Connecting localized DNA strand displacement reactions

Science.gov (United States)

Mullor Ruiz, Ismael; Arbona, Jean-Michel; Lad, Amitkumar; Mendoza, Oscar; Aimé, Jean-Pierre; Elezgaray, Juan

2015-07-01

Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions.Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis). As expected, constraining distances between DNA strands leads to faster reaction rates. However, it also induces side-effects that are not detectable in the solution-phase version of this circuitry. Appropriate design of the system, including protection and asymmetry between input and fuel strands, leads to a reproducible behaviour, at least one order of magnitude faster than the one observed under bulk conditions. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR02434J

Carbon-14 immobilization via the CO2-Ba(OH)2 hydrate gas-solid reaction

International Nuclear Information System (INIS)

Haag, G.L.

1980-01-01

Although no restrictions have been placed on the release of carbon-14, it has been identified as a potential health hazard due to the ease in which it may be assimilated into the biosphere. The intent of the Carbon-14 Immobilization Program, funded through the Airborne Waste Program Management Office, is to develop and demonstrate a novel process for restricting off-gas releases of carbon-14 from various nuclear facilities. The process utilizes the CO 2 -Ba(OH) 2 hydrate gas-solid reaction to directly remove and immobilize carbon-14. The reaction product, BaCO 3 , possesses both the thermal and chemical stability desired for long-term waste disposal. The process is capable of providing decontamination factors in excess of 1000 and reactant utilization of greater than 99% in the treatment of high volumetric, airlike (330 ppM CO 2 ) gas streams. For the treatment of an air-based off-gas stream, the use of packed beds of Ba(OH) 2 .8H 2 O flakes to remove CO 2 has been demonstrated. However, the operating conditions must be maintained between certain upper and lower limits with respect to the partial pressure of water. If the water vapor pressure in the gas is less than the dissociation vapor pressure of Ba(OH) 2 .8H 2 O, the bed will deactivate. If the vapor pressure is considerably greater, pressure drop problems will increase with increasing humidity as the particles curl and degrade. Results have indicated that when operated in the proper regime, the bulk of the increase in pressure drop results from the conversion of Ba(OH) 2 .8H 2 O to BaCO 3 and not from the hydration of the commercial Ba(OH) 2 .8H 2 O (i.e. Ba(OH) 2 .7.50H 2 O) to Ba(OH) 2 .8H 2 O

Set-Up and Validation of a Dynamic Solid/Gas Bioreactor

KAUST Repository

Lloyd-Randol, Jennifer D.

2012-05-01

The limited availability of fossil resourses mandates the development of new energy vectors, which is one of the Grand Challenges of the 21st Century [1]. Biocatalytic energy conversion is a promising solution to meet the increased energy demand of industrialized societies. Applications of biocatalysis in the gas-phase are so far limited to production of fine chemicals and pharmaceuticals. However, this technology has the potential for large scale biocatalytic applications [2], e.g. for the formation of novel energy carriers. The so-called solid/gas biocatalysis is defined as the application of a biocatalyst immobilized on solid-phase support acting on gaseous substrates [3]. This process combines the advantages of bio-catalysis (green chemistry, mild reaction conditions, high specicity & selectivity) and heterogeneous dynamic gas-phase processes (low diffusion limitation, high conversion, simple scale-up). This work presents the modifications of a PID Microactivity Reference reactor in order to make it suitable for solid/gas biocatalysis. The reactor design requirements are based on previously published laboratory scale solid/gas systems with a feed of saturated vapors [4]. These vapors are produced in saturation flasks, which were designed and optimized during this project. Other modifications included relocation of the gas mixing chamber, redesigning the location and heating mechanism for the reactor tube, and heating of the outlet gas line. The modified reactor system was verified based on the Candida antarctica lipase B catalyzed transesterication of ethyl acetate with 1-hexanol to hexyl acetate and ethanol and results were compared to liquid-phase model reactions. Products were analyzed on line by a gas chromatograph with a flame ionization detector. C. antarc- tica physisorbed on silica particles produced a 50% conversion of hexanol at 40 C in the gas-phase. A commercial immobilized lipase from Iris Biotech produced 99% and 97% conversions of hexanol in

Kinetics of solid-gas reactions characterized by scanning AC nano-calorimetry with application to Zr oxidation

International Nuclear Information System (INIS)

Xiao, Kechao; Lee, Dongwoo; Vlassak, Joost J.

2014-01-01

Scanning AC nano-calorimetry is a recently developed experimental technique capable of measuring the heat capacity of thin-film samples of a material over a wide range of temperatures and heating rates. Here, we describe how this technique can be used to study solid-gas phase reactions by measuring the change in heat capacity of a sample during reaction. We apply this approach to evaluate the oxidation kinetics of thin-film samples of zirconium in air. The results confirm parabolic oxidation kinetics with an activation energy of 0.59 ± 0.03 eV. The nano-calorimetry measurements were performed using a device that contains an array of micromachined nano-calorimeter sensors in an architecture designed for combinatorial studies. We demonstrate that the oxidation kinetics can be quantified using a single sample, thus enabling high-throughput mapping of the composition-dependence of the reaction rate.

Effectiveness and reaction networks of H2O2 vapor with NH3 gas for decontamination of the toxic warfare nerve agent, VX on a solid surface.

Science.gov (United States)

Gon Ryu, Sam; Wan Lee, Hae

2015-01-01

The nerve agent, O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) must be promptly eliminated following its release into the environment because it is extremely toxic, can cause death within a few minutes after exposure, acts through direct skin contact as well as inhalation, and persists in the environment for several weeks after release. A mixture of hydrogen peroxide vapor and ammonia gas was examined as a decontaminant for the removal of VX on solid surfaces at ambient temperature, and the reaction products were analyzed by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectrometry (NMR). All the VX on glass wool filter disks was found to be eliminated after 2 h of exposure to the decontaminant mixtures, and the primary decomposition product was determined to be non-toxic ethyl methylphosphonic acid (EMPA); no toxic S-[2-(diisopropylamino)ethyl] methylphosphonothioic acid (EA-2192), which is usually produced in traditional basic hydrolysis systems, was found to be formed. However, other by-products, such as toxic O-ethyl S-vinyl methylphosphonothioate and (2-diisopropylaminoethyl) vinyl disulfide, were detected up to 150 min of exposure to the decontaminant mixture; these by-products disappeared after 3 h. The two detected vinyl byproducts were identified first in this study with the decontamination system of liquid VX on solid surfaces using a mixture of hydrogen peroxide vapor and ammonia gas. The detailed decontamination reaction networks of VX on solid surfaces produced by the mixture of hydrogen peroxide vapor and ammonia gas were suggested based on the reaction products. These findings suggest that the mixture of hydrogen peroxide vapor and ammonia gas investigated in this study is an efficient decontaminant mixture for the removal of VX on solid surfaces at ambient temperature despite the formation of a toxic by-product in the reaction process.

Application of the carbon dioxide-barium hydroxide hydrate gas-solid reaction for the treatment of dilute carbon dioxide-bearing gas streams

International Nuclear Information System (INIS)

Haag, G.L.

1983-09-01

The removal of trace components from gas streams via irreversible gas-solid reactions in an area of interest to the chemical engineering profession. This research effort addresses the use of fixed beds of Ba(OH) 2 hydrate flakes for the removal of an acid gas, CO 2 , from air that contains approx. 330 ppM/sub v/ CO 2 . Areas of investigation encompassed: (1) an extensive literature review of Ba(OH) 2 hydrate chemistry, (2) microscale studies on 0.150-g samples to develop a better understanding of the reaction, (3) process studies at the macroscale level with 10.2-cm-ID fixed-bed reactors, and (4) the development of a model for predicting fixed-bed performance. Experimental studies indicated fixed beds of commercial Ba(OH) 2 .8H 2 O flakes at ambient temperatures to be capable of high CO 2 -removal efficiencies (effluent concentrations 99%), and an acceptable pressure drop (1.8 kPa/m at a superficial gas velocity of 13 cm/s). Ba(OH) 2 .8H 2 O was determined to be more reactive toward CO 2 than either Ba(OH) 2 .3H 2 O or Ba(OH) 2 .1H 2 O. A key variable in the development of this fixed-bed process was relative humidity. Operation at conditions with effluent relative humidities >60% resulted in significant recrystallization and restructuring of the flake and subsequent pressure-drop problems

Influence of additives and impurities in sweep gas and solid tritium release behaviour from lithium ceramics (review)

International Nuclear Information System (INIS)

Tanaka, Satoru

1991-01-01

Tritium release from solid breeding material is affected by small amounts of additives or impurities in the sweep gas or solid itself. Addition of hydrogen or water vapor to the sweep gas is reported to enhance the surface reaction of tritium release. Doping to solid breeder with elements of different valence from lithium has a possibility to improve tritium diffusion in the solid. Surface reaction and migration behavior in bulk are believed to be also affected by impurities in the sweep gas and in the solid. In order to model tritium release behavior in the blanket of fusion reactor, the mechanism of interaction with these additives or impurities must be quantitatively formulated. However, the mechanism of these remains to be elucidated. In this paper effects of these additives and impurities on tritium migration are reviewed. The mechanism of surface reaction for He+H 2 sweep gas is also discussed. (orig.)

Study of the obtainment of Mo{sub 2}C by gas-solid reaction in a fixed and rotary bed reactor; Estudo da obtencao de Mo{sub 2}C por reacao gas-solido em reator de leito fixo e rotativo

Energy Technology Data Exchange (ETDEWEB)

Araujo, C.P.B. de; Souza, C.P. de; Souto, M.V.M.; Barbosa, C.M.; Frota, A.V.V.M., E-mail: cpbaraujo@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

2016-07-01

Carbides' synthesis via gas-solid reaction overcomes many of the difficulties found in other processes, requiring lower temperatures and reaction times than traditional metallurgic routes, for example. In carbides' synthesis in fixed bed reactors (FB) the solid precursor is permeated by the reducing/carburizing gas stream forming a packed bed without mobility. The use of a rotary kiln reactor (RK) adds a mixing character to this process, changing its fluid-particle dynamics. In this work ammonium molybdate was subjected to carbo-reduction reaction (CH4 / H2) in both reactors under the same gas flow (15L / h) and temperature (660 ° C) for 180 minutes. Complete conversion was observed Mo2C (dp = 18.9nm modal particles sizes' distribution) in the fixed bed reactor. In the RK reactor this conversion was only partial (∼ 40%) and Mo2C and MoO3 (34nm dp = bimodal) could be observed on the produced XRD pattern. Partial conversion was attributed to the need to use higher solids loading in the reactor CR (50% higher) to avoid solids to centrifuge. (author)

Reaction diffusion and solid state chemical kinetics handbook

CERN Document Server

Dybkov, V I

2010-01-01

This monograph deals with a physico-chemical approach to the problem of the solid-state growth of chemical compound layers and reaction-diffusion in binary heterogeneous systems formed by two solids; as well as a solid with a liquid or a gas. It is explained why the number of compound layers growing at the interface between the original phases is usually much lower than the number of chemical compounds in the phase diagram of a given binary system. For example, of the eight intermetallic compounds which exist in the aluminium-zirconium binary system, only ZrAl3 was found to grow as a separate

Double Displacement: an Improved Bioorthogonal Reaction Strategy for Templated Nucleic Acid Detection

OpenAIRE

Kleinbaum, Daniel J.; Miller, Gregory P.; Kool, Eric T.

2010-01-01

Quenched autoligation probes have been employed previously in a target-templated nonenzymatic ligation strategy for detecting nucleic acids in cells by fluorescence. A common source of background signal in such probes is undesired reaction with water and other cellular nucleophiles. Here we describe a new class of self-ligating probes, double displacement (DD) probes, that rely on two displacement reactions to fully unquench a nearby fluorophore. Three potential double displacement architectu...

The reactive solid-gas flow of a fluidized bed for UO2 conversion

International Nuclear Information System (INIS)

Juanico, L.E.

1991-01-01

The reactive solid-gas flow of a fluidized bed for UO 2 conversion was modeled. The sedimentation-reaction process was treated using the drift-flux equations. Also, the associated pressure transient due to the reaction gas release was analyzed. An experiment was carried out to compare the results, and pressure transient was numerically simulated, reaching interesting conclusions. (Author) [es

Double displacement: An improved bioorthogonal reaction strategy for templated nucleic acid detection.

Science.gov (United States)

Kleinbaum, Daniel J; Miller, Gregory P; Kool, Eric T

2010-06-16

Quenched autoligation probes have been employed previously in a target-templated nonenzymatic ligation strategy for detecting nucleic acids in cells by fluorescence. A common source of background signal in such probes is the undesired reaction with water and other cellular nucleophiles. Here, we describe a new class of self-ligating probes, double displacement (DD) probes, that rely on two displacement reactions to fully unquench a nearby fluorophore. Three potential double displacement architectures, all possessing two fluorescence quencher/leaving groups (dabsylate groups), were synthesized and evaluated for templated reaction with nucleophile (phosphorothioate) probes both in vitro and in intact bacterial cells. All three DD probe designs provided substantially better initial quenching than a single-Dabsyl control. In isothermal templated reactions in vitro, double displacement probes yielded considerably lower background signal than previous single displacement probes; investigation into the mechanism revealed that one dabsylate acts as a sacrificial leaving group, reacting nonspecifically with water, but yielding little signal because another quencher group remains. Templated reaction with the specific nucleophile probe is required to activate a signal. The double displacement probes provided a ca. 80-fold turn-on signal and yielded a 2-4-fold improvement in signal/background over single Dabsyl probes. The best-performing probe architecture was demonstrated in a two-color, FRET-based two-allele discrimination system in vitro and was shown to be capable of discriminating between two closely related species of bacteria differing by a single nucleotide at an rRNA target site.

Energy-filtered environmental transmission electron microscopy for the assessment of solid-gas reactions at elevated temperature: NiO/YSZ-H₂ as a case study

DEFF Research Database (Denmark)

Jeangros, Q.; Hansen, Thomas Willum; Wagner, Jakob Birkedal

2016-01-01

A novel approach, which is based on the analysis of sequences of images recorded using energy-filtered transmission electron microscopy and can be used to assess the reaction of a solid with a gas at elevated temperature, is illustrated for the reduction of a NiO/ceramic solid oxide fuel cell ano...

Molecular dynamics study of atomic displacements in disordered solid alloys

Science.gov (United States)

Puzyrev, Yevgeniy S.

The effects of atomic displacements on the energetics of alloys plays important role in the determining the properties of alloys. We studied the atomic displacements in disordered solid alloys using molecular dynamics and Monte-Carlo methods. The diffuse scattering of pure materials, copper, gold, nickel, and palladium was calculated. The experimental data for pure Cu was obtained from diffuse scattering intensity of synchrotron x-ray radiation. The comparison showed the advantages of molecular dynamics method for calculating the atomic displacements in solid alloys. The individual nearest neighbor separations were calculated for Cu 50Au50 alloy and compared to the result of XAFS experiment. The molecular dynamics method provided theoretical predictions of nearest neighbor pair separations in other binary alloys, Cu-Pd and Cu-Al for wide range of the concentrations. We also experimentally recovered the diffuse scattering maps for the Cu47.3Au52.7 and Cu85.2Al14.8 alloy.

Synthesis and characterization of tungsten carbide doped cobalt via gas-solid reaction in rotary bed reactor; Sintese e caracterizacao de carbeto de tungstenio dopado com cobalto via reacao gas-solido em reator de leito rotativo

Energy Technology Data Exchange (ETDEWEB)

Tertuliano, R.S.C.; Araujo, C.P.B. de; Frota, A.V.V.M.; Moriyama, A.L.L.; Souza, C.P. de, E-mail: ruasavio@hotmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Departamento de Engenharia Quimica

2016-07-01

The search for materials with high added value, high applicability and sustainability, motivates innovations in all areas of engineering. In this context, so-called doped carbides, ceramic and metal compounds are included. This work proposes the synthesis and characterization of tungsten carbide doped cobalt (WC-Co) through the gas-solid reaction in a rotating bed reactor. The production stages of the material are: precursor synthesis by wetting, drying at 80 deg C, characterization of the precursor by MEV, DRX and FRX, gas-solid reaction at 750 deg C in a reducing atmosphere of CH{sub 4} / H{sub 2} in a rotary reactor at 34 rpm and characterization of the reaction product by the techniques already mentioned. The results showed that tungsten carbide powders were produced with cobalt inserted into the structure, with high surface area, nanometric grains and with potential for applications in the areas of catalysis, reactors and fuel cells, showing the relevance of this type of research.

Gas Generation from Solids in Aqueous Suspensions

International Nuclear Information System (INIS)

Meisel, D.; Schatz, T.

1999-01-01

The presence of solid particles suspended in solution may change the radiation-induced chemistry of a system in many ways. Catalytic surface effects may manifest themselves through the acceleration or inhibition of various reactions. As importantly, the yield of primary radiolysis products may be affected as the solids absorb a significant fraction of the radiation energy. The latter is the subject of this study. We explore the possibility that absorption of radiation by the solid particles may initiate chemistry in the water. This is a question of fundamental as well as practical significance. On the fundamental side we ask whether electron-hole pairs generated in the solid phase can escape and cross into the aqueous phase and initiate chemical reactions such as gas generation and how this possibility depends on the energy levels of the material and on particle size. From a practical angle, such questions are directly relevant to any heterogeneous system exposed to radiation. High-level waste temporarily stored in underground tanks, low-level waste permanently stored in humid grout, or soil particles migrating in geological formations are but a few examples

Workshop Report: Fundamental Reactions in Solid Propellant Combustion

Science.gov (United States)

1979-05-01

combustion conditions. 6. What effect might a pressure-induced phase transition to a polymorph other than 6- HMX have on the pressure slope break during...pure HMX as well. Nevertheless, it is recommended that the high pressure polymorphs of HMX and RDX be determined. It was also felt that there...plateau burning phenomena E. Solid phase, surface, gas phase reactions F. Phase transitions : melting, vaporization, polymorphs G. Flame

Gas-Solid Reaction Route toward the Production of Intermetallics from Their Corresponding Oxide Mixtures

Directory of Open Access Journals (Sweden)

Hesham Ahmed

2016-08-01

Full Text Available Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the “Reduction-Sintering” process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H2, CH4 and N2 were used for simultaneous reduction, carburization and nitridation, respectively. Different techniques have been utilized. A thermogravimetric analyzer was used to accurately control the process conditions and obtain reaction kinetics. The fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method. These efforts end up with a successful preparation of nanograined intermetallics like Fe-Mo and Ni-W. In addition, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures

A Model of Solid State Gas Sensors

Science.gov (United States)

Woestman, J. T.; Brailsford, A. D.; Shane, M.; Logothetis, E. M.

1997-03-01

Solid state gas sensors are widely used to measure the concentrations of gases such as CO, CH_4, C_3H_6, H_2, C_3H8 and O2 The applications of these sensors range from air-to-fuel ratio control in combustion processes including those in automotive engines and industrial furnaces to leakage detection of inflammable and toxic gases in domestic and industrial environments. As the need increases to accurately measure smaller and smaller concentrations, problems such as poor selectivity, stability and response time limit the use of these sensors. In an effort to overcome some of these limitations, a theoretical model of the transient behavior of solid state gas sensors has been developed. In this presentation, a model for the transient response of an electrochemical gas sensor to gas mixtures containing O2 and one reducing species, such as CO, is discussed. This model accounts for the transport of the reactive species to the sampling electrode, the catalyzed oxidation/reduction reaction of these species and the generation of the resulting electrical signal. The model will be shown to reproduce the results of published steady state models and to agree with experimental steady state and transient data.

New paradigm for simplified combustion modeling of energetic solids: Branched chain gas reaction

Energy Technology Data Exchange (ETDEWEB)

Brewster, M.Q.; Ward, M.J. [Univ. of Illinois, Urbana, IL (United States); Son, S.F. [Los Alamos National Lab., NM (United States)

1997-09-01

Two combustion models with simple but rational chemistry are compared: the classical high gas activation energy (E{sub g}/RT {much_gt} 1) Denison-Baum-Williams (DBW) model, and a new low gas activation energy (E{sub g}/RT {much_lt} 1) model recently proposed by Ward, Son, and Brewster (WSB). Both models make the same simplifying assumptions of constant properties, Lewis number unity, single-step, second order gas phase reaction, and single-step, zero order, high activation energy condensed phase decomposition. The only difference is in the gas reaction activation energy E{sub g} which is asymptotically large for DBW and vanishingly small for WSB. For realistic parameters the DBW model predicts a nearly constant temperature sensitivity {sigma}{sub p} and a pressure exponent n approaching 1. The WSB model predicts generally observed values of n = 0.7 to 0.9 and {sigma}{sub p}(T{sub o},P) with the generally observed variations with temperature (increasing) and pressure (decreasing). The WSB temperature profile also matches measured profiles better. Comparisons with experimental data are made using HMX as an illustrative example (for which WSB predictions for {sigma}{sub p}(T{sub o},P) are currently more accurate than even complex chemistry models). WSB has also shown good agreement with NC/NG double base propellant and HNF, suggesting that at the simplest level of combustion modeling, a vanishingly small gas activation energy is more realistic than an asymptotically large one. The authors conclude from this that the important (regression rate determining) gas reaction zone near the surface has more the character of chain branching than thermal decomposition.

Displacement of oil by gas in power production

International Nuclear Information System (INIS)

Sundram, S.; Seng, L.K.; Kow, P.T.A.

1992-01-01

After the oil crises, Malaysia unveiled its four fuel diversification policy in the late 1970s towards utilization of gas, oil, coal and hydro. This was to ensure adequate and continuous energy supply for driving economic development and to cushion itself against impact of possible future fluctuations in oil prices. The primary energy supply in 1978 was predominantly oil based, consisting of 75.5% oil. As a result of this diversification policy, the oil component was reduced to about 51.8% in 1988. Due to its inherent ability to adapt and adjust to different fuels, the power sector played a crucial role in this massive shift away from oil. For the corresponding period, the oil component in the electricity generation input mix has decreased from 86.7% oil to 47.4%. Malaysia is endowed with substantial natural gas reserves amounting to 52.5 trillion cubic feet. Gas, therefore constitutes a natural and attractive option for the power sector in diversifying into non-oil indigenous energy resources, as the country's hydro potential has its limitations and the available proven coal reserves are relatively small. The paper addresses the past and current status and issues involved in displacing oil by gas for the power sector. These include the economic, technological and pricing aspects of natural gas development and issues pertaining to power system development. Future gas utilization strategies include the conversion of existing oil-fired plants to gas-fired, and the plant-up of gas turbines and the efficient combined cycle plants to meet the load requirements. These strategies are assessed from the viability and security perspective of increased gas utilization. Oil will continue to be displaced, but the extent to which gas will increase its share in power production is dependent on numerous factors ranging from its economics to supply security

Internal Displacement Reactions in Multicomponent Oxides: Part I. Line Compounds with Narrow Homogeneity Range

OpenAIRE

Reddy, SNS; Leonard, DN; Wiggins, LB; Jacob, KT

2005-01-01

As a model of an internal displacement reaction involving a ternary oxide line compound, the following reaction was studied at 1273 K as a function of time, t: $Fe+NiTiO_3 = Ni + FeTiO_3$ Both polycrystalline and single-crystal materials were used as the starting $NiTiO_3$ oxide. During the reaction, the Ni in the oxide compound is displaced by Fe and it precipitates as a \\gamma -(Ni-Fe) alloy. The reaction preserves the starting ilmenite structure. The product oxide has a consta...

Direct gas-solid carbonation kinetics of steel slag and the contribution to in situ sequestration of flue gas CO(2) in steel-making plants.

Science.gov (United States)

Tian, Sicong; Jiang, Jianguo; Chen, Xuejing; Yan, Feng; Li, Kaimin

2013-12-01

Direct gas-solid carbonation of steel slag under various operational conditions was investigated to determine the sequestration of the flue gas CO2 . X-ray diffraction analysis of steel slag revealed the existence of portlandite, which provided a maximum theoretical CO2 sequestration potential of 159.4 kg CO 2 tslag (-1) as calculated by the reference intensity ratio method. The carbonation reaction occurred through a fast kinetically controlled stage with an activation energy of 21.29 kJ mol(-1) , followed by 10(3) orders of magnitude slower diffusion-controlled stage with an activation energy of 49.54 kJ mol(-1) , which could be represented by a first-order reaction kinetic equation and the Ginstling equation, respectively. Temperature, CO2 concentration, and the presence of SO2 impacted on the carbonation conversion of steel slag through their direct and definite influence on the rate constants. Temperature was the most important factor influencing the direct gas-solid carbonation of steel slag in terms of both the carbonation conversion and reaction rate. CO2 concentration had a definite influence on the carbonation rate during the kinetically controlled stage, and the presence of SO2 at typical flue gas concentrations enhanced the direct gas-solid carbonation of steel slag. Carbonation conversions between 49.5 % and 55.5 % were achieved in a typical flue gas at 600 °C, with the maximum CO2 sequestration amount generating 88.5 kg CO 2 tslag (-1) . Direct gas-solid carbonation of steel slag showed a rapid CO2 sequestration rate, high CO2 sequestration amounts, low raw-material costs, and a large potential for waste heat utilization, which is promising for in situ carbon capture and sequestration in the steel industry. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Use of the finite element displacement method to solve solid-fluid interaction vibration problems

International Nuclear Information System (INIS)

Brown, S.J.; Hsu, K.H.

1978-01-01

It is shown through comparison to experimental, theoretical, and other finite element formulations that the finite element displacement method can solve accurately and economically a certain class of solid-fluid eigenvalue problems. The problems considered are small displacements in the absence of viscous damping and are 2-D and 3-D in nature. In this study the advantages of the finite element method (in particular the displacement formulation) is apparent in that a large structure consisting of the cylinders, support flanges, fluid, and other experimental boundaries could be modeled to yield good correlation to experimental data. The ability to handle large problems with standard structural programs is the key advantage of the displacement fluid method. The greatest obstacle is the inability of the analyst to inhibit those rotational degrees of freedom that are unnecessary to his fluid-structure vibration problem. With judicious use of element formulation, boundary conditions and modeling, the displacement finite element method can be successfully used to predict solid-fluid response to vibration and seismic loading

Gas transport in solid oxide fuel cells

CERN Document Server

He, Weidong; Dickerson, James

2014-01-01

This book provides a comprehensive overview of contemporary research and emerging measurement technologies associated with gas transport in solid oxide fuel cells. Within these pages, an introduction to the concept of gas diffusion in solid oxide fuel cells is presented. This book also discusses the history and underlying fundamental mechanisms of gas diffusion in solid oxide fuel cells, general theoretical mathematical models for gas diffusion, and traditional and advanced techniques for gas diffusivity measurement.

Electron stimulated reactions of methyl iodide coadsorbed with amorphous solid water

International Nuclear Information System (INIS)

Perry, C. C.; Faradzhev, N. S.; Madey, T. E.; Fairbrother, D. H.

2007-01-01

The electron stimulated reactions of methyl iodide (MeI) adsorbed on and suspended within amorphous solid water (ice) were studied using a combination of postirradiation temperature programmed desorption and reflection absorption infrared spectroscopy. For MeI adsorbed on top of amorphous solid water (ice), electron beam irradiation is responsible for both structural and chemical transformations within the overlayer. Electron stimulated reactions of MeI result principally in the formation of methyl radicals and solvated iodide anions. The cross section for electron stimulated decomposition of MeI is comparable to the gas phase value and is only weakly dependent upon the local environment. For both adsorbed MeI and suspended MeI, reactions of methyl radicals within MeI clusters lead to the formation of ethane, ethyl iodide, and diiodomethane. In contrast, reactions between the products of methyl iodide and water dissociation are responsible for the formation of methanol and carbon dioxide. Methane, formed as a result of reactions between methyl radicals and either parent MeI molecules or hydrogen atoms, is also observed. The product distribution is found to depend on the film's initial chemical composition as well as the electron fluence. Results from this study highlight the similarities in the carbon-containing products formed when monohalomethanes coadsorbed with amorphous solid water are irradiated by either electrons or photons

Combined effects of displacement damage and high gas content in aluminum

International Nuclear Information System (INIS)

Farrell, K.; Houston, J.T.

1976-01-01

A solid solution alloy of 2300 at. ppM of 6 Li isotope in aluminum was neutron irradiated at about 0.36 T/sub m/ in high, fast and thermal fluxes producing a damage level of 2 to 3 dpa and simultaneously inducing a gas content of about 2200 at. ppM each of helium and tritium from burnup of 6 Li. The gases significantly increased the nucleation of structural defects but did not change the degree of swelling; cavity concentrations were increased approximately 1000-fold, cavity sizes were decreased approximately 10-fold and there was approximately 10-fold increase in the concentrations of dislocations. Also, large cavities were developed on grain boundaries. The cavities were consistent with their being gas-filled bubbles. The refinement of damage structure by the gases caused a considerable increase in radiation hardening. Bend tests at 77 and 296 0 K revealed severe embrittlement and intergranular fracture. Comparison with data from material irradiated to produce comparable gas levels but relatively little displacement damage indicates that premature intergranular failure is much enhanced by the presence of a defect-hardened matrix. Postirradiation annealing tests showed the cavity and dislocation structures to have high resistance to annealing. Annealing also encouraged the development of a secondary population of large cavities believed to be associated with migration and precipitation of tritium

Combined effects of displacement damage and high gas content in aluminum

International Nuclear Information System (INIS)

Farrell, K.; Houston, J.T.

1976-05-01

A solid solution alloy of 2300 appm of 6 Li isotope in aluminum was neutron irradiated at about 0.36 T/sub m/ in high, fast and thermal fluxes producing a damage level of 2 to 3 dpa and simultaneously inducing a gas content of about 2200 appm each of helium and tritium from burnup of 6 Li. The gases significantly increased the nucleation of structural defects but did not change the degree of swelling; cavity concentrations were increased approximately 1000-fold, cavity sizes were decreased approximately 10-fold and there was approximately 10-fold increase in the concentrations of dislocations. Also, large cavities were developed on grain boundaries. The cavities were consistent with their being gas-filled bubbles. The refinement of damage structure by the gases caused a considerable increase in radiation hardening. Bend tests at 77 and 296 K revealed severe embrittlement and intergranular fracture. Comparison with data from material irradiated to produce comparable gas levels but relatively little displacement damage indicates that premature intergranular failure is much enhanced by the presence of a defect-hardened matrix. Postirradiation annealing tests showed the cavity and dislocation structures to have high resistance to annealing. Annealing also encouraged the development of a secondary population of large cavities believed to be associated with migration and precipitation of tritium

Boundaries matter: Greenhouse gas emission reductions from alternative waste treatment strategies for California’s municipal solid waste

DEFF Research Database (Denmark)

Vergara, Sintana E.; Damgaard, Anders; Horvathc, Arpad

2011-01-01

How waste is managed – whether as a nuisance to be disposed of, or as a resource to be reused – directly affects local and global environmental quality. This analysis explores the GHG benefits of five treatment options for residual municipal solid waste (MSW) in California: Business As Usual...... landfills. Using two different waste LCA models, EASEWASTE (a Danish model) and WARM (a U.S. model), we find that improved biogenic waste management through anaerobic digestion and waste reduction can lead to life-cycle GHG savings when compared to Business As Usual. The magnitude of the benefits depends...... strongly on a number of model assumptions: the type of electricity displaced by waste-derived energy, how biogenic carbon is counted as a contributor to atmospheric carbon stocks, and the landfill gas collection rate. Assuming that natural gas is displaced by waste-derived energy, that 64% of landfill gas...

Theory of atom displacements induced by fast electron elastic scattering in solids

International Nuclear Information System (INIS)

Cruz, C. M.; Pinera, I.; Abreu, Y.; Leyva, A.

2006-01-01

Present contribution deals with the theoretical description of the conditions favoring the occurrence of single fast electron elastic scattering in solids, leading to the displacement of atoms from their crystalline sites. Firstly, the Moliere-Bethe-Goudsmit-Saunderson theory of Multiple Electron Scattering is applied, determining the limiting angle θ l over which the single electron elastic scattering prevails over the multiple one, leading to the evaluation of the total macroscopic cross-section for single electron elastic scattering on the basis of the Mott-Rutherford differential cross-section. On the basis of single electron elastic scattering by atoms in the solid matrix, it was determined the relative number of Atom Displacements produced by the Gamma Radiation as a primary act, as well as the energy and linear momentum of the ejected atoms. The statistical distributions of single electron elastic scattering and of those inducing Atom Displacements at different electron initial energies in comparison with the others electron inelastic scattering channels are discussed, where the statistical sampling methods on the basis of the rejection one where applied simulating different practical situations. (Full text)

Mechanism of chimera formation during the Multiple Displacement Amplification reaction

Directory of Open Access Journals (Sweden)

Stockwell Timothy B

2007-04-01

Full Text Available Abstract Background Multiple Displacement Amplification (MDA is a method used for amplifying limiting DNA sources. The high molecular weight amplified DNA is ideal for DNA library construction. While this has enabled genomic sequencing from one or a few cells of unculturable microorganisms, the process is complicated by the tendency of MDA to generate chimeric DNA rearrangements in the amplified DNA. Determining the source of the DNA rearrangements would be an important step towards reducing or eliminating them. Results Here, we characterize the major types of chimeras formed by carrying out an MDA whole genome amplification from a single E. coli cell and sequencing by the 454 Life Sciences method. Analysis of 475 chimeras revealed the predominant reaction mechanisms that create the DNA rearrangements. The highly branched DNA synthesized in MDA can assume many alternative secondary structures. DNA strands extended on an initial template can be displaced becoming available to prime on a second template creating the chimeras. Evidence supports a model in which branch migration can displace 3'-ends freeing them to prime on the new templates. More than 85% of the resulting DNA rearrangements were inverted sequences with intervening deletions that the model predicts. Intramolecular rearrangements were favored, with displaced 3'-ends reannealing to single stranded 5'-strands contained within the same branched DNA molecule. In over 70% of the chimeric junctions, the 3' termini had initiated priming at complimentary sequences of 2–21 nucleotides (nts in the new templates. Conclusion Formation of chimeras is an important limitation to the MDA method, particularly for whole genome sequencing. Identification of the mechanism for chimera formation provides new insight into the MDA reaction and suggests methods to reduce chimeras. The 454 sequencing approach used here will provide a rapid method to assess the utility of reaction modifications.

Constructing Solid-Gas-Interfacial Fenton Reaction over Alkalinized-C3N4 Photocatalyst To Achieve Apparent Quantum Yield of 49% at 420 nm.

Science.gov (United States)

Li, Yunxiang; Ouyang, Shuxin; Xu, Hua; Wang, Xin; Bi, Yingpu; Zhang, Yuanfang; Ye, Jinhua

2016-10-03

Efficient generation of active oxygen-related radicals plays an essential role in boosting advanced oxidation process. To promote photocatalytic oxidation for gaseous pollutant over g-C 3 N 4 , a solid-gas interfacial Fenton reaction is coupled into alkalinized g-C 3 N 4 -based photocatalyst to effectively convert photocatalytic generation of H 2 O 2 into oxygen-related radicals. This system includes light energy as power, alkalinized g-C 3 N 4 -based photocatalyst as an in situ and robust H 2 O 2 generator, and surface-decorated Fe 3+ as a trigger of H 2 O 2 conversion, which attains highly efficient and universal activity for photodegradation of volatile organic compounds (VOCs). Taking the photooxidation of isopropanol as model reaction, this system achieves a photoactivity of 2-3 orders of magnitude higher than that of pristine g-C 3 N 4 , which corresponds to a high apparent quantum yield of 49% at around 420 nm. In-situ electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicate that the notable photoactivity promotion could be ascribed to the collaboration between photocarriers (electrons and holes) and Fenton process to produce abundant and reactive oxygen-related radicals. The strategy of coupling solid-gas interfacial Fenton process into semiconductor-based photocatalysis provides a facile and promising solution to the remediation of air pollution via solar energy.

Chemical kinetics of gas reactions

CERN Document Server

Kondrat'Ev, V N

2013-01-01

Chemical Kinetics of Gas Reactions explores the advances in gas kinetics and thermal, photochemical, electrical discharge, and radiation chemical reactions. This book is composed of 10 chapters, and begins with the presentation of general kinetic rules for simple and complex chemical reactions. The next chapters deal with the experimental methods for evaluating chemical reaction mechanisms and some theories of elementary chemical processes. These topics are followed by discussions on certain class of chemical reactions, including unimolecular, bimolecular, and termolecular reactions. The rema

Analytical solutions for non-linear conversion of a porous solid particle in a gas : II. non-isothermal conversion and numerical verification

NARCIS (Netherlands)

Brem, G.; Brouwers, J.J.H.

1990-01-01

In Part I, analytical solutions were given for the non-linear isothermal heterogeneous conversion of a porous solid particle. Account was taken of a reaction rate of general order with respect to the gas reactant, intrinsic reaction surface area and effective pore diffusion, which change with solid

Studies in the reaction dynamics of beam-gas chemiluminescent reactions

International Nuclear Information System (INIS)

Prisant, M.G.

1984-01-01

This thesis develops techniques for the analysis and interpretation of data obtained from beam-gas chemiluminescence experiments. These techniques are applied to experimental studies of atom transfer reactions of the type A + BC → AB + C. A procedure is developed for determining the product rotational alignment in the center-of-mass frame from polarization measurements of chemiluminescent atom-diatom exchange reactions under beam-gas conditions. Knowledge of a vector property of a reaction, such as product alignment, provides information on the disposition of angular momentum by a chemical reaction. Fluorescence polarization and hence product alignment are measured for two prototype reactions. The reaction of metastable calcium atoms with hydrogen-chloride gas yields highly aligned calcium-chloride product which exhibits little variation of alignment with vibrational state. The reaction of ground-state calcium with fluorine gas yields moderately aligned product which shows strong variation of alignment with vibration. A multi-surface direct-interaction model is developed to interpret product alignment and population data. The predictions of this model for the reaction of calcium with fluorine show reasonable agreement with experiment

Flow regimes in vertical gas-solid contact systems

Energy Technology Data Exchange (ETDEWEB)

Yerushalmi, J.; Cankurt, N. T.; Geldart, D.; Liss, B.

1976-01-01

The flow characteristics in fluidized beds, i.e., gas-solid systems, was studied to determine the flow regimes, the interaction of gas and solid in the various flow regimes and the dependence of this interaction and of transition between flow regimes on the properties of the gas and solid, on the gas and solid flow rates, and on the containing vessel. Fluidized beds with both coarse and fine particles are considered. Test results using high speed photography to view the operation of a 2-dimensional bed are discussed. (LCL)

The constitutive distributed parameter model of multicomponent chemical processes in gas, fluid and solid phase

International Nuclear Information System (INIS)

Niemiec, W.

1985-01-01

In the literature of distributed parameter modelling of real processes is not considered the class of multicomponent chemical processes in gas, fluid and solid phase. The aim of paper is constitutive distributed parameter physicochemical model, constructed on kinetics and phenomenal analysis of multicomponent chemical processes in gas, fluid and solid phase. The mass, energy and momentum aspects of these multicomponent chemical reactions and adequate phenomena are utilized in balance operations, by conditions of: constitutive invariance for continuous media with space and time memories, reciprocity principle for isotropic and anisotropic nonhomogeneous media with space and time memories, application of definitions of following derivative and equation of continuity, to the construction of systems of partial differential constitutive state equations, in the following derivative forms for gas, fluid and solid phase. Couched in this way all physicochemical conditions of multicomponent chemical processes in gas, fluid and solid phase are new form of constitutive distributed parameter model for automatics and its systems of equations are new form of systems of partial differential constitutive state equations in sense of phenomenal distributed parameter control

Solid-solid and gas-solid interactions induced during high-energy milling to produce PbTe nanopowders

Energy Technology Data Exchange (ETDEWEB)

Rojas-Chavez, H., E-mail: rojas_hugo@ittlahuac2.edu.mx [Instituto Tecnologico de Tlahuac - II (Mexico); Reyes-Carmona, F. [Facultad de Quimica - UNAM (Mexico); Garibay-Febles, V. [Instituto Mexicano del Petroleo, Laboratorio de Microscopia Electronica de Ultra Alta Resolucion (Mexico); Jaramillo-Vigueras, D. [Centro de Investigacion e Innovacion Tecnologica - IPN (Mexico)

2013-05-15

Transformations from precursors to nanoparticles by high-energy milling are promoted by two major driving forces, namely physical and/or chemical. While the former has been difficult to trace since stress, strain and recovery may occur almost simultaneously during milling, the latter has been sequentially followed as an evolution from precursors to intermediate phases and thereof to high purity nanocrystals. The specific objective of this work is to discern how solid-solid and partially solid-gas reactions manifest themselves correspondingly as a short-range diffusion through an interface or how vapor species, as a subliming phenomenon, grows as a different phase on an active local surface. These series of changes were traced by sub-cooling the as-milled powders extracted during a milling cycle. Through this experimental technique, samples were electron microscopically analyzed and where it was required, selected area electron diffraction images were obtained. High-resolution transmission electron microscopy results, unambiguously, confirm that nanocrystals in the last stage show a cubic morphology which average size distributions are around 17 nm.

Spectator Ions ARE Important! A Kinetic Study of the Copper-Aluminum Displacement Reaction

Science.gov (United States)

Sobel, Sabrina G.; Cohen, Skyler

2010-01-01

Surprisingly, spectator ions are responsible for unexpected kinetics in the biphasic copper(II)-aluminum displacement reaction, with the rate of reaction dependent on the identity of the otherwise ignored spectator ions. Application of a published kinetic analysis developed for a reaction between a rotating Al disk and a Cu(II) ion solution to the…

Chemical looping coal gasification with calcium ferrite and barium ferrite via solid–solid reactions

International Nuclear Information System (INIS)

Siriwardane, Ranjani; Riley, Jarrett; Tian, Hanjing; Richards, George

2016-01-01

Highlights: • BaFe 2 O 4 and CaFe 2 O 4 are excellent for chemical looping coal gasification. • BaFe 2 O 4 and CaFe 2 O 4 have minimal reactivity with synthesis gas. • Steam enhances the gasification process with these oxygen carriers. • Reaction rates of steam gasification of coal with CaFe 2 O 4 was better than with gaseous oxygen. • Coal gasification appears to be via solid–solid interaction with the oxygen carrier. - Abstract: Coal gasification to produce synthesis gas by chemical looping was investigated with two oxygen carriers, barium ferrite (BaFe 2 O 4 ) and calcium ferrite (CaFe 2 O 4 ). Thermo-gravimetric analysis (TGA) and fixed-bed flow reactor data indicated that a solid–solid interaction occurred between oxygen carriers and coal to produce synthesis gas. Both thermodynamic analysis and experimental data indicated that BaFe 2 O 4 and CaFe 2 O 4 have high reactivity with coal but have a low reactivity with synthesis gas, which makes them very attractive for the coal gasification process. Adding steam increased the production of hydrogen (H 2 ) and carbon monoxide (CO), but carbon dioxide (CO 2 ) remained low because these oxygen carriers have minimal reactivity with H 2 and CO. Therefore, the combined steam–oxygen carrier produced the highest quantity of synthesis gas. It appeared that neither the water–gas shift reaction nor the water splitting reaction promoted additional H 2 formation with the oxygen carriers when steam was present. Wyodak coal, which is a sub-bituminous coal, had the best gasification yield with oxygen carrier–steam while Illinois #6 coal had the lowest. The rate of gasification and selectivity for synthesis gas production was significantly higher when these oxygen carriers were present during steam gasification of coal. The rates and synthesis gas yields during the temperature ramps of coal–steam with oxygen carriers were better than with gaseous oxygen.

Excitons in the rare gas solids

International Nuclear Information System (INIS)

1988-01-01

Excitons play a prominent role in the chemistry and physics of condensed matter. Excitons in the rare gas solids, the prototypical van der Waals insulators, will be the focus of the remainder of this report. The goal here is to investigate the controversies surrounding the description of excitons in insulators and, therefore the simplest class of these solids, namely the rare gas solids, is chosen as the exemplary system. Specific problems associated with molecular crystals are, therefore, avoided and only the salient features of excitons are thus considered. 47 refs., 9 figs., 4 tabs

The Pictet-Spengler reaction in solid-phase combinatorial chemistry

DEFF Research Database (Denmark)

Nielsen, Thomas E; Diness, Frederik; Meldal, Morten

2003-01-01

The Pictet-Spengler reaction is an important reaction for the generation of tetrahydro-beta-carbolines and tetrahydroisoquinoline ring systems, which exhibit a range of biological and pharmacological properties. This review covers the solid-phase Pictet-Spengler reaction, as employed in solid...

The gas-solid trickle-flow reactor for the catalytic oxidation of hydrogen sulphide: a trickle-phase model

NARCIS (Netherlands)

Verver, A.B.; van Swaaij, Willibrordus Petrus Maria

1987-01-01

The oxidation of H2S by O2 producing elemental sulphur has been studied at temperatures of 100–300°C and at atmospheric pressure in a laboratory-scale gas-solid trickle-flow reactor. In this reactor one of the reaction products, i.e. sulphur, is removed continuously by flowing solids. A porous,

Marginal greenhouse gas emissions displacement of wind power in Great Britain

International Nuclear Information System (INIS)

Thomson, R. Camilla; Harrison, Gareth P.; Chick, John P.

2017-01-01

There is considerable uncertainty over the effect of wind power on the operation of power systems, and the consequent greenhouse gas (GHG) emissions displacement; this is used to project emissions reductions that inform energy policy. Currently, it is approximated as the average emissions of the whole system, despite an acknowledgement that wind will actually displace only the generators operating on the margin. This article presents a methodology to isolate the marginal emissions displacement of wind power from historical empirical data, taking into account the impact on the operating efficiency of coal and CCGT plants. For Great Britain over 2009–2014, it was found that marginal emissions displacement has generally been underestimated with, for example, the emissions displacement factor for wind being 21% higher than that the average emissions factor in 2010. The actual displacement depends upon the relative merit of coal and CCGT, with a greater discrepancy between marginal displacement and average emissions during more normal system operation, suggesting that policies to penalise high-carbon generation can increase the effectiveness of wind at reducing GHG emissions. Furthermore, it was also identified that wind power is almost as technically effective as demand-side reductions at decreasing GHG emissions from power generation. - Highlights: • Marginal emissions displacement was calculated from operational data for 2009–2014. • Existing estimates of emissions displacement are generally low. • Emissions displacement is a function of the relative merit of coal and CCGT plants. • Policies to penalise high-carbon generation should increase emissions displacement. • Wind almost as effective as demand-reduction at reducing emissions.

ON THE SYNTHESIS OF MOLYBDENUM CARBIDE WITH COBALT ADDITION VIA GAS-SOLID REACTIONS IN A CH4/H2 ATMOSPHERE

Directory of Open Access Journals (Sweden)

C. P. B. Araujo

Full Text Available Abstract Due to ever more severe environmental regulations regarding SOx, NOx and other pollutants' emissions, there has been an interest in developing new and improved catalysts for hydroprocessing reactions. Mo2C has been reported to display good selectivity and activity for those reactions, especially for HDS. Addition of another metal to the carbide structure may improve catalytic properties. Mo2C with low cobalt addition (2.5 and 5% was obtained via gas-solid reaction in a fixed bed reactor with CH4 (5%/H2 atmosphere. XRD and TG/DTA analysis of the precursors were carried out in order to understand its mass loss profile, doping metal presence and phase distributions. CoMoO4 as well as MoO3 were identified after calcining doped precursors at 600 °C/180min. SEM, XRD, XRF, TOC, BET and laser granulometric analysis of the reaction products were also performed. Compositions verified by XRF and theoretical values were compatible. At 700 °C both carbide (Mo2C and oxide (MoO2 phases are present, as identified in XRD analysis and observed by SEM. At 750 °C only single phase Mo2C was verified by XRD, indicating Co dispersion on the carbide matrix. Morphology at this temperature is compatible with pure Mo2C, though XRF indicates Co presence on the material.

Endothermic decompositions of inorganic monocrystalline thin plates. II. Displacement rate modulation of the reaction front

Science.gov (United States)

Bertrand, G.; Comperat, M.; Lallemant, M.

1980-09-01

Copper sulfate pentahydrate dehydration into trihydrate was investigated using monocrystalline platelets with (110) crystallographic orientation. Temperature and pressure conditions were selected so as to obtain elliptical trihydrate domains. The study deals with the evolution, vs time, of elliptical domain dimensions and the evolution, vs water vapor pressure, of the {D}/{d} ratio of ellipse axes and on the other hand of the interface displacement rate along a given direction. The phenomena observed are not basically different from those yielded by the overall kinetic study of the solid sample. Their magnitude, however, is modulated depending on displacement direction. The results are analyzed within the scope of our study of endothermic decomposition of solids.

Isotope exchange reaction on solid breeder materials

International Nuclear Information System (INIS)

Baba, A.; Nishikawa, M.; Eguchi, T.; Kawagoe, T.

2000-01-01

Lithium ceramic materials such as Li 2 O, LiAlO 2 , Li 2 ZrO 3 , Li 2 TiO 3 and Li 4 SiO 4 are considered to be as candidate for the tritium breeding material in a deuterium-tritium (D-T) fusion reactor. In the recent blanket designs, helium gas with hydrogen or deuterium is planned to be used as the blanket purge gas to reduce tritium inventory and promote tritium release from the breeding material. In addition, the rate of isotope exchange reaction between hydrogen isotopes in the purge gas and tritium on the surface of the breeding material is necessary to analyze the tritium release behavior from the breeding materials. However, the rate of isotope exchange reactions between hydrogen isotopes in the purge gas and tritium on the surface of those materials has not been quantified until recently. Recently, the present authors quantified the rate of isotope exchange reaction on Li 2 O and Li 2 ZrO 3 . The overall mass transfer coefficients representing the isotope exchange reaction between H 2 and D 2 O on breeding materials or the same between D 2 and H 2 O are experimentally obtained in this study. Comparison to isotope exchange reaction rates on various breeding materials is also performed in this study. Discussions about the effects of temperature, concentration of hydrogen in the purge gas or flow rate of the purge gas on the conversion of tritiated water to tritium gas are also performed

A model for a countercurrent gas—solid—solid trickle flow reactor for equilibrium reactions. The methanol synthesis

NARCIS (Netherlands)

Westerterp, K.R.; Kuczynski, M.

1987-01-01

The theoretical background for a novel, countercurrent gas—solid—solid trickle flow reactor for equilibrium gas reactions is presented. A one-dimensional, steady-state reactor model is developed. The influence of the various process parameters on the reactor performance is discussed. The physical

Displacer Diameter Effect in Displacer Pulse Tube Refrigerator

Science.gov (United States)

Zhu, Shaowei

2017-12-01

Gas driving displacer pulse tube refrigerators are one of the work recovery type of pulse tube refrigerators whose theoretical efficiency is the same as Stirling refrigerators'. Its cooling power is from the displacement of the displacer. Displace diameter, rod diameter and pressure drop of the regenerator influence the displacement, which are investigated by numerical simulation. It is shown that the displacement ratio of the displacer over the piston is almost not affected by the displacer diameter at the same rod diameter ratio, or displacer with different diameters almost has the same performance.

Analytical study of solids-gas two phase flow

International Nuclear Information System (INIS)

Hosaka, Minoru

1977-01-01

Fundamental studies were made on the hydrodynamics of solids-gas two-phase suspension flow, in which very small solid particles are mixed in a gas flow to enhance the heat transfer characteristics of gas cooled high temperature reactors. Especially, the pressure drop due to friction and the density distribution of solid particles are theoretically analyzed. The friction pressure drop of two-phase flow was analyzed based on the analytical result of the single-phase friction pressure drop. The calculated values of solid/gas friction factor as a function of solid/gas mass loading are compared with experimental results. Comparisons are made for Various combinations of Reynolds number and particle size. As for the particle density distribution, some factors affecting the non-uniformity of distribution were considered. The minimum of energy dispersion was obtained with the variational principle. The suspension density of particles was obtained as a function of relative distance from wall and was compared with experimental results. It is concluded that the distribution is much affected by the particle size and that the smaller particles are apt to gather near the wall. (Aoki, K.)

Solid electrolyte gas sensors based on cyclic voltammetry with one active electrode

Energy Technology Data Exchange (ETDEWEB)

Jasinski, G; Jasinski, P, E-mail: gregor@biomed.eti.pg.gda.pl [Gdansk University of Technology, Faculty of Electronics, Telecommunication and Informatics, Narutowicza 11/12, 80-233 Gdansk (Poland)

2011-10-29

Solid state gas sensors are cost effective, small, rugged and reliable. Typically electrochemical solid state sensors operate in either potentiometric or amperometric mode. However, a lack of selectivity is sometimes a shortcoming of such sensors. It seems that improvements of selectivity can be obtained in case of the electrocatalytic sensors, which operate in cyclic voltammetry mode. Their working principle is based on acquisition of an electric current, while voltage ramp is applied to the sensor. The current-voltage response depends in a unique way on the type and concentration of ambient gas. Most electrocatalytic sensors have symmetrical structure. They are in a form of pellets with two electrodes placed on their opposite sides. Electrochemical reactions occur simultaneously on both electrodes. In this paper results for sensors with only one active electrode exposed to ambient gas are presented. The other electrode was isolated from ambient gas with dielectric sealing. This sensor construction allows application of advanced measuring procedures, which permit sensor regeneration acceleration. Experiments were conducted on Nasicon sensors. Properties of two sensors, one with one active electrode and second with symmetrical structure, used for the detection of mixtures of NO{sub 2} and synthetic air are compared.

Interaction of cover and target with xenon gas in the IFE-reaction chamber

International Nuclear Information System (INIS)

Kuteev, Boris V.

2001-11-01

Interaction of a direct drive target and a cover, which is shielding the target against gas particle and heat flows in the reaction chamber of the Inertial Confinement Reactor, is considered. The cover is produced from solid gas -deuterium, neon of xenon. It is shown that at the SOMBRERO parameters the xenon cover with 5.6-mm size significantly reduces the heat flows onto the 4-mm target. The gas drag produces the deceleration of the target much larger than that for the cover due to large mass difference between them. The distance between the target and the cover is about 15 mm at the explosion point, which is sufficient for normal irradiation of the target by laser beams. Protection of the target against the wall radiation is necessary during the flight. Along with creation of reflecting layers over the target surface ablating layers from solid hydrogen or neon seem to be a solution. (author)

Nanocrystalline spinel ferrites by solid state reaction route

Indian Academy of Sciences (India)

Wintec

Nanocrystalline spinel ferrites by solid state reaction route. T K KUNDU* and S MISHRA. Department of Physics, Visva-Bharati, Santiniketan 731 235, India. Abstract. Nanostructured NiFe2O4, MnFe2O4 and (NiZn)Fe2O4 were synthesized by aliovalent ion doping using conventional solid-state reaction route. With the ...

The reductive decomposition of calcium sulphate I. Kinetics of the apparent solid-solid reaction

NARCIS (Netherlands)

Kamphuis, B.; Potma, A.W.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

1992-01-01

The reductive decomposition of calcium sulphate by hydrogen is used for the regeneration of calcium-based atmospheric fluidized bed combustion (AFBC) SO2 sorbents. The apparent solid¿solid reaction between CaS and CaSO4, one of the steps involved in the reaction mechanism of the reductive

Reactive solid surface morphology variation via ionic diffusion.

Science.gov (United States)

Sun, Zhenchao; Zhou, Qiang; Fan, Liang-Shih

2012-08-14

In gas-solid reactions, one of the most important factors that determine the overall reaction rate is the solid morphology, which can be characterized by a combination of smooth, convex and concave structures. Generally, the solid surface structure varies in the course of reactions, which is classically noted as being attributed to one or more of the following three mechanisms: mechanical interaction, molar volume change, and sintering. Here we show that if a gas-solid reaction involves the outward ionic diffusion of a solid-phase reactant then this outward ionic diffusion could eventually smooth the surface with an initial concave and/or convex structure. Specifically, the concave surface is filled via a larger outward diffusing surface pointing to the concave valley, whereas the height of the convex surface decreases via a lower outward diffusion flux in the vertical direction. A quantitative 2-D continuum diffusion model is established to analyze these two morphological variation processes, which shows consistent results with the experiments. This surface morphology variation by solid-phase ionic diffusion serves to provide a fourth mechanism that supplements the traditionally acknowledged solid morphology variation or, in general, porosity variation mechanisms in gas-solid reactions.

Solid state gas sensors. Industrial application

Energy Technology Data Exchange (ETDEWEB)

Fleischer, Maximilian [Siemens AG, Muenchen (Germany). Corporate Technology; Lehmann, Mirko (eds.) [Innovative Sensor Technology (IST) AG, Wattwil (Switzerland)

2012-11-01

Written by experts. Richly illustrated. Encourages future research and investments in the fascinating field of gas sensors. Gas sensor products are very often the key to innovations in the fields of comfort, security, health, environment, and energy savings. This compendium focuses on what the research community labels as solid state gas sensors, where a gas directly changes the electrical properties of a solid, serving as the primary signal for the transducer. It starts with a visionary approach to how life in future buildings can benefit from the power of gas sensors. The requirements for various applications, such as for example the automotive industry, are then discussed in several chapters. Further contributions highlight current trends in new sensing principles, such as the use of nanomaterials and how to use new sensing principles for innovative applications in e.g. meteorology. So as to bring together the views of all the different groups needed to produce new gas sensing applications, renowned industrial and academic representatives report on their experiences and expectations in research, applications and industrialisation.

Gas converter. Gaswandler

Energy Technology Data Exchange (ETDEWEB)

Eisenmann, A

1984-09-27

A gas converter is proposed for carbonisation gas containing hydrocarbons, consisting of a bricked shaft, which has a free combustion chamber and a solid bed of bulk grainy material with partly burnt hot carbonisation gases flowing through it as the lower boundary of this combustion chamber, in the upper part of which a hot reaction zone at about 1000 to 1200/sup 0/C is formed and which has a cracked gas extraction below the solid bed and an ash outlet. The solid bed is arranged at an angle to the vertical. The shaft has a solid material outlet for the bed material no longer capable of taking part in the reaction on the wall going obliquely downwards and a solid material inlet for new bulk bed material on the opposite wall going obliquely upwards.

Programming chemical kinetics: engineering dynamic reaction networks with DNA strand displacement

Science.gov (United States)

Srinivas, Niranjan

Over the last century, the silicon revolution has enabled us to build faster, smaller and more sophisticated computers. Today, these computers control phones, cars, satellites, assembly lines, and other electromechanical devices. Just as electrical wiring controls electromechanical devices, living organisms employ "chemical wiring" to make decisions about their environment and control physical processes. Currently, the big difference between these two substrates is that while we have the abstractions, design principles, verification and fabrication techniques in place for programming with silicon, we have no comparable understanding or expertise for programming chemistry. In this thesis we take a small step towards the goal of learning how to systematically engineer prescribed non-equilibrium dynamical behaviors in chemical systems. We use the formalism of chemical reaction networks (CRNs), combined with mass-action kinetics, as our programming language for specifying dynamical behaviors. Leveraging the tools of nucleic acid nanotechnology (introduced in Chapter 1), we employ synthetic DNA molecules as our molecular architecture and toehold-mediated DNA strand displacement as our reaction primitive. Abstraction, modular design and systematic fabrication can work only with well-understood and quantitatively characterized tools. Therefore, we embark on a detailed study of the "device physics" of DNA strand displacement (Chapter 2). We present a unified view of strand displacement biophysics and kinetics by studying the process at multiple levels of detail, using an intuitive model of a random walk on a 1-dimensional energy landscape, a secondary structure kinetics model with single base-pair steps, and a coarse-grained molecular model that incorporates three-dimensional geometric and steric effects. Further, we experimentally investigate the thermodynamics of three-way branch migration. Our findings are consistent with previously measured or inferred rates for

Meta-analysis of greenhouse gas displacement factors of wood product substitution

International Nuclear Information System (INIS)

Sathre, Roger; O'Connor, Jennifer

2010-01-01

A displacement factor can express the efficiency of using biomass to reduce net greenhouse gas (GHG) emission, by quantifying the amount of emission reduction achieved per unit of wood use. Here we integrate data from 21 different international studies in a meta-analysis of the displacement factors of wood products substituted in place of non-wood materials. We calculate the displacement factors in consistent units of tons of carbon (tC) of emission reduction per tC in wood product. The displacement factors range from a low of -2.3 to a high of 15, with most lying in the range of 1.0 to 3.0. The average displacement factor value is 2.1, meaning that for each tC in wood products substituted in place of non-wood products, there occurs an average GHG emission reduction of approximately 2.1 tC. Expressed in other units, this value corresponds to roughly 3.9 t CO 2 eq emission reduction per ton of dry wood used. The few cases of negative displacement factors are the result of worst-case scenarios that are unrealistic in current practice. This meta-analysis quantifies the range of GHG benefits of wood substitution, and provides a clear climate rationale for increasing wood substitution in place of other products, provided that forests are sustainably managed and that wood residues are used responsibly.

Meta-analysis of greenhouse gas displacement factors of wood product substitution

Energy Technology Data Exchange (ETDEWEB)

Sathre, Roger [Ecotechnology, Mid Sweden University, 83125 Ostersund (Sweden); O' Connor, Jennifer [FPInnovations-Forintek, Vancouver, BC, Canada V6T 1W5 (Canada)

2010-04-15

A displacement factor can express the efficiency of using biomass to reduce net greenhouse gas (GHG) emission, by quantifying the amount of emission reduction achieved per unit of wood use. Here we integrate data from 21 different international studies in a meta-analysis of the displacement factors of wood products substituted in place of non-wood materials. We calculate the displacement factors in consistent units of tons of carbon (tC) of emission reduction per tC in wood product. The displacement factors range from a low of -2.3 to a high of 15, with most lying in the range of 1.0 to 3.0. The average displacement factor value is 2.1, meaning that for each tC in wood products substituted in place of non-wood products, there occurs an average GHG emission reduction of approximately 2.1 tC. Expressed in other units, this value corresponds to roughly 3.9 t CO{sub 2} eq emission reduction per ton of dry wood used. The few cases of negative displacement factors are the result of worst-case scenarios that are unrealistic in current practice. This meta-analysis quantifies the range of GHG benefits of wood substitution, and provides a clear climate rationale for increasing wood substitution in place of other products, provided that forests are sustainably managed and that wood residues are used responsibly.

Sulfur Poisoning of the Water Gas Shift Reaction on Anode Supported Solid Oxide Fuel Cells

DEFF Research Database (Denmark)

Hagen, Anke

2013-01-01

resistance increased both in the high and low frequency region, which indicates a strong poisoning of the water gas shift reaction and thus a lack of hydrogen fuel in addition to the poisoning of the electrochemical hydrogen oxidation. All poisoning effects are reversible under the applied operating...

Mass transfer between gas and particles in a gas-solid trickle flow reactor

NARCIS (Netherlands)

Kiel, J.H.A.; Kiel, J.H.A.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

1992-01-01

Gas-solids mass transfer was studied for counter-current flow of gas and millimetre-sized solid particles over an inert packing at dilute phase or trickle flow conditions. Experimental data were obtained from the adsorption of water vapour on 640 and 2200 ¿m diameter molecular sieve spheres at

Study on fine particles influence on sodium sulfite and oxygen gas-liquid reaction

Energy Technology Data Exchange (ETDEWEB)

Tao, Shuchang; Zhao, Bo; Wang, Shujuan; Zhuo, Yuqun; Chen, Changhe [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering; Ministry of Education, Beijing (China). Key Lab. for Thermal Science and Power Engineering

2013-07-01

Wet limestone scrubbing is the most common flue gas desulfurization process for control of sulfur dioxide emissions from the combustion of fossil fuels, and forced oxidation is a key part of the reaction. During the reaction which controlled by gas-liquid mass transfer, the fine particles' characteristic, size, solid loading and temperature has a great influence on gas-liquid mass transfer. In the present work is to explain how these factors influence the reaction between Na{sub 2}SO{sub 3} and O{sub 2} and find the best react conditions through experiment. The oxidation rate was experimentally studied by contacting pure oxygen with a sodium sulfite solution with active carbon particle in a stirred tank, and the system pressure drop was record by the pressure sensor. At the beginning the pressure is about 215 kPa and Na{sub 2}SO{sub 3} is about 0.5mol/L. The temperature is 40, 50, 60, 70, 80 C. Compare the results of no particles included, we can conclude that high temperature, proper loadings and smaller particles resulting in higher mass transfer coefficients k{sub L}.

The potential for buoyant displacement gas release events in Tank 241-SY-102 after waste transfer from Tank 241-SY-101

International Nuclear Information System (INIS)

Wells, BE; Meyer, P.E.; Chen, G.

2000-01-01

Tank 241-SY-101 (SY-101) is a double-shell, radioactive waste storage tank with waste that, before the recent transfer and water back-dilution operations, was capable of retaining gas and producing buoyant displacement (BD) gas release events (GREs). Some BD GREs caused gas concentrations in the tank headspace to exceed the lower flammability limit (LFL). A BD GRE occurs when a portion of the nonconvective layer retains enough gas to become buoyant, rises to the waste surface, breaks up, and releases some of its stored gas. The installation of a mixer pump in 1993 successfully mitigated gas retention in the settled solids layer in SY-101 and has since prevented BD GREs. However, operation of the mixer pump over the years caused gas retention in the floating crust layer and a corresponding accelerated waste level growth. The accelerating crust growth trend observed in 1997--98 led to initiation of sequences of waste removal and water back-dilutions in December 1999. Waste is removed from the mixed slurry layer in Tank SY-101 and transferred into Tank 241-Sy-102 (SY-102). Water is then added back to dissolve soluble solids that retain gas. The initial transfer of 89,500 gallons of SY-101 waste, diluted in-line at 0.94:1 by volume with water, to SY-102 was conducted in December 1999. The second transfer of 230,000 gallons of original SY-101 waste, diluted approximately 0.9:1, was completed in January 2000, and the third transfer of 205,500 gallons of original SY-101 waste diluted at 0.9:1 was completed in March 2000

Chemical reaction on solid surface observed through isotope tracer technique

International Nuclear Information System (INIS)

Tanaka, Ken-ichi

1983-01-01

In order to know the role of atoms and ions on solid surfaces as the partners participating in elementary processes, the literatures related to the isomerization and hydrogen exchanging reaction of olefines, the hydrogenation of olefines, the metathesis reaction and homologation of olefines based on solid catalysts were reviewed. Various olefines, of which the hydrogen atoms were substituted with deuterium at desired positions, were reacted using various solid catalysts such as ZnO, K 2 CO 3 on C, MoS 2 (single crystal and powder) and molybdenum oxide (with various carriers), and the infra-red spectra of adsorbed olefines on catalysts, the isotope composition of reaction products and the production rate of the reaction products were measured. From the results, the bonding mode of reactant with the atoms and ions on solid surfaces, and the mechanism of the elementary process were considered. The author emphasized that the mechanism of the chemical reaction on solid surfaces and the role of active points or catalysts can be made clear to the considerable extent by combining isotopes suitably. (Yoshitake, I.)

Prismatic displacement effect of progressive multifocal glasses on reaction time and accuracy in elderly people.

Science.gov (United States)

Ellison, Ashton C; Campbell, A John; Robertson, M Clare; Sanderson, Gordon F

2014-01-01

Multifocal glasses (bifocals, trifocals, and progressives) increase the risk of falling in elderly people, but how they do so is unclear. To explain why glasses with progressive addition lenses increase the risk of falls and whether this can be attributed to false projection, this study aimed to 1) map the prismatic displacement of a progressive lens, and 2) test whether this displacement impaired reaction time and accuracy. The reaction times of healthy ≥75-year-olds (31 participants) were measured when grasping for a bar and touching a black line. Participants performed each test twice, wearing their progressives and new, matched single vision (distance) glasses in random order. The line and bar targets were positioned according to the maximum and minimum prismatic displacement effect through the progressive lens, mapped using a focimeter. Progressive spectacle lenses have large areas of prismatic displacement in the central visual axis and edges. Reaction time was faster for progressives compared with single vision glasses with a centrally-placed horizontal grab bar (mean difference 101 ms, P=0.011 [repeated measures analysis]) and a horizontal black line placed 300 mm below center (mean difference 80 ms, P=0.007). There was no difference in accuracy between the two types of glasses. Older people appear to adapt to the false projection of progressives in the central visual axis. This adaptation means that swapping to new glasses or a large change in prescription may lead to a fall. Frequently updating glasses may be more beneficial.

Niobium carbide synthesis by solid-gas reaction using a rotating cylinder reactor

International Nuclear Information System (INIS)

Fontes, F.A.O.; Gomes, K.K.P.; Oliveira, S.A.; Souza, C.P.; Sousa, J.F.; Rio Grande do Norte Univ., Natal, RN

2004-01-01

A rotating cylinder reactor was designed for the synthesis of niobium carbide powders at 1173 K. Niobium carbide, NbC, was prepared by carbothermal reduction starting from commercial niobium pentoxide powders. The reactor was heated using a custom-made, two-part, hinged, electric furnace with programmable temperature control. The design and operational details of the reactor are presented. The longitudinal temperature gradient inside the reactor was determined. Total reaction time was monitored by a gas chromatograph equipped with an FID detector for determination of methane concentrations. The results show that time of reaction depended on rotation speed. NbC was also prepared in a static-bed alumina reactor using the same conditions as in the previous case. The niobium carbide powders were characterized by X-ray diffraction and compared with commercially available products. Morphological, particle size distribution and surface area analyses were obtained using SEM, LDPS and BET, respectively. Therefore, the present study offers a significant technological contribution to the synthesis of NbC powders in a rotating cylinder reactor. (author)

Removing antimony from waste lead storage batteries alloy by vacuum displacement reaction technology.

Science.gov (United States)

Liu, Tiantian; Qiu, Keqiang

2018-04-05

With the wide application of lead acid battery, spent lead acid battery has become a serious problem to environmental protection and human health. Though spent battery can be a contaminant if not handled properly, it is also an important resource to obtain refined lead. Nowadays, the Sb-content in lead storage batteries is about 0.5-3 wt%, which is higher than the Sb-content in the crude lead. However, there are few reports about the process of removing antimony from high-antimony lead bullion. In this study, vacuum displacement reaction technology, a new process for removing antimony from high-antimony lead melts, was investigated. During this process, lead oxide was added to the system and antimony from lead melts was converted into antimony trioxide, which easily was evaporated under vacuum so that antimony was removed from lead melts. The experimental results demonstrated that Sb-content in lead melts decreased from 2.5% to 23 ppm under following conditions: mass ratio of PbO/lead bullion of 0.33, residual gas pressure of 30 Pa, melt temperature of 840 °C, reaction time of 60 min. The distillate gotten can be used as by-product to produce antimony white. Moreover, this study is of importance to recycling of waste lead storage batteries alloy. Copyright © 2018 Elsevier B.V. All rights reserved.

Gas driven displacement in a Hele-Shaw cell with chemical reaction

Science.gov (United States)

White, Andrew; Ward, Thomas

2011-11-01

Injecting a less viscous fluid into a more viscous fluid produces instabilities in the form of fingering which grow radially from the less viscous injection point (Saffman & Taylor, Proc. R. Soc. Lon. A, 1958). For two non-reacting fluids in a radial Hele-Shaw cell the ability of the gas phase to penetrate the liquid phase is largely dependent on the gap height, liquid viscosity and gas pressure. In contrast combining two reactive fluids such as aqueous calcium hydroxide and carbon dioxide, which form a precipitate, presents a more complex but technically relevant system. As the two species react calcium carbonate precipitates and increases the aqueous phase visocosity. This change in viscosity may have a significant impact on how the gas phase penetrates the liquid phase. Experimental are performed in a radial Hele-Shaw cell with gap heights O(10-100) microns by loading a single drop of aqueous calcium hydroxide and injecting carbon dioxide into the drop. The calcium hydroxide concentration, carbon dioxide pressure and gap height are varied and images of the gas penetration are analyzed to determine residual film thickness and bursting times.

Volatiles from solids

Energy Technology Data Exchange (ETDEWEB)

Loughrey, C T

1939-08-24

To remove volatiles from solids, such as oil shale, gases, and/or vapours are passed through a mass of the materials, the vapours and gases separated, and the vapours condensed. The volatile-containing solid materials are fed to a retort, and a shaft is driven to rotate an impeller so as to displace the liquid and create a vortex tube, which draws in gas from the atmosphere through an intake, twyer, interstices in the material in the retort, a conduit, chamber, tubes, another chamber and cylinder. This gas is carried outwardly and upwardly by the vortices in the liquid and is carried to discharge through three conduits. The vapours entrained by the gas are part condensed in the liquid and the remainder directed to a condenser. Steam may be delivered to the twyer through a nozzle of a pipe, with or without air, and combustible hydrocarbon fuel may be fed through the burner nozzle or solid fuel may be directed from feeder and combusted in the twyer.

Axial dispersion of gas and solid phases in a gas—solid packed column at trickle flow

NARCIS (Netherlands)

Roes, A.W.M.; van Swaaij, Willibrordus Petrus Maria

1979-01-01

Axial dispersion of gas and solid phases in a gas—solid packed column at trickle flow, a promising new countercurrent operation, was evaluated using residence time distribution (RTD) experiments. The column was packed with dumped Pall rings, the gas phase was air at ambient conditions and the solid

Chemical transport reactions

CERN Document Server

Schäfer, Harald

2013-01-01

Chemical Transport Reactions focuses on the processes and reactions involved in the transport of solid or liquid substances to form vapor phase reaction products. The publication first offers information on experimental and theoretical principles and the transport of solid substances and its special applications. Discussions focus on calculation of the transport effect of heterogeneous equilibria for a gas motion between equilibrium spaces; transport effect and the thermodynamic quantities of the transport reaction; separation and purification of substances by means of material transport; and

Direct gas-solid carbonation of serpentinite residues in the absence and presence of water vapor: a feasibility study for carbon dioxide sequestration.

Science.gov (United States)

Veetil, Sanoopkumar Puthiya; Pasquier, Louis-César; Blais, Jean-François; Cecchi, Emmanuelle; Kentish, Sandra; Mercier, Guy

2015-09-01

Mineral carbonation of serpentinite mining residue offers an environmentally secure and permanent storage of carbon dioxide. The strategy of using readily available mining residue for the direct treatment of flue gas could improve the energy demand and economics of CO2 sequestration by avoiding the mineral extraction and separate CO2 capture steps. The present is a laboratory scale study to assess the possibility of CO2 fixation in serpentinite mining residues via direct gas-solid reaction. The degree of carbonation is measured both in the absence and presence of water vapor in a batch reactor. The gas used is a simulated gas mixture reproducing an average cement flue gas CO2 composition of 18 vol.% CO2. The reaction parameters considered are temperature, total gas pressure, time, and concentration of water vapor. In the absence of water vapor, the gas-solid carbonation of serpentinite mining residues is negligible, but the residues removed CO2 from the feed gas possibly due to reversible adsorption. The presence of small amount of water vapor enhances the gas-solid carbonation, but the measured rates are too low for practical application. The maximum CO2 fixation obtained is 0.07 g CO2 when reacting 1 g of residue at 200 °C and 25 barg (pCO2 ≈ 4.7) in a gas mixture containing 18 vol.% CO2 and 10 vol.% water vapor in 1 h. The fixation is likely surface limited and restricted due to poor gas-solid interaction. It was identified that both the relative humidity and carbon dioxide-water vapor ratio have a role in CO2 fixation regardless of the percentage of water vapor.

Zirconia-based solid state chemical gas sensors

CERN Document Server

Zhuiykov, S

2000-01-01

This paper presents an overview of chemical gas sensors, based on solid state technology, that are sensitive to environmental gases, such as O sub 2 , SO sub x , NO sub x , CO sub 2 and hydrocarbons. The paper is focussed on performance of electrochemical gas sensors that are based on zirconia as a solid electrolyte. The paper considers sensor structures and selection of electrode materials. Impact of interfaces on sensor performance is discussed. This paper also provides a brief overview of electrochemical properties of zirconia and their effect on sensor performance. Impact of auxiliary materials on sensors performance characteristics, such as sensitivity, selectivity, response time and recovery time, is also discussed. Dual gas sensors that can be applied for simultaneous monitoring of the concentration of both oxygen and other gas phase components, are briefly considered

Critical comparison of hydrodynamic models for gas-solid fluidized beds - Part II: freely bubbling gas-solid fluidized beds

NARCIS (Netherlands)

Patil, D.J.; van Sint Annaland, M.; Kuipers, J.A.M.

2005-01-01

Correct prediction of spontaneous bubble formation in freely bubbling gas¿solid fluidized beds using Eulerian models, strongly depends on the description of the internal momentum transfer in the particulate phase. In this part, the comparison of the simple classical model, describing the solid phase

Solid Base Catalysis

CERN Document Server

Ono, Yoshio

2011-01-01

The importance of solid base catalysts has come to be recognized for their environmentally benign qualities, and much significant progress has been made over the past two decades in catalytic materials and solid base-catalyzed reactions. The book is focused on the solid base. Because of the advantages over liquid bases, the use of solid base catalysts in organic synthesis is expanding. Solid bases are easier to dispose than liquid bases, separation and recovery of products, catalysts and solvents are less difficult, and they are non-corrosive. Furthermore, base-catalyzed reactions can be performed without using solvents and even in the gas phase, opening up more possibilities for discovering novel reaction systems. Using numerous examples, the present volume describes the remarkable role solid base catalysis can play, given the ever increasing worldwide importance of "green" chemistry. The reader will obtain an overall view of solid base catalysis and gain insight into the versatility of the reactions to whic...

Confined-but-Connected Quantum Solids via Controlled Ligand Displacement

KAUST Repository

Baumgardner, William J.

2013-07-10

Confined-but-connected quantum dot solids (QDS) combine the advantages of tunable, quantum-confined energy levels with efficient charge transport through enhanced electronic interdot coupling. We report the fabrication of QDS by treating self-assembled films of colloidal PbSe quantum dots with polar nonsolvents. Treatment with dimethylformamide balances the rates of self-assembly and ligand displacement to yield confined-but-connected QDS structures with cubic ordering and quasi-epitaxial interdot connections through facets of neighboring dots. The QDS structure was analyzed by a combination of transmission electron microscopy and wide-angle and small-angle X-ray scattering. Excitonic absorption signatures in optical spectroscopy confirm that quantum confinement is preserved. Transport measurements show significantly enhanced conductivity in treated films. © 2013 American Chemical Society.

Computer codes for simulating atomic-displacement cascades in solids subject to irradiation

International Nuclear Information System (INIS)

Asaoka, Takumi; Taji, Yukichi; Tsutsui, Tsuneo; Nakagawa, Masayuki; Nishida, Takahiko

1979-03-01

In order to study atomic displacement cascades originating from primary knock-on atoms in solids subject to incident radiation, the simulation code CASCADE/CLUSTER is adapted for use on FACOM/230-75 computer system. In addition, the code is modified so as to plot the defect patterns in crystalline solids. As other simulation code of the cascade process, MARLOWE is also available for use on the FACOM system. To deal with the thermal annealing of point defects produced in the cascade process, the code DAIQUIRI developed originally for body-centered cubic crystals is modified to be applicable also for face-centered cubic lattices. By combining CASCADE/CLUSTER and DAIQUIRI, we then prepared a computer code system CASCSRB to deal with heavy irradiation or saturation damage state of solids at normal temperature. Furthermore, a code system for the simulation of heavy irradiations CASCMARL is available, in which MARLOWE code is substituted for CASCADE in the CASCSRB system. (author)

Coherent diffractive imaging of solid state reactions in zinc oxide crystals

Science.gov (United States)

Leake, Steven J.; Harder, Ross; Robinson, Ian K.

2011-11-01

We investigated the doping of zinc oxide (ZnO) microcrystals with iron and nickel via in situ coherent x-ray diffractive imaging (CXDI) in vacuum. Evaporated thin metal films were deposited onto the ZnO microcrystals. A single crystal was selected and tracked through annealing cycles. A solid state reaction was observed in both iron and nickel experiments using CXDI. A combination of the shrink wrap and guided hybrid-input-output phasing methods were applied to retrieve the electron density. The resolution was 33 nm (half order) determined via the phase retrieval transfer function. The resulting images are nevertheless sensitive to sub-angstrom displacements. The exterior of the microcrystal was found to degrade dramatically. The annealing of ZnO microcrystals coated with metal thin films proved an unsuitable doping method. In addition the observed defect structure of one crystal was attributed to the presence of an array of defects and was found to change upon annealing.

Influence of vibrations of gas molecules on neutron reaction cross sections

Science.gov (United States)

Bowman, C. D.; Schrack, R. A.

1980-01-01

The change in molecular vibrational energy upon absorption of a neutron by a nucleus bound in a free molecule can influence resonance shape and other aspects of neutron reaction cross sections. A formalism is developed for centrosymmetric molecules such as UF6 and applied to the shape of the 6.67 eV resonance in 238U. The ratio of the resonance shape for 238UF6 gas and for solid 238U3O8 has been measured and compared with the calculation. Reasonable agreement is obtained indicating the validity of the calculation and the necessity to include vibration effects to avoid large errors in measurements and calculations on gascontaining systems. NUCLEAR REACTIONS 238U(n,γ) measured at 6.67 eV resonance; Effect of molecular vibrations studied experimentally and theoretically.

Heat transfer across the interface between nanoscale solids and gas.

Science.gov (United States)

Cheng, Chun; Fan, Wen; Cao, Jinbo; Ryu, Sang-Gil; Ji, Jie; Grigoropoulos, Costas P; Wu, Junqiao

2011-12-27

When solid materials and devices scale down in size, heat transfer from the active region to the gas environment becomes increasingly significant. We show that the heat transfer coefficient across the solid-gas interface behaves very differently when the size of the solid is reduced to the nanoscale, such as that of a single nanowire. Unlike for macroscopic solids, the coefficient is strongly pressure dependent above ∼10 Torr, and at lower pressures it is much higher than predictions of the kinetic gas theory. The heat transfer coefficient was measured between a single, free-standing VO(2) nanowire and surrounding air using laser thermography, where the temperature distribution along the VO(2) nanowire was determined by imaging its domain structure of metal-insulator phase transition. The one-dimensional domain structure along the nanowire results from the balance between heat generation by the focused laser and heat dissipation to the substrate as well as to the surrounding gas, and thus serves as a nanoscale power-meter and thermometer. We quantified the heat loss rate across the nanowire-air interface, and found that it dominates over all other heat dissipation channels for small-diameter nanowires near ambient pressure. As the heat transfer across the solid-gas interface is nearly independent of the chemical identity of the solid, the results reveal a general scaling relationship for gaseous heat dissipation from nanostructures of all solid materials, which is applicable to nanoscale electronic and thermal devices exposed to gaseous environments.

Atomic mean-square displacements and the critical-voltage effect in cubic solid solutions

International Nuclear Information System (INIS)

Shirley, C.G.; Fisher, R.M.

1979-01-01

The critical-voltage phenomena observed in high-voltage electron microscope images of bend contours as well as in corresponding Kikuchi or convergent-beam diffraction patterns provide sensitive methods of determining submicroscopic alloy parameters such as Debye temperatures, short-range order, and atomic scattering factors. Only a very limited number of critical voltages can be observed in metal crystals in the voltage range usually available, 100 to 1200 kV, so that quantitative interpretation of the data must be based on a few-parameter model which incorporates all the pertinent factors. A satisfactory two-parameter model has been developed which can be used to interpret or compute the critical voltages of substitutional solid solutions as functions of composition, temperature and short-range order. In the alloy systems Fe-Cr, Ni-Au, Cu-Au and Cu-Al, sufficient critical voltage data are available to derive the model parameters which pertain to atomic bonding in the lattice. In addition to atomic scattering amplitudes, the critical voltage depends strongly on the atomic mean-square displacements. The static contribution to the mean-square displacements is large in alloys with large atomic-radius disparity, and is especially sensitive to short-range order in f.c.c. solid solutions. Well-defined best estimates for the model parameters are used to predict the critical voltage and its sensitivity to composition, temperature and short-range order for a large number of solid solutions. Systems for which critical-voltage studies may be of considerable interest are indicated. (author)

Study of solid/liquid and solid/gas interfaces in Cu–isoleucine complex by surface X-ray diffraction

International Nuclear Information System (INIS)

Ferrer, Pilar; Rubio-Zuazo, Juan; Castro, German R.

2013-01-01

The enzymes could be understood like structures formed by amino acids bonded with metals, which act as active sites. The research on the coordination of metal–amino acid complexes will bring light on the behavior of metal enzymes, due to the close relation existing between the atomic structure and the functionality. The Cu–isoleucine bond is considered as a good model system to attain a better insight into the characteristics of naturally occurring copper metalloproteins. The surface structure of metal–amino acid complex could be considered as a more realistic model for real systems under biologic working conditions, since the molecular packing is decreased. In the surface, the structural constrains are reduced, keeping the structural capability of surface complex to change as a function of the surrounding environment. In this work, we present a surface X-ray diffraction study on Cu–isoleucine complex under different ambient conditions. Cu(Ile) 2 crystals of about 5 mm × 5 mm × 1 mm have been growth, by seeding method in a supersaturated solution, presenting a surface of high quality. The sample for the surface diffraction study was mounted on a cell specially designed for solid/liquid or solid/gas interface analysis. The Cu–isoleucine crystal was measured under a protective dry N 2 gas flow and in contact with a saturated metal amino acid solution. The bulk and the surface signals were compared, showing different atomic structures. In both cases, from surface diffraction data, it is observed that the atomic structure of the top layer undergoes a clear structural deformation. A non-uniform surface relaxation is observed producing an inhomogeneous displacement of the surface atoms towards the surface normal.

Prismatic displacement effect of progressive multifocal glasses on reaction time and accuracy in elderly people

Directory of Open Access Journals (Sweden)

Ellison AC

2014-05-01

Full Text Available Ashton C Ellison, A John Campbell, M Clare Robertson, Gordon F SandersonDunedin School of Medicine, Department of Medicine, Dunedin, New ZealandBackground: Multifocal glasses (bifocals, trifocals, and progressives increase the risk of falling in elderly people, but how they do so is unclear. To explain why glasses with progressive addition lenses increase the risk of falls and whether this can be attributed to false projection, this study aimed to 1 map the prismatic displacement of a progressive lens, and 2 test whether this displacement impaired reaction time and accuracy.Methods: The reaction times of healthy ≥75-year-olds (31 participants were measured when grasping for a bar and touching a black line. Participants performed each test twice, wearing their progressives and new, matched single vision (distance glasses in random order. The line and bar targets were positioned according to the maximum and minimum prismatic displacement effect through the progressive lens, mapped using a focimeter.Results: Progressive spectacle lenses have large areas of prismatic displacement in the central visual axis and edges. Reaction time was faster for progressives compared with single vision glasses with a centrally-placed horizontal grab bar (mean difference 101 ms, P=0.011 [repeated measures analysis] and a horizontal black line placed 300 mm below center (mean difference 80 ms, P=0.007. There was no difference in accuracy between the two types of glasses.Conclusion: Older people appear to adapt to the false projection of progressives in the central visual axis. This adaptation means that swapping to new glasses or a large change in prescription may lead to a fall. Frequently updating glasses may be more beneficial.Keywords: fall prevention, false projection, stored visual spatial information

Kinetic concepts of thermally stimulated reactions in solids

Science.gov (United States)

Vyazovkin, Sergey

Historical analysis suggests that the basic kinetic concepts of reactions in solids were inherited from homogeneous kinetics. These concepts rest upon the assumption of a single-step reaction that disagrees with the multiple-step nature of solid-state processes. The inadequate concepts inspire such unjustified anticipations of kinetic analysis as evaluating constant activation energy and/or deriving a single-step reaction mechanism for the overall process. A more adequate concept is that of the effective activation energy, which may vary with temperature and extent of conversion. The adequacy of this concept is illustrated by literature data as well as by experimental data on the thermal dehydration of calcium oxalate monohydrate and thermal decomposition of calcium carbonate, ammonium nitrate and 1,3,5,7- tetranitro-1,3,5,7-tetrazocine.

Modeling of Chemical Reactions in Afterburning for the Reduction of N2O

DEFF Research Database (Denmark)

Gustavsson, Lennart; Glarborg, Peter; Leckner, Bo

1996-01-01

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

Model for transport and reaction of defects and carriers within displacement cascades in gallium arsenide

International Nuclear Information System (INIS)

Wampler, William R.; Myers, Samuel M.

2015-01-01

A model is presented for recombination of charge carriers at evolving displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with the details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers, and defects within a representative spherically symmetric cluster of defects. The initial radial defect profiles within the cluster were determined through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to displacement damage from energetic particle irradiation

Phenomenological theory of current-producing processes at the solid oxide electrolyte/gas electrode interface: steady-state polarization of fuel-cell electrodes

International Nuclear Information System (INIS)

Murygin, I.V.; Chebotin, V.N.

1979-01-01

The polarization of fuel-cell electrodes (mixtures CO + CO 2 and H 2 + H 2 O) in systems with solid oxide electrolytes is discussed. The theory is based upon a process model where the electrode reaction zone can spread along the line of three-phase contact by diffusion of reaction partners and products across the electrolyte/electrode and electrolyte/gas interface

Hydrodesulphurization of Light Gas Oil using hydrogen from the Water Gas Shift Reaction

Science.gov (United States)

Alghamdi, Abdulaziz

2009-12-01

The production of clean fuel faces the challenges of high production cost and complying with stricter environmental regulations. In this research, the ability of using a novel technology of upgrading heavy oil to treat Light Gas Oil (LGO) will be investigated. The target of this project is to produce cleaner transportation fuel with much lower cost of production. Recently, a novel process for upgrading of heavy oil has been developed at University of Waterloo. It is combining the two essential processes in bitumen upgrading; emulsion breaking and hydroprocessing into one process. The water in the emulsion is used to generate in situ hydrogen from the Water Gas Shift Reaction (WGSR). This hydrogen can be used for the hydrogenation and hydrotreating reaction which includes sulfur removal instead of the expensive molecular hydrogen. This process can be carried out for the upgrading of the bitumen emulsion which would improve its quality. In this study, the hydrodesulphurization (HDS) of LGO was conducted using in situ hydrogen produced via the Water Gas Shift Reaction (WGSR). The main objective of this experimental study is to evaluate the possibility of producing clean LGO over dispersed molybdenum sulphide catalyst and to evaluate the effect of different promoters and syn-gas on the activity of the dispersed Mo catalyst. Experiments were carried out in a 300 ml Autoclave batch reactor under 600 psi (initially) at 391°C for 1 to 3 hours and different amounts of water. After the hydrotreating reaction, the gas samples were collected and the conversion of carbon monoxide to hydrogen via WGSR was determined using a refinery gas analyzer. The sulphur content in liquid sample was analyzed via X-Ray Fluorescence. Experimental results showed that using more water will enhance WGSR but at the same time inhibits the HDS reaction. It was also shown that the amount of sulfur removed depends on the reaction time. The plan is to investigate the effect of synthesis gas (syngas

The effect of interfaces on solid-state reactions between oxides

International Nuclear Information System (INIS)

Johnson, M.T.; Carter, C.B.

1998-01-01

A thin-film geometry has been used to study fundamental solid-state reaction processes occurring at interfaces in two spinel-forming oxide systems. In the first system, NiO/Al 2 O 3 , epitactic NiO films were deposited on various orientations of single-crystal α-Al 2 O 3 . In this case, the reaction kinetics were studied and correlated with the interfacial structure (or substrate orientation). In the second, In 2 O 3 /MgO, solid-state reactions were studied under the influence of an electric field. The electric field provides a driving force for mass transport that affects both the reaction process and the morphological stability of an interface

Slurried solid media for simultaneous water purification and carbon dioxide removal from gas mixtures

Science.gov (United States)

Aines, Roger D.; Bourcier, William L.; Viani, Brian

2013-01-29

A slurried solid media for simultaneous water purification and carbon dioxide removal from gas mixtures includes the steps of dissolving the gas mixture and carbon dioxide in water providing a gas, carbon dioxide, water mixture; adding a porous solid media to the gas, carbon dioxide, water mixture forming a slurry of gas, carbon dioxide, water, and porous solid media; heating the slurry of gas, carbon dioxide, water, and porous solid media producing steam; and cooling the steam to produce purified water and carbon dioxide.

Gold nanoparticle enhanced fluorescence anisotropy for the assay of single nucleotide polymorphisms (SNPs) based on toehold-mediated strand-displacement reaction.

Science.gov (United States)

Wang, Xinyi; Zou, Mingjian; Huang, Hongduan; Ren, Yuqian; Li, Limei; Yang, Xiaoda; Li, Na

2013-03-15

We developed a highly differentiating, homogeneous gold nanoparticle (AuNP) enhanced fluorescence anisotropic method for single nucleotide polymorphism (SNP) detection at nanomolar level using toehold-mediated strand-displacement reaction. The template strand, containing a toehold domain with an allele-specific site, was immobilized on the surface of AuNPs, and the solution fluorescence anisotropy was markedly enhanced when the fluorescein-labeled blocking DNA was attached to the AuNP via hybridization. Strand-displacement by the target ssDNA strand resulted in detachment of fluorescein-labeled DNA from AuNPs, and thus decreased fluorescence anisotropy. The drastic kinetic difference in strand-displacement from toehold design was used to distinguish between the perfectly matched and the single-base mismatched strands. Free energy changes were calculated to elucidate the dependence of the differentiation ability on the mutation site in the toehold region. A solid negative signal change can be obtained for single-base mismatched strand in the dynamic range of the calibration curve, and a more than 10-fold signal difference can still be observed in a mixed solution containing 100 times the single-base mismatched strand, indicating the good specificity of the method. This proposed method can be performed with a standard spectrofluorimeter in a homogeneous and cost-effective manner, and has the potential to be extended to the application of fluorescence anisotropy method of SNP detection. Copyright © 2012 Elsevier B.V. All rights reserved.

Selected Topics on Mass Transport in Gas-solid Interactions

DEFF Research Database (Denmark)

Somers, Marcel A.J.

2004-01-01

The present article is a short review containing examples of the role of mass transport in the solid state during gas-solid interactions. Examples are taken from the authors' research on the interaction of carbon and/or nitrogen with iron-based metals. Topics dealt with are diffusion-controlled d......The present article is a short review containing examples of the role of mass transport in the solid state during gas-solid interactions. Examples are taken from the authors' research on the interaction of carbon and/or nitrogen with iron-based metals. Topics dealt with are diffusion...... on the kinetics of phenomena in the solid state. Various experimental techniques were applied to investigate these phenomena; it is however beyond the scope of the present article to treat experimental conditions in detail. The interested reader is referred to the original work for in depth discussions...

Visualizing Gas Adsorption on Porous Solids: Four Simple, Effective Demonstrations

Science.gov (United States)

Cheung, Ocean

2014-01-01

Gas adsorption on porous solids is a topic that is often discussed in an undergraduate chemistry or chemical engineering course. The idea of porosity and gas adsorption on a porous solid is usually discussed with adsorption isotherms recorded using commercially available equipment. This discussion can be rather abstract and can be difficult for…

Chemical degradation of proteins in the solid state with a focus on photochemical reactions.

Science.gov (United States)

Mozziconacci, Olivier; Schöneich, Christian

2015-10-01

Protein pharmaceuticals comprise an increasing fraction of marketed products but the limited solution stability of proteins requires considerable research effort to prepare stable formulations. An alternative is solid formulation, as proteins in the solid state are thermodynamically less susceptible to degradation. Nevertheless, within the time of storage a large panel of kinetically controlled degradation reactions can occur such as, e.g., hydrolysis reactions, the formation of diketopiperazine, condensation and aggregation reactions. These mechanisms of degradation in protein solids are relatively well covered by the literature. Considerably less is known about oxidative and photochemical reactions of solid proteins. This review will provide an overview over photolytic and non-photolytic degradation reactions, and specially emphasize mechanistic details on how solid structure may affect the interaction of protein solids with light. Copyright © 2014 Elsevier B.V. All rights reserved.

Investigation of Gas Solid Fluidized Bed Dynamics with Non-Spherical Particles

Energy Technology Data Exchange (ETDEWEB)

Choudhuri, Ahsan [Univ. of Texas, El Paso, TX (United States). Dept. of Mechanical Engineering

2013-06-30

One of the largest challenges for 21st century is to fulfill global energy demand while also reducing detrimental impacts of energy generation and use on the environment. Gasification is a promising technology to meet the requirement of reduced emissions without compromising performance. Coal gasification is not an incinerating process; rather than burning coal completely a partial combustion takes place in the presence of steam and limited amounts of oxygen. In this controlled environment, a chemical reaction takes place to produce a mixture of clean synthetic gas. Gas-solid fluidized bed is one such type of gasification technology. During gasification, the mixing behavior of solid (coal) and gas and their flow patterns can be very complicated to understand. Many attempts have taken place in laboratory scale to understand bed hydrodynamics with spherical particles though in actual applications with coal, the particles are non-spherical. This issue drove the documented attempt presented here to investigate fluidized bed behavior using different ranges of non-spherical particles, as well as spherical. For this investigation, various parameters are controlled that included particle size, bed height, bed diameter and particle shape. Particles ranged from 355 µm to 1180 µm, bed diameter varied from 2 cm to 7 cm, two fluidized beds with diameters of 3.4 cm and 12.4 cm, for the spherical and non-spherical shaped particles that were taken into consideration. Pressure drop was measured with increasing superficial gas velocity. The velocity required in order to start to fluidize the particle is called the minimum fluidization velocity, which is one of the most important parameters to design and optimize within a gas-solid fluidized bed. This minimum fluidization velocity was monitored during investigation while observing variables factors and their effect on this velocity. From our investigation, it has been found that minimum fluidization velocity is independent of bed

Solid Organic Deposition During Gas Injection Studies

DEFF Research Database (Denmark)

Dandekar, Abhijit Y.; Andersen, Simon Ivar; Stenby, Erling Halfdan

2000-01-01

Recently a series of first contact miscibility (swelling) experiments have been performed on undersaturated light and heavy oils using LPG rich and methane rich injection gases, in which solid organic deposition was observed. A compositional gradient in the oils during the gas injection process....... The asphaltene content of the different oil samples were determined by the TP 143 method. The standard asphaltenes and the solid organic deposit recovered from the swelling tests were analyzed using FTIR, HPLC-SEC and H-1 NMR. The aim of these analyses is to reveal the molecular nature of the deposits formed...... during the gas injection process in comparison with the standard asphaltenes in order to understand the mechanisms involved in asphaltene deposition....

New developments on Monte Carlo simulation code for the calculation of Atom Displacements Induced rates by High Energy Electrons in Solid Materials

International Nuclear Information System (INIS)

Damiani, Daniela D.; Cruz, Carlos M.; Pinnera, Ibrahin; Abreu, Yamiel; Leyva, Antonio

2015-01-01

New developments and simulations on regard to the interactions of incident gamma radiation over solids materials using the MCSAD (Monte Carlo Simulation of Atom Displacement) code are presented. In this code Monte Carlo algorithms are applied in order to sample all electrons and gamma interaction processes occurring during their transport through a solid target, especially those connected to the output of atom displacements events. Particularly, it is calculated the limit angle to elastic scattering for the electrons on a new approach, which allows correctly the splitting of the electron single processes at higher scattering angles. On this way, the probability of single electron scattering processes transferring high recoil atomic energy leading to atom displacement effects is calculated and consequently sampled in the MCSAD code. In addition, it is considered some other new theoretical aspects in order to improve previous versions, like the one concerning the selection of threshold energy for displacements at a given atom site in dependence of the atom recoil direction. (Author)

The Influence of Mixing in High Temperature Gas Phase Reactions

DEFF Research Database (Denmark)

Østberg, Martin

1996-01-01

by injection of NH3 with carrier gas into the flue gas. NH3 can react with NO and form N2, but a competing reaction path is the oxidation of NH3 to NO.The SNR process is briefly described and it is shown by chemical kinetic modelling that OH radicals under the present conditions will initiate the reaction......The objective of this thesis is to describe the mixing in high temperature gas phase reactions.The Selective Non-Catalytic Reduction of NOx (referred as the SNR process) using NH3 as reductant was chosen as reaction system. This in-furnace denitrification process is made at around 1200 - 1300 K...... diffusion. The SNR process is simulated using the mixing model and an empirical kinetic model based on laboratory experiments.A bench scale reactor set-up has been built using a natural gas burner to provide the main reaction gas. The set-up has been used to perform an experimental investigation...

Displacement of an electric arc by a stationary transverse magnetic field to different pressures of the ionized gas

International Nuclear Information System (INIS)

Ramos, J.

1987-01-01

The displacement of a wall-stabilized electric arc by a stationary transverse magnetic field is measured to different pressures of the ionized gas. The increase of the pressure makes the heat transfer function and the mass flow velocity in the arc column to raise, and it makes the arc displacement to decrease. (author)

Study of gas-solid contact in an ultra-rapid reactor for cumene catalytic cracking; Etude du contact gaz-solide dans un reacteur a co-courant descendant par la mise en oeuvre du craquage catalytique du cumene

Energy Technology Data Exchange (ETDEWEB)

Bayle, J

1996-11-05

Few studies have been carried out on the notion of gas-solid contact in ultra-rapid reactors. Both gas and solid move in the reactor and the contact can be directly estimated when using a chemical reaction such as cumene cracking. It`s a pure and light feedstock whose kinetics can be determined in a fixed bed. The study was carried out on a downflow ultra-rapid reactor (ID = 20 mm, length = 1 m) at the University of Western Ontario. It proved that the quench and the ultra-rapid separation of gas and solid must be carefully designed in the pilot plant. Cumene conversion dropped when reducing gas-solid contact, which led to push the temperature over 550 deg. C and increase the cat/oil ratio at 25 working at solid mass fluxes below 85 kg/m{sup 2}.s. Change of selectivity at very short residence time were also observed due to deactivation effects. Experiments made by Roques (1994) with phosphorescent pigments on the Residence Time Distribution of solids gave Hydrodynamic data on a cold flow copy of the pilot plant. Experiments made on packed bed gave kinetic data on the cracking of cumene. These data were combined to optimize a mono dimensional plug flow model for cumene cracking. (author)

Energy-filtered environmental transmission electron microscopy for the assessment of solid–gas reactions at elevated temperature: NiO/YSZ–H{sub 2} as a case study

Energy Technology Data Exchange (ETDEWEB)

Jeangros, Q. [Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland); Photovoltaics and Thin Film Electronics Laboratory, Ecole Polytechnique Fédérale de Lausanne, Neuchâtel (Switzerland); Hansen, T.W.; Wagner, J.B. [Center for Electron Nanoscopy, Technical University of Denmark, Lyngby (Denmark); Dunin-Borkowski, R.E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Jülich Research Centre, Jülich (Germany); Hébert, C. [Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland); Van herle, J. [Fuelmat Group, Ecole Polytechnique Fédérale de Lausanne, Sion (Switzerland); Hessler-Wyser, A. [Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland); Photovoltaics and Thin Film Electronics Laboratory, Ecole Polytechnique Fédérale de Lausanne, Neuchâtel (Switzerland)

2016-10-15

A novel approach, which is based on the analysis of sequences of images recorded using energy-filtered transmission electron microscopy and can be used to assess the reaction of a solid with a gas at elevated temperature, is illustrated for the reduction of a NiO/ceramic solid oxide fuel cell anode in 1.3 mbar of H{sub 2}. Three-window elemental maps and jump-ratio images of the O K edge and total inelastic mean free path images are recorded as a function of temperature and used to provide local and quantitative information about the reaction kinetics and the volume changes that result from the reaction. Under certain assumptions, the speed of progression of the reaction front in all three dimensions is obtained, thereby providing a three-dimensional understanding of the reaction. - Highlights: • EFTEM is used to assess solid–gas reactions at elevated temperatures. • This novel approach provides local, quantitative chemical and structural data. • A 3D insight into how the reaction proceeds is obtained under certain assumptions. • Reaction mechanisms and their link to microstructure can be established.

Highly sensitive chemiluminescent point mutation detection by circular strand-displacement amplification reaction.

Science.gov (United States)

Shi, Chao; Ge, Yujie; Gu, Hongxi; Ma, Cuiping

2011-08-15

Single nucleotide polymorphism (SNP) genotyping is attracting extensive attentions owing to its direct connections with human diseases including cancers. Here, we have developed a highly sensitive chemiluminescence biosensor based on circular strand-displacement amplification and the separation by magnetic beads reducing the background signal for point mutation detection at room temperature. This method took advantage of both the T4 DNA ligase recognizing single-base mismatch with high selectivity and the strand-displacement reaction of polymerase to perform signal amplification. The detection limit of this method was 1.3 × 10(-16)M, which showed better sensitivity than that of most of those reported detection methods of SNP. Additionally, the magnetic beads as carrier of immobility was not only to reduce the background signal, but also may have potential apply in high through-put screening of SNP detection in human genome. Copyright © 2011 Elsevier B.V. All rights reserved.

Modelling Toehold-Mediated RNA Strand Displacement

OpenAIRE

Šulc, Petr; Ouldridge, Thomas E.; Romano, Flavio; Doye, Jonathan P.K.; Louis, Ard A.

2015-01-01

We study the thermodynamics and kinetics of an RNA toehold-mediated strand displacement reaction with a recently developed coarse-grained model of RNA. Strand displacement, during which a single strand displaces a different strand previously bound to a complementary substrate strand, is an essential mechanism in active nucleic acid nanotechnology and has also been hypothesized to occur in vivo. We study the rate of displacement reactions as a function of the length of the toehold and temperat...

Method for improved gas-solids separation

Science.gov (United States)

Kusik, C.L.; He, B.X.

1990-11-13

Methods are disclosed for the removal of particulate solids from a gas stream at high separation efficiency, including the removal of submicron size particles. The apparatus includes a cyclone separator type of device which contains an axially mounted perforated cylindrical hollow rotor. The rotor is rotated at high velocity in the same direction as the flow of an input particle-laden gas stream to thereby cause enhanced separation of particulate matter from the gas stream in the cylindrical annular space between the rotor and the sidewall of the cyclone vessel. Substantially particle-free gas passes through the perforated surface of the spinning rotor and into the hollow rotor, from where it is discharged out of the top of the apparatus. Separated particulates are removed from the bottom of the vessel. 4 figs.

Overcoming Short-Circuit in Lead-Free CH3NH3SnI3 Perovskite Solar Cells via Kinetically Controlled Gas-Solid Reaction Film Fabrication Process.

Science.gov (United States)

Yokoyama, Takamichi; Cao, Duyen H; Stoumpos, Constantinos C; Song, Tze-Bin; Sato, Yoshiharu; Aramaki, Shinji; Kanatzidis, Mercouri G

2016-03-03

The development of Sn-based perovskite solar cells has been challenging because devices often show short-circuit behavior due to poor morphologies and undesired electrical properties of the thin films. A low-temperature vapor-assisted solution process (LT-VASP) has been employed as a novel kinetically controlled gas-solid reaction film fabrication method to prepare lead-free CH3NH3SnI3 thin films. We show that the solid SnI2 substrate temperature is the key parameter in achieving perovskite films with high surface coverage and excellent uniformity. The resulting high-quality CH3NH3SnI3 films allow the successful fabrication of solar cells with drastically improved reproducibility, reaching an efficiency of 1.86%. Furthermore, our Kelvin probe studies show the VASP films have a doping level lower than that of films prepared from the conventional one-step method, effectively lowering the film conductivity. Above all, with (LT)-VASP, the short-circuit behavior often obtained from the conventional one-step-fabricated Sn-based perovskite devices has been overcome. This study facilitates the path to more successful Sn-perovskite photovoltaic research.

The injection of inert gas ions into solids: their trapping and escape

International Nuclear Information System (INIS)

Carter, G.; Armour, D.G.; Donnelly, S.E.; Ingram, D.C.; Webb, R.P.

1980-01-01

Basic information is required to understand fission gas generation and its consequence for swelling and embrittlement in fission reactors, for understanding and controlling first wall problems in fusion reactors and for attempting to design storage for active gas waste. In all of these areas the rare gas atoms are generated with kinetic energy and may thus interact differently, during their slowing down, with the solid than if they had been introduced more gently (e.g. via diffusion) into the solid. An important method of simulating the behaviour of such energetic rare gas atoms in solids is via external irradiation of the solid with rare gas ions of appropriate species and energies and it is the purpose of this review to evaluate studies of this nature. The review is divided into three parts. The first describes experimental techniques, discusses the results of measurements of how ions penetrate into and may be retained in a solid, and outlines theoretical interpretations of the data. The mechanisms of gas atom dissolution and thermal transport in solids are of profound importance and so, in the second part of this review, attention is devoted to how the technique of post-implantation thermal evolution spectrometry can be employed to attempt to understand some of these processes. Particular attention is paid to the difficulties of unique interpretation of evolution spectra. In the final section, consideration will be given to the processes which lead to the inevitable saturation of solids undergoing continued irradiation with rare gas ions and experimental measurements and their probable interpretation will be discussed. Since many materials are of importance in the context of this symposium, reference will be made to as broad a range of studies as possible. (author)

Experimental and modeling study of high performance direct carbon solid oxide fuel cell with in situ catalytic steam-carbon gasification reaction

Science.gov (United States)

Xu, Haoran; Chen, Bin; Zhang, Houcheng; Tan, Peng; Yang, Guangming; Irvine, John T. S.; Ni, Meng

2018-04-01

In this paper, 2D models for direct carbon solid oxide fuel cells (DC-SOFCs) with in situ catalytic steam-carbon gasification reaction are developed. The simulation results are found to be in good agreement with experimental data. The performance of DC-SOFCs with and without catalyst are compared at different operating potential, anode inlet gas flow rate and operating temperature. It is found that adding suitable catalyst can significantly speed up the in situ steam-carbon gasification reaction and improve the performance of DC-SOFC with H2O as gasification agent. The potential of syngas and electricity co-generation from the fuel cell is also evaluated, where the composition of H2 and CO in syngas can be adjusted by controlling the anode inlet gas flow rate. In addition, the performance DC-SOFCs and the percentage of fuel in the outlet gas are both increased with increasing operating temperature. At a reduced temperature (below 800 °C), good performance of DC-SOFC can still be obtained with in-situ catalytic carbon gasification by steam. The results of this study form a solid foundation to understand the important effect of catalyst and related operating conditions on H2O-assisted DC-SOFCs.

Size Controlled Synthesis of Tellurium Nanorices by Galvanic Displacement Reaction of Aluminum

International Nuclear Information System (INIS)

Wu, Tingjun; Myung, Lawrence Youngjae; Zhang, Miluo; Lee, Kyu-Hwan; Lee, Yeheun Laura; Lim, Hyo-Ryong; Kim, Bum Sung; Choa, Yong-Ho; Myung, Nosang V.

2015-01-01

ABSTRACT: Tellurium nanostructures were synthesized by galvanic displacement reaction (GDR) of aluminum in an alkaline solution containing TeO 3 2− ions. Due to negative redox potential of Al/AlO 2 − (i.e., −2.50 V vs. sat. Ag/AgCl), TeO 3 2− (+IV) can be reduced to Te 2 2− (-I) and Te 2− (-II), which resulted in the deposition of Te (0) nanostructures in the solution via chemical reaction between Te 2 2− or Te 2− and TeO 3 2− . The deposition mechanism led to the formation of unique “rice-like” nanostructures in the solution instead of branched structures on the substrate. The sharp tips of the “rice-like” nanostructures may be attributed to the high density of surface charges at the tips. The morphology, diameter and aspect ratio of Te “rice-like” nanostructures were altered by the TeO 3 2− concentration, solution pH, reaction time and the reaction temperature. Electrochemical analytical methods, including open circuit potential (OCP) and linear polarizations (LPs), were used to investigate the reaction mechanisms. The enhancement of piezoelectric constant (d 11 ) of nanorices at small diameter was probably due to a flexoelectric effect

In-situ study of the gas-phase composition and temperature of an intermediate-temperature solid oxide fuel cell anode surface fed by reformate natural gas

Science.gov (United States)

Santoni, F.; Silva Mosqueda, D. M.; Pumiglia, D.; Viceconti, E.; Conti, B.; Boigues Muñoz, C.; Bosio, B.; Ulgiati, S.; McPhail, S. J.

2017-12-01

An innovative experimental setup is used for in-depth and in-operando characterization of solid oxide fuel cell anodic processes. This work focuses on the heterogeneous reactions taking place on a 121 cm2 anode-supported cell (ASC) running with a H2, CH4, CO2, CO and steam gas mixture as a fuel, using an operating temperature of 923 K. The results have been obtained by analyzing the gas composition and temperature profiles along the anode surface in different conditions: open circuit voltage (OCV) and under two different current densities, 165 mA cm-2 and 330 mA cm-2, corresponding to 27% and 54% of fuel utilization, respectively. The gas composition and temperature analysis results are consistent, allowing to monitor the evolution of the principal chemical and electrochemical reactions along the anode surface. A possible competition between CO2 and H2O in methane internal reforming is shown under OCV condition and low current density values, leading to two different types of methane reforming: Steam Reforming and Dry Reforming. Under a current load of 40 A, the dominance of exothermic reactions leads to a more marked increase of temperature in the portion of the cell close to the inlet revealing that current density is not uniform along the anode surface.

Zeolite Membrane Reactor for Water Gas Shift Reaction for Hydrogen Production

Energy Technology Data Exchange (ETDEWEB)

Lin, Jerry Y.S. [Arizona State Univ., Mesa, AZ (United States)

2013-01-29

Gasification of biomass or heavy feedstock to produce hydrogen fuel gas using current technology is costly and energy-intensive. The technology includes water gas shift reaction in two or more reactor stages with inter-cooling to maximize conversion for a given catalyst volume. This project is focused on developing a membrane reactor for efficient conversion of water gas shift reaction to produce a hydrogen stream as a fuel and a carbon dioxide stream suitable for sequestration. The project was focused on synthesizing stable, hydrogen perm-selective MFI zeolite membranes for high temperature hydrogen separation; fabricating tubular MFI zeolite membrane reactor and stable water gas shift catalyst for membrane reactor applications, and identifying experimental conditions for water gas shift reaction in the zeolite membrane reactor that will produce a high purity hydrogen stream. The project has improved understanding of zeolite membrane synthesis, high temperature gas diffusion and separation mechanisms for zeolite membranes, synthesis and properties of sulfur resistant catalysts, fabrication and structure optimization of membrane supports, and fundamentals of coupling reaction with separation in zeolite membrane reactor for water gas shift reaction. Through the fundamental study, the research teams have developed MFI zeolite membranes with good perm-selectivity for hydrogen over carbon dioxide, carbon monoxide and water vapor, and high stability for operation in syngas mixture containing 500 part per million hydrogen sulfide at high temperatures around 500°C. The research teams also developed a sulfur resistant catalyst for water gas shift reaction. Modeling and experimental studies on the zeolite membrane reactor for water gas shift reaction have demonstrated the effective use of the zeolite membrane reactor for production of high purity hydrogen stream.

Bond-selective control of a gas-surface reaction

Science.gov (United States)

Killelea, Daniel R.

The prospect of using light to selectively control chemical reactions has tantalized chemists since the development of the laser. Unfortunately, the realization of laser-directed chemistry is frequently thwarted by the randomization of energy within the molecule through intramolecular vibrational energy distribution (IVR). However, recent results showing vibrational mode-specific reactivity on metal surfaces suggest that IVR may not always be complete for gas-surface reactions. Here, we combine molecular beam techniques and direct laser excitation to characterize the bond-specific reactivity of trideuteromethane on a Ni(111) surface. Our results reveal important details about how vibrational energy is distributed in the reactive molecule. We use a molecular beam to direct state-selected trideuteromethane (CHD 3) molecules onto a nickel single crystal sample and use the results we obtain to describe the flow of vibrational energy in the methane-surface reaction complex. We show that CHD3 molecules initially excited to v=1, J=2, K=0 of the v 1 symmetric C-H stretching mode will dissociate exclusively via C-H cleavage on Ni(111). This result highlights the localization of vibrational energy in the reaction complex, despite the presence of many energy exchange channels with the high state-density surface. We demonstrate, for the first time, highly parallel bond-selective control of a heterogeneously catalyzed reaction. We place our results in the context of recent experiments investigating IVR for molecules in both the gas phase and liquid solutions. If IVR is fast on the reaction timescale, vibrational energy would be randomly distributed throughout the nascent methane-surface reaction complex and vibrational mode-specific behavior would not occur. The short timescale of a direct gas-surface collision may explain how the exchange of energy via IVR is limited to only a small subset of the energetic configurations available to the reaction complex. This framework

A lateral flow biosensor for detection of single nucleotide polymorphism by circular strand displacement reaction.

Science.gov (United States)

Xiao, Zhuo; Lie, Puchang; Fang, Zhiyuan; Yu, Luxin; Chen, Junhua; Liu, Jie; Ge, Chenchen; Zhou, Xuemeng; Zeng, Lingwen

2012-09-04

A lateral flow biosensor for detection of single nucleotide polymorphism based on circular strand displacement reaction (CSDPR) has been developed. Taking advantage of high fidelity of T4 DNA ligase, signal amplification by CSDPR, and the optical properties of gold nanoparticles, this assay has reached a detection limit of 0.01 fM.

Methanol synthesis in a countercurrent gas-solid-solid trickle flow reactor. An experimental study

NARCIS (Netherlands)

Kuczynski, M.; Oyevaar, M.H.; Pieters, R.T.; Westerterp, K.R.

1987-01-01

The synthesis of methanol from CO and H2 was executed in a gas-solid-solid trickle flow reactor. The reactor consisted of three tubular reactor sections with cooling sections in between. The catalyst was Cu on alumina, the adsorbent was a silica-alumina powder and the experimental range 498–523 K,

A miniature CSTR cascade for continuous flow of reactions containing solids

OpenAIRE

Mo, Yiming; Jensen, Klavs F

2016-01-01

Continuous handling of solids creates challenges for realizing continuous production of pharmaceuticals and fine chemicals. We present a new miniature continuous stirred-tank reactor (CSTR) cascade to handle solid-forming reactions in flow. Single-phase residence time distribution (RTD) measurements of the CSTR cascade reveal nearly ideal CSTR mixing behavior of the individual units. Consistency of experimental and predicted conversions of a Diels–Alder reaction further confirms the CSTR perf...

Chemical cleavage reactions of DNA on solid support: application in mutation detection

Directory of Open Access Journals (Sweden)

Cotton Richard GH

2003-05-01

Full Text Available Abstract Background The conventional solution-phase Chemical Cleavage of Mismatch (CCM method is time-consuming, as the protocol requires purification of DNA after each reaction step. This paper describes a new version of CCM to overcome this problem by immobilizing DNA on silica solid supports. Results DNA test samples were loaded on to silica beads and the DNA bound to the solid supports underwent chemical modification reactions with KMnO4 (potassium permanganate and hydroxylamine in 3M TEAC (tetraethylammonium chloride solution. The resulting modified DNA was then simultaneously cleaved by piperidine and removed from the solid supports to afford DNA fragments without the requirement of DNA purification between reaction steps. Conclusions The new solid-phase version of CCM is a fast, cost-effective and sensitive method for detection of mismatches and mutations.

Modelling toehold-mediated RNA strand displacement.

Science.gov (United States)

Šulc, Petr; Ouldridge, Thomas E; Romano, Flavio; Doye, Jonathan P K; Louis, Ard A

2015-03-10

We study the thermodynamics and kinetics of an RNA toehold-mediated strand displacement reaction with a recently developed coarse-grained model of RNA. Strand displacement, during which a single strand displaces a different strand previously bound to a complementary substrate strand, is an essential mechanism in active nucleic acid nanotechnology and has also been hypothesized to occur in vivo. We study the rate of displacement reactions as a function of the length of the toehold and temperature and make two experimentally testable predictions: that the displacement is faster if the toehold is placed at the 5' end of the substrate; and that the displacement slows down with increasing temperature for longer toeholds. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Magnesium hydroxide extracted from a magnesium-rich mineral for CO2 sequestration in a gas-solid system.

Science.gov (United States)

Lin, Pao-Chung; Huang, Cheng-Wei; Hsiao, Ching-Ta; Teng, Hsisheng

2008-04-15

Magnesium hydroxide extracted from magnesium-bearing minerals is considered a promising agent for binding CO2 as a carbonate mineral in a gas-solid reaction. An efficient extraction route consisting of hydrothermal treatment on serpentine in HCl followed by NaOH titration for Mg(OH)2 precipitation was demonstrated. The extracted Mg(OH)2 powder had a mean crystal domain size as small as 12 nm and an apparent surface area of 54 m2/g. Under one atmosphere of 10 vol% CO2/N2, carbonation of the serpentine-derived Mg(OH)2 to 26% of the stoichiometric limit was achieved at 325 degrees C in 2 h; while carbonation of a commercially available Mg(OH)2, with a mean crystal domain size of 33 nm and an apparent surface area of 3.5 m2/g, reached only 9% of the stoichiometric limit. The amount of CO2 fixation was found to be inversely proportional to the crystal domain size of the Mg(OH)2 specimens. The experimental data strongly suggested that only a monolayer of carbonates was formed on the crystal domain boundary in the gas-solid reaction, with little penetration of the carbonates into the crystal domain.

Coefficient of solid-gas heat transfer in particle fixed bed; Coeficiente de transferencia de calor gas-solido em leito fixo de particulas

Energy Technology Data Exchange (ETDEWEB)

Fernandes Filho, Francisco

1991-03-01

The work presents a study on heat transfer between gas and solid phases for fixed beds in the absence of mass transfer and chemical reactions. Mathematical models presented in the literature were analyzed concerning to the assumptions made on axial dispersion in the fluid phase and interparticle thermal conductivity. Heat transfer coefficients and their dependency on flow conditions, particles and packed bed characteristics were experimentally determined through the solution of the previous mathematical models. Pressure drop behaviour for the packed beds used for the heat transfer study was also included. (author) 32 refs., 12 figs.

Thermally activated reaction–diffusion-controlled chemical bulk reactions of gases and solids

Directory of Open Access Journals (Sweden)

S. Möller

2015-01-01

Full Text Available The chemical kinetics of the reaction of thin films with reactive gases is investigated. The removal of thin films using thermally activated solid–gas to gas reactions is a method to in-situ control deposition inventory in vacuum and plasma vessels. Significant scatter of experimental deposit removal rates at apparently similar conditions was observed in the past, highlighting the need for understanding the underlying processes. A model based on the presence of reactive gas in the films bulk and chemical kinetics is presented. The model describes the diffusion of reactive gas into the film and its chemical interaction with film constituents in the bulk using a stationary reaction–diffusion equation. This yields the reactive gas concentration and reaction rates. Diffusion and reaction rate limitations are depicted in parameter studies. Comparison with literature data on tokamak co-deposit removal results in good agreement of removal rates as a function of pressure, film thickness and temperature.

Mass transfer with chemical reaction in multiphase systems

International Nuclear Information System (INIS)

Alper, E.

1983-01-01

These volumes deal with the phenomenon of 'mass transfer with chemical reaction' which is of industrial, biological and physiological importance. In process engineering, it is encountered both in separation processes and in reaction engineering and both aspects are covered here in four sections: introduction; gas-liquid system; liquid-liquid system; and gas-liquid-solid system

Simulation of granular and gas-solid flows using discrete element method

Science.gov (United States)

Boyalakuntla, Dhanunjay S.

2003-10-01

In recent years there has been increased research activity in the experimental and numerical study of gas-solid flows. Flows of this type have numerous applications in the energy, pharmaceuticals, and chemicals process industries. Typical applications include pulverized coal combustion, flow and heat transfer in bubbling and circulating fluidized beds, hopper and chute flows, pneumatic transport of pharmaceutical powders and pellets, and many more. The present work addresses the study of gas-solid flows using computational fluid dynamics (CFD) techniques and discrete element simulation methods (DES) combined. Many previous studies of coupled gas-solid flows have been performed assuming the solid phase as a continuum with averaged properties and treating the gas-solid flow as constituting of interpenetrating continua. Instead, in the present work, the gas phase flow is simulated using continuum theory and the solid phase flow is simulated using DES. DES treats each solid particle individually, thus accounting for its dynamics due to particle-particle interactions, particle-wall interactions as well as fluid drag and buoyancy. The present work involves developing efficient DES methods for dense granular flow and coupling this simulation to continuum simulations of the gas phase flow. Simulations have been performed to observe pure granular behavior in vibrating beds. Benchmark cases have been simulated and the results obtained match the published literature. The dimensionless acceleration amplitude and the bed height are the parameters governing bed behavior. Various interesting behaviors such as heaping, round and cusp surface standing waves, as well as kinks, have been observed for different values of the acceleration amplitude for a given bed height. Furthermore, binary granular mixtures (granular mixtures with two particle sizes) in a vibrated bed have also been studied. Gas-solid flow simulations have been performed to study fluidized beds. Benchmark 2D

Growth of binary solid solution single crystals and calculation of melt surface displacement velocity

International Nuclear Information System (INIS)

Agamaliyev, Z.A.; Tahirov, V.I.; Hasanov, Z.Y.; Quliyev, A.F.

2007-01-01

A binary solid solution single crystal growth method has been worked out. Cylinder feeding alloy with complex content distribution and truncated cone crucible are used. Second component distribution coefficient is more than unit. Content distribution along grown crystal is found by solving continuity equation. After reaching dynamic equilibrium state second component concentration in grown crystal is saturated the value of which is less than the average ona in the feeding alloy. Using the method Ge-Si perfect single crystals has been grown. Calculation method of melt surface displacement velocity has been offered as well

Feed gas contaminant removal in ion transport membrane systems

Science.gov (United States)

Carolan, Michael Francis [Allentown, PA; Miller, Christopher Francis [Macungie, PA

2008-09-16

Method for gas purification comprising (a) obtaining a feed gas stream containing one or more contaminants selected from the group consisting of volatile metal oxy-hydroxides, volatile metal oxides, and volatile silicon hydroxide; (b) contacting the feed gas stream with a reactive solid material in a guard bed and reacting at least a portion of the contaminants with the reactive solid material to form a solid reaction product in the guard bed; and (c) withdrawing from the guard bed a purified gas stream.

Gas chromatographic determination of impurities of inorganic compounds

International Nuclear Information System (INIS)

Drugov, Yu.S.

1985-01-01

Methods of concentration, separation, detection in gas chromatographic determination of impurities of inorganic compounds including low-boiling gases, reactive gases, organometallic compounds, free metals, anions, etc. are reviewed. Methods of reaction gas chromatography for determining reactive gases, water, anions, metal chelates are considered in detail as well as methods of reaction-sorption concentration and reaction gas extraction. The application of gas chromatograpny ior anaiysis of water and atmosphere contamination, for determination of impurities in highly pure solid substances and gases is described

An integration scheme for stiff solid-gas reactor models

Directory of Open Access Journals (Sweden)

Bjarne A. Foss

2001-04-01

Full Text Available Many dynamic models encounter numerical integration problems because of a large span in the dynamic modes. In this paper we develop a numerical integration scheme for systems that include a gas phase, and solid and liquid phases, such as a gas-solid reactor. The method is based on neglecting fast dynamic modes and exploiting the structure of the algebraic equations. The integration method is suitable for a large class of industrially relevant systems. The methodology has proven remarkably efficient. It has in practice performed excellent and been a key factor for the success of the industrial simulator for electrochemical furnaces for ferro-alloy production.

Through-furnace for burning solid organic substances

International Nuclear Information System (INIS)

Kemmler, G.; Schlich, E.

1984-01-01

The through-furnace for burning radio-active organic solid waste consists of a reaction pipe heated from the outside, an input device and an output device. A solid pump is used as the input device, which has a common longitudinal axis with the reaction pipe. The reaction pipe is widened in the transport direction of the combustion pipe, where the angle between the longitudinal axis and the pipe wall is 0.5 to 5 0 . The pipe wall is wholely or partially permeable to gas. The thermal treatment of the solid organic substances can occur by combustion or by pyrohydrolysis or pyrolysis in the through-furnace. (orig./HP) [de

Pneumatic tool torque reaction: reaction forces, displacement, muscle activity and discomfort in the hand-arm system.

Science.gov (United States)

Kihlberg, S; Kjellberg, A; Lindbeck, L

1993-06-01

Reaction forces, hand-arm displacement, muscle activity and discomfort ratings were studied during the securing of threaded fasteners with three angle nutrunners with different shut-off mechanisms, but with the same spindle torque (72-74 Nm). The three tools were tested according to the method specified in ISO 6544. One of the tools had an almost instantaneous shut-off. Another had a more slowly declining torque curve. For the third tool the maximum torque was maintained for a while before shut-off. Twelve male subjects participated in the study. A force platform measured the reaction force between the subject and the floor. The option of the hand-arm system and the shoulder was measured with an optoelectronic measuring system. The muscle activity (EMG) in six muscles in the arm and shoulder was measured with surface electrodes. Significant differences in the arm movements and ground reaction forces were found between the three tools. The smallest values were found with the fast shut-off tool while the delayed shut-off tool caused the largest values. The EMG measures gave inconsistent response patterns. Discomfort ratings were highly correlated with the time for which the tool torque exceeded 90% of peak preset torque, but the time for which the tool torque exceeded 90% of peak calculated by the method specified in ISO 6544. Nutrunners with a shut-off mechanism that causes a slowly decreasing torque or a torque that is maintained for a while before shut-off should be avoided. If no substitutes are available, then a torque reaction bar should be mounted on the tool.

Calculation of displacement, gas, and transmutation production in stainless steel irradiated with spallation neutrons

International Nuclear Information System (INIS)

Wechsler, M.A.; Ramavarapu, R.; Daugherty, E.L.; Palmer, R.C.; Bullen, D.B.; Sommer, W.F.

1993-01-01

Calculations using the high-energy transport code LAHET have been made for the production of displacements, helium gas, and transmuted atoms for stainless steel (Fe-18 wt % Cr-10 wt % Ni) irradiated with spallation neutrons at energies of 100 to 1600 MeV. The damage energy cross section increased from about 250 to 350 b keV for increasing neutron energies from 100 to 1600 MeV with a spallation spectrum average of 281 barns-keV. For a displacement threshold energy of 33 eV, the corresponding spectrum-average displacement cross section is 3400 barns. The PKA spectrum was found to be fairly independent of the incident neutron energy, with an average damage energy of 0.25--0.30 MeV. The helium production cross section increased monotonically with increasing neutron energy, with a spectrum average of 0.32 barns. The maximum transmutation yield was observed near manganese (Z = 25), corresponding to a production cross section of about 0.2 barns. Relevance to fusion materials is discussed

Solid-phase vibrational redox reactions in coordinated oxides

International Nuclear Information System (INIS)

Kostikova, G.P.; Korol'kov, D.V.; Kostikov, Yu.P.

1996-01-01

The properties of multicomponent oxides (YBa 2 Cu 3 O 7-x , etc.), incorporating different valency forms of each of two (or more) different elements have been compared with the properties of the known chemical systems, where vibrational (periodic) redox-reactions are realized a fortiori. The essence of the new theoretical concept suggested consists in the following: high-T c superconductivity of the complex oxides and similar compounds originates from vibrational redox reaction proceeding in solid phase and involving different valency atoms of every element

Ambient Mechanochemical Solid-State Reactions of Carbon Nanotubes and Their Reactions via Covalent Coordinate Bond in Solution

Science.gov (United States)

Kabbani, Mohamad A.

In its first part, this thesis deals with ambient mechanochemical solid-state reactions of differently functionalized multiple walled carbon nanotubes (MWCNTs) while in its second part it investigates the cross-linking reactions of CNTs in solution via covalent coordinate bonds with transitions metals and carboxylate groups decorating their surfaces. In the first part a series of mechanochemical reactions involving different reactive functionalities on the CNTs such as COOH/OH, COOH/NH2 and COCl/OH were performed. The solid-state unzipping of CNTs leading to graphene formation was confirmed using spectroscopic, thermal and electron microscopy techniques. The non-grapheme products were established using in-situ quadruple mass spectroscopy. The experimental results were confirmed by theoretical simulation calculations using the 'hot spots' protocol. The kinetics of the reaction between MWCNT-COOH and MWCNT-OH was monitored using variable temperature Raman spectroscopy. The low activation energy was discussed in terms of hydrogen bond mediated proton transfer mechanism. The second part involves the reaction of MWCNTII COOH with Zn (II) and Cu (II) to form CNT metal-organic frame (MOFs) products that were tested for their effective use as counter-electrodes in dyes sensitized solar cells (DSSC). The thesis concludes by the study of the room temperature reaction between the functionalized graphenes, GOH and G'-COOH followed by the application of compressive loads. The 3D solid graphene pellet product ( 0.6gm/cc) is conductive and reflective with a 35MPa ultimate strength as compared to 10MPa strength of graphite electrode ( 2.2gm/cc).

Formation of fine aggregate structure by solid-state displacement reaction of Ti with CoO or NiO. CoO oyobi NiO to Ti kan no koso chikan hanno ni yoru bisai fukugo soshiki no seisei

Energy Technology Data Exchange (ETDEWEB)

Taimatsu, H; Kaneko, H [Akita Univ., Akita (Japan). Mining College; Wada, K [Akita Univ., Akita (Japan). Graduate School

1992-09-20

As a result of search for systems which have aggregate structures, the displacement reaction products of Ti with CoO or NiO are found to have aggregate structures in which the produced oxides and metals are entangled with each other. The displacement reaction of Ti with CoO or NiO is investigated at the temperature of 1273K. In the reaction of either couple, aggregate products are produced, and reacted layer is observed in the TiO2 matrix wherein Co or Ni phases are three dimensionally entangled in finely dispersed state of micron order. 2 layers of cavitated and dense TiO2 layers are found in the reacted layer. The thicknesses of the reacted layer are not constant according to locations, but thick portions are grown obeying the parabolic rate law. As a result of the study on the possibility of fabricating cermet by the reaction between powders, finely mixed characteristic structures are found to be easily obtained using systems which can produce aggregate structures. 24 refs., 9 figs.

Thermodynamics of gas adsorption on solid adsorbents

International Nuclear Information System (INIS)

Budrugeac, P.

1979-01-01

Starting with several hypotheses about the adsorbtion system and the adsorption phenomenon, a thermodynamic treatment of gas adsorption on solid adsorbants is presented. The relationships for determination from isotherms and calorimetric data of thermodynamic functions are derived. The problem of the phase changes in adsorbed layer is discussed. (author)

Numerical simulation of coupled binary gas-solid interaction during carbon dioxide sequestration in a coal bed

International Nuclear Information System (INIS)

Feng Qiyan; Zhou Lai; Chen Zhongwei; Liu Jishan

2008-01-01

Complicated coupled binary gas-solid interaction arises during carbon dioxide sequestration in a coal seam, which combines effects of CO 2 -CH 4 counter adsorption, CO 2 -CH 4 counter diffusion, binary gas flow and coal bed deformation. Through solving a set of coupled field governing equations, a novel full coupled Finite Element (FE) model was established by COMSOL Multiphysics. The new FE model was applied to the quantification of coal porous pressure, coal permeability, gas composition fraction and coal displacement when CO 2 was injected in a CH 4 saturated coal bed. Numerical results demonstrate that CH 4 is swept by the injected CO 2 accompanied by coal volumetric deformation. Compared to the single CH 4 in situ, CH 4 -CO 2 counter-diffusion induced coal swelling can make more compensation for coal shrinkage due to effective stress. Competing influences between the effective stress and the CH 4 -CO 2 counter-diffusion induced volume change governs the evolution of porous pressure and permeability, which is controlled by the porous pressure correspondingly. This achievement extends our ability to understand the coupled multi-physics of the CO 2 geological sequestration and CO 2 enhanced coal bed methane recovery under field conditions. (authors)

Possibilities of mercury removal in the dry flue gas cleaning lines of solid waste incineration units.

Science.gov (United States)

Svoboda, Karel; Hartman, Miloslav; Šyc, Michal; Pohořelý, Michael; Kameníková, Petra; Jeremiáš, Michal; Durda, Tomáš

2016-01-15

Dry methods of the flue gas cleaning (for HCl and SO2 removal) are useful particularly in smaller solid waste incineration units. The amount and forms of mercury emissions depend on waste (fuel) composition, content of mercury and chlorine and on the entire process of the flue gas cleaning. In the case of high HCl/total Hg molar ratio in the flue gas, the majority (usually 70-90%) of mercury is present in the form of HgCl2 and a smaller amount in the form of mercury vapors at higher temperatures. Removal of both main forms of mercury from the flue gas is dependent on chemical reactions and sorption processes at the temperatures below approx. 340 °C. Significant part of HgCl2 and a small part of elemental Hg vapors can be adsorbed on fly ash and solid particle in the air pollution control (APC) processes, which are removed in dust filters. Injection of non-impregnated active carbon (AC) or activated lignite coke particles is able to remove mainly the oxidized Hg(2+) compounds. Vapors of metallic Hg(o) are adsorbed relatively weakly. Much better chemisorption of Hg(o) together with higher sorbent capacity is achieved by AC-based sorbents impregnated with sulfur, alkali poly-sulfides, ferric chloride, etc. Inorganic sorbents with the same or similar chemical impregnation are also applicable for deeper Hg(o) removal (over 85%). SCR catalysts convert part of Hg(o) into oxidized compounds (HgO, HgCl2, etc.) contributing to more efficient Hg removal, but excess of NH3 has a negative effect. Both forms, elemental Hg(o) and HgCl2, can be converted into HgS particles by reacting with droplets/aerosol of poly-sulfides solutions/solids in flue gas. Mercury captured in the form of water insoluble HgS is more advantageous in the disposal of solid waste from APC processes. Four selected options of the dry flue gas cleaning with mercury removal are analyzed, assessed and compared (in terms of efficiency of Hg-emission reduction and costs) with wet methods and retrofits for more

In Situ Insight into Reversible O2 Gas-Solid Reactions

DEFF Research Database (Denmark)

Wegeberg, Christina

2016-01-01

Non-porous crystalline solids containing a series of cationic tetracobalt complexes reversibly, selectively and stoichiometrically chemisorb dioxygen in temperature/O2 partial pressure induced processes involving the oxidation of cobalt with concurrent reduction of two equivalents of sorbed O2 to...

Surface-Activated Coupling Reactions Confined on a Surface.

Science.gov (United States)

Dong, Lei; Liu, Pei Nian; Lin, Nian

2015-10-20

Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density

Correlation dimension estimate and its potential use in analysis of gas-solid flows

DEFF Research Database (Denmark)

Yin, Chungen; Rosendahl, Lasse Aistrup; Kær, Søren Knudsen

2005-01-01

Gas-solid flows are nonlinear systems. Therefore state-space analysis, a tool developed within the framework of nonlinear dynamics, could provide more useful insights into complex gas-solid flows. One of the positive aspects of state-space analysis is that the major properties of a system can be ...

Kinetics of the Coupled Gas-Iron Reactions Involving Silicon and ...

African Journals Online (AJOL)

The kinetic study of coupled gas-iron reactions at 15600 has been carried out for the system involving liquid iron containing carbon and silicon and a gas phase consisting carbon monoxide, silicon monoxide and carbon dioxide. The coupled reactions are: (1) 200(g) = CO2 + C. (2) SiO (g) + CO (g) = Si ¸ CO (g). (3) SiO (g) + ...

Rapid estimate of solid volume in large tuff cores using a gas pycnometer

International Nuclear Information System (INIS)

Thies, C.; Geddis, A.M.; Guzman, A.G.

1996-09-01

A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1 degrees C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm 3 with less than 1% error

Acoustic probe for solid-gas-liquid suspensions. 1998 annual progress report

International Nuclear Information System (INIS)

Greenwood, M.S.; Sangani, A.S.; Tavlarides, L.L.

1998-01-01

'The proposed research will develop an acoustic probe for monitoring particle size and volume fraction in slurries in the absence and presence of gas. The goals are to commission and verify the probe components and system operation, develop theory for the forward and inverse problems for acoustic wave propagation through a three phase medium, and experimentally verify the theoretical analysis. The acoustic probe will permit measurement of solid content in gas-liquid-solid waste slurries in tanks across the DOE complex.'

Development of [18F]halofluorination and [18F]fluoride ion displacement reactions for the synthesis of F-18 labelled radiopharmaceuticals

International Nuclear Information System (INIS)

Chi, D.Y.

1986-01-01

Two fluorine-18 labeling methods, [ 18 F]halofluorination and [ 18 F]fluoride ion displacement reactions, have been developed to assess their potential for labeling molecules with the positron-emitting radionuclide fluorine-18 at the no-carrier-added level. Olefin halofluorination involves the in situ generation of a halogen-fluoride reagent and subsequent addition to an olefin. The characteristics of this reaction were investigated with three model olefins (allylbenzene, 1-hexene, and propene). A two-step method for the preparation of fluoroalkyl substituted amines and amides has been achieved. The sequence involves fluoride ion displacement of trifluoromethanesulfonates (triflates) from short-chain haloalkyl triflates, followed by fluoroalkylation of the amine or amide. Alternatively, short-chain fluoroalkyl halides can be prepared by halofluorination of a terminal olefin. These reactions have been used to prepare various fluoroalkyl derivatives of 1-phenylpiperazine and N-fluoroalkyl derivatives of the neuroleptic agent spiperone. A series of fluorine-18 labeled N-fluoroalkylated spiperone derivatives were synthesized by N-alkylation of spiperone with fluoroalkyl halides

Effects of gas periodic stimulation on key enzyme activity in gas double-dynamic solid state fermentation (GDD-SSF).

Science.gov (United States)

Chen, Hongzhang; Shao, Meixue; Li, Hongqiang

2014-03-05

The heat and mass transfer have been proved to be the important factors in air pressure pulsation for cellulase production. However, as process of enzyme secretion, the cellulase formation has not been studied in the view of microorganism metabolism and metabolic key enzyme activity under air pressure pulsation condition. Two fermentation methods in ATPase activity, cellulase productivity, weight lose rate and membrane permeability were systematically compared. Results indicated that gas double-dynamic solid state fermentation had no obviously effect on cell membrane permeability. However, the relation between ATPase activity and weight loss rate was linearly dependent with r=0.9784. Meanwhile, the results also implied that gas periodic stimulation had apparently strengthened microbial metabolism through increasing ATPase activity during gas double-dynamic solid state fermentation, resulting in motivating the production of cellulase by Trichoderma reesei YG3. Therefore, the increase of ATPase activity would be another crucial factor to strengthen fermentation process for cellulase production under gas double-dynamic solid state fermentation. Copyright © 2013 Elsevier Inc. All rights reserved.

Aseismic study of high temperature gas-cooled reactor core with block-type fuel, 3

International Nuclear Information System (INIS)

Ikushima, Takeshi; Honma, Toshiaki.

1985-01-01

A two-dimensional horizontal seismic experiment with single axis and simultaneous two-axes excitations was performed to obtain the core seismic design data on the block-type high temperature gas-cooled reactor. Effects of excitation directions and core side support stiffness on characteristics of core displacements and reaction forces of support were revealed. The values of the side reaction forces are the largest in the excitation of flat-to-flat of hexagonal block. Preload from the core periphery to the core center are effective to decrease core displacements and side reaction forces. (author)

Hydrodynamic boundary conditions for one-component liquid-gas flows on non-isothermal solid substrates

KAUST Repository

Xu, Xinpeng; Liu, Chun; Qian, Tiezheng

2012-01-01

profiles of liquid-gas flows on non-isothermal, heterogeneous solid substrates is still absent. The purpose of this work is to construct a continuum model for simulating the liquid-gas flows on solid surfaces that are flat and rigid, and may involve

Displacement Ventilation

DEFF Research Database (Denmark)

Bjørn, Erik; Mattsson, Magnus; Sandberg, Mats

Full-scale experiments were made in a displacement ventilated room with two breathing thermal manikins to study the effect of movements and breathing on the vertical contaminant distribution, and on the personal exposure of occupants. Concentrations were measured with tracer gas equipment...

Adsorption of gas mixtures on heterogeneous solid surfaces

Energy Technology Data Exchange (ETDEWEB)

Jaroniec, M; Rudzinski, W

1977-01-01

A review of theoretical studies on the physical adsorption from gas mixtures on heterogeneous solid surfaces, mainly by Jaroniec and coworkers, covers the vector notation used in the calculations; adsorption isotherms for multicomponent gases; the generalized integral equation for adsorption of gas mixtures, its numerical and analytical solutions, applied, (e.g., to interpret the experimental adsorption isotherms of ethane/ethylene on Nuxit-AL); thermodynamic relations, applied, (e.g., to calculating isosteric adsorption heats from experimental parameters for the adsorption of propylene from propane/propylene mixtures on Nuxit-AL); and the derivation and use of a simplified integral equation for describing the adsorption from gas mixtures on heterogeneous surfaces. 75 references.

Control of DNA strand displacement kinetics using toehold exchange.

Science.gov (United States)

Zhang, David Yu; Winfree, Erik

2009-12-02

DNA is increasingly being used as the engineering material of choice for the construction of nanoscale circuits, structures, and motors. Many of these enzyme-free constructions function by DNA strand displacement reactions. The kinetics of strand displacement can be modulated by toeholds, short single-stranded segments of DNA that colocalize reactant DNA molecules. Recently, the toehold exchange process was introduced as a method for designing fast and reversible strand displacement reactions. Here, we characterize the kinetics of DNA toehold exchange and model it as a three-step process. This model is simple and quantitatively predicts the kinetics of 85 different strand displacement reactions from the DNA sequences. Furthermore, we use toehold exchange to construct a simple catalytic reaction. This work improves the understanding of the kinetics of nucleic acid reactions and will be useful in the rational design of dynamic DNA and RNA circuits and nanodevices.

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

Directory of Open Access Journals (Sweden)

Josef Schachtner

2016-08-01

Full Text Available A home-built microreactor system for light-mediated biphasic gas/liquid reactions was assembled from simple commercial components. This paper describes in full detail the nature and function of the required building elements, the assembly of parts, and the tuning and interdependencies of the most important reactor and reaction parameters. Unlike many commercial thin-film and microchannel reactors, the described set-up operates residence times of up to 30 min which cover the typical rates of many organic reactions. The tubular microreactor was successfully applied to the photooxygenation of hydrocarbons (Schenck ene reaction. Major emphasis was laid on the realization of a constant and highly reproducible gas/liquid slug flow and the effective illumination by an appropriate light source. The optimized set of conditions enabled the shortening of reaction times by more than 99% with equal chemoselectivities. The modular home-made flow reactor can serve as a prototype model for the continuous operation of various other reactions at light/liquid/gas interfaces in student, research, and industrial laboratories.

Rapid estimate of solid volume in large tuff cores using a gas pycnometer

Energy Technology Data Exchange (ETDEWEB)

Thies, C. [ed.; Geddis, A.M.; Guzman, A.G. [and others

1996-09-01

A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1{degrees}C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm{sup 3} with less than 1% error.

Greenhouse gas emissions from solid waste in Beijing: The rising trend and the mitigation effects by management improvements.

Science.gov (United States)

Yu, Yongqiang; Zhang, Wen

2016-04-01

Disposal of solid waste poses great challenges to city managements. Changes in solid waste composition and disposal methods, along with urbanisation, can certainly affect greenhouse gas emissions from municipal solid waste. In this study, we analysed the changes in the generation, composition and management of municipal solid waste in Beijing. The changes of greenhouse gas emissions from municipal solid waste management were thereafter calculated. The impacts of municipal solid waste management improvements on greenhouse gas emissions and the mitigation effects of treatment techniques of greenhouse gas were also analysed. Municipal solid waste generation in Beijing has increased, and food waste has constituted the most substantial component of municipal solid waste over the past decade. Since the first half of 1950s, greenhouse gas emission has increased from 6 CO2-eq Gg y(-1)to approximately 200 CO2-eq Gg y(-1)in the early 1990s and 2145 CO2-eq Gg y(-1)in 2013. Landfill gas flaring, landfill gas utilisation and energy recovery in incineration are three techniques of the after-emission treatments in municipal solid waste management. The scenario analysis showed that three techniques might reduce greenhouse gas emissions by 22.7%, 4.5% and 9.8%, respectively. In the future, if waste disposal can achieve a ratio of 4:3:3 by landfill, composting and incineration with the proposed after-emission treatments, as stipulated by the Beijing Municipal Waste Management Act, greenhouse gas emissions from municipal solid waste will decrease by 41%. © The Author(s) 2016.

Electron transfer reactions

CERN Document Server

Cannon, R D

2013-01-01

Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

Investigation of a Gas-Solid Separation Process for Cement Raw Meal

DEFF Research Database (Denmark)

Maarup, Claus; Hjuler, Klaus; Clement, Karsten

2015-01-01

The gas/solid heat exchanger (2D-HX), developed to replace the cyclone preheaters in cement plants is presented. This design aims at reducing construction height and operation costs. The separation process in the 2D-HX is experimentally investigated, and the results show that separation efficienc......The gas/solid heat exchanger (2D-HX), developed to replace the cyclone preheaters in cement plants is presented. This design aims at reducing construction height and operation costs. The separation process in the 2D-HX is experimentally investigated, and the results show that separation...

Tuning Catalytic Performance through a Single or Sequential Post-Synthesis Reaction(s) in a Gas Phase

Energy Technology Data Exchange (ETDEWEB)

Shan, Junjun [Department; Department; Zhang, Shiran [Department; Department; Choksi, Tej [Department; Nguyen, Luan [Department; Department; Bonifacio, Cecile S. [Department; Li, Yuanyuan [Department; Zhu, Wei [Department; Department; College; Tang, Yu [Department; Department; Zhang, Yawen [College; Yang, Judith C. [Department; Greeley, Jeffrey [Department; Frenkel, Anatoly I. [Department; Tao, Franklin [Department; Department

2016-12-05

Catalytic performance of a bimetallic catalyst is determined by geometric structure and electronic state of the surface or even the near-surface region of the catalyst. Here we report that single and sequential postsynthesis reactions of an as-synthesized bimetallic nanoparticle catalyst in one or more gas phases can tailor surface chemistry and structure of the catalyst in a gas phase, by which catalytic performance of this bimetallic catalyst can be tuned. Pt–Cu regular nanocube (Pt–Cu RNC) and concave nanocube (Pt–Cu CNC) are chosen as models of bimetallic catalysts. Surface chemistry and catalyst structure under different reaction conditions and during catalysis were explored in gas phase of one or two reactants with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The newly formed surface structures of Pt–Cu RNC and Pt–Cu CNC catalysts strongly depend on the reactive gas(es) used in the postsynthesis reaction(s). A reaction of Pt–Cu RNC-as synthesized with H2 at 200 °C generates a near-surface alloy consisting of a Pt skin layer, a Cu-rich subsurface, and a Pt-rich deep layer. This near-surface alloy of Pt–Cu RNC-as synthesized-H2 exhibits a much higher catalytic activity in CO oxidation in terms of a low activation barrier of 39 ± 4 kJ/mol in contrast to 128 ± 7 kJ/mol of Pt–Cu RNC-as synthesized. Here the significant decrease of activation barrier demonstrates a method to tune catalytic performances of as-synthesized bimetallic catalysts. A further reaction of Pt–Cu RNC-as synthesized-H2 with CO forms a Pt–Cu alloy surface, which exhibits quite different catalytic performance in CO oxidation. It suggests the capability of generating a different surface by using another gas. The capability of tuning surface chemistry and structure of bimetallic catalysts was also demonstrated in restructuring of Pt–Cu CNC-as synthesized.

C-terminal peptide extension via gas-phase ion/ion reactions

Science.gov (United States)

Peng, Zhou; McLuckey, Scott A.

2015-01-01

The formation of peptide bonds is of great importance from both a biological standpoint and in routine organic synthesis. Recent work from our group demonstrated the synthesis of peptides in the gas-phase via ion/ion reactions with sulfo-NHS reagents, which resulted in conjugation of individual amino acids or small peptides to the N-terminus of an existing ‘anchor’ peptide. Here, we demonstrate a complementary approach resulting in the C-terminal extension of peptides. Individual amino acids or short peptides can be prepared as reagents by incorporating gas phase-labile protecting groups to the reactive C-terminus and then converting the N-terminal amino groups to the active ketenimine reagent. Gas-phase ion/ion reactions between the anionic reagents and doubly protonated “anchor” peptide cations results in extension of the “anchor” peptide with new amide bond formation at the C-terminus. We have demonstrated that ion/ion reactions can be used as a fast, controlled, and efficient means for C-terminal peptide extension in the gas phase. PMID:26640400

Heat transfer problems in gas-cooled solid blankets

International Nuclear Information System (INIS)

Fillo, J.A.; Powell, J.R.

1976-01-01

In all fusion reactors using the deuterium-tritium fuel cycle, a large fraction approximately 80 percent of the fusion energy will be released as approximately 14 MeV neutrons which must be slowed down in a relatively thick blanket surrounding the plasma, thereby, converting their kinetic energy to high temperature heat which can be continuously removed by a coolant stream and converted in part to electricity in a conventional power turbine. Because of the primary goal of achieving minimum radioactivity, to date Brookhaven blanket concepts have been restricted to the use of some form of solid lithium, with inert gas-cooling and in some design cases, water-cooling of the shell structure. Aluminum and graphite have been identified as very promising structural materials for fusion blankets, and conceptual designs based on these materials have been made. Depending on the thermal loading on the ''first'' wall which surrounds the plasma as well as blanket design, heat transfer problems may be noticeably different in gas-cooled solid blankets. Approaches to solution of heat removal problems as well as explanation of: (a) the after-heat problems in blankets; (b) tritium breeding in solids; and (c) materials selection for radiation shields relative to the minimum activity blanket efforts at Brookhaven are discussed

The equivalent electrical permittivity of gas-solid mixtures at intermediate solid volume fractions.

Energy Technology Data Exchange (ETDEWEB)

Torczynski, John Robert; Ceccio, Steven Louis; Tortora, Paul Richard

2005-07-01

Several mixture models are evaluated for their suitability in predicting the equivalent permittivity of dielectric particles in a dielectric medium for intermediate solid volume fractions (0.4 to 0.6). Predictions of the Maxwell, Rayleigh, Bottcher and Bruggeman models are compared to computational simulations of several arrangements of solid particles in a gas and to the experimentally determined permittivity of a static particle bed. The experiment uses spherical glass beads in air, so air and glass permittivity values (1 and 7, respectively) are used with all of the models and simulations. The experimental system used to measure the permittivity of the static particle bed and its calibration are described. The Rayleigh model is found to be suitable for predicting permittivity over the entire range of solid volume fractions (0-0.6).

Exchange reactions in the systems of alkali metal, silver and thallium, sulfates, niobates and tantalates

International Nuclear Information System (INIS)

Belyaev, I.N.; Lupejko, T.G.; Nalbandyan, V.B.; Abanina, E.V.

1978-01-01

Investigated are exchange interactions in diagonal cross sections of twenty triple mutual systems with A and A' cations and SO 4 and MO 3 anions where A and A'-Li, Na, K, Ag, Tl, M-Nb, Ta using the methods of X-ray phase, chemical and differential thermal analyses. Exchange reaction between crystal complex oxide and melted salt are effective synthesis method. These reactions in particular permitted to obtain pure AgNbO 3 , AgTaO 3 and their solid solutions at temperatures hundreds degrees lower than in displacement reactions. Equilibrium samples of AMO 3 -A'MO 3 systems, continuous or discontinuous solid solutions, compounds (except NaMO 3 -KMO 3 , and also LiTaO 3 -KTaO 3 ) are formed in exchange reactions when there is sulfate shortage. Thus, exchange reactions can be applied for solid solution synthesis, and also for phase diagram study

An alternative preparation method for ion exchanged catalysts: Solid state redox reaction

DEFF Research Database (Denmark)

Schneider, E.; Hagen, A.; Grunwaldt, J.-D.

2004-01-01

A new method for modifying zeolites with zinc is proposed. The solid state redox reaction between metallic zinc and ZSM-5 zeolites with different Si/Al ratios was investigated by temperature programmed hydrogen evolution (TPHE), X-ray absorption near edge structure (XANES) and diffuse reflectance...... infrared Fourier transform spectroscopy (DRIFTS). The evolution of hydrogen was detected at temperatures above 620 K. The source of hydrogen was the solid state redox reaction of the metal with protons of the support. The samples exhibit catalytic activity in ethane aromatization indicating that zinc...... should be located at the same sites as in catalysts prepared by conventional methods. Combination of XANES and catalytic activity point to zinc being mainly present in tetrahedral geometry under reaction conditions....

Method and system for purification of gas streams for solid oxide cells

DEFF Research Database (Denmark)

2011-01-01

of: - providing at least one scrubber in the gas stream at the inlet side of the first electrode of the solid oxide cell; and/or providing at least one scrubber in the gas stream at the inlet side of the second electrode of the solid oxide cell; and - purifying the gas streams towards the first...... and second electrode; wherein the at least one scrubber in the gas stream at the inlet side of the first electrode and/or the at least one scrubber in the gas stream at the inlet side of the second electrode comprises a material suitable as an electrolyte material and a material suitable as an electrode...... material, and wherein the material suitable as an electrolyte material and a material suitable as an electrode material form triple phase boundaries similar to or identical to the triple phase boundaries of the electrode for which the gas stream is purified with the at least one scrubber....

Laboratory investigations of the alpha-pinene/ozone gas-phase reaction

International Nuclear Information System (INIS)

Benner, C.L.

1985-01-01

In order to provide more insight into terpene photooxidation or ozonolysis reaction mechanisms, a radiotracer technique was developed. This technique was applied to an investigation of the 14 C-alpha-pinene/ozone reaction. In the first phase of the research, the carbon distribution at the conclusion of the ozonolysis reaction was determined by separating carbon-14-labelled gaseous products from labelled aerosols, and counting each phase by liquid scintillation methods. The resulting carbon balance was 38% to 60% filtered aerosols, 6% to 20% gas phase compounds, and 11% to 29% products absorbed on the reaction chamber walls. Recoveries of the alpha-pinene carbon-14 ranging from 79% to 97% were achieved using this method. The alpha-pinene concentrations in these experiments were close to ambient (1 part per billion), yet the carbon balance was similar to that observed at much higher concentrations (>1 part per million). In the second phase of the alpha-pinene study, both gas and aerosol products of the ozonolysis reaction were collected on cartridges impregnated with 2,4-dinitrophenylhydrazine, then analyzed by HPLC. In the final experiments, alpha-pinene aerosol was reacted with a silylating agent to improve the detection of organic acids and alcohols. The gas chromatographic/mass spectrometric analysis of the silylated aerosol products showed evidence of dimer/polymer formation occurring in the ozonolysis reaction

Measurement of flow characteristics of solid particles mixed with gas in pipelines

Energy Technology Data Exchange (ETDEWEB)

Siberev, S P; Nazarov, S I; Soldatkin, G I

1983-01-01

A mathematical model of the interaction of solid particles in a gas stream flowing through a pipeline comprises equations for the energy and material balances in the system and for force and energy interactions between the solid particles and transducers located within the pipeline. Soviet researchers confirmed that the average value of stress recorded by a transducer is proportional to the average kinetic energy of the particles; for a constant particle speed, the stress is proportional to the mass flow of the particles. The analysis and flow transducer measurements are valuable in measuring and controlling flowline sand and soil in natural gas transport from gas wells and undergound storage facilities.

The Chemistry of Inorganic Precursors during the Chemical Deposition of Films on Solid Surfaces.

Science.gov (United States)

Barry, Seán T; Teplyakov, Andrew V; Zaera, Francisco

2018-03-20

The deposition of thin solid films is central to many industrial applications, and chemical vapor deposition (CVD) methods are particularly useful for this task. For one, the isotropic nature of the adsorption of chemical species affords even coverages on surfaces with rough topographies, an increasingly common requirement in microelectronics. Furthermore, by splitting the overall film-depositing reactions into two or more complementary and self-limiting steps, as it is done in atomic layer depositions (ALD), film thicknesses can be controlled down to the sub-monolayer level. Thanks to the availability of a vast array of inorganic and metalorganic precursors, CVD and ALD are quite versatile and can be engineered to deposit virtually any type of solid material. On the negative side, the surface chemistry that takes place in these processes is often complex, and can include undesirable side reactions leading to the incorporation of impurities in the growing films. Appropriate precursors and deposition conditions need to be chosen to minimize these problems, and that requires a proper understanding of the underlying surface chemistry. The precursors for CVD and ALD are often designed and chosen based on their known thermal chemistry from inorganic chemistry studies, taking advantage of the vast knowledge developed in that field over the years. Although a good first approximation, however, this approach can lead to wrong choices, because the reactions of these precursors at gas-solid interfaces can be quite different from what is seen in solution. For one, solvents often aid in the displacement of ligands in metalorganic compounds, providing the right dielectric environment, temporarily coordinating to the metal, or facilitating multiple ligand-complex interactions to increase reaction probabilities; these options are not available in the gas-solid reactions associated with CVD and ALD. Moreover, solid surfaces act as unique "ligands", if these reactions are to be

Analysis of reaction products formed in the gas phase reaction of E,E-2,4-hexadienal with atmospheric oxidants: Reaction mechanisms and atmospheric implications

Science.gov (United States)

Colmenar, I.; Martin, P.; Cabañas, B.; Salgado, S.; Martinez, E.

2018-03-01

An analysis of reaction products for the reaction of E,E-2,4-hexadienal with chlorine atoms (Cl) and OH and NO3 radicals has been carried out at the first time with the aim of obtaining a better understanding of the tropospheric reactivity of α,β-unsaturated carbonyl compounds. Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography-Mass Spectrometry with a Time of Flight detector (GC-TOFMS) were used to carry out the qualitative and/or quantitative analyses. Reaction products in gas and particulate phase were observed from the reactions of E,E-2,4- hexadienal with all oxidants. E/Z-Butenedial and maleic anhydride were the main products identified in gas phase. E-butenedial calculated molar yield ranging from 4 to 10%. A significant amount of multifunctional compounds (chloro and hydroxy carbonyls) was identified. These compounds could be formed in particulate phase explaining the ∼90% of unaccounted carbon in gas phase. The reaction with Cl atoms in the presence of NOx with a long reaction time gave Peroxy Acetyl Nitrate (PAN) as an additional product, which is known for being an important specie in the generation of the photochemical smog. Nitrated compounds were the major organic products from the reaction with the NO3 radical. Based on the identified products, the reaction mechanisms have been proposed. In these mechanisms a double bond addition of the atmospheric oxidant at C4/C5 of E,E-2,4-hexadienal is the first step for tropospheric degradation.

Plasmid-derived DNA Strand Displacement Gates for Implementing Chemical Reaction Networks.

Science.gov (United States)

Chen, Yuan-Jyue; Rao, Sundipta D; Seelig, Georg

2015-11-25

DNA nanotechnology requires large amounts of highly pure DNA as an engineering material. Plasmid DNA could meet this need since it is replicated with high fidelity, is readily amplified through bacterial culture and can be stored indefinitely in the form of bacterial glycerol stocks. However, the double-stranded nature of plasmid DNA has so far hindered its efficient use for construction of DNA nanostructures or devices that typically contain single-stranded or branched domains. In recent work, it was found that nicked double stranded DNA (ndsDNA) strand displacement gates could be sourced from plasmid DNA. The following is a protocol that details how these ndsDNA gates can be efficiently encoded in plasmids and can be derived from the plasmids through a small number of enzymatic processing steps. Also given is a protocol for testing ndsDNA gates using fluorescence kinetics measurements. NdsDNA gates can be used to implement arbitrary chemical reaction networks (CRNs) and thus provide a pathway towards the use of the CRN formalism as a prescriptive molecular programming language. To demonstrate this technology, a multi-step reaction cascade with catalytic kinetics is constructed. Further it is shown that plasmid-derived components perform better than identical components assembled from synthetic DNA.

Physicochemical characterization of some solid materials by inverse gas chromatography

International Nuclear Information System (INIS)

Hamieh, T.; Abdessater, S.

2004-01-01

Full text.New equations and models on two-dimensional state of solid surfaces were previously elaborated in many other studies. results obtained were used in this paper to the determination and the quantification of some physicochemical properties of some solid surfaces, and especially, to study the acid-base superficial characteristics of some solid substrates like oxides and/or polymer adsorbed on oxides, carbon fibers, cements, etc. The technique used was the inverse gas chromatography (CGI) at infinite dilution. The acid-base constants were calculated for many solid surfaces: Al 2 O 3 , SiO 2 , MgO, ZnO, some cements, textiles and carbon fibers

A nanostructured surface increases friction exponentially at the solid-gas interface.

Science.gov (United States)

Phani, Arindam; Putkaradze, Vakhtang; Hawk, John E; Prashanthi, Kovur; Thundat, Thomas

2016-09-06

According to Stokes' law, a moving solid surface experiences viscous drag that is linearly related to its velocity and the viscosity of the medium. The viscous interactions result in dissipation that is known to scale as the square root of the kinematic viscosity times the density of the gas. We observed that when an oscillating surface is modified with nanostructures, the experimentally measured dissipation shows an exponential dependence on kinematic viscosity. The surface nanostructures alter solid-gas interplay greatly, amplifying the dissipation response exponentially for even minute variations in viscosity. Nanostructured resonator thus allows discrimination of otherwise narrow range of gaseous viscosity making dissipation an ideal parameter for analysis of a gaseous media. We attribute the observed exponential enhancement to the stochastic nature of interactions of many coupled nanostructures with the gas media.

A nanostructured surface increases friction exponentially at the solid-gas interface

Science.gov (United States)

Phani, Arindam; Putkaradze, Vakhtang; Hawk, John E.; Prashanthi, Kovur; Thundat, Thomas

2016-09-01

According to Stokes’ law, a moving solid surface experiences viscous drag that is linearly related to its velocity and the viscosity of the medium. The viscous interactions result in dissipation that is known to scale as the square root of the kinematic viscosity times the density of the gas. We observed that when an oscillating surface is modified with nanostructures, the experimentally measured dissipation shows an exponential dependence on kinematic viscosity. The surface nanostructures alter solid-gas interplay greatly, amplifying the dissipation response exponentially for even minute variations in viscosity. Nanostructured resonator thus allows discrimination of otherwise narrow range of gaseous viscosity making dissipation an ideal parameter for analysis of a gaseous media. We attribute the observed exponential enhancement to the stochastic nature of interactions of many coupled nanostructures with the gas media.

Reactions of newly formed fission products in the gas phase

International Nuclear Information System (INIS)

Strickert, R.G.

1976-01-01

A dynamic gas-flow system was constructed which stopped fission products in the gas phase and rapidly separated (in less than 2 sec) volatile compounds from non-volatile ones. The filter assembly designed and used was shown to stop essentially all non-volatile fission products. Between 5 percent and 20 percent of tellurium fission-product isotopes reacted with several hydrocarbon gases to form volatile compounds, which passed through the filter. With carbon monoxide gas, volatile tellurium compound(s) (probably TeCO) were also formed with similar efficiencies. The upper limits for the yields of volatile compounds formed between CO and tin and antimony fission products were shown to be less than 0.3 percent, so tellurium nuclides, not their precursors, reacted with CO. It was found that CO reacted preferentially with independently produced tellurium atoms; the reaction efficiency of beta-produced atoms was only 27 +- 3 percent of that of the independently formed atoms. The selectivity, which was independent of the over-all reaction efficiency, was shown to be due to reaction of independently formed atoms in the gas phase. The gas phase reactions are believed to occur mainly at thermal energies because of the independence of the yield upon argon moderator mole-fraction (up to 80 percent). It was shown in some experiments that about one-half of the TeCO decomposed in passing through a filter and that an appreciable fraction (approximately 20 percent) of the tellurium atoms deposited on the filter reacted agin with CO. Other tellurium atoms on the filter surface (those formed by beta decay and those formed independently but not reacting in the gas phase) also reacted with CO, but probably somewhat less efficiently than atoms formed by TeCO decomposition. No evidence was found for formation of TeCO as a direct result of beta-decay

The radiation chemistry of organic solids

International Nuclear Information System (INIS)

Willard, J.E.

1987-01-01

The yields of primary products (ions, electrons, and excited state) produced by exposure of an organic compound to ionizing radiation are essentially independent of whether it is in the gas, liquid, or solid state. However, the nature and yields of the final products are often dependent on the state. This is the result of the effects of density and temperature on the relative probabilities of competing reactions of the primary species and of the radicals which they produce. The density effects are of two types. First, the dose proximity of neighboring molecules in the solid favors reactivation rather than decomposition of excited molecules and favors prompt recombination in the parent cage of the fragments of any that do decompose. Second, since the distance traveled by an energetic electron is depositing its energy is inversely proportional to the density of the medium, the tracks are shorter and the spur radii smaller in the solid than in the liquid (and in great contrast to the gas, where spur effects are negligible). The increased role of intraspur reactions of radicals, electrons, and cations in solids is shown by the results discussed in this chapter

Ion-neutral gas reactions in a collision/reaction cell in inductively coupled plasma mass spectrometry: Correlation of ion signal decrease to kinetic rate constants

Energy Technology Data Exchange (ETDEWEB)

Gray, Patrick J. [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States); Department of Chemistry, The Ohio State University, 120 18th Avenue, Columbus, OH 43210 (United States); Olesik, John W., E-mail: olesik.2@osu.edu [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States)

2015-03-01

Reaction gas flow rate dependent Ar{sub 2}{sup +} and Ar{sup +} signals are correlated to fundamental kinetic rate coefficients. A simple calculation, assuming that gas exits the reaction cell due only to effusion, is described to estimate the gas pressure in the reaction cell. The value of the product of the kinetic rate constant and the ion residence time in the reaction cell can be determined from experimental measurement of the decrease in an ion signal as a function of reaction gas flow rate. New kinetic rate constants are determined for the reaction of CH{sub 3}F with Ar{sup +} and Ar{sub 2}{sup +}. - Highlights: • How to determine pressure and the product of the kinetic rate constant times the ion residence time in reaction cell • Relate measured ICP-DRC-MS signals versus gas flow rate to kinetic rate constants measured previously using SIFT-MS • Describe how to determine previously unmeasured kinetic rate constants using ICP-DRC-MS.

Reaction of uranium and the fluorocarbon FC-75

Science.gov (United States)

Young, R. H.

1985-04-01

Because of criticality concerns with water cooling in enriched uranium upgrading, a fluorocarbon has been evaluated as a replacement coolant for internal module components in the Plasma Separation Process (PSP). The interaction of bulk uranium and of powdered uranium with FC-75 has been investigated at temperatures between 200 and 700 C. The gas pressure and the metal temperature were monitored as a function of time. Modest temperature changes of 50 to 100 C were observed for the bulk uranium/fluorocarbon reaction. Much larger changes (up to 1000 C) were noted for the reaction involving high surface area uranium powder. These temperature transients, particularly for the powdered uranium reaction, were short-lived ( 10 seconds) and indicative of the formation of a protective layer of reaction products. Analysis of residual gas products by infrared spectroscopy indicated that one potentially serious hazard, UF6, was not present; however, several small toxic fluorocarbons were produced by thermolysis and/or reaction. X-ray diffraction analysis of the residual solids indicated UF4 and UO2 were the major solid products.

Solid-Gas Coupling Model for Coal-Rock Mass Deformation and Pressure Relief Gas Flow in Protection Layer Mining

OpenAIRE

Zhu, Zhuohui; Feng, Tao; Yuan, Zhigang; Xie, Donghai; Chen, Wei

2018-01-01

The solid-gas coupling model for mining coal-rock mass deformation and pressure relief gas flow in protection layer mining is the key to determine deformation of coal-rock mass and migration law of pressure relief gas of protection layer mining in outburst coal seams. Based on the physical coupling process between coal-rock mass deformation and pressure-relief gas migration, the coupling variable of mining coal-rock mass, a part of governing equations of gas seepage field and deformation fiel...

Integration of a municipal solid waste gasification plant with solid oxide fuel cell and gas turbine

DEFF Research Database (Denmark)

Bellomare, Filippo; Rokni, Masoud

2013-01-01

An interesting source of producing energy with low pollutants emission and reduced environmental impact are the biomasses; particularly using Municipal Solid Waste (MSW) as fuel, can be a competitive solution not only to produce energy with negligible costs but also to decrease the storage...... in landfills. A Municipal Solid Waste Gasification Plant Integrated with Solid Oxide Fuel Cell (SOFC) and Gas Turbine (GT) has been studied and the plant is called IGSG (Integrated Gasification SOFC and GT). Gasification plant is fed by MSW to produce syngas by which the anode side of an SOFC is fed wherein...

Highly sensitive "signal-on" electrochemiluminescent biosensor for the detection of DNA based on dual quenching and strand displacement reaction.

Science.gov (United States)

Lou, Jing; Wang, Zhaoyin; Wang, Xiao; Bao, Jianchun; Tu, Wenwen; Dai, Zhihui

2015-10-07

A "signal-on" electrochemiluminescent DNA biosensing platform was proposed based on the dual quenching and strand displacement reaction. This novel "signal-on" detection strategy revealed its sensitivity in achieving a detection limit of 2.4 aM and its selectivity in distinguishing single nucleotide polymorphism of target DNA.

Ultraselective electrochemiluminescence biosensor based on locked nucleic acid modified toehold-mediated strand displacement reaction and junction-probe.

Science.gov (United States)

Zhang, Xi; Zhang, Jing; Wu, Dongzhi; Liu, Zhijing; Cai, Shuxian; Chen, Mei; Zhao, Yanping; Li, Chunyan; Yang, Huanghao; Chen, Jinghua

2014-12-07

Locked nucleic acid (LNA) is applied in toehold-mediated strand displacement reaction (TMSDR) to develop a junction-probe electrochemiluminescence (ECL) biosensor for single-nucleotide polymorphism (SNP) detection in the BRCA1 gene related to breast cancer. More than 65-fold signal difference can be observed with perfectly matched target sequence to single-base mismatched sequence under the same conditions, indicating good selectivity of the ECL biosensor.

Desulfurization reaction of high sulfur content flue gas treated by electron beam

International Nuclear Information System (INIS)

Hirosawa, Shojiro; Suzuki, Ryoji; Aoki, Shinji; Kojima, Takuji; Hashimoto, Shoji

2002-01-01

Experiments of flue gas treatment by electron beam were carried out, using simulated ligniteburning flue gas containing SO 2 (5500 ppm), NO (390 ppm) and H 2 O (22%). Removal efficiency of SO 2 was more than 90% at a dose of 1-2 kGy. It shows applicability of electron beam for treatment of lignite-burning flue gas. Another removal reaction besides the radiation-induced radical reaction and the thermal reaction occurring without irradiation was suggested by the facts that removal of SO 2 by the radical reaction is only a few hundreds of ppm and the removal amounts by thermal reaction under irradiation is lower than a half of total desulfurization. The mechanism similar to thermal reaction was proposed, assuming simultaneous uptake reaction of SO 2 and NH 3 on the surface of liquid aerosol. It was suggested that ammonium nitrate having deliquescence relative humidity (DRH) of 60% at 25 deg C plays an important role in producing liquid aerosols. Decrease of DRH of ammonium nitrate with elevating temperature and with formation of double salt of ammonium sulfate results in enhancement of formation of liquid aerosols. (author)

Fabrication of dendritic silver-coated copper powders by galvanic displacement reaction and their thermal stability against oxidation

International Nuclear Information System (INIS)

Park, Yu-Seon; An, Chang Yong; Kannan, Padmanathan Karthick; Seo, Nary; Zhuo, Kai; Yoo, Tae Kyong; Chung, Chan-Hwa

2016-01-01

Highlights: • The dendritic silver-coated copper powders with high specific surface area have been prepared using a simple wet chemical reduction process at room temperature. • It is found that the Cu starts to be oxidized into Cu_2O followed by CuO at elevated temperatures. • The more amount of Ag-coating provides the less oxidation, which confirms that the Ag-shell prevents the Cu-core from oxidation. • The resistivity of dendritic 33.27 wt.% Ag-coated Cu powders was measured to 25.67 μΩ cm after the annealing at 150 °C for 30 min. - Abstract: Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a galvanic displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the galvanic displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150 °C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.

Fabrication of dendritic silver-coated copper powders by galvanic displacement reaction and their thermal stability against oxidation

Energy Technology Data Exchange (ETDEWEB)

Park, Yu-Seon [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Farad Materials Co., Ltd., Suwon 16419 (Korea, Republic of); An, Chang Yong; Kannan, Padmanathan Karthick; Seo, Nary [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Zhuo, Kai [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Farad Materials Co., Ltd., Suwon 16419 (Korea, Republic of); Yoo, Tae Kyong [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Chung, Chan-Hwa, E-mail: chchung@skku.edu [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Farad Materials Co., Ltd., Suwon 16419 (Korea, Republic of)

2016-12-15

Highlights: • The dendritic silver-coated copper powders with high specific surface area have been prepared using a simple wet chemical reduction process at room temperature. • It is found that the Cu starts to be oxidized into Cu{sub 2}O followed by CuO at elevated temperatures. • The more amount of Ag-coating provides the less oxidation, which confirms that the Ag-shell prevents the Cu-core from oxidation. • The resistivity of dendritic 33.27 wt.% Ag-coated Cu powders was measured to 25.67 μΩ cm after the annealing at 150 °C for 30 min. - Abstract: Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a galvanic displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the galvanic displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150 °C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.

Gas production in anaerobic dark-fermentation processes from agriculture solid waste

Science.gov (United States)

Sriwuryandari, L.; Priantoro, E. A.; Sintawardani, N.

2017-03-01

Approximately, Bandung produces agricultural solid waste of 1549 ton/day. This wastes consist of wet-organic matter and can be used for bio-gas production. The research aimed to apply the available agricultural solid waste for bio-hydrogen. Biogas production was done by a serial of batches anaerobic fermentation using mix-culture bacteria as the active microorganism. Fermentation was carried out inside a 30 L bioreactor at room temperature. The analyzed parameters were of pH, total gas, temperature, and COD. Result showed that from 3 kg/day of organic wastes, various total gases of O2, CH4, H2, CO2, and CnHn,O2 was produced.

Gas-Liquid Precipitation of water dissolved heavy metal ions using hydrogen sulfide gas

NARCIS (Netherlands)

Al Tarazi, M.Y.M.

2004-01-01

Precipitation of solids promoted by gas-liquid reactions is applied in many industrial processes such as the production of ammonium phosphate, ammonium sulphate, barium carbonate, calcium carbonate, calcium fluoride, ypsum (calcium sulphate), goethite, sodium bicarbonate, strontium carbonate and

Solid State Pathways towards Molecular Complexity in Space

Science.gov (United States)

Linnartz, Harold; Bossa, Jean-Baptiste; Bouwman, Jordy; Cuppen, Herma M.; Cuylle, Steven H.; van Dishoeck, Ewine F.; Fayolle, Edith C.; Fedoseev, Gleb; Fuchs, Guido W.; Ioppolo, Sergio; Isokoski, Karoliina; Lamberts, Thanja; Öberg, Karin I.; Romanzin, Claire; Tenenbaum, Emily; Zhen, Junfeng

2011-12-01

It has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment such as the interstellar medium. In the last decennium more and more evidence has been found that the observed mix of small and complex, stable and highly transient species in space is the cumulative result of gas phase and solid state reactions as well as gas-grain interactions. Solid state reactions on icy dust grains are specifically found to play an important role in the formation of the more complex ``organic'' compounds. In order to investigate the underlying physical and chemical processes detailed laboratory based experiments are needed that simulate surface reactions triggered by processes as different as thermal heating, photon (UV) irradiation and particle (atom, cosmic ray, electron) bombardment of interstellar ice analogues. Here, some of the latest research performed in the Sackler Laboratory for Astrophysics in Leiden, the Netherlands is reviewed. The focus is on hydrogenation, i.e., H-atom addition reactions and vacuum ultraviolet irradiation of interstellar ice analogues at astronomically relevant temperatures. It is shown that solid state processes are crucial in the chemical evolution of the interstellar medium, providing pathways towards molecular complexity in space.

Advances of zeolite based membrane for hydrogen production via water gas shift reaction

Science.gov (United States)

Makertihartha, I. G. B. N.; Zunita, M.; Rizki, Z.; Dharmawijaya, P. T.

2017-07-01

Hydrogen is considered as a promising energy vector which can be obtained from various renewable sources. However, an efficient hydrogen production technology is still challenging. One technology to produce hydrogen with very high capacity with low cost is through water gas shift (WGS) reaction. Water gas shift reaction is an equilibrium reaction that produces hydrogen from syngas mixture by the introduction of steam. Conventional WGS reaction employs two or more reactors in series with inter-cooling to maximize conversion for a given volume of catalyst. Membrane reactor as new technology can cope several drawbacks of conventional reactor by removing reaction product and the reaction will favour towards product formation. Zeolite has properties namely high temperature, chemical resistant, and low price makes it suitable for membrane reactor applications. Moreover, it has been employed for years as hydrogen selective layer. This review paper is focusing on the development of membrane reactor for efficient water gas shift reaction to produce high purity hydrogen and carbon dioxide. Development of membrane reactor is discussed further related to its modification towards efficient reaction and separation from WGS reaction mixture. Moreover, zeolite framework suitable for WGS membrane reactor will be discussed more deeply.

Modelling combustion reactions for gas flaring and its resulting emissions

Directory of Open Access Journals (Sweden)

O. Saheed Ismail

2016-07-01

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

Gas-Solid Displacement Reactions for Converting Silica Diatom Frustules into MgO and TiO₂

Energy Technology Data Exchange (ETDEWEB)

Kalem, Tugba [Iowa State Univ., Ames, IA (United States)

2004-01-01

Technology for the microfabrication of freely moving parts began with a Bell Labs microgear spun by an air jet, and electrostatic silicon micro motors in the mid-1980s. It continued with development work on micropositioning of optics, miniature heat exchangers, small fluidic devices, and chemical reaction chambers. Recently, there has been a great deal of interest centered on the design and manufacture of devices of nanometer proportions and this speculation has spawned a new industry named, nanotechnology. Despite the technological and economic promise of this technology, current commercial micro/mesofabrication methods have largely been based upon two-dimensional processing principles which is not well suited to the low-cost mass production of three-dimensional micro devices with complex geometries and meso/nanoscale features. Diatoms are three dimensional (3D) microstructures from nature that provide a practical alternative for nanotechnology and microfabrication. Diatoms (Figure 1) are single-celled micro algae that form rigid cell walls (frustules) composed of amorphous silica. Their dimensions can range from less than 1 micron to several hundreds of microns. They are distributed throughout the world in aquatic, semi-aquatic and moist habitats, and extremely abundant in freshwater and marine ecosystems. Diatoms are thought to be responsible for up to 25% of the world's net primary production of organic carbon (by transforming of carbon dioxide and water into sugars by photosynthesis). Approximately 10⁵ unique diatom frustule shapes have been claimed to exist in nature. The frustules are composed of two valves that fit together like a petri-dish, connected to each other by one or more girdle bands. The frustule wall consists of a nanoporous assembly of silica nanoparticles. They absorb soluble silica from water even at extremely low concentrations and metabolize and deposit it as an external skeleton. Continued reproduction of a single parent

The injection of inert gas ions into solids: their trapping and escape

International Nuclear Information System (INIS)

Carter, G.; Armour, D.G.; Donnelly, S.E.; Ingram, D.C.; Webb, R.P.

1980-01-01

The first part of this contribution will review experimental studies of the trapping probabilities of ions injected into solids as a function of ion energy and indicate how the data can be modelled theoretically. It will be demonstrated that trapping is a two stage process, the first involving penetration into the solid and the second requiring atom dissolution and experimental evidence will be cited to show how the latter process may be dominant for light ions which create little radiation damage. For low ion fluences, injected atoms are generally trapped in isolation but as fluence increases gas-defect complexes are formed and it will be shown how post bombardment thermal evaluation studies can provide evidence for the growth of these complexes. Concomitant with trapping however, dissolved gas may be evolved from the solid by some form of sputtering process, sometimes by mechanisms much more efficient than congruent sputtering of the solid together with the trapped species. Measurements of the trapped atom concentration-ion fluence behaviour and of the evolution of one initially trapped species by bombardment with a second species provide information on the physical processes involved in trapped atom sputtering and upon the mechanism of gas incorporation saturation and experimental studies in this area, together with some first approximation theoretical investigations will be discussed. It will be shown that an important mechanism in dictating incorporation saturation, in addition to sputtering, is the atomic saturation of the solid by the implant. (author)

Radical Reactions in the Gas Phase: Recent Development and Application in Biomolecules

Directory of Open Access Journals (Sweden)

Yang Gao

2014-01-01

Full Text Available This review summarizes recent literature describing the use of gas phase radical reactions for structural characterization of complex biomolecules other than peptides. Specifically, chemical derivatization, in-source chemical reaction, and gas phase ion/ion reactions have been demonstrated as effective ways to generate radical precursor ions that yield structural informative fragments complementary to those from conventional collision-induced dissociation (CID. Radical driven dissociation has been applied to a variety of biomolecules including peptides, nucleic acids, carbohydrates, and phospholipids. The majority of the molecules discussed in this review see limited fragmentation from conventional CID, and the gas phase radical reactions open up completely new dissociation channels for these molecules and therefore yield high fidelity confirmation of the structures of the target molecules. Due to the extensively studied peptide fragmentation, this review focuses only on nonpeptide biomolecules such as nucleic acids, carbohydrates, and phospholipids.

Neutron-induced displacement damage analysis (with particular reference to zirconium)

International Nuclear Information System (INIS)

Woo, C.H.

1978-10-01

Neutron irradiation produces damage in a solid, initially in the form of atomic displacements. As a first step to understanding the effects of irradiation damage in reactor structural materials, information on the initial atomic displacements is necessary. The computer program DISPKAN, based on an extension and generalization of the program RICE, written at ORNL for such calculations, has been developed and installed on the CDC system at CRNL. Using neutron scattering data from ENDF/B files, DISPKAN performs a displacement and PKO analysis on the initial damage caused by neutrons from a given spectrum. The following quantities are calculated: the displacement rate per unit neutron flux, the PKO spectrum, the displacement spectrum, the fraction of PKO's with energy above T, the fraction of displacements produced by PKO's with energy above T, the average PKO energy, the average number of displacements produced per PKO, and the total number of PKO's produced per atom of the solid per unit fluence. The input and output formats of the program are explained. Sample runs are demonstrated. Results for zirconium, exposed to five neutron spectra typically available to experimentalist, are given to illustrate the spectral dependence of the initial displacement events. (author)

Improved calculation of displacements per atom cross section in solids by gamma and electron irradiation

Energy Technology Data Exchange (ETDEWEB)

Piñera, Ibrahin, E-mail: ipinera@ceaden.edu.cu [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, CEADEN, 30 St. 502, Playa 11300, Havana (Cuba); Cruz, Carlos M.; Leyva, Antonio; Abreu, Yamiel; Cabal, Ana E. [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, CEADEN, 30 St. 502, Playa 11300, Havana (Cuba); Espen, Piet Van; Remortel, Nick Van [University of Antwerp, CGB, Groenenborgerlaan 171, 2020 Antwerpen (Belgium)

2014-11-15

Highlights: • We present a calculation procedure for dpa cross section in solids under irradiation. • Improvement about 10–90% for the gamma irradiation induced dpa cross section. • Improvement about 5–50% for the electron irradiation induced dpa cross section. • More precise results (20–70%) for thin samples irradiated with electrons. - Abstract: Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10–90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5–50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20–70%) with respect to the previous studies.

Solid state reaction studies in Fe3O4–TiO2 system by diffusion couple method

International Nuclear Information System (INIS)

Ren, Zhongshan; Hu, Xiaojun; Xue, Xiangxin; Chou, Kuochih

2013-01-01

Highlights: •The solid state reactions of Fe2O3-TiO2 system was studied by the diffusion couple method. •Different products were formed by diffusion, and the FeTiO3 was more stable phase. •The inter-diffusion coefficients and diffusion activation energy were estimated. -- Abstract: The solid state reactions in Fe 3 O 4 –TiO 2 system has been studied by diffusion couple experiments at 1323–1473 K, in which the oxygen partial pressure was controlled by the CO–CO 2 gas mixture. The XRD analysis was used to confirm the phases of the inter-compound, and the concentration profiles were determined by electron probe microanalysis (EPMA). Based on the concentration profile of Ti, the inter-diffusion coefficients in Fe 3 O 4 phase, which were both temperature and concentration of Ti ions dependent, were calculated by the modified Boltzmann–Matano method. According to the relation between the thickness of diffusion layer and temperature, the diffusion coefficient of the Fe 3 O 4 –TiO 2 system was obtained. According to the Arrhenius equation, the estimated diffusion activation energy was about 282.1 ± 18.8 kJ mol −1

Attainment of chemical equilibrium in effusive beam sources of the heterogeneous reaction type

International Nuclear Information System (INIS)

Hildenbrand, D.L.

1979-01-01

Effusive beam sources derived from gas-solid reactions provide a very important pathway for widening the scope of high temperature thermodynamic studies, but the attainment of chemical equilibrium within these sources is problematical. Some of the underlying kinetic factors associated with the use of these sources are discussed. As one might expect, it is important to maximize the ratio of reactive surface area to exit orifice area. Equilibrium seems to be achieved more readily among the products of gas-solid reactions than among reactant and products, as suggested by the quasi-equilibrium model. Some experiences with the use of heterogeneous reaction sources are described, and two definitive tests for the establishment of equilibrium are outlined

Density functional theory study on water-gas-shift reaction over molybdenum disulfide

DEFF Research Database (Denmark)

Shi, X. R.; Wang, Shengguang; Hu, J.

2009-01-01

. The pathway for water-gas-shift reaction on both terminations has been carefully studied where the most favorable reaction path precedes the redox mechanism, namely the reaction takes place as follows: CO + H2O --> CO + OH + H --> CO + O + 2H --> CO2 + H-2. The most likely reaction candidates for the formate......Density functional theory calculations have been carried out to investigate the adsorption of reaction intermediates appearing during water-gas-shift reaction at the sulfur covered MoS2 (1 0 0)surfaces, Mo-termination with 37.5% S coverage and S-termination with 50% S coverage using periodic slabs...... species HCOO formation is the surface CO2 reaction with H as a side reaction of CO2 desorption on S-termination with 50% S coverage. The formed HCOO species will react further with adsorbed hydrogen yielding H2COO followed by breaking its C-O bond to form the surface CH2O and O species....

Development of solid-gas equilibrium propulsion system for small spacecraft

Science.gov (United States)

Chujo, Toshihiro; Mori, Osamu; Kubo, Yuki

2017-11-01

A phase equilibrium propulsion system is a kind of cold-gas jet in which the phase equilibrium state of the fuel is maintained in a tank and its vapor is ejected when a valve is opened. One such example is a gas-liquid equilibrium propulsion system that uses liquefied gas as fuel. This system was mounted on the IKAROS solar sail and has been demonstrated in orbit. The system has a higher storage efficiency and a lighter configuration than a high-pressure cold-gas jet because the vapor pressure is lower, and is suitable for small spacecraft. However, the system requires a gas-liquid separation device in order to avoid leakage of the liquid, which makes the system complex. As another example of a phase equilibrium propulsion system, we introduce a solid-gas equilibrium propulsion system, which uses a sublimable substance as fuel and ejects its vapor. This system has an even lower vapor pressure and does not require such a separation device, instead requiring only a filter to keep the solid inside the tank. Moreover, the system is much simpler and lighter, making it more suitable for small spacecraft, especially CubeSat-class spacecraft, and the low thrust of the system allows spacecraft motion to be controlled precisely. In addition, the thrust level can be controlled by controlling the temperature of the fuel, which changes the vapor pressure. The present paper introduces the concept of the proposed system, and describes ejection experiments and its evaluation. The basic function of the proposed system is demonstrated in order to verify its usefulness.

Isotope effects of reactions in quantum solids initiated by IR + UV lasers: quantum model simulations for Cl((2)P(3/2)) + X(2)(ν) → XCl + X in X(2) matrices (X = H, D).

Science.gov (United States)

Korolkov, M V; Manz, J; Schild, A

2010-09-16

Six isotope effects (i)-(vi) are discovered for the reactions Cl + H(2)(ν) → HCl + H in solid para-H(2) ( 1 ) versus Cl + D(2)(ν) → DCl + D in ortho-D(2) ( 2 ), by means of quantum reaction dynamics simulations, within the frame of our simple model ( J. Phys. Chem. A 2009 , 113 , 7630 . ). Experimentally, the reactions may be initiated for ν = 0 and ν ≥ 1, by means of "UV only" photodissociation of the matrix-isolated precursor, Cl(2), or by "IR + UV" coirradiation ( Kettwich , S. C. , Raston , P. L. , and Anderson , D. T. J. Phys. Chem. A 2009 , 113 , 7621 . ), respectively. Specifically, (i) various shape and Feshbach reaction resonances correlate with vibrational thresholds of reactants and products, due to the near-thermoneutrality and low barrier of the system. The energetic density of resonances increases as the square root of mass, from M(X) = M(H) to M(D). (ii) The state selective reaction ( 1 ), ν = 1, is supported by a shape resonance, whereas this type of resonance is absent in ( 2 ), ν = 1. As a consequence, time-resolved measurements should monitor different three-step versus direct error-function type evolutions of the formation of the products. (iii) The effective barrier is lower for reaction 1 , ν = 0, enhancing the tunneling rate, as compared to that for reaction 2 , ν = 0. (iv) For reference, the reaction probabilities P versus total energy E(tot) in the gas exhibit sharp resonance peaks or zigzag behaviors of the reaction probability P versus total energy, near the levels of resonances ( Persky , A. and Baer , M. J. Chem. Phys . 1974 , 60 , 133 . ). These features tend to be washed out and broadened for reaction 1 , and even more so for reaction 2 . For comparison, they disappear for reactions in classical solids. (v) The slopes of P versus E(tot) below the potential barrier increase more steeply for reaction 1 , ν = 0, than for reaction 2 , ν = 0. This enhances the tunneling rate of the heavier isotopomer, reaction 2 , ν = 0

Analytical solutions for non-linear conversion of a porous solid particle in a gas–I. Isothermal conversion

NARCIS (Netherlands)

Brem, Gerrit; Brouwers, J.J.H.

1990-01-01

Analytical description are presented for non-linear heterogeneous conversion of a porous solid particle reacting with a surrounding gas. Account has been taken of a reaction rate of general order with respect to gas concentration, intrinsic reaction surface area and pore diffusion, which change with

Well-to-Wheels Analysis of Compressed Natural Gas and Ethanol from Municipal Solid Waste

Energy Technology Data Exchange (ETDEWEB)

Lee, Uisung [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division; Han, Jeongwoo [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division; Wang, Michael [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division

2016-10-01

The amount of municipal solid waste (MSW) generated in the United States was estimated at 254 million wet tons in 2013, and around half of that generated waste was landfilled. There is a huge potential in recovering energy from that waste, since around 60% of landfilled material is biomass-derived waste that has high energy content. In addition, diverting waste for fuel production avoids huge fugitive emissions from landfills, especially uncontrolled CH₄ emissions, which are the third largest anthropogenic CH₄ source in the United States. Lifecycle analysis (LCA) is typically used to evaluate the environmental impact of alternative fuel production pathways. LCA of transportation fuels is called well-to-wheels (WTW) and covers all stages of the fuel production pathways, from feedstock recovery (well) to vehicle operation (wheels). In this study, the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET^®) model developed by Argonne National Laboratory is used to evaluate WTW greenhouse gas (GHG) emissions and fossil fuel consumption of waste-derived fuels. Two waste-to-energy (WTE) pathways have been evaluated – one for compressed natural gas (CNG) production using food waste via anaerobic digestion, and the other for ethanol production from yard trimmings via fermentation processes. Because the fuel production pathways displace current waste management practices (i.e., landfilling waste), we use a marginal approach that considers only the differences in emissions between the counterfactual case and the alternative fuel production case.

Modelling of non-catalytic reactors in a gas-solid trickle flow reactor: Dry, regenerative flue gas desulphurization using a silica-supported copper oxide sorbent

NARCIS (Netherlands)

Kiel, J.H.A.; Kiel, J.H.A.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

1992-01-01

A one-dimensional, two-phase dispersed plug flow model has been developed to describe the steady-state performance of a relatively new type of reactor, the gas-solid trickle flow reactor (GSTFR). In this reactor, an upward-flowing gas phase is contacted with as downward-flowing dilute solids phase

Minimization of steam requirements and enhancement of water-gas shift reaction with warm gas temperature CO2 removal

Science.gov (United States)

Siriwardane, Ranjani V; Fisher, II, James C

2013-12-31

The disclosure utilizes a hydroxide sorbent for humidification and CO.sub.2 removal from a gaseous stream comprised of CO and CO.sub.2 prior to entry into a water-gas-shift reactor, in order to decrease CO.sub.2 concentration and increase H.sub.2O concentration and shift the water-gas shift reaction toward the forward reaction products CO.sub.2 and H.sub.2. The hydroxide sorbent may be utilized for absorbtion of CO.sub.2 exiting the water-gas shift reactor, producing an enriched H.sub.2 stream. The disclosure further provides for regeneration of the hydroxide sorbent at temperature approximating water-gas shift conditions, and for utilizing H.sub.2O product liberated as a result of the CO.sub.2 absorption.

Observation of an Aligned Gas - Solid "Eutectic" during Controlled Directional Solidification Aboard the International Space Station - Comparison with Ground-based Studies

Science.gov (United States)

Grugel, R. N.; Anilkumar, A.

2005-01-01

Direct observation of the controlled melting and solidification of succinonitrile was conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) in an atmosphere of nitrogen at 450 millibar pressure for eventual processing in the Pore Formation and Mobility Investigation (PFMI) apparatus in the glovebox facility (GBX) on board the ISS. Real time visualization during controlled directional melt back of the sample showed nitrogen bubbles emerging from the interface and moving through the liquid up the imposed temperature gradient. Over a period of time these bubbles disappear by dissolving into the melt. Translation is stopped after melting back of about 9 cm of the sample, with an equilibrium solid-liquid interface established. During controlled re-solidification, aligned tubes of gas were seen growing perpendicular to the planar solid/liquid interface, inferring that the nitrogen previously dissolved into the liquid SCN was now coming out at the solid/liquid interface and forming the little studied liquid = solid + gas eutectic-type reaction. The observed structure is evaluated in terms of spacing dimensions, interface undercooling, and mechanisms for spacing adjustments. Finally, the significance of processing in a microgravity environment is ascertained in view of ground-based results.

Prolonged displacement may compromise resilience in Eritrean ...

African Journals Online (AJOL)

Objective: to assess the impact of prolonged displacement on the resilience of Eritrean mothers. Methods: an adapted SOC scale (short form) was administered. Complementary qualitative data were gathered from study participants' spontaneous reactions to and commentaries on the SOC scale. Results: Displaced ...

Miscible fluid displacement: an answer to increasing oil recovery

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, N R; Rivera, R J

1976-01-01

This study presents the state of the art on miscible and miscible-type processes. It is well known that when these processes are applied under ideal laboratory conditions, the oil recovery obtained from linear cores approaches 100% of the total oil contained in the porous structure which is contacted by the displacing fluids. In the past few years, a worldwide shortage of crude oil supplies produced an increased interest in new oil recovery methods. Because of this situation, the oil industry turned its eyes back toward the miscible processes. This study discusses the following miscible fluid displacement processes: (1) high-pressure dry gas displacement; (2) enriched gas displacement; (3) GLP slug flooding; and (4) carbon dioxide displacement. In addition to the processes aforementioned, this work presents the main features of the micellar solution flooding process. (17 refs.)

1D to 3D diffusion-reaction kinetics of defects in crystals

DEFF Research Database (Denmark)

Trinkaus, H.; Heinisch, H.L.; Barashev, A.V.

2002-01-01

Microstructural features evolving in crystalline solids from diffusion-reaction kinetics of mobile components depend crucially on the dimension of the underlying diffusion process which is commonly assumed to be three-dimensional (3D). In metals, irradiation-induced displacement cascades produce...... clusters of self-interstitials performing 1D diffusion. Changes between equivalent 1D diffusion paths and transversal diffusion result in diffusion-reaction kinetics between one and three dimensions. An analytical approach suggests a single-variable function (master curve) interpolating between the 1D...

Direct determination of enthalpies of solid phase reactions by immersion method; Determination directe des enthalpies de reaction en phase solide par une methode de plongee

Energy Technology Data Exchange (ETDEWEB)

Roux, A; Richard, M; Eyraud, L; Stevanovic, M; Elston, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

It is not generally possible to measure the enthalpy change corresponding to solid phase reactions using the dynamic differential thermal analysis method because these reactions are usually too slow at the temperature of operation of present equipment. A ballistic differential thermal analysis apparatus has been developed which is based on an immersion-compensation method; it overcomes the difficulties previously encountered. This apparatus has been used after calibration for determining the enthalpies of formation of calcium and cadmium titanates. and also the Wigner energies of BeO, MgO and Al{sub 2}O{sub 3} samples irradiated at variable dose at a temperature of under 100 deg. C. (authors) [French] Il n'est generalement pas possible de mesurer la variation d'enthalpie correspondant aux reactions en phase solide par la methode d'analyse thermique differentielle dynamique. En effet, ces reactions sont le plus souvent trop lentes aux temperatures d'utilisation des dispositifs actuels. Un appareil d'analyse thermique differentielle balistique, base sur une methode de plongee avec compensation, a ete mis au point et permet de surmonter les difficultes precedentes. Apres etalonnages, cet appareil a ete utilise pour la determination des enthalpies de formation du titanate de calcium et du titanate de cadmium ainsi que pour celle des energies Wigner emmagasinees dans des echantillons de BeO, MgO et Al{sub 2}O{sub 3} irradies a une temperature inferieure a 100 deg. C et a differentes doses. (auteurs)

In Situ Apparatus to Study Gas-Metal Reactions and Wettability at High Temperatures for Hot-Dip Galvanizing Applications

Science.gov (United States)

Koltsov, A.; Cornu, M.-J.; Scheid, J.

2018-02-01

The understanding of gas-metal reactions and related surface wettability at high temperatures is often limited due to the lack of in situ surface characterization. Ex situ transfers at low temperature between annealing furnace, wettability device, and analytical tools induce noticeable changes of surface composition distinct from the reality of the phenomena.Therefore, a high temperature wettability device was designed in order to allow in situ sample surface characterization by x-rays photoelectron spectroscopy after gas/metal and liquid metal/solid metal surface reactions. Such airless characterization rules out any contamination and oxidation of surfaces and reveals their real composition after heat treatment and chemical reaction. The device consists of two connected reactors, respectively, dedicated to annealing treatments and wettability measurements. Heat treatments are performed in an infrared lamp furnace in a well-controlled atmosphere conditions designed to reproduce gas-metal reactions occurring during the industrial recrystallization annealing of steels. Wetting experiments are carried out in dispensed drop configuration with the precise control of the deposited droplets kinetic energies. The spreading of drops is followed by a high-speed CCD video camera at 500-2000 frames/s in order to reach information at very low contact time. First trials have started to simulate phenomena occurring during recrystallization annealing and hot-dip galvanizing on polished pure Fe and FeAl8 wt.% samples. The results demonstrate real surface chemistry of steel samples after annealing when they are put in contact with liquid zinc alloy bath during hot-dip galvanizing. The wetting results are compared to literature data and coupled with the characterization of interfacial layers by FEG-Auger. It is fair to conclude that the results show the real interest of such in situ experimental setup for interfacial chemistry studies.

Solid-state polymerisation via [2+2] cycloaddition reaction involving coordination polymers.

Science.gov (United States)

Medishetty, Raghavender; Park, In-Hyeok; Lee, Shim Sung; Vittal, Jagadese J

2016-03-14

Highly crystalline metal ions containing organic polymers are potentially useful to manipulate the magnetic and optical properties to make advanced multifunctional materials. However, it is challenging to synthesise monocrystalline metal complexes of organic polymers and single-phase hybrid materials made up of both coordination and organic polymers by traditional solution crystallisation. This requires an entirely different approach in the solid-state by thermal or photo polymerisation of the ligands. Among the photochemical methods available, [2+2] cycloaddition reaction has been recently employed to generate cyclobutane based coordination polymers from the metal complexes. Cyclobutane polymers have also been integrated into coordination polymers in this way. Recent advancements in the construction of polymeric chains of cyclobutane rings through photo-dimerisation reaction in the monocrystalline solids containing metal complexes, coordination polymers and metal-organic framework structures are discussed here.

Synthesisofc-lifepo4 composite by solid state reaction method

Science.gov (United States)

Rahayu, I.; Hidayat, S.; Noviyanti, A. R.; Rakhmawaty, D.; Ernawati, E.

2017-02-01

In this research, the enhancement of LiFePO4 conductivity was conducted by doping method with carbon materials. Carbon-based materials were obtained from the mixture of sucrose, and the precursor of LiH2PO4 and α-Fe2O3 was synthesized by solid state reaction. Sintering temperature was varied at 700°C, 800°C, 900°C and 1,000°C. The result showed that C-LiFePO4 could be synthesized by using solid state reaction method. Based on the XRD and FTIR spectrums, C-LiFePO4 can be identified as the type of crystal, characterized by the appearance of sharp signal on (011), (211) and typical peak of LiFePO4 materials. The result of conductivity measurement from C-LiFePO4 at sintering temperature of 900°C and 1,000°C was 2×10-4 S/cm and 4×10-4S/cm, respectively. The conductivity value at sintering temperature of 700°C and 800°C was very small (<10-6 S/cm), which cannot be measured by the existing equipment.

High Temperature Gas-to-Gas Heat Exchanger Based on a Solid Intermediate Medium

Directory of Open Access Journals (Sweden)

R. Amirante

2014-04-01

Full Text Available This paper proposes the design of an innovative high temperature gas-to-gas heat exchanger based on solid particles as intermediate medium, with application in medium and large scale externally fired combined power plants fed by alternative and dirty fuels, such as biomass and coal. An optimization procedure, performed by means of a genetic algorithm combined with computational fluid dynamics (CFD analysis, is employed for the design of the heat exchanger: the goal is the minimization of its size for an assigned heat exchanger efficiency. Two cases, corresponding to efficiencies equal to 80% and 90%, are considered. The scientific and technical difficulties for the realization of the heat exchanger are also faced up; in particular, this work focuses on the development both of a pressurization device, which is needed to move the solid particles within the heat exchanger, and of a pneumatic conveyor, which is required to deliver back the particles from the bottom to the top of the plant in order to realize a continuous operation mode. An analytical approach and a thorough experimental campaign are proposed to analyze the proposed systems and to evaluate the associated energy losses.

Monitoring mass transport in heterogeneously catalyzed reactions by field-gradient NMR for assessing reaction efficiency in a single pellet

Science.gov (United States)

Buljubasich, L.; Blümich, B.; Stapf, S.

2011-09-01

An important aspect in assessing the performance of a catalytically active reactor is the accessibility of the reactive sites inside the individual pellets, and the mass transfer of reactants and products to and from these sites. Optimal design often requires a suitable combination of micro- and macropores in order to facilitate mass transport inside the pellet. In an exothermic reaction, fluid exchange between the pellet and the surrounding medium is enhanced by convection, and often by the occurrence of gas bubbles. Determining mass flow in the vicinity of a pellet thus represents a parameter for quantifying the reaction efficiency and its dependence on time or external reaction conditions. Field gradient Nuclear Magnetic Resonance (NMR) methods are suggested as a tool for providing parameters sensitive to this mass flow in a contact-free and non-invasive way. For the example of bubble-forming hydrogen peroxide decomposition in an alumina pellet, the dependence of the mean-squared displacement of fluid molecules on spatial direction, observation time and reaction time is presented, and multi-pulse techniques are employed in order to separate molecular displacements from coherent and incoherent motion on the timescale of the experiment. The reaction progress is followed until the complete decomposition of H 2O 2.

Development of acoustic flow instruments for solid/gas pipe flows

International Nuclear Information System (INIS)

Sheen, S.H.; Raptis, A.C.

1986-05-01

Two nonintrusive acoustic flow sensing techniques are reported. One technique, passive in nature, simply measures the bandpassed acoustic noise level produced by particle/particle and particle/wall collisions. The noise levels, given in true RMS voltages or in autocorrelations, show a linear relationship to particle velocity but increase with solid concentration. Therefore, the passive technique requires calibration and a separate measure of solid concentration before it can be used to monitor the particle velocity. The second technique is based on the active cross-correlation principle. It measures particle velocity directly by correlating flow-related signatures at two sensing stations. The velocity data obtained by this technique are compared with measurements by a radioactive-particle time-of-flight (TOF) method. A multiplier of 1.53 is required to bring the acoustic data into agreement with the radioactive TOF result. The difference may originate from the difference in flow fields where particles are detected. The radioactive method senses particles mainly in the turbulent region and essentially measures average particle velocity across the pipe, while the acoustic technique detects particles near the pipe wall, and so measures the particle velocity in the viscous sublayer. Both techniques were tested in flows of limestone and air and 1-mm glass beads and air at the Argonne National Laboratory Solid/Gas Test Facility (SGFTF). The test matrix covered solid velocities of 20 to 30 m/s in a 2-in. pipe and solid-to-gas loading ratios of 6 to 22. 37 refs., 19 figs., 4 tabs

Measurement of Gas Velocities in the Presence of Solids in the Riser of a Cold Flow Circulating Fluidized Bed

International Nuclear Information System (INIS)

Spenik, J.; Ludlow, J.C.; Compston, R.; Breault, R.W.

2007-01-01

The local gas velocity and the intensity of the gas turbulence in a gas/solid flow are a required measurement in validating the gas and solids flow structure predicted by computational fluid dynamic (CFD) models in fluid bed and transport reactors. The high concentration and velocities of solids, however, make the use of traditional gas velocity measurement devices such as pitot tubes, hot wire anemometers and other such devices difficult. A method of determining these velocities has been devised at the National Energy Technology Laboratory employing tracer gas. The technique developed measures the time average local axial velocity gas component of a gas/solid flow using an injected tracer gas which induces changes in the heat transfer characteristics of the gas mixture. A small amount of helium is injected upstream a known distance from a self-heated thermistor. The thermistor, protected from the solids by means of a filter, is exposed to gases that are continuously extracted from the flow. Changes in the convective heat transfer characteristics of the gas are indicated by voltage variations across a Wheatstone bridge. When pulsed injections of helium are introduced to the riser flow the change in convective heat transfer coefficient of the gas can be rapidly and accurately determined with this instrument. By knowing the separation distance between the helium injection point and the thermistor extraction location as well as the time delay between injection and detection, the gas velocity can easily be calculated. Variations in the measured gas velocities also allow the turbulence intensity of the gas to be estimated

Experimental and theoretical studies on the gas/solid/gas transformation cycle in extraterrestrial environments

Science.gov (United States)

Cottin, Hervé; Gazeau, Marie-Claire; Chaquin, Patrick; Raulin, François; Bénilan, Yves

2001-12-01

The ubiquity of molecular material in the universe, from hydrogen to complex organic matter, is the result of intermixed physicochemical processes that have occurred throughout history. In particular, the gas/solid/gas phase transformation cycle plays a key role in chemical evolution of organic matter from the interstellar medium to planetary systems. This paper focuses on two examples that are representative of the diversity of environments where such transformations occur in the Solar System: (1) the photolytic evolution from gaseous to solid material in methane containing planetary atmospheres and (2) the degradation of high molecular weight compounds into gas phase molecules in comets. We are currently developing two programs which couple experimental and theoretical studies. The aim of this research is to provide data necessary to build models in order to better understand (1) the photochemical evolution of Titan's atmosphere, through a laboratory program to determine quantitative spectroscopic data on long carbon chain molecules (polyynes) obtained in the SCOOP program (French acronym for Spectroscopy of Organic Compounds Oriented for Planetology), and (2) the extended sources in comets, through a laboratory program of quantitative studies of photochemical and thermal degradation processes on relevant polymers (e.g., Polyoxymethylene) by the SEMAPhOrE Cometaire program (French acronym for Experimental Simulation and Modeling Applied to Organic Chemistry in Cometary Environment).

Modelling of interactions between variable mass and density solid particles and swirling gas stream

International Nuclear Information System (INIS)

Wardach-Święcicka, I; Kardaś, D; Pozorski, J

2011-01-01

The aim of this work is to investigate the solid particles - gas interactions. For this purpose, numerical modelling was carried out by means of a commercial code for simulations of two-phase dispersed flows with the in-house models accounting for mass and density change of solid phase. In the studied case the particles are treated as spherical moving grains carried by a swirling stream of hot gases. Due to the heat and mass transfer between gas and solid phase, the particles are losing their mass and they are changing their volume. Numerical simulations were performed for turbulent regime, using two methods for turbulence modelling: RANS and LES.

Thermal-Flow Code for Modeling Gas Dynamics and Heat Transfer in Space Shuttle Solid Rocket Motor Joints

Science.gov (United States)

Wang, Qunzhen; Mathias, Edward C.; Heman, Joe R.; Smith, Cory W.

2000-01-01

A new, thermal-flow simulation code, called SFLOW. has been developed to model the gas dynamics, heat transfer, as well as O-ring and flow path erosion inside the space shuttle solid rocket motor joints by combining SINDA/Glo, a commercial thermal analyzer. and SHARPO, a general-purpose CFD code developed at Thiokol Propulsion. SHARP was modified so that friction, heat transfer, mass addition, as well as minor losses in one-dimensional flow can be taken into account. The pressure, temperature and velocity of the combustion gas in the leak paths are calculated in SHARP by solving the time-dependent Navier-Stokes equations while the heat conduction in the solid is modeled by SINDA/G. The two codes are coupled by the heat flux at the solid-gas interface. A few test cases are presented and the results from SFLOW agree very well with the exact solutions or experimental data. These cases include Fanno flow where friction is important, Rayleigh flow where heat transfer between gas and solid is important, flow with mass addition due to the erosion of the solid wall, a transient volume venting process, as well as some transient one-dimensional flows with analytical solutions. In addition, SFLOW is applied to model the RSRM nozzle joint 4 subscale hot-flow tests and the predicted pressures, temperatures (both gas and solid), and O-ring erosions agree well with the experimental data. It was also found that the heat transfer between gas and solid has a major effect on the pressures and temperatures of the fill bottles in the RSRM nozzle joint 4 configuration No. 8 test.

Solid state reaction in alumina nanoparticles/LZSA glass-ceramic composites

International Nuclear Information System (INIS)

Montedo, O.K.; Oliveira, A.N. de; Raupp-Pereira, F.

2016-01-01

Full text: The aim of this work is to present results related to solid state reactions on LZSA glass-ceramic composites containing alumina reinforcement nano-particles. A LZSA (Li2O-ZrO2-SiO2-Al2O3) glass-ceramic has been prepared by sintering of powders and characterized. Composites containing 0 to 77 vol.% of alumina nanoparticles (27-43 nm APS, 35 m2.g-1 SSA) and a 16.9Li2O•5.0ZrO2•65.1SiO2•8.6Al2O3 glass-ceramic matrix have been prepared. X-ray diffractometry studies have been performed in order of investigating the solid state reactions occurring in LZSA-based composites. Results of the XRD patterns have been related to the coefficient of thermal expansion (CTE), Young modulus, and dielectric constant, showing that, in comparison with the glass-ceramic composition, the composites showed a decrease of CTE with the alumina concentration increasing, due to the increasing of beta-spodumeness formation (solid solution of beta-spodumene, Li2O.Al2O3.4-10SiO2). The performance of the glass-ceramic was improved with the alumina nano-particles addition, showing potential of using in the preparation of Low Thermal Co-fired Ceramics (LTCC). (author)

In Situ Environmental TEM in Imaging Gas and Liquid Phase Chemical Reactions for Materials Research.

Science.gov (United States)

Wu, Jianbo; Shan, Hao; Chen, Wenlong; Gu, Xin; Tao, Peng; Song, Chengyi; Shang, Wen; Deng, Tao

2016-11-01

Gas and liquid phase chemical reactions cover a broad range of research areas in materials science and engineering, including the synthesis of nanomaterials and application of nanomaterials, for example, in the areas of sensing, energy storage and conversion, catalysis, and bio-related applications. Environmental transmission electron microscopy (ETEM) provides a unique opportunity for monitoring gas and liquid phase reactions because it enables the observation of those reactions at the ultra-high spatial resolution, which is not achievable through other techniques. Here, the fundamental science and technology developments of gas and liquid phase TEM that facilitate the mechanistic study of the gas and liquid phase chemical reactions are discussed. Combined with other characterization tools integrated in TEM, unprecedented material behaviors and reaction mechanisms are observed through the use of the in situ gas and liquid phase TEM. These observations and also the recent applications in this emerging area are described. The current challenges in the imaging process are also discussed, including the imaging speed, imaging resolution, and data management. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of the number of phenyl groups per molecule on the reactivity of hydroxyl or carboxyl group in hydrogen-isotope exchange reaction

International Nuclear Information System (INIS)

Okada, Minoru; Imaizumi, Hiroshi; Oguma, Shuichi

1989-01-01

Hydrogen-exchange reactions in solid alcohols (or solid carboxylic acids) which contain phenyl group(s) in each molecule have been observed in a gas-solid system or liquid-solid system at 40 ≅ 80deg C. The data thus obtained have been analyzed by using the A''-McKay plot method, and 'the acidities based on kinetic logic' have been obtained for those compounds. From the acidities the following four characteristics have been determined. (1) The acidity increases with increases of temperature. (2) The reactivities of carboxylic acids are larger than those of alcohols at any temperature. (3) The effect of the number of phenyl groups on the reactivity of the functional group in the molecule in question is fairly large. (4) Acidity based on kinetic logic can be applied not only to gas-solid reactions, but also to liquid-solid reactions. (orig.)

Anomalous low-temperature desorption from preirradiated rare gas solids

International Nuclear Information System (INIS)

Savchenko, E.V.; Gumenchuk, G.B.; Yurtaeva, E.M.; Belov, A.G.; Khyzhniy, I.V.; Frankowski, M.; Beyer, M.K.; Smith-Gicklhorn, A.M.; Ponomaryov, A.N.; Bondybey, V.E.

2005-01-01

The role for the exciton-induced defects in the stimulation of anomalous low-temperature desorption of the own lattice atoms from solid Ar and Ne preirradiated by an electron beam is studied. The free electrons from shallow traps-structural defects-was monitored by the measurements of a yield of the thermally induced exoelectron emission (TSEE). The reaction of recombination of self-trapped holes with electrons is considered as a source of energy needed for the desorption of atoms from the surface of preirradiated solids. A key part of the exciton-induced defects in the phenomenon observed is demonstrated

Validation of mechanistic models for gas precipitation in solids during postirradiation annealing experiments

Science.gov (United States)

Rest, J.

1989-12-01

A number of different phenomenological models for gas precipitation in solids during postirradiation annealing experiments have been proposed. Validation of such mechanistic models for gas release and swelling is complicated by the use of data containing large systematic errors, and phenomena characterized by synergistic effects as well as uncertainties in materials properties. Statistical regression analysis is recommended for the selection of a reasonably well characterized data base for gas release from irradiated fuel under transient heating conditions. It is demonstrated that an appropriate data selection method is required in order to realistically examine the impact of differing descriptions of the phenomena, and uncertainties in selected materials properties, on the validation results. The results of the analysis show that the kinetics of gas precipitation in solids depend on bubble overpressurization effects and need to be accounted for during the heatup phase of isothermal heating experiments. It is shown that if only the total gas release values (as opposed to time-dependent data) were available, differentiation between different gas precipitation models would be ambiguous. The observed sustained increase in the fractional release curve at relatively high temperatures after the total precipitation of intragranular gas in fission gas bubbles is ascribed to the effects of a grain-growth/grain-boundary sweeping mechanism.

Validation of mechanistic models for gas precipitation in solids during postirradiation annealing experiments

International Nuclear Information System (INIS)

Rest, J.

1989-01-01

A number of different phenomenological models for gas precipitation in solids during postirradiation annealing experiments have been proposed. Validation of such mechanistic models for gas release and swelling is complicated by the use of data containing large systematic errors, and phenomena characterized by synergistic effects as well as uncertainties in materials properties. Statistical regression analysis is recommended for the selection of a reasonably well characterized data base for gas release from irradiated fuel under transient heating conditions. It is demonstrated that an appropriate data selection method is required in order to realistically examine the impact of differing descriptions of the phenomena, and uncertainties in selected materials properties, on the validation results. The results of the analysis show that the kinetics of gas precipitation in solid depend on bubble overpressurization effects and need to be accounted for during the heatup phase of isothermal heating experiments. It is shown that if only the total gas release values (as opposed to time-dependent data) were available, differentiation between different gas precipitation models would be ambiguous. The observed sustained increase in the fractional release curve at relatively high temperatures after the total precipitation of intragranular gas in fission gas bubbles is ascribed to the effects of a grain-growth/grain-boundary sweeping mechanism. (orig.)

Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries.

Science.gov (United States)

Prentice, Boone M; McLuckey, Scott A

2013-02-01

Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field.

Modeled heating and surface erosion comparing motile (gas borne) and stationary (surface coating) inert particle additives

International Nuclear Information System (INIS)

Buckingham, A.C.; Siekhaus, W.J.

1982-01-01

The unsteady, non-similar, chemically reactive, turbulent boundary layer equations are modified for gas plus dispersed solid particle mixtures, for gas phase turbulent combustion reactions and for heterogeneous gas-solid surface erosive reactions. The exterior (ballistic core) edge boundary conditions for the solutions are modified to include dispersed particle influences on core propellant combustion-generated turbulence levels, combustion reactants and products, and reaction-induced, non-isentropic mixture states. The wall surface (in this study it is always steel) is considered either bare or coated with a fixed particle coating which is conceptually non-reactive, insulative, and non-ablative. Two families of solutions are compared. These correspond to: (1) consideration of gas-borne, free-slip, almost spontaneously mobile (motile) solid particle additives which influence the turbulent heat transfer at the uncoated steel surface and, in contrast, (2) consideration of particle-free, gas phase turbulent heat transfer to the insulated surface coated by stationary particles. Significant differences in erosive heat transfer are found in comparing the two families of solutions over a substantial range of interior ballistic flow conditions. The most effective influences on reducing erosive heat transfer appear to favor mobile, gas-borne particle additives

The effect of gas double-dynamic on mass distribution in solid-state fermentation.

Science.gov (United States)

Chen, Hong-Zhang; Zhao, Zhi-Min; Li, Hong-Qiang

2014-05-10

The mass distribution regularity in substrate of solid-state fermentation (SSF) has rarely been reported due to the heterogeneity of solid medium and the lack of suitable instrument and method, which limited the comprehensive analysis and enhancement of the SSF performance. In this work, the distributions of water, biomass, and fermentation product in different medium depths of SSF were determined using near-infrared spectroscopy (NIRS) and the developed models. Based on the mass distribution regularity, the effects of gas double-dynamic on heat transfer, microbial growth and metabolism, and product distribution gradient were systematically investigated. Results indicated that the maximum temperature of substrate and the maximum carbon dioxide evolution rate (CER) were 39.5°C and 2.48mg/(hg) under static aeration solid-state fermentation (SASSF) and 33.9°C and 5.38mg/(hg) under gas double-dynamic solid-state fermentation (GDSSF), respectively, with the environmental temperature for fermentation of 30±1°C. The fermentation production (cellulase activity) ratios of the upper, middle, and lower levels were 1:0.90:0.78 at seventh day under SASSF and 1:0.95:0.89 at fifth day under GDSSF. Therefore, combined with NIRS analysis, gas double-dynamic could effectively strengthen the solid-state fermentation performance due to the enhancement of heat transfer, the stimulation of microbial metabolism and the increase of the homogeneity of fermentation products. Copyright © 2014 Elsevier Inc. All rights reserved.

Revisiting low-fidelity two-fluid models for gas-solids transport

Science.gov (United States)

Adeleke, Najeem; Adewumi, Michael; Ityokumbul, Thaddeus

2016-08-01

Two-phase gas-solids transport models are widely utilized for process design and automation in a broad range of industrial applications. Some of these applications include proppant transport in gaseous fracking fluids, air/gas drilling hydraulics, coal-gasification reactors and food processing units. Systems automation and real time process optimization stand to benefit a great deal from availability of efficient and accurate theoretical models for operations data processing. However, modeling two-phase pneumatic transport systems accurately requires a comprehensive understanding of gas-solids flow behavior. In this study we discuss the prevailing flow conditions and present a low-fidelity two-fluid model equation for particulate transport. The model equations are formulated in a manner that ensures the physical flux term remains conservative despite the inclusion of solids normal stress through the empirical formula for modulus of elasticity. A new set of Roe-Pike averages are presented for the resulting strictly hyperbolic flux term in the system of equations, which was used to develop a Roe-type approximate Riemann solver. The resulting scheme is stable regardless of the choice of flux-limiter. The model is evaluated by the prediction of experimental results from both pneumatic riser and air-drilling hydraulics systems. We demonstrate the effect and impact of numerical formulation and choice of numerical scheme on model predictions. We illustrate the capability of a low-fidelity one-dimensional two-fluid model in predicting relevant flow parameters in two-phase particulate systems accurately even under flow regimes involving counter-current flow.

Municipal Solid Waste Gasification Plant Integrated With SOFC and Gas Turbine

DEFF Research Database (Denmark)

Bellomare, Filippo; Rokni, Masoud

2012-01-01

An interesting source of producing energy with low pollutants emission and reduced environmental impact are the biomasses; particularly using Municipal Solid Waste (MSW) as fuel, can be a competitive solution not only to produce energy with negligible costs but also to decrease the storage...... in landfills. A Municipal Solid Waste Gasification Plant Integrated with Solid Oxide Fuel Cell (SOFC) and Gas Turbine (GT) has been studied and the plant is called IGSG (Integrated Gasification SOFC and GT). Gasification plant is fed by MSW to produce syngas by which the anode side of a SOFC is fed wherein...

A study of paint sludge deactivation by pyrolysis reactions

Directory of Open Access Journals (Sweden)

Muniz L.A.R.

2003-01-01

Full Text Available The production of large quantities of paint sludge is a serious environmental problem. This work evaluates the use of pyrolysis reaction as a process for deactivating paint sludge that generates a combustible gas phase, a solvent liquid phase and an inert solid phase. These wastes were classified into three types: water-based solvent (latex resin and solvents based on their resins (alkyd and polyurethane. An electrically heated stainless steel batch reactor with a capacity of 579 mL and a maximum pressure of 30 atm was used. Following the reactor, a flash separator, which was operated at atmospheric pressure, partially condensed and separated liquid and gas products. Pressure and temperature were monitored on-line by a control and data acquisition system, which adjusted the heating power supplied to the pyrolysis reactor. Reactions followed an experimental design with two factors (reaction time and temperature and three levels (10, 50 and 90 minutes; 450, 550 and 650degreesC. The response variables were liquid and solid masses and net heat of combustion. The optimal operational range for the pyrolysis process was obtained for each response variable. A significant reduction in total mass of solid waste was obtained.

Hydrodynamic boundary conditions for one-component liquid-gas flows on non-isothermal solid substrates

KAUST Repository

Xu, Xinpeng

2012-01-01

Recently, liquid-gas flows related to droplets, bubbles, and thin films on solid surfaces with thermal and wettability gradients have attracted widespread attention because of the many physical processes involved and their promising potential applications in biology, chemistry, and industry. Various new physical effects have been discovered at fluid-solid interfaces by experiments and molecular dynamics simulations, e.g., fluid velocity slip, temperature slip (Kapitza resistance), mechanical-thermal cross coupling, etc. There have been various models and theories proposed to explain these experimental and numerical observations. However, to the best of our knowledge,a continuum hydrodynamic model capable of predicting the temperature and velocity profiles of liquid-gas flows on non-isothermal, heterogeneous solid substrates is still absent. The purpose of this work is to construct a continuum model for simulating the liquid-gas flows on solid surfaces that are flat and rigid, and may involve wettability gradients and thermal gradients. This model is able to describe fluid velocity slip, temperature slip, and mechanical-thermal coupling that may occur at fluid-solid interfaces. For this purpose, we first employ the diffuse interface modeling to formulate the hydrodynamic equations for one-component liquid-gas flows in the bulk region. This reproduces the dynamic van der Waals theory of Onuki [Phys. Rev. Lett., 94: 054501, 2005]. We then extendWaldmann\\'s method [Z. Naturforsch. A, 22: 1269-1280, 1967] to formulate the boundary conditions at the fluid-solid interface that match the hydrodynamic equations in the bulk. The effects of the solid surface curvature are also briefly discussed in the appendix. The guiding principles of our model derivation are the conservation laws and the positive definiteness of entropy production together with the Onsager reciprocal relation. The derived model is self-consistent in the sense that the boundary conditions are

Non-intrusive measurement and hydrodynamics characterization of gas-solid fluidized beds: a review

Science.gov (United States)

Sun, Jingyuan; Yan, Yong

2016-11-01

Gas-solid fluidization is a well-established technique to suspend or transport particles and has been applied in a variety of industrial processes. Nevertheless, our knowledge of fluidization hydrodynamics is still limited for the design, scale-up and operation optimization of fluidized bed reactors. It is, therefore, essential to characterize the two-phase flow behaviours in gas-solid fluidized beds and monitor the fluidization processes for control and optimization. A range of non-intrusive techniques have been developed or proposed for measuring the fluidization dynamic parameters and monitoring the flow status without disturbing or distorting the flow fields. This paper presents a comprehensive review of the non-intrusive measurement techniques and the current state of knowledge and experience in the characterization and monitoring of gas-solid fluidized beds. These techniques are classified into six main categories as per sensing principles, electrostatic, acoustic emission and vibration, visualization, particle tracking, laser Doppler anemometry and phase Doppler anemometry as well as pressure-fluctuation methods. Trends and future developments in this field are also discussed.

CuInSe2 nano-crystallite reaction kinetics using solid state reaction from Cu2Se and In2Se3 powders

International Nuclear Information System (INIS)

Hsiang, Hsing-I; Lu, Li-Hsin; Chang, Yu-Lun; Ray, Dahtong; Yen, Fu-Su

2011-01-01

Highlights: → CuInSe 2 phase increased gradually accompanied with a decrease in γ-In 2 Se 3 and no intermediate phase during calcination. → CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a one-dimensional diffusion-controlled reaction with apparent activation energy of about 122.5 kJ/mol. → The solid reaction kinetics may be dominated by the diffusion of In 3+ ions. - Abstract: The reaction mechanism and CuInSe 2 formation kinetics using a solid state reaction from Cu 2 Se and In 2 Se 3 powders synthesized using a heating up process were investigated using X-ray diffractomy (XRD) and transmission electron microscopy (TEM). It was observed that the CuInSe 2 phase increased gradually, accompanied with a decrease in γ-In 2 Se 3 with no intermediate phase as the calcination temperature and soaking time were increased. The reaction kinetics was analyzed using the Avrami and polynomial kinetic model, suggesting that CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a diffusion-controlled reaction with an apparent activation energy of about 122.5-182.3 kJ/mol. Cu 2 Se and In 2 Se 3 phases react and directly transform into CIS without the occurrence of any intermediate phase and the size of the newly formed CuInSe 2 crystallites was close to that of the Cu 2 Se reactant particle based on the TEM results, which indicated that the solid reaction kinetics may be dominated by the diffusion of In 3+ ions.

Comparison Between Conventional Design and Cathode Gas Recirculation Design of a Direct-Syngas Solid Oxide Fuel Cell–Gas Turbine Hybrid Systems Part I: Design Performance

Directory of Open Access Journals (Sweden)

Vahid Azami

2017-06-01

Keywords: Solid oxide fuel cell, Gas turbine, Cathode gas recirculation, Exergy. Article History: Received Feb 23rd 2017; Received in revised form May 26th 2017; Accepted June 1st 2017; Available online How to Cite This Article: Azami, V, and Yari, M. (2017 Comparison between conventional design and cathode gas recirculation design of a direct-syngas solid oxide fuel cell–gas turbine hybrid systems part I: Design performance. International Journal of Renewable Energy Develeopment, 6(2, 127-136. https://doi.org/10.14710/ijred.6.2.127-136

Simulations of small solid accretion on to planetesimals in the presence of gas

Science.gov (United States)

Hughes, A. G.; Boley, A. C.

2017-12-01

The growth and migration of planetesimals in a young protoplanetary disc are fundamental to planet formation. In all models of early growth, there are several processes that can inhibit grains from reaching larger sizes. Nevertheless, observations suggest that growth of planetesimals must be rapid. If a small number of 100 km sized planetesimals do manage to form in the disc, then gas drag effects could enable them to efficiently accrete small solids from beyond their gravitationally focused cross-section. This gas-drag-enhanced accretion can allow planetesimals to grow at rapid rates, in principle. We present self-consistent hydrodynamics simulations with direct particle integration and gas-drag coupling to estimate the rate of planetesimal growth due to pebble accretion. Wind tunnel simulations are used to explore a range of particle sizes and disc conditions. We also explore analytic estimates of planetesimal growth and numerically integrate planetesimal drift due to the accretion of small solids. Our results show that, for almost every case that we consider, there is a clearly preferred particle size for accretion that depends on the properties of the accreting planetesimal and the local disc conditions. For solids much smaller than the preferred particle size, accretion rates are significantly reduced as the particles are entrained in the gas and flow around the planetesimal. Solids much larger than the preferred size accrete at rates consistent with gravitational focusing. Our analytic estimates for pebble accretion highlight the time-scales that are needed for the growth of large objects under different disc conditions and initial planetesimal sizes.

Growth behavior of LiMn2O4 particles formed by solid-state reactions in air and water vapor

International Nuclear Information System (INIS)

Kozawa, Takahiro; Yanagisawa, Kazumichi; Murakami, Takeshi; Naito, Makio

2016-01-01

Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn 2 O 4 particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn 2 O 4 particles in air and water vapor atmospheres as model reactions; LiMn 2 O 4 is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO 3 precursor impregnated with LiOH, LiMn 2 O 4 spheres with a hollow structure were obtained in air, while angulated particles with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700 °C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled. - Graphical abstract: This study has demonstrated a new strategy towards achieving morphology control without the use of additives during conventional solid-state reactions by exploiting water vapor-induced particle growth. - Highlights: • A new strategy to control the morphology of LiMn 2 O 4 particles is proposed. • Water vapor-induced particle growth is exploited in solid-state reactions. • The microstructural evolution of LiMn 2 O 4 particles is investigated. • The shape, size and microstructure can be controlled by solid-state reactions.

MOLECULAR SPECTROSCPY AND REACTIONS OF ACTINIDES IN THE GAS PHASE AND CRYOGENIC MATRICES

Energy Technology Data Exchange (ETDEWEB)

Heaven, Michael C.; Gibson, John K.; Marcalo, Joaquim

2009-02-01

In this chapter we review the spectroscopic data for actinide molecules and the reaction dynamics for atomic and molecular actinides that have been examined in the gas phase or in inert cryogenic matrices. The motivation for this type of investigation is that physical properties and reactions can be studied in the absence of external perturbations (gas phase) or under minimally perturbing conditions (cryogenic matrices). This information can be compared directly with the results from high-level theoretical models. The interplay between experiment and theory is critically important for advancing our understanding of actinide chemistry. For example, elucidation of the role of the 5f electrons in bonding and reactivity can only be achieved through the application of experimentally verified theoretical models. Theoretical calculations for the actinides are challenging due the large numbers of electrons that must be treated explicitly and the presence of strong relativistic effects. This topic has been reviewed in depth in Chapter 17 of this series. One of the goals of the experimental work described in this chapter has been to provide benchmark data that can be used to evaluate both empirical and ab initio theoretical models. While gas-phase data are the most suitable for comparison with theoretical calculations, there are technical difficulties entailed in generating workable densities of gas-phase actinide molecules that have limited the range of species that have been characterized. Many of the compounds of interest are refractory, and problems associated with the use of high temperature vapors have complicated measurements of spectra, ionization energies, and reactions. One approach that has proved to be especially valuable in overcoming this difficulty has been the use of pulsed laser ablation to generate plumes of vapor from refractory actinide-containing materials. The vapor is entrained in an inert gas, which can be used to cool the actinide species to room

Modeling the Gas Dynamics Environment in a Subscale Solid Rocket Test Motor

Science.gov (United States)

Eaton, Andrew M.; Ewing, Mark E.; Bailey, Kirk M.; McCool, Alex (Technical Monitor)

2001-01-01

Subscale test motors are often used for the evaluation of solid rocket motor component materials such as internal insulation. These motors are useful for characterizing insulation performance behavior, screening insulation material candidates and obtaining material thermal and ablative property design data. One of the primary challenges associated with using subscale motors however, is the uncertainty involved when extrapolating the results to full-scale motor conditions. These uncertainties are related to differences in such phenomena as turbulent flow behavior and boundary layer development, propellant particle interactions with the wall, insulation off-gas mixing and thermochemical reactions with the bulk flow, radiation levels, material response to the local environment, and other anomalous flow conditions. In addition to the need for better understanding of physical mechanisms, there is also a need to better understand how to best simulate these phenomena using numerical modeling approaches such as computational fluid dynamics (CFD). To better understand and model interactions between major phenomena in a subscale test motor, a numerical study of the internal flow environment of a representative motor was performed. Simulation of the environment included not only gas dynamics, but two-phase flow modeling of entrained alumina particles like those found in an aluminized propellant, and offgassing from wall surfaces similar to an ablating insulation material. This work represents a starting point for establishing the internal environment of a subscale test motor using comprehensive modeling techniques, and lays the groundwork for improving the understanding of the applicability of subscale test data to full-scale motors. It was found that grid resolution, and inclusion of phenomena in addition to gas dynamics, such as two-phase and multi-component gas composition are all important factors that can effect the overall flow field predictions.

Study of Parameters Effect on Hydrodynamics of a Gas-Solid Chamber Experimentally and Numerically

Directory of Open Access Journals (Sweden)

Rahimzadeh Hassan

2012-04-01

Full Text Available In this research, gas velocity, initial static bed height and particle size effect on hydrodynamics of a non-reactive gas–solid fluidized bed chamber were studied experimentally and computationally. A multi fluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady state behavior of this chamber and momentum exchange coefficients were calculated by using the Syamlal- O’Brien drag functions. Simulation results were compared with the experimental data in order to validate the CFD model. Pressure drops predicted by the simulations at different particle sizes and initial static bed height were in good agreement with experimental measurements at superficial gas velocity higher than the minimum fluidization velocity. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upwards forming larger bubbles. Furthermore, this comparison showed that the model can predict hydrodynamic behavior of gas solid fluidized bed chambers reasonably well.

Reaction between laser ablation plume and ambient gas studied by laser-induced fluorescence imaging spectroscopy

International Nuclear Information System (INIS)

Sasaki, K; Watarai, H

2007-01-01

We visualized the density distributions of C 2 (plume), NO (ambient gas), and CN (reaction product) when a graphite target was ablated by irradiating YAG laser pulses at wavelengths of 1064 and 355 nm in ambient gas mixture of NO and He. It has been shown by the density distributions of C 2 and NO that the expansion of the plume removes the ambient gas and the plume and the ambient gas locate exclusively in both the cases at 1064 and 355 nm. A high CN density was observed at the interface between the plume and the ambient gas at 1064 nm, which is reasonable since chemical reactions between the plume and the ambient gas may occur only at their interface. On the other hand, in the case at 355 nm, we observed considerable CN inside the plume, indicating that the chemical reaction processes in the laser ablation at 355 nm is different from that expected from the density distributions of the plume and the ambient gas

Reaction of hydrogen atoms produced by radiolysis and photolysis in solid phase at 4 and 77 K

International Nuclear Information System (INIS)

Miyazaki, Tetsuo

1991-01-01

The behavior of H atoms in the solid phase has been reviewed with special attention to comparison of H atoms produced by radiolysis with those produced by photolysis. The paper consists of three parts. I -Production of H atoms: (1) the experimental results which indicate H-atom formation in the radiolysis of solid alkane are summarized; (2) ESR saturation behavior of trapped H atoms depends upon the method of H-atom-production, i.e. photolysis or radiolysis, and upon the initial energy of H atoms in the photolysis. II - Diffusion of H atoms: (1) activation energies for thermally-activated diffusion of H atoms are shown; (2) quantum diffusion of H atoms in solid H 2 is explained in terms of repetition of tunneling reaction H 2 + H → H + H 2 . III -Reaction of H atoms: (1) reactions and trapping processes of hot H atoms have been shown in solid methane and argon by use of hot H atoms with specified initial energy; (2) when H atoms are produced by the radiolysis of solvent alkane or by the photolysis of HI in the alkane mixtures at 77 K, the H atoms react very selectively with solute alkane at low concentration. The selective reaction of the H atom has been found in eight matrices; (3) activation energy for a hydrogen-atom-abstraction reaction by thermal H atoms at low temperatures is less than than several kJ mol -1 because of quantum tunneling. The absolute rate constants for H 2 (D 2 , HD) + H(D) tunneling reactions have been determined experimentally in solid hydrogen at 4.2K; (4) theoretical studies for tunneling reactions H 2 (D 2 ,HD) + H(D) at ultralow temperatures were reviewed. The calculated rate constants were compared with the rate constants obtained experimentally. (author)

The Effect of Basepair Mismatch on DNA Strand Displacement

OpenAIRE

Broadwater, D.?W.?Bo; Kim, Harold?D.

2016-01-01

DNA strand displacement is a key reaction in DNA homologous recombination and DNA mismatch repair and is also heavily utilized in DNA-based computation and locomotion. Despite its ubiquity in science and engineering, sequence-dependent effects of displacement kinetics have not been extensively characterized. Here, we measured toehold-mediated strand displacement kinetics using single-molecule fluorescence in the presence of a single base pair mismatch. The apparent displacement rate varied si...

Greenhouse gas contribution of municipal solid waste collection: A case study in the city of Istanbul, Turkey.

Science.gov (United States)

Korkut, Nafiz E; Yaman, Cevat; Küçükağa, Yusuf; Jaunich, Megan K; Demir, İbrahim

2018-02-01

This article estimates greenhouse gas emissions and global warming factors resulting from collection of municipal solid waste to the transfer stations or landfills in Istanbul for the year of 2015. The aim of this study is to quantify and compare diesel fuel consumption and estimate the greenhouse gas emissions and global warming factors associated with municipal solid waste collection of the 39 districts of Istanbul. Each district's greenhouse gas emissions resulting from the provision and combustion of diesel fuel was estimated by considering the number of collection trips and distances to municipal solid waste facilities. The estimated greenhouse gases and global warming factors for the districts varied from 61.2 to 2759.1 t CO 2 -eq and from 4.60 to 15.20 kg CO 2 -eq t -1 , respectively. The total greenhouse gas emission was estimated as 46.4E3 t CO 2 -eq. Lastly, the collection data from the districts was used to parameterise a collection model that can be used to estimate fuel consumption associated with municipal solid waste collection. This mechanistic model can then be used to predict future fuel consumption and greenhouse gas emissions associated with municipal solid waste collection based on projected population, waste generation, and distance to transfer stations and landfills. The greenhouse gas emissions can be reduced by decreasing the trip numbers and trip distances, building more transfer stations around the city, and making sure that the collection trucks are full in each trip.

A CMOS-MEMS clamped–clamped beam displacement amplifier for resonant switch applications

Science.gov (United States)

Liu, Jia-Ren; Lu, Shih-Chuan; Tsai, Chun-Pu; Li, Wei-Chang

2018-06-01

This paper presents a micromechanical clamped–clamped beam (CC-beam) displacement amplifier based on a CMOS-MEMS fabrication process platform. In particular, a 2.0 MHz resonant displacement amplifier composed of two identical CC-beams coupled by a mechanical beam at locations where the two beams have mismatched velocities exhibits a larger displacement, up to 9.96×, on one beam than that of the other. The displacement amplification prevents unwanted input impacting—the structure switches only to the output but not the input—required by resonant switch-based mechanical circuits (Kim et al 2009 22nd IEEE Int. Conf. on Micro Electro Mechanical Systems; Lin et al 2009 15th Int. Conf. on Solid-State Sensors, Actuators, & Microsystems (TRANSDUCERS’09) Li et al 2013 17th Int. Conf. on Solid-State Sensors, Actuators, & Microsystems (TRANSDUCERS’13)). Compared to a single CC-beam displacement amplifier, theory predicts that the displacement amplifying CC-beam array yields a larger overall output displacement for displacement gain beyond 1.13 thanks to the preserved input driving force. A complete analytical model predicts the resultant stiffness and displacement gain of the coupled CC-beam displacement amplifier that match well with finite element analysis (FEA) prediction and measured results.

Highly selective and sensitive detection of miRNA based on toehold-mediated strand displacement reaction and DNA tetrahedron substrate.

Science.gov (United States)

Li, Wei; Jiang, Wei; Ding, Yongshun; Wang, Lei

2015-09-15

MicroRNAs (miRNAs) play important roles in a variety of biological processes and have been regarded as tumor biomarkers in cancer diagnosis and prognosis. In this work, a single-molecule counting method for miRNA analysis was proposed based on toehold-mediated strand displacement reaction (SDR) and DNA tetrahedron substrate. Firstly, a specially designed DNA tetrahedron was assembled with a hairpin at one of the vertex, which has an overhanging toehold domain. Then, the DNA tetrahedron was immobilized on the epoxy-functional glass slide by epoxy-amine reaction, forming a DNA tetrahedron substrate. Next, the target miRNA perhybridized with the toehold domain and initiated a strand displacement reaction along with the unfolding of the hairpin, realizing the selective recognization of miRNA. Finally, a biotin labeled detection DNA was hybridized with the new emerging single strand and the streptavidin coated QDs were used as fluorescent probes. Fluorescent images were acquired via epi-fluorescence microscopy, the numbers of fluorescence dots were counted one by one for quantification. The detection limit is 5 fM, which displayed an excellent sensitivity. Moreover, the proposed method which can accurately be identified the target miRNA among its family members, demonstrated an admirable selectivity. Furthermore, miRNA analysis in total RNA samples from human lung tissues was performed, suggesting the feasibility of this method for quantitative detection of miRNA in biomedical research and early clinical diagnostics. Copyright © 2015 Elsevier B.V. All rights reserved.

A Simple Approach to Characterize Gas-Aqueous Liquid Two-phase Flow Configuration Based on Discrete Solid-Liquid Contact Electrification.

Science.gov (United States)

Choi, Dongwhi; Lee, Donghyeon; Kim, Dong Sung

2015-10-14

In this study, we first suggest a simple approach to characterize configuration of gas-aqueous liquid two-phase flow based on discrete solid-liquid contact electrification, which is a newly defined concept as a sequential process of solid-liquid contact and successive detachment of the contact liquid from the solid surface. This approach exhibits several advantages such as simple operation, precise measurement, and cost-effectiveness. By using electric potential that is spontaneously generated by discrete solid-liquid contact electrification, the configurations of the gas-aqueous liquid two-phase flow such as size of a gas slug and flow rate are precisely characterized. According to the experimental and numerical analyses on parameters that affect electric potential, gas slugs have been verified to behave similarly to point electric charges when the measuring point of the electric potential is far enough from the gas slug. In addition, the configuration of the gas-aqueous liquid two-phase microfluidic system with multiple gas slugs is also characterized by using the presented approach. For a proof-of-concept demonstration of using the proposed approach in a self-triggered sensor, a gas slug detector with a counter system is developed to show its practicality and applicability.

Study on Fluid-solid Coupling Mathematical Models and Numerical Simulation of Coal Containing Gas

Science.gov (United States)

Xu, Gang; Hao, Meng; Jin, Hongwei

2018-02-01

Based on coal seam gas migration theory under multi-physics field coupling effect, fluid-solid coupling model of coal seam gas was build using elastic mechanics, fluid mechanics in porous medium and effective stress principle. Gas seepage behavior under different original gas pressure was simulated. Results indicated that residual gas pressure, gas pressure gradient and gas low were bigger when original gas pressure was higher. Coal permeability distribution decreased exponentially when original gas pressure was lower than critical pressure. Coal permeability decreased rapidly first and then increased slowly when original pressure was higher than critical pressure.

Simulation of a bubbling fluidized bed process for capturing CO2 from flue gas

International Nuclear Information System (INIS)

Choi, Jeong-Hoo; Yi, Chang-Keun; Jo, Sung-Ho; Ryu, Ho-Jung; Park, Young-Cheol

2014-01-01

We simulated a bubbling bed process capturing CO 2 from flue gas. It applied for a laboratory scale process to investigate effects of operating parameters on capture efficiency. The adsorber temperature had a stronger effect than the regenerator temperature. The effect of regenerator temperature was minor for high adsorber temperature. The effect of regenerator temperature decreased to level off for the temperature >250 .deg. C. The capture efficiency was rather dominated by the adsorption reaction than the regeneration reaction. The effect of gas velocity was as appreciable as that of adsorber temperature. The capture efficiency increased with the solids circulation rate since it was ruled by the molar ratio of K to CO 2 for solids circulation smaller than the minimum required one (G s, min ). However, it leveled off for solids circulation rate >G s, min . As the ratio of adsorber solids inventory to the total solids inventory (x w1 ) increased, the capture efficiency increased until x w1 =0.705, but decreased for x w1 >0.705 because the regeneration time decreased too small. It revealed that the regeneration reaction was faster than the adsorption reaction. Increase of total solids inventory is a good way to get further increase in capture efficiency

Electron transfer reactions in microporous solids. Progress report, September 1990--January 1993

Energy Technology Data Exchange (ETDEWEB)

Mallouk, T.E.

1993-01-01

Basic thrust the research program involves use of microporous solids (zeolites, clays, layered and tunnel structure oxide semiconductors) as organizing media for artificial photosynthetic systems. Purpose of the microporous solid is twofold. First, it induces spatial organization of photoactive and electroactive components (sensitizers, semiconductor particles, electron relays, and catalysts) at the solid-solution interface, enhancing the quantum efficiency of charge separation and separating physically the ultimate electron donor and acceptor in the electron transport chain. Second, since the microcrystalline solid admits only molecules of a certain charge and size, it is possible to achieve permanent charge separation by sieving chemical photoproducts (e.g., H{sub 2} and I{sub 3}{sup {minus}}, or H{sub 2} and O{sub 2)} from each other. Spectroscopic and electrochemical methods are used to study the kinetics of electron transfer reactions in these hybrid molecular/solid state assemblies.

Real-time monitoring of enzyme-free strand displacement cascades by colorimetric assays

Science.gov (United States)

Duan, Ruixue; Wang, Boya; Hong, Fan; Zhang, Tianchi; Jia, Yongmei; Huang, Jiayu; Hakeem, Abdul; Liu, Nannan; Lou, Xiaoding; Xia, Fan

2015-03-01

The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications.The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications. Electronic supplementary information (ESI) available: Experimental procedures and analytical data are provided. See DOI: 10.1039/c5nr00697j

Analytical solutions for non-linear conversion of a porous solid particle in a gas–II. Non-isothermal conversion and numerical verification

NARCIS (Netherlands)

Brem, Gerrit; Brouwers, J.J.H.

1990-01-01

In Part I, analytical solutions were given for the non-linear isothermal heterogeneous conversion of a porous solid particle. Account was taken of a reaction rate of general order with respect to the gas reactant, intrinsic reaction surface area and effective pore diffusion, which change with solid

DEM-CFD simulation of purge gas flow in a solid breeder pebble bed

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hao [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Zhenghong [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); University of Science and Technology of China, Hefei 230027 (China); Guo, Haibing [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Ye, Minyou [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Huang, Hongwen, E-mail: inpclane@sina.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2016-12-15

Solid tritium breeding blanket applying pebble bed concept is promising for fusion reactors. Tritium bred in the pebble bed is purged out by inert gas. The flow characteristics of the purge gas are important for the tritium transport from the solid breeder materials. In this study, a randomly packed pebble bed was generated by Discrete Element Method (DEM) and verified by radial porosity distribution. The flow parameters of the purge gas in channels were solved by Computational Fluid Dynamics (CFD) method. The results show that the normalized velocity magnitudes have the same damped oscillating patterns with radial porosity distribution. Besides, the bypass flow near the wall cannot be ignored in this model, and it has a slight increase with inlet velocity. Furthermore, higher purging efficiency becomes with higher inlet velocity and especially higher in near wall region.

Electrode Kinetics and Gas Conversion in Solid Oxide Cells

DEFF Research Database (Denmark)

Njodzefon, Jean-Claude

The solid oxide fuel cell (SOFC) converts hydrogen, carbon monoxide and hydrocarbon fuels (directly) into electricity with very high efficiencies and has demonstrated almost comparable performance when operated in reverse mode as a solid oxide electrolysis cell (SOEC). In this case electrical (and...... thermal) energy is stored as chemical energy of reaction products. To this end, the cells are fed with steam (H2O electrolysis), carbon dioxide (CO2 electrolysis) or a mixture of both (H2O/CO2 co-electrolysis) and of course electrical (ΔG) and thermal (TΔS) energies for the splitting of reactant compounds...... of the solid oxide cell (SOC) and independent of polarization mode (fuel cell mode or electrolysis mode), the current flowing through the cell is limited by processes such as adsorption and desorption of reactants or products, diffusion through the porous electrodes, activation or charge transfer...

Heterogeneous reactions and aerosol formation in flue gas cleaning by electron beam

International Nuclear Information System (INIS)

Baumann, W.; Jordan, S.; Leichsenring, C.H.; Maetzing, H.; Paur, H.R.; Schikarski, W.

1990-08-01

The electron beam dry scrubbing process is a simultaneous method for the removal of SO 2 and NO x from flue gas. By electron irradiation radicals (OH, O 2 H, O) are formed from the main flue gas components which oxidize NO x and SO 2 into the acids HNO 3 and H 2 SO 4 . These are then neutralized by the injection of NH 3 . A submicron aerosol consisting of ammonium salts is formed which is filtered from the offgas. The main pathways of the gas phase chemistry and product formation have been elucidated by experimental and theoretical studies. Back reactions which occur in the gas and the particle phase limit the energy efficiency of the process. By recirculation of irradiated gas into the reaction vessel (multiple irradiation) a significant improvement of removal yields was obtained. This enhancement of the energy efficiency requires the removal of products between the irradiation steps. Studies show that the material balance is complete. Deficits in the N and S balance of the process are due to the additional formation of molecular nitrogen and the deposition of ammonium sulfate in the ducts. Aerosol formation participates only with 30% in the material balance. The remaining 70% of the product are formed by surface reactions in the filter cake (40%) and in the ducts (30%). (orig.) With 38 figs., 29 tabs [de

A light-gas gun for acceleration of pellets of solid D2

International Nuclear Information System (INIS)

Nordskov, A.; Skovgaard, H.; Soerensen, H.; Weisberg, K.V.

1980-10-01

A gun has been designed and built to be used for injecting solid D 2 pellets into a small tokamak for pellet-plasma interaction studies. The pellets are formed and accelerated at temperatures close to those of liquid helium. They are propelled with pressurised H 2 -gas; the pressure arises when a quantity of solid H 2 placed in the gun barrel behind the pellet is pulse heated. Pellet velocities up to 240 m/s have been obtained. The directional accuracy is better than 0.2deg and the repetition rate is one firing every five minutes. The pellet volume is 0.6 mm 3 (2 x 10 19 molecules) while the quantity of propeller gas used is around 12 x 10 19 molecules. (author)

Interactions of cephalexin with bovine serum albumin: displacement reaction and molecular docking

Directory of Open Access Journals (Sweden)

Hamed Hamishehkar

2016-09-01

Conclusion: The outcomes of spectroscopic methods revealed that the conformation of BSA changed during drug-BSA interaction. The results of FRET propose that CPL quenches the fluorescence of BSA by static quenching and FRET. The displacement study showed that phenylbutazon and ketoprofen displaced CPL, indicating that its binding site on albumin is site I and Gentamicin cannot be displaced from the binding site of CPL. All results of molecular docking method agreed with the results of experimental data.

Strategies for displacing oil

Science.gov (United States)

Rao, Vikram; Gupta, Raghubir

2015-03-01

Oil currently holds a monopoly on transportation fuels. Until recently biofuels were seen as the means to break this stranglehold. They will still have a part to play, but the lead role has been handed to natural gas, almost solely due to the increased availability of shale gas. The spread between oil and gas prices, unprecedented in its scale and duration, will cause a secular shift away from oil as a raw material. In the transport fuel sector, natural gas will gain traction first in the displacement of diesel fuel. Substantial innovation is occurring in the methods of producing liquid fuel from shale gas at the well site, in particular in the development of small scale distributed processes. In some cases, the financing of such small-scale plants may require new business models.

Mathematical modeling of the coupled transport and electrochemical reactions in solid oxide steam electrolyzer for hydrogen production

International Nuclear Information System (INIS)

Ni, Meng; Leung, Michael K.H.; Leung, Dennis Y.C.

2007-01-01

A mathematical model was developed to simulate the coupled transport/electrochemical reaction phenomena in a solid oxide steam electrolyzer (SOSE) at the micro-scale level. Ohm's law, dusty gas model (DGM), Darcy's law, and the generalized Butler Volmer equation were employed to determine the transport of electronic/ionic charges and gas species as well as the electrochemical reactions. Parametric analyses were performed to investigate the effects of operating parameters and micro-structural parameters on SOSE potential. The results substantiated the fact that SOSE potential could be effectively decreased by increasing the operating temperature. In addition, higher steam molar fraction would enhance the operation of SOSE with lower potential. The effect of particle sizes on SOSE potential was studied with due consideration on the SOSE activation and concentration overpotentials. Optimal particle sizes that could minimize the SOSE potential were obtained. It was also found that decreasing electrode porosity could monotonically decrease the SOSE potential. Besides, optimal values of volumetric fraction of electronic particles were found to minimize electrode total overpotentials. In order to optimize electrode microstructure to minimize SOSE electricity consumption, the concept of 'functionally graded materials (FGM)' was introduced to lower the SOSE potential. The advanced design of particle size graded SOSE was found effective for minimizing electrical energy consumption resulting in efficient SOSE hydrogen production. The micro-scale model was capable of predicting SOSE hydrogen production performance and would be a useful tool for design optimization

Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Chen Li [Department of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Goettingen (Germany); Ueta, Hirokazu; Beck, Rainer D. [Laboratoire de Chimie Physique Moleculaire, Ecole Polytechnique Federale de Lausanne (Switzerland); Bisson, Regis [Aix-Marseille Universite, PIIM, CNRS, UMR 7345, 13397 Marseille (France)

2013-05-15

We report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S({theta}). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface.

Fluid-solid contact vessel having fluid distributors therein

Science.gov (United States)

Jones, Jr., John B.

1980-09-09

Rectangularly-shaped fluid distributors for large diameter, vertical vessels include reinforcers for high heat operation, vertical sides with gas distributing orifices and overhanging, sloped roofs. Devices are provided for cleaning the orifices from a buildup of solid deposits resulting from the reactions in the vessel.

Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

Science.gov (United States)

Steinecker, William H; Miecznikowski, Krzysztof; Kulesza, Pawel J; Sandlin, Zechariah D; Cox, James A

2017-11-01

An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase. Response was demonstrated toward a diverse set of analytes, namely hydrogen, 1,2-ethandithiol, phenol, p-cresol, and thioanisole. Using flow injection amperometry of hydrogen with He as the carrier gas, 90% of the steady-state current was achieved in < 1s at a flow rate of 20mLmin -1 . A separation of 1,2-ethandithiol, phenol, p-cresol, and thioanisole at a 2.2mLmin -1 flow rate was achieved with respective detection limits (k = 3 criterion) of 4, 1, 3, and 70 ppmv when the working electrode potential was 800mV. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental investigation of attrition resistance of zeolite catalysts in two particle gas-solid-solid fluidization system

International Nuclear Information System (INIS)

Nawaz, Z.; Ziaoping, T.; Shu, Q.; Wei, F.; Naveed, S.

2010-01-01

In the study of mechanical degradation of 34 ZSM-5 and SAPO catalysts, using the gas jet attrition - ASTM standard fluidized bed test (D-5757), the effect of particle size and its quantitative analysis in co-fluidization environment was investigated on the air jet index (AJI) basis. In gas-solid-solid fluidized bed reactors (GSS-FBR), two different sized particles were fluidized under isothermal conditions. In case of ZSM-5 and SAPO-34, significant attrition resistance was observed, which was attributed to small pore size and specific structural strength of the mobile framework image (MFI) and chabasite (CHA) structures, respectively. The optimum AJI for SAPO-34 and ZSM-5 (of particle size 0.2 mm) in GSS-fluidization system was observed to be 0.0118 and 0.0062, respectively. In co-fluidization, deviations from Gwyn relationship were observed due to change in impact of collision. Therefore, zeolites are recommended as suitable catalysts or catalytic supports (for doping of expensive metals) and for commercial use in GSS-FBR. (author)

Use of radioactive tracers in chemical reactions. the displacement of zinc-nickel complexes with quantitative determination of nickel

International Nuclear Information System (INIS)

Mazzilli, B.; Saiki, M.

1983-01-01

The present paper presents a method for the determination of small quantities of nickel radioactive tracers. An analytical application of the displacement reaction between nickel and zinc ethylenediaminetetraacetate labeled with zinc-65 is pursued. This method is based on the extraction of radioactive zinc displaced by nickel from the zinc chelate into a dithizone-carbon tetrachloride solution and the subsequent measurement of the activity of an aliquot of the extract. The method is very sensitive and nickel can be measured in concentrations as small as 0.1 μg/ml or even less, depending on the specific activity of the radioreagent used. The precision and the accuracy of the method are determined. The problem of interferences is also investigated and an attempt is made in order to eliminate them by using masking agents or by means of a previous separation between nickel and other interfering metals. (Author) [pt

Potential for natural gas to displace oil in response to the Middle East crisis and the implications for the GRI R and D program

International Nuclear Information System (INIS)

Holtberg, P.D.; Webb, D.O.

1990-11-01

Although the significance of Iraq's invasion of Kuwait is indeterminate, a move toward more efficient use of energy in end use applications and increased reliance on domestic energy sources is anticipated. The short and long term potential for natural gas to displace oil in end use applications is analyzed and R and D initiatives are proposed that would accelerate the development of technology by GRI and the gas industry necessary to maximize the substitution of gas for oil

Effect of the reaction medium on the properties of solid catalysts

Energy Technology Data Exchange (ETDEWEB)

Boreskov, G.K.

1980-01-01

The effect of the reaction medium on the properties of solid catalysts, such as bulk or supported metals, alloys, or metal oxides, include variations in surface composition, structure, and catalytic properties due to catalyst interaction with the reactants. This interaction leads to the establishment of a steady state, which is determined by the composition of the reaction medium and temperature, but is independent of the initial state of the catalyst. This steady state for a catalyst of a given chemical composition is characterized by an approximately constant specific activity in most chemical reactions, which is almost independent of the preparation method, surface area, or crystal size of the catalyst. The structurally sensitive reactions, which occur only on limited segments of catalyst surface characterized by specific structures, are the exception. The effects of the variations in catalytic properties caused by the reaction medium on the steady-state and nonsteady-state reaction kinetics are also discussed based on the results obtained for oxidative dehydrogenation of 1-butene over an iron/antimony oxide catalyst.

Method and apparatus for controlling gas evolution from chemical reactions

Science.gov (United States)

Skorpik, James R.; Dodson, Michael G.

1999-01-01

The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846.

Gas-phase ion-molecule reactions and high-pressure mass spectrometer, 1

International Nuclear Information System (INIS)

Hiraoka, Kenzo

1977-01-01

The reasons for the fact that the research in gas-phase ion-molecule reactions, to which wide interest is shown, have greatly contributed to the physical and chemical fields are that, first it is essential in understanding general phenomena concerning ions, second, it can furnish many unique informations in the dynamics of chemical reactions, and third, usefulness of '' chemical ionization'' methods has been established as its application to chemical analysis. In this review, the history and trend of studies and equipments in gas-phase ion-molecule reactions are surveyed. The survey includes the chemical ionization mass spectrometer for simultaneously measuring the positive and negative ions utilizing a quadrupole mass spectrometer presented by Hunt and others, flowing afterglow method derived from the flowing method which traces neutral chemical species mainly optically, ion cyclotron resonance mass spectrometer, trapped ion mass spectrometer and others. Number of reports referred to ion-molecule reactions issued during the last one year well exceeds the total number of reports concerning mass spectrometers presented before 1955. This truly shows how active the research and development are in this field. (Wakatsuki, Y.)

Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

Directory of Open Access Journals (Sweden)

Santiago Sempere

2018-01-01

Full Text Available We study the structural and mobility properties of edge dislocations in rare-gas crystals with the hexagonal close-packed (hcp structure by using classical simulation techniques. Our results are discussed in the light of recent experimental and theoretical studies on hcp 4 He, an archetypal quantum crystal. According to our simulations classical hcp rare-gas crystals present a strong tendency towards dislocation dissociation into Shockley partials in the basal plane, similarly to what is observed in solid helium. This is due to the presence of a low-energy metastable stacking fault, of the order of 0.1 mJ/m 2 , that can get further reduced by quantum nuclear effects. We compute the minimum shear stress that induces glide of dislocations within the hcp basal plane at zero temperature, namely, the Peierls stress, and find a characteristic value of the order of 1 MPa. This threshold value is similar to the Peierls stress reported for metallic hcp solids (Zr and Cd but orders of magnitude larger than the one estimated for solid helium. We find, however, that in contrast to classical hcp metals but in analogy to solid helium, glide of edge dislocations can be thermally activated at very low temperatures, T∼10 K, in the absence of any applied shear stress.

Potential for a solids fire during an ITP waste tank deflagration and the impact on gas pressure

International Nuclear Information System (INIS)

Thomas, J.K.

1993-07-01

During the In-Tank Precipitation (ITP) process, solid deposits may form at the water-line on internal waste tank surfaces. These solids may be combustible due to the presence of tetraphenylborate compounds and hence there is a potential that a waste tank deflagration could ignite a solids fire. The work described in this report evaluates the potential for a waste tank deflagration to ignite a solids fire and the subsequent effect on gas pressure. Thermal analyses were performed using a one-dimensional conduction model, radiative heat flux values calculated with the Deflagration Pressure Analysis Code (DPAC), and effective deposit properties calculated from the component properties. It was shown that a solids fire could only be ignited by a waste tank deflagration for a limited range of cases. For the best-estimate mixtures, a solids fire could not be ignited prior to the time the peak gas pressure is reached and would not increase the peak pressure. For the upper-bound mixtures, the thickness of the solid layer which could be ignited is insufficient to increase the energy released by the deflagration by a significant amount. It was also shown that these conclusions are relatively insensitive to uncertainties related to deposit composition. Thus, the contribution from a solids fire to the gas pressure resulting from a waste tank deflagration may be neglected

Studies of gas phase ion/molecule reactions by Fourier transform ion cyclotron resonance mass spectrometry

International Nuclear Information System (INIS)

Kleingeld, J.C.

1984-01-01

An important field in which Fourier-transform ion cyclotron resonance has useful applications is that of gas phase ion chemistry, the subject of this thesis. First, the general picture of ion-molecule reactions in the gas phase is discussed. Next, some positive ion-molecule reactions are described, whereas the remaining chapters deal with negative ion-molecule reactions. Most of these studies have been performed using the FT-ICR method. Reactions involving H 3 O - and NH 4 - ions are described whereas the other chapters deal with larger organic complexes. (Auth.)

Experimental validation of a numerical model of two-phase displacement in porous medium

International Nuclear Information System (INIS)

Genty, A.

1996-01-01

Burial in geological layers appears to be an interesting solution to dispose of radioactive wastes. This thesis analyzes and simulates the behaviour of gas produced by waste barrels corrosion. The released contaminated gas drains the water initially present in the host rock and yields a water-gas two phase flow. A literature survey of two phase flow shows that fluid interfaces may display instabilities for definite flow characteristics. When the displacement is stable a smooth interface proceeds through the porous medium. When the interface shows fingering, the displacement is said to be 'viscous-unstable', and when the front is jagged the displacement is called 'capillary' displacement. A dimensional analysis of classical equations governing two phase flow in porous media is combined with a classification of dominant forces to define an original map of flow regimes that includes gravitational forces. The map is based on three dimensionless numbers and predicts a priori the flow type. For typical data describing a radioactive waste repository a 'viscous-unstable' displacement is predicted by the map. We simulate water-gas displacement with a numerical model previously developed; this code, based on the Muskat model, uses the mixed-hybrid finite elements technique and is therefore well adapted for tracking moving interfaces. Fluxes are well conserved, however instabilities cannot be simulated. We assume that there is always a scale to be found where instabilities can be averaged and we try to validate the model with experimental two phase flows. We performed laboratory water-gas flow experiments for a variety of flow conditions. The observed displacement types are consistent with the map of flow regimes. Good agreement with numerical simulations is obtained when precise parameters of the displacements are available, in particular relative permeability curves. We conclude that our model allows a first approach of migration of gas near a radioactive waste repository

In Situ Monitoring of Chemical Reactions at a Solid-Water Interface by Femtosecond Acoustics.

Science.gov (United States)

Shen, Chih-Chiang; Weng, Meng-Yu; Sheu, Jinn-Kong; Yao, Yi-Ting; Sun, Chi-Kuang

2017-11-02

Chemical reactions at a solid-liquid interface are of fundamental importance. Interfacial chemical reactions occur not only at the very interface but also in the subsurface area, while existing monitoring techniques either provide limited spatial resolution or are applicable only for the outmost atomic layer. Here, with the aid of the time-domain analysis with femtosecond acoustics, we demonstrate a subatomic-level-resolution technique to longitudinally monitor chemical reactions at solid-water interfaces, capable of in situ monitoring even the subsurface area under atmospheric conditions. Our work was proven by monitoring the already-known anode oxidation process occurring during photoelectrochemical water splitting. Furthermore, whenever the oxide layer thickness equals an integer  number of the effective atomic layer thickness, the measured acoustic echo will show higher signal-to-noise ratios with reduced speckle noise, indicating the quantum-like behavior of this coherent-phonon-based technique.

Transport and reaction processes affecting the attenuation of landfill gas in cover soils

DEFF Research Database (Denmark)

Molins, S.; Mayer, K.U.; Scheutz, Charlotte

2008-01-01

of methane, chlorofluorocarbons, and hydrochlorofluorocarbons to the atmosphere. This study was conducted to investigate the effect of oxidation reactions on the overall gas transport regime and to evaluate, the contributions of various gas transport processes on methane attenuation in landfill cover soils....... For this purpose, a reactive transport model that includes advection and the Dusty Gas Model for simulation of multicomponent gas diffusion was used. The simulations are constrained by data from a series of counter-gradient laboratory experiments. Diffusion typically accounts for over 99% of methane emission...... to the atmosphere. Oxygen supply into the soil column is driven exclusively by diffusion, whereas advection outward offsets part of the diffusive contribution. In the reaction zone, methane consumption reduces the pressure gradient, further decreasing the significance of advection near the top of the column...

Solid-State Gas Sensors: Sensor System Challenges in the Civil Security Domain.

Science.gov (United States)

Müller, Gerhard; Hackner, Angelika; Beer, Sebastian; Göbel, Johann

2016-01-20

The detection of military high explosives and illicit drugs presents problems of paramount importance in the fields of counter terrorism and criminal investigation. Effectively dealing with such threats requires hand-portable, mobile and affordable instruments. The paper shows that solid-state gas sensors can contribute to the development of such instruments provided the sensors are incorporated into integrated sensor systems, which acquire the target substances in the form of particle residue from suspect objects and which process the collected residue through a sequence of particle sampling, solid-vapor conversion, vapor detection and signal treatment steps. Considering sensor systems with metal oxide gas sensors at the backend, it is demonstrated that significant gains in sensitivity, selectivity and speed of response can be attained when the threat substances are sampled in particle as opposed to vapor form.

Thin liquid films with time-dependent chemical reactions sheared by an ambient gas flow

Science.gov (United States)

Bender, Achim; Stephan, Peter; Gambaryan-Roisman, Tatiana

2017-08-01

Chemical reactions in thin liquid films are found in many industrial applications, e.g., in combustion chambers of internal combustion engines where a fuel film can develop on pistons or cylinder walls. The reactions within the film and the turbulent outer gas flow influence film stability and lead to film breakup, which in turn can lead to deposit formation. In this work we examine the evolution and stability of a thin liquid film in the presence of a first-order chemical reaction and under the influence of a turbulent gas flow. Long-wave theory with a double perturbation analysis is used to reduce the complexity of the problem and obtain an evolution equation for the film thickness. The chemical reaction is assumed to be slow compared to film evolution and the amount of reactant in the film is limited, which means that the reaction rate decreases with time as the reactant is consumed. A linear stability analysis is performed to identify the influence of reaction parameters, material properties, and environmental conditions on the film stability limits. Results indicate that exothermic reactions have a stabilizing effect whereas endothermic reactions destabilize the film and can lead to rupture. It is shown that an initially unstable film can become stable with time as the reaction rate decreases. The shearing of the film by the external gas flow leads to the appearance of traveling waves. The shear stress magnitude has a nonmonotonic influence on film stability.

Development of a Reduced-Order Model for Reacting Gas-Solids Flow using Proper Orthogonal Decomposition

Energy Technology Data Exchange (ETDEWEB)

McDaniel, Dwayne [Florida International Univ., Miami, FL (United States); Dulikravich, George [Florida International Univ., Miami, FL (United States); Cizmas, Paul [Florida International Univ., Miami, FL (United States)

2017-11-27

This report summarizes the objectives, tasks and accomplishments made during the three year duration of this research project. The report presents the results obtained by applying advanced computational techniques to develop reduced-order models (ROMs) in the case of reacting multiphase flows based on high fidelity numerical simulation of gas-solids flow structures in risers and vertical columns obtained by the Multiphase Flow with Interphase eXchanges (MFIX) software. The research includes a numerical investigation of reacting and non-reacting gas-solids flow systems and computational analysis that will involve model development to accelerate the scale-up process for the design of fluidization systems by providing accurate solutions that match the full-scale models. The computational work contributes to the development of a methodology for obtaining ROMs that is applicable to the system of gas-solid flows. Finally, the validity of the developed ROMs is evaluated by comparing the results against those obtained using the MFIX code. Additionally, the robustness of existing POD-based ROMs for multiphase flows is improved by avoiding non-physical solutions of the gas void fraction and ensuring that the reduced kinetics models used for reactive flows in fluidized beds are thermodynamically consistent.

Solid state reaction studies in Fe{sub 3}O{sub 4}–TiO{sub 2} system by diffusion couple method

Energy Technology Data Exchange (ETDEWEB)

Ren, Zhongshan [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Hu, Xiaojun, E-mail: huxiaojun@ustb.edu.cn [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Xue, Xiangxin [School of Materials and Metallurgy, Northeastern University, Shenyang 110006 (China); Chou, Kuochih [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

2013-12-15

Highlights: •The solid state reactions of Fe2O3-TiO2 system was studied by the diffusion couple method. •Different products were formed by diffusion, and the FeTiO3 was more stable phase. •The inter-diffusion coefficients and diffusion activation energy were estimated. -- Abstract: The solid state reactions in Fe{sub 3}O{sub 4}–TiO{sub 2} system has been studied by diffusion couple experiments at 1323–1473 K, in which the oxygen partial pressure was controlled by the CO–CO{sub 2} gas mixture. The XRD analysis was used to confirm the phases of the inter-compound, and the concentration profiles were determined by electron probe microanalysis (EPMA). Based on the concentration profile of Ti, the inter-diffusion coefficients in Fe{sub 3}O{sub 4} phase, which were both temperature and concentration of Ti ions dependent, were calculated by the modified Boltzmann–Matano method. According to the relation between the thickness of diffusion layer and temperature, the diffusion coefficient of the Fe{sub 3}O{sub 4}–TiO{sub 2} system was obtained. According to the Arrhenius equation, the estimated diffusion activation energy was about 282.1 ± 18.8 kJ mol{sup −1}.

The impact of municipal solid waste management on greenhouse gas emissions in the United States.

Science.gov (United States)

Weitz, Keith A; Thorneloe, Susan A; Nishtala, Subba R; Yarkosky, Sherry; Zannes, Maria

2002-09-01

Technological advancements, environmental regulations, and emphasis on resource conservation and recovery have greatly reduced the environmental impacts of municipal solid waste (MSW) management, including emissions of greenhouse gases (GHGs). This study was conducted using a life-cycle methodology to track changes in GHG emissions during the past 25 years from the management of MSW in the United States. For the baseline year of 1974, MSW management consisted of limited recycling, combustion without energy recovery, and landfilling without gas collection or control. This was compared with data for 1980, 1990, and 1997, accounting for changes in MSW quantity, composition, management practices, and technology. Over time, the United States has moved toward increased recycling, composting, combustion (with energy recovery) and landfilling with gas recovery, control, and utilization. These changes were accounted for with historical data on MSW composition, quantities, management practices, and technological changes. Included in the analysis were the benefits of materials recycling and energy recovery to the extent that these displace virgin raw materials and fossil fuel electricity production, respectively. Carbon sinks associated with MSW management also were addressed. The results indicate that the MSW management actions taken by U.S. communities have significantly reduced potential GHG emissions despite an almost 2-fold increase in waste generation. GHG emissions from MSW management were estimated to be 36 million metric tons carbon equivalents (MMTCE) in 1974 and 8 MMTCE in 1997. If MSW were being managed today as it was in 1974, GHG emissions would be approximately 60 MMTCE.

A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.

Energy Technology Data Exchange (ETDEWEB)

Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

2013-03-01

Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms

International Nuclear Information System (INIS)

Jorge, Nelly Lidia; Romero, Jorge Marcelo; Grand, André; Hernández-Laguna, Alfonso

2012-01-01

Highlights: ► Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. ► Gas chromatography and computational potential energy surfaces were performed. ► A mechanism in steps looked like the most probable mechanism. ► A spin–orbit coupling appeared at the singlet and triple diradical open structures. ► A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463–503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 ± 0.8 kcal/mol and 5.2 × 10 13 s −1 , respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G ∗∗ level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin–orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.

Optimisation of environmental gas cleaning routes for solid wastes cogeneration systems. Part II - Analysis of waste incineration combined gas/steam cycle

International Nuclear Information System (INIS)

Holanda, Marcelo R.; Perrella Balestieri, Jose A.

2008-01-01

In the first paper of this paper (Part I), conditions were presented for the gas cleaning technological route for environomic optimisation of a cogeneration system based in a thermal cycle with municipal solid waste incineration. In this second part, an environomic analysis is presented of a cogeneration system comprising a combined cycle composed of a gas cycle burning natural gas with a heat recovery steam generator with no supplementary burning and a steam cycle burning municipal solid wastes (MSW) to which will be added a pure back pressure steam turbine (another one) of pure condensation. This analysis aims to select, concerning some scenarios, the best atmospheric pollutant emission control routes (rc) according to the investment cost minimisation, operation and social damage criteria. In this study, a comparison is also performed with the results obtained in the Case Study presented in Part I

Study of reaction sequences for formation of solid solution: 0,48 ...

African Journals Online (AJOL)

... of a low concentration of ions forming the perovskite structure PZT (Pb2+, Zr4+ et Ti4+) by other ions (Zn2+, Cr3+ et Sb+5 in our study) alters the reaction sequences training of the solid solution PZT and especially the formation of intermediate phase. Keywords: PZT / Calcination / TGA / DTA / RX / Piezoelectric Ceramics ...

Numerical simulation of gas-solid flow in an interconnected fluidized bed

Directory of Open Access Journals (Sweden)

Canneto Giuseppe

2015-01-01

Full Text Available The gas-particles flow in an interconnected bubbling fluidized cold model is simulated using a commercial CFD package by Ansys. Conservation equations of mass and momentum are solved using the Eulerian granular multiphase model. Bubbles formation and their paths are analyzed to investigate the behaviour of the bed at different gas velocities. Experimental tests, carried out by the cold model, are compared with simulation runs to study the fluidization quality and to estimate the circulation of solid particles in the bed.

Measurement of interactions between solid particles, liquid droplets, and/or gas bubbles in a liquid using an integrated thin film drainage apparatus.

Science.gov (United States)

Wang, Louxiang; Sharp, David; Masliyah, Jacob; Xu, Zhenghe

2013-03-19

A novel device was designed to measure drainage dynamics of thin liquid films confined between a solid particle, an immiscible liquid droplet, and/or gas bubble. Equipped with a bimorph force sensor, a computer-interfaced video capture, and a data acquisition system, the newly designed integrated thin film drainage apparatus (ITFDA) allows for the direct and simultaneous measurements of force barrier, true film drainage time, and bubble/droplet deformation under a well-controlled external force, receding and advancing contact angles, capillary force, and adhesion (detachment) force between an air bubble or oil droplet and a solid, a liquid, or an air bubble in an immiscible liquid. Using the diaphragm of a high-frequency speaker as the drive mechanism for the air bubble or oil droplet attached to a capillary tube, this newly designed device is capable of measuring forces over a wide range of hydrodynamic conditions, including bubble approach and retract velocities up to 50 mm/s and displacement range up to 1 mm. The results showed that the ITFDA was capable of measuring hydrodynamic resistance, film drainage time, and other important physical parameters between air bubbles and solid particles in aqueous solutions. As an example of illustrating the versatility, the ITFDA was also applied to other important systems such as interactions between air bubble and oil droplet, two air bubbles, and two oil droplets in an aqueous solution.

Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

Science.gov (United States)

Kamioka, K.; Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

2014-08-01

The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 1020 cm-3) into ZnO is performed using a multiple-step energy. The high resistivity of ∼103 Ω cm in un-implanted samples remarkably decreased to ∼10-2 Ω cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

A comparative study of gas-gas miscibility processes in underground gas storage reservoirs

Energy Technology Data Exchange (ETDEWEB)

Rafiee, M.M.; Schmitz, S. [DBI - Gastechnologisches Institut gGmbH, Freiberg (Germany)

2013-08-01

Intermixture of gases in underground gas reservoirs have had great weight for natural gas storage in UGS projects with substitution of cushion gas by inert gases or changing the stored gas quality or origin, as for the replacement of town gas by natural gas. It was also investigated during the last years for Enhanced Gas Recovery (EGR) and Carbon Capture and Storage (CCS) projects. The actual importance of its mechanisms is discussed for the H{sub 2} storage in Power to Gas to Power projects (PGP). In these approaches miscibility of the injected gas with the gas in place in the reservoir plays an important role in the displacement process. The conditions and parameters for the gas-gas displacement and mixing have been investigated in previous projects, as e.g. the miscibility of CO{sub 2} with natural gas (CLEAN). Furthermore the miscibility process of town gas with natural gas and sauer gas with sweet gas were also previously measured and compared in laboratory. The objective of this work is to investigate the miscibility of H{sub 2} injection into natural gas reservoirs using a compositional and a black oil reservoir simulator. Three processes of convection, dispersion and diffusion are considered precisely. The effect of gas miscibility is studied for both simulators and the results are compared to find optimum miscibility parameters. The findings of this work could be helpful for further pilot and field case studies to predict and monitor the changes in gas composition and quality. In future this monitoring might become more important when PGP together with H{sub 2}-UGS, as storage technology, will help to successfully implement the change to an energy supply from more renewable sources. Similarly the method confirms the use of the black oil simulator as an alternative for gas-gas displacement and sequestration reservoir simulation in comparison to the compositional simulator. (orig.)

Synthesis of Ca_3CO_4O_9 via solid state reaction

International Nuclear Information System (INIS)

Melo, K.P.; Dutra, R.P.S.; Marques, K.A.; Junior, S.M.S.; Brasileiro, C.T.; Coutinho, S.V.C.R.; Souza, T.; Chagas, T.F.; Silva, R.M.; Macedo, D.A.

2016-01-01

Solid oxide fuel cells (SOFCs) stand out as the most promising today's energy conversion technologies. In the development of cathode materials for SOFC, calcium cobaltate (Ca3Co4O9, C349) appears as a potential alternative to traditional lanthanum manganites. In this work, C349 was prepared via solid state reaction of stoichiometric mixtures containing CaCO3 from mollusk shells, in natura (M1) and heat treated at 550 ° C (M2), and Co3O4 obtained by citrate method. The M1 and M2 mixtures were calcined at 800 (powder) and 900 ° C (tablets) for 12 h. The crystal structure and phase composition of the powder and the reaction products were studied by X-ray diffraction Rietveld refinement of the diffraction data. The results showed the formation of free C349 secondary stages, showing a good alternative to use waste from seafood shells as raw material for obtaining high-value ceramics.(author)

Numerical simulation of the gas-solid flow in a square circulating fluidized bed with secondary air injection

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhengyang [Harbin Institute of Technology, Harbin (China). Post-doctor Station of Civil Engineering; Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Sun, Shaozeng; Zhao, Ningbo; Wu, Shaohua [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Tan, Yufei [Harbin Institute of Technology, Harbin (China). School of Municipal and Environmental Engineering

2013-07-01

The dynamic behavior of gas-solid flow in an experimental square circulating fluidized bed setup (0.25 m x 0.25 m x 6.07 m) is predicted with numerical simulation based on the theory of Euler-Euler gas-solid two-phase flow and the kinetic theory of granular flows. The simulation includes the operation cases with secondary injection and without air-staging. The pressure drop profile, local solids concentration and particle velocity was compared with experimental results. Both simulation and experimental results show that solids concentration increases significantly below the secondary air injection ports when air-staging is adopted. Furthermore, the flow asymmetry in the solid entrance region of the bed was investigated based on the particle concentration/velocity profile. The simulation results are in agreement with the experimental results qualitatively.

Investigation of potential for occurrence of molten soil displacement events during in situ vitrification of combustible wastes

International Nuclear Information System (INIS)

Roberts, J.S.; Strachan, C.W.; Luey, J.

1993-02-01

Computer simulations are used to investigate the application of in situ vitrification (ISV) for processing contaminated soil containing high loadings of solid, compressible waste material, typical of landfills and solid waste trenches. Specifically, these simulations predict whether significant displacement of molten soil, due to large, 1 to 2 m diameter, gas bubbles rising up through the ISV melt, are likely to occur during processing of combustible waste-loaded sites. These bubbles are believed to originate from high-pressure regions below the melt caused by vaporization of water and gases generated by the combustion, volatilization, or pyrolyzation of combustible materials in the waste. Simulations were run using the TOUGH2 computer code to predict pressures underneath the ISV melt TOUGH2 is an unsaturated groundwater modeling code capable of treating non-isothermal problems. These simulations include moving melt front and simple pyrolysis models and investigate how the gas pressure in the soil below the melt is affected by melt progression rate, soil permeability, combustible and impermeable material loading. The following, conclusions have been drawn based on the TOUGH2 simulations

A green synthesis of a layered titanate, potassium lithium titanate; lower temperature solid-state reaction and improved materials performance

International Nuclear Information System (INIS)

Ogawa, Makoto; Morita, Masashi; Igarashi, Shota; Sato, Soh

2013-01-01

A layered titanate, potassium lithium titanate, with the size range from 0.1 to 30 µm was prepared to show the effects of the particle size on the materials performance. The potassium lithium titanate was prepared by solid-state reaction as reported previously, where the reaction temperature was varied. The reported temperature for the titanate preparation was higher than 800 °C, though 600 °C is good enough to obtain single-phase potassium lithium titanate. The lower temperature synthesis is cost effective and the product exhibit better performance as photocatalysts due to surface reactivity. - Graphical abstract: Finite particle of a layered titanate, potassium lithium titanate, was prepared by solid-state reaction at lower temperature to show modified materials performance. Display Omitted - Highlights: • Potassium lithium titanate was prepared by solid-state reaction. • Lower temperature reaction resulted in smaller sized particles of titanate. • 600 °C was good enough to obtain single phased potassium lithium titanate. • The product exhibited better performance as photocatalyst

Effects of gas flow on oxidation reaction in liquid induced by He/O{sub 2} plasma-jet irradiation

Energy Technology Data Exchange (ETDEWEB)

Nakajima, Atsushi; Uchida, Giichiro, E-mail: uchida@jwri.osaka-u.ac.jp; Takenaka, Kosuke; Setsuhara, Yuichi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Kawasaki, Toshiyuki [Department of Mechanical and Electrical Engineering, Nippon Bunri University, Oita, Oita 870-0397 (Japan); Koga, Kazunori; Sarinont, Thapanut; Amano, Takaaki; Shiratani, Masaharu [Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka, Fukuoka 819-0395 (Japan)

2015-07-28

We present here analysis of oxidation reaction in liquid by a plasma-jet irradiation under various gas flow patterns such as laminar and turbulence flows. To estimate the total amount of oxidation reaction induced by reactive oxygen species (ROS) in liquid, we employ a KI-starch solution system, where the absorbance of the KI-starch solution near 600 nm behaves linear to the total amount of oxidation reaction in liquid. The laminar flow with higher gas velocity induces an increase in the ROS distribution area on the liquid surface, which results in a large amount of oxidation reaction in liquid. However, a much faster gas flow conversely results in a reduction in the total amount of oxidation reaction in liquid under the following two conditions: first condition is that the turbulence flow is triggered in a gas flow channel at a high Reynolds number of gas flow, which leads to a marked change of the spatial distribution of the ROS concentration in gas phase. Second condition is that the dimpled liquid surface is formed by strong gas flow, which prevents the ROS from being transported in radial direction along the liquid surface.

Measurement of characteristics of solid flow in the cyclone separators with fiber optical probe

International Nuclear Information System (INIS)

Li Shaohua; Li Yan; Li Jinjing; Yang Shi; Yang Hairui; Zhang Hai; Lu Junfu; Yue Guangxi

2009-01-01

In some applications, e.g. circulating fluidized beds (CFB), cyclones are usually operated at high solid loadings. Under high inlet solid concentration, most of the particles are collected at the wall and form a dense particle spiral band because of high separation efficiency. As a result, gas-solid reactions should occur mostly in the near-wall region. To understand the gas-solid reaction mechanism in the cyclone, an experimental study was conducted in a plexiglass CFB cold apparatus, with a riser of 0.2m I.D. and 5m high, and a standard Lapple cyclone. Fiber optical probe was used to measure the characteristics of solid flow in the cyclone, including particle velocity and volumetric solid concentration, especially in the near-wall region of the cyclone. Based on the experiment results, the combustion of carbon particles in the cyclone of a CFB boiler was estimated with group combustion theory. The calculated results show that combustion effectiveness factor ηeff of near-wall particle cloud is smaller than 1/25, which means the combustion rate of a carbon particle in the near-wall region is greatly restricted by other particles in the cloud.

Photoemission from excited states in rare gas solids by combining synchrotronradiation with a laser

International Nuclear Information System (INIS)

Bernstorff, S.

1984-09-01

A new spectroscopic method has been developed to study excited states in rare gas solids: Excitons and conductionband-states are populated by synchrotron radiation (photon energy hw SR =5 - 30 eV). Subsequently electrons from these bound or conduction band-states are excited above the vacuum level of the solid by a pulsed dye laser (hw L =1.9 - 3.7 eV). This experimental technique was applied to solid Xe, Kr, Ar and Ne. (orig./GSCH)

The Effect of Basepair Mismatch on DNA Strand Displacement.

Science.gov (United States)

Broadwater, D W Bo; Kim, Harold D

2016-04-12

DNA strand displacement is a key reaction in DNA homologous recombination and DNA mismatch repair and is also heavily utilized in DNA-based computation and locomotion. Despite its ubiquity in science and engineering, sequence-dependent effects of displacement kinetics have not been extensively characterized. Here, we measured toehold-mediated strand displacement kinetics using single-molecule fluorescence in the presence of a single basepair mismatch. The apparent displacement rate varied significantly when the mismatch was introduced in the invading DNA strand. The rate generally decreased as the mismatch in the invader was encountered earlier in displacement. Our data indicate that a single base pair mismatch in the invader stalls branch migration and displacement occurs via direct dissociation of the destabilized incumbent strand from the substrate strand. We combined both branch migration and direct dissociation into a model, which we term the concurrent displacement model, and used the first passage time approach to quantitatively explain the salient features of the observed relationship. We also introduce the concept of splitting probabilities to justify that the concurrent model can be simplified into a three-step sequential model in the presence of an invader mismatch. We expect our model to become a powerful tool to design DNA-based reaction schemes with broad functionality. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Detection of single-nucleotide polymorphisms using an ON-OFF switching of regenerated biosensor based on a locked nucleic acid-integrated and toehold-mediated strand displacement reaction.

Science.gov (United States)

Gao, Zhong Feng; Ling, Yu; Lu, Lu; Chen, Ning Yu; Luo, Hong Qun; Li, Nian Bing

2014-03-04

Although various strategies have been reported for single-nucleotide polymorphisms (SNPs) detection, development of a time-saving, specific, and regenerated electrochemical sensing platform still remains a realistic goal. In this study, an ON-OFF switching of a regenerated biosensor based on a locked nucleic acid (LNA)-integrated and toehold-mediated strand displacement reaction technique is constructed for detection of SNPs. The LNA-integrated and methylene blue-labeled capture probe with an external toehold is designed to switch on the sensing system. The mutant-type DNA probe completes complementary with the capture probe to trigger the strand displacement reaction, which switches off the sensing system. However, when the single-base mismatched wild-type DNA probe is presented, the strand displacement reaction cannot be achieved; therefore, the sensing system still keeps the ON state. This DNA sensor is stable over five reuses. We further testify that the LNA-integrated sequence has better recognition ability for SNPs detection compared to the DNA-integrated sequence. Moreover, this DNA senor exhibits a remarkable discrimination capability of SNPs among abundant wild-type targets and 6000-fold (m/m) excess of genomic DNA. In addition, it is selective enough in complex and contaminant-ridden samples, such as human urine, soil, saliva, and beer. Overall, these results demonstrate that this reliable DNA sensor is easy to be fabricated, simple to operate, and stable enough to be readily regenerated.

Solid-State Gas Sensors: Sensor System Challenges in the Civil Security Domain

Directory of Open Access Journals (Sweden)

Gerhard Müller

2016-01-01

Full Text Available The detection of military high explosives and illicit drugs presents problems of paramount importance in the fields of counter terrorism and criminal investigation. Effectively dealing with such threats requires hand-portable, mobile and affordable instruments. The paper shows that solid-state gas sensors can contribute to the development of such instruments provided the sensors are incorporated into integrated sensor systems, which acquire the target substances in the form of particle residue from suspect objects and which process the collected residue through a sequence of particle sampling, solid-vapor conversion, vapor detection and signal treatment steps. Considering sensor systems with metal oxide gas sensors at the backend, it is demonstrated that significant gains in sensitivity, selectivity and speed of response can be attained when the threat substances are sampled in particle as opposed to vapor form.

Greenhouse Gas Emissions from Solid and Liquid Organic Fertilizers Applied to Lettuce.

Science.gov (United States)

Toonsiri, Phasita; Del Grosso, Stephen J; Sukor, Arina; Davis, Jessica G

2016-11-01

Improper application of nitrogen (N) fertilizer and environmental factors can cause the loss of nitrous oxide (NO) to the environment. Different types of fertilizers with different C/N ratios may have different effects on the environment. The focus of this study was to evaluate the effects of environmental factors and four organic fertilizers (feather meal, blood meal, fish emulsion, and cyano-fertilizer) applied at different rates (0, 28, 56, and 112 kg N ha) on NO emissions and to track CO emissions from a lettuce field ( L.). The study was conducted in 2013 and 2014 and compared preplant-applied solid fertilizers (feather meal and blood meal) and multiple applications of liquid fertilizers (fish emulsion and cyano-fertilizer). Three days a week, NO and CO emissions were measured twice per day in 2013 and once per day in 2014 using a closed-static chamber, and gas samples were analyzed by gas chromatography. Preplant-applied solid fertilizers significantly increased cumulative NO emissions as compared with control, but multiple applications of liquid fertilizers did not. Emission factors for NO ranged from 0 to 0.1% for multiple applications of liquid fertilizers and 0.6 to 11% for preplant-applied solid fertilizers, which could be overestimated due to chamber placement over fertilizer bands. In 2014, solid fertilizers with higher C/N ratios (3.3-3.5) resulted in higher CO emissions than liquid fertilizers (C/N ratio, 0.9-1.5). Therefore, organic farmers should consider the use of multiple applications of liquid fertilizers as a means to reduce soil greenhouse gas emissions while maintaining high yields. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

The behaviour of radionuclides in gas adsorption chromatographic processes with superimposed chemical reactions (chlorides)

International Nuclear Information System (INIS)

Eichler, B.

1996-01-01

Thermochemical relationships are derived describing the gas adsorption chromatographic transport of carrier-free radionuclides. Especially, complex adsorption processes such as dissociative, associative and substitutive adsorption are dealt with. The comparison of experimental with calculated data allows the determination of the type of adsorption reaction, which is the basis of the respective gas chromatographic process. The behaviour of carrier-free radionuclides of elements Pu, Ce, Ru, Co and Cr in thermochromatographic experiments with chlorinating carrier gases can be described as dissociative adsorption of chlorides in higher oxidation states. The gas adsorption chromatographic transport of Zr with oxygen and chlorine containing carrier gas is shown to be a substitutive adsorption process. The consequences of superimposed chemical reactions on the interpretation of results and the conception of gas adsorption chromatographic experiments with carrier-free radionuclides in isothermal columns and in temperature gradient tubes is discussed. (orig.)

Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions

Science.gov (United States)

Lupinetti, Anthony J [Los Alamos, NM; Garcia, Eduardo [Los Alamos, NM; Abney, Kent D [Los Alamos, NM

2004-12-14

The synthesis of actinide tetraborides including uranium tetraboride (UB.sub.4), plutonium tetraboride (PuB.sub.4) and thorium tetraboride (ThB.sub.4) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to .ltoreq.850.degree. C. As an example, when UCl.sub.4 is reacted with an excess of MgB.sub.2, at 850.degree. C., crystalline UB.sub.4 is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl.sub.3 as the initial step in the reaction. The UB.sub.4 product is purified by washing water and drying.

Axial and Radial Gas Holdup in Bubble Column Reactor

International Nuclear Information System (INIS)

Wagh, Sameer M.; Ansari, Mohashin E Alan; Kene, Pragati T.

2014-01-01

Bubble column reactors are considered the reactor of choice for numerous applications including oxidation, hydrogenation, waste water treatment, and Fischer-Tropsch (FT) synthesis. They are widely used in a variety of industrial applications for carrying out gas-liquid and gas-liquid-solid reactions. In this paper, the computational fluid dynamics (CFD) model is used for predicting the gas holdup and its distribution along radial and axial direction are presented. Gas holdup increases linearly with increase in gas velocity. Gas bubbles tends to concentrate more towards the center of the column and follows a wavy path

Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms

Energy Technology Data Exchange (ETDEWEB)

Jorge, Nelly Lidia [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain); Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Romero, Jorge Marcelo [Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Grand, Andre [INAC, SCIB, Laboratoire ' Lesions des Acides Nucleiques' , UMR CEA-UJF E3, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Hernandez-Laguna, Alfonso, E-mail: ahlaguna@ugr.es [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain)

2012-01-17

Highlights: Black-Right-Pointing-Pointer Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. Black-Right-Pointing-Pointer Gas chromatography and computational potential energy surfaces were performed. Black-Right-Pointing-Pointer A mechanism in steps looked like the most probable mechanism. Black-Right-Pointing-Pointer A spin-orbit coupling appeared at the singlet and triple diradical open structures. Black-Right-Pointing-Pointer A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463-503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 {+-} 0.8 kcal/mol and 5.2 Multiplication-Sign 10{sup 13} s{sup -1}, respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G{sup Asterisk-Operator Asterisk-Operator} level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin-orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.

The Effect of an Inert Solid Reservoir on Molecular Abundances in Dense Interstellar Clouds

Directory of Open Access Journals (Sweden)

Kalvāns Juris

2012-12-01

Full Text Available The question, what is the role of freeze-out of chemical species in determining the molecular abundances in the interstellar gas is a matter of debate. We investigate a theoretical case of a dense interstellar molecular cloud core by time-dependent modeling of chemical kinetics, where grain surface reactions deliberately are not included. That means, the gas-phase and solid-phase abundances are influenced only by gas reactions, accretion on grains and desorption. We compare the results to a reference model where no accretion occurs, and only gas-phase reactions are included. We can trace that the purely physical processes of molecule accretion and desorption have major chemical consequences on the gas-phase chemistry. The main effect of introduction of the gas-grain interaction is long-term molecule abundance changes that come nowhere near an equilibrium during the typical lifetime of a prestellar core.

Solid adsorbents for removal of hydrogen sulphide from hot gas

Energy Technology Data Exchange (ETDEWEB)

Furimsky, E.; Yumura, Motoo

1986-04-01

A wide range of solids have been tested as potential adsorbents for H/sub 2/S removal from hot gas. These solids can be divided into two main groups, i.e., the adsorbents containing alkaline earth metals and those containing transition metals. Among the former, calcium oxide and naturally occurring materials such as limestone, dolomite and calcium silicate have attracted a great deal of attention. The adsorbents of the second group include iron oxide alone or in combination with some supports, zinc oxide, zinc ferrite and manganese oxide. The materials containing both the alkaline earth metals and transition metals, e.g., manganese nodules, fly ash and the reject from the aluminium industry (red mud) have been evaluated as well.

Practical experiences with the synthesis of [11C]CH3I through gas phase iodination reaction using a TRACERlabFXC synthesis module

International Nuclear Information System (INIS)

Kniess, Torsten; Rode, Katrin; Wuest, Frank

2008-01-01

The results of [ 11 C]CH 3 I synthesis through hydrogen gas reduction of [ 11 C]CO 2 on different nickel catalysts (HARSHAW-nickel, SHIMALITE-nickel, nickel on silica/alumina, nickel nanosize 99.99%) followed by gas phase iodination using a TRACERlab FX C synthesis unit are reported. Further reaction parameters such as furnace temperatures, flow rate of hydrogen gas and reduction time were optimized. It was found that reduction of [ 11 C]CO 2 proceeded in 28-83% yield depending on the nickel catalyst and temperature. The gas phase iodination (methane conversion) gave 31-62% of [ 11 C]CH 3 I depending on temperature and amount of iodine in the iodine furnace. [ 11 C]CH 3 I was used for heteroatom methylation reactions exemplified by a piperazine and a phenol (1 and 3). The specific activity of the 11 C-labelled products 2 and 4 was determined after HPLC purification and solid-phase extraction. Compounds 2 and 4 were obtained in 8-14% radiochemical yield (decay-corrected, based upon trapped [ 11 C]CH 4 ) within 30 min. The specific activity was determined to be in the range of 20-30 GBq/μmol at the end-of-synthesis. Nickel catalyst nanosize was found to be superior compared with other Ni catalysts tested. The relatively low specific activity may be mainly due to carbon contaminations originating from the long copper tubing (500 m) between the cyclotron and the radiochemistry facility

Computational modeling of chemical reactions and interstitial growth and remodeling involving charged solutes and solid-bound molecules.

Science.gov (United States)

Ateshian, Gerard A; Nims, Robert J; Maas, Steve; Weiss, Jeffrey A

2014-10-01

Mechanobiological processes are rooted in mechanics and chemistry, and such processes may be modeled in a framework that couples their governing equations starting from fundamental principles. In many biological applications, the reactants and products of chemical reactions may be electrically charged, and these charge effects may produce driving forces and constraints that significantly influence outcomes. In this study, a novel formulation and computational implementation are presented for modeling chemical reactions in biological tissues that involve charged solutes and solid-bound molecules within a deformable porous hydrated solid matrix, coupling mechanics with chemistry while accounting for electric charges. The deposition or removal of solid-bound molecules contributes to the growth and remodeling of the solid matrix; in particular, volumetric growth may be driven by Donnan osmotic swelling, resulting from charged molecular species fixed to the solid matrix. This formulation incorporates the state of strain as a state variable in the production rate of chemical reactions, explicitly tying chemistry with mechanics for the purpose of modeling mechanobiology. To achieve these objectives, this treatment identifies the specific theoretical and computational challenges faced in modeling complex systems of interacting neutral and charged constituents while accommodating any number of simultaneous reactions where reactants and products may be modeled explicitly or implicitly. Several finite element verification problems are shown to agree with closed-form analytical solutions. An illustrative tissue engineering analysis demonstrates tissue growth and swelling resulting from the deposition of chondroitin sulfate, a charged solid-bound molecular species. This implementation is released in the open-source program FEBio ( www.febio.org ). The availability of this framework may be particularly beneficial to optimizing tissue engineering culture systems by examining the

Growth behavior of LiMn{sub 2}O{sub 4} particles formed by solid-state reactions in air and water vapor

Energy Technology Data Exchange (ETDEWEB)

Kozawa, Takahiro, E-mail: t-kozawa@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, 11–1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Yanagisawa, Kazumichi [Research Laboratory of Hydrothermal Chemistry, Faculty of Science, Kochi University, 2–5-1 Akebono-cho, Kochi 780-8520 (Japan); Murakami, Takeshi; Naito, Makio [Joining and Welding Research Institute, Osaka University, 11–1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

2016-11-15

Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn{sub 2}O{sub 4} particles in air and water vapor atmospheres as model reactions; LiMn{sub 2}O{sub 4} is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO{sub 3} precursor impregnated with LiOH, LiMn{sub 2}O{sub 4} spheres with a hollow structure were obtained in air, while angulated particles with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700 °C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled. - Graphical abstract: This study has demonstrated a new strategy towards achieving morphology control without the use of additives during conventional solid-state reactions by exploiting water vapor-induced particle growth. - Highlights: • A new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles is proposed. • Water vapor-induced particle growth is exploited in solid-state reactions. • The microstructural evolution of LiMn{sub 2}O{sub 4} particles is investigated. • The shape, size and microstructure can be controlled by solid-state reactions.

Pyrolysis-GCMS Analysis of Solid Organic Products from Catalytic Fischer-Tropsch Synthesis Experiments

Science.gov (United States)

Locke, Darren R.; Yazzie, Cyriah A.; Burton, Aaron S.; Niles, Paul B.; Johnson, Natasha M.

2015-01-01

Abiotic synthesis of complex organic compounds in the early solar nebula that formed our solar system is hypothesized to occur via a Fischer-Tropsch type (FTT) synthesis involving the reaction of hydrogen and carbon monoxide gases over metal and metal oxide catalysts. In general, at low temperatures (less than 200 C), FTT synthesis is expected to form abundant alkane compounds while at higher temperatures (greater than 200 C) it is expected to product lesser amounts of n-alkanes and greater amounts of alkene, alcohol, and polycyclic aromatic hydrocarbons (PAHs). Experiments utilizing a closed-gas circulation system to study the effects of FTT reaction temperature, catalysts, and number of experimental cycles on the resulting solid insoluble organic products are being performed in the laboratory at NASA Goddard Space Flight Center. These experiments aim to determine whether or not FTT reactions on grain surfaces in the protosolar nebula could be the source of the insoluble organic matter observed in meteorites. The resulting solid organic products are being analyzed at NASA Johnson Space Center by pyrolysis gas chromatography mass spectrometry (PY-GCMS). PY-GCMS yields the types and distribution of organic compounds released from the insoluble organic matter generated from the FTT reactions. Previously, exploratory work utilizing PY-GCMS to characterize the deposited organic materials from these reactions has been reported. Presented here are new organic analyses using magnetite catalyst to produce solid insoluble organic FTT products with varying reaction temperatures and number of experimental cycles.

Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

Energy Technology Data Exchange (ETDEWEB)

Kamioka, K.; Oga, T.; Izawa, Y. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kuriyama, K., E-mail: kuri@ionbeam.hosei.ac.jp [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Department of Arts and Science, Osaka Kyouiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

2014-08-01

The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 10{sup 20} cm{sup −3}) into ZnO is performed using a multiple-step energy. The high resistivity of ∼10{sup 3} Ω cm in un-implanted samples remarkably decreased to ∼10{sup −2} Ω cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

Assessment of alternative disposal methods to reduce greenhouse gas emissions from municipal solid waste in India.

Science.gov (United States)

Yedla, Sudhakar; Sindhu, N T

2016-06-01

Open dumping, the most commonly practiced method of solid waste disposal in Indian cities, creates serious environment and economic challenges, and also contributes significantly to greenhouse gas emissions. The present article attempts to analyse and identify economically effective ways to reduce greenhouse gas emissions from municipal solid waste. The article looks at the selection of appropriate methods for the control of methane emissions. Multivariate functional models are presented, based on theoretical considerations as well as the field measurements to forecast the greenhouse gas mitigation potential for all the methodologies under consideration. Economic feasibility is tested by calculating the unit cost of waste disposal for the respective disposal process. The purpose-built landfill system proposed by Yedla and Parikh has shown promise in controlling greenhouse gas and saving land. However, these studies show that aerobic composting offers the optimal method, both in terms of controlling greenhouse gas emissions and reducing costs, mainly by requiring less land than other methods. © The Author(s) 2016.

Impact of the spatial distribution of morphological pattern on the efficiency of electrocatalytic gas evolving reactions

Directory of Open Access Journals (Sweden)

Žerađanin Aleksandar R.

2014-01-01

Full Text Available The efficiency of electrocatalytic gas evolving reactions (hydrogen, chlorine and oxygen evolution is a key challenge for the important industrial processes, such as chlor-alkali electrolysis or water electrolysis. Central issue for the aforementioned electrocatalytic processes is huge power consumption. Experimental results accumulated in the past, as well as some predictive models ("volcano" plots indicate that altering the nature of the electrode material cannot significantly increase the activity of mentioned reactions. Consequently, it is necessary to find a qualitatively different strategy for improving the energy efficiency of electrocatalytic gas evolving reactions. Usually disregarded fact is that the gas evolution is an oscillatory phenomenon. Given the oscillatory behavior, a key parameter of macrokinetics of gas electrode is the frequency of gas-bubble detachment. Bearing in mind that the gas evolution greatly depends on the surface morphology, a methodology is proposed that establishes a rational link between the morphological pattern of electrode with electrode activity and stability. Characterization was performed using advanced analytical tools. Frequency of gas-bubble detachment is obtained in the configuration of scanning electrochemical microscopy (SECM while the corrosion stability is analyzed using miniaturized scanning flow electrochemical cell connected to the mass spectrometer (SFC-ICPMS.

Al-Si/Al2O3 in situ composite prepared by displacement reaction of CuO/Al system

Directory of Open Access Journals (Sweden)

Zhang Jing

2010-02-01

Full Text Available Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al. The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350 ℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/Al system was studied by using of differential scanning calorimetry(DSC and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu2O and Al2O3 at the melting temperature of the matrix alloy, and second, Cu2O reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750–780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.

Flow chemistry: intelligent processing of gas-liquid transformations using a tube-in-tube reactor.

Science.gov (United States)

Brzozowski, Martin; O'Brien, Matthew; Ley, Steven V; Polyzos, Anastasios

2015-02-17

CONSPECTUS: The previous decade has witnessed the expeditious uptake of flow chemistry techniques in modern synthesis laboratories, and flow-based chemistry is poised to significantly impact our approach to chemical preparation. The advantages of moving from classical batch synthesis to flow mode, in order to address the limitations of traditional approaches, particularly within the context of organic synthesis are now well established. Flow chemistry methodology has led to measurable improvements in safety and reduced energy consumption and has enabled the expansion of available reaction conditions. Contributions from our own laboratories have focused on the establishment of flow chemistry methods to address challenges associated with the assembly of complex targets through the development of multistep methods employing supported reagents and in-line monitoring of reaction intermediates to ensure the delivery of high quality target compounds. Recently, flow chemistry approaches have addressed the challenges associated with reactions utilizing reactive gases in classical batch synthesis. The small volumes of microreactors ameliorate the hazards of high-pressure gas reactions and enable improved mixing with the liquid phase. Established strategies for gas-liquid reactions in flow have relied on plug-flow (or segmented flow) regimes in which the gas plugs are introduced to a liquid stream and dissolution of gas relies on interfacial contact of the gas bubble with the liquid phase. This approach confers limited control over gas concentration within the liquid phase and is unsuitable for multistep methods requiring heterogeneous catalysis or solid supported reagents. We have identified the use of a gas-permeable fluoropolymer, Teflon AF-2400, as a simple method of achieving efficient gas-liquid contact to afford homogeneous solutions of reactive gases in flow. The membrane permits the transport of a wide range of gases with significant control of the stoichiometry of

Investigation of Multiscale and Multiphase Flow, Transport and Reaction in Heavy Oil Recovery Processes

Energy Technology Data Exchange (ETDEWEB)

Yortsos, Yanis C.

2002-10-08

In this report, the thrust areas include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.

Online gas composition estimation in solid oxide fuel cell systems with anode off-gas recycle configuration

Science.gov (United States)

Dolenc, B.; Vrečko, D.; Juričić, Ð.; Pohjoranta, A.; Pianese, C.

2017-03-01

Degradation and poisoning of solid oxide fuel cell (SOFC) stacks are continuously shortening the lifespan of SOFC systems. Poisoning mechanisms, such as carbon deposition, form a coating layer, hence rapidly decreasing the efficiency of the fuel cells. Gas composition of inlet gases is known to have great impact on the rate of coke formation. Therefore, monitoring of these variables can be of great benefit for overall management of SOFCs. Although measuring the gas composition of the gas stream is feasible, it is too costly for commercial applications. This paper proposes three distinct approaches for the design of gas composition estimators of an SOFC system in anode off-gas recycle configuration which are (i.) accurate, and (ii.) easy to implement on a programmable logic controller. Firstly, a classical approach is briefly revisited and problems related to implementation complexity are discussed. Secondly, the model is simplified and adapted for easy implementation. Further, an alternative data-driven approach for gas composition estimation is developed. Finally, a hybrid estimator employing experimental data and 1st-principles is proposed. Despite the structural simplicity of the estimators, the experimental validation shows a high precision for all of the approaches. Experimental validation is performed on a 10 kW SOFC system.

Experimental solid state NMR of gas hydrates : problems and solutions

Energy Technology Data Exchange (ETDEWEB)

Moudrakovski, I.; Lu, H.; Ripmeester, J. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences; Kumar, R.; Susilo, R. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Luzi, M. [GeoForschungsZentrum Potsdam, Potsdam (Germany)

2008-07-01

Solid State NMR is a suitable spectroscopic technique for hydrate research for several reasons, including its capability to distinguish between different structural types of hydrates, its quantitative nature and potential for both in-situ and time resolved experiments. This study illustrated the applications of solid state NMR for compositional and structural studies of clathrate hydrates, with particular emphasis on experimental techniques and potential ways to overcome technical difficulties. In order to use the method to its full capacity, some instrumental developments are needed to adapt it to the specific experimental requirements of hydrate studies, such as very low temperatures and high pressures. This presentation discussed the quantification of the Carbon-13 spectra with examples from natural and synthetic hydrates prepared from multi-component mixtures of hydrocarbons. The main approach used for the first two examples was Carbon-13 NMR with Magic Angle Spinning (MAS) at -100 degrees C. The detailed characterization of mixed hydrogen hydrates required low temperature hydrogen MAS. The quantification problems encountered during these experiments were also discussed. The purpose of these recent experimental developments was to prompt wider application of Solid State NMR in hydrate research. NMR proved to be a viable method for analyzing the composition and structure of multi-component mixed gas hydrates; characterizing natural gas hydrates; and, evaluating the formation conditions and properties of mixed hydrogen hydrates. The limitations of the method were highlighted and sensible choices of experimental conditions and techniques that ensure accurate results were discussed. 34 refs., 10 figs.

Configuration of a pulse radiolysis system for the study of gas-phase reactions and kinetic investigations of the reactions of hydroxyl radicals with methyl and ethyl radicals

International Nuclear Information System (INIS)

Fagerstroem, K.

1993-01-01

The work that is presented in this thesis deals with the assembling and testing of a pulse radiolysis system for kinetic studies of gas-phase reactions as well as with the kinetics of the gas-phase reactions of hydroxyl radicals with methyl and ethyl radicals. These radicals are very important as these are formed at an early stage in hydrocarbon combustion processes. The two studied reactions are key reactions in those processes. (6 refs., 4 figs., 2 tabs.)

Method for reactivating solid catalysts used in alkylation reactions

Science.gov (United States)

Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

2003-06-17

A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

Numerical Simulation of Dense Gas-Solid Fluidized Beds: A Multiscale Modeling Strategy

NARCIS (Netherlands)

van der Hoef, Martin Anton; van Sint Annaland, M.; Deen, N.G.; Kuipers, J.A.M.

2008-01-01

Gas-solid fluidized beds are widely applied in many chemical processes involving physical and/or chemical transformations, and for this reason they are the subject of intense research in chemical engineering science. Over the years, researchers have developed a large number of numerical models of

Numerical simulation of dense gas-solid fluidized beds : a multiscale modeling strategy

NARCIS (Netherlands)

Hoef, van der M.A.; Sint Annaland, van M.; Deen, N.G.; Kuipers, J.A.M.

2008-01-01

Gas-solid fluidized beds are widely applied in many chemical processes involving physical and/or chemical transformations, and for this reason they are the subject of intense research in chemical engineering science. Over the years, researchers have developed a large number of numerical models of

Lattice-enabled nuclear reactions in the nickel and hydrogen gas system

International Nuclear Information System (INIS)

Nagel, David J.

2015-01-01

Thousands of lattice-enabled nuclear reaction (LENR) experiments involving electrochemical loading of deuterium into palladium have been conducted and reported in hundreds of papers. But, it appears that the first commercial LENR power generators will employ gas loading of hydrogen onto nickel. This article reviews the scientific base for LENR in the gas-loaded Ni-H system, and some of the tests of pre-commercial prototype generators based on this combination. (author)

Analyzer for measurement of nitrogen oxide concentration by ozone content reduction in gas using solid state chemiluminescent sensor

Science.gov (United States)

Chelibanov, V. P.; Ishanin, G. G.; Isaev, L. N.

2014-05-01

Role of nitrogen oxide in ambient air is described and analyzed. New method of nitrogen oxide concentration measurement in gas phase is suggested based on ozone concentration measurement with titration by nitrogen oxide. Research of chemiluminescent sensor composition is carried out on experimental stand. The sensor produced on the base of solid state non-activated chemiluminescent composition is applied as ozone sensor. Composition is put on the surface of polymer matrix with developed surface. Sensor compositions includes gallic acid with addition of rodamine-6G. Model of interaction process between sensor composition and ozone has been developed, main products appeared during reaction are identified. The product determining the speed of luminescense appearance is found. This product belongs to quinone class. Then new structure of chemiluminescent composition was suggested, with absence of activation period and with high stability of operation. Experimental model of gas analyzer was constructed and operation algorithm was developed. It was demonstrated that developed NO measuring instrument would be applied for monitoring purposes of ambient air. This work was partially financially supported by Government of Russian Federation, Grant 074-U01

Chloride pyrometallurgy of uranium ore. 1. Chlorination of phosphate ore using solid or gas chlorinating agent and carbon

International Nuclear Information System (INIS)

Taki, Tomihiro; Komoto, Shigetoshi; Otomura, Keiichiro; Takenaka, Toshihide; Sato, Nobuaki; Fujino, Takeo.

1995-01-01

A thermodynamical and pyrometallurgical study to recover uranium from the phosphate ores was undertaken using the chloride volatilization method. Iron was chlorinated with solid chlorinating agents such as NaCl and CaCl 2 in combination with activated carbon, which will be used for removing this element from the ore, but uranium was not. On the other hand, the chlorination using Cl 2 gas and activated carbon gave a good result at 1,223 K. Not only uranium but also iron, phosphorus, aluminum and silicon were found to form volatile chlorides which vaporized out of the ore, while calcium remained in the ore as non-volatile CaCl 2 . The chlorination condition was studied as functions of temperature, reaction time and carbon content. The volatilization ratio of uranium around 95% was obtained by heating the mixture of the ore and activated carbon (35 wt%) in a mixed gas flow of Cl 2 (200 ml/min) and N 2 (200 ml/min) at 1,223 K for 120 min. (author)

Reaction behavior of SO2 in the sintering process with flue gas recirculation.

Science.gov (United States)

Yu, Zhi-Yuan; Fan, Xiao-Hui; Gan, Min; Chen, Xu-Ling; Chen, Qiang; Huang, Yun-Song

2016-07-01

The primary goal of this paper is to reveal the reaction behavior of SO2 in the sinter zone, combustion zone, drying-preheating zone, and over-wet zone during flue gas recirculation (FGR) technique. The results showed that SO2 retention in the sinter zone was associated with free-CaO in the form of CaSO3/CaSO4, and the SO2 adsorption reached a maximum under 900ºC. SO2 in the flue gas came almost from the combustion zone. One reaction behavior was the oxidation of sulfur in the sintering mix when the temperature was between 800 and 1000ºC; the other behavior was the decomposition of sulfite/sulfate when the temperature was over 1000ºC. However, the SO2 adsorption in the sintering bed mainly occurred in the drying-preheating zone, adsorbed by CaCO3, Ca(OH)2, and CaO. When the SO2 adsorption reaction in the drying-preheating zone reached equilibrium, the excess SO2 gas continued to migrate to the over-wet zone and was then absorbed by Ca(OH)2 and H2O. The emission rising point of SO2 moved forward in combustion zone, and the concentration of SO2 emissions significantly increased in the case of flue gas recirculation (FGR) technique. Aiming for the reuse of the sensible heat and a reduction in exhaust gas emission, the FGR technique is proposed in the iron ore sintering process. When using the FGR technique, SO2 emission in exhaust gas gets changed. In practice, the application of the FGR technique in a sinter plant should be cooperative with the flue gas desulfurization (FGD) technique. Thus, it is necessary to study the influence of the FGR technique on SO2 emissions because it will directly influence the demand and design of the FGD system.

Application of process tomography in gas-solid fluidised beds in different scales and structures

Science.gov (United States)

Wang, H. G.; Che, H. Q.; Ye, J. M.; Tu, Q. Y.; Wu, Z. P.; Yang, W. Q.; Ocone, R.

2018-04-01

Gas-solid fluidised beds are commonly used in particle-related processes, e.g. for coal combustion and gasification in the power industry, and the coating and granulation process in the pharmaceutical industry. Because the operation efficiency depends on the gas-solid flow characteristics, it is necessary to investigate the flow behaviour. This paper is about the application of process tomography, including electrical capacitance tomography (ECT) and microwave tomography (MWT), in multi-scale gas-solid fluidisation processes in the pharmaceutical and power industries. This is the first time that both ECT and MWT have been applied for this purpose in multi-scale and complex structure. To evaluate the sensor design and image reconstruction and to investigate the effects of sensor structure and dimension on the image quality, a normalised sensitivity coefficient is introduced. In the meantime, computational fluid dynamic (CFD) analysis based on a computational particle fluid dynamic (CPFD) model and a two-phase fluid model (TFM) is used. Part of the CPFD-TFM simulation results are compared and validated by experimental results from ECT and/or MWT. By both simulation and experiment, the complex flow hydrodynamic behaviour in different scales is analysed. Time-series capacitance data are analysed both in time and frequency domains to reveal the flow characteristics.

Experimenting with a Visible Copper-Aluminum Displacement Reaction in Agar Gel and Observing Copper Crystal Growth Patterns to Engage Student Interest and Inquiry

Science.gov (United States)

Xu, Xinhua; Wu, Meifen; Wang, Xiaogang; Yang, Yangyiwei; Shi, Xiang; Wang, Guoping

2016-01-01

The reaction process of copper-aluminum displacement in agar gel was observed at the microscopic level with a stereomicroscope; pine-like branches of copper crystals growing from aluminum surface into gel at a constant rate were observed. Students were asked to make hypotheses on the pattern formation and design new research approaches to prove…

Determination of tolerances of mirror displacement and radiator gas impurity for the CBM RICH detector

Energy Technology Data Exchange (ETDEWEB)

Adamczewski-Musch, J. [GSI Darmstadt (Germany); Becker, K.-H. [University Wuppertal (Germany); Belogurov, S. [ITEP Moscow (Russian Federation); Boldyreva, N. [PNPI Gatchina (Russian Federation); Chernogorov, A. [ITEP Moscow (Russian Federation); Deveaux, C. [University Gießen (Germany); Dobyrn, V. [PNPI Gatchina (Russian Federation); Dürr, M. [University Gießen (Germany); Eom, J. [Pusan National University (Korea, Republic of); Eschke, J. [GSI Darmstadt (Germany); Höhne, C. [University Gießen (Germany); Kampert, K.-H. [University Wuppertal (Germany); Kleipa, V. [GSI Darmstadt (Germany); Kochenda, L. [PNPI Gatchina (Russian Federation); Kolb, B. [GSI Darmstadt (Germany); Kopfer, J. [University Wuppertal (Germany); Kravtsov, P. [PNPI Gatchina (Russian Federation); Lebedev, S.; Lebedeva, E. [University Gießen (Germany); Leonova, E. [PNPI Gatchina (Russian Federation); and others

2014-12-01

The CBM experiment at the future FAIR facility will explore nuclear matter at high net-baryon densities. One of the key observables is di-leptons as they penetrate the created matter without further strong interactions. A gaseous RICH detector in a standard projective geometry using spherical mirrors is one of two detector elements for the required electron identification. The mirror system consists of about 72 trapezoidal mirror tiles. Any misalignment between the tiles relative to the nominal common spherical surface leads to reduction of the reconstruction efficiency of Cherenkov rings and deterioration of their resolution. To determine tolerances in mirror misalignment extensive simulation and measurement studies were carried out. Pure CO{sub 2} will be used as radiator gas. Gas contamination, mainly moisture and Oxygen, reduces the number of detected photons per ring and worsens the quality of reconstructed Cherenkov rings. Therefore a study was carried out to determine tolerances in radiator gas contamination. - Highlights: • Mirror misalignment leads to ring deformation in a RICH detector. • Radiator contamination leads to resolution deterioration of fitted rings. • To determine tolerances measurements and simulations were carried out. • Mirror displacements of up to 0.32 mm at any mirror side can be tolerated. • Oxygen (moisture) contamination of up to 1% (0.0011%) can be safely tolerated.

Reaction mechanism of reductive decomposition of FGD gypsum with anthracite

International Nuclear Information System (INIS)

Zheng, Da; Lu, Hailin; Sun, Xiuyun; Liu, Xiaodong; Han, Weiqing; Wang, Lianjun

2013-01-01

Highlights: • The reaction mechanism was different if the molar ratio of C/CaSO 4 was different. • The yield of CaO rises with an increase in temperature. • The optimal ratio of C/CaSO 4 = 1.2:1. • The decomposition process is mainly apparent solid–solid reaction with liquid-phase involved. - Abstract: The process of decomposition reaction between flue gas desulfurization (FGD) gypsum and anthracite is complex, which depends on the reaction conditions and atmosphere. In this study, thermogravimetric analysis with Fourier transform infrared spectroscopy (TGA-FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and the experiment in a tubular reactor were used to characterize the decomposition reaction in a nitrogen atmosphere under different conditions. The reaction mechanism analysis showed that the decomposition reaction process and mechanism were different when the molar proportion of C/CaSO 4 was changed. The experiment results showed that appropriate increase in the C/CaSO 4 proportion and higher temperatures were suitable for the formation of the main production of CaO, which can help us to understand the solid state reaction mechanism better. Via kinetic analysis of the reaction between anthracite and FGD gypsum under the optimal molar ratio of C/CaSO 4 , the mechanism model of the reaction was confirmed and the decomposition process was a two-step reaction which was in accordance with apparent solid–solid reaction

Hydrogen/Chlorine exchange reactions of gaseous carbanions.

Science.gov (United States)

Chen, Hao; Cooks, R Graham; Meurer, Eduardo C; Eberlin, Marcos N

2005-12-01

Gas-phase reactions of three typical carbanions CH(2)NO(2)(-), CH(2)CN(-), and CH(2)S(O)CH(3)(-) with the chloromethanes CH(2)Cl(2), CHCl(3), and CCl(4), examined by tandem mass spectrometry, show a novel hydrogen/chlorine exchange reaction. For example, reaction between the nitromethyl anion CH(2)NO(2)(-) and carbon tetrachloride CCl(4) forms the ion CHClNO(2)(-). The suggested reaction mechanism involves nucleophilic attack by CH(2)NO(2)(-) at the chlorine of CCl(4) followed by proton transfer within the resulting complex [CH(2)ClNO(2) + CCl(3)(-)] to form CHClNO(2)(-) and CHCl(3). Two other carbanions CH(2)CN(-) and CH(2)S(O)CH(3)(-) also undergo the novel hydrogen/chlorine exchange reactions with CCl(4) but to a much smaller extent, their higher nucleophilicities favoring competitive nucleophilic attack reactions. Proton abstraction is the exclusive pathway in the reactions of these carbanions with CHCl(3). While CH(2)CN(-) and CH(2)S(O)CH(3)(-) promote mainly proton abstraction and nucleophilic displacement in reactions with CH(2)Cl(2), CH(2)NO(2)(-) does not react.

Delignification of softwood kraft pulp by chlorine dioxide in a laboratory bleaching liquor displacement reactor

International Nuclear Information System (INIS)

Hamzeh, Y.; Izadyar, S.

2008-01-01

The chlorine dioxide delignification efficiency of softwood kraft pulp in the laboratory liquor displacement reactor (fixed bed reactor) was investigated and compared with conventional batch reactor. The comparison of two reactors was made based on the effective efficiency and overall efficiency of chlorine dioxide. Effective efficiency corresponds to the oxidizing capacity of chlorine dioxide which consumed by organic materials. Comparison of two reactors based on the effective efficiency showed that the selectivity of delignification significantly enhanced in the displacement reactor in which the primary reaction products are eliminated from reaction zone by displacing flow. On the other hand, the formation of high amounts of chlorate in the reaction zone of displacement reactor reduces the overall efficiency of chlorine dioxide delignification stage. Thus, in spite of significant decrease in useless secondary reactions, this type of reactor would not be cost effective in the industrial scale

Synthesising and comparing electrical properties of NTC thermistors prepared from nano powder and solid state reaction

International Nuclear Information System (INIS)

Azad, N.; Ghanbari Shohany, B.; Hosseini, S. M.; Kompany, A.

2011-01-01

In this research, NTC thermistors with composition of NiMn 2-x Co x O 4 (x = 0.4, 0.8, 1.2, 1.6) prepared by two methods: solid state reaction and sol-gel (gel-combustion). The average particle size was monitored and structure of the calcinated powders have been investigated using x-ray diffraction and tunneling electron microscopy techniques. The average particle size was estimated to be about 65 nm with the cubic and cubic + tetragonal phases for low and high cobalt concentrations, respectively. The grain size of samples verifies with scanning electron microscopy images. Upon increasing the cobalt fraction, the grain size of samples increases from about 2μm to a few μm in size. The electrical properties of these thermistors depend on the grain size. The grain size of samples made from sol-gel is smaller than from solid state reaction under the same condition. For longer sintering time of the samples prepared by gel-combustion method, the grain size was increased then the electrical parameters of nano powder improved and we obtain better results than the samples prepared from solid state reaction.

Gas phase reactions of nitrogen oxides with olefins

Energy Technology Data Exchange (ETDEWEB)

Altshuller, A P; Cohen, I

1961-01-01

The nature of the condensation products formed in the gas phase reactions of nitrogen dioxide and nitric oxide with pentene-1, 2-methylbutene-2, and 2-methylbutadiene-1,3 was investigated. The reactants were combined at partial pressures in the range of 0.1 to 2.5 mm with the total pressure at one atmosphere. The products were determined by infrared and ultraviolet spectroscopy and colorimetry. The condensates included primary and secondary nitro compounds and alkyl nitrates. Strong hydroxyl and single bond carbon to oxygen stretching vibrations indicate the presence of either nitroalcohols or simple aliphatic alcohols formed through oxidation reactions. Carbonyl stretching frequencies observable in some of the reactions support the conclusion that a portion of the reactants disappear by oxidation rather than by nitration processes. The available results do not indicate the presence of appreciable amounts of tert.-nitro compounds, conjugated nitro-olefins, or gem-dinitro-alkanes. The reactivities of the olefins with the nitrogen oxides are in the decreasing order: 2-methyl-butadiene-1,3, 2-methylbutene-2, pentene-1. 20 references.

Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber

KAUST Repository

Shi, Xian

2017-01-05

Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber are numerically investigated using an 1-D unsteady, shock-capturing, compressible and reacting flow solver. Different combinations of reaction front propagation and end-gas combustion modes are observed, i.e., 1) deflagration without end-gas combustion, 2) deflagration to end-gas autoignition, 3) deflagration to end-gas detonation, 4) developing or developed detonation, occurring in the sequence of increasing initial temperatures. Effects of ignition location and chamber size are evaluated: the asymmetric ignition is found to promote the reactivity of unburnt mixture compared to ignitions at center/wall, due to additional heating from asymmetric pressure waves. End-gas combustion occurs earlier in smaller chambers, where end-gas temperature rise due to compression heating from the deflagration is faster. According to the ξ−ε regime diagram based on Zeldovich theory, modes of reaction front propagation are primarily determined by reactivity gradients introduced by initial ignition, while modes of end-gas combustion are influenced by the total amount of unburnt mixture at the time when autoignition occurs. A transient reactivity gradient method is provided and able to capture the occurrence of detonation.

Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber

KAUST Repository

Shi, Xian; Ryu, Je Ir; Chen, Jyh-Yuan; Dibble, Robert W.

2017-01-01

Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber are numerically investigated using an 1-D unsteady, shock-capturing, compressible and reacting flow solver. Different combinations of reaction front propagation and end-gas combustion modes are observed, i.e., 1) deflagration without end-gas combustion, 2) deflagration to end-gas autoignition, 3) deflagration to end-gas detonation, 4) developing or developed detonation, occurring in the sequence of increasing initial temperatures. Effects of ignition location and chamber size are evaluated: the asymmetric ignition is found to promote the reactivity of unburnt mixture compared to ignitions at center/wall, due to additional heating from asymmetric pressure waves. End-gas combustion occurs earlier in smaller chambers, where end-gas temperature rise due to compression heating from the deflagration is faster. According to the ξ−ε regime diagram based on Zeldovich theory, modes of reaction front propagation are primarily determined by reactivity gradients introduced by initial ignition, while modes of end-gas combustion are influenced by the total amount of unburnt mixture at the time when autoignition occurs. A transient reactivity gradient method is provided and able to capture the occurrence of detonation.

Gas to liquid to solid transition in halogen hot atom chemistry. 6. Product formation routes and chemical selectivity of high energy iodine reactions with butyne isomers

International Nuclear Information System (INIS)

Garmestani, S.K.; Firouzbakht, M.L.; Rack, E.P.

1979-01-01

Reactions of recoil produced iodine-128 with isomers of butyne were studied in gaseous, high pressure, and condensed phase conditions, with rare gas additives and in the presence and absence of radical scavengers (I 2 and O 2 ). It was found that recoil iodine-128 reactions were initiated by thermal electronically excited I + species for both 1-butyne and 2-butyne systems. While the diverse and complex nature of the reactions cannot be explained by simple chemical parameters, comparisons among the alkyne systems demonstrate preferential attack of iodine at the triple bond resulting, mainly, in electronically excited intermediates. A comparison of the various product formation routes results in the characterization of general traits common to the alkynes. 6 figures, 4 tables

Biogasification of solid wastes by two-phase anaerobic fermentation

International Nuclear Information System (INIS)

Ghosh, S.; Vieitez, E.R.; Liu, T.; Kato, Y.

1997-01-01

Municipal, industrial and agricultural solid wastes, and biomass deposits, cause large-scale pollution of land and water. Gaseous products of waste decomposition pollute the air and contribute to global warming. This paper describes the development of a two-phase fermentation system that alleviates methanogenic inhibition encountered with high-solids feed, accelerates methane fermentation of the solid bed, and captures methane (renewable energy) for captive use to reduce global warming. The innovative system consisted of a solid bed reactor packed with simulated solid waste at a density of 160 kg/m 3 and operated with recirculation of the percolated culture (bioleachate) through the bed. A rapid onset of solids hydrolysis, acidification, denitrification and hydrogen gas formation was observed under these operating conditions. However, these fermentative reactions stopped at a total fatty acids concentration of 13,000 mg/l (as acetic) at pH 5, with a reactor head-gas composition of 75 percent carbon dioxide, 20 percent nitrogen, 2 percent hydrogen and 3 percent methane. Fermentation inhibition was alleviated by moving the bioleachate to a separate methane-phase fermenter, and recycling methanogenic effluents at pH 7 to the solid bed. Coupled operation of the two reactors promoted methanogenic conversion of the high-solids feed. (author)

Surface chemical reactions induced by molecules electronically-excited in the gas

DEFF Research Database (Denmark)

Petrunin, Victor V.

2011-01-01

and alignment are taking place, guiding all the molecules towards the intersections with the ground state PES, where transitions to the ground state PES will occur with minimum energy dissipation. The accumulated kinetic energy may be used to overcome the chemical reaction barrier. While recombination chemical...... be readily produced. Products of chemical adsorption and/or chemical reactions induced within adsorbates are aggregated on the surface and observed by light scattering. We will demonstrate how pressure and spectral dependencies of the chemical outcomes, polarization of the light and interference of two laser...... beams inducing the reaction can be used to distinguish the new process we try to investigate from chemical reactions induced by photoexcitation within adsorbed molecules and/or gas phase photolysis....

kinetics of the coupled gas-iron reactions involving silicon and carbon

African Journals Online (AJOL)

user

1985-09-01

Sep 1, 1985 ... out for the system involving liquid iron containing carbon and silicon and a gas ... in content with liquid iron at. 15600C, the ... of carbon monoxide bubbles at the. Slag - metal ..... equilibrium strongly make chemical reactions.

CFD simulation of a dry scroll vacuum pump with clearances, solid heating and thermal deformation

Science.gov (United States)

Spille-Kohoff, A.; Hesse, J.; Andres, R.; Hetze, F.

2017-08-01

Although dry scroll vacuum pumps (DSPV) are essential devices in many different industrial processes, the CFD simulation of such pumps is not widely used and often restricted to simplified cases due to its complexity: The working principle with a fixed and an orbiting scroll leads to working chambers that are changing in time and are connected through moving small radial and axial clearances in the range of 10 to 100 μm. Due to the low densities and low mass flow rates in vacuum pumps, it is important to include heat transfer towards and inside the solid components. Solid heating is very slow compared to the scroll revolution speed and the gas behaviour, thus a special workflow is necessary to reach the working conditions in reasonable simulation times. The resulting solid temperature is then used to compute the thermal deformation, which usually results in gap size changes that influence leakage flows. In this paper, setup steps and results for the simulation of a DSVP are shown and compared to theoretical and experimental results. The time-varying working chambers are meshed with TwinMesh, a hexahedral meshing programme for positive displacement machines. The CFD simulation with ANSYS CFX accounts for gas flow with compressibility and turbulence effects, conjugate heat transfer between gas and solids, and leakage flows through the clearances. Time-resolved results for torques, chamber pressure, mass flow, and heat flow between gas and solids are shown, as well as time- and space-resolved results for pressure, velocity, and temperature for different operating conditions of the DSVP.

Non-equilibrium thermodynamics of highly rarefied neutron gas under creative and destructive reactions

International Nuclear Information System (INIS)

Hayasaka, Hideo

1978-01-01

The thermodynamic structures of non-equilibrium steady states of a highly rarefied neutron gas in various media are considered in terms of the irreversible processes due to creative and destructive reactions of neutrons with nuclei of these media and to neutrons supplied from external sources. The respective subsystems of the stationary neutron gas are regarded as imperfect equilibrium systems in the presence of the medium and the external neutron sources, and are treated like different species in a mixture. The entropy production due to neutron-nuclear reactions has a minimum value at the steady state. The distribution function of such a neutron gas is determined from the extremum condition in which entropy does not change, and is expressed as a shifted Boltzmann distribution specified by the respective values of the generalized chemical potential for each energy level. (author)

Solar-wind krypton and solid/gas fractionation in the early solar nebula

Science.gov (United States)

Wiens, Roger C.; Burnett, D. S.; Neugebauer, M.; Pepin, R. O.

1991-01-01

The solar-system Kr abundance is calculated from solar-wind noble-gas ratios, determined previously by low-temperature oxidations of lunar ilmenite grains, normalized to Si by spacecraft solar-wind measurements. The estimated Kr-83 abundance of 4.1 + or - 1.5 per million Si atoms is within uncertainty of estimates assuming no fractionation, determined from CI-chondrite abundances of surrounding elements. This is significant because it is the first such constraint on solid/gas fractionation, though the large uncertainty only confines it to somewhat less than a factor of two.

Ion-beam mixing and solid-state reaction in Zr-Fe multilayers

International Nuclear Information System (INIS)

Paesano, A. Jr.; Motta, A.T.; Birtcher, R.C.; Ryan, E.A.; Teixeira, S.R.; Bruckmann, M.E.; Amaral, L.

1997-01-01

Vapor-deposited Zr-Fe multilayered thin films with various wavelengths and of overall composition either 50% Fe or Fe-rich up to 57% Fe were either irradiated with 300 keV Kr ions at temperatures from 25 K to 623 K to fluences up to 2 x 10 16 cm -2 , or simply annealed at 773 K in-situ in the Intermediate Voltage Electron microscope At Argonne National Laboratory. Under irradiation, the final reaction product is the amorphous phase in all cases studied, but the dose to amorphization depends on the temperature and on the wavelength. In the purely thermal case (annealing at 773 K), the 50-50 composition produces the amorphous phase but for the Fe-rich multilayers the reaction products depend on the multilayer wavelength. For small wavelength, the amorphous phase is still formed, but at large wavelength the Zr-Fe crystalline intermetallic compounds appear. These results are discussed in terms of existing models of irradiation kinetics and phase selection during solid state reaction

Assessment of potential greenhouse gas mitigation of available household solid waste treatment technologies

Directory of Open Access Journals (Sweden)

Hoang Minh Giang

2013-11-01

Full Text Available Current household solid waste treatment practices in most cities in Vietnam caused a great amount of direct greenhouse gas (GHG emissions. Available solid waste treatment technologies should be seriously taken  into consideration as a wedge of GHG mitigation in waste sector base on presently Vietnamese economic conditions. This study aim to evaluate the potential amount of GHG mitigation from current domestic solid waste treatment technologies in Vietnam including landfills and composting from various management scenarios. In oder to use Tier 2 model of IPCC 2006 for GHG estimation from landfills, an analysis on current household solid waste management system of the city was obtained by using material flow analysis approach. A case study in Hanoi, the capital city of Vietnam was carried out in this research. As a result, there was a reduced of over 70% of the amount of CH4 emissions and  up to 53% of total GHG saving (CO2-eq from avoiding organic waste to landfill. In addition, applying an energy recovery from LFG system to available landfills would lead to aproximately 75% of GHG saved compare to current emission of waste sector.Doi: http://dx.doi.org/10.12777/wastech.1.1.10-16Citation: Giang, H.M.,Luong, N.D., and Huong, L.T.M.2013. Assessment of potential greenhouse gas mitigation of available household solid waste treatment technologies. . Waste Technology 1(1:6-9. Doi: http://dx.doi.org/10.12777/wastech.1.1.10-16

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions.

Science.gov (United States)

Brack, Paul; Dann, Sandie; Wijayantha, K G Upul; Adcock, Paul; Foster, Simon

2016-08-17

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

Term value/band-gap energy correlations for solid rare gas excitons

International Nuclear Information System (INIS)

Anon.

1987-01-01

Term value/ionization energy correlation algorithms have proven to be of considerable utility in the assignment of atomic and molecular Rydberg states. Many examples of empirical term value/ionization energy correlations are known for diverse classes of atoms and molecules. The purpose of this paper is to demonstrate that similar correlations are also obtained for excitons in rare gas solids

Charged Porous Polymers using a Solid C-O Cross-Coupling Reaction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pengfei; Jiang, Xueguang; Wan, Shun; Dai, Sheng

2015-07-15

Here in this paper, we report a green, fast, efficient mechanochemical strategy for charged porous polymers (CPPs). A cationic CPP with basic anions and an anionic CPP with Li+ cations were fabricated by solid grinding under solvent-free conditions. Compared with solution-based synthesis, mechanochemical grinding can shorten the reaction time from dozens of hours to several minutes (60–90 min) to form polymers possessing a high molecular mass and low polydispersity. During the construction of CPPs, a Pd-catalyzed solid polycondensation based on unactivated organic linkers was introduced. In particular, CPPs with basic phenolic or proline anions showed good activity and stability in SO2 capture, and Li+-functionalized CPPs can be post-modified to CPPs with other metal ions by ion exchange, highlighting the tailorable feature of ionic-modified CPPs.

Charged Porous Polymers using a Solid C-O Cross-Coupling Reaction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pengfei; Jiang, Xueguang; Wan, Shun; Dai, Sheng

2015-07-15

Herein, we report a green, fast, efficient mechanochemical strategy for charged porous polymers (CPPs). A cationic CPP with basic anions and an anionic CPP with Li+ cations were fabricated by solid grinding under solvent-free conditions. Compared with solution-based synthesis, mechanochemical grinding can shorten the reaction time from dozens of hours to several minutes (60–90 min) to form polymers possessing a high molecular mass and low polydispersity. During the construction of CPPs, a Pd-catalyzed solid polycondensation based on unactivated organic linkers was introduced. In particular, CPPs with basic phenolic or proline anions showed good activity and stability in SO2 capture, and Li+-functionalized CPPs can be post-modified to CPPs with other metal ions by ion exchange, highlighting the tailorable feature of ionic-modified CPPs.

Catalytic reaction in a porous solid subject to a boundary layer flow

Energy Technology Data Exchange (ETDEWEB)

Mihail, R; Teddorescu, C

1978-01-01

A mathematical model of a boundary layer flowing past a catalytic slab was developed which included an analysis of the coupled mass and heat transfer and the heterogeneous chemical reaction. The porous flat plate was used to illustrate the interaction of boundary layer flow with chemical reaction within a porous catalytic body. The model yielded systems of transcendental equations which were solved numerically by means of a superposition integral in connection with a norm reduction procedure. A parametric study was conducted and an analysis of the possible multiplicity of steady states was developed and illustrated for the extreme case of infinite solid thermal conductivity. Tables, diagrams, graphs, and 12 references.

Prolonged displacement may compromise resilience in Eritrean mothers.

Science.gov (United States)

Almedom, Astier; Tesfamichael, Berhe; Mohammed, Zein; Mascie-Taylor, Nick; Muller, Jocelyn; Alemu, Zemui

2005-12-01

to assess the impact of prolonged displacement on the resilience of Eritrean mothers. an adapted SOC scale (short form) was administered. Complementary qualitative data were gathered from study participants' spontaneous reactions to and commentaries on the SOC scale. Displaced women's SOC scores were significantly less than those of the non-displaced: Mean = 54.84; SD = 6.48 in internally displaced person (IDP) camps, compared to non-displaced urban and rural/pastoralist: Mean = 48. 94, SD = 11.99; t = 3.831, p urban (non-displaced). Rural but traditionally mobile (pastoralist or transhumant) communities scored more or less the same as the urban non-displaced--i.e., significantly higher than those in IDP camps (p urban and pastoralist/transhumant groups were similar, while women in IDP camps were lower scoring--RR = .268, p < .001. The implications of these findings for health policy are critical. It is incumbent on the international health institutions including the World Health Organization and regional as well as local players to address the plight of internally displaced women, their families and communities in Eritrea and other places of dire conditions such as, for example Darfur in the Sudan.

Conditioning of radioactive ash residue in a wave of solid-phase exothermal reactions

International Nuclear Information System (INIS)

Karlina, O.K.; Varlakova, G.A.; Ozhovan, M.I.; Tivanskij, V.M.; Dmitriev, S.A.

2001-01-01

The abilities for utilization of exothermic reaction heat in solid phase for conditioning the ash residue produced as a result of solid radioactive waste burning are analyzed. It is shown that the process of ash residue making monolithic with obtaining the glass-like finish product containing 50-60 mass % of ash residue which meets the requirements for solidified radioactive wastes may be realized without energy supplying from external heat sources. The conditioning is realized in a special crucible furnace-container designed not only for the process conducting but also for subsequent storage or disposal of the finish product [ru

Isotope exchange reaction in Li2ZrO3 packed bed

International Nuclear Information System (INIS)

Kawamura, Y.; Enoeda, M.; Okuno, K.

1998-01-01

To understand the release behavior of bred tritium in a solid breeder blanket, the tritium transfer rate and tritium inventory for various mass transfer processes should be investigated. The contribution of the surface reactions (adsorption, desorption and two kinds of isotope exchange reactions) to the release process cannot be ignored. It is believed that two kinds of isotope exchange reactions (gaseous hydrogen-tritiated water and water vapor-tritiated water) occur on the surface of the solid breeder materials when hydrogen is added to the sweep gas to enhance the tritium release rate. The isotope exchange reaction study in H-D systems was carried out using a Li 2 ZrO 3 packed bed. The exchange reaction between gaseous hydrogen and water was the rate controlling step among the two kinds of exchange reactions. The reaction rate constants were quantified, and experimental equations were proposed. The equilibrium constant of the isotope exchange reaction in the H-D system was obtained from experimental data and was found to be 1.17. (orig.)

Fabrication of AlN-TiC/Al composites by gas injection processing

Institute of Scientific and Technical Information of China (English)

YU Huashun; CHEN Hongmei; MA Rendian; MIN Guanghui

2006-01-01

The fabrication of AlN-TiC/Al composites by carbon-and nitrogen-containing gas injection into Al-Mg-Ti melts was studied. It was shown that AlN and TiC particles could be formed by the in situ reaction of mixture gas (N2+C2H2+NH3) with Al-Mg-Ti melts. The condition for the formation of AlN was that the treatment temperature must be higher than 1373 K, and the amounts of AlN and TiC increased with the increase of the treatment temperature and the gas injection time.It was considered that AlN was formed by the direct reaction of Al with nitrogen-containing gas at the interface of the gas bubble and the melt. However, the mechanism of TiC formation is a combination mechanism of solution-precipitation and solid-liquid reaction.

Universal, colorimetric microRNA detection strategy based on target-catalyzed toehold-mediated strand displacement reaction

Science.gov (United States)

Park, Yeonkyung; Lee, Chang Yeol; Kang, Shinyoung; Kim, Hansol; Park, Ki Soo; Park, Hyun Gyu

2018-02-01

In this work, we developed a novel, label-free, and enzyme-free strategy for the colorimetric detection of microRNA (miRNA), which relies on a target-catalyzed toehold-mediated strand displacement (TMSD) reaction. The system employs a detection probe that specifically binds to the target miRNA and sequentially releases a catalyst strand (CS) intended to trigger the subsequent TMSD reaction. Thus, the presence of target miRNA releases the CS that mediates the formation of an active G-quadruplex DNAzyme which is initially caged and inactivated by a blocker strand. In addition, a fuel strand that is supplemented for the recycling of the CS promotes another TMSD reaction, consequently generating a large number of active G-quadruplex DNAzymes. As a result, a distinct colorimetric signal is produced by the ABTS oxidation promoted by the peroxidase mimicking activity of the released G-quadruplex DNAzymes. Based on this novel strategy, we successfully detected miR-141, a promising biomarker for human prostate cancer, with high selectivity. The diagnostic capability of this system was also demonstrated by reliably determining target miR-141 in human serum, showing its great potential towards real clinical applications. Importantly, the proposed approach is composed of separate target recognition and signal transduction modules. Thus, it could be extended to analyze different target miRNAs by simply redesigning the detection probe while keeping the same signal transduction module as a universal signal amplification unit, which was successfully demonstrated by analyzing another target miRNA, let-7d.

Gas phase ion/molecule reactions as studied by Fourier Transform Ion Cyclotron Resonance mass spectrometry

International Nuclear Information System (INIS)

Joergensen, S.I.

1985-01-01

The subject of this thesis is gas phase ion/molecule reactions as studied by Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry (chapter 2 contains a short description of this method). Three chapters are mainly concerned with mechanistic aspects of gas phase ion/molecule reactions. An equally important aspect of the thesis is the stability and reactivity of α-thio carbanions, dipole stabilized carbanions and homoenolate anions, dealt with in the other four chapters. (Auth.)

The effect of B_2O_3 flux on growth NLBCO superconductor by solid state reaction and wet-mixing methods

International Nuclear Information System (INIS)

Suharta, W. G.; Wendri, N.; Ratini, N.; Suarbawa, K. N.

2016-01-01

The synthesis of B_2O_3 flux substituted NLBCO superconductor NdBa_1_._7_5La_0_._2_5Cu_3O_7_-_∂ has been done using solid state reaction and wet-mixing methods in order to obtain homogeneous crystals and single phase. From DTA/TGA characteritations showed the synthesis process by wet-mixing requires a lower temperature than the solid state reaction in growing the superconductor NdBa_1_._7_5La_0_._2_5Cu_3O_7_-_∂. Therefore, in this research NdBa_1_._7_5La_0_._2_5Cu_3O_7_-_∂ sample calcinated at 650°C for wet-mixing method and 820°C for solid state reaction methods. The all samples was sintered at 950°C for ten hours. Crystallinity of the sample was confirmed using X-ray techniques and generally obtained sharp peaks that indicates the sample already well crystallized. Search match analyses for diffraction data gave weight fractions of impurity phase of the solid state reaction method higher than wet-mixing method. In this research showed decreasing the price of the lattice parameter about 1% with the addition of B_2O_3 flux for the both synthesis process and 2% of wet mixing process for all samples. Characterization using scanning electron microscopy (SEM) showed the distribution of crystal zise for wet-mixing method more homogeneous than solid state reaction method, with he grain size of samples is around 150–250 nm. The results of vibrating sample magnetometer (VSM) showed the paramagnetic properties for all samples.

Thermal theory of autowave processes in low-temperature solid-phase radiochemical reactions

International Nuclear Information System (INIS)

Barelko, V.V.; Barkalov, I.M.; Vaganov, D.A.; Zanin, A.M.; Kiryukhin, D.P.

1982-01-01

A new phenomenon in radiation cryochemistry concerning the class of autowave processes was previously discovered. It was observed in halogenation and hydrohalogenation of hydrocarbons and consisted of spontaneous, laminar propagation of a chemical transformation wave based on a frozen mixture of reagents previously irradiated with 60 Co γ-rays. The effect of the positive inverse correlation between the chemical conversion and brittle fracture of a solid sample of reagents is the phenomenological basis of the phenomenon; formation of fractures triggers a reactive process which takes place on their active surface (or in the layer adjacent to it), and the chemical reaction, in turn, stimulates the subsequent development of the process of decomposition. As a result, a single brittle fracture and chemical conversion wave which moves along the solid sample arises. Different mechanisms of generation of fracture surfaces under the effect of the reaction are possible. A difference in the densities of the initial reagents and the products of the reaction could be one of the causes of brittle fracture, and the thermal stresses induced by the exothermicity of the chemical processes could be another cause. The present work concerns the analysis of the features of the wave process which occurs based on the second, thermal mechanism. The analysis was conducted within the framework of a phenomenological approach which does not require specific definition of the nature of the chemical activation of the system during its brittle fracture

Measurement of interfacial displacement of a liquid film in microchannels using laser focus displacement meter

International Nuclear Information System (INIS)

Hazuku, Tatsuya; Fukamachi, Norihiro; Takamasa, Tomoji; Hibiki, Takashi

2004-01-01

This paper presents a new method for measuring the interfacial displacement of a liquid film in microchannels using a laser focus displacement meter (LFD). The purpose of the study is to clarify the effectiveness of the new method for obtaining detailed information concerning interfacial displacement, especially in the case of a thin liquid film, in micro- and mini-channels. To prevent the tube wall signal from disturbing that of the gas-liquid interface, a fluorocarbon tube with water box was used; the refraction index of this device is same as that for water. With this method, accurate instantaneous measurements of interfacial displacement of the liquid film were achieved. The error caused by refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated analytically and experimentally. The formulated analytical equation can estimate the real interface displacement using measured displacement in a fluorocarbon tube of 25 μm to 2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 and 2 mm I.D. showed that the corrected interface displacement calculated by the equation agreed with real displacement within a 1% margin of error. It was also confirmed that the LFD in the system could measure a liquid film of 0.25 μm at the thinnest. We made simultaneous measurements of the interface in fluorocarbon tubes of 0.5 and 1 mm I.D. using the LFD and a high-speed video camera with a microscope. These showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow regimes. The data also clarified the existence of a thin liquid film less than 1 μm in thickness in slug and annular flow regions. (author)

Formation of amorphous Ti-50at.%Pt by solid state reactions during mechanical alloying

CSIR Research Space (South Africa)

Mahlatji, ML

2013-10-01

Full Text Available Mechanical alloying of an equiatomic mixture of crystalline elemental powders of Ti and Pt in a high-energy ball mill results in formation of an amorphous alloy by solid-state reactions. Mechanical alloying was carried out in an argon atmosphere...

Gas-solid hydroxyethylation of potato starch in a stirred vibrating fluidized bed reactor

NARCIS (Netherlands)

Kuipers, N.J M; Stamhuis, Eize; Beenackers, A.A C M

A novel reactor for modifying cohesive C-powders such as in the gas-solid hydroxyethylation of semidry potato starch is characterized, the so-called stirred vibrating fluidized bed reactor. Good fluidization characteristics are obtained in this reactor for certain combinations of stirring and

Avalanches near a solid insulator in nitrogen gas at atmospheric pressure

International Nuclear Information System (INIS)

Mahajan, S.M.; Sudarshan, T.S.; Department of Electrical and Computer Engineering, University of South Carolina, Columbia, South Carolina 29208)

1989-01-01

The pulsed Townsend (PT) technique was used to record the growth of avalanches near a solid insulator in nitrogen gas at 0.1 MPa. Several other nonconventional techniques for releasing initiatory electrons at the cathode are discussed. In this paper, experimental results of avalanches initiated by illuminating a fast (0.6-ns) nitrogen laser onto the cathode triple junction are presented. Data were recorded with plexiglas, Teflon, high-density polyethylene, low-density polyethylene, Delrin, etc. Effect of surface condition, variation of the distance between insulator surface and the avalanche initiation region, and the effect of a large number of previous avalanches on the avalanche characteristics at a particular voltage were studied. The Townsend primary ionization coefficient, hereafter referred to as growth coefficient (α), and drift velocity (V/sub e/) were evaluated through the PT technique. Results indicate that the avalanche growth in the vicinity of a solid insulator is less than that in an identical plain gas gap. Existence of a nonuniform field as a result of surface charges on the insulator and/or field modifications due to the avalanche space charge are believed to be responsible for this behavior

Label-free and sensitive detection of T4 polynucleotide kinase activity via coupling DNA strand displacement reaction with enzymatic-aided amplification.

Science.gov (United States)

Cheng, Rui; Tao, Mangjuan; Shi, Zhilu; Zhang, Xiafei; Jin, Yan; Li, Baoxin

2015-11-15

Several fluorescence signal amplification strategies have been developed for sensitive detection of T4 polynucleotide kinase (T4 PNK) activity, but they need fluorescence dye labeled DNA probe. We have addressed the limitation and report here a label-free strategy for sensitive detection of PNK activity by coupling DNA strand displacement reaction with enzymatic-aided amplification. A hairpin oligonucleotide (hpDNA) with blunt ends was used as the substrate for T4 PNK phosphorylation. In the presence of T4 PNK, the stem of hpDNA was phosphorylated and further degraded by lambda exonuclease (λ exo) from 5' to 3' direction to release a single-stranded DNA as a trigger of DNA strand displacement reaction (SDR). The trigger DNA can continuously displace DNA P2 from P1/P2 hybrid with the help of specific cleavage of nicking endonuclease (Nt.BbvCI). Then, DNA P2 can form G-quadruplex in the presence of potassium ions and quadruplex-selective fluorphore, N-methyl mesoporphyrin IX (NMM), resulting in a significant increase in fluorescence intensity of NMM. Thus, the accumulative release of DNA P2 led to fluorescence signal amplification for determining T4 PNK activity with a detection limit of 6.6×10(-4) U/mL, which is superior or comparative with established approaches. By ingeniously utilizing T4 PNK-triggered DNA SDR, T4 PNK activity can be specifically and facilely studied in homogeneous solution containing complex matrix without any external fluorescence labeling. Moreover, the influence of different inhibitors on the T4 PNK activity revealed that it also can be explored to screen T4 PNK inhibitors. Therefore, this label-free amplification strategy presents a facile and cost-effective approach for nucleic acid phosphorylation related research. Copyright © 2015 Elsevier B.V. All rights reserved.

Application of lattice-gas cellular automata to the Brownian motion of solids in suspension

International Nuclear Information System (INIS)

Ladd, A.J.C.; Colvin, M.E.; Frenkel, D.

1988-01-01

An adaptation of lattice-gas cellular automata to the simulation of solid-fluid suspensions is described. The method incorporates both dissipative hydrodynamic forces and thermal fluctuations. At low solid densities, theoretical results for the drag force on a single disk and the viscosity of a suspension of disks are reproduced. The zero--shear-rate viscosity has been obtained over a range of packing fractions and results indicate that simulations of three-dimensional suspensions are feasible

Liquid and Gas Phase Chemistry of Hypergolic Reactions between MMH and NTO or RFNA

Science.gov (United States)

Black, Ariel

Hypergolic systems rely on fuel and oxidizer propellant combinations that spontaneously ignite upon contact. Monomethylhydrazine (MMH) fuel and nitrogen tetroxide (NTO) - based oxidizers embody the state of the art for hypergolic propellants, although the health and safety hazards associated with these propellants demand investigation into less-toxic, high performance alternatives. In order to replicate the combustion characteristics of these highly reactive propellants, a detailed understanding of the full reaction process is necessary. Current reaction mechanisms and hypergolic ignition models generally assume that gas-phase chemistry dominates the interaction since the liquid-phase reactions occur on the order of microseconds. However, condensed-phase reactions produce intermediates integral to gas-phase initiation and development. Additional insight into the physical and chemical processes that dictate this liquid-phase chemistry is therefore essential. Concurrently, further examination of the gas-phase reactions leading to and immediately following ignition is also needed. A method devoted to the determination of the liquid phase hypergolic reaction mechanism and kinematic rate parameters for MMH-NTO and MMH-red fuming nitric acid (RFNA) is presented in this study. MMH-RFNA reaction chemistry is better understood and documented in literature than MMH-NTO and is examined for comparison and validation. Drop on pool experiments at a range of temperatures were initially undertaken using MMH and RFNA and then modified to accommodate the high vapor pressure of NTO. Using a temperature and atmosphere controlled droplet contact chamber, the liquid phases of MMH-RFNA and MMH-NTO were studied by capturing impacts at frame rates from 100,000 to 500,000 fps. This footage allowed for the identification of time delays between droplet contact and initial gas formation, enabling calibration of the Arrhenius pre-exponential factors and activation energies for a global, one

Approximate deconvolution model for the simulation of turbulent gas-solid flows: An a priori analysis

Science.gov (United States)

Schneiderbauer, Simon; Saeedipour, Mahdi

2018-02-01

Highly resolved two-fluid model (TFM) simulations of gas-solid flows in vertical periodic channels have been performed to study closures for the filtered drag force and the Reynolds-stress-like contribution stemming from the convective terms. An approximate deconvolution model (ADM) for the large-eddy simulation of turbulent gas-solid suspensions is detailed and subsequently used to reconstruct those unresolved contributions in an a priori manner. With such an approach, an approximation of the unfiltered solution is obtained by repeated filtering allowing the determination of the unclosed terms of the filtered equations directly. A priori filtering shows that predictions of the ADM model yield fairly good agreement with the fine grid TFM simulations for various filter sizes and different particle sizes. In particular, strong positive correlation (ρ > 0.98) is observed at intermediate filter sizes for all sub-grid terms. Additionally, our study reveals that the ADM results moderately depend on the choice of the filters, such as box and Gaussian filter, as well as the deconvolution order. The a priori test finally reveals that ADM is superior compared to isotropic functional closures proposed recently [S. Schneiderbauer, "A spatially-averaged two-fluid model for dense large-scale gas-solid flows," AIChE J. 63, 3544-3562 (2017)].

Effects of Fault Displacement on Emplacement Drifts

International Nuclear Information System (INIS)

Duan, F.

2000-01-01

The purpose of this analysis is to evaluate potential effects of fault displacement on emplacement drifts, including drip shields and waste packages emplaced in emplacement drifts. The output from this analysis not only provides data for the evaluation of long-term drift stability but also supports the Engineered Barrier System (EBS) process model report (PMR) and Disruptive Events Report currently under development. The primary scope of this analysis includes (1) examining fault displacement effects in terms of induced stresses and displacements in the rock mass surrounding an emplacement drift and (2 ) predicting fault displacement effects on the drip shield and waste package. The magnitude of the fault displacement analyzed in this analysis bounds the mean fault displacement corresponding to an annual frequency of exceedance of 10 -5 adopted for the preclosure period of the repository and also supports the postclosure performance assessment. This analysis is performed following the development plan prepared for analyzing effects of fault displacement on emplacement drifts (CRWMS M and O 2000). The analysis will begin with the identification and preparation of requirements, criteria, and inputs. A literature survey on accommodating fault displacements encountered in underground structures such as buried oil and gas pipelines will be conducted. For a given fault displacement, the least favorable scenario in term of the spatial relation of a fault to an emplacement drift is chosen, and the analysis is then performed analytically. Based on the analysis results, conclusions are made regarding the effects and consequences of fault displacement on emplacement drifts. Specifically, the analysis will discuss loads which can be induced by fault displacement on emplacement drifts, drip shield and/or waste packages during the time period of postclosure

Measurement on liquid film in microchannels using laser focus displacements meter

International Nuclear Information System (INIS)

Fukamachi, Norihiro; Tamura, Naohisa; Hazuku, Tatsuya; Takamasa, Tomoji

2003-01-01

To elucidate details of the fascinating nonlinear phenomena of gas-liquid interface in micro- and mini-channels, high spatial temporal knowledge of the interface in gas-liquid two-phase flows is essential. This paper presents a new method for measuring interface of liquid film in microchannels using a laser focus displacement meter(LFD). The purpose of the study was to clarify the effectiveness the new method for obtaining detailed information of interface displacement, especially in the case of thin liquid film, in micro- and mini-channels. In the test, water and nitrogen gas were used as working fluids. To eliminate the signal of tube wall disturbing that of gas-liquid interface, a fluorocarbon tube with water box was used; whose refraction index was the same as one of water. With this method, accurate measurements of the interface of liquid film, in real time, with sensitivity of 0.1 μm and 1 kHz, were achieved. The error caused by the refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated theoretically and experimentally. The formulated theoretical equation can derive the real interface displacement using measured displacement in a fluorocarbon tube of 25 μm -2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 and 2 mm in I.D. showed that the corrected interface displacement calculated by the equation agreed with real displacement within a 1% margin of error. Simultaneous measurement on the interface in a fluorocarbon tube of 0.5 and 1 mm in I.D. using the LFD and a high-speed camera movie with a microscope was carried out. It showed that the LFD could measure the interface of liquid film in high spatially and temporally in annular, slug and piston flow regions and clarified the existence of thin liquid film thinner than 1 μm in thickness in slug and annular regions. (author)

Effect of sweep gas chemistry on vaporization of Li4SiO4

International Nuclear Information System (INIS)

Yamawaki, M.; Yamaguchi, K.

1995-01-01

Gas/solid equilibria in the system Li 4 SiO 4 -D 2 -D 2 O were studied by means of Knudsen effusion mass spectrometry. A Knudsen effusion mass spectrometer was modified to enable studies of reactions of hydrogen and/or water vapor with ceramic breeder materials. A gas inlet system was constructed to allow the introduction of gases into a platinum Knudsen cell, from which the equilibrated gaseous reaction products effuse. From the experimental results, it has been deduced that the equilibrium constants of vaporization reactions differ correspondingly to the nonstoichiometry of lithium orthosilicate. ((orig.))

Passive Smoking in a Displacement Ventilated Room

DEFF Research Database (Denmark)

Bjørn, Erik; Nielsen, Peter V.

The aim of this research is to see if the displacement ventilation principle can protect a person from exposure to passive tobacco smoking. This is done by full-scale experiments with two breathing thermal manikins, smoke visualisations, and tracer gas measurements. In some situations, exhaled...... smoke will stratify in a certain height due to the vertical temperature gradient. This horizontal layer of exhaled tobacco smoke may lead to exposure. In other situations, the smoke is mixed into the upper zone, and the passive smoker is protected to some extent by the displacement principle...

Selection and application of strand displacement probes for a fumonisin B1 aptamer

Science.gov (United States)

Fumonisin B1 (FB1) is a toxin produced by Fusarium moniliforme, mainly on contaminated maize and maize products. In this study a solid surface chain displacement strategy was used to isolate oligonucleotide displacement probes for a FB1 aptamer. The probes were used as the basis for the development ...

Flow Mapping in a Gas-Solid Riser via Computer Automated Radioactive Particle Tracking (CARPT)

Energy Technology Data Exchange (ETDEWEB)

Muthanna Al-Dahhan; Milorad P. Dudukovic; Satish Bhusarapu; Timothy J. O' hern; Steven Trujillo; Michael R. Prairie

2005-06-04

Statement of the Problem: Developing and disseminating a general and experimentally validated model for turbulent multiphase fluid dynamics suitable for engineering design purposes in industrial scale applications of riser reactors and pneumatic conveying, require collecting reliable data on solids trajectories, velocities ? averaged and instantaneous, solids holdup distribution and solids fluxes in the riser as a function of operating conditions. Such data are currently not available on the same system. Multiphase Fluid Dynamics Research Consortium (MFDRC) was established to address these issues on a chosen example of circulating fluidized bed (CFB) reactor, which is widely used in petroleum and chemical industry including coal combustion. This project addresses the problem of lacking reliable data to advance CFB technology. Project Objectives: The objective of this project is to advance the understanding of the solids flow pattern and mixing in a well-developed flow region of a gas-solid riser, operated at different gas flow rates and solids loading using the state-of-the-art non-intrusive measurements. This work creates an insight and reliable database for local solids fluid-dynamic quantities in a pilot-plant scale CFB, which can then be used to validate/develop phenomenological models for the riser. This study also attempts to provide benchmark data for validation of Computational Fluid Dynamic (CFD) codes and their current closures. Technical Approach: Non-Invasive Computer Automated Radioactive Particle Tracking (CARPT) technique provides complete Eulerian solids flow field (time average velocity map and various turbulence parameters such as the Reynolds stresses, turbulent kinetic energy, and eddy diffusivities). It also gives directly the Lagrangian information of solids flow and yields the true solids residence time distribution (RTD). Another radiation based technique, Computed Tomography (CT) yields detailed time averaged local holdup profiles at

Calculations of atomic sputtering and displacement cross-sections in solid elements by electrons with energies from threshold to 1.5 MV

International Nuclear Information System (INIS)

Bradley, C.R.

1988-12-01

The kinetics of knock-on collisions of relativistic electrons with nuclei and details of the numerical evaluation of differential, recoil, and total Mott cross-sections are reviewed and discussed. The effects of electron beam induced displacement and sputtering, in the transmission electron microscope (TEM) environment, on microanalysis are analyzed with particular emphasis placed on the removal of material by knock-on sputtering. The mass loss predicted due to transmission knock-on sputtering is significant for many elements under conditions frequently encountered in microanalysis. Total Mott cross-sections are tabulated for all naturally occurring solid elements up to Z = 92 at displacement energies of one, two, four, and five times the sublimation energy and for accelerating voltages accessible in the transmission electron microscope. Fortran source code listings for the calculation of the differential Mott cross-section as a function of electron scattering angle (dMottCS), as a function of nuclear recoil angle (RECOIL), and the total Mott cross-section (TOTCS) are included. 48 refs., 21 figs., 12 tabs

Laser-induced carbon plasma emission spectroscopic measurements on solid targets and in gas-phase optical breakdown

International Nuclear Information System (INIS)

Nemes, Laszlo; Keszler, Anna M.; Hornkohl, James O.; Parigger, Christian

2005-01-01

We report measurements of time- and spatially averaged spontaneous-emission spectra following laser-induced breakdown on a solid graphite/ambient gas interface and on solid graphite in vacuum, and also emission spectra from gas-phase optical breakdown in allene C3H4 and helium, and in CO2 and helium mixtures. These emission spectra were dominated by CII (singly ionized carbon), CIII (doubly ionized carbon), hydrogen Balmer beta (H b eta), and Swan C2 band features. Using the local thermodynamic equilibrium and thin plasma assumptions, we derived electron number density and electron temperature estimates. The former was in the 1016 cm -3 range, while the latter was found to be near 20000 K. In addition, the vibration-rotation temperature of the Swan bands of the C2 radical was determined to be between 4500 and 7000 K, using an exact theoretical model for simulating diatomic emission spectra. This temperature range is probably caused by the spatial inhomogeneity of the laser-induced plasma plume. Differences are pointed out in the role of ambient CO2 in a solid graphite target and in gas-phase breakdown plasma

An Equilibrium-Based Model of Gas Reaction and Detonation

International Nuclear Information System (INIS)

Trowbridge, L.D.

2000-01-01

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

A cascade autocatalytic strand displacement amplification and hybridization chain reaction event for label-free and ultrasensitive electrochemical nucleic acid biosensing.

Science.gov (United States)

Chen, Zhiqiang; Liu, Ying; Xin, Chen; Zhao, Jikuan; Liu, Shufeng

2018-04-23

Herein, an autocatalytic strand displacement amplification (ASDA) strategy was proposed for the first time, which was further ingeniously coupled with hybridization chain reaction (HCR) event for the isothermal, label-free and multiple amplification toward nucleic acid detection. During the ASDA module, the target recognition opens the immobilized hairpin probe (IP) and initiates the annealing of the auxiliary DNA strand (AS) with the opened IP for the successive polymerization and nicking reaction in the presence of DNA polymerase and nicking endonuclease. This induces the target recycling and generation of a large amount of intermediate DNA sequences, which can be used as target analogy to execute the autocatalytic strand displacement amplification. Simultaneously, the introduced AS strand can propagate the HCR between two hairpins (H1 and H2) to form a linear DNA concatamer with cytosine (C)-rich loop region, which can facilitate the in-situ synthesis of silver nanoclusters (AgNCs) as electrochemical tags for further amplification toward target responses. With current cascade ASDA and HCR strategy, the detection of target DNA could be achieved with a low detection limit of about 0.16 fM and a good selectivity. The developed biosensor also exhibits the distinct advantages of flexibility and simplicity in probe design and biosensor fabrication, and label-free electrochemical detection, thus opens a promising avenue for the detection of nucleic acid with low abundance in bioanalysis and clinical biomedicine. Copyright © 2018 Elsevier B.V. All rights reserved.

Detection of DNA damage based on metal-mediated molecular beacon and DNA strands displacement reaction

Science.gov (United States)

Xiong, Yanxiang; Wei, Min; Wei, Wei; Yin, Lihong; Pu, Yuepu; Liu, Songqin

2014-01-01

DNA hairpin structure probes are usually designed by forming intra-molecular duplex based on Watson-Crick hydrogen bonds. In this paper, a molecular beacon based on silver ions-mediated cytosine-Ag+-cytosine base pairs was used to detect DNA. The inherent characteristic of the metal ligation facilitated the design of functional probe and the adjustment of its binding strength compared to traditional DNA hairpin structure probes, which make it be used to detect DNA in a simple, rapid and easy way with the help of DNA strands displacement reaction. The method was sensitive and also possesses the good specificity to differentiate the single base mismatched DNA from the complementary DNA. It was also successfully applied to study the damage effect of classic genotoxicity chemicals such as styrene oxide and sodium arsenite on DNA, which was significant in food science, environmental science and pharmaceutical science.

Tuneable diode laser gas analyser for methane measurements on a large scale solid oxide fuel cell

Science.gov (United States)

Lengden, Michael; Cunningham, Robert; Johnstone, Walter

2011-10-01

A new in-line, real time gas analyser is described that uses tuneable diode laser spectroscopy (TDLS) for the measurement of methane in solid oxide fuel cells. The sensor has been tested on an operating solid oxide fuel cell (SOFC) in order to prove the fast response and accuracy of the technology as compared to a gas chromatograph. The advantages of using a TDLS system for process control in a large-scale, distributed power SOFC unit are described. In future work, the addition of new laser sources and wavelength modulation will allow the simultaneous measurement of methane, water vapour, carbon-dioxide and carbon-monoxide concentrations.

Effect of temperature on a free energy and equilibrium constants during dry flue gas desulphurisation chemical reactions

Directory of Open Access Journals (Sweden)

Kuburović Miloš

2002-01-01

Full Text Available During dry flue gas desulphurisation (FGD dry particles of reagents are inserted (injected in the stream of flue gas, where they bond SO2. As reagents, the most often are used compounds of calcium (CaCO3, CaO or Ca(OH2. Knowledge of free energy and equilibrium constants of chemical reactions during dry FGD is necessary for understanding of influence of flue gas temperature to course of these chemical reactions as well as to SO2 bonding from flue gases.

Greenhouse gas emission mitigation relevant to changes in municipal solid waste management system.

Science.gov (United States)

Pikoń, Krzysztof; Gaska, Krzysztof

2010-07-01

Standard methods for assessing the environmental impact of waste management systems are needed to underpin the development and implementation of sustainable waste management practice. Life cycle assessment (LCA) is a tool for comprehensively ensuring such assessment and covers all impacts associated with waste management. LCA is often called "from cradle to grave" analysis. This paper integrates information on the greenhouse gas (GHG) implications of various management options for some of the most common materials in municipal solid waste (MSW). Different waste treatment options for MSW were studied in a system analysis. Different combinations of recycling (cardboard, plastics, glass, metals), biological treatment (composting), and incineration as well as land-filling were studied. The index of environmental burden in the global warming impact category was calculated. The calculations are based on LCA methodology. All emissions taking place in the whole life cycle system were taken into account. The analysis included "own emissions," or emissions from the system at all stages of the life cycle, and "linked emissions," or emissions from other sources linked with the system in an indirect way. Avoided emissions caused by recycling and energy recovery were included in the analysis. Displaced emissions of GHGs originate from the substitution of energy or materials derived from waste for alternative sources. The complex analysis of the environmental impact of municipal waste management systems before and after application of changes in MSW systems according to European Union regulations is presented in this paper. The evaluation is made for MSW systems in Poland.

Thermodynamic Performance Study of Biomass Gasification, Solid Oxide Fuel Cell and Micro Gas Turbine Hybrid Systems

DEFF Research Database (Denmark)

Bang-Møller, Christian; Rokni, Masoud

2010-01-01

A system level modelling study of three combined heat and power systems based on biomass gasification is presented. Product gas is converted in a micro gas turbine (MGT) in the first system, in a solid oxide fuel cell (SOFC) in the second system and in a combined SOFC–MGT arrangement in the third...

Exchange between the stagnant and flowing zone in gas-flowing solids-fixed bed contactors

Directory of Open Access Journals (Sweden)

ALEKSANDAR P. DUDUKOVIC

2005-02-01

Full Text Available In countercurrent gas – flowing solids – fixed bed contactors, a fraction of the flowing solids is in motion (dynamic holdup, while the other fraction is resting on the fixed bed elements. In this study it was experimentally proved that the stagnant zone should not be considered as a dead part of the column, but that there is a dynamic exchange between these two portions of flowing solids particles. Combining a mathematical model with tracer experiments, the rate of exchange was determined and it was shown that only a small part (ca. 20 % of the stagnant region should be considered as a dead one.

One-step simultaneous differential scanning calorimetry-FTIR microspectroscopy to quickly detect continuous pathways in the solid-state glucose/asparagine Maillard reaction.

Science.gov (United States)

Hwang, Deng-Fwu; Hsieh, Tzu-Feng; Lin, Shan-Yang

2013-01-01

The stepwise reaction pathway of the solid-state Maillard reaction between glucose (Glc) and asparagine (Asn) was investigated using simultaneous differential scanning calorimetry (DSC)-FTIR microspectroscopy. The color change and FTIR spectra of Glc-Asn physical mixtures (molar ratio = 1:1) preheated to different temperatures followed by cooling were also examined. The successive reaction products such as Schiff base intermediate, Amadori product, and decarboxylated Amadori product in the solid-state Glc-Asn Maillard reaction were first simultaneously evidenced by this unique DSC-FTIR microspectroscopy. The color changed from white to yellow-brown to dark brown, and appearance of new IR peaks confirmed the formation of Maillard reaction products. The present study clearly indicates that this unique DSC-FTIR technique not only accelerates but also detects precursors and products of the Maillard reaction in real time.

Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions

International Nuclear Information System (INIS)

Frankovsky, Rainer

2013-01-01

The results of this thesis can be divided into three major topics, which can also be seen as different approaches of solid state chemistry to reveal interesting features of known and unknown compounds and to develop alternative synthesis routes. Firstly, known compounds with related structural motifs to the superconducting iron-arsenides were investigated regarding their structural and physical properties. In case of La 3 Pd 4 Ge 4 the influence of Fe doping on the properties was studied, whereas in the series ZrMAs (M=Ti,V) the physical properties have not yet been reported at all and were investigated for the first time. Secondly, an alternative synthesis route has been developed for the synthesis of superconducting LaFeAsO 1-x F x . This solid state metathesis reaction distinctly increased the quality of the samples compared to conventionally prepared products. Furthermore, the reaction pathway was investigated and clarified, which helps to understand the processes during high temperature solid state metathesis reactions in general. Thirdly, this alternative synthesis route was expanded to other systems and new compounds like co-substituted LaFe 1-x Mn x AsO 1-y F y were prepared and thoroughly investigated. This led to a complex study of the interplay of magnetism, electronic and structural conditions and the occurrence of superconducting properties. The investigation and understanding of such complex coherences will probably be decisive for the further understanding of the superconducting mechanism in iron based superconductors.

Gas phase polymerization of propylene. Reaction kinetics and molecular weight distribution

NARCIS (Netherlands)

Meier, G.B.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria

2001-01-01

Gas-phase polymerizations have been executed at different temperatures, pressures, and hydrogen concentrations using Me2Si[Ind]2ZrCl2 / methylaluminoxane / SiO2(Pennsylvania Quarts) as a catalyst. The reaction rate curves have been described by a kinetic model, which takes into account the initially

Theoretical and experimental study on solid chemical reaction between BaCO3 and TiO2 in microwave field

International Nuclear Information System (INIS)

Liu Hanxing; Guo, Liling; Zou Long; Cao Minhe; Zhou Jian; Ouyang Shixi

2004-01-01

Solid-state chemical reaction mechanism for the reaction between BaCO 3 and TiO 2 in microwave field was investigated based on X-ray power diffraction (XRD) data and theory of diffusion. The compositions of the resultant after reaction under different conditions were studied by employing XRD. The quantitative analyses based on XRD data showed the reaction in microwave field was quite different from that in the conventional method. A model was proposed to explain the change of the ratio between the reactant BaCO 3 , TiO 2 and the resultant BaTiO 3 for the chemical reaction. The formation kinetic of BaTiO 3 from the BaCO 3 and TiO 2 was calculated by employing this theoretical model. The reaction rate between BaCO 3 and TiO 2 in microwave field was much higher than that in conventional method. The activation energy of the atomic diffusions in this solid chemical reaction is only 58 kJ/mol, which was only about 1/4 of 232 kJ/mol in the conventional value. The result suggests that the microwave field enhance atomic diffusion during the reaction

Humidity independent mass spectrometry for gas phase chemical analysis via ambient proton transfer reaction.

Science.gov (United States)

Zhu, Hongying; Huang, Guangming

2015-03-31

In this work, a humidity independent mass spectrometric method was developed for rapid analysis of gas phase chemicals. This method is based upon ambient proton transfer reaction between gas phase chemicals and charged water droplets, in a reaction chamber with nearly saturate humidity under atmospheric pressure. The humidity independent nature enables direct and rapid analysis of raw gas phase samples, avoiding time- and sample-consuming sample pretreatments in conventional mass spectrometry methods to control sample humidity. Acetone, benzene, toluene, ethylbenzene and meta-xylene were used to evaluate the analytical performance of present method. The limits of detection for benzene, toluene, ethylbenzene and meta-xylene are in the range of ∼0.1 to ∼0.3 ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5 μg m(-3), ∼1.44 ppbV), with linear ranges of approximately two orders of magnitude. The majority of the homemade device contains a stainless steel tube as reaction chamber and an ultrasonic humidifier as the source of charged water droplets, which makes this cheap device easy to assemble and facile to operate. In addition, potential application of this method was illustrated by the real time identification of raw gas phase chemicals released from plants at different physiological stages. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of Bubble-Bubble interactions on the macroscale circulation patterns in a bubbling gas-solid fluidized bed

NARCIS (Netherlands)

Laverman, J.A.; van Sint Annaland, M.; Kuipers, J.A.M.

2007-01-01

The macro-scale circulation patterns in the emulsion phase of a gas-solid fluidized bed in the bubbling regime have been studied with a 3D Discrete Bubble Model. It has been shown that bubble-bubble interactions strongly influence the extent of the solids circulation and the bubble size

Gas-Phase Functionalization of Macroscopic Carbon Nanotube Fiber Assemblies: Reaction Control, Electrochemical Properties, and Use for Flexible Supercapacitors.

Science.gov (United States)

Iglesias, Daniel; Senokos, Evgeny; Alemán, Belén; Cabana, Laura; Navío, Cristina; Marcilla, Rebeca; Prato, Maurizio; Vilatela, Juan J; Marchesan, Silvia

2018-02-14

The assembly of aligned carbon nanotubes (CNTs) into fibers (CNTFs) is a convenient approach to exploit and apply the unique physico-chemical properties of CNTs in many fields. CNT functionalization has been extensively used for its implementation into composites and devices. However, CNTF functionalization is still in its infancy because of the challenges associated with preservation of CNTF morphology. Here, we report a thorough study of the gas-phase functionalization of CNTF assemblies using ozone which was generated in situ from a UV source. In contrast with liquid-based oxidation methods, this gas-phase approach preserves CNTF morphology, while notably increasing its hydrophilicity. The functionalized material is thoroughly characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. Its newly acquired hydrophilicity enables CNTF electrochemical characterization in aqueous media, which was not possible for the pristine material. Through comparison of electrochemical measurements in aqueous electrolytes and ionic liquids, we decouple the effects of functionalization on pseudocapacitive reactions and quantum capacitance. The functionalized CNTF assembly is successfully used as an active material and a current collector in all-solid supercapacitor flexible devices with an ionic liquid-based polymer electrolyte.

Mitigating CO2 Leakage by Immobilizing CO2 into Solid Reaction Products: 13th International Conference on Greenhouse Gas Control Technologies, GHGT 2016. 14 November 2016 through 18 November 2016

NARCIS (Netherlands)

Wasch, L.J.; Wollenweber, J.; Neele, F.; Fleury, M.

2017-01-01

In the unlikely case of CO2 leakage from a storage reservoir, it is desirable to close the leak efficiently and permanently. This could be done by injecting a reactive solution into the leak path, thereby immobilizing migrating CO2 by consuming the gas and forming solid reactants. With regard to

ICR studies of some anionic gas phase reactions and FTICR software design

International Nuclear Information System (INIS)

Noest, A.J.

1983-01-01

This thesis consists of two parts. Part one (Chs. 1-5) reports experimental results from mostly drift-cell ICR studies of negative ion-molecule reactions; part two (Chs. 6-11) concerns the design of software for an FTICR instrument. The author discusses successively: 1. ion cyclotron resonance spectrometry; 2. the gas phase allyl anion; 3. the (M-H) and (M-H2) anions from acetone; 4. negative ion-molecule reactions of aliphatic nitrites studied by cyclotron resonance; 5. homoconjugation versus charge-dipole interaction effects in the stabilization of carbanions in the gas phase; 6. the Fourier Transform ICR method; 7. the FTICR-software; 8. an efficient adaptive matcher filter for fast transient signals; 9. reduction of spectral peak height errors by time-domain weighing; 10. Chirp excitation; 11. Compact data storage. The book concludes with a Dutch and English summary (G.J.P.)

Specifications for surface reaction analysis apparatus

International Nuclear Information System (INIS)

Teraoka, Yuden; Yoshigoe, Akitaka

2001-03-01

A surface reaction analysis apparatus was installed at the JAERI soft x-ray beamline in the SPring-8 as an experimental end-station for the study of surface chemistry. The apparatus is devoted to the study concerning the influence of translational kinetic energy of incident molecules to chemical reactions on solid surfaces with gas molecules. In order to achieve the research purpose, reactive molecular scattering experiments and photoemission spectroscopic measurements using synchrotron radiation are performed in that apparatus via a supersonic molecular beam generator, an electron energy analyzer and a quadrupole mass analyzer. The detail specifications for the apparatus are described in this report. (author)

Sub-ensemble monitoring of DNA strand displacement using multiparameter single-molecule FRET

OpenAIRE

Baltierra Jasso, Laura; Morten, Michael; Magennis, Steven William

2018-01-01

Non-enzymatic DNA strand displacement is an important mechanism in dynamic DNA nanotechnology. Here we show that the large parameter space that is accessible by single-molecule FRET is ideal for the simultaneous monitoring of multiple reactants and products of DNA strand exchange reactions. We monitored the strand displacement from double-stranded DNA (dsDNA) by single-stranded DNA (ssDNA) at 37 °C; the data were modelled as a second-order reaction approaching equilibrium, with a rate constan...

Multiple Multidentate Halogen Bonding in Solution, in the Solid State, and in the (Calculated) Gas Phase.

Science.gov (United States)

Jungbauer, Stefan H; Schindler, Severin; Herdtweck, Eberhardt; Keller, Sandro; Huber, Stefan M

2015-09-21

The binding properties of neutral halogen-bond donors (XB donors) bearing two multidentate Lewis acidic motifs toward halides were investigated. Employing polyfluorinated and polyiodinated terphenyl and quaterphenyl derivatives as anion receptors, we obtained X-ray crystallographic data of the adducts of three structurally related XB donors with tetraalkylammonium chloride, bromide, and iodide. The stability of these XB complexes in solution was determined by isothermal titration calorimetry (ITC), and the results were compared to X-ray analyses as well as to calculated binding patterns in the gas phase. Density functional theory (DFT) calculations on the gas-phase complexes indicated that the experimentally observed distortion of the XB donors during multiple multidentate binding can be reproduced in 1:1 complexes with halides, whereas adducts with two halides show a symmetric binding pattern in the gas phase that is markedly different from the solid state structures. Overall, this study demonstrates the limitations in the transferability of binding data between solid state, solution, and gas phase in the study of complex multidentate XB donors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aromatic C-Nitroso Compounds and Their Dimers: A Model for Probing the Reaction Mechanisms in Crystalline Molecular Solids

Directory of Open Access Journals (Sweden)

Ivana Biljan

2017-12-01

Full Text Available This review is focused on the dimerization and dissociation of aromatic C-nitroso compounds and their dimers, the reactions that could be used as a convenient model for studying the thermal organic solid-state reaction mechanisms. This molecular model is simple because it includes formation or breaking of only one covalent bond between two nitrogen atoms. The crystalline molecular solids of nitroso dimers (azodioxides dissociate by photolysis under the cryogenic conditions, and re-dimerize by slow warming. The thermal re-dimerization reaction is examined under the different topotactic conditions in crystals: disordering, surface defects, and phase transformations. Depending on the conditions, and on the molecular structure, aromatic C-nitroso compounds can associate to form one-dimensional polymeric structures and are able to self-assemble on gold surfaces.

Formation of the prebiotic molecule NH2CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations.

Science.gov (United States)

Song, Lei; Kästner, Johannes

2016-10-26

Investigating how formamide forms in the interstellar medium is a hot topic in astrochemistry, which can contribute to our understanding of the origin of life on Earth. We have constructed a QM/MM model to simulate the hydrogenation of isocyanic acid on amorphous solid water surfaces to form formamide. The binding energy of HNCO on the ASW surface varies significantly between different binding sites, we found values between ∼0 and 100 kJ mol -1 . The barrier for the hydrogenation reaction is almost independent of the binding energy, though. We calculated tunneling rate constants of H + HNCO → NH 2 CO at temperatures down to 103 K combining QM/MM with instanton theory. Tunneling dominates the reaction at such low temperatures. The tunneling reaction is hardly accelerated by the amorphous solid water surface compared to the gas phase for this system, even though the activation energy of the surface reaction is lower than the one of the gas-phase reaction. Both the height and width of the barrier affect the tunneling rate in practice. Strong kinetic isotope effects were observed by comparing to rate constants of D + HNCO → NHDCO. At 103 K we found a KIE of 231 on the surface and 146 in the gas phase. Furthermore, we investigated the gas-phase reaction NH 2 + H 2 CO → NH 2 CHO + H and found it unlikely to occur at cryogenic temperatures. The data of our tunneling rate constants are expected to significantly influence astrochemical models.

Reaction pathways for catalytic gas-phase oxidation of glycerol over mixed metal oxides

Energy Technology Data Exchange (ETDEWEB)

Suprun, W.; Glaeser, R.; Papp, H. [Leipzig Univ. (Germany). Inst. of Chemical Technology

2011-07-01

Glycerol as a main by-product from bio-diesel manufacture is a cheap raw material with large potential for chemical or biochemical transformations to value-added C3-chemicals. One possible way of glycerol utilization involves its catalytic oxidation to acrylic acid as an alternative to petrochemical routes. However, this catalytic conversion exhibits various problems such as harsh reaction conditions, severe catalyst coking and large amounts of undesired by-products. In this study, the reaction pathways for gas-phase conversion of glycerol over transition metal oxides (Mo, V und W) supported on TiO{sub 2} and SiO{sub 2} were investigated by two methods: (i) steady state experiments of glycerol oxidation and possible reactions intermediates, i.e., acrolein, 3-hydroxy propionaldehyde and acetaldehyde, and (ii) temperature-programmed surface reaction (TPSR) studies of glycerol conversion in the presence and in the absence of gas-phase oxygen. It is shown that the supported W-, V and Mo-oxides possess an ability to catalyze the oxidation of glycerol to acrylic acid. These investigations allowed us to gain a deeper insight into the reaction mechanism. Thus, based on the obtained results, three possible reactions pathways for the selective oxidation of glycerol to acrylic acid on the transition metal-containing catalysts are proposed. The major pathways in presence of molecular oxygen are a fast successive destructive oxidation of glycerol to CO{sub x} and the dehydration of glycerol to acrolein which is a rate-limiting step. (orig.)

Photochemical Acceleration of DNA Strand Displacement by Using Ultrafast DNA Photo-crosslinking.

Science.gov (United States)

Nakamura, Shigetaka; Hashimoto, Hirokazu; Kobayashi, Satoshi; Fujimoto, Kenzo

2017-10-18

DNA strand displacement is an essential reaction in genetic recombination, biological processes, and DNA nanotechnology. In particular, various DNA nanodevices enable complicated calculations. However, it takes time before the output is obtained, so acceleration of DNA strand displacement is required for a rapid-response DNA nanodevice. Herein, DNA strand displacement by using DNA photo-crosslinking to accelerate this displacement is evaluated. The DNA photo-crosslinking of 3-cyanovinylcarbazole ( CNV K) was accelerated at least 20 times, showing a faster DNA strand displacement. The rate of photo-crosslinking is a key factor and the rate of DNA strand displacement is accelerated through ultrafast photo-crosslinking. The rate of DNA strand displacement was regulated by photoirradiation energy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A highly sensitive hydrogen sensor with gas selectivity using a PMMA membrane-coated Pd nanoparticle/single-layer graphene hybrid.

Science.gov (United States)

Hong, Juree; Lee, Sanggeun; Seo, Jungmok; Pyo, Soonjae; Kim, Jongbaeg; Lee, Taeyoon

2015-02-18

A polymer membrane-coated palladium (Pd) nanoparticle (NP)/single-layer graphene (SLG) hybrid sensor was fabricated for highly sensitive hydrogen gas (H2) sensing with gas selectivity. Pd NPs were deposited on SLG via the galvanic displacement reaction between graphene-buffered copper (Cu) and Pd ion. During the galvanic displacement reaction, graphene was used as a buffer layer, which transports electrons from Cu for Pd to nucleate on the SLG surface. The deposited Pd NPs on the SLG surface were well-distributed with high uniformity and low defects. The Pd NP/SLG hybrid was then coated with polymer membrane layer for the selective filtration of H2. Because of the selective H2 filtration effect of the polymer membrane layer, the sensor had no responses to methane, carbon monoxide, or nitrogen dioxide gas. On the contrary, the PMMA/Pd NP/SLG hybrid sensor exhibited a good response to exposure to 2% H2: on average, 66.37% response within 1.81 min and recovery within 5.52 min. In addition, reliable and repeatable sensing behaviors were obtained when the sensor was exposed to different H2 concentrations ranging from 0.025 to 2%.

A plug flow model for chemical reactions and aerosol nucleation and growth in an alkali-containing flue gas

DEFF Research Database (Denmark)

Christensen, K. A.; Livbjerg, Hans

2000-01-01

multicomponent growth models are treated. The local gas phase composition is determined from a gas phase chemical equilibrium calculation combined with finite reaction rate kinetics for slower reactions. The model is useful in the analysis of boiler operation with respect to the formation of particles, HCl, SO2......The paper presents a numerical model for the simulation of gas to particle conversion and the chemical changes during cooling of a flue gas from the combustion of fuels rich in volatile alkali species. For the homogeneous nucleation of alkali species the model uses the classical theory modified...

Effect of molecular structure on fragmentation of isolated organic molecules in solid rare gas matrices