalpy and Isotherm by Adsorption Calorimetry

    Directory of Open Access Journals (Sweden)

    V. Garcia-Cuello

    2008-01-01

    Full Text Available An adsorption microcalorimeter for the simultaneous determination of the differential heat of adsorption and the adsorption isotherm for gas-solid systems are designed, built, and tested. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K=154.34±0.23 WV−1. The adsorption microcalorimeter is used to obtain adsorption isotherms and the corresponding differential heats for the adsorption of CO2 on a reference solid, such as a NaZSM-5 type zeolite. Results for the behavior of this system are compared with those obtained with commercial equipment and with other studies in the literature.

  8. Hypervelocity Expansion Facility for Fundamental High-Enthalpy Research

    Science.gov (United States)

    2017-02-27

    of thumb of 70% are 0.239-in for the width and 0.147-in for the depth. Because all the grooves for the adapter and access panels have linear lengths...to avoid high EMF areas o Be sealed against dust and fluids • Pressure input should be an analog to digital converter ( ADC ) input with the following

  9. Determination of Differential Enthalpy and Isotherm by Adsorption Calorimetry

    OpenAIRE

    Garcia-Cuello, V.; Moreno-Piraján, J. C; Giraldo-Gutiérrez, L.; K. Sapag; Zgrablich, G.

    2008-01-01

    An adsorption microcalorimeter for the simultaneous determination of the differential heat of adsorption and the adsorption isotherm for gas-solid systems are designed, built, and tested. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K=154.34±0.23 WV−1. The adsor...

  10. Spectroscopy Measurements on Ablation Testing in High Enthalpy Plasma Flows

    Science.gov (United States)

    2010-11-01

    two-colour Raytek Marathon MR1S-C pyrometer (0.75 − 1.1μm), with a temperature range from 1000°C to 3000°C. It measures the infrared radiation of a...18 3.5.2 PYROMETER ...might undergo additional chemical reactions, creating highly radiating species which can increase the radiative heat flux. Figure 1-2: Process of

  11. Phase Change Enthalpies and Entropies of Liquid Crystals

    National Research Council Canada - National Science Library

    Acree, William E; Chickos, James S

    2006-01-01

    .... A group additivity approach used to estimate total phase change entropies of organic molecules applied to 627 of these liquid crystals is found to significantly overestimate their total phase change entropies...

  12. Enthalpy and entropy effects in hydrogen adsorption on carbon nanotubes.

    Science.gov (United States)

    Efremenko, Irena; Sheintuch, Moshe

    2005-07-05

    Interaction energies and entropies associated with hydrogen adsorption on the inner and outer surfaces of zigzag single-wall carbon nanotubes (SWCNT) of various diameters are analyzed by means of molecular mechanics, density functional theory, and ab initio calculations. For a single molecule the strongest interaction, which is 3.5 greater than that with the planar graphite sheet, is found inside a (8,0) nanotube. Adsorption on the outer surfaces is weaker than that on graphite. Due to the steric considerations, both processes are accompanied by an extremely strong decline in entropy. Absence of specific adsorption sites and weak attractive interaction between hydrogen molecules within carbon nanotubes results in their close packing at low temperatures. Using the calculated geometric and thermodynamic parameters in Langmuir isotherms we predict the adsorption capacity of SWCNTs at room temperature to be smaller than 1 wt % even at 100 bar.

  13. Special relativity

    CERN Document Server

    Faraoni, Valerio

    2013-01-01

    This book offers an essential bridge between college-level introductions and advanced graduate-level books on special relativity. It begins at an elementary level, presenting and discussing the basic concepts normally covered in college-level works, including the Lorentz transformation. Subsequent chapters introduce the four-dimensional worldview implied by the Lorentz transformations, mixing time and space coordinates, before continuing on to the formalism of tensors, a topic usually avoided in lower-level courses. The book’s second half addresses a number of essential points, including the concept of causality; the equivalence between mass and energy, including applications; relativistic optics; and measurements and matter in Minkowski spacetime. The closing chapters focus on the energy-momentum tensor of a continuous distribution of mass-energy and its covariant conservation; angular momentum; a discussion of the scalar field of perfect fluids and the Maxwell field; and general coordinates. Every chapter...

  14. General Relativity

    CERN Document Server

    Khriplovich, I. B

    2005-01-01

    This book offers an alternative to other textbooks on the subject, providing a more specific discussion of numerous general relativistic effects for readers who have knowledge of classical mechanics and electrodynamics, including special relativity. Coverage includes gravitational lensing, signal retardation in the gravitational field of the Sun, the Reissner-Nordström solution, selected spin effects, the resonance transformation of an electromagnetic wave into a gravitational one, and the entropy and temperature of black holes. The book includes numerous problems at various levels of difficulty, making it ideal also for independent study by a broad readership of advanced students and researchers. I.B. Khriplovich is Chief Researcher, Budker Institute of Nuclear Physics, Novosibirsk, and Chair of Theoretical Physics at Novosibirsk University. Dr. Khriplovich is a Corresponding Member of the Russian Academy of Sciences. He has been awarded the Dirac Medal ``For the advancement of theoretical physics'' by Univ...

  15. Numerical relativity

    CERN Document Server

    Nakamura, T

    1993-01-01

    In GR13 we heard many reports on recent. progress as well as future plans of detection of gravitational waves. According to these reports (see the report of the workshop on the detection of gravitational waves by Paik in this volume), it is highly probable that the sensitivity of detectors such as laser interferometers and ultra low temperature resonant bars will reach the level of h ~ 10—21 by 1998. in this level we may expect the detection of the gravitational waves from astrophysical sources such as coalescing binary neutron stars once a year or so. Therefore the progress in numerical relativity is urgently required to predict the wave pattern and amplitude of the gravitational waves from realistic astrophysical sources. The time left for numerical relativists is only six years or so although there are so many difficulties in principle as well as in practice.

  16. Experimental evaluation of enthalpy efficiency and gas-phase contaminant transfer in an enthalpy recovery unit with polymer membrane foils

    DEFF Research Database (Denmark)

    Nie, Jinzhe; Yang, Jianrong; Fang, Lei

    2015-01-01

    and outdoor air by twin chambers was connected to the unit. Three chemical gases were dosed to the indoor exhaust air to mimic indoor air contaminants. Based on the measurements of temperature, humidity ratio, and contaminant concentrations of the indoor exhaust air and outdoor air supply upstream...

  17. Entalpía de disolución de sulfacetamida sódica en agua: comparación entre la calorimetría isoperibólica de solución y el método de van't Hoff Dissolution enthalpy of sodium sulfacetamide in water: comparison between solution isoperibolic calorimetry and the van't Hoff method

    Directory of Open Access Journals (Sweden)

    Daniel R. Torres

    2008-01-01

    Full Text Available The dissolution enthalpy (ΔH0soln of sodium sulfacetamide in water was determined by means of isoperibolic solution calorimetry. It was found that ΔH0soln diminishes as the drug concentration increases. Otherwise, the calorimetric values obtained as a function of the drug concentration were significantly different than those predicted by the van't Hoff method. It was demonstrated that the later is not a fully reliable method for the determination of ΔH0soln values in the specific case of highly soluble sodium salts. The observed phenomenon could be explained by the presence of strong solute-solute interactions at high salt concentrations, in addition to solute-solvent and solvent-solvent interactions.

  18. Possible existence of two amorphous phases of D-mannitol related by a first-order transition

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Men; Yu, Lian, E-mail: lian.yu@wisc.edu [Department of Chemistry and School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Wang, Jun-Qiang; Perepezko, John H. [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2015-06-28

    We report that the common polyalcohol D-mannitol may have two amorphous phases related by a first-order transition. Slightly above its glass transition temperature T{sub g} (284 K), the supercooled liquid (SCL) of D-mannitol transforms to a low-energy, apparently amorphous phase with stronger hydrogen bonds. The enthalpy of this so-called Phase X is approximately halfway between those of the known amorphous and crystalline phases, a position low for glass aging and high for crystal polymorphs. Similar to the SCL, Phase X is transparent with broad X-ray diffraction and Raman scattering; upon temperature cycling, it exhibits a glass-transition-like change of heat capacity. On fast heating, Phase X transforms back to the SCL near T{sub g} + 50 K, enabling a determination of their equilibrium temperature. The presence of D-sorbitol as a plasticizer enables observation of a first-order transition from the SCL to Phase X entirely in the liquid state (liquid-liquid transition). The transition from D-mannitol’s SCL to Phase X has intriguing similarities with the formation of the glacial phase of triphenyl phosphite (TPP) and the conversion from high-density to low-density amorphous ice, both studied intensely in the context of polyamorphism. All three processes occur near T{sub g} with substantial enthalpy decrease toward the crystalline phases; the processes in water and D-mannitol both strengthen the hydrogen bonds. In contrast to TPP, D-mannitol’s Phase X forms more rapidly and can transform back to the SCL. These features make D-mannitol a valuable new model for understanding polyamorphism.

  19. Social relations: network, support and relational strain

    DEFF Research Database (Denmark)

    Due, P; Holstein, B; Lund, Rikke

    1999-01-01

    We introduce a conceptual framework with social relations as the main concept and the structure and the function of social relations as subconcepts. The structure of social relations covers aspects of formal relations and social network. The function of social relations covers social support......,011. The postal questionnaires were answered by a random sample in each of the age groups. The results show marked age and gender differences in both the structure and the function of social relations. The social network, measured as weekly contacts, weakens with age and so does instrumental support. Emotional...... support is unrelated to this decline in contact frequency and appears to be at the same level for younger and older individuals. Relational strain, measured as conflicts, declines with age for all kinds of social relations. The weakening of the social network with age does not seem to affect the level...

  20. The thermodynamics of protein folding: a critique of widely used quasi-thermodynamic interpretations and a restatement based on the Gibbs-Duhem relation and consistent with the Phase Rule.

    Science.gov (United States)

    Pethica, Brian A

    2010-07-21

    Interpretations of data in the extensive literature on the unfolding of proteins in aqueous solution follow a variety of methods involving assumptions leading to estimates of thermodynamic quantities associated with the unfolding transition. Inconsistencies and thermodynamic errors in these methods are identified. Estimates of standard molar free energies and enthalpies of unfolding using incompletely defined equilibrium constants and the van't Hoff relation are unsound, and typically contradict model-free interpretation of the data. A widely used routine for estimating the change in heat capacity associated with unfolding based on changes in the unfolding temperature and enthalpy co-induced by addition of denaturant or protective additives is thermodynamically incorrect by neglect of the Phase Rule. Many models and simulations predicting thermodynamic measures of unfolding are presently making comparisons with insecure quantities derived by incorrect thermodynamic analyses of experimental data. Analysis of unfolding via the Gibbs-Duhem equation with the correct Phase Rule constraints avoids the assumptions associated with incomplete equilibrium constants and misuse of the van't Hoff relation, and applies equally to positive, negative, sitewise or diffuse solute binding to the protein. The method gives the necessary relations between the thermodynamic parameters for thermal and isothermal unfolding and is developed for the case of two-state unfolding. The differences in binding of denaturants or stabilizers to the folded and unfolded forms of the protein are identified as major determinants of the unfolding process. The Phase Rule requires the temperature and enthalpy of unfolding to depend generally on the protein concentration. The available evidence bears out this expectation for thermal unfolding, indicating that protein-protein interactions influence folding. A parallel dependence of the denaturant concentrations for isothermal unfolding on the protein

  1. Incorporating Relation Paths in Neural Relation Extraction

    OpenAIRE

    Zeng, Wenyuan; Lin, Yankai; Liu, Zhiyuan; Sun, Maosong

    2016-01-01

    Distantly supervised relation extraction has been widely used to find novel relational facts from plain text. To predict the relation between a pair of two target entities, existing methods solely rely on those direct sentences containing both entities. In fact, there are also many sentences containing only one of the target entities, which provide rich and useful information for relation extraction. To address this issue, we build inference chains between two target entities via intermediate...

  2. Social relations: network, support and relational strain.

    Science.gov (United States)

    Due, P; Holstein, B; Lund, R; Modvig, J; Avlund, K

    1999-03-01

    We introduce a conceptual framework with social relations as the main concept and the structure and the function of social relations as subconcepts. The structure of social relations covers aspects of formal relations and social network. The function of social relations covers social support, social anchorage and relational strain. We use this conceptual framework to describe social relations in the Danish population, with questionnaire data from the Danish Longitudinal Health Behaviour Study including a random sample of each of the age groups 25-, 50-, 60-and 70-year olds, N = 2,011. The postal questionnaires were answered by a random sample in each of the age groups. The results show marked age and gender differences in both the structure and the function of social relations. The social network, measured as weekly contacts, weakens with age and so does instrumental support. Emotional support is unrelated to this decline in contact frequency and appears to be at the same level for younger and older individuals. Relational strain, measured as conflicts, declines with age for all kinds of social relations. The weakening of the social network with age does not seem to affect the level of emotional support and in turn seems to be partly compensated for by a simultaneous decline in relational strain.

  3. Estimation of production characteristic curves of geothermal wells and of the permeability of rocky formations through one single mass flow-pressure-enthalpy (W-P-h) measurement at the wellhead; Estimacion de curvas caracteristicas de produccion de pozos geotermicos y de permeabilidades de formaciones rocosas a partir de una sola medicion flujo masico-presion- entalpia (W-P-h) a boca de pozo

    Energy Technology Data Exchange (ETDEWEB)

    L Moya, Sara; Aragon, Alfonso [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1997-12-31

    The proposed methodology described ahead (Moya et al.,1996; Moya et al.,1997a, 1997b and 1997c) simplifies the construction of production characteristic curves of geothermal wells and of its associated thermal productivity, in requiring one single measurement of mass flow-pressure-enthalpy (W-P-h) at the wellhead. Therefore it is an ecological option, technically and economically more feasible. On the other hand, the methodology also allows to diagnose the rocky formation absolute permeability in the well feeding zone. This permeability is usually determined through well bottom pressure tests, than in some cases are difficult to interpret. The permeability inferred by means of the proposed technology represents a complementary tool for these field tests and for the laboratory measurements on drilling cores. [Espanol] La metodologia propuesta que se describe a continuacion [Moya et al., 1995d; Moya et al., 1996; Moya et al., 1997a, 1997b y 1997c] simplifica la construccion de curvas caracteristicas de produccion de pozos geotermicos y de su productividad termica asociada al requerir solo una medicion de flujo masico-presion-entalpia (W-P-h) a boca de pozo. Es por tanto una alternativa ecologica, tecnica y economicamente mas factible. Por otra parte, la metodologia tambien permite diagnosticar el valor de la permeabilidad absoluta de la formacion rocosa en la zona de alimentacion al pozo. Esta permeabilidad se determina usualmente a partir de pruebas de presion a fondo de pozo que en algunos casos son dificiles de interpretar. La permeabilidad inferida mediante la metodologia propuesta representa una herramienta complementaria a estas pruebas de campo y a las mediciones de laboratorio sobre nucleos de perforacion.

  4. Tests Related to Pregnancy

    Science.gov (United States)

    ... what you want to learn. Search form Search Tests related to pregnancy You are here Home Testing & Services Testing for ... Genes: A Guide to Genetic Counseling . What Are Tests Related to Pregnancy? Pregnancy related testing is done before or during ...

  5. Understanding Causal Coherence Relations

    NARCIS (Netherlands)

    Mulder, G.

    2008-01-01

    The research reported in this dissertation focuses on the cognitive processes and representations involved in understanding causal coherence relations in text. Coherence relations are the meaning relations between the information units in the text, such as Cause-Consequence. These relations can be

  6. Introduction to relation algebras relation algebras

    CERN Document Server

    Givant, Steven

    2017-01-01

    The first volume of a pair that charts relation algebras from novice to expert level, this text offers a comprehensive grounding for readers new to the topic. Upon completing this introduction, mathematics students may delve into areas of active research by progressing to the second volume, Advanced Topics in Relation Algebras; computer scientists, philosophers, and beyond will be equipped to apply these tools in their own field. The careful presentation establishes first the arithmetic of relation algebras, providing ample motivation and examples, then proceeds primarily on the basis of algebraic constructions: subalgebras, homomorphisms, quotient algebras, and direct products. Each chapter ends with a historical section and a substantial number of exercises. The only formal prerequisite is a background in abstract algebra and some mathematical maturity, though the reader will also benefit from familiarity with Boolean algebra and naïve set theory. The measured pace and outstanding clarity are particularly ...

  7. The Fundamental Property Relation.

    Science.gov (United States)

    Martin, Joseph J.

    1983-01-01

    Discusses a basic equation in thermodynamics (the fundamental property relation), focusing on a logical approach to the development of the relation where effects other than thermal, compression, and exchange of matter with the surroundings are considered. Also demonstrates erroneous treatments of the relation in three well-known textbooks. (JN)

  8. Matrix relation algebras

    NARCIS (Netherlands)

    el Bachraoui, M.; van de Vel, M.L.J.

    2002-01-01

    Square matrices over a relation algebra are relation algebras in a natural way. We show that for fixed n, these algebras can be characterized as reducts of some richer kind of algebra. Hence for fixed n, the class of n × n matrix relation algebras has a first-order characterization. As a

  9. Relativity and cosmology

    CERN Document Server

    Kaufmann, William J

    1973-01-01

    The foundations of gravitational theory ; the birth of relativity theory ; the foundations of general relativity ; experimental tests of relativity ; the meaning of the redshift ; the black hole ; wormholes and white holes ; galaxies and quasars ; gravitational waves ; the shape of the Universe ; the creation of the Universe.

  10. 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...

  11. Space, Time and Relativity

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 7 ... General Article Volume 11 Issue 7 July 2006 pp 14-29 ... Galilean relativity; inertial frames; Newtonian mechanics; Maxwell electromagnetism; special relativity; non Euclidean geometry; principle of equiva ence; general relativity; absolute ...

  12. Bellman goes Relational

    NARCIS (Netherlands)

    Kersting, Kristian; van Otterlo, M.; De Raedt, Luc; Greiner, R.; Schuurmans, D.

    2004-01-01

    Motivated by the interest in relational reinforcement learning, we introduce a novel relational Bellman update operator called ReBel. It employs a constraint logic programming language to compactly represent Markov decision processes over relational domains. Using ReBel, a novel value iteration

  13. Nothing but relativity

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Palash B [Saha Institute of Nuclear Physics, 1/AF Bidhan-Nagar, Calcutta 700064 (India)

    2003-05-01

    We deduce the most general space-time transformation laws consistent with the principle of relativity. Thus, our result contains the results of both Galilean and Einsteinian relativity. The velocity addition law comes as a by-product of this analysis. We also argue why Galilean and Einsteinian versions are the only possible embodiments of the principle of relativity.

  14. Making relative survival analysis relatively easy.

    Science.gov (United States)

    Pohar, Maja; Stare, Janez

    2007-12-01

    In survival analysis we are interested in time from the beginning of an observation until certain event (death, relapse, etc.). We assume that the final event is well defined, so that we are never in doubt whether the final event has occurred or not. In practice this is not always true. If we are interested in cause-specific deaths, then it may sometimes be difficult or even impossible to establish the cause of death, or there may be different causes of death, making it impossible to assign death to just one cause. Suicides of terminal cancer patients are a typical example. In such cases, standard survival techniques cannot be used for estimation of mortality due to a certain cause. The cure to the problem are relative survival techniques which compare the survival experience in a study cohort to the one expected should they follow the background population mortality rates. This enables the estimation of the proportion of deaths due to a certain cause. In this paper, we briefly review some of the techniques to model relative survival, and outline a new fitting method for the additive model, which solves the problem of dependency of the parameter estimation on the assumption about the baseline excess hazard. We then direct the reader's attention to our R package relsurv that provides functions for easy and flexible fitting of all the commonly used relative survival regression models. The basic features of the package have been described in detail elsewhere, but here we additionally explain the usage of the new fitting method and the interface for using population mortality data freely available on the Internet. The combination of the package and the data sets provides a powerful informational tool in the hands of a skilled statistician/informatician.

  15. Structure of Dihydrochalcones and Related Derivatives and Their Scavenging and Antioxidant Activity against Oxygen and Nitrogen Radical Species

    Directory of Open Access Journals (Sweden)

    Alexandre L. A. Bentes

    2011-02-01

    Full Text Available Quantum mechanical calculations at B3LYP/6-31G** level of theory were employed to obtain energy (E, ionization potential (IP, bond dissociation enthalpy (O-H BDE and stabilization energies (DEiso in order to infer the scavenging activity of dihydrochalcones (DHC and structurally related compounds. Spin density calculations were also performed for the proposed antioxidant activity mechanism of 2,4,6-trihydroxyacetophenone (2,4,6-THA. The unpaired electron formed by the hydrogen abstraction from the phenolic hydroxyl group of 2,4,6-THA is localized on the phenolic oxygen at 2, 6, and 4 positions, the C3 and C6 carbon atoms at ortho positions, and the C5 carbon atom at para position. The lowest phenolic oxygen contribution corresponded to the  highest scavenging activity value. It was found that antioxidant activity depends on the presence of a hydroxyl at the C2 and C4 positions and that there is a correlation between IP and O-H BDE and peroxynitrite scavenging activity and lipid peroxidation. These results identified the pharmacophore group for DHC.

  16. Possible Existence of Two Amorphous Phases of D-Mannitol Related by a First-Order Transition

    Science.gov (United States)

    Zhu, Men; Wang, Jun-Qiang; Perepezko, John; Yu, Lian

    We report that the common polyalcohol D-mannitol may have two amorphous phases related by a first-order transition. Slightly above Tg (284 K), the supercooled liquid (SCL) of D-mannitol transforms to a low-energy, apparently amorphous phase (Phase X). The enthalpy of Phase X is roughly halfway between those of the known amorphous and crystalline phases. The amorphous nature of Phase X is suggested by its absence of birefringence, transparency, broad X-ray diffraction, and broad Raman and NIR spectra. Phase X has greater molecular spacing, higher molecular order, fewer intra- and more inter-molecular hydrogen bonds than the normal liquid. On fast heating, Phase X transforms back to SCL near 330 K. Upon temperature cycling, it shows a glass-transition-like change of heat capacity. The presence of D-sorbitol enables a first-order liquid-liquid transition (LLT) from SCL to Phase X. This is the first report of polyamorphism at 1 atm for a pharmaceutical relevant substance. As amorphous solids are explored for many applications, polyamorphism could offer a tool to engineer the properties of materials. (Ref: M. Zhu et al., J. Chem. Phys. 2015, 142, 244504)

  17. Preliminary phase relations involving glaucophane and applications to high pressure petrology: new heat capacity and thermodynamic data

    Science.gov (United States)

    Holland, Timothy J. B.

    1988-05-01

    New heat capacity measurements and cell volume data are presented for a very magnesian glaucophane from a Tauern Window eclogite. These data are combined with estimated entropy, thermal expansion, and compressibility data to generate an enthalpy of formation for glaucophane from experimentally determined phase equilibria. The data are supported by preliminary experiments of the author and provide consistent calculations on the pressure of formation of the Tauern eclogites and on the position of the blueschist-greenschist transformation reaction as studied experimentally by Maruyama et al. (1986). The resulting thermodynamic data for glaucophane may be combined with the dataset of Holland and Powell (1985) to calculate phase relations for blueschists and eclogites. The stability of magnesian glaucophane lies in the pressure range between 8 and 32 kbars at 400° C and between 13 and 33 kbars at 600° C, and the unusual eclogite assemblage of glaucophane+kyanite from the Tauern Window is restricted to pressures above 20 kbars at high water activity.

  18. Decreasing Relative Risk Premium

    DEFF Research Database (Denmark)

    Hansen, Frank

    We consider the risk premium demanded by a decision maker with wealth x in order to be indifferent between obtaining a new level of wealth y1 with certainty, or to participate in a lottery which either results in unchanged present wealth or a level of wealth y2 > y1. We define the relative risk...... premium as the quotient between the risk premium and the increase in wealth y1–x which the decision maker puts on the line by choosing the lottery in place of receiving y1 with certainty. We study preferences such that the relative risk premium is a decreasing function of present wealth, and we determine...... relative risk premium in the small implies decreasing relative risk premium in the large, and decreasing relative risk premium everywhere implies risk aversion. We finally show that preferences with decreasing relative risk premium may be equivalently expressed in terms of certain preferences on risky...

  19. RELATED PARTY TRANSACTIONS - OVERVIEW

    OpenAIRE

    Alexandra Corlaciu; Adriana Tiron Tudor

    2011-01-01

    The purpose of the present investigation is to provide a short overview of themain implications arising from carrying related parties transactions: accounting reporting(related party disclosures - IAS 24), auditing (audit procedures for related partytransactions), taxation (issues regarding the transfer prices used for intra-grouptransactions). Although this research does not identify a problem with the scope to solve ithowever the utility might be observed by its contribution to the future d...

  20. Object relational mapping frameworks

    OpenAIRE

    Patrný, Vojtěch

    2008-01-01

    This paper is about Java object relational frameworks and related processes. The goal of this work consists of showing design patterns for ORM, introducing Java ORM standards along with the main implementations, finding criteria for comparison of ORM frameworks and showing working ORM example in a case study. This paper has the following structure: The first part of this paper discusses main ORM design patters, approaches to ORM and performance related features of Java ORM frameworks. Next pa...

  1. Gravitation and relativity

    CERN Document Server

    Bowler, Michael George

    1976-01-01

    Gravitation and Relativity generalizes Isaac Newton's theory of gravitation using the elementary tools of Albert Einstein's special relativity. Topics covered include gravitational waves, martian electrodynamics, relativistic gravitational fields and gravitational forces, the distortion of reference frames, and the precession of the perihelion of Mercury. Black holes and the geometry of spacetime also receive consideration. This book is comprised of 10 chapters; the first of which briefly reviews special relativity, with the emphasis on the Lorentz covariance of the equations of physics. This

  2. Reconstructing relational information.

    Science.gov (United States)

    Horecka, Kevin M; Dulas, Michael R; Schwarb, Hillary; Lucas, Heather D; Duff, Melissa; Cohen, Neal J

    2018-02-01

    Hippocampal involvement in learning and remembering relational information has an extensive history, often focusing specifically on spatial information. In humans, spatial reconstruction (SR) paradigms are a powerful tool for evaluating an individuals' spatial-relational memory. In SR tasks, participants study locations of items in space and subsequently reconstruct the studied display after a short delay. Previous work has revealed that patients with hippocampal damage are impaired both in overall placement accuracy as well as on a specific measure of relational memory efficacy, "swaps" (i.e., when the relative location of two items is reversed). However, the necessity of the hippocampus for other types of spatial-relational information involved in reconstruction behaviors (e.g., where in the environment and relative to which other items an item was located) have not yet been investigated systematically. In this work, three patients with hippocampal damage and nine healthy matched comparison participants performed an SR task. An analysis framework was developed to independently assess three first-order types of relations: (1) memory for the binding of specific item identities to locations, (2) memory for arrangement of items in relation to each other or the environment bounds, regardless of memory for the item identity, and (3) higher-order, compound relational errors (i.e., errors involving multiple pieces of relational information). Reconstruction errors were evaluated to determine the degree to which patients and comparisons differed (or not) on each type of spatial-relational information. Data revealed that the primary group difference in performance was for identity-location information. However, when the locations of items were evaluated without regarding the identities, no group difference was found in the number of item placements to studied locations. The present work provides a principled approach to analysis of SR data and clarifies our understanding of

  3. Decreasing relative risk premium

    DEFF Research Database (Denmark)

    Hansen, Frank

    2007-01-01

    such that the corresponding relative risk premium is a decreasing function of present wealth, and we determine the set of associated utility functions. We find a new characterization of risk vulnerability and determine a large set of utility functions, closed under summation and composition, which are both risk vulnerable...... and have decreasing relative risk premium. We finally introduce the notion of partial risk neutral preferences on binary lotteries and show that partial risk neutrality is equivalent to preferences with decreasing relative risk premium...

  4. Relative Monads Formalised

    Directory of Open Access Journals (Sweden)

    Thorsten Altenkirch

    2014-07-01

    Full Text Available Relative monads are a generalisation of ordinary monads where the underlying functor need not be an endofunctor. In this paper, we describe a formalisation of the basic theory of relative monads in the interactive theorem prover and dependently typed programming language Agda. The formalisation comprises the requisite basic category theory, the central concepts of the theory of relative monads and adjunctions, which are compared to their ordinary counterparts, and two running examples from programming theory.

  5. Characteristic uncertainty relations

    Energy Technology Data Exchange (ETDEWEB)

    Trifonov, D.A.; Donev, S.G. [Institute for Nuclear Research and Nuclear Energetics, Sofia (Bulgaria)

    1998-10-02

    New uncertainty relations for n observables are established. The relations take the invariant form of inequalities between the characteristic coefficients of order r, r=1, 2,...,n, of the uncertainty matrix and the matrix of mean commutators of the observables. It is shown that the second- and third-order characteristic inequalities for the three generators of SU(1, 1) and SU(2) are minimized in the corresponding group-related coherent states with maximal symmetry. (author)

  6. Motion and relativity

    CERN Document Server

    Infeld, Leopold

    1960-01-01

    Motion and Relativity focuses on the methodologies, solutions, and approaches involved in the study of motion and relativity, including the general relativity theory, gravitation, and approximation.The publication first offers information on notation and gravitational interaction and the general theory of motion. Discussions focus on the notation of the general relativity theory, field values on the world-lines, general statement of the physical problem, Newton's theory of gravitation, and forms for the equation of motion of the second kind. The text then takes a look at the approximation meth

  7. Relative Lyapunov Center Bifurcations

    DEFF Research Database (Denmark)

    Wulff, Claudia; Schilder, Frank

    2014-01-01

    Relative equilibria (REs) and relative periodic orbits (RPOs) are ubiquitous in symmetric Hamiltonian systems and occur, for example, in celestial mechanics, molecular dynamics, and rigid body motion. REs are equilibria, and RPOs are periodic orbits of the symmetry reduced system. Relative Lyapunov...... center bifurcations are bifurcations of RPOs from REs corresponding to Lyapunov center bifurcations of the symmetry reduced dynamics. In this paper we first prove a relative Lyapunov center theorem by combining recent results on the persistence of RPOs in Hamiltonian systems with a symmetric Lyapunov...

  8. Gaining Relational Competitive Advantages

    DEFF Research Database (Denmark)

    Hu, Yimei; Zhang, Si; Li, Jizhen

    2015-01-01

    Establishing strategic technological partnerships (STPs) with foreign partners is an increasingly studied topic within the innovation management literature. Partnering firms can jointly create sources of relational competitive advantage. Chinese firms often lack research and development (R......&D) capabilities but are increasingly becoming preferred technological partners for transnational corporations. We investigate an STP between a Scandinavian and a Chinese firm and try to explore how to gain relational competitive advantage by focusing on its two essential stages: relational rent generation...... and appropriation. Based on an explorative case study, we develop a conceptual framework that consists of process, organizational alliance factors, and coordination modes that we propose lead to relational competitive advantage....

  9. Models as Relational Categories

    Science.gov (United States)

    Kokkonen, Tommi

    2017-10-01

    Model-based learning (MBL) has an established position within science education. It has been found to enhance conceptual understanding and provide a way for engaging students in authentic scientific activity. Despite ample research, few studies have examined the cognitive processes regarding learning scientific concepts within MBL. On the other hand, recent research within cognitive science has examined the learning of so-called relational categories. Relational categories are categories whose membership is determined on the basis of the common relational structure. In this theoretical paper, I argue that viewing models as relational categories provides a well-motivated cognitive basis for MBL. I discuss the different roles of models and modeling within MBL (using ready-made models, constructive modeling, and generative modeling) and discern the related cognitive aspects brought forward by the reinterpretation of models as relational categories. I will argue that relational knowledge is vital in learning novel models and in the transfer of learning. Moreover, relational knowledge underlies the coherent, hierarchical knowledge of experts. Lastly, I will examine how the format of external representations may affect the learning of models and the relevant relations. The nature of the learning mechanisms underlying students' mental representations of models is an interesting open question to be examined. Furthermore, the ways in which the expert-like knowledge develops and how to best support it is in need of more research. The discussion and conceptualization of models as relational categories allows discerning students' mental representations of models in terms of evolving relational structures in greater detail than previously done.

  10. Heat-Related Illnesses

    Science.gov (United States)

    ... this! Home » Emergency 101 Heat-Related Illnesses Dr. Glenn Mitchell , Emergency physician at Mercy Health System in Chesterfield, Missouri Heat-related illness can be caused by overexposure to the sun or any situation that involves extreme heat. Young children and the elderly are most at risk, ...

  11. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... this! Home » Emergency 101 Heat-Related Illnesses Dr. Glenn Mitchell , Emergency physician at Mercy Health System in Chesterfield, Missouri Heat-related illness can be caused by overexposure to the sun or any situation that involves extreme heat. Young children and the elderly are most at risk, ...

  12. relatives in Butajira, Ethiopia

    African Journals Online (AJOL)

    Perception of stigma in people with epilepsy and their relatives in Butajira, Ethiopia. Teshome Shibrel, Atalay Alem', Redda Tekle-Hai'manotz, Girmay Medhin3, Lars ,Jacobsson4. Abstract. Background: The occurrence of psychosocial problems related to epilepsy is well recognized and in certain situations could even be ...

  13. Relational Processing Following Stroke

    Science.gov (United States)

    Andrews, Glenda; Halford, Graeme S.; Shum, David; Maujean, Annick; Chappell, Mark; Birney, Damian

    2013-01-01

    The research examined relational processing following stroke. Stroke patients (14 with frontal, 30 with non-frontal lesions) and 41 matched controls completed four relational processing tasks: sentence comprehension, Latin square matrix completion, modified Dimensional Change Card Sorting, and n-back. Each task included items at two or three…

  14. Theory of relativity

    CERN Document Server

    Pauli, W

    1958-01-01

    This classic work offers a concise and comprehensive review of the literature on relativity as of 1921, along with the author's insightful update of later developments in relativity theory and coverage of subsequent controversies. Special attention is given to unified field theories. 1958 edition.

  15. Space, Time and Relativity

    Indian Academy of Sciences (India)

    Special Relativity is now a hundred years old, and Gen- eral Relativity is just ten years younger. Even the gen- eral literate public probably knows that these two the- ories of physics - STR and GTR - profoundly altered previous conceptions and understanding of space and time in physics. We will try to describe these ...

  16. Color Relationalism and Relativism.

    Science.gov (United States)

    Byrne, Alex; Hilbert, David R

    2017-01-01

    This paper critically examines color relationalism and color relativism, two theories of color that are allegedly supported by variation in normal human color vision. We mostly discuss color relationalism, defended at length in Jonathan Cohen's The Red and the Real, and argue that the theory has insuperable problems. Copyright © 2017 Cognitive Science Society, Inc.

  17. Quantum Fluctuation Relations

    OpenAIRE

    Facchi, Paolo; Garnero, Giancarlo; Ligabò, Marilena

    2017-01-01

    We present here a set of lecture notes on exact fluctuation relations. We prove the Jarzynski equality and the Crooks fluctuation theorem, two paradigmatic examples of classical fluctuation relations. Finally we consider their quantum versions, and analyze analogies and differences with the classical case.

  18. Destination: Alumni Relations

    Science.gov (United States)

    Scully, Maura King

    2010-01-01

    Increasingly today, with the growing and sophisticated skill set alumni professionals need to get the job done, alumni relations has become a destination career rather than a stop along the way. Modern alumni relations is "so much more than homecoming and punch-and-cookie receptions." It's marketing, volunteer management, and social networking. To…

  19. relatives in Butajira, Ethiopia

    African Journals Online (AJOL)

    Abstract. Background: The occurrence of psychosocial problems related to epilepsy is well recognized and in certain situations could even be more troublesome than the effect of the seizure disorders themselves. Objective: This study was conducted to assess the magnitude of stigma experienced by patients and relatives ...

  20. The Redshifts in Relativity

    Science.gov (United States)

    Singh, Satya Pal; Singh, Apoorva; Hareet, Prabhav

    2011-01-01

    The progress of modern cosmology took off in 1917 when A. Einstein published his paper on general theory of relativity extending his work of special theory of relativity (1905). In 1922 Alexander Friedmann constructed a mathematical model for expanding Universe that had a big bang in remote past. The experimental evidences could come in 1929 by…

  1. Forces in General Relativity

    Science.gov (United States)

    Ridgely, Charles T.

    2010-01-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…

  2. Reciprocal relations in electroacoustics.

    Science.gov (United States)

    Chassagne, C; Bedeaux, D

    2014-07-28

    In a colloidal suspension, one can generate sound waves by the application of an alternating electric field (Electrokinetic Sonic Amplitude, i.e., ESA). Another phenomenon is electrophoresis (Electrophoretic Mobility, i.e., EM) where a colloidal particle moves relative to the solvent in an electric field. Vice versa one can generate electric fields or electric currents by sound waves (Colloid Vibration Potential/Current, i.e., CVP/CVI). In 1988 and 1990, O'Brien [J. Fluid Mech. 190, 71-86 (1988) and O'Brien, J. Fluid Mech. 212, 81-93 (1990)] derived a reciprocal relation between the proportionality coefficients of the EM and CVI phenomena. In this paper, we will generalize his proof by constructing the relevant entropy production from which the linear force-flux relations follow. General relations are derived for electrolyte solutions, of which colloidal suspensions are a particular case. The relations between CVI, CVP, EM, and ESA are discussed. O'Brien's reciprocal relation then follows as an Onsager relation. The relation is valid for any applied electric field frequency, particle surface charge and particle concentration (even in the presence of particle-particle interactions) provided the system is isotropic.

  3. Antecedents of Relational Capital

    DEFF Research Database (Denmark)

    Nowinska, Agnieszka

    This paper merges economic geography and relational capital perspective in order to analyze the proximity-based antecedents of relational assets in brokerage. It investigates empirically the role and interplay of geographical and cognitive proximity between a broker and her buyers in a quantitative...... for buyers characteristics. Lastly, I make use the under-researched empirical field of brokers....

  4. Relational Perspectives on Leading

    DEFF Research Database (Denmark)

    Relational Perspectives on Leading discusses leadership from a relational and social constructionism perspective as practiced on an everyday basis between people. The book pursues a fast growing, practice-based approach - particularly within the Anglo-Saxon parts of the world - to organization...

  5. Relational Perspectives on Leading

    DEFF Research Database (Denmark)

    Larsen, Mette Vinther; Rasmussen, Jørgen Gulddahl

    2015-01-01

    Relational Perspectives on Leading discusses leadership from a relational and social constructionism perspective as practiced on an everyday basis between people. The book pursues a fast growing, practice-based approach - particularly within the Anglo-Saxon parts of the world - to organization...

  6. Journalism of Relation

    DEFF Research Database (Denmark)

    Blaagaard, Bolette

    of the self-other relation which is simultaneously personal and political. Secondly, the dissertation relates the phenomenological ‘race’ and gender debates to the societal and productive context of contemporary European and ‘western’ globalised and mediated culture and politics. Journalism is re...... of cosmopolitanism from universal reproductions of sameness into creative productions of singular self-other relations based on the practiced and productive journalism. This is substantiated through case study analyses. The aim is to challenge the modern, rational journalistic subject referring back to the unified...... accountability and relation from journalistic training and practices whereby a ‘white’ and homogeneous social imaginary is reproduced. I make a call for thinking about journalism as relation – in terms of technological mediations, but also in terms of subjectivities. In order to allow for this, a shift is needed...

  7. Modernization of credit relations

    Directory of Open Access Journals (Sweden)

    S.V. Volosovich

    2015-03-01

    Full Text Available Nowadays it is essential to modernize credit relations in the conditions of global economy transformations. This is due to the influence of integration processes on credit relations and transformation of the risks inherent in the credit field. The purpose of this article is to develop measures that help to improve the efficiency of interaction of credit relations’ participants. Modernization of credit relations is based on the interaction of its main and indirect subjects who belong to the subsystems of loans granting, deposits attraction and provision of related services. Its goal is to pass from extensive to intensive model of interaction between the subjects of credit relations. Components of the credit relations modernization are the following: institutional modernization, which is based on the interaction of credit relations’ subjects, and ensures the development of competition in all credit market’s segments, the creation of its corresponding infrastructure, qualitative change in the approaches of regulation and supervision; technological modernization, which involves the formation of joint products on the credit market and the formation of an integrated informational and analytical system. In the result of the credit relations’ modernization it is expected to achieve synergies between the subjects of credit relations, that will lead to changes in the business architecture of the financial market.

  8. Ether formulations of relativity

    Energy Technology Data Exchange (ETDEWEB)

    Duffy, M.C.

    1980-12-01

    Contemporary ether theories are surveyed and criticized, especially those formally identical to orthodox Relativity. The historical development of Relativity, Special and General, in terms of an ether, is briefly indicated. Classical interpretations of Generalized Relativity using ether are compared to Euclidean formulations using a background space. The history of a sub-group of theories, formulating a 'new' Relativity involving modified transforms, is outlined. According to the theory with which they agree, recent supposed detections of drift are classified and criticized. Cosmological evidence suggesting an ether is mentioned. Only ether theories formally identical to Relativity have been published in depth. They stand criticized as being contrary to the positivist spirit. The history of mechanical analogues is traced, from Hartley's representing gravitating matter as spherical standing waves, to recent suggestions that vortex-sponge might model electromagnetic, quantum, uncertainty and faster-than-light phenomena. Contemporary theories are particular physical theories, themselves 'second interpretations' of a primary mathematical model. Mechanical analogues are auxiliary, not necessary, to other theory, disclosing relationships between classical and non-classical descriptions of assemblies charging state. The ether-relativity polemic, part of a broader dispute about relativity, is founded on mistaken conceptions of the roles of mathematical and physical models, mechanical analogues; and a distored view of history, which indicates that ether theories have become relativistic. 103 references.

  9. Optical clocks and relativity.

    Science.gov (United States)

    Chou, C W; Hume, D B; Rosenband, T; Wineland, D J

    2010-09-24

    Observers in relative motion or at different gravitational potentials measure disparate clock rates. These predictions of relativity have previously been observed with atomic clocks at high velocities and with large changes in elevation. We observed time dilation from relative speeds of less than 10 meters per second by comparing two optical atomic clocks connected by a 75-meter length of optical fiber. We can now also detect time dilation due to a change in height near Earth's surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.

  10. Gravitation and relativity

    CERN Document Server

    Hoffmann, William F

    1964-01-01

    Remarks on the observational basis of general relativity ; Riemannian geometry ; gravitation as geometry ; gravitational waves ; Mach's principle and experiments on mass anisotropy ; the many faces of Mach ; the significance for the solar system of time-varying gravitation ; relativity principles and the role of coordinates in physics ; the superdense star and the critical nucleon number ; gravitation and light ; possible effects on the solar system of φ waves if they exist ; the Lyttleton-Bondi universe and charge equality ; quantization of general relativity ; Mach's principle as boundary condition for Einstein's equations.

  11. NgsRelate

    DEFF Research Database (Denmark)

    Korneliussen, Thorfinn Sand; Moltke, Ida

    2015-01-01

    be called with high certainty. RESULTS: We present a software tool, NgsRelate, for estimating pairwise relatedness from NGS data. It provides maximum likelihood estimates that are based on genotype likelihoods instead of genotypes and thereby takes the inherent uncertainty of the genotypes into account....... Using both simulated and real data, we show that NgsRelate provides markedly better estimates for low-depth NGS data than two state-of-the-art genotype-based methods. AVAILABILITY: NgsRelate is implemented in C++ and is available under the GNU license at www.pop gen.dk/software. CONTACT: ida...

  12. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Emergencies A-Z Share this! Home » Emergency 101 Heat-Related Illnesses Dr. Glenn Mitchell , Emergency physician at ... about heat cramps and heat stroke and exhaustion. Heat Cramps Symptoms include muscle spasms, usually in the ...

  13. Sport-related concussions

    Directory of Open Access Journals (Sweden)

    Jéssica Natuline Ianof

    Full Text Available ABSTRACT Traumatic brain injury (TBI is a major cause of lifelong disability and death worldwide. Sport-related traumatic brain injury is an important public health concern. The purpose of this review was to highlight the importance of sport-related concussions. Concussion refers to a transient alteration in consciousness induced by external biomechanical forces transmitted directly or indirectly to the brain. It is a common, although most likely underreported, condition. Contact sports such as American football, rugby, soccer, boxing, basketball and hockey are associated with a relatively high prevalence of concussion. Various factors may be associated with a greater risk of sport-related concussion, such as age, sex, sport played, level of sport played and equipment used. Physical complaints (headache, fatigue, dizziness, behavioral changes (depression, anxiety, irritability and cognitive impairment are very common after a concussion. The risk of premature return to activities includes the prolongation of post-concussive symptoms and increased risk of concussion recurrence.

  14. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Health System in Chesterfield, Missouri Heat-related illness can be caused by overexposure to the sun or ... the elderly are most at risk, but anyone can be affected. Here you will find information about ...

  15. What Are Related Disorders?

    Science.gov (United States)

    ... physical problems. Some examples are Loeys-Dietz syndrome, Ehlers-Danlos syndrome, and Familial Thoracic Aortic Aneurysm and Dissection. ... are related to Marfan syndrome: Loeys-Dietz Syndrome Ehlers-Danlos Syndrome Familial Thoracic Aortic Aneurysm and Dissection MASS ...

  16. Ecomium Public Relations

    Science.gov (United States)

    Moorefield, Arthur A.

    1973-01-01

    A music professor suggests that science, math, English and history departments of colleges and universities can help build public relations, thereby taking the burden off touring choral groups, orchestras, and bands. (PG)

  17. Simple relation algebras

    CERN Document Server

    Givant, Steven

    2017-01-01

    This monograph details several different methods for constructing simple relation algebras, many of which are new with this book. By drawing these seemingly different methods together, all are shown to be aspects of one general approach, for which several applications are given. These tools for constructing and analyzing relation algebras are of particular interest to mathematicians working in logic, algebraic logic, or universal algebra, but will also appeal to philosophers and theoretical computer scientists working in fields that use mathematics. The book is written with a broad audience in mind and features a careful, pedagogical approach; an appendix contains the requisite background material in relation algebras. Over 400 exercises provide ample opportunities to engage with the material, making this a monograph equally appropriate for use in a special topics course or for independent study. Readers interested in pursuing an extended background study of relation algebras will find a comprehensive treatme...

  18. EU-Mashreq Relations

    DEFF Research Database (Denmark)

    Seeberg, Peter

    2018-01-01

    This chapter presents an overview of key issues in the relations between the European Union (EU) and the countries in the Mashreq region since the launching of the European Neighbourhood Policy (ENP) in 2004. In this chapter, the Mashreq mainly refers to Egypt, Jordan, Lebanon and Syria. 1...... Initially, it should be emphasized that the following analysis of EU-Mashreq relations is influenced by the very different political, social and economic realities in the four countries. As stated in a Strategy Paper from the European Commission in 2004, this was, from the beginning, reflected in ENP-related...... foreign policy considerations: the ENP Action Plans (APs) ‘will draw on a common set of principles but will be differentiated, reflecting the existing state of relations with each country, its needs and capacities, as well as common interests’ (Commission of the European Communities 2004). In the Mashreq...

  19. Drug related critical incidents.

    Science.gov (United States)

    Khan, F A; Hoda, M Q

    2005-01-01

    Drug related incidents are a common form of reported medical errors. This paper reviews the critical incidents related to drug errors reported from the main operating theatre suite in a teaching hospital in a developing country from January 1997 to December 2002. Each report was evaluated individually by two reviewers using a structured process. During this period, 44 874 anaesthetics were administered; 768 critical incidents were reported, 165 (21%) of which were related to drug errors. Underdosage, side-effect/drug reaction and syringe swap were the most common. A total of 76% were classified as preventable; 56% due to human error and 19% due to system error. High risk incidents accounted for 10% of all drug errors and most of these were related to the use of neuromuscular blocking drugs. This analysis has been found useful in addressing some issues about priorities.

  20. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Medicine's Front Line Observation Emergency Care Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share ... Illnesses Dr. Glenn Mitchell , Emergency physician at Mercy Health System in Chesterfield, Missouri Heat-related illness can ...

  1. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... ICE” in Your Cell Phone Prepare for Disasters Communication With Your Family And Your Doctor About Your ... Dr. Glenn Mitchell , Emergency physician at Mercy Health System in Chesterfield, Missouri Heat-related illness can be ...

  2. Publicity and public relations

    Science.gov (United States)

    Fosha, Charles E.

    1990-01-01

    This paper addresses approaches to using publicity and public relations to meet the goals of the NASA Space Grant College. Methods universities and colleges can use to publicize space activities are presented.

  3. The equation of state of polymers. Part III: Relation with the compensation law.

    Science.gov (United States)

    Rault, Jacques

    2017-09-01

    The properties of amorphous polymers and of organic compounds under pressure are interpreted in the framework of the modified Van der Walls Equation of State (mVW-EOS) the Vogel-Fulcher-Tamann (VFT) law and of the compensation law. We have shown recently that polymers and organic compounds in amorphous liquid and crystalline states verify the mVW-EOS which depends on three parameters, [Formula: see text] [Formula: see text] and [Formula: see text]. In this paper we compare the characteristic pressure [Formula: see text] of the mVW-EOS to the various pressures [Formula: see text] deduced from thermodynamic and kinetic properties of polymers in the liquid and solid states. [Formula: see text] and [Formula: see text] are: a) the enthalpy and volume change at the melting and glass transitions (the glass being isotropic or oriented and annealed below [Formula: see text] at various aging conditions); b) the activation parameters of individual [Formula: see text] and cooperative [Formula: see text] motions in crystalline liquid and amorphous polymers studied by dielectric or mechanical spectroscopy; and c) the activation parameters of amorphous (solid and liquid) polymers submitted to a deformation depending on the time frequency temperature and strain rate. For a same material, whatever its state and whatever the experimental properties analyzed (dielectric and mechanical relaxation, viscosity, auto-diffusion, yielding under hydrostatic pressure), we demonstrate that [Formula: see text], ([Formula: see text] Grüneisen parameter, [Formula: see text] compressibility). In all polymers and organic compounds (and water), these pressures, weakly dependent on T and P near [Formula: see text] and [Formula: see text] at low pressure are characteristic of the H-H inter-molecular interactions. It is shown that the two empirical Lawson and Keyes relations of the compensation law can be deduced from the mVW-EOS.

  4. Managing or Relating?

    DEFF Research Database (Denmark)

    Sproedt, Henrik; Buur, Jacob

    2010-01-01

    This paper describes a case of user-driven innovation. We draw on social capital theory and the concept of complex responsive processes to examine the role of relations for the exchange and generation of knowledge across different knowledge traditions. We argue that innovation as a social phenome...... phenomenon with a high degree of uncertainty and complexity requires more relating and less managing to use conflict as a resource by turning the friction between different knowledge traditions into creative friction....

  5. The metamorphoses of relativity

    Science.gov (United States)

    Staley, Richard

    This talk will explore the ways that problems shifted and disciplinary boundaries changed around physicists' engagement with relational physics and relativistic thought, first in research dealing with physiology, psychology and geometry in the late nineteenth century and then (a better-known story) moving between physics, mathematics and geometry in the twentieth century. I hope to develop a richer approach for understanding the disciplinary and political significance of relativity, especially by considering in one framework the work of Engels, Mach, Einstein and Planck.

  6. State extended uncertainty relations

    Energy Technology Data Exchange (ETDEWEB)

    Trifonov, D.A. [Institute for Nuclear Research, Sofia (Bulgaria)

    2000-08-18

    A scheme for construction of uncertainty relations for n observables and m states is presented. Several lowest-order inequalities are displayed and briefly discussed. For two states vertical bar {psi} > and vertical bar {phi} > and canonical observables the (entangled) extension of the Heisenberg relation reads [{delta}p({psi})]{sup 2}+[{delta}q({phi})]{sup 2}+[{delta}p({phi})]{sup 2}[{delta}q({psi})]{sup 2}= {>=}1/2. (author). Letter-to-the-editor.

  7. Algorithmic Relative Complexity

    OpenAIRE

    Daniele Cerra; Mihai Datcu

    2011-01-01

    Information content and compression are tightly related concepts that can be addressed through both classical and algorithmic information theories, on the basis of Shannon entropy and Kolmogorov complexity, respectively. The definition of several entities in Kolmogorov’s framework relies upon ideas from classical information theory, and these two approaches share many common traits. In this work, we expand the relations between these two frameworks by introducing algorithmic cross-complexity ...

  8. Why was Relativity Accepted?

    Science.gov (United States)

    Brush, S. G.

    Historians of science have published many studies of the reception of Einstein's special and general theories of relativity. Based on a review of these studies, and my own research on the role of the light-bending prediction in the reception of general relativity, I discuss the role of three kinds of reasons for accepting relativity (1) empirical predictions and explanations; (2) social-psychological factors; and (3) aesthetic-mathematical factors. According to the historical studies, acceptance was a three-stage process. First, a few leading scientists adopted the special theory for aesthetic-mathematical reasons. In the second stage, their enthusiastic advocacy persuaded other scientists to work on the theory and apply it to problems currently of interest in atomic physics. The special theory was accepted by many German physicists by 1910 and had begun to attract some interest in other countries. In the third stage, the confirmation of Einstein's light-bending prediction attracted much public attention and forced all physicists to take the general theory of relativity seriously. In addition to light-bending, the explanation of the advance of Mercury's perihelion was considered strong evidence by theoretical physicists. The American astronomers who conducted successful tests of general relativity became defenders of the theory. There is little evidence that relativity was `socially constructed' but its initial acceptance was facilitated by the prestige and resources of its advocates.

  9. INTERPERSONAL RELATIONS IN SCHOOL

    Directory of Open Access Journals (Sweden)

    Siniša Opić

    2016-12-01

    Full Text Available As part of the scientific project titled “The Curriculum of Social Competences and Relations in School”, the aim of this paper is to examine the quality of interpersonal relations between teachers and pupils. On a sample of 432 teachers from 20 towns, 35 primary schools in the Republic of Croatia, and 432 pupils, it was confirmed that there is a difference in the appraisal of the quality of their interpersonal relations. Although the overall quality of interpersonal relations between pupils and teachers is at a moderately satisfactory level, pupils still appraise the quality of interpersonal relations lower than their teachers. In view of latent dimensionality, a factor questionnaire structure was used (14 variables; ordinal type and two main components (subscales determined: didactic support and interaction, and rough verbal and physical treatment. As part of the differential draft of our research, no gender differences were established (between female and male teachers in the appraisal of the quality of interpersonal relations with pupils (on two subscales. The correlation analysis confirmed a low negative statistically significant correlation between the years of service and the subscale rough verbal and physical treatment (Rho=-0.101. In view of the subscale of rough verbal and physical treatment between pupils and teachers, such results on a negative correlation imply that older teachers, as opposed to their younger colleagues, use more corporal punishment in schools, treat pupils rudely, use nasty and impolite words, and call pupils insulting names.

  10. De Sitter projective relativity

    CERN Document Server

    Licata, Ignazio; Benedetto, Elmo

    2017-01-01

    This book presents the Projective approach to de Sitter Relativity. It traces the development of renewed interest in models of the universe at constant positive curvature such as "vacuum" geometry. The De Sitter Theory of Relativity, formulated in 1917 with Willem De Sitter's solution of the Einstein equations, was used in different fields during the 1950s and 1960s, in the work of H. Bacry, J.M. LevyLeblond and F.Gursey, to name some important contributors. From the 1960s to 1980s, L. Fantappié and G. Arcidiacono provided an elegant group approach to the De Sitter universe putting the basis for special and general projective relativity. Today such suggestions flow into a unitary scenario, and this way the De Sitter Relativity is no more a "missing opportunity" (F. Dyson, 1972), but has a central role in theoretical physics. In this volume a systematic presentation is given of the De Sitter Projective relativity, with the recent developments in projective general relativity and quantum cosmology.

  11. Frontiers in Numerical Relativity

    Science.gov (United States)

    Evans, Charles R.; Finn, Lee S.; Hobill, David W.

    2011-06-01

    Preface; Participants; Introduction; 1. Supercomputing and numerical relativity: a look at the past, present and future David W. Hobill and Larry L. Smarr; 2. Computational relativity in two and three dimensions Stuart L. Shapiro and Saul A. Teukolsky; 3. Slowly moving maximally charged black holes Robert C. Ferrell and Douglas M. Eardley; 4. Kepler's third law in general relativity Steven Detweiler; 5. Black hole spacetimes: testing numerical relativity David H. Bernstein, David W. Hobill and Larry L. Smarr; 6. Three dimensional initial data of numerical relativity Ken-ichi Oohara and Takashi Nakamura; 7. Initial data for collisions of black holes and other gravitational miscellany James W. York, Jr.; 8. Analytic-numerical matching for gravitational waveform extraction Andrew M. Abrahams; 9. Supernovae, gravitational radiation and the quadrupole formula L. S. Finn; 10. Gravitational radiation from perturbations of stellar core collapse models Edward Seidel and Thomas Moore; 11. General relativistic implicit radiation hydrodynamics in polar sliced space-time Paul J. Schinder; 12. General relativistic radiation hydrodynamics in spherically symmetric spacetimes A. Mezzacappa and R. A. Matzner; 13. Constraint preserving transport for magnetohydrodynamics John F. Hawley and Charles R. Evans; 14. Enforcing the momentum constraints during axisymmetric spacelike simulations Charles R. Evans; 15. Experiences with an adaptive mesh refinement algorithm in numerical relativity Matthew W. Choptuik; 16. The multigrid technique Gregory B. Cook; 17. Finite element methods in numerical relativity P. J. Mann; 18. Pseudo-spectral methods applied to gravitational collapse Silvano Bonazzola and Jean-Alain Marck; 19. Methods in 3D numerical relativity Takashi Nakamura and Ken-ichi Oohara; 20. Nonaxisymmetric rotating gravitational collapse and gravitational radiation Richard F. Stark; 21. Nonaxisymmetric neutron star collisions: initial results using smooth particle hydrodynamics

  12. Amiodarone-related Pneumonitis

    Directory of Open Access Journals (Sweden)

    Sheng-Nan Chang

    2007-05-01

    Full Text Available Amiodarone-related pneumonitis is a potentially limiting factor for amiodarone usage. However, it is believed that amiodarone-related pneumonitis is unlikely to occur during low-dose and short courses of therapy. We report three patients who received low-dose amiodarone, 200 mg/day, for an average of 6.6 months and who developed amiodarone-related pneumonitis. All patients were male with age of 75, 93 and 85, respectively, and had the habit of cigarette smoking. The initial presentation was dyspnea without symptoms and signs of heart failure. Their chest radiographs showed diffuse interstitial pneumonitis pattern and chest computed tomography scan also confirmed interstitial pneumonitis. Treatment included cessation of amiodarone and corticosteroid usage. All patients improved symptomatically by early detection and early treatment. This case report implies that old age and possible pre-existing pulmonary abnormalities caused by smoking could be associated with amiodarone-related pulmonary toxicity. Clinicians must remain alert to detect amiodarone-related pneumonitis even under low dosage and short duration of amiodarone usage. Immediate withdrawal of amiodarone and prompt steroid therapy will ensure full recovery.

  13. Relationality and social interaction.

    Science.gov (United States)

    Bottero, Wendy

    2009-06-01

    This paper explores Bourdieu's account of a relational social space, and his relative neglect of social interaction within this framework. Bourdieu includes social capital as one of the key relational elements of his social space, but says much less about it than economic or cultural capital, and levels of social capital are rarely measured in his work. Bourdieu is reluctant to focus on the content of social networks as part of his rejection of substantialist thinking. The neglect of substantive networks creates problems for Bourdieu's framework, because many of Bourdieu's core concepts rest upon assumptions about their interactional properties (in particular, the prevalence of homophilous differential association) which are left unexamined. It is argued here that Bourdieu's neglect of the substance of social networks is related to the criticisms that Bourdieu's framework often encounters, and that this neglect bears re-examination, since it is helpful to think of the ways in which differentiated social networks contribute to the development of habitus, help form fields, and so constitute the intersubjective social relations within which sociality, and practice more generally, occur.

  14. Algorithmic Relative Complexity

    Directory of Open Access Journals (Sweden)

    Daniele Cerra

    2011-04-01

    Full Text Available Information content and compression are tightly related concepts that can be addressed through both classical and algorithmic information theories, on the basis of Shannon entropy and Kolmogorov complexity, respectively. The definition of several entities in Kolmogorov’s framework relies upon ideas from classical information theory, and these two approaches share many common traits. In this work, we expand the relations between these two frameworks by introducing algorithmic cross-complexity and relative complexity, counterparts of the cross-entropy and relative entropy (or Kullback-Leibler divergence found in Shannon’s framework. We define the cross-complexity of an object x with respect to another object y as the amount of computational resources needed to specify x in terms of y, and the complexity of x related to y as the compression power which is lost when adopting such a description for x, compared to the shortest representation of x. Properties of analogous quantities in classical information theory hold for these new concepts. As these notions are incomputable, a suitable approximation based upon data compression is derived to enable the application to real data, yielding a divergence measure applicable to any pair of strings. Example applications are outlined, involving authorship attribution and satellite image classification, as well as a comparison to similar established techniques.

  15. Metabolism and composition of the canine anterior cruciate ligament relate to differences in knee joint mechanics and predisposition to ligament rupture.

    Science.gov (United States)

    Comerford, Eithne J; Tarlton, John F; Innes, John F; Johnson, Kenneth A; Amis, Andrew A; Bailey, Allen J

    2005-01-01

    The objective of this study was to determine whether differences in the composition and metabolism of the extracellular matrix (ECM) in canine anterior cruciate ligaments (ACLs) might relate to mechanical properties of the canine knee. Variations in ACL biochemistry and knee mechanics could account for divergent predispositions to ligament rupture. Eleven knee joints were obtained from both cadaveric Labrador Retrievers (rupture predisposed) and ex-racing Greyhounds (non-rupture predisposed). Anterioposterior laxity and tensile testing determined mechanical properties of the knee joints and ACL samples respectively. The thermal properties of the collagenous matrix were determined by differential scanning calorimetry (DSC) and the biochemical properties by measuring collagen content, collagen cross-links, glycosaminoglycan (GAG) levels, matrix metalloproteinase-2 (MMP-2), tissue inhibitors of metalloproteinase (TIMP). The anterioposterior laxity was significantly greater (p = 0.04) in the Labrador Retriever knee joints, and their ACLs tended to be weaker (p = 0.06). Greater collagen turnover was demonstrated by significantly higher (p = 0.02) concentrations of pro-MMP-2, and lower enthalpy of denaturation (p = 0.05) in Labrador Retriever ACLs. The different metabolism of the collagenous matrix in the ACLs of dogs predisposed to rupture was related to greater knee joint laxity and lower ligament material properties (ultimate tensile stress). This may be suggestive of a link between ligament rupture and eventual knee osteoarthritis in both dogs and humans.

  16. Effects of alkyl alcohols and related chemicals on rat liver structure and function. III. Physiochemical properties of ethanol-, propanol- and butanol- treated rat liver mitochondrial membranes.

    Science.gov (United States)

    Adachi, K; Momota, M; Teranishi, Y; Ueki, R; Hagiwara, M; Wakabayashi, T; Popinigis, J

    1992-08-01

    The physicochemical properties of mitochondria in liver tissue obtained from rats given 32% ethanol, 32% propanol or 6.9% butanol in drinking water for up to 3 months were investigated using differential scanning calorimetry and fluorescence polarization measurements. The results obtained were as follows: 1) Phospholipids extracted from mitochondria showed increases in the relative amounts of phosphatidylcholine, phosphatidylinositol and phosphatidylserine, and a decrease in the relative amount of phosphatidylethanolamine. An increase in the unsaturated/saturated fatty acid ratio of phospholipids was also observed. 2) Elevation of the thermotropic lipid phase transition temperature with a decrease in the enthalpy value (delta H) was revealed by differential scanning calorimetry. 3) The elevation of the lipid phase transition temperature was detected also by fluorescence polarization measurements using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. Elevation of mitochondrial membrane fluidity was found in some of the experimental animals, but most showed no changes in comparison with the control. A possible role of membrane fusion in the mechanism of formation of ethanol-, propanol- and butanol-induced hepatic megamitochondria is discussed on the basis of these results.

  17. Dynamics and Relativity

    CERN Document Server

    Forshaw, Jeffrey

    2009-01-01

    A new title in the Manchester Physics Series, this introductory text emphasises physical principles behind classical mechanics and relativity. It assumes little in the way of prior knowledge, introducing relevant mathematics and carefully developing it within a physics context. Designed to provide a logical development of the subject, the book is divided into four sections, introductory material on dynamics, and special relativity, which is then followed by more advanced coverage of dynamics and special relativity. Each chapter includes problems ranging in difficulty from simple to challenging with?solutions for solving problems. Includes?solutions for solving problemsNumerous worked examples included throughout the bookMathematics is carefully explained and developed within a physics environmentSensitive to topics that can appear daunting or confusing

  18. Tensors, relativity, and cosmology

    CERN Document Server

    Dalarsson, Mirjana

    2015-01-01

    Tensors, Relativity, and Cosmology, Second Edition, combines relativity, astrophysics, and cosmology in a single volume, providing a simplified introduction to each subject that is followed by detailed mathematical derivations. The book includes a section on general relativity that gives the case for a curved space-time, presents the mathematical background (tensor calculus, Riemannian geometry), discusses the Einstein equation and its solutions (including black holes and Penrose processes), and considers the energy-momentum tensor for various solutions. In addition, a section on relativistic astrophysics discusses stellar contraction and collapse, neutron stars and their equations of state, black holes, and accretion onto collapsed objects, with a final section on cosmology discussing cosmological models, observational tests, and scenarios for the early universe. This fully revised and updated second edition includes new material on relativistic effects, such as the behavior of clocks and measuring rods in m...

  19. Rotating Stars in Relativity

    Directory of Open Access Journals (Sweden)

    Stergioulas Nikolaos

    2003-01-01

    Full Text Available Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on the equilibrium properties and on the nonaxisymmetric instabilities in f-modes and r-modes have been updated and several new sections have been added on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity.

  20. Essential dynamics and relativity

    CERN Document Server

    O'Donnell, Peter J

    2014-01-01

    Essential Dynamics & Relativity provides students with an introduction to the core aspects of dynamics and special relativity. The author reiterates important ideas and terms throughout and covers concepts that are often missing from other textbooks at this level. He also places each topic within the wider constructs of the theory, without jumping from topic to topic to illustrate a point.The first section of the book focuses on dynamics, discussing the basic aspects of single particle motion and analyzing the motion of multi-particle systems. The book also explains the dynamical behavior of b

  1. Relativity and its roots

    CERN Document Server

    Hoffmann, Banesh

    1998-01-01

    In this fascinating, accessible introduction to one of the most revolutionary developments in modern physics, Einstein scholar Banesh Hoffmann recounts the successive insights that led to both the special and general theories of relativity.Using simple examples from everyday life, the author presents entertaining, nontechnical demonstrations of what relativity actually means and how it has revolutionized our ideas of time and space. Starting with the geometrical and cosmological ideas of the ancient Greeks, the author traces the succession of ideas and advances that paved the way for modern p

  2. On Allometry Relations

    Science.gov (United States)

    2012-07-06

    ed.) The Notebooks of Leonardo da Vinci , Vol. 1 (Dover, New York, 1970); unabridged edition of the work first published in London in 1883. 178. R...connect the “law” with a larger body of theory and/or data. An example drawn from the Notebooks of Leonardo da Vinci177 relates the diameter of a parent...limb d0 to two daughter limbs d1 and d2 : dα0 = d α 1 + d α 2 . (9) The da Vinci scaling relation supplies the phenomenological mechanism necessary

  3. Bourdieu in International Relations

    DEFF Research Database (Denmark)

    The last few years have seen a genuine wave of publications promoting sociology in international relations. Scholars have suggested that Bourdieu’s vocabulary can be applied to study security, diplomacy, migration and global environmental politics. Yet we still lack a systematic and accessible....... The chapters demonstrate how these concepts can be reinterpreted and used in new ways when exposed to Bourdieusian logic. Challenging key pillars of IR scholarship, Bourdieu in International Relations will be of interest to critical theorists, and scholars of IR theory....

  4. Annoying Danish Relatives

    DEFF Research Database (Denmark)

    Jensen de López, Kristine M.; Sundahl Olsen, Lone; Chondrigianni, V.

    2014-01-01

    This study examines the comprehension and production of subject and object relative clauses (SRCs, ORCs) by children with Specific Language Impairment (SLI) and their typically developing (TD) peers. The purpose is to investigate whether relative clauses are problematic for Danish children with SLI...... task, as well as on SRCs compared to ORCs and produced various avoidance strategies. In the ORC context, children with SLI produced more reversal errors than the AM children, who opted for passive ORCs. These results are discussed within current theories of SLI and indicate a deficiency...

  5. Structural Logical Relations

    DEFF Research Database (Denmark)

    Schürmann, Carsten; Sarnat, Jeffrey

    2008-01-01

    Tait's method (a.k.a. proof by logical relations) is a powerful proof technique frequently used for showing foundational properties of languages based on typed lambda-calculi. Historically, these proofs have been extremely difficult to formalize in proof assistants with weak meta-logics, such as ......Tait's method (a.k.a. proof by logical relations) is a powerful proof technique frequently used for showing foundational properties of languages based on typed lambda-calculi. Historically, these proofs have been extremely difficult to formalize in proof assistants with weak meta...

  6. Work-related asthma

    African Journals Online (AJOL)

    grain dust, welding fumes and wood dust. (Table III).1 Exposure to animal epithelia, hairs and secretions is commonly reported among laboratory animal workers and agricultural workers. Latex allergy-related asthma appears to be less common due to the introduction of latex-free gloves in most health care settings.

  7. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Vomiting and Diarrhea Stroke Your Blood Pressure ...

  8. Can Relations be Designed?

    DEFF Research Database (Denmark)

    Skou, Niels Peter; Mikkelsen, Mette

    2014-01-01

    This paper examines the role of design methods in a social innovation project on a Danish Institution for severely physically and mentally handicapped people. The project was focused on ‘designing’ new or better relations between the residents at the institution and the civil society. During the ...

  9. On conformally related -waves

    Indian Academy of Sciences (India)

    Conformal transformations; conformal Killing vectors; -waves. Abstract. Brinkmann [1] has shown that conformally related distinct Ricci flat solutions are -waves. Brinkmann's result has been generalized to include the conformally invariant source terms. It has been shown that [4] if g i k and g ¯ i k ( = − 2 g i k , : a ...

  10. Relationality and Mathematical Knowing

    Science.gov (United States)

    Maheux, Jean-Francois; Roth, Wolff-Michael

    2011-01-01

    Current conceptualizations of knowing and learning tend to separate the knower from others, the world they know, and themselves. In this article, we offer "relationality" as an alternative to such conceptualizations of mathematical knowing. We begin with the perspective of Maturana and Varela to articulate some of its problems and our alternative.…

  11. Om evalueringsforskningens relative autonomi

    DEFF Research Database (Denmark)

    Nørholm, Morten

    2008-01-01

    Det empiriske udgangspunkt for artiklen "Om evalueringsforskningens relative autonomi - dansk normal evalueringsforskning som et ikke-autonomt (sub)felt i magtens felt" er en række tekster af fire dominerende danske evalueringsforskere. Det teoretiske udgangspunkt er især Pierre Bourdieus teori om...

  12. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Puncture Wounds Snake Bites Teeth (Dental Emergencies) ...

  13. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Bites and Stings Listen to your Symptoms - ...

  14. A Concurrent Logical Relation

    DEFF Research Database (Denmark)

    Birkedal, Lars; Sieczkowski, Filip; Thamsborg, Jacob Junker

    2012-01-01

    We present a logical relation for showing the correctness of program transformations based on a new type-and-effect system for a concurrent extension of an ML-like language with higher-order functions, higher-order store and dynamic memory allocation. We show how to use our model to verify a number...

  15. Related Addictive Disorders.

    Science.gov (United States)

    Buck, Tina; Sales, Amos

    This paper provides an overview of addiction related to substance abuse. It provides basic information, prevalence, diagnostic criteria, assessment tools, and treatment issues for eating disorders, compulsive gambling, sex addictions, and work addictions. Eating disorders such as anorexia nervosa and bulimia nervosa, especially affect adolescents.…

  16. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Sore Throat Suicide Your Blood Pressure Score ...

  17. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Your Blood Pressure Score is as Important ...

  18. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Shock Sore Throat Suicide Resources Home Safety ...

  19. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Puncture Wounds Teeth (Dental Emergencies) Sore Throat ...

  20. Lessons in Human Relations.

    Science.gov (United States)

    Glenn, Joanne Lozar

    2003-01-01

    Explores the importance of relationship literacy--the ability to create good relationships with others--in the next economy and offers perspectives on how business education instructors can help students develop and improve their human relations skills for business success. (Author/JOW)

  1. Relational aspects of clusters

    DEFF Research Database (Denmark)

    Gjerding, Allan Næs

    The present paper is the first preliminary account of a project being planned for 2013, focussing on the development of the biomedico cluster in North Denmark. The project focusses on the relational capabilities of the cluster in terms of a number of organizational roles which are argued...... to be necessary for the development and growth of the upcoming cluster in question....

  2. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Sore Throat Chest Pain Is ALWAYS A ...

  3. Sports-related concussions.

    Science.gov (United States)

    Conder, Robert L; Conder, Alanna A

    2015-04-01

    Concussions are an inherent part of collision sports such as football and soccer. As a subset of traumatic brain injury, concussions are neurometabolic events that cause transient neurologic dysfunction. Following a concussion, some athletes require longer neurologic recovery than others. Education and intervention aimed at prevention and management can minimize the long-term sequelae of sports-related concussions.

  4. Challenging Scandinavian employment relations

    DEFF Research Database (Denmark)

    Ibsen, Christian Lyhne; Larsen, Trine Pernille; Madsen, Jørgen Steen

    2011-01-01

    and employment relations in the Danish, Norwegian and Swedish public sector. In this paper, we argue that although differences exist across the Scandinavian countries, it is evident that they have managed to adopt and implement NPM-inspired reforms without dismantling their universal welfare services and strong...

  5. Employment Relations in Denmark

    DEFF Research Database (Denmark)

    Madsen, Jørgen Steen; Due, Jesper Jørgen; Andersen, Søren Kaj

    2011-01-01

    Jørgen Steen Madsen, Jesper Due og Søren Kaj Andersen har skrevet et kapitel om udviklingen i dansk arbejdsmarkedsregulering til bogen International and Comparative Employment Relations, redigeret af Greg Bamber, Russell Lansbury og Nick Wailes. Bogen indeholder bidrag, der præsenterer og...

  6. Status of numerical relativity

    Indian Academy of Sciences (India)

    Numerical relativity; gravitational waves; black hole; neutron star. ... and stellar collapse, emphasizing the well-developed current status of such implementations that enable simulations for several astrophysical phenomena. Some of our latest results for simulation of binary neutron star mergers are briefly presented.

  7. Heat-Related Illnesses

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  8. Status of numerical relativity

    Indian Academy of Sciences (India)

    schemes are described in [48]. 2.5 Black hole finder. In many simulations of numerical relativity, black holes are formed or exist from the beginning of simulation (e.g., in merger of binary black holes). To confirm the existence of black holes and to find their location, apparent horizon finder and/or event horizon finder have to ...

  9. Work-related stress

    NARCIS (Netherlands)

    Houtman, I.L.D.

    2005-01-01

    Changes in the content and organisation of work in recent decades have resulted in an intensification of work, which is commonly regarded as a cause of stress. This report presents trends in the risks and consequences of work-related stress, and identifies how these can be prevented. The focus

  10. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Seizures Vomiting and Diarrhea Sunburn and Sun ...

  11. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Vomiting and Diarrhea Shock Sprains and Strains ...

  12. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Choking (Heimlich Maneuver) Snake Bites Sore Throat ...

  13. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Dr. Glenn Mitchell , Emergency physician at Mercy Health System in Chesterfield, Missouri Heat-related illness can be caused by overexposure to the sun or any situation that involves extreme heat. Young children and the elderly are most at risk, but anyone can be affected. ...

  14. Is Happinness relative?

    NARCIS (Netherlands)

    R. Veenhoven (Ruut)

    1991-01-01

    textabstractABSTRACT The theory that happiness is relative is based on three postulates: (1) happiness results from comparison. (2) standards of comparison adjust, (3) standards of comparison are arbitrary constructs. On the basis of these postulates the theory predicts: (a) happiness does not

  15. Effective relational dynamics

    NARCIS (Netherlands)

    Höhn, P.A.

    2011-01-01

    We provide a synopsis of an effective approach to the problem of time in the semiclassical regime. The essential features of this new approach to evaluating relational quantum dynamics in constrained systems are illustrated by means of a simple toy model.

  16. Related Drupal Nodes Block

    NARCIS (Netherlands)

    Van der Vegt, Wim

    2010-01-01

    Related Drupal Nodes Block This module exposes a block that uses Latent Semantic Analysis (Lsa) internally to suggest three nodes that are relevant to the node a user is viewing. This module performs three tasks. 1) It periodically indexes a Drupal site and generates a Lsa Term Document Matrix.

  17. Sport-Related Concussions

    Science.gov (United States)

    Brady, Don; Brady, Flo

    2011-01-01

    Sport-related concussions (SRC) are not limited to specific age ranges, professional athletes, or gender. The primary focus of much of SRC research pertains to the assessment, management, and return to play (RTP) of the concussed athlete. This article highlights some major issues of SRC along with some controversies that presently exist within the…

  18. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Chest Pain Is ALWAYS A Reason To ...

  19. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Sore Throat Suicide Puncture Wounds Resources Home ...

  20. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Sprains and Strains Sunburn and Sun Safety ...

  1. Heat-Related Illnesses

    Medline Plus

    Full Text Available ... Fact Sheet Health & Safety Tips Campaigns SUBSCRIBE Emergencies A-Z Share this! Home » Emergency 101 Heat-Related ... if the person becomes unconscious. READ IN EMERGENCIES A-Z Mental Health Emergencies - Waits for Care Grow ...

  2. Relational time in physics

    Energy Technology Data Exchange (ETDEWEB)

    Assis, A.K.T. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

    2011-07-01

    Full text: Isaac Newton (1642-1727) defended in his book Mathematical Principles of Natural Philosophy, also know as Principia, published in 1687, the utilization of absolute time in physics. According to him 'absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external'. Leibniz (1646-1716), on the other hand, was against this concept and proposed relative time to replace it: 'As for my opinion, I have said more than once, that I hold space to be something merely relative, as time is; that I hold it to be an order of coexistence, as time is an order of successions'. Leibniz ideas were accepted and developed by Ernst Mach (1838-1916) in his book The Science of Mechanics, published in 1883. In this work we consider the implementation of relational time, as proposed by Leibniz and Mach, and the consequences this implementation will mean for physics as a whole. We consider some specific examples related to mechanics (Newton's bucket experiment, the flattening of the Earth, Foucault's pendulum experiment) and to electromagnetism (Ampere's force between current carrying wires, an electric charge describing a Larmor radius due to a nearby large magnet, two charges orbiting around one another). We generalize these ideas considering the principle of physical proportions (PPP), according to which no absolute magnitudes should appear in the laws of physics. We present some laws satisfying this principle and others which do not comply with it. The laws which do not satisfy the PPP should be based upon incomplete theories. We present the consequences of complete theories complying with this fundamental principle of nature. (author)

  3. THE RELATION APICULTURE - TOURISM

    Directory of Open Access Journals (Sweden)

    Goryana Yonkova

    2016-06-01

    Full Text Available The paper presents analyses of the current condition, trends and opportunities for the apiculture development and its relation to tourism in Bulgaria. Beekeeping is considered as a branch of agriculture since its formation after the liberation to the present day and in its dynamics of development for the last 5 years. Resource base including traditions, state, production and marketing of honey is presented. Data from the National Statistics Institute, Ministry of Agriculture, Food beekeepers' associations, processors and traders of honey and bee products, the Ministry of Tourism and tourism industry organizations is analyzed and discussed. Beekeeping is represented in the relation as a resource for development of apitourism, as untraditional attractive specialized type of tourism, which can support farmers through non-agricultural practices. The paper aimed at assisting companies and individuals in the field of agribusiness and apitourism for the realization of bee products and services.

  4. Numerical relativity beyond astrophysics

    Science.gov (United States)

    Garfinkle, David

    2017-01-01

    Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology. (ii) investigations of critical behavior at the threshold of black hole formation in gravitational collapse. (iii) investigations inspired by string theory, in particular analogs of black holes in more than 4 spacetime dimensions and gravitational collapse in spacetimes with a negative cosmological constant.

  5. Surviving relatives after suicide

    DEFF Research Database (Denmark)

    Nørrelykke, Helle; Cohrt, Pernille

    suicide in Denmark. This means that at least 400 people undergo the trauma it is when one of their near relatives commits suicide. We also know that the loss from suicide involves a lot of conflicting feelings - like anger, shame, guilt and loss and that the lack of therapy/treatment of these difficult...... and conflicting feelings may result in pathological expansion of grief characterized by extremely reduced quality of life involving severe psychical and social consequences. Suicide a subject of taboo In the 1980s WHO drafted a health policy document (‘Health for all year 2000’) with 38 targets for attaining......We would like to focus on the surviving relatives after suicides, because it is generally accepted that it is especially difficult to recover after the loss from suicide and because we know as a fact that one suicide affects five persons on average. Every year approximately 700 people commit...

  6. Attachment and Related Variables

    Directory of Open Access Journals (Sweden)

    Umit Morsunbul

    2011-09-01

    Full Text Available Attachment which is defined as strong emotional bond people develop for significant others have been investigated by researchers for long years. Attachment theory proposes that attachment patterns developed in the first stages of life are carried onto next stages of life with internal working models. Additionally it is also proposed that attachment patterns are important to determine individual’s social-emotional competence. This study aims to review how attachment patterns differ according to life stages, continuity/discontiniuty of attachment patterns developed in the first stages of life and evaluate the relations between attachment patterns and social-emotional competence. The basic features of social relations model, relationship between attachment patterns and identity development, and risk taking behavior in adolescence have also been investigated in this review.

  7. LAMA2-related myopathy

    DEFF Research Database (Denmark)

    Løkken, Nicoline; Born, Alfred Peter; Duno, Morten

    2015-01-01

    INTRODUCTION: Muscular dystrophy caused by LAMA2-gene mutations is an autosomal recessive disease typically presenting as a severe, early-onset congenital muscular dystrophy (CMD). However, milder cases with a limb-girdle type muscular dystrophy (LGMD) have been described. METHODS: In this study......, we assessed the frequency and phenotypic spectrum of LAMA2-related muscular dystrophy in CMD (n = 18) and LGMD2 (n = 128) cohorts identified in the last 15 years in eastern Denmark. The medical history, brain-MRI, muscle pathology, muscle laminin-α2 expression, and genetic analyses were assessed....... RESULTS: Molecular genetics revealed 2 pathogenic LAMA2 mutations in 5 of 18 CMD and 3 of 128 LGMD patients, corresponding to a LAMA2-mutation frequency of 28% in the CMD and 2.3% in the LGMD cohorts, respectively. CONCLUSIONS: This study demonstrates a wide clinical spectrum of LAMA2-related muscular...

  8. Numerical relativity beyond astrophysics.

    Science.gov (United States)

    Garfinkle, David

    2017-01-01

    Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology. (ii) investigations of critical behavior at the threshold of black hole formation in gravitational collapse. (iii) investigations inspired by string theory, in particular analogs of black holes in more than 4 spacetime dimensions and gravitational collapse in spacetimes with a negative cosmological constant.

  9. Rotating stars in relativity.

    Science.gov (United States)

    Paschalidis, Vasileios; Stergioulas, Nikolaos

    2017-01-01

    Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on equilibrium properties and on nonaxisymmetric oscillations and instabilities in f -modes and r -modes have been updated. Several new sections have been added on equilibria in modified theories of gravity, approximate universal relationships, the one-arm spiral instability, on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity including both hydrodynamic and magnetohydrodynamic studies of these objects.

  10. International Relations in France

    DEFF Research Database (Denmark)

    Breitenbauch, Henrik Ø.

    Why is the French International Relations (IR) discipline different from the transnational-American discipline? By analysing argument structures in research articles across time, this book shows how the discipline in France is caught between the American character of the discipline and the French...... state as regulator of legitimate forms of expression. Concretely, French research arguments are less explicit about what their propositions are and what academic discussions they draw on and add to than their transnational-American counterparts. Based on a comparative case study of French and American...... IR research from 1950 to 2011, the book is a major contribution to the meta-IR literature on global, regional and national traditions of IR. The challenge to the French discipline of whether and how to position itself in relation to the evolving American discipline is in many ways exemplary for other...

  11. [Sport-related concussion].

    Science.gov (United States)

    Bonfanti, Silvia; Duthon, Victoria; Ziltener, Jean-Luc; Menetrey, Jacques

    2017-07-12

    Sport-related concussion is a frequent and complex pathology whose physiopathological mechanisms are not completely understood yet. A recent consensus statement has been published with the objective to provide practicioners with an overview of literature and give some guidelines based on the current state of knowledge. An 11R approach (Recognise, Remove, Re-evaluate, Rest, Rehabilitation, Refer, Recover, Return to sport, Reconsider, Residual effects and sequelae, Risk reduction) is proposed to evaluate and manage sport-related concussion. There is currently no available test predicting recovery, but the risk factors for a slow recovery are now known. Return to daily activities (as school) and to full sport participation should follow the graduated return-to-school or - sport strategy, and the ultimate decision is clinically based, and made by the physician.

  12. 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....

  13. Offentlighed og Public Relations

    Directory of Open Access Journals (Sweden)

    Lars Heltoft

    1993-09-01

    Full Text Available Lars Heltoft, der er en af grundlæggerne af Public Relationsuddannelsen på Roskilde Universitetscenter, kaster i artiklen et kritisk blik på den akademiske forskning i feltet public relations. Selv i nyere udgaver af PR-forskningen - af mange anset for "progressive", f.eks. James Grunings og Jon Whites arbejder - ser Lars Heltoft tydelige spor af PR- professionens selvforståelse og legitimationsbehov. Resultatet er, at den "offentlighed", der burde være kernen i den videnskabelige beskæftigelse med public relations, "forsvinder i den blå luft". Han argumenterer for, at Habermas´ forestilling om "offentlighed" stadig institutionaliserer mulig- heden for kritisk diskurs inden for feltet, samtidig med at han i sproghand- lingsteoretisk perspektiv problematiserer Habermas´ legitimationsbegreb, fordi det undtager private virksomheder og organisationer.

  14. Human Relations-skolen

    DEFF Research Database (Denmark)

    Scheuer, Steen

    2014-01-01

    Human Relations-skolen er en samlebetegnelse for to forskningsretninger, som tilsammen bidrog som nogle af de første til at indkredse og belyse de mellemmenneskelige relationers betydning for motivation og trivsel i arbejdslivet, og som skulle få stor ind"ydelse ikke bare på organisationsteorien......, men også arbejdssociologien, arbejdspsykologien og human resource development. Den første retning udsprang af de såkaldte Hawthorne-eksperimenter og psykologen Elton Mayos bearbejdelse af resultaterne derfra. Den anden er en løsere gruppering bestående af navne som Abraham Maslow og Frederick Herzberg......, som formulerede en række teorier og modeller om menneskets motivation, trivsel og behov i arbejdslivet. Selvom de ikke nødvendigvis relaterede sig til hinandens arbejde, er de forskellige bidragsydere i dag kendt som repræsentanter for den paradigmatiske betegnelse Human Relations. Undertiden skelnes...

  15. Very special relativity.

    Science.gov (United States)

    Cohen, Andrew G; Glashow, Sheldon L

    2006-07-14

    By very special relativity (VSR) we mean descriptions of nature whose space-time symmetries are certain proper subgroups of the Poincaré group. These subgroups contain space-time translations together with at least a two-parameter subgroup of the Lorentz group isomorphic to that generated by K(x) + J(y) and K(y)- J(x). We find that VSR implies special relativity (SR) in the context of local quantum field theory or of conservation. Absent both of these added hypotheses, VSR provides a simulacrum of SR for which most of the consequences of Lorentz invariance remain wholly or essentially intact, and for which many sensitive searches for departures from Lorentz invariance must fail. Several feasible experiments are discussed for which Lorentz-violating effects in VSR may be detectable.

  16. Relative value health insurance.

    Science.gov (United States)

    Korobkin, Russell

    2014-04-01

    Increases in health costs continue to outpace general inflation, and implementation of the Patient Protection and Affordable Care Act will exacerbate the problem by adding more Americans to the ranks of the insured. The most commonly proposed solutions--bureaucratic controls, greater patient cost sharing, and changes to physician incentives--all have substantial weaknesses. This article proposes a new paradigm for rationalizing health care expenditures called "relative value health insurance," a product that would enable consumers to purchase health insurance that covers cost-effective treatments but excludes cost-ineffective treatments. A combination of legal and informational impediments prevents private insurers from marketing this type of product today, but creative use of comparative effectiveness research, funded as a part of health care reform, could make relative value health insurance possible. Data deficits, adverse selection risks, and heterogeneous values among consumers create obstacles to shifting the health insurance system to this paradigm, but they could be overcome.

  17. Elements of general relativity

    Science.gov (United States)

    Agakov, Vsevolod G.; Zel'Manov, Abram L.

    The main principles of general relativity (GR) are expounded, and some of its astronomical applications are discussed. Particular emphasis is placed on mathematical methods of GR developed by Zel'manov, i.e., methods of chronometrically and kinemetrically invariant quantities, and the orthometric form of the monad formalism. The application of Zel'manov's methods to problems of relativistic cosmology are considered, and a semiinverse method for solving the Einstein gravitation equations is developed.

  18. Work related shoulder disorders

    DEFF Research Database (Denmark)

    Svendsen, Susanne Wulff; Bonde, Jens Peter; Mathiassen, S.E.

    2004-01-01

    Aims: To determine quantitative exposure-response relations between work with highly elevated arms and supraspinatus tendinitis, shoulder pain with disability, and shoulder pain without disability. Methods: A cross sectional study was conducted in a historical cohort of 1886 males from three occu...... between current work with highly elevated arms and clinically verified shoulder disorders. Substantial long term cumulative effects were not shown. A potential for primary prevention was revealed....

  19. Statin-related myotoxicity

    OpenAIRE

    Fernandes, V; Santos, MJ; Pérez, A.

    2016-01-01

    Statin therapy has a very important role in decreasing cardiovascular risk, and treatment non-compliance may therefore be a concern in high cardiovascular risk patients. Myotoxicity is a frequent side effect of statin therapy and one of the main causes of statin discontinuation, which limits effective treatment of patients at risk of or with cardiovascular disease. Because of the high proportion of patients on statin treatment and the frequency of statin-related myotoxicity, this is a subject...

  20. relation in spherical systems

    Indian Academy of Sciences (India)

    D. Bhattacharyya

    2018-02-09

    Feb 9, 2018 ... Abstract. To investigate the M• − σ relation, we consider realistic elliptical galaxy profiles that are taken to follow a single power-law density profile given by ρ(r) = ρ0(r/r0)−γ or the Nuker intensity profile. We calculate the density using Abel's formula in the latter case by employing the derived stellar potential; ...