Kinetic studies on the reduction of iron ore nuggets by devolatilization of lean-grade coal

NASA Astrophysics Data System (ADS)

Biswas, Chanchal; Gupta, Prithviraj; De, Arnab; Chaudhuri, Mahua Ghosh; Dey, Rajib

2016-12-01

An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200°C for 10-120 min. The reduced samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chemical analysis. A good degree of metallization and reduction was achieved. Gas diffusion through the solid was identified as the reaction-rate-controlling resistance; however, during the initial period, particularly at lower temperatures, resistance to interfacial chemical reaction was also significant, though not dominant. The apparent rate constant was observed to increase marginally with decreasing size of the particles constituting the nuggets. The apparent activation energy of reduction was estimated to be in the range from 49.640 to 51.220 kJ/mol and was not observed to be affected by the particle size. The sulfur and carbon contents in the reduced samples were also determined.

Synthesis and devolatilization of M-97 NVB silicone gum compounded into silica reinforced silicone base

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, J.W.

1986-06-01

Silica reinforced silicon bases having 0.31 weight percent vinyl content were prepared by using a blend of low and high vinyl content devolatilized M-97 NVB silicone gum. The M-97 NVB is a custom dimethyl-, diphenyl-, methylvinylsiloxane gum. The silicon gum was devolatilized to evaluate the anticipated improved handling characteristics. Previous procured batches of M-97 NVB had not been devolatilized and difficult handling problems were encountered. The synthesis, devolatilization, and compound processes for the M-97 NVB silicone gum are discussed.

A comparison of simple global kinetic models for coal devolatilization with the CPD model

DOE PAGES

Richards, Andrew P.; Fletcher, Thomas H.

2016-08-01

Simulations of coal combustors and gasifiers generally cannot incorporate the complexities of advanced pyrolysis models, and hence there is interest in evaluating simpler models over ranges of temperature and heating rate that are applicable to the furnace of interest. In this paper, six different simple model forms are compared to predictions made by the Chemical Percolation Devolatilization (CPD) model. The model forms included three modified one-step models, a simple two-step model, and two new modified two-step models. These simple model forms were compared over a wide range of heating rates (5 × 10 3 to 10 6 K/s) at finalmore » temperatures up to 1600 K. Comparisons were made of total volatiles yield as a function of temperature, as well as the ultimate volatiles yield. Advantages and disadvantages for each simple model form are discussed. In conclusion, a modified two-step model with distributed activation energies seems to give the best agreement with CPD model predictions (with the fewest tunable parameters).« less

Devolatilization of oil sludge in a lab-scale bubbling fluidized bed.

PubMed

Liu, Jianguo; Jiang, Xiumin; Han, Xiangxin

2011-01-30

Devolatilization of oil sludge pellets was investigated in nitrogen and air atmosphere in a lab-scale bubbling fluidized bed (BFB). Devolatilization times were measured by the degree of completion of the evolution of the volatiles for individual oil sludge pellets in the 5-15 mm diameter range. The influences of pellet size, bed temperature and superficial fluidization velocity on devolatilization time were evaluated. The variation of devolatilization time with particle diameter was expressed by the correlation, τ(d) = Ad(p)(N). The devolatilization time to pellet diameter curve shows nearly a linear increase in nitrogen, whereas an exponential increase in air. No noticeable effect of superficial fluidization velocity on devolatilization time in air atmosphere was observed. The behavior of the sludge pellets in the BFB was also focused during combustion experiments, primary fragmentation (a micro-explosive combustion phenomenon) was observed for bigger pellets (>10mm) at high bed temperatures (>700 °C), which occurred towards the end of combustion and remarkably reduce the devolatilization time of the oil sludge pellet. The size analysis of bed materials and fly ash showed that entire ash particle was entrained or elutriated out of the BFB furnace due to the fragile structure of oil sludge ash particles. Copyright © 2010 Elsevier B.V. All rights reserved.

Performance characteristics of a slagging gasifier for MHD combustor systems

NASA Technical Reports Server (NTRS)

Smith, K. O.

1979-01-01

The performance of a two stage, coal combustor concept for magnetohydrodynamic (MHD) systems was investigated analytically. The two stage MHD combustor is comprised of an entrained flow, slagging gasifier as the first stage, and a gas phase reactor as the second stage. The first stage was modeled by assuming instantaneous coal devolatilization, and volatiles combustion and char gasification by CO2 and H2O in plug flow. The second stage combustor was modeled assuming adiabatic instantaneous gas phase reactions. Of primary interest was the dependence of char gasification efficiency on first stage particle residence time. The influence of first stage stoichiometry, heat loss, coal moisture, coal size distribution, and degree of coal devolatilization on gasifier performance and second stage exhaust temperature was determined. Performance predictions indicate that particle residence times on the order of 500 msec would be required to achieve gasification efficiencies in the range of 90 to 95 percent. The use of a finer coal size distribution significantly reduces the required gasifier residence time for acceptable levels of fuel use efficiency. Residence time requirements are also decreased by increased levels of coal devolatilization. Combustor design efforts should maximize devolatilization by minimizing mixing times associated with coal injection.

Dehydration kinetics of shocked serpentine

NASA Technical Reports Server (NTRS)

Tyburczy, James A.; Ahrens, Thomas J.

1988-01-01

Experimental rates of dehydration of shocked and unshocked serpentine were determined using a differential scanning calorimetric technique. Dehydration rates in shocked serpentine are enhanced by orders of magnitude over corresponding rates in unshocked material, even though the impact experiments were carried out under conditions that inhibited direct impact-induced devolatilization. Extrapolation to temperatures of the Martian surface indicates that dehydration of shocked material would occur 20 to 30 orders of magnitude more rapidly than for unshocked serpentine. The results indicate that impacted planetary surfaces and associated atmospheres would reach chemical equilibrium much more quickly than calculations based on unshocked material would indicate, even during the earliest, coldest stages of accretion. Furthermore, it is suggested that chemical weathering of shocked planetary surfaces by solid-gas reactions would be sufficiently rapid that true equilibrium mineral assemblages should form.

Devolatilization Analysis in a Twin Screw Extruder by using the Flow Analysis Network (FAN) Method

NASA Astrophysics Data System (ADS)

Tomiyama, Hideki; Takamoto, Seiji; Shintani, Hiroaki; Inoue, Shigeki

We derived the theoretical formulas for three mechanisms of devolatilization in a twin screw extruder. These are flash, surface refreshment and forced expansion. The method for flash devolatilization is based on the equation of equilibrium concentration which shows that volatiles break off from polymer when they are relieved from high pressure condition. For surface refreshment devolatilization, we applied Latinen's model to allow estimation of polymer behavior in the unfilled screw conveying condition. Forced expansion devolatilization is based on the expansion theory in which foams are generated under reduced pressure and volatiles are diffused on the exposed surface layer after mixing with the injected devolatilization agent. Based on these models, we developed the simulation software of twin-screw extrusion by the FAN method and it allows us to quantitatively estimate volatile concentration and polymer temperature with a high accuracy in the actual multi-vent extrusion process for LDPE + n-hexane.

Updraft Fixed Bed Gasification Aspen Plus Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

2007-09-27

The updraft fixed bed gasification model provides predictive modeling capabilities for updraft fixed bed gasifiers, when devolatilization data is available. The fixed bed model is constructed using Aspen Plus, process modeling software, coupled with a FORTRAN user kinetic subroutine. Current updraft gasification models created in Aspen Plus have limited predictive capabilities and must be "tuned" to reflect a generalized gas composition as specified in literature or by the gasifier manufacturer. This limits the applicability of the process model.

Reaction rate kinetics for in situ combustion retorting of Michigan Antrim oil shale

USGS Publications Warehouse

Rostam-Abadi, M.; Mickelson, R.W.

1984-01-01

The intrinsic reaction rate kinetics for the pyrolysis of Michigan Antrim oil shale and the oxidation of the carbonaceous residue of this shale have been determined using a thermogravimetric analysis method. The kinetics of the pyrolysis reaction were evaluated from both isothermal and nonisothermal rate data. The reaction was found to be second-order with an activation energy of 252.2 kJ/mole, and with a frequency factor of 9.25 ?? 1015 sec-1. Pyrolysis kinetics were not affected by heating rates between 0.01 to 0.67??K/s. No evidence of any reactions among the oil shale mineral constituents was observed at temperatures below 1173??K. However, it was found that the presence of pyrite in oil shale reduces the primary devolatilization rate of kerogen and increases the amount of residual char in the spent shale. Carbonaceous residues which were prepared by heating the oil shale at a rate of 0.166??K/s to temperatures between 923??K and 1073??K, had the highest reactivities when oxidized at 0.166??K/s in a gas having 21 volume percent oxygen. Oxygen chemisorption was found to be the initial precursor to the oxidation process. The kinetics governing oxygen chemisorption is (Equation Presented) where X is the fractional coverage. The oxidation of the carbonaceous residue was found also to be second-order. The activation energy and the frequency factor determined from isothermal experiments were 147 kJ/mole and 9.18??107 sec-1 respectively, while the values of these parameters obtained from a nonisothermal experiment were 212 kJ/mole and 1.5??1013 sec-1. The variation in the rate constants is attributed to the fact that isothermal and nonisothermal analyses represent two different aspects of the combustion process.

Witness of fluid-flow organization during high-pressure antigorite dehydration

NASA Astrophysics Data System (ADS)

López Sánchez-Vizcaíno, Vicente; Padrón-Navarta, José Alberto; Garrido, Carlos J.; Gómez-Pugnaire, María. Teresa

2010-05-01

The link between devolatilization reactions and fluid flow is crucial to unravel important geodynamic processes in subduction zones as deformation and element transfer is extremely controlled by the presence of water. At high confining pressure, significant fluid pressure gradients are expected in a reacting rock being dehydrated, because of its rather limited permeability [1]. Compactation-driven fluid flow seems to be an intrinsic mechanism occurring at devolatilization of viscolastic rocks. Nevertheless, and despite the important implications of this coupled deformation/fluid-migration mechanism for fluid transport, a conclusive confirmation of these processes by petrological and textural evidences in metamorphic terrains has been hampered by the scarcity of devolatilization fronts in the geological record. Evidences of high-pressure antigorite dehydration found at Cerro del Almirez (Betic Cordillera, Spain) [2] represent a noteworthy exception. Here, the transition between the hydrous protolith (antigorite serpentinite) and the prograde product assemblage (olivine + orthopyroxene + chlorite, chlorite harzburgite) is extremely well preserved and can be surveyed in detail. The maximum stability of the antigorite has been experimentally determined at ~680°C at 1.6-1.9 GPa [3]. Antigorite dehydration is accompanied by release of high amounts of high-pressure water-rich fluids (~ 9 wt.% fluid). Distinctive layers (up to 1 m thick) of transitional lithologies occur in between atg-serpentinite and chl-harburgite all along the devolatilization front, consisting of (1) chlorite-antigorite olivine-serpentinite, which gradually changes to (2) chlorite-antigorite-olivine-orthopyroxene serpentinite. These transitional lithologies are more massive and darker in color than atg-serpentinite and largely consist of coarse sized grains of antigorite and chlorite (250-500 μm). Antigorite in these assemblages is characterized by microstructural disorder features, which are lacking in antigorite far from the devolatilization front [4]. The sharp appearance of chlorite (Chl-in), crosscutting the serpentinite foliation, and coarsening of olivine define the upper limit of the transitional lithologies, whereas the lower limit (Atg-out) is gradational to chl-harzburgite. The modal increase of orthopyroxene is concomitant with the gradual disappearance of antigorite. The gradual disappearance of antigorite over short distances leads to the final prograde assemblage in the Chl-harzburgite with two contrasting textures: (1) coarse granular texture and (2) an intriguing spinifex-like texture (arborescent growth of centimeter-sized olivine and orthopyroxene). Both textures alternate at the meter to tens of meters scale over the entire massif. We interpret these textures as the result of contrasting pore fluid overpressure, reaction rates and fluid-flow organization shortly after the antigorite breakdown. These observations will be discussed on the frame of the reaction kinetic and the propagation of deformation associated to fluid pressure gradients. [1] Connolly, Journal of Geophysical Research 112 (B8), 18 (1997). [2] Trommsdorff, López Sánchez-Vizcaíno, Gómez-Pugnaire et al., Contrib Mineral Petr 132 (2), 139 (1998). [3] Padrón-Navarta, Hermann, Garrido et al., Contrib Mineral Petr 159 (1), 25 (2010). [4] Padrón-Navarta, López Sánchez-Vizcaíno, Garrido et al., Contrib Mineral Petr 156 (5), 679 (2008).

Volatile-bearing phases in carbonaceous chondrites: Compositions, modal abundance, and reaction kinetics

NASA Technical Reports Server (NTRS)

Ganguly, Jibamitra

1990-01-01

The spectral and density characteristics of Phobos and Deimos (the two small natural satellites of Mars) strongly suggest that a significant fraction of the near-earth asteroids are made of carbonaceous chondrites, which are rich in volatile components and, thus, could serve as potential resources for propellants and life supporting systems in future planetary missions. However, in order to develop energy efficient engineering designs for the extraction of volatiles, knowledge of the nature and modal abundance of the minerals in which the volatiles are structurally bound and appropriate kinetic data on the rates of the devolatilization reactions is required. Theoretical calculations to predict the modal abundances and compositions of the major volatile-bearing and other mineral phases that could develop in the bulk compositions of C1 and C2 classes (the most volatile rich classes among the carbonaceous chondrites) were performed as functions of pressure and temperature. The rates of dehydration of talc at 585, 600, 637, and 670 C at P(total) = 1 bar were determine for the reaction: Talc = 3 enstatite + quartz + water. A scanning electron microscopic study was conducted to see if the relative abundance of phases can be determined on the basis of the spectral identification and x ray mapping. The results of this study and the other studies within the project are discussed.

A kinetic study on the catalysis of KCl, K2SO4, and K2CO3 during oxy-biomass combustion.

PubMed

Deng, Shuanghui; Wang, Xuebin; Zhang, Jiaye; Liu, Zihan; Mikulčić, Hrvoje; Vujanović, Milan; Tan, Houzhang; Duić, Neven

2018-07-15

Biomass combustion under the oxy-fuel conditions (Oxy-biomass combustion) is one of the approaches achieving negative CO 2 emissions. KCl, K 2 CO 3 and K 2 SO 4 , as the major potassium species in biomass ash, can catalytically affect biomass combustion. In this paper, the catalysis of the representative potassium salts on oxy-biomass combustion was studied using a thermogravimetric analyzer (TGA). Effects of potassium salt types (KCl, K 2 CO 3 and K 2 SO 4 ), loading concentrations (0, 1, 3, 5, 8 wt%), replacing N 2 by CO 2 , and O 2 concentrations (5, 20, 30 vol%) on the catalysis degree were discussed. The comparison between TG-DTG curves of biomass combustion before and after water washing in both the 20%O 2 /80%N 2 and 20%O 2 /80%CO 2 atmospheres indicates that the water-soluble minerals in biomass play a role in promoting the devolatilization and accelerating the char-oxidation; and the replacement of N 2 by CO 2 inhibits the devolatilization and char-oxidation processes during oxy-biomass combustion. In the devolatilization stage, the catalysis degree of potassium monotonously increases with the increase of potassium salt loaded concentration. The catalysis degree order of the studied potassium salts is K 2 CO 3  > KCl > K 2 SO 4 . In the char-oxidation stage, with the increase of loading concentration the three kinds of potassium salts present inconsistent change tendencies of the catalysis degree. In the studied loading concentrations from 0 to 8 wt%, there is an optimal loading concentration for KCl and K 2 CO 3 , at 3 and 5 wt%, respectively; while for K 2 SO 4 , the catalysis degree on char-oxidation monotonically increases with the loading potassium concentration. For most studied conditions, regardless of the potassium salt types or the loading concentrations or the combustion stages, the catalysis degree in the O 2 /CO 2 atmosphere is stronger than that in the O 2 /N 2 atmosphere. The catalysis degree is also affected by the O 2 concentrations, and the lowest catalysis degree is generally around 20 vol% O 2 concentration. The kinetic parameters under the different studied conditions are finally obtained. Copyright © 2018 Elsevier Ltd. All rights reserved.

Devolatilization of coal particles in a flat flame -- Experimental and modeling study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Therssen, E.; Gourichon, L.; Delfosse, L.

1995-10-01

Pulverized coals have been tested under the conditions of industrial flames, with high heating rate and high temperatures. The chars were collected after different pyrolysis times. For eight coals, the devolatilized fraction of coal has been measured, as well as those of carbon, hydrogen and nitrogen. During pyrolysis, the evolution of the texture of the grains has been studied by measurement of their microporous surface area, which undergoes a large increase, depending on coal rank. The composition of the volatiles, as deduced from the ultimate and proximate analysis of chars, showed high volatile bituminous coals to essentially produce tars withmore » an aromatic structure. Low and medium volatile bituminous coals produced light hydrocarbons on devolatilization and the char`s surface area continued increasing slowly during the whole of devolatilization, according to the slow increase of the fraction of hydrogen devolatilized. The char`s reactivity with oxygen was followed by measurements of Active Surface Area (ASA). It was shown that the ASA continuously decreases during devolatilization. Five models of devolatilization in the literature were tested and compared to the experimental results, assuming first-order reactions with respect to the remaining volatile matter. Badzioch`s model correctly fitted the experimental results and values of the rate constant obtained by computer trial and error adjustment were higher for lower ranks of the four bituminous coals. Anthony`s model also fits the measurements, provided an adjustment of the preexponential factor of activation energy for which it is shown that an infinite number of such pairs is suitable. If the model is run isothermally at the flame`s peak temperature, it also correctly fits the experimental results.« less

The Chaotic Terrains of Mercury: A History of Large-Scale Crustal Devolatilization

NASA Astrophysics Data System (ADS)

Rodriguez, J. A. P.; Domingue, D. L.; Berman, D. C.; Kargel, J. S.; Baker, V. R.; Teodoro, L. F.; Banks, M.; Leonard, G.

2018-05-01

Approximately 400 million years after the Caloris basin impact, extensive collapse formed Mercury's chaotic terrains. Collapse likely resulted from regionally elevated heat flow devolatilizing crustal materials along NE and NW extensional faults.

Pyrolytic and Kinetic Characteristics of the Thermal Decomposition of Perilla frutescens Polysaccharide

PubMed Central

Zhou, Quancheng; Sheng, Guihua

2012-01-01

The thermal decomposition of Perilla frutescens polysaccharide was examined by thermogravimetry, differential thermogravimetry, and differential thermal analysis. The results showed that the mass loss of the substance proceeded in three steps. The first stage can be attributed to the expulsion of the water from ambient temperature to 182°C. The second stage corresponded to devolatilization from 182°C to 439°C. The residue slowly degraded in the third stage. The weight loss in air is faster than that in nitrogen, because the oxygen in air accelerated the pyrolytic reaction speed reaction. The heating rate significantly affected the pyrolysis of the sample. Similar activation energies of the degradation process (210–211 kJ mol−1) were obtained by the FWO, KAS, and Popescu techniques. According to Popescu mechanism functions, the possible kinetic model was estimated to be Avrami–Erofeev 20 g(α) = [−ln(1–α)]4. PMID:23300715

Dynamic compression and volatile release of carbonates

NASA Technical Reports Server (NTRS)

Tyburczy, J. A.; Ahrens, T. J.

1984-01-01

Particle velocity profiles upon shock compression and isentropic releases were measured for polycrystalline calcite. The Solenhofen limestone release paths lie, close to the Hugoniot. Calcite 3 to 2 transition, upon release, was observed, but rarefaction shocks were not detected. The equation of state is used to predict the fraction of material devolatilized upon isentropic release as a function of shock pressure. The effect of ambient partial pressure of CO2 on the calculations is demonstrated and considered in models of atmospheric evolution by impact induced mineral devolatilization. The radiative characteristics of shocked calcite indicate that localization of thermal energy occurs under shock compression. Shock entropy calculations result in a minimum estimate of 90% devolatilization upon complete release from 10 GPa. Isentropic release paths from calculated continuum Hugoniot temperatures cross into the CaO (solid) + CO2 (vapor) field at improbably low pressures. It is found that release paths from measured shock temperatures cross into the melt plus vapor field at pressures greater than .5 GPa, which suggests that devolatilization is initiated at the shear banding sites.

Impact-induced devolatilization of CaSO4 anhydrite and implications for K-T extinctions: Preliminary results

NASA Technical Reports Server (NTRS)

Tyburczy, James A.; Ahrens, Thomas J.

1993-01-01

The recent suggestions that the target area for the K-T bolide may have been a sulfate-rich evaporite and that the resulting sulfuric acid-rich aerosol was responsible for the subsequent cooling of the Earth and the resulting biological extinctions has prompted us to experimentally examine the impact-induced devolatization of the sulfate minerals anhydrite (CaSO4) and gypsum (CaSO4(2H2O)). Preliminary results for anhydrite are reported. Up to 42 GPa peak shock pressure, little or no devolatilization occurs, consistent with chemical thermodynamic calculations. Calculation of the influence of the partial pressure of the gas species on impact-induced devolatilization suggests that an even greater amount of sulfur than that proposed by Brett could have been released to the atmosphere by an impact into a sulfate-rich layer. Solid recovery, impact-induced devolatilization experiments were performed on the Caltech 20mm gun using vented, stainless steel sample assemblies.

Ab initio calculations and kinetic modeling of thermal conversion of methyl chloride: implications for gasification of biomass.

PubMed

Singla, Mallika; Rasmussen, Morten Lund; Hashemi, Hamid; Wu, Hao; Glarborg, Peter; Pelucchi, Matteo; Faravelli, Tiziano; Marshall, Paul

2018-04-25

Limitations in current hot gas cleaning methods for chlorine species from biomass gasification may be a challenge for end use such as gas turbines, engines, and fuel cells, all requiring very low levels of chlorine. During devolatilization of biomass, chlorine is released partly as methyl chloride. In the present work, the thermal conversion of CH3Cl under gasification conditions was investigated. A detailed chemical kinetic model for pyrolysis and oxidation of methyl chloride was developed and validated against selected experimental data from the literature. Key reactions of CH2Cl with O2 and C2H4 for which data are scarce were studied by ab initio methods. The model was used to analyze the fate of methyl chloride in gasification processes. The results indicate that CH3Cl emissions will be negligible for most gasification technologies, but could be a concern for fluidized bed gasifiers, in particular in low-temperature gasification. The present work illustrates how ab initio theory and chemical kinetic modeling can help to resolve emission issues for thermal processes in industrial scale.

Shock-induced devolatilization of calcium sulfate and implications for K-T extinctions

NASA Technical Reports Server (NTRS)

Chen, Guangqing; Tyburczy, James A.; Ahrens, Thomas J.

1994-01-01

The devolatilization of calcium sulfate, which is present in the target rock of the Chicxulub, Mexico impact structure, and dispersal in the stratosphere of the resultant sulfuric acid aerosol have been suggested as a possible mechanism for the Cretaceous-Tertiary extinctions. We measured the amount of SO2 produced from two shock-induced devolatilization reactions of calcium sulfate up to 42 GPa in the laboratory. We found both to proceed to a much lower extent than calculated by equilibrium thermodynamic calculations. Reaction products are found to be approx. 10(exp -2) times those calculated for equilibrium. Upon modeling the quantity of sulfur oxides degassed into the atmosphere from shock devolatilization of CaSO4 in the Chicxulub lithographic section, the resulting 9 x 10(exp 16) to 6 x 10(exp 17) g (in sulfur mass) is lower by a factor of 10-100 than previous upper limit estimates, the related environmental stress arising from the resultant global cooling and fallout of acid rain is insufficient to explain the widespread K-T extinctions.

Reduction of Iron-Oxide-Carbon Composites: Part I. Estimation of the Rate Constants

NASA Astrophysics Data System (ADS)

Halder, S.; Fruehan, R. J.

2008-12-01

A new ironmaking concept using iron-oxide-carbon composite pellets has been proposed, which involves the combination of a rotary hearth furnace (RHF) and an iron bath smelter. This part of the research focuses on studying the two primary chemical kinetic steps. Efforts have been made to experimentally measure the kinetics of the carbon gasification by CO2 and wüstite reduction by CO by isolating them from the influence of heat- and mass-transport steps. A combined reaction model was used to interpret the experimental data and determine the rate constants. Results showed that the reduction is likely to be influenced by the chemical kinetics of both carbon oxidation and wüstite reduction at the temperatures of interest. Devolatilized wood-charcoal was observed to be a far more reactive form of carbon in comparison to coal-char. Sintering of the iron-oxide at the high temperatures of interest was found to exert a considerable influence on the reactivity of wüstite by virtue of altering the internal pore surface area available for the reaction. Sintering was found to be predominant for highly porous oxides and less of an influence on the denser ores. It was found using an indirect measurement technique that the rate constants for wüstite reduction were higher for the porous iron-oxide than dense hematite ore at higher temperatures (>1423 K). Such an indirect mode of measurement was used to minimize the influence of sintering of the porous oxide at these temperatures.

Pyrolysis reaction models of waste tires: Application of Master-Plots method for energy conversion via devolatilization.

PubMed

Irmak Aslan, Dilan; Parthasarathy, Prakash; Goldfarb, Jillian L; Ceylan, Selim

2017-10-01

Land applied disposal of waste tires has far-reaching environmental, economic, and human health consequences. Pyrolysis represents a potential waste management solution, whereby the solid carbonaceous residue is heated in the absence of oxygen to produce liquid and gaseous fuels, and a solid char. The design of an efficient conversion unit requires information on the reaction kinetics of pyrolysis. This work is the first to probe the appropriate reaction model of waste tire pyrolysis. The average activation energy of pyrolysis was determined via iso-conversional methods over a mass fraction conversion range between 0.20 and 0.80 to be 162.8±23.2kJmol -1 . Using the Master Plots method, a reaction order of three was found to be the most suitable model to describe the pyrolytic decomposition. This suggests that the chemical reactions themselves (cracking, depolymerization, etc.), not diffusion or boundary layer interactions common with carbonaceous biomasses, are the rate-limiting steps in the pyrolytic decomposition of waste tires. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Mechanistic Investigation of Nitrogen Evolution and Corrosion with Oxy-Combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dale Tree; Andrew Mackrory; Thomas Fletcher

A premixed, staged, down-fired, pulverized coal reactor and a flat flame burner were used to study the evolution of nitrogen in coal contrasting differences in air and oxy-combustion. In the premixed reactor, the oxidizer was staged to produce a fuel rich zone followed by a burnout zone. The initial nominal fuel rich zone stoichiometric ratio (S.R.) of 0.85 selected produced higher NO reductions in the fuel rich region under oxy-combustion conditions. Air was found to be capable of similar NO reductions when the fuel rich zone was at a much lower S.R. of 0.65. At a S.R. of 0.85, oxy-combustionmore » was measured to have higher CO, unburned hydrocarbons, HCN and NH{sub 3} in the fuel rich region than air at the same S.R. There was no measured difference in the initial formation of NO. The data suggest devolatilization and initial NO formation is similar for the two oxidizers when flame temperatures are the same, but the higher CO{sub 2} leads to higher concentrations of CO and nitrogen reducing intermediates at a given equivalence ratio which increases the ability of the gas phase to reduce NO. These results are supported by flat flame burner experiments which show devolatilization of nitrogen from the coal and char to be similar for air and oxy-flame conditions at a given temperature. A model of premixed combustion containing devolatilization, char oxidation and detailed kinetics captures most of the trends seen in the data. The model suggests CO is high in oxy-combustion because of dissociation of CO{sub 2}. The model also predicts a fraction (up to 20%, dependent on S.R.) of NO in air combustion can be formed via thermal processes with the source being nitrogen from the air while in oxy-combustion equilibrium drives a reduction in NO of similar magnitude. The data confirm oxy-combustion is a superior oxidizer to air for NO control because NO reduction can be achieved at higher S.R. producing better char burnout in addition to NO from recirculated flue gas being reduced as it passes back through the flame.« less

A numerical model to simulate foams during devolatilization of polymers

NASA Astrophysics Data System (ADS)

Khan, Irfan; Dixit, Ravindra

2014-11-01

Customers often demand that the polymers sold in the market have low levels of volatile organic compounds (VOC). Some of the processes for making polymers involve the removal of volatiles to the levels of parts per million (devolatilization). During this step the volatiles are phase separated out of the polymer through a combination of heating and applying lower pressure, creating foam with the pure polymer in liquid phase and the volatiles in the gas phase. The efficiency of the devolatilization process depends on predicting the onset of solvent phase change in the polymer and volatiles mixture accurately based on the processing conditions. However due to the complex relationship between the polymer properties and the processing conditions this is not trivial. In this work, a bubble scale model is coupled with a bulk scale transport model to simulate the processing conditions of polymer devolatilization. The bubble scale model simulates the nucleation and bubble growth based on the classical nucleation theory and the popular ``influence volume approach.'' As such it provides the information of bubble size distribution and number density inside the polymer at any given time and position. This information is used to predict the bulk properties of the polymer and its behavior under the applied processing conditions. Initial results of this modeling approach will be presented.

Numerical investigation of slag formation in an entrained-flow gasifier

NASA Astrophysics Data System (ADS)

Zageris, G.; Geza, V.; Jakovics, A.

2018-05-01

A CFD mathematical model for an entrained-flow gasifier is constructed – the model of an actual gasifier is rendered in 3D and appropriately meshed. Then, the turbulent gas flow in the gasifier is modeled with the realizable k-ε approach, taking devolatilization, combustion and coal gasification in account. Various such simulations are conducted, obtaining results for different air inlet positions and by tracking particles of varying sizes undergoing devolatilization and gasification. The model identifies potential problematic zones where most particles collide with the gasifier walls, indicating risk regions where ash deposits could most likely form. In conclusion, effects on the formation of an ash layer of air inlet positioning and particle size allowed in the main gasifier tank are discussed, and viable solutions such as radial inlet positioning for decreasing the amount of undesirable deposits are proposed. We also conclude that the particular chemical reactions that take place inside the gasifier play a significant role in determining how slagging occurs inside a gasifier.

Pyrolysis and oxy-fuel combustion characteristics and kinetics of petrochemical wastewater sludge using thermogravimetric analysis.

PubMed

Chen, Jianbiao; Mu, Lin; Cai, Jingcheng; Yao, Pikai; Song, Xigeng; Yin, Hongchao; Li, Aimin

2015-12-01

The pyrolysis and oxy-fuel combustion characteristics of petrochemical wastewater sludge (PS) were studied in air (O2/N2) and oxy-fuel (O2/CO2) atmospheres using non-isothermal thermogravimetric analysis (TGA). Pyrolysis experiments showed that the weight loss profiles were almost similar up to 1050K in both N2 and CO2 atmospheres, while further weight loss took place in CO2 atmosphere at higher temperatures due to char-CO2 gasification. Compared with 20%O2/80%N2, the drying and devolatilization stage of PS were delayed in 20%O2/80%CO2 due to the differences in properties of the diluting gases. In oxy-fuel combustion experiments, with O2 concentration increasing, characteristic temperatures decreased, while characteristic combustion rates and combustion performance indexes increased. Kinetic analysis of PS decomposition under various atmospheres was performed using Coats-Redfern approach. The results indicated that, with O2 concentration increasing, the activation energies of Step 1 almost kept constant, while the values of subsequent three steps increased. Copyright © 2015 Elsevier Ltd. All rights reserved.

Predicting properties of gas and solid streams by intrinsic kinetics of fast pyrolysis of wood

DOE PAGES

Klinger, Jordan; Bar-Ziv, Ezra; Shonnard, David; ...

2015-12-12

Pyrolysis has the potential to create a biocrude oil from biomass sources that can be used as fuel or as feedstock for subsequent upgrading to hydrocarbon fuels or other chemicals. The product distribution/composition, however, is linked to the biomass source. This work investigates the products formed from pyrolysis of woody biomass with a previously developed chemical kinetics model. Different woody feedstocks reported in prior literature are placed on a common basis (moisture, ash, fixed carbon free) and normalized by initial elemental composition through ultimate analysis. Observed product distributions over the full devolatilization range are explored, reconstructed by the model, andmore » verified with independent experimental data collected with a microwave-assisted pyrolysis system. These trends include production of permanent gas (CO, CO 2), char, and condensable (oil, water) species. Elementary compositions of these streams are also investigated. As a result, close agreement between literature data, model predictions, and independent experimental data indicate that the proposed model/method is able to predict the ideal distribution from fast pyrolysis given reaction temperature, residence time, and feedstock composition.« less

Modeling of the devolatilization kinetics during pyrolysis of grape residues.

PubMed

Fiori, Luca; Valbusa, Michele; Lorenzi, Denis; Fambri, Luca

2012-01-01

Thermo-gravimetric analysis (TGA) was performed on grape seeds, skins, stalks, marc, vine-branches, grape seed oil and grape seeds depleted of their oil. The TGA data was modeled through Gaussian, logistic and Miura-Maki distributed activation energy models (DAEMs) and a simpler two-parameter model. All DAEMs allowed an accurate prediction of the TGA data; however, the Miura-Maki model could not account for the complete range of conversion for some substrates, while the Gaussian and logistic DAEMs suffered from the interrelation between the pre-exponential factor k0 and the mean activation energy E0--an obstacle that can be overcome by fixing the value of k0 a priori. The results confirmed the capabilities of DAEMs but also highlighted some drawbacks in their application to certain thermodegradation experimental data. Copyright © 2011 Elsevier Ltd. All rights reserved.

Relative Shock Effects in Mixed Powders of Calcite, Gypsum, and Quartz: A Calibration Scheme from Shock Experiments

NASA Technical Reports Server (NTRS)

Bell, Mary S.

2009-01-01

The shock behavior of calcite and gypsum is important in understanding the Cretaceous/Tertiary event and other terrestrial impacts that contain evaporite sediments in their targets. Most interest focuses on issues of devolatilization to quantify the production of CO2 or SO2 to better understand their role in generating a temporary atmosphere and its effects on climate and biota [e.g., papers in 1,2,3,4]. Devolatilization of carbonate is also important because the dispersion and fragmentation of ejecta is strongly controlled by the expansion of large volumes of gas during the impact process as well [5,6]. Shock recovery experiments for calcite yield seemingly conflicting results: early experimental devolatilization studies [7,8,9] suggested that calcite was substantially outgassed at 30 GPa (> 50%). However, the recent petrographic work of [10,11,12] presented evidence that essentially intact calcite is recovered from 60 GPa experiments. [13] reported results of shock experiments on anhydrite, gypsum, and mixtures of those phases with silica. Their observations indicate little or no devolatilization of anhydrite shocked to 42 GPa and that the fraction of sulfur, by mass, that degassed is approx.10(exp -2) of theoretical prediction. In another (preliminary) report of shock experiments on calcite, anhydrite, and gypsum, [14] observe calcite recrystallization when shock loaded at 61 GPa, only intensive plastic deformation in anhydrite shock loaded at 63 GPa, and gypsum converted to anhydrite when shock loaded at 56 GPa. [15] shock loaded anhydrite and quartz to a peak pressure of 60 GPa. All of the quartz grains were trans-formed to glass and the platy anhydrite grains were completely pseudomorphed by small crystallized anhydrite grains. However, no evidence of interaction between the two phases could be observed and they suggest that recrystallization of anhydrite grains is the result of a solid state transformation. [16] reanalyzed the calcite and anhydrite shock wave experiments of [17] using improved equations of state of porous materials and vaporized products. They determined the pressures for incipient and complete vaporization to be 32.5 and 122 GPa for anhydrite and 17.8 and 54.1 GPa for calcite, respectively, a factor of 2 to 3 lower than reported earlier by [17].

Thermogravimetric-mass spectrometric analysis on combustion of lignocellulosic biomass.

PubMed

López-González, D; Fernandez-Lopez, M; Valverde, J L; Sanchez-Silva, L

2013-09-01

Combustion characteristics of biomass main components and three lignocellulosic biomass (fir wood, eucalyptus wood and pine bark) were investigated by thermogravimetric analysis coupled with mass spectrometry. The combustion of biomass was divided into two main steps, devolatilization and char oxidation stage. Heating rate effect was also studied. Generally, the higher the heating rate, the higher the decomposition temperature. Furthermore, the weight loss rate decreased due to particle temperature gradients. Combustion kinetics were studied. Models based on reaction order (Oi), nucleation (Ni) and diffusion (Di) achieved the best fitting to the experimental data. Cellulose oxidation presented the highest activation energies. CO, CO2 and H2O were the main components evolved from combustion. Additionally, light hydrocarbons (CH4 and C2H5) were also present. Finally, nitrogen compounds were in a higher proportion than sulfur compounds being released as primary amines and NOx. Copyright © 2013 Elsevier Ltd. All rights reserved.

Permeability of gypsum samples dehydrated in air

NASA Astrophysics Data System (ADS)

Milsch, Harald; Priegnitz, Mike; Blöcher, Guido

2011-09-01

We report on changes in rock permeability induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air (dry) for up to 800 h at ambient pressure and temperatures between 378 and 423 K. Subsequently, the reaction kinetics, so induced changes in porosity, and the concurrent evolution of sample permeability were constrained. Weighing the heated samples in predefined time intervals yielded the reaction progress where the stoichiometric mass balance indicated an ultimate and complete dehydration to anhydrite regardless of temperature. Porosity showed to continuously increase with reaction progress from approximately 2% to 30%, whilst the initial bulk volume remained unchanged. Within these limits permeability significantly increased with porosity by almost three orders of magnitude from approximately 7 × 10-19 m2 to 3 × 10-16 m2. We show that - when mechanical and hydraulic feedbacks can be excluded - permeability, reaction progress, and porosity are related unequivocally.

DESIGNING AN OPPORTUNITY FUEL WITH BIOMASS AND TIRE-DERIVED FUEL FOR COFIRING AT WILLOW ISLAND GENERATING STATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

K. Payette; D. Tillman

During the period January 1, 2001-March 31, 2001, Allegheny Energy Supply Co., LLC (Allegheny) finalized the engineering of the Willow Island cofiring project, completed the fuel characterizations for both the Willow Island and Albright Generating Station projects, and initiated construction of both projects. Allegheny and its contractor, Foster Wheeler, selected appropriate fuel blends and issued purchase orders for all processing and mechanical equipment to be installed at both sites. This report summarizes the activities associated with the Designer Opportunity Fuel program, and demonstrations at Willow Island and Albright Generating Stations. The third quarter of the project involved completing the detailedmore » designs for the Willow Island Designer Fuel project. It also included complete characterization of the coal and biomass fuels being burned, focusing upon the following characteristics: proximate and ultimate analysis; higher heating value; carbon 13 nuclear magnetic resonance testing for aromaticity, number of aromatic carbons per cluster, and the structural characteristics of oxygen in the fuel; drop tube reactor testing for high temperature devolatilization kinetics and generation of fuel chars; thermogravimetric analyses (TGA) for char oxidation kinetics; and related testing. The construction at both sites commenced during this quarter, and was largely completed at the Albright Generating Station site.« less

Transformation of Swine Manure and Algal Consortia to Value-added Products

NASA Astrophysics Data System (ADS)

Sharara, Mahmoud A.

The swine production sector is projected to grow globally. In the past, this growth manifested itself in increased herd sizes and geographically concentrated production. Although economically sound, these trends had negative consequences on surrounding ecosystems. Over-application of manure resulted in water quality degradation, while long-term storage of manure slurries was found to promote release of potent GHG emissions. There is a need for innovative approaches for swine manure management that are compatible with current scales of production, and increasingly strict environmental regulations. This study aims to investigate the potential for incorporating gasification as part of a novel swine manure management system which utilizes liquid-solid separation and periphytic algal consortia as a phycoremediation vector for the liquid slurry. The gasification of swine manure solids, and algal biomass solids generate both a gaseous fuel product (producer gas) in addition to a biochar co-product. First, the decomposition kinetics for both feedstock, i.e., swine manure solids, and algal solids, were quantified using thermogravimetry at different heating rates (1 ~ 40°C min-1) under different atmospheres (nitrogen, and air). Pyrolysis kinetics were determined for manure solids from two farms with different manure management systems. Similarly, the pyrolysis kinetics were determined for phycoremediation algae grown on swine manure slurries. Modeling algal solids pyrolysis as first-order independent parallel reactions was sufficient to describe sample devolatilization. Combustion of swine manure solids blended with algal solids, at different ratios, showed no synergistic effects. Gasification of phycoremediation algal biomass was studied using a bench-scale auger gasification system at temperatures between 760 and 960°C. The temperature profile suggested a stratification of reaction zones common to fixed-bed reactors. The producer gas heating value ranged between 2.2 MJ m-3 at 760°C, and 3.6 MJ m-3 at 960°C. Finally, life cycle assessment (LCA) was used to evaluate a proposed swine manure management system that includes a thermochemical conversion sub-system: drying, gasification, and producer-gas combustion (boiler). Liquid manure storage (uncovered tank) was the biggest contributor to GHG emissions. Liquid slurry management stages were credited with the highest fossil fuel use. Improvements to separation and drying technologies can improve this conversion scenario.

Assessing the Role of Anhydrite in the KT Mass Extinction: Hints from Shock-loading Experiments

NASA Technical Reports Server (NTRS)

Skala, R.; Lnagenhorst, F.; Hoerz, F.

2004-01-01

Various killing mechanisms have been suggested to contribute to the mass extinctions at the KT boundary, including severe, global deterioration of the atmosphere and hydrosphere due to SO(x) released from heavily shocked, sulfate-bearing target rocks. The devolatilization of anhydrite is predominantly inferred from thermodynamic considerations and lacks experimental confirmation. To date, the experimentally determined shock behavior of anhydrite is limited to solid-state effects employing X-ray diffraction methods. The present report employs additional methods to characterize experimentally shocked anhydrite.

Modelisation et simulation de pyrolyse de pneus usages dans des reacteurs de laboratoire et industriel

NASA Astrophysics Data System (ADS)

Lanteigne, Jean-Remi

The present thesis covers an applied study on tire pyrolysis. The main objective is to develop tools to allow predicting the production and the quality of oil from tire pyrolysis. The first research objective consisted in modelling the kinetics of tires pyrolysis in a reactor, namely an industrial rotary drum operating in batch mode. A literature review performed later demonstrated that almost all kinetics models developed to represent tire pyrolysis could not represent the actual industrial process with enough accuracy. Among the families of kinetics models for pyrolysis, three have been identified: models with one single global reaction, models with multiple combined parallel reactions, and models with multiple parallel and series reactions. It was observed that these models show limitations. In the models with one single global reaction and with multiple parallels reactions, the production of each individual pyrolytic product cannot be predicted, but only for combined volatiles. Morevoer, the mass term in the kinetics refers to the final char weight (Winfinity) that varies with pyrolysis conditions, which yields less robust models. Also, despite the fact that models with multiple parallels and series reactions can predict the rate of production for each pyrolysis product, the selectivities are determined for operating temperatures instead of real mass temperatures, giving models for which parameters tuning is not adequate when used at the industrial scale. A new kinetics model has been developed, allowing predicting the rate of production of noncondensable gas, oil, and char from tire pyrolysis. The novelty of this model is the consideration of intrinsic selectivities for each product as a function of temperature. This hypothesis has been assumed valid considering that in the industrial pyrolysis process, pyrolysis kinetics is limiting. The developed model considers individual kinetics for each of the three pyrolytic products proportional to the global decomposition kinetics of pyrolysables. The simulation with data obtained in industrial operation showed the robustness of the model to predict with accuracy in transient regime, tires pyrolysis, with the help of model parameters obtained at laboratory scale, namely in regards of the trigger of production, the residence time of tires (dynamic production) and the amount of oil produced (cumulative yield). It is a novel way to model pyrolysis that could be extrapolated to new waste materials. The second objective of this doctoral research was to determine the evolution of specific tires specific heat during pyrolysis and the enthalpy of pyrolysis. The origin of this objective comes from a primary contradiction. With few exceptions, it is acknowledged that organic materials pyrolysis is globally an endothermic phenomenon. At the opposite, all experiments led with laboratory apparatuses such as DSC (Differential Scanning Calorimetry) showed exothermic peaks during dynamic experiments (constant heating rate). It has been confirmed by results obtained at the industrial scale, where no sign of exothermicity has been observed. The Hess Law has also confirmed these results, that globally, pyrolysis is indeed a completely endothermic process. An accurate energy balance is required to predict mass temperature during pyrolysis, this parameter being unbindable from kinetics. An advanced investigation of char first allowed demonstrating that specific heat of solids during pyrolysis decreases with increasing temperature until the weight loss peak is reached, around 400°C, and then starts increasing again. This observation, combined with the fact that the sample loses weight during pyrolysis is considered as the major cause of the apparition of an exothermic peak in laboratory scale experiments. That is, the control system of these apparatuses generates a bias and an unavoidable overheat of the samples producing this exothermic behavior. It would thus be an artifact. On the base of new data on the evolution of global specific heat during pyrolysis, a model of the energy balance has been developed at the industrial scale to determine the enthalpy of pyrolysis. The simulation has shown that a major part of the heat transferred to the pyrolized mass would make its temperature increase. Next, an enthalpy of pyrolysis dependent of weight loss was obtained. Finally, two other terms of enthalpy have been found, namely an enthalpy for the breakage of sulfur bridges and an enthalpy for the stabilization of char when conversion approaches completion. This research will have allowed establishing a novel general methodology to determine the enthalpy of pyrolysis. More particularly, new clarifications hasve been obtained in regards to the evolution of specific heat of solids during pyrolysis and new enthalpies of pyrolysis, all endothermic, could be obtained, in agreement with the theoretical expectations. The third research objective concerned the behavior of sulfur during tires pyrolysis. With as a premise that sulfur is an intrinsic contaminant of many types of waste, it is critical to clarify its fate during pyrolysis, in the present case for waste tires. It has been observed in the literature that some quantitative analyses had been presented, but generally, the mechanisms for the distribution of sulfur within the pyrolytic products remain unclear. Thus, it was then not possible to predict the transfer of sulfur to each of the tire pyrolysis products. The results taken form literature have been complemented with a series of TGA experiments followed by complete elemental analyses of the residual solids. Mass balances have been performed in order to characterize the distribution of elements within the three products (noncondensable gas, oil, and char). A novel parameter has been created during this research: the sulfur loss selectivity. This intrinsic selectivity is a prediction of the distribution of sulfur within the pyrolysis products as a function of temperature. Three phenomena has been identified that could affect the sulfur loss selectivity. First, the natural devolatilization of sulfur due to pyrolysis. Next, the sulfur devolatilization due to the desulfurization of the solid matrix by hydrogen and finally, the clustering of sulfur in the solid state due to metal sulfidation (zinc and iron). The results have shown that this selectivity reach a limit value of 1 when pyrolysis is limited by the kinetics and in the absence of metal. When the mass transfer is limiting at low temperature (<500°C) the selectivity will be greater than 1. At a temperature over 350°C with the presence of metals, the selectivity will be lower than 1. It is a useful tool for industrial pyrolysis processes, being a novel indicator for the distribution of contaminants during the pyrolysis of waste. A better comprehension of these mechanisms allows elaborating a better strategy when designing these industrial processes. For example, in light of this research, it could be preferable to pre-treat the tires at lower temperature to eliminate a significant part of sulfur before pyrolyzing them at high temperature. The resulting pyrolytic products would then necessitate a lighter purification post-treatment, being more efficient and more economical.

Development and numerical/experimental characterization of a lab-scale flat flame reactor allowing the analysis of pulverized solid fuel devolatilization and oxidation at high heating rates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemaire, R., E-mail: romain.lemaire@mines-douai.fr; Menanteau, S.

2016-01-15

This paper deals with the thorough characterization of a new experimental test bench designed to study the devolatilization and oxidation of pulverized fuel particles in a wide range of operating conditions. This lab-scale facility is composed of a fuel feeding system, the functioning of which has been optimized by computational fluid dynamics. It allows delivering a constant and time-independent mass flow rate of fuel particles which are pneumatically transported to the central injector of a hybrid McKenna burner using a carrier gas stream that can be inert or oxidant depending on the targeted application. A premixed propane/air laminar flat flamemore » stabilized on the porous part of the burner is used to generate the hot gases insuring the heating of the central coal/carrier-gas jet with a thermal gradient similar to those found in industrial combustors (>10{sup 5} K/s). In the present work, results issued from numerical simulations performed a priori to characterize the velocity and temperature fields in the reaction chamber have been analyzed and confronted with experimental measurements carried out by coupling particle image velocimetry, thermocouple and two-color pyrometry measurements so as to validate the order of magnitude of the heating rate delivered by such a new test bench. Finally, the main features of the flat flame reactor we developed have been discussed with respect to those of another laboratory-scale system designed to study coal devolatilization at a high heating rate.« less

Development and numerical/experimental characterization of a lab-scale flat flame reactor allowing the analysis of pulverized solid fuel devolatilization and oxidation at high heating rates

NASA Astrophysics Data System (ADS)

Lemaire, R.; Menanteau, S.

2016-01-01

This paper deals with the thorough characterization of a new experimental test bench designed to study the devolatilization and oxidation of pulverized fuel particles in a wide range of operating conditions. This lab-scale facility is composed of a fuel feeding system, the functioning of which has been optimized by computational fluid dynamics. It allows delivering a constant and time-independent mass flow rate of fuel particles which are pneumatically transported to the central injector of a hybrid McKenna burner using a carrier gas stream that can be inert or oxidant depending on the targeted application. A premixed propane/air laminar flat flame stabilized on the porous part of the burner is used to generate the hot gases insuring the heating of the central coal/carrier-gas jet with a thermal gradient similar to those found in industrial combustors (>105 K/s). In the present work, results issued from numerical simulations performed a priori to characterize the velocity and temperature fields in the reaction chamber have been analyzed and confronted with experimental measurements carried out by coupling particle image velocimetry, thermocouple and two-color pyrometry measurements so as to validate the order of magnitude of the heating rate delivered by such a new test bench. Finally, the main features of the flat flame reactor we developed have been discussed with respect to those of another laboratory-scale system designed to study coal devolatilization at a high heating rate.

Evaluating the combustion reactivity of drop tube furnace and thermogravimetric analysis coal chars with a selection of metal additives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katherine Le Manquais; Colin E. Snape; Ian McRobbie

Opportunities exist for effective coal combustion additives that can reduce the carbon content of pulverized fuel ash (PFA) to below 6%, thereby making it saleable for filler/building material applications without the need for postcombustion treatment. However, with only limited combustion data currently available for the multitude of potential additives, catalytic performance under pulverized fuel (PF) boiler conditions has received relatively little attention. This paper therefore compares the reactivity of catalyzed bituminous coal chars from thermogravimetric analysis (TGA) with those generated by devolatilization in a drop tube furnace (DTF). The principal aim was to explore the fundamental chemistry behind the chosenmore » additives' relative reactivities. Accordingly, all eight of the investigated additives increased the TGA burnout rate of the TGA and DTF chars, with most of the catalysts demonstrating consistent reactivity levels across chars from both devolatilization methods. Copper(I) chloride, silver chloride, and copper nitrate were thus identified as the most successful additives tested, but it proved difficult to establish a definitive reactivity ranking. This was largely due to the use of physical mixtures for catalyst dispersion, the relatively narrow selection of additives examined, and the inherent variability of the DTF chars. Nevertheless, one crucial exception to normal additive behavior was discovered, with copper(I) chloride perceptibly deactivating during devolatilization in the DTF, even though it remained the most effective catalyst tested. As a prolonged burnout at over 1000{sup o}C was required to replicate this deactivation effect on the TGA, the phenomenon could not be detected by typical testing procedures. Subsequently, a comprehensive TGA study showed no obvious relationship between the catalyst-induced reductions in the reaction's apparent activation energy and the samples recorded burnout rates.« less

Ammonium loss and nitrogen isotopic fractionation in biotite as a function of metamorphic grade in metapelites from western Maine, USA

NASA Astrophysics Data System (ADS)

Plessen, Birgit; Harlov, Daniel E.; Henry, Darrell; Guidotti, Charles V.

2010-08-01

Ammonium fixed in micas of metamorphic rocks is a sensitive indicator both of organic-inorganic interactions during diagenesis as well as of the devolatilization history and fluid/rock interaction during metamorphism. In this study, a collection of geochemically well-characterized biotite separates from a series of graphite-bearing Paleozoic greenschist- to upper amphibolite-facies metapelites, western Maine, USA, were analyzed for ammonium nitrogen ( NH4+-N) contents and isotopic composition (δ 15N NH4) using the HF-digestion distillation technique followed by the EA-IRMS technique. Biotite separates, sampled from 9 individual metamorphic zones, contain 3000 to 100 ppm NH4+-N with a wide range in δ 15N from +1.6‰ to +9.1‰. Average NH4+-N contents in biotite show a distinct decrease from about 2750 ppm for the lowest metamorphic grade (˜500 °C) down to 218 ppm for the highest metamorphic grade (˜685 °C). Decreasing abundances in NH4+ are inversely correlated in a linear fashion with increasing K + in biotite as a function of metamorphic grade and are interpreted as a devolatilization effect. Despite expected increasing δ 15N NH4 values in biotite with nitrogen loss, a significant decrease from the Garnet Zones to the Staurolite Zones was found, followed by an increase to the Sillimanite Zones. This pattern for δ 15N NH4 values in biotite inversely correlates with Mg/(Mg + Fe) ratios in biotite and is discussed in the framework of isotopic fractionation due to different exchange processes between NH4+-NH or NH4+-N, reflecting devolatilization history and redox conditions during metamorphism.

OXIDATION AND DEVOLATILIZATION OF NITROGEN IN COAL CHAR

EPA Science Inventory

The reactions of organically-bound nitrogen in coal char during combustion have been studied in a laboratory furnace using size-graded char particles prepared by the pyrolysis of a Montana lignite. The time-resolved variations of nitrogen-to-carbon ratio during char oxidation hav...

The Bulk Elemental Composition of any Terrestrial Planets in the Alpha Centauri System

NASA Astrophysics Data System (ADS)

Lineweaver, C. H.; Schonberger, B. F. G.; Robles, J. A.

2010-04-01

Based on the devolatilization patterns in the solar system, and on the differences in the chemical compositions of the Sun and Alpha Centauri, we make estimates of the chemical composition of any Earth-like planets in the Alpha Centauri system.

Coal Combustion Science quarterly progress report, April--June 1992. Task 1, Coal devolatilization: Task 2, Coal char combustion; Task 3, Fate of mineral matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardesty, D.R.; Hurt, R.H.; Baxter, L.L.

1992-09-01

The objective of this work is to support the Office of Fossil Energy in executing research on coal combustion science. This project consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center (PETC) Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency (IEA) Coal Combustion Science Project. Specific tasks include: The characterization of the physical and chemical processes that constitute the early devolatilization phase of coal combustion: Characterization of the combustion behavior of selected coals under conditions relevant to industria pulverized coal-fired furnaces; and to establish a quantitative understanding of themore » mechanisms and rates of transformation, fragmentation, and deposition of mineral matter in coal combustion environments as a function of coal type, particle size and temperature, the initial forms and distributions of mineral species in the unreacted coal, and the local gas temperature and composition.« less

Is torrefaction of polysaccharides-rich biomass equivalent to carbonization of lignin-rich biomass?

PubMed

Bilgic, E; Yaman, S; Haykiri-Acma, H; Kucukbayrak, S

2016-01-01

Waste biomass species such as lignin-rich hazelnut shell (HS) and polysaccharides-rich sunflower seed shell (SSS) were subjected to torrefaction at 300°C and carbonization at 600°C under nitrogen. The structural variations in torrefied and carbonized biomasses were compared. Also, the burning characteristics under dry air and pure oxygen (oxy-combustion) conditions were investigated. It was concluded that the effects of carbonization on HS are almost comparable with the effects of torrefaction on SSS in terms of devolatilization and deoxygenation potentials and the increases in carbon content and the heating value. Consequently, it can be proposed that torrefaction does not provide efficient devolatilization from the lignin-rich biomass while it is relatively more efficient for polysaccharides-rich biomass. Heat-induced variations in biomass led to significant changes in the burning characteristics under both burning conditions. That is, low temperature reactivity of biomass reduced considerably and the burning shifted to higher temperatures with very high burning rates. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comprehensive Model of Single Particle Pulverized Coal Combustion Extended to Oxy-Coal Conditions

DOE PAGES

Holland, Troy; Fletcher, Thomas H.

2017-02-22

Oxy-fired coal combustion is a promising potential carbon capture technology. Predictive CFD simulations are valuable tools in evaluating and deploying oxy-fuel and other carbon capture technologies either as retrofit technologies or for new construction. But, accurate predictive simulations require physically realistic submodels with low computational requirements. In particular, comprehensive char oxidation and gasification models have been developed that describe multiple reaction and diffusion processes. Our work extends a comprehensive char conversion code (CCK), which treats surface oxidation and gasification reactions as well as processes such as film diffusion, pore diffusion, ash encapsulation, and annealing. In this work several submodels inmore » the CCK code were updated with more realistic physics or otherwise extended to function in oxy-coal conditions. Improved submodels include the annealing model, the swelling model, the mode of burning parameter, and the kinetic model, as well as the addition of the chemical percolation devolatilization (CPD) model. We compare our results of the char combustion model to oxy-coal data, and further compared to parallel data sets near conventional conditions. A potential method to apply the detailed code in CFD work is given.« less

Comprehensive Model of Single Particle Pulverized Coal Combustion Extended to Oxy-Coal Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holland, Troy; Fletcher, Thomas H.

Oxy-fired coal combustion is a promising potential carbon capture technology. Predictive CFD simulations are valuable tools in evaluating and deploying oxy-fuel and other carbon capture technologies either as retrofit technologies or for new construction. But, accurate predictive simulations require physically realistic submodels with low computational requirements. In particular, comprehensive char oxidation and gasification models have been developed that describe multiple reaction and diffusion processes. Our work extends a comprehensive char conversion code (CCK), which treats surface oxidation and gasification reactions as well as processes such as film diffusion, pore diffusion, ash encapsulation, and annealing. In this work several submodels inmore » the CCK code were updated with more realistic physics or otherwise extended to function in oxy-coal conditions. Improved submodels include the annealing model, the swelling model, the mode of burning parameter, and the kinetic model, as well as the addition of the chemical percolation devolatilization (CPD) model. We compare our results of the char combustion model to oxy-coal data, and further compared to parallel data sets near conventional conditions. A potential method to apply the detailed code in CFD work is given.« less

HIGH PRESSURE COAL COMBUSTON KINETICS PROJECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stefano Orsino

As part of the U.S. Department of Energy (DoE) initiative to improve the efficiency of coal-fired power plants and reduce the pollution generated by these facilities, DOE has funded the High-Pressure Coal Combustion Kinetics (HPCCK) Projects. A series of laboratory experiments were conducted on selected pulverized coals at elevated pressures with the specific goals to provide new data for pressurized coal combustion that will help extend to high pressure and validate models for burnout, pollutant formation, and generate samples of solid combustion products for analyses to fill crucial gaps in knowledge of char morphology and fly ash formation. Two seriesmore » of high-pressure coal combustion experiments were performed using SRI's pressurized radiant coal flow reactor. The first series of tests characterized the near burner flame zone (NBFZ). Three coals were tested, two high volatile bituminous (Pittsburgh No.8 and Illinois No.6), and one sub-bituminous (Powder River Basin), at pressures of 1, 2, and 3 MPa (10, 20, and 30 atm). The second series of experiments, which covered high-pressure burnout (HPBO) conditions, utilized a range of substantially longer combustion residence times to produce char burnout levels from 50% to 100%. The same three coals were tested at 1, 2, and 3 MPa, as well as at 0.2 MPa. Tests were also conducted on Pittsburgh No.8 coal in CO2 entrainment gas at 0.2, 1, and 2 MPa to begin establishing a database of experiments relevant to carbon sequestration techniques. The HPBO test series included use of an impactor-type particle sampler to measure the particle size distribution of fly ash produced under complete burnout conditions. The collected data have been interpreted with the help of CFD and detailed kinetics simulation to extend and validate devolatilization, char combustion and pollutant model at elevated pressure. A global NOX production sub-model has been proposed. The submodel reproduces the performance of the detailed chemical reaction mechanism for the NBFZ tests.« less

Dynamical evidence regarding the relationship between asteroids and meteorites

NASA Technical Reports Server (NTRS)

Wetherill, G. W.

1978-01-01

Meteorites are fragments of small solar system bodies transferring into the vicinity of earth from the inner edge of the asteroid belt. Photometric measurements support an association between Apollo objects and chondritic meteorites. Dynamical arguments indicate that most Apollo objects are devolatilized comet residues, however; petrographic and cosmogonical reasons argue against this conclusion.

Comparison of the combustion reactivity of TGA and drop tube furnace chars from a bituminous coal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katherine Le Manquais; Colin Snape; Ian McRobbie

This paper compares the reactivity of chars generated in a drop tube furnace (DTF) to those from TGA. The implications of devolatilization temperature, heating rate and residence time are considered. For the smaller particle size ranges of the bituminous coal investigated (ATC), optimized devolatilization procedures were used to generate corresponding TGA burnout rates between the two char types. However, with fractions of >75 {mu}m, the DTF chars showed an increased burnout propensity when moving from combustion regime II to combustion regime III. Scanning electron microscope (SEM) images and internal surface areas indicate that this is because of incompatible char morphologies.more » Thus, while chars produced under the conditions of TGA pyrolysis strongly resemble raw coal and display an undeveloped pore network; the DTF chars are highly porous, extensively swollen and possess considerably larger internal surface areas. Subsequently, char burnout variability was quantified, with the reactivity distribution for the DTF samples found to be up to an order of magnitude more significant than for the TGA chars. This is attributed to a fluctuating devolatilization environment on the DTF. Finally, a TGA study observed a robust particle size based compensation effect for the TGA chars, with the relative reaction rates and activation energies demonstrating the presence of internal diffusion control. However this phenomenon was partly alleviated for the DTF chars, since their higher porosities reduce mass transfer restrictions. Moreover, it should be realized that DTF char fractions of <38 {mu}m, including those required to ensure true intrinsic control under the investigated burnout conditions, cannot be produced directly. This is because of bridging and sloughing in the DTF's screw-feeder. Instead, such samples must be created by grinding larger particles, which destroys the char's existing porosity. 60 refs., 9 figs., 5 tabs.« less

Causes of distal volcano-tectonic seismicity inferred from hydrothermal modeling

NASA Astrophysics Data System (ADS)

Coulon, C. A.; Hsieh, P. A.; White, R.; Lowenstern, J. B.; Ingebritsen, S. E.

2017-10-01

Distal volcano-tectonic (dVT) seismicity typically precedes eruption at long-dormant volcanoes by days to years. Precursory dVT seismicity may reflect magma-induced fluid-pressure pulses that intersect critically stressed faults. We explored this hypothesis using an open-source magmatic-hydrothermal code that simulates multiphase fluid and heat transport over the temperature range 0 to 1200 °C. We calculated fluid-pressure changes caused by a small (0.04 km3) intrusion and explored the effects of flow geometry (channelized vs. radial flow), magma devolatilization rates (0-15 kg/s), and intrusion depths (5 and 7.5 km, above and below the brittle-ductile transition). Magma and host-rock permeabilities were key controlling parameters and we tested a wide range of permeability (k) and permeability anisotropies (kh/kv), including k constant, k(z), k(T), and k(z, T, P) distributions, examining a total of 1600 realizations to explore the relevant parameter space. Propagation of potentially causal pressure changes (ΔP ≥ 0.1 bars) to the mean dVT location (6 km lateral distance, 6 km depth) was favored by channelized fluid flow, high devolatilization rates, and permeabilities similar to those found in geothermal reservoirs (k 10- 16 to 10- 13 m2). For channelized flow, magma-induced thermal pressurization alone can generate cases of Δ P ≥ 0.1 bars for all permeabilities in the range 10- 16 to 10- 13 m2, whereas in radial flow regimes thermal pressurization causes Δ P < 0.1 bars for all permeabilities. Changes in distal fluid pressure occurred before proximal pressure changes given modest anisotropies (kh/kv 10-100). Invoking k(z,T,P) and high, sustained devolatilization rates caused large dynamic fluctuations in k and P in the near-magma environment but had little effect on pressure changes at the distal dVT location. Intrusion below the brittle-ductile transition damps but does not prevent pressure transmission to the dVT site.

Characterization of fuels for second-generation PFBC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zevenhoven, C.A.P.; Hupa, M.

1997-12-31

In second-generation PFBC technology a solid fuel is partly converted in a devolatilization step (in a carbonizer) to produce a char and a pressurized fuel gas, followed by PFB combustion of the char. The fuel gas is led to the combustion chamber of a gas turbine after it is mixed with the PFBC off-gas, thus increasing the temperature at the inlet of the expansion turbine. Clearly, the optimization of the carbonizer design and operation is essential to the process. Detailed information on the behavior of solid fuels under pressurized conditions is, however, largely limited to steam and/or carbon dioxide gasificationmore » reactivities, obtained at a different combination of process parameters, such as temperature, pressure, heating rate, particle size and gas atmosphere. In the present work, the effect of temperature, pressure and heating rates on the yields of volatiles and char residue reactivity has been measured for a set of fuels ranging from bituminous coal to wood. Laboratory conditions were typical for the carbonizer and combustion reactors in a second-generation PFBC system. A pressurized thermogravimetric reactor (PTGR) operated at heating rates of around 250 K/s and a pressurized grid heater (PGH) operated at heating rates up to 3,000 K/s were used to analyze fuel devolatilization and char reactivity against carbon dioxide or steam at temperatures between 800 and 1,100 C, and 1, 10 or 25 bar total pressure. For comparison, a few experiments were repeated without a separate devolatilization step. The behavior of the various fuels were compared and related to proximate and ultimate fuel analysis. Several empirical, engineering equations are given. A simple 2-parameter model which separates intrinsic surface reactivity and physical, structure effects, very well describes the time-conversion data of the char. It was found that the fuel O/C molar ratio is a very good index for char reactivity, when the char O/C ratio itself is unknown.« less

A Chlorine-Centric Perspective on Fluid-Mediated Processes at Convergent Plate Boundaries

NASA Astrophysics Data System (ADS)

Selverstone, J.

2014-12-01

The release and migration of metamorphic fluids from subducting slabs into overlying mantle is widely recognized as a major mechanism in producing arc geochemical signatures and returning fluid-mobile elements to earth's crust and surface environments. Although the magnitudes of many geochemical fluxes are well constrained, the processes whereby mass transfer occurs in different portions of the subduction system are less well known. Chlorine stable isotopes provide a new perspective on some of these processes: Cl is hydrophilic, but decarbonation reactions favor Cl retention in minerals. Cl also shows less isotopic fractionation than other fluid-sensitive systems and may thus preserve evidence of specific fluid sources and/or fluid mixing events. Detailed studies of sedimentary sequences show that individual beds are isotopically homogeneous but large heterogeneities in δ37Cl exist across beds on a cm to m scale and vary as a function of depositional environment. Compositionally correlative medium-, high-, and ultrahigh-pressure metamorphic sequences in the Alps record decreases of 30-50% in Cl contents in the earliest stages of metamorphism, but little change thereafter. No statistically significant change in isotopic composition occurs during prograde metamorphism of individual horizons, and the same large degree of isotopic heterogeneity (up to 6‰) persists throughout the prograde devolatilization history of the rocks. Likewise, analysis of HP/UHP serpentinites and altered oceanic crust show that heterogeneous protolith compositions are preserved during transport to sub-arc depths, despite large-scale devolatilization. However, upward transport of rocks within the subduction channel results in highly localized interaction with isotopically distinct, Cl-bearing fluid packets. Overlying forearc wedge rocks also record heterogeneous and channelized interaction with distinct fluid components with different δ37Cl. Within-layer fluid compartmentalization during continuous devolatilization reactions must thus be reconciled with discontinuous, cross-layer fluid percolation out of the slab and into the wedge. The resulting implications of the chlorine data for recent mechanical models of slab-to-wedge fluid transport will be discussed.

Product distribution from pyrolysis of wood and agricultural residues

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Blasi, C.; Signorelli, G.; Di Russo, C.

1999-06-01

The pyrolysis characteristics of agricultural residues (wheat straw, olive husks, grape residues, and rice husks) and wood chips have been investigated on a bench scale. The experimental system establishes the conditions encountered by a thin (4 {times} 10{sup {minus}2} m diameter) packed bed of biomass particles suddenly exposed in a high-temperature environment, simulated by a radiant furnace. Product yields (gases, liquids, and char) and gas composition, measured for surface bed temperatures in the range 650--1000 K, reproduce trends already observed for wood. However, differences are quantitatively large. Pyrolysis of agricultural residues is always associated with much higher solid yields (upmore » to a factor of 2) and lower liquid yields. Differences are lower for the total gas, and approximate relationships exist among the ratios of the main gas species yields, indicating comparable activation energies for the corresponding apparent kinetics of formation. However, while the ratios are about the same for wood chips, rice husks, and straw, much lower values are shown by olive and grape residues. Large differences have also been found in the average values of the specific devolatilization rates. The fastest (up to factors of about 1.5 with respect to wood) have been observed for wheat straw and the slowest (up to factors of 2) for grape residues.« less

Chemical cleaning of coal by molten caustic leaching after pretreatment by low-temperature devolatilization

DOEpatents

Chriswell, Colin D.; Kaushik, Surender M.; Shah, Navin D.; Markuszewski, Richard

1989-08-22

Pretreatment of coal by devolatization at temperatures ranging from about 420.degree. C. to about 450.degree. C. for from about 10 minutes to about 30 minutes before leaching with molten caustic leads to a significant reduction in carbonate formation, greatly reducing the cost of cleaning coal on a per ton basis.

Advanced modeling of nitrogen oxide emissions in circulating fluidized bed combustors: Parametric study of coal combustion and nitrogen compound chemistries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kilpinen, P.; Kallio, S.; Hupa, M.

1999-07-01

This paper describes work-in-progress aimed at developing an emission model for circulating fluidized bed combustors using detailed homogeneous and heterogeneous chemical kinetics. The main emphasis is on nitrogen oxides (NO{sub x}, N{sub 2}O) but also unburned gases (CO, C{sub x}H{sub y}) and sulfur dioxide (SO{sub 2}) will be investigated in the long run. The hydrodynamics is described by a 1.5-dimensional model where the riser is divided into three regions: a dense bubbling bed at the bottom, a vigorously mixed splash zone, and a transport zone. The two latter zones are horizontally split into a core region and an annular region.more » The solids circulation rate is calculated from the known solids inventory and the pressure and mass balances over the entire circulation loop. The solids are divided into classes according to size and type or particle. The model assumes instantaneous fuel devolatilization at the bottom and an even distribution of volatiles in the suspension phase of the dense bed. For addition of secondary air, a complete penetration and an instantaneous mixing with the combustor gases in the core region is assumed. The temperature distribution is assumed to be known, and no energy balance is solved. A comprehensive kinetic scheme of about 300 elementary gas-phase reactions is used to describe the homogeneous oxidation of the volatiles including both hydrocarbon and volatile-nitrogen components (NH{sub 3}, HCN). Heterogeneous char combustion to CO and CO{sub 2}, and char-nitrogen conversion to NO, N{sub 2}O, and N{sub 2} are described by a single particle model that includes 15 reaction steps given in the form of 6 net reaction paths. In the paper, the model is briefly described. A special emphasis is put on the evaluation of chemistry submodels. Modeling results on nitrogen oxides' formation are compared with measured concentration profiles in a 12 MW CFBC riser from literature. The importance of accurate chemistry description on predictions is illustrated by comparing modeling results using detailed kinetics to those obtained when hydrocarbon and volatile-nitrogen oxidation are described with empirical, global kinetic rate expressions from literature. Submodels that need further improvements are discussed.« less

Subduction-Zone Metamorphic Pathway for Deep Carbon Cycling: Evidence from the Italian Alps and the Tianshan

NASA Astrophysics Data System (ADS)

Bebout, G. E.; Collins, N.; Cook-Kollars, J.; Angiboust, S.; Agard, P.; Scambelluri, M.; John, T.; Kump, L. R.

2013-12-01

Depending on the magnitude of the poorly constrained C flux in ultramafic rocks, on a global basis, sediments and altered oceanic crust (AOC) together deliver 70-95% of the C currently entering subduction zones. We are investigating extents of retention and metamorphic release of C in deeply subducted AOC and carbonate-rich sediment represented by HP/UHP meta-ophiolitic and metasedimentary rocks in the Italian Alps and in the Tianshan. Study of metapelite devolatilization in the same W. Alps suite (Bebout et al., 2013, Chem. Geol.) provides a geochemical framework for study of C behavior along prograde P-T paths similar to those experienced in forearcs of most modern subduction margins. Study of veins in the Tianshan affords examination of C mobility in UHP fluids, in later stages as metabasaltic rocks were fragmented in the subduction channel. Our results for sediments and AOC indicate impressive retention of oxidized C (carbonate) and reduced C (variably metamorphosed organic matter) to depths approaching those beneath arc volcanic fronts. In metasedimentary rocks, extensive isotopic exchange between the oxidized and reduced C resulted in shifts in both reservoirs toward upper mantle compositions. Much of the carbonate in metabasalts has C and O isotopic compositions overlapping with those for carbonate in AOC, with some HP/UHP metamorphic veins showing greater influence of organic C signatures from metasedimentary rocks. Calculations of prograde devolatilization histories using Perple-X demonstrate that, in most forearcs, very little decarbonation occurs in the more carbonate-rich rocks unless they are flushed by H2O-rich fluids from an external source, for example, from the hydrated ultramafic section of subducting slabs (cf. Gorman et al., 2006; G3) or from more nearby rocks experiencing dehydration (e.g., metapelites). A comparison of the most recently published thermal models for modern subduction zones (van Keken et al., 2011, JGR) with calculated and experimentally determined phase relations indicates that significant C loss during devolatilization (and partial melting) should occur as subducting sections traverse depths beneath arcs. The extent of C mobility due to carbonate dissolution remains uncertain. On a global basis, imbalance between subducted C input and C return flux by magmatism (excluding ultramafic inputs, ~40×20% of subducted C return via arcs and ~80×20% by all magmatism; Bebout, 2013, Treat. Geochem.) indicates net modern C return to the mantle, perhaps a reversal of Archean net outgassing (despite more rapid subduction). Global C cycle models predict that relatively small (and geologically plausible) change in the subduction/volcanic C flux could significantly affect atmospheric CO2 levels and thus global climate.

Characterization of bio-oil from induction-heating pyrolysis of food-processing sewage sludges using chromatographic analysis.

PubMed

Tsai, Wen-Tien; Lee, Mei-Kuei; Chang, Jeng-Hung; Su, Ting-Yi; Chang, Yuan-Ming

2009-05-01

In this study, gas chromatography-mass spectrometry (GC-MS) was used to analyze the pyrolytic bio-oils and gas fractions derived from the pyrolysis of industrial sewage sludges using induction-heating technique. The liquid products were obtained from the cryogenic condensation of the devolatilization fraction in a nitrogen atmosphere using a heating rate of 300 degrees C/min ranging from 25 to 500 degrees C. The analytical results showed that the pyrolysis bio-oils were very complex mixtures of organic compounds and contained a lot of nitrogenated and/or oxygenated compounds such as aliphatic hydrocarbons, phenols, pyridines, pyrroles, amines, ketones, and so on. These organic hydrocarbons containing nitrogen and/or oxygen should originate from the protein and nucleic acid textures of the microbial organisms present in the sewage sludge. The non-condensable devolatilization fractions were also composed of nitrogenated and oxygenated compounds, but contained small fractions of phenols, 1H-indoles, and fatty carboxylic acids. On the other hand, the compositions in the non-condensable gas products were principally carbon dioxide, carbon monoxide and methane analyzed by gas chromatography-thermal conductivity detector (GC-TCD).

Effects of combustion temperature on PCDD/Fs formation in laboratory-scale fluidized-bed incineration.

PubMed

Hatanaka, T; Imagawa, T; Kitajima, A; Takeuchi, M

2001-12-15

Combustion experiments in a laboratory-scale fluidized-bed reactor were performed to elucidate the effects of combustion temperature on PCDD/Fs formation during incineration of model wastes with poly(vinyl chloride) or sodium chloride as a chlorine source and copper chloride as a catalyst. Each temperature of primary and secondary combustion zones in the reactor was set independently to 700, 800, and 900 degrees C using external electric heaters. The PCDD/Fs concentration is reduced as the temperature of the secondary combustion zone increases. It is effective to keep the temperature of the secondary combustion zone high enough to reduce their release during the waste incineration. On the other hand, as the temperature of the primary combustion zone rises, the PCDD/Fs concentration also increases. Lower temperature of the primary combustion zone results in less PCDD/Fs concentration in these experimental conditions. This result is probably related to the devolatilization rate of the solid waste in the primary combustion zone. The temperature decrease slows the devolatilization rate and promotes mixing of oxygen and volatile matters from the solid waste. This contributes to completing combustion reactions, resulting in reducing the PCDD/Fs concentration.

Impact induced dehydration of serpentine and the evolution of planetary atmospheres

NASA Technical Reports Server (NTRS)

Lange, M. A.; Ahrens, T. J.

1982-01-01

Results of shock recovery experiments carried out on antigorite serpentine Mg3Si2O5(OH)4 are reported. The main objective of the present study is the determination of critical shock pressures for partial and complete dehydration of serpentine under shock loading. It is pointed out that serpentine and serpentine-like layer silicates are the major water-bearing phases in carbonaceous chondrites. It appears that these minerals, and a poorly defined cometary contribution, were the most likely water-bearing phases in accreting planetesimals which led to the formation of the terrestrial planets. The obtained results imply that the process of impact induced devolatilization of volatile bearing minerals during accretion is likely to have occurred on earth. The findings lend support to the model of a terrestrial atmosphere/hydrosphere forming during the later stages of accretion of the earth.

Characterization of Cracking Mechanisms of Carbon Anodes Used in Aluminum Industry by Optical Microscopy and Tomography

NASA Astrophysics Data System (ADS)

Amrani, Salah; Kocaefe, Duygu; Kocaefe, Yasar; Bhattacharyay, Dipankar; Bouazara, Mohamed; Morais, Brigitte

2016-10-01

The objective of this work is to understand the different mechanisms of crack formation in dense anodes used in the aluminum industry. The first approach used is based on the qualitative characterization of the surface cracks and the depth of these cracks. The second approach, which constitutes a quantitative characterization, is carried out by determining the distribution of the crack width along its length as well as the percentage of the surface containing cracks. A qualitative analysis of crack formation was also carried out using 3D tomography. It was observed that mixing and forming conditions have a significant effect on crack formation in green anodes. The devolatilization of pitch during baking causes the formation and propagation of cracks in baked anodes in which large particles control the direction of crack propagation.

Filtering coal-derived oil through a filter media precoated with particles partially solubilized by said oil

DOEpatents

Rodgers, Billy R.; Edwards, Michael S.

1977-01-01

Solids such as char, ash, and refractory organic compounds are removed from coal-derived liquids from coal liquefaction processes by the pressure precoat filtration method using particles of 85-350 mesh material selected from the group of bituminous coal, anthracite coal, lignite, and devolatilized coals as precoat materials and as body feed to the unfiltered coal-derived liquid.

Causes of distal volcano-tectonic seismicity inferred from hydrothermal modeling

USGS Publications Warehouse

Coulon, Cecile A.; Hsieh, Paul A.; White, Randall A.; Lowenstern, Jacob B.; Ingebritsen, Steven E.

2017-01-01

Distal volcano-tectonic (dVT) seismicity typically precedes eruption at long-dormant volcanoes by days to years. Precursory dVT seismicity may reflect magma-induced fluid-pressure pulses that intersect critically stressed faults. We explored this hypothesis using an open-source magmatic-hydrothermal code that simulates multiphase fluid and heat transport over the temperature range 0 to 1200 °C. We calculated fluid-pressure changes caused by a small (0.04 km3) intrusion and explored the effects of flow geometry (channelized vs. radial flow), magma devolatilization rates (0–15 kg/s), and intrusion depths (5 and 7.5 km, above and below the brittle-ductile transition). Magma and host-rock permeabilities were key controlling parameters and we tested a wide range of permeability (k) and permeability anisotropies (kh/kv), including k constant, k(z), k(T), and k(z, T, P) distributions, examining a total of ~ 1600 realizations to explore the relevant parameter space. Propagation of potentially causal pressure changes (ΔP ≥ 0.1 bars) to the mean dVT location (6 km lateral distance, 6 km depth) was favored by channelized fluid flow, high devolatilization rates, and permeabilities similar to those found in geothermal reservoirs (k ~ 10− 16 to 10− 13 m2). For channelized flow, magma-induced thermal pressurization alone can generate cases of ∆ P ≥ 0.1 bars for all permeabilities in the range 10− 16 to 10− 13 m2, whereas in radial flow regimes thermal pressurization causes ∆ P < 0.1 bars for all permeabilities. Changes in distal fluid pressure occurred before proximal pressure changes given modest anisotropies (kh/kv ~ 10–100). Invoking k(z,T,P) and high, sustained devolatilization rates caused large dynamic fluctuations in k and P in the near-magma environment but had little effect on pressure changes at the distal dVT location. Intrusion below the brittle-ductile transition damps but does not prevent pressure transmission to the dVT site.

HIGH PRESSURE COAL COMBUSTION KINETICS PROJECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chris Guenther; Bill Rogers

2001-09-15

The HPCCK project was initiated with a kickoff meeting held on June 12, 2001 in Morgantown, WV, which was attended by all project participants. SRI's existing g-RCFR reactor was reconfigured to a SRT-RCFR geometry (Task 1.1). This new design is suitable for performing the NBFZ experiments of Task 1.2. It was decided that the SRT-RCFR apparatus could be modified and used for the HPBO experiments. The purchase, assembly, and testing of required instrumentation and hardware is nearly complete (Task 1.1 and 1.2). Initial samples of PBR coal have been shipped from FWC to SRI (Task 1.1). The ECT device formore » coal flow measurements used at FWC will not be used in the SRI apparatus and a screw type feeder has been suggested instead (Task 5.1). NEA has completed a upgrade of an existing Fluent simulator for SRI's RCFR to a version that is suitable for interpreting results from tests in the NBFZ configuration (Task 1.3) this upgrade includes finite-rate submodels for devolatilization, secondary volatiles pyrolysis, volatiles combustion, and char oxidation. Plans for an enhanced version of CBK have been discussed and development of this enhanced version has begun (Task 2.5). A developmental framework for implementing pressure and oxygen effects on ash formation in an ash formation model (Task 3.3) has begun.« less

Impact and collisional processes in the solar system

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.; Gazis, C.; Pepin, R.; Becker, R.; Cronin, R.; Tyburczy, J.; Tingle, T.; Duffy, T.; Rowan, L.

1991-01-01

As impact cratered terrains have been successively recognized on certain planets and planetary satellites, it has become clear that impact processes are important to the understanding of the accretion and evolution of all solid planets. The noble gases in the normalized atmospheric inventories of the planets and the normalized gas content of meteorites are grossly similar, but demonstrate differences from each other which are not understood. In order to study shock devolatilization of the candidate carrier phases which are principally thought to be carbonaceous or hydrocarbons in planetesimals, experiments were conducted on noble gase implantation in various carbons: carbon black, activated charcoal, graphite, and carbon glass. These were candidate starting materials for impact devolatilization experiments. Initial experiments were conducted on vitreous amorphous carbon samples which were synthesized under vapor saturated conditions using argon as the pressurizing medium. An amino acid and surface analysis by laser ionization analyses were performed on three samples of shocked Murchison meteorite. A first study was completed in which a series of shock loading experiments on a porous limestone and on a non-porous gabbro in one and three dimensions were performed. Also a series of recovery experiments were conducted in which shocked molten basalt a 1700 C is encapsulated in molybdenum containers and shock recovered from up to 6 GPa pressures.

Deciphering the dynamics of olivine nucleation and growth during antigorite breakdown

NASA Astrophysics Data System (ADS)

Dilissen, Nicole; Kahl, Wolf-Achim; Garrido, Carlos J.; López Sánchez-Vizcaíno, Vicente; Hidas, Károly

2016-04-01

Subduction zones are dynamic convergent plate boundaries associated with arc volcanism and earthquakes, which are believed to be controlled by fluids released during devolatilization reactions from the downgoing slab. The high-pressure breakdown of antigorite-serpentinite to prograde chlorite-harzburgite is considered to be the most significant source of water in subduction zones. The Cerro del Almirez ultramafic massif (Betic Cordillera, SE Spain) is a unique exhumed subduction terrane that preserves this dehydration reaction as a sharp front. A key to the understanding of the metamorphic conditions prevailing during serpentinite dehydration is to study the two prominent textures, granofels and spinifex-like chlorite harzburgite, which are the reaction products of antigorite breakdown. The textural study of these two types of Chl-harzburgite can provide insights into the kinetic of serpentinite dehydration reaction and the key factors controlling the overstepping of the reaction. Detailed mapping of textural variations in chlorite-harzburgite unveiled a network of granofels and spinifex-like lenses in the Almirez massif. In this work, we focus in the detailed textural variations across a well-exposed lens of spinifex-like chlorite-harzburgite, surrounded by granofels chlorite-harzburgite. This outcrop allowed us to make a very detailed oriented sampling (every 0.1-0.5 m across the 6 m thick lens) from the granofels into spinifex textures. The petrological study shows a developing transition of the olivine crystal shape, with premature mm-sized spinifex-like olivine crystals at the lens rims and well developed cm-sized spinifex-like grains in the core of the lens. The micro-CT study of oriented cores, together with EBSD study of thin sections from the same cores, allows the 3D reconstruction of olivine shapes and their lattice preferred orientation (LPO), constraining how olivine shapes and LPO differ from one texture to the other. This study provides valuable information on the kinetic of crystallization of olivine and how different textures formed in space and time, associated with the antigorite breakdown reaction.

Contact metamorphism of black shales: global carbon cycle and climate perturbations

NASA Astrophysics Data System (ADS)

Aarnes, I.; Svensen, H.; Polteau, S.; Connolly, J. A. D.; Planke, S.

2009-04-01

There is an increasing interest in improving the understanding of past climate changes, as it can lead to a better understanding of future challenges related to global warming and anthropogenic release of greenhouse gases. The formation of Large Igneous Provinces (LIPs) and sill intrusions in volcanic basins correlate with global warming events and mass extinctions, e.g. the Karoo Basin, South Africa (~183 Ma), the Møre and Vøring Basins offshore Norway (~55 Ma), and the Tunguska Basin, Siberia (~252 Ma). The proxy records from these events suggest that rapid release of large amounts of isotopically 13C-depleted greenhouse gases (CO2 and methane) to the atmosphere. Organic matter stored in sedimentary rocks (e.g. black shale) represents a major carbon source. Large volumes of greenhouse gases may form by contact metamorphism of organic-rich sediments around sill intrusions associated with LIPs. The organic-rich Ecca Group forms the base of the Karoo sedimentary succession and contains thousands of degassing pipe structures rooted in contact aureoles around sill intrusions. Numerical and analogue modelling show that these piercement structures form during violent eruptions releasing the overpressure driven by dehydration and devolatilization metamorphic reactions. In this study we evaluate the aureole processes numerically in order to constrain the amount of gases formed in contact aureoles around sill intrusions, and the isotopic composition of those gases. The total organic carbon (TOC) in the shale and the intrusion thickness are the most important parameters controlling the amount of carbon gas that can trigger pipe formation and release into the atmosphere. . We model thermal cracking using a general kinetic approach, while dehydration reactions are modeled under the assumption of thermodynamic equilibrium. The theoretical approach is tested against borehole data from the Karoo Basin in South Africa (geochemical analyses, Rock-Eval pyrolysis, TOC, vitrinite reflectance and stable isotopes). Decreasing TOC content and increasing vitrinite reflectance with decreasing distance to the intrusive contact are signatures of thermogenic hydrocarbon formation. During high temperature metamorphism, formation of carbon gases is preferred over liquid hydrocarbons. However, only limited isotopic fractionation is occurring in the released carbon gases during increasing temperature. Increasing veining towards the contact of a 10 meter sill suggests that hydrocarbon formation in organic-rich aureoles leads to pressure buildup and fracturing of the aureole, even with small volumes. Our numerical model also shows that sill thicknesses in the order of 100 m are necessary to produce the pressure buildup in the contact aureole and subsequent venting. In addition, mineral dehydration and thermal stresses contribute to pore fluid pressure increase. We use our numerical model to predict the amount of fluids produced as response to thin (~10 meter) and thick (~100 meter) sills. The model provides us with important estimates of rate and duration of gas formation. The time-scale of subsurface gas formation is well within the time scale indicated by the proxy data. Results from isotope compositions demonstrate that the 2.8t/m2 of organic carbon escapes the contact aureole during devolatilization processes involving the generation of light carbon gases. The calculated isotopic composition of the carbon released is similar whether using the batch devolatilization or the Rayleigh distillation model, and ranges from the background values to 1-2 permil lighter values with decreasing distance from the contact. The extrapolation of our results to the portion of the sedimentary basin intruded by magma suggests that contact metamorphism of organic-rich sediments triggered a potential release of between 2000 to 10000 Gt of isotopically light carbon gas to the atmosphere. In conclusion, the amount and composition of methane that can be produced and vented from contact aureoles in the Karoo Basin during the Toarcian is within the same order of magnitude as required to explain global carbon isotope excursion and hence global warming.

Experimental investigation of wood combustion in a fixed bed with hot air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markovic, Miladin, E-mail: m.markovic@utwente.nl; Bramer, Eddy A.; Brem, Gerrit

Highlights: • Upward combustion is a new combustion concept with ignition by hot primary air. • Upward combustion has three stages: short drying, rapid devolatilization and char combustion. • Variation of fuel moisture and inert content have little influence on the combustion. • Experimental comparison between conventional and upward combustion is presented. - Abstract: Waste combustion on a grate with energy recovery is an important pillar of municipal solid waste (MSW) management in the Netherlands. In MSW incinerators fresh waste stacked on a grate enters the combustion chamber, heats up by radiation from the flame above the layer and ignitionmore » occurs. Typically, the reaction zone starts at the top of the waste layer and propagates downwards, producing heat for drying and devolatilization of the fresh waste below it until the ignition front reaches the grate. The control of this process is mainly based on empiricism. MSW is a highly inhomogeneous fuel with continuous fluctuating moisture content, heating value and chemical composition. The resulting process fluctuations may cause process control difficulties, fouling and corrosion issues, extra maintenance, and unplanned stops. In the new concept the fuel layer is ignited by means of preheated air (T > 220 °C) from below without any external ignition source. As a result a combustion front will be formed close to the grate and will propagate upwards. That is why this approach is denoted by upward combustion. Experimental research has been carried out in a batch reactor with height of 4.55 m, an inner diameter of 200 mm and a fuel layer height up to 1 m. Due to a high quality two-layer insulation adiabatic conditions can be assumed. The primary air can be preheated up to 350 °C, and the secondary air is distributed via nozzles above the waste layer. During the experiments, temperatures along the height of the reactor, gas composition and total weight decrease are continuously monitored. The influence of the primary air speed, fuel moisture and inert content on the combustion characteristics (ignition rate, combustion rate, ignition front speed and temperature of the reaction zone) is evaluated. The upward combustion concept decouples the drying, devolatilization and burnout phase. In this way the moisture and inert content of the waste have almost no influence on the combustion process. In this paper an experimental comparison between conventional and reversed combustion is presented.« less

Numerical and experimental studies on effects of moisture content on combustion characteristics of simulated municipal solid wastes in a fixed bed.

PubMed

Sun, Rui; Ismail, Tamer M; Ren, Xiaohan; Abd El-Salam, M

2015-05-01

In order to reveal the features of the combustion process in the porous bed of a waste incinerator, a two-dimensional unsteady state model and experimental study were employed to investigate the combustion process in a fixed bed of municipal solid waste (MSW) on the combustion process in a fixed bed reactor. Conservation equations of the waste bed were implemented to describe the incineration process. The gas phase turbulence was modeled using the k-ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. The rate of moisture evaporation, devolatilization rate, and char burnout was calculated according to the waste property characters. The simulation results were then compared with experimental data for different moisture content of MSW, which shows that the incineration process of waste in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data. Due to the high moisture content of fuel, moisture evaporation consumes a vast amount of heat, and the evaporation takes up most of the combustion time (about 2/3 of the whole combustion process). The whole bed combustion process reduces greatly as MSW moisture content increases. The experimental and simulation results provide direction for design and optimization of the fixed bed of MSW. Copyright © 2015 Elsevier Ltd. All rights reserved.

Impact Cratering Calculations

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.

2001-01-01

This research is computational /theoretical and complements the Caltech experimental program. We have developed an understanding of the basic physical processes and produced computational models and implemented these into Eulerian and Lagrangian finite element codes. The key issues we have addressed include the conditions required for: faulting (strain localization), elastic moduli weakening, dynamic weakening (layering elastic instabilities and fluidization), bulking (creation of porosity at zero pressure) and compaction of pores, frictional melting (creation of pseudotachylytes), partial and selective devolatilization of materials (e.g. CaCO3, water/ice mixtures), and debris flows.

H2O and CO2 devolatilization in subduction zones: implications for the global water and carbon cycles (Invited)

NASA Astrophysics Data System (ADS)

van Keken, P. E.; Hacker, B. R.; Syracuse, E. M.; Abers, G. A.

2010-12-01

Subduction of sediments and altered oceanic crust functions as a major carbon sink. Upon subduction the carbon may be released by progressive metamorphic reactions, which can be strongly enhanced by free fluids. Quantification of the CO2 release from subducting slabs is important to determine the provenance of CO2 that is released by the volcanic arc and to constrain the flux of carbon to the deeper mantle. In recent work we used a global set of high resolution thermal models of subduction zones to predict the flux of H2O from the subducting slab (van Keken, Hacker, Syracuse, Abers, Subduction factory 4: Depth-dependent flux of H2O from subducting slabs worldwide, J. Geophys. Res., under review) which provides a new estimate of the dehydration efficiency of the global subducting system. It was found that mineralogically bound water can pass efficiently through old and fast subduction zones (such as in the western Pacific) but that warm subduction zones (such as Cascadia) see nearly complete dehydration of the subducting slab. The top of the slab is sufficiently hot in all subduction zones that the upper crust dehydrates significantly. The degree and depth of dehydration is highly diverse and strongly depends on (p,T) and bulk rock composition. On average about one third of subducted H2O reaches 240 km depth, carried principally and roughly equally in the gabbro and peridotite sections. The present-day global flux of H2O to the deep mantle translates to an addition of about one ocean mass over the age of the Earth. We extend the slab devolatilization work to carbon by providing an update to Gorman et al. (Geochem. Geophys. Geosyst, 2006), who quantified the effects of free fluids on CO2 release. The thermal conditions were based on three end-member subduction zones with linear interpolation to provide a global CO2 flux. We use the new high resolution and global set of models to provide higher resolution predictions for the provenance and pathways of CO2 release to the mantle wedge and a more robust prediction of the global CO2 flux in subduction.

Elemental Mercury Diffusion Processes and Concentration at the Lunar Poles

NASA Technical Reports Server (NTRS)

Moxley, Frederick; Killen, Rosemary M.; Hurley, Dana M.

2011-01-01

In 2009, the Lyman Alpha Mapping Project (LAMP) spectrograph onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft made the first detection of element mercury (Hg) vapor in the lunar exosphere after the Lunar Crater Observing and Sensing Satellite (LCROSS) Centaur rocket impacted into the Cabeus crater in the southern polar region of the Moon. The lunar regolith core samples from the Apollo missions determined that Hg had a devolatilized pattern with a concentration gradient increasing with depth, in addition to a layered pattern suggesting multiple episodes of burial and volatile loss. Hg migration on the lunar surface resulted in cold trapping at the poles. We have modeled the rate at which indigenous Hg is lost from the regolith through diffusion out of lunar grains. We secondly modeled the migration of Hg vapor in the exosphere and estimated the rate of cold-trapping at the poles using a Monte Carlo technique. The Hg vapor may be lost from the exosphere via ionization, Jeans escape, or re-impact into the surface causing reabsorption.

Volatile transfer and recycling at convergent margins: Mass-balance and insights from high-P/T metamorphic rocks

NASA Astrophysics Data System (ADS)

Bebout, Gray E.

The efficiency with which volatiles are deeply subducted is governed by devolatilization histories and the geometries and mechanisms of fluid transport deep in subduction zones. Metamorphism along the forearc slab-mantle interface may prevent the deep subduction of many volatile components (e.g., H2O, Cs, B, N, perhaps As, Sb, and U) and result in their transport in fluids toward shallower reservoirs. The release, by devolatilization, and transport of such components toward the seafloor or into the forearc mantle wedge, could in part explain the imbalances between the estimated amounts of subducted volatiles and the amounts returned to Earth's surface. The proportion of the initially subducted volatile component that is retained in rocks subducted to depths greater than those beneath magmatic arcs (>100 km) is largely unknown, complicating assessments of deep mantle volatile budgets. Isotopic and trace element data and volatile contents for the Catalina Schist, the Franciscan Complex, and eclogite-facies complexes in the Alps (and elsewhere) provide insight into the nature and magnitude of fluid production and transport deep in subduction zones and into the possible effects of metamorphism on the compositions of subducting rocks. Compatibilities of the compositions of the subduction-related rocks and fluids with the isotopic and trace element compositions of various mantle-derived materials (igneous rocks, xenoliths, serpentinite seamounts) indicate the potential to trace the recycling of rock and fluid reservoirs chemically and isotopically fractionated during subduction-zone metamorphism.

Carbon dioxide released from subduction zones by fluid-mediated reactions

NASA Astrophysics Data System (ADS)

Ague, Jay J.; Nicolescu, Stefan

2014-05-01

The balance between the subduction of carbonate mineral-bearing rocks into Earth's mantle and the return of CO2 to the atmosphere by volcanic and metamorphic degassing is critical to the carbon cycle. Carbon is thought to be released from subducted rocks mostly by simple devolatilization reactions. However, these reactions will also retain large amounts of carbon within the subducting slab and have difficulty in accounting for the mass of CO2 emitted from volcanic arcs. Carbon release may therefore occur via fluid-induced dissolution of calcium carbonate. Here we use carbonate δ18O and δ13C systematics, combined with analyses of rock and fluid inclusion mineralogy and geochemistry, to investigate the alteration of the exhumed Eocene Cycladic subduction complex on the Syros and Tinos islands, Greece. We find that in marble rocks adjacent to two fluid conduits that were active during subduction, the abundance of calcium carbonate drastically decreases approaching the conduits, whereas silicate minerals increase. Up to 60-90% of the CO2 was released from the rocks--far greater than expected via simple devolatilization reactions. The δ18O of the carbonate minerals is 5-10 lighter than is typical for metamorphosed carbonate rocks, implying that isotopically light oxygen was transported by fluid infiltration from the surroundings. We suggest that fluid-mediated carbonate mineral removal, accompanied by silicate mineral precipitation, provides a mechanism for the release of enormous amounts of CO2 from subduction zones.

Freeboard reactions in fluidized coal combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walsh, P.M.; Dutta, A.; Beer, J.M.

1984-05-11

The objective of this study was to determine the contribution of freeboard combustion to overall fixed carbon conversion during atmospheric pressure fluidized bed combustion of Kentucky No. 9 high volatile bituminous coal. The progress of the O/sub 2//char reaction in the freeboard was inferred from O/sub 2/ profiles determined by gas sampling. The rates of O/sub 2/ consumption were in good agreement with the O/sub 2//char rate expression of Sergeant and Smith (1973), except at the lowest temperature investigated (964 K). The discrepancy in this case might be due to catalysis of the O/sub 2//char reaction by lime, since thismore » was the first run of the series. Extrapolation of the O/sub 2/ profile to the bed surface using the rate expression of Sergeant and Smith showed that approximately all of the fixed carbon conversion could be accounted for by freeboard combustion. A simple model is proposed in which devolatilization, fragmentation, attrition, and volatile combustion are limited to the bed; with combustion of the finely ground char occurring only in the freeboard. This model predicts O/sub 2/ at the combustor outlet within 60% of the measured values, except in the low temperature/high lime case.« less

Hydrogen isotope investigation of amphibole and biotite phenocrysts in silicic magmas erupted at Lassen Volcanic Center, California

USGS Publications Warehouse

Underwood, S.J.; Feeley, T.C.; Clynne, M.A.

2012-01-01

Hydrogen isotope ratio, water content and Fe3 +/Fe2 + in coexisting amphibole and biotite phenocrysts in volcanic rocks can provide insight into shallow pre- and syn-eruptive magmatic processes such as vesiculation, and lava drainback with mixing into less devolatilized magma that erupts later in a volcanic sequence. We studied four ~ 35 ka and younger eruption sequences (i.e. Kings Creek, Lassen Peak, Chaos Crags, and 1915) at the Lassen Volcanic Center (LVC), California, where intrusion of crystal-rich silicic magma mushes by mafic magmas is inferred from the varying abundances of mafic magmatic inclusions (MMIs) in the silicic volcanic rocks. Types and relative proportions of reacted and unreacted hydrous phenocryst populations are evaluated with accompanying chemical and H isotope changes. Biotite phenocrysts were more susceptible to rehydration in older vesicular glassy volcanic rocks than coexisting amphibole phenocrysts. Biotite and magnesiohornblende phenocrysts toward the core of the Lassen Peak dome are extensively dehydroxylated and reacted from prolonged exposure to high temperature, low pressure, and higher fO2 conditions from post-emplacement cooling. In silicic volcanic rocks not affected by alteration, biotite phenocrysts are often relatively more dehydroxylated than are magnesiohornblende phenocrysts of similar size; this is likely due to the ca 10 times larger overall bulk H diffusion coefficient in biotite. A simplified model of dehydrogenation in hydrous phenocrysts above reaction closure temperature suggests that eruption and quench of magma ascended to the surface in a few hours is too short a time for substantial H loss from amphibole. In contrast, slowly ascended magma can have extremely dehydrogenated and possibly dehydrated biotite, relatively less dehydrogenated magnesiohornblende and reaction rims on both phases. Eruptive products containing the highest proportions of mottled dehydrogenated crystals could indicate that within a few days prior to eruption, degassed vesiculated magma or lava had drained back down the volcanic conduit and mixed with less devolatilized magma. The vesiculated magma contained hydrous phenocrysts with lattice damage, which locally raised the effective H diffusion coefficient by ca 10–100 × and resulted in increased mineral dehydrogenation. Remobilization of dacite magma mush by relatively more reduced mafic magma appears to have generated further fO2 variations in May 1915 as oxidized magma from shallow levels circulated to depths where dehydrogenation of hydrous phenocrysts began. The δDMagmatic H2O expressed in LVC acid hot springs is likely a mixture derived from devolatilized ascending mafic magmas and crystallizing silicic magma mush.

Combustion studies of coal derived solid fuels by thermogravimetric analysis. III. Correlation between burnout temperature and carbon combustion efficiency

USGS Publications Warehouse

Rostam-Abadi, M.; DeBarr, J.A.; Chen, W.T.

1990-01-01

Burning profiles of 35-53 ??m size fractions of an Illinois coal and three partially devolatilized coals prepared from the original coal were obtained using a thermogravimetric analyzer. The burning profile burnout temperatures were higher for lower volatile fuels and correlated well with carbon combustion efficiencies of the fuels when burned in a laboratory-scale laminar flow reactor. Fuels with higher burnout temperatures had lower carbon combustion efficiencies under various time-temperature conditions in the laboratory-scale reactor. ?? 1990.

Ultra-Fast Laser Desorption/Laser Ionization Mass Spectrometry for the Organic Analysis of Stardust Sample Return

NASA Technical Reports Server (NTRS)

Clemett, Simon J.; McKay, David S.

2005-01-01

The STARDUST sample return capsule is anticipated to provide 500-1000 cometary particles 15 m in size. These were collected during the 340 km flyby of Comet P/Wild-2 and impacted the aerogel collection medium at a relative velocity of approx. 6.1 /kms. Hypervelocity impact studies suggest that some fraction of the original organic inventory of collected particles ought to remain intact, although there is likely to be a significant amount of devolatilization and disassociation of the lower mass organic fraction.

Conversion of raw carbonaceous fuels

DOEpatents

Cooper, John F [Oakland, CA

2007-08-07

Three configurations for an electrochemical cell are utilized to generate electric power from the reaction of oxygen or air with porous plates or particulates of carbon, arranged such that waste heat from the electrochemical cells is allowed to flow upwards through a storage chamber or port containing raw carbonaceous fuel. These configurations allow combining the separate processes of devolatilization, pyrolysis and electrochemical conversion of carbon to electric power into a single unit process, fed with raw fuel and exhausting high BTU gases, electric power, and substantially pure CO.sub.2 during operation.

Simulation of fluidized bed coal combustors

NASA Technical Reports Server (NTRS)

Rajan, R.

1979-01-01

The many deficiencies of previous work on simulation of fluidized bed combustion (FBC) processes are presented. An attempt is made to reduce these deficiencies, and to formulate a comprehensive FBC model taking into account the following elements: (1) devolatilization of coal and the subsequent combustion of volatiles and residual char; (2) sulfur dioxide capture by limestone; (3) NOx release and reduction of NOx by char; (4) attrition and elutriation of char and limestone; (5) bubble hydrodynamics; (6) solids mixing; (7) heat transfer between gas and solid, and solid and heat exchange surfaces; and (8) freeboard reactions.

Copper(II)-mediated thermolysis of alginates: a model kinetic study on the influence of metal ions in the thermochemical processing of macroalgae

PubMed Central

Rowbotham, J. S.; Dyer, P. W.; Greenwell, H. C.; Selby, D.; Theodorou, M. K.

2013-01-01

Thermochemical processing methods such as pyrolysis are of growing interest as a means of converting biomass into fuels and commodity chemicals in a sustainable manner. Macroalgae, or seaweed, represent a novel class of feedstock for pyrolysis that, owing to the nature of the environments in which they grow coupled with their biochemistry, naturally possess high metal contents. Although the impact of metals upon the pyrolysis of terrestrial biomass is well documented, their influence on the thermochemical conversion of marine-derived feeds is largely unknown. Furthermore, these effects are inherently difficult to study, owing to the heterogeneous character of natural seaweed samples. The work described in this paper uses copper(II) alginate, together with alginic acid and sodium alginate as model compounds for exploring the effects of metals upon macroalgae thermolysis. A thermogravimetric analysis–Fourier transform infrared spectroscopic study revealed that, unusually, Cu2+ ions promote the onset of pyrolysis in the alginate polymer, with copper(II) alginate initiating rapid devolatilization at 143°C, 14°C lower than alginic acid and 61°C below the equivalent point for sodium alginate. Moreover, this effect was mirrored in a sample of wild Laminaria digitata that had been doped with Cu2+ ions prior to pyrolysis, thus validating the use of alginates as model compounds with which to study the thermolysis of macroalgae. These observations indicate the varying impact of different metal species on thermochemical behaviour of seaweeds and offer an insight into the pyrolysis of brown macroalgae used in phytoremediation of metal-containing waste streams. PMID:24427515

Revised users manual, Pulverized Coal Gasification or Combustion: 2-dimensional (87-PCGC-2): Final report, Volume 2. [87-PCGC-2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, P.J.; Smoot, L.D.; Brewster, B.S.

1987-12-01

A two-dimensional, steady-state model for describing a variety of reactive and non-reactive flows, including pulverized coal combustion and gasification, is presented. Recent code revisions and additions are described. The model, referred to as 87-PCGC-2, is applicable to cylindrical axi-symmetric systems. Turbulence is accounted for in both the fluid mechanics equations and the combustion scheme. Radiation from gases, walls, and particles is taken into account using either a flux method or discrete ordinates method. The particle phase is modeled in a Lagrangian framework, such that mean paths of particle groups are followed. Several multi-step coal devolatilization schemes are included along withmore » a heterogeneous reaction scheme that allows for both diffusion and chemical reaction. Major gas-phase reactions are modeled assuming local instantaneous equilibrium, and thus the reaction rates are limited by the turbulent rate mixing. A NO/sub x/ finite rate chemistry submodel is included which integrates chemical kinetics and the statistics of the turbulence. The gas phase is described by elliptic partial differential equations that are solved by an iterative line-by-line technique. Under-relaxation is used to achieve numerical stability. The generalized nature of the model allows for calculation of isothermal fluid mechanicsgaseous combustion, droplet combustion, particulate combustion and various mixtures of the above, including combustion of coal-water and coal-oil slurries. Both combustion and gasification environments are permissible. User information and theory are presented, along with sample problems. 106 refs.« less

Lithospheric processes that enhance melting at rifts

NASA Astrophysics Data System (ADS)

Elkins-Tanton, L. T.; Furman, T.

2008-12-01

Continental rifts are commonly sites for mantle melting, whether in the form of ridge melting to create new oceanic crust, or as the locus of flood basalt activity, or in the long initial period of rifting before lavas evolve fully into MORBs. The high topography in the lithosphere-asthenosphere boundary under a rift creates mantle upwelling and adiabatic melting even in the absence of a plume. This geometry itself, however, is conducive to lithospheric instability on the sides of the rifts. Unstable lithosphere may founder into the mantle, producing more complex aesthenospheric convective patterns and additional opportunities to produce melt. Lithospheric instabilities can produce additional adiabatic melting in convection produced as they sink, and they may also devolatilize as they sink, introducing the possibility of flux melting to the rift environment. We call this process upside-down melting, since devolatilization and melting proceed as the foundering lithosphere sinks, rather than while rising, as in the more familiar adiabatic decompression melting. Both adiabatic melting and flux melting would take place along the edges of the rift and may even move magmatism outside the rift, as has been seen in Ethiopia. In volcanism postdating the flood basalts on and adjacent to the Ethiopian Plateau there is evidence for both lithospheric thinning and volatile enrichment in the magmas, potentially consistent with the upside-down melting model. Here we present a physical model for the conjunction of adiabatic decompression melting to produce new oceanic crust in the rift, while lithospheric gravitational instabilities drive both adiabatic and flux melting at its margins.

The dilemma of the Jiaodong gold deposits: Are they unique?

USGS Publications Warehouse

Goldfarb, Richard J.; Santosh, M.

2013-01-01

The ca. 126–120 Ma Au deposits of the Jiaodong Peninsula, eastern China, define the country's largest gold province with an overall endowment estimated as >3000 t Au. The vein and disseminated ores are hosted by NE- to NNE-trending brittle normal faults that parallel the margins of ca. 165–150 Ma, deeply emplaced, lower crustal melt granites. The deposits are sited along the faults for many tens of kilometers and the larger orebodies are associated with dilatational jogs. Country rocks to the granites are Precambrian high-grade metamorphic rocks located on both sides of a Triassic suture between the North and South China blocks. During early Mesozoic convergent deformation, the ore-hosting structures developed as ductile thrust faults that were subsequently reactivated during Early Cretaceous “Yanshanian” intracontinental extensional deformation and associated gold formation.Classification of the gold deposits remains problematic. Many features resemble those typical of orogenic Au including the linear structural distribution of the deposits, mineralization style, ore and alteration assemblages, and ore fluid chemistry. However, Phanerozoic orogenic Au deposits are formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens. The Jiaodong deposits, in contrast, formed within two Precambrian blocks approximately 2 billion years after devolatilization of the country rocks, and thus require a model that involves alternative fluid and metal sources for the ores. A widespread suite of ca. 130–123 Ma granodiorites overlaps temporally with the ores, but shows a poor spatial association with the deposits. Furthermore, the deposit distribution and mineralization style is atypical of ores formed from nearby magmas. The ore concentration requires fluid focusing during some type of sub-crustal thermal event, which could be broadly related to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific plate subduction, and seismicity along the continental-scale Tan-Lu fault. Possible ore genesis scenarios include those where ore fluids were produced directly by the metamorphism of oceanic lithosphere and overlying sediment on the subducting paleo-Pacific slab, or by devolatilization of an enriched mantle wedge above the slab. Both the sulfur and gold could be sourced from either the oceanic sediments or the serpentinized mantle. A better understanding of the architecture of the paleo-Pacific slab during Early Cretaceous below the eastern margin of China is essential to determination of the validity of possible models.

Assessment of shock effects on amphibole water contents and hydrogen isotope compositions: 1. Amphibolite experiments

NASA Astrophysics Data System (ADS)

Minitti, Michelle E.; Rutherford, Malcolm J.; Taylor, Bruce E.; Dyar, M. Darby; Schultz, Peter H.

2008-02-01

Kaersutitic amphiboles found within a subset of the Martian meteorites have low water contents and variably heavy hydrogen isotope compositions. In order to assess if impact shock-induced devolatilization and hydrogen isotope fractionation were determining factors in these water and isotopic characteristics of the Martian kaersutites, we conducted impact shock experiments on samples of Gore Mountain amphibolite in the Ames Vertical Gun Range (AVGR). A parallel shock experiment conducted on an anorthosite sample indicated that contamination of shocked samples by the AVGR hydrogen propellant was unlikely. Petrographic study of the experimental amphibolite shock products indicates that only ˜ 10% of the shock products experienced levels of damage equivalent to those found in the most highly shocked kaersutite-bearing Martian meteorites (30-35 GPa). Ion microprobe studies of highly shocked hornblende from the amphibolite exhibited elevated water contents (ΔH 2O ˜ 0.1 wt.%) and enriched hydrogen isotope compositions (Δ D ˜ + 10‰) relative to unshocked hornblende. Water and hydrogen isotope analyses of tens of milligrams of unshocked, moderately shocked, and highly shocked hornblende samples by vacuum extraction/uranium reduction and isotope ratio mass spectrometry (IRMS), respectively, are largely consistent with analyses of single grains from the ion microprobe. The mechanisms thought to have produced the excess water in most of the shocked hornblendes are shock-induced reduction of hornblende Fe and/or irreversible adsorption of hydrogen. Addition of the isotopically enriched Martian atmosphere to the Martian meteorite kaersutites via these mechanisms could explain their enriched and variable isotopic compositions. Alternatively, regrouping the water extraction and IRMS analyses on the basis of isotopic composition reveals a small, but consistent, degree of impact-induced devolatilization (˜ 0.1 wt.% H 2O) and H isotope enrichment (Δ D ˜ + 10‰). Extrapolating the shock signature of the regrouped data to grains that experienced Martian meteorite-like shock pressures suggests that shock-induced water losses and hydrogen isotope enrichments could approach 1 wt.% H 2O and Δ D = + 100‰, respectively. If these values are valid, then impact shock effects could explain a substantial fraction of the low water contents and variable hydrogen isotope compositions of the Martian meteorite kaersutites.

Experimental Shock Transformation of Gypsum to Anhydrite: A New Low Pressure Regime Shock Indicator

NASA Technical Reports Server (NTRS)

Bell, Mary S.; Zolensky, Michael E.

2011-01-01

The shock behavior of gypsum is important in understanding the Cretaceous/Paleogene event and other terrestrial impacts that contain evaporite sediments in their targets (e.g., Mars Exploration Rover Spirit detected sulfate at Gusev crater, [1]). Most interest focuses on issues of devolatilization to quantify the production of SO2 to better understand its role in generating a temporary atmosphere and its effects on climate and biota [2,3]. Kondo and Ahrens [4] measured induced radiation emitted from single crystal gypsum shocked to 30 and 40 GPa. They observed greybody emission spectra corresponding to temperatures in the range of 3,000 to 4,000 K that are a factor of 2 to 10 times greater than calculated pressure-density energy equation of state temperatures (Hugoniot) and are high enough to melt gypsum. Chen et al. [5] reported results of shock experiments on anhydrite, gypsum, and mixtures of these phases with silica. Their observations indicated little or no devolatilization of anhydrite shocked to 42 GPa and that the fraction of sulfur, by mass, that degassed is approx.10(exp -2) of theoretical prediction. In another report of shock experiments on calcite, anhydrite, and gypsum, Badjukov et al. [6] observed only intensive plastic deformation in anhydrite shock loaded at 63 GPa, and gypsum converted to anhydrite when shock loaded at 56 GPa but have not experimentally shocked gypsum in a step-wise manner to constrain possible incipient transformation effects. Schmitt and Hornemann [7] shock loaded anhydrite and quartz to a peak pressure of 60 GPa and report the platy anhydrite grains were completely pseudomorphed by small crystallized anhydrite grains. However, no evidence of interaction between the two phases could be observed and they suggested that recrystallization of anhydrite grains is the result of a solid-state transformation. They concluded that significant decomposition of anhydrite requires shock pressures higher than 60 GPa. Gupta et al. [8] reanalyzed the calcite and anhydrite shock wave experiments of Yang [9] using improved equations of state of porous materials and vaporized products. They determined the pressures for incipient and complete vaporization to be 32.5 and 122 GPa for anhydrite GPa which is a factor of 2 to 3 lower than reported earlier by Yang [9]. These studies are not in agreement regarding the onset of sulfate decomposition and documentation of shock effects in gypsum is incomplete.

[Enzyme kinetic glucose determination by the glucose dehydrogenase method. Enzyme kinetic substrate determination using competitive inhibitors, II (author's transl)].

PubMed

Müller-Matthesius, R

1975-05-01

The sensitivity of enzyme kinetic substrate determinations can be improved with the aid of competitive inhibitors. As an example, the determination of glucose dehydrogenase in the presence of potassium thiocyanate is described. The method has the advantage of rapid operation with satisfactory precision.

Coal desulfurization by chlorinolysis production and combustion test evaluation of product coals

NASA Technical Reports Server (NTRS)

Kalvinskas, J. J.; Daly, D.

1982-01-01

Laboratory-scale screening tests were carried out on coal from Harrison County, Ohio to establish chlorination and hydrodesulfurization conditions for the batch reactor production of chlorinolysis and chlorinolysis-hydrodesulfurized coals. In addition, three bituminous coals, were treated on the lab scale by the chlorinolysis process to provide 39 to 62% desulfurization. Two bituminous coals and one subbituminous coal were then produced in 11 to 15 pound lots as chlorinolysis and hydrodesulfurized coals. The chlorinolysis coals had a desulfurization of 29-69%, reductions in voltatiles and hydrogen. Hydrodesulfurization provided a much greater desulfurization (56-86%), reductions in volatiles and hydrogen. The three coals were combustion tested in the Penn State ""plane flame furnace'' to determine ignition and burning characteristics. All three coals burned well to completion as: raw coals, chlorinolysis processed coals, and hydrodesulfurized coals. The hydrodesulfurized coals experienced greater ignition delays and reduced burning rates than the other coals because of the reduced volatile content. It is thought that the increased open pore volume in the desulfurized-devolatilized coals compensates in part for the decreased volatiles effect on ignition and burning.

Two-stage fixed-bed gasifier with selectable middle gas off-take point

DOEpatents

Strickland, Larry D.; Bissett, Larry A.

1992-01-01

A two-stage fixed bed coal gasifier wherein an annular region is in registry with a gasification zone underlying a devolatilization zone for extracting a side stream of high temperature substantially tar-free gas from the gasifier. A vertically displaceable skirt means is positioned within the gasifier to define the lower portion of the annular region so that vertical displacement of the skirt means positions the inlet into the annular region in a selected location within or in close proximity to the gasification zone for providing a positive control over the composition of the side stream gas.

Comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open-system pyrolysis

USGS Publications Warehouse

Lewan, M.D.; Ruble, T.E.

2002-01-01

This study compares kinetic parameters determined by open-system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types. Kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated, but also in the derivation of the kinetic parameters (i.e., isothermal linear regression and non-isothermal nonlinear regression). Results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open-system pyrolysis. Hydrous-pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the organic-sulfur content of the original kerogen. Conversely, open-system kinetic parameters determine broad oil windows that show no significant differences with kerogen types or their organic-sulfur contents. Comparisons of the kinetic parameters in a hypothetical thermal-burial history (2.5 ??C/my) show open-system kinetic parameters significantly underestimate the extent and timing of oil generation for Type-US kerogen and significantly overestimate the extent and timing of petroleum formation for Type-I kerogen compared to hydrous pyrolysis kinetic parameters. These hypothetical differences determined by the kinetic parameters are supported by natural thermal-burial histories for the Naokelekan source rock (Type-IIS kerogen) in the Zagros basin of Iraq and for the Green River Formation (Type-I kerogen) in the Uinta basin of Utah. Differences in extent and timing of oil generation determined by open-system pyrolysis and hydrous pyrolysis can be attributed to the former not adequately simulating natural oil generation conditions, products, and mechanisms.

Numerical and experimental studies on effects of moisture content on combustion characteristics of simulated municipal solid wastes in a fixed bed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Rui, E-mail: Sunsr@hit.edu.cn; Ismail, Tamer M., E-mail: temoil@aucegypt.edu; Ren, Xiaohan

Highlights: • The effects of moisture content on the burning process of MSW are investigated. • A two-dimensional mathematical model was built to simulate the combustion process. • Temperature distributions, process rates, gas species were measured and simulated. • The The conversion ratio of C/CO and N/NO in MSW are inverse to moisture content. - Abstract: In order to reveal the features of the combustion process in the porous bed of a waste incinerator, a two-dimensional unsteady state model and experimental study were employed to investigate the combustion process in a fixed bed of municipal solid waste (MSW) on themore » combustion process in a fixed bed reactor. Conservation equations of the waste bed were implemented to describe the incineration process. The gas phase turbulence was modeled using the k–ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. The rate of moisture evaporation, devolatilization rate, and char burnout was calculated according to the waste property characters. The simulation results were then compared with experimental data for different moisture content of MSW, which shows that the incineration process of waste in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data. Due to the high moisture content of fuel, moisture evaporation consumes a vast amount of heat, and the evaporation takes up most of the combustion time (about 2/3 of the whole combustion process). The whole bed combustion process reduces greatly as MSW moisture content increases. The experimental and simulation results provide direction for design and optimization of the fixed bed of MSW.« less

Effect of H2O on the NO emission characteristics of pulverized coal during oxy-fuel combustion.

PubMed

Lei, Ming; Sun, Cen; Zou, Chan; Mi, Hang; Wang, Chunbo

2018-04-01

The NO emission characteristics of Datong bituminous coal and Yangquan anthracite in O 2 /H 2 O/CO 2 atmospheres were investigated by using a fixed-bed reactor system, and the emission characteristics were compared with the experimental results from O 2 /N 2 and O 2 /CO 2 atmospheres, especially at low O 2 concentrations and high temperatures. The results showed that NO emissions of pulverized coal in O 2 /CO 2 environments were less than those in the O 2 /N 2 environments, regardless of the O 2 concentration and the furnace temperature. Adding H 2 O decreased the possibility of reactions between the reductive groups (NH) and the oxygen radical during devolatilization, which led to a decrease in NO emissions at 1000 °C. However, as the furnace temperature increased, "additional" nitrogen precursors (HCN and NH 3 ) generated by enhanced char-H 2 O gasification were quickly oxidized to generate a large amount of NO during char oxidation that exceeded the amount of NO reduced by NH during devolatilization. Thus, the NO emissions in O 2 /CO 2 /H 2 O atmosphere were higher than those in O 2 /CO 2 atmosphere at a low O 2 concentration. However, as the O 2 concentration increased, the NO emissions in O 2 /CO 2 /H 2 O atmosphere became lower than those in O 2 /CO 2 atmosphere because the effect of H 2 O gasification became weaker. The NO emissions of Yangquan anthracite (YQ) were higher than those of DT, but the changing trend of YQ was similar to that of DT.

Intra-slab COH fluid fluxes evidenced by fluid-mediated decarbonation of lawsonite eclogite-facies altered oceanic metabasalts

NASA Astrophysics Data System (ADS)

Vitale Brovarone, Alberto; Chu, Xu; Martin, Laure; Ague, Jay J.; Monié, Patrick; Groppo, Chiara; Martinez, Isabelle; Chaduteau, Carine

2018-04-01

The interplay between the processes controlling the mobility of H2O and C-bearing species during subduction zone metamorphism exerts a critical control on plate tectonics and global volatile recycling. Here we present the first study on fresh, carbonate-bearing, lawsonite eclogite-facies metabasalts from Alpine Corsica, France, which reached the critical depths at which important devolatilization reactions occur in subducting slabs. The studied samples indicate that the evolution of oceanic crustal sequences subducted under present-day thermal regimes is dominated by localized fluid-rock interactions that are strongly controlled by the nature and extent of inherited (sub)seafloor hydrothermal processes, and by the possibility of deep fluids to be channelized along inherited or newly-formed discontinuities. Fluid channelization along inherited discontinuities controlled local rehydration and dehydration/decarbonation reactions and the stability of carbonate and silicate minerals at the blueschist-eclogite transition. Fluid-mediated decarbonation was driven by upward, up-temperature fluid flow in the inverted geothermal gradient of a subducting oceanic slab, a process that has not been documented in natural samples to date. We estimate that the observed fluid-rock reactions released 20-60 kg CO2 per m3 of rock (i.e. 0.7-2.1 wt% CO2), which is in line with the values predicted from decarbonation of metabasalts in open systems at these depths. Conversely, the estimated time-integrated fluid fluxes (20-50 t/m2) indicate that the amount of carbon transported by channelized fluid flow within the volcanic part of subducting oceanic plates is potentially much higher than previous numerical estimates, testifying to the percolation of C-bearing fluids resulting from devolatilization/dissolution processes operative in large reservoirs.

Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.

ERIC Educational Resources Information Center

Diamandis, E. P.; And Others

1983-01-01

The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

Measurement and modeling of advanced coal conversion processes, Volume II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solomon, P.R.; Serio, M.A.; Hamblen, D.G.

1993-06-01

A two dimensional, steady-state model for describing a variety of reactive and nonreactive flows, including pulverized coal combustion and gasification, is presented. The model, referred to as 93-PCGC-2 is applicable to cylindrical, axi-symmetric systems. Turbulence is accounted for in both the fluid mechanics equations and the combustion scheme. Radiation from gases, walls, and particles is taken into account using a discrete ordinates method. The particle phase is modeled in a lagrangian framework, such that mean paths of particle groups are followed. A new coal-general devolatilization submodel (FG-DVC) with coal swelling and char reactivity submodels has been added.

Determining Kinetic Parameters for Isothermal Crystallization of Glasses

NASA Technical Reports Server (NTRS)

Ray, C. S.; Zhang, T.; Reis, S. T.; Brow, R. K.

2006-01-01

Non-isothermal crystallization techniques are frequently used to determine the kinetic parameters for crystallization in glasses. These techniques are experimentally simple and quick compared to the isothermal techniques. However, the analytical models used for non-isothermal data analysis, originally developed for describing isothermal transformation kinetics, are fundamentally flawed. The present paper describes a technique for determining the kinetic parameters for isothermal crystallization in glasses, which eliminates most of the common problems that generally make the studies of isothermal crystallization laborious and time consuming. In this technique, the volume fraction of glass that is crystallized as a function of time during an isothermal hold was determined using differential thermal analysis (DTA). The crystallization parameters for the lithium-disilicate (Li2O.2SiO2) model glass were first determined and compared to the same parameters determined by other techniques to establish the accuracy and usefulness of the present technique. This technique was then used to describe the crystallization kinetics of a complex Ca-Sr-Zn-silicate glass developed for sealing solid oxide fuel cells.

Utilization of the Recycle Reactor in Determining Kinetics of Gas-Solid Catalytic Reactions.

ERIC Educational Resources Information Center

Paspek, Stephen C.; And Others

1980-01-01

Describes a laboratory scale reactor that determines the kinetics of a gas-solid catalytic reaction. The external recycle reactor construction is detailed with accompanying diagrams. Experimental details, application of the reactor to CO oxidation kinetics, interphase gradients, and intraphase gradients are discussed. (CS)

SVD-aided pseudo principal-component analysis: A new method to speed up and improve determination of the optimum kinetic model from time-resolved data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oang, Key Young; Yang, Cheolhee; Muniyappan, Srinivasan

Determination of the optimum kinetic model is an essential prerequisite for characterizing dynamics and mechanism of a reaction. Here, we propose a simple method, termed as singular value decomposition-aided pseudo principal-component analysis (SAPPA), to facilitate determination of the optimum kinetic model from time-resolved data by bypassing any need to examine candidate kinetic models. We demonstrate the wide applicability of SAPPA by examining three different sets of experimental time-resolved data and show that SAPPA can efficiently determine the optimum kinetic model. In addition, the results of SAPPA for both time-resolved X-ray solution scattering (TRXSS) and transient absorption (TA) data of themore » same protein reveal that global structural changes of protein, which is probed by TRXSS, may occur more slowly than local structural changes around the chromophore, which is probed by TA spectroscopy.« less

Linear prediction and single-channel recording.

PubMed

Carter, A A; Oswald, R E

1995-08-01

The measurement of individual single-channel events arising from the gating of ion channels provides a detailed data set from which the kinetic mechanism of a channel can be deduced. In many cases, the pattern of dwells in the open and closed states is very complex, and the kinetic mechanism and parameters are not easily determined. Assuming a Markov model for channel kinetics, the probability density function for open and closed time dwells should consist of a sum of decaying exponentials. One method of approaching the kinetic analysis of such a system is to determine the number of exponentials and the corresponding parameters which comprise the open and closed dwell time distributions. These can then be compared to the relaxations predicted from the kinetic model to determine, where possible, the kinetic constants. We report here the use of a linear technique, linear prediction/singular value decomposition, to determine the number of exponentials and the exponential parameters. Using simulated distributions and comparing with standard maximum-likelihood analysis, the singular value decomposition techniques provide advantages in some situations and are a useful adjunct to other single-channel analysis techniques.

Determination of outer layer and bulk dehydration kinetics of trehalose dihydrate using atomic force microscopy, gravimetric vapour sorption and near infrared spectroscopy.

PubMed

Jones, Matthew D; Beezer, Anthony E; Buckton, Graham

2008-10-01

Knowledge of the kinetics of solid state reactions is important when considering the stability of many medicines. Potentially, such reactions could follow different kinetics on the surface of particles when compared with their interior, yet solid state processes are routinely followed using only bulk characterisation techniques. Atomic force microscopy (AFM) has previously been shown to be a suitable technique for the investigation of surface processes, but has not been combined with bulk techniques in order to analyse surface and bulk kinetics separately. This report therefore describes the investigation of the outer layer and bulk kinetics of the dehydration of trehalose dihydrate at ambient temperature and low humidity, using AFM, dynamic vapour sorption (DVS) and near infrared spectroscopy (NIR). The use of AFM enabled the dehydration kinetics of the outer layers to be determined both directly and from bulk data. There were no significant differences between the outer layer dehydration kinetics determined using these methods. AFM also enabled the bulk-only kinetics to be analysed from the DVS and NIR data. These results suggest that the combination of AFM and bulk characterisation techniques should enable a more complete understanding of the kinetics of certain solid state reactions to be achieved. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

On the formation of granulites

USGS Publications Warehouse

Bohlen, S.R.

1991-01-01

The tectonic settings for the formation and evolution of regional granulite terranes and the lowermost continental crust can be deduced from pressure-temperature-time (P-T-time) paths and constrained by petrological and geophysical considerations. P-T conditions deduced for regional granulites require transient, average geothermal gradients of greater than 35??C km-1, implying minimum heat flow in excess of 100 mW m-2. Such high heat flow is probably caused by magmatic heating. Tectonic settings wherein such conditions are found include convergent plate margins, continental rifts, hot spots and at the margins of large, deep-seated batholiths. Cooling paths can be constrained by solid-solid and devolatilization equilibria and geophysical modelling. -from Author

Pulverized coal burner

DOEpatents

Sivy, J.L.; Rodgers, L.W.; Koslosy, J.V.; LaRue, A.D.; Kaufman, K.C.; Sarv, H.

1998-11-03

A burner is described having lower emissions and lower unburned fuel losses by implementing a transition zone in a low NO{sub x} burner. The improved burner includes a pulverized fuel transport nozzle surrounded by the transition zone which shields the central oxygen-lean fuel devolatilization zone from the swirling secondary combustion air. The transition zone acts as a buffer between the primary and the secondary air streams to improve the control of near-burner mixing and flame stability by providing limited recirculation regions between primary and secondary air streams. These limited recirculation regions transport evolved NO{sub x} back towards the oxygen-lean fuel pyrolysis zone for reduction to molecular nitrogen. Alternate embodiments include natural gas and fuel oil firing. 8 figs.

Pulverized coal burner

DOEpatents

Sivy, Jennifer L.; Rodgers, Larry W.; Koslosy, John V.; LaRue, Albert D.; Kaufman, Keith C.; Sarv, Hamid

1998-01-01

A burner having lower emissions and lower unburned fuel losses by implementing a transition zone in a low NO.sub.x burner. The improved burner includes a pulverized fuel transport nozzle surrounded by the transition zone which shields the central oxygen-lean fuel devolatilization zone from the swirling secondary combustion air. The transition zone acts as a buffer between the primary and the secondary air streams to improve the control of near-burner mixing and flame stability by providing limited recirculation regions between primary and secondary air streams. These limited recirculation regions transport evolved NO.sub.x back towards the oxygen-lean fuel pyrolysis zone for reduction to molecular nitrogen. Alternate embodiments include natural gas and fuel oil firing.

Kinetics and thermodynamics of chemical reactions in Li/SOCl2 cells

NASA Technical Reports Server (NTRS)

Hansen, Lee D.; Frank, Harvey

1987-01-01

Work is described that was designed to determine the kinetic constants necessary to extrapolate kinetic data on Li/SOCl2 cells over the temperature range from 25 to 75 C. A second objective was to characterize as far as possible the chemical reactions that occur in the cells since these reactions may be important in understanding the potential hazards of these cells. The kinetics of the corrosion processes in undischarged Li/SOCl2 cells were determined and separated according to their occurrence at the anode and cathode; the effects that switching the current on and off has on the corrosion reactions was determined; and the effects of discharge state on the kinetics of the corrosion process were found. A thermodynamic analysis of the current-producing reactions in the cell was done and is included.

Saponification reaction system: a detailed mass transfer coefficient determination.

PubMed

Pečar, Darja; Goršek, Andreja

2015-01-01

The saponification of an aromatic ester with an aqueous sodium hydroxide was studied within a heterogeneous reaction medium in order to determine the overall kinetics of the selected system. The extended thermo-kinetic model was developed compared to the previously used simple one. The reaction rate within a heterogeneous liquid-liquid system incorporates a chemical kinetics term as well as mass transfer between both phases. Chemical rate constant was obtained from experiments within a homogeneous medium, whilst the mass-transfer coefficient was determined separately. The measured thermal profiles were then the bases for determining the overall reaction-rate. This study presents the development of an extended kinetic model for considering mass transfer regarding the saponification of ethyl benzoate with sodium hydroxide within a heterogeneous reaction medium. The time-dependences are presented for the mass transfer coefficient and the interfacial areas at different heterogeneous stages and temperatures. The results indicated an important role of reliable kinetic model, as significant difference in k(L)a product was obtained with extended and simple approach.

Systems, methods and computer-readable media to model kinetic performance of rechargeable electrochemical devices

DOEpatents

Gering, Kevin L.

2013-01-01

A system includes an electrochemical cell, monitoring hardware, and a computing system. The monitoring hardware samples performance characteristics of the electrochemical cell. The computing system determines cell information from the performance characteristics. The computing system also analyzes the cell information of the electrochemical cell with a Butler-Volmer (BV) expression modified to determine exchange current density of the electrochemical cell by including kinetic performance information related to pulse-time dependence, electrode surface availability, or a combination thereof. A set of sigmoid-based expressions may be included with the modified-BV expression to determine kinetic performance as a function of pulse time. The determined exchange current density may be used with the modified-BV expression, with or without the sigmoid expressions, to analyze other characteristics of the electrochemical cell. Model parameters can be defined in terms of cell aging, making the overall kinetics model amenable to predictive estimates of cell kinetic performance along the aging timeline.

Visual evaluation of kinetic characteristics of PET probe for neuroreceptors using a two-phase graphic plot analysis.

PubMed

Ito, Hiroshi; Ikoma, Yoko; Seki, Chie; Kimura, Yasuyuki; Kawaguchi, Hiroshi; Takuwa, Hiroyuki; Ichise, Masanori; Suhara, Tetsuya; Kanno, Iwao

2017-05-01

Objectives In PET studies for neuroreceptors, tracer kinetics are described by the two-tissue compartment model (2-TCM), and binding parameters, including the total distribution volume (V T ), non-displaceable distribution volume (V ND ), and binding potential (BP ND ), can be determined from model parameters estimated by kinetic analysis. The stability of binding parameter estimates depends on the kinetic characteristics of radioligands. To describe these kinetic characteristics, we previously developed a two-phase graphic plot analysis in which V ND and V T can be estimated from the x-intercept of regression lines for early and delayed phases, respectively. In this study, we applied this graphic plot analysis to visual evaluation of the kinetic characteristics of radioligands for neuroreceptors, and investigated a relationship between the shape of these graphic plots and the stability of binding parameters estimated by the kinetic analysis with 2-TCM in simulated brain tissue time-activity curves (TACs) with various binding parameters. Methods 90-min TACs were generated with the arterial input function and assumed kinetic parameters according to 2-TCM. Graphic plot analysis was applied to these simulated TACs, and the curvature of the plot for each TAC was evaluated visually. TACs with several noise levels were also generated with various kinetic parameters, and the bias and variation of binding parameters estimated by kinetic analysis were calculated in each TAC. These bias and variation were compared with the shape of graphic plots. Results The graphic plots showed larger curvature for TACs with higher specific binding and slower dissociation of specific binding. The quartile deviations of V ND and BP ND determined by kinetic analysis were smaller for radioligands with slow dissociation. Conclusions The larger curvature of graphic plots for radioligands with slow dissociation might indicate a stable determination of V ND and BP ND by kinetic analysis. For investigation of the kinetics of radioligands, such kinetic characteristics should be considered.

Tracing fluid transfer across subduction zones using iron and zinc stable isotopes

NASA Astrophysics Data System (ADS)

Williams, H. M.; Debret, B.; Pons, M. L.; Bouilhol, P.

2016-12-01

In subduction zones, serpentinite devolatilization within the downgoing slab and the fluids released play a fundamental role in volatile transfer as well as the redox evolution of the sub-arc mantle. Constraining subduction-related serpentinite devolatilisation is essential in order to better understand of the nature and composition of slab-derived fluids and fluid/rock interactions. Fe and Zn stable isotopes can trace fluid composition and speciation as isotope partitioning is driven by changes in oxidation state, coordination, and bonding environment. In the case of serpentinite devolatilisation, Fe isotope fractionation should reflect changes in Fe redox state and the formation of Fe-Cl- and SO42- complexes (Hill et al., GCA 2010); Zn isotope fractionation should be sensitive to complexation with CO32-, HS- and SO42- anions (Fujii et al., GCA 2011). We targeted samples from Western Alps ophiolite complexes, interpreted as remnants of serpentinized oceanic lithosphere metamorphosed and devolatilized during subduction (Hattori and Guillot, G3 2007; Debret et al., Chem. Geol. 2013). A striking negative correlation is present between bulk serpentinite Fe isotope composition and Fe3+/Fetot, with the highest grade samples displaying the heaviest Fe isotope compositions and lowest Fe3+/Fetot (Debret et al., Geology, 2016). The same samples also display a corresponding variation in Zn isotopes, with the highest grade samples displaying isotopically light compositions (Pons et al., in revision). The negative correlation between Fe and Zn isotopes and decrease in Fe3+/Fetot can explained by serpentinite sulfide breakdown and the release of fluids enriched in isotopically light Fe and heavy Zn sulphate complexes. The migration of these SOX-bearing fluids from the slab to the slab-mantle interface or mantle wedge has important implications for the redox evolution of the sub-arc mantle and the transport of metals from the subducting slab.

GIANT IMPACT: AN EFFICIENT MECHANISM FOR THE DEVOLATILIZATION OF SUPER-EARTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Shang-Fei; Hori, Yasunori; Lin, D. N. C.

Mini-Neptunes and volatile-poor super-Earths coexist on adjacent orbits in proximity to host stars such as Kepler-36 and Kepler-11. Several post-formation processes have been proposed for explaining the origin of the compositional diversity between neighboring planets: mass loss via stellar XUV irradiation, degassing of accreted material, and in situ accumulation of the disk gas. Close-in planets are also likely to experience giant impacts during the advanced stage of planet formation. This study examines the possibility of transforming volatile-rich super-Earths/mini-Neptunes into volatile-depleted super-Earths through giant impacts. We present the results of three-dimensional hydrodynamic simulations of giant impacts in the accretionary and disruptivemore » regimes. Target planets are modeled with a three-layered structure composed of an iron core, silicate mantle, and hydrogen/helium envelope. In the disruptive case, the giant impact can remove most of the H/He atmosphere immediately and homogenize the refractory material in the planetary interior. In the accretionary case, the planet is able to retain more than half of the original gaseous envelope, while a compositional gradient suppresses efficient heat transfer as the planetary interior undergoes double-diffusive convection. After the giant impact, a hot and inflated planet cools and contracts slowly. The extended atmosphere enhances the mass loss via both a Parker wind induced by thermal pressure and hydrodynamic escape driven by the stellar XUV irradiation. As a result, the entire gaseous envelope is expected to be lost due to the combination of those processes in both cases. Based on our results, we propose that Kepler-36b may have been significantly devolatilized by giant impacts, while a substantial fraction of Kepler-36c’s atmosphere may remain intact. Furthermore, the stochastic nature of giant impacts may account for the observed large dispersion in the mass–radius relationship of close-in super-Earths and mini-Neptunes (at least to some extent)« less

The dynamics of serpentinite dehydration reactions in subduction zones: Constrains from the Cerro del Almirez ultramafic massif (Betic Cordillera, SE Spain)

NASA Astrophysics Data System (ADS)

Dilissen, Nicole; Garrido, Carlos J.; López Sánchez-Vizcaíno, Vicente; Padrón-Navarta, José Alberto

2015-04-01

Arc volcanism, earthquakes and subduction dynamics are controlled by fluids from downgoing slabs and their effect on the melting and rheology of the overlying mantle wedge. High pressure dehydration of serpentinite in the slab and the subduction channel is considered as one of the main sources of fluids in subduction zones. Even though this metamorphic reaction is essential in subduction activities, the behavior of the fluids, the kinetics and thermodynamics during the breakdown reaction are still poorly understood. The Cerro del Almirez (Nevado-Filábride Complex, Betic Cordillera, SE Spain) uniquely preserves the dehydration front from antigorite serpentinite to chlorite-harzburgite and constitutes a unique natural laboratory to investigate high-pressure dehydration of serpentinite. This reaction occurred in a subduction setting releasing up to 13 wt% of water, contributing significantly to the supply of fluids to the overlying mantle wedge. A key to the understanding of the metamorphic conditions prevailing during serpentinite dehydration is to study the two prominent textures -granofels and spinifex-like chlorite harzburgite- occurring in this reaction product. The detailed texture differences in the Chl-harzburgite can provide insights into diverse kinetic and thermodynamic conditions of this dehydration reaction due to variations in effective pressure and drainage conditions. It has been proposed that difference in overpressure (P') and deviation from growth equilibrium, i.e. overstepping, is responsible for these two types of textures [Padrón-Navarta et al., 2011]. The magnitude and duration of P' is highly dependent on dehydration kinetics [Connolly, 1997]. The fast pressure drop, with spinifex-texture as a product, can be linked to draining events expected after hydrofracturing, which are recorded in grain size reduction zones in this massif. According to this hypothesis, mapping of textural variation in Chl-harzburgite might be used as a proxy to investigate the hydrodynamics of serpentinite dehydration reaction. During an intensive detailed field mapping of a well-exposed area of ca. 0.87 km2 in the W-SW part of the massif, we mapped textural variations of Chl-harzburgite every three to ten meters. Granofels and spinifex lenses occur within scales of decimetres to decametres. These spatial scale constrains can be linked to temporal scales of the reactions and to the spatial and temporal variation of fluid release during dehydration of serpentinite. REFERENCES Connolly, J. A. D. (1997), Devolatilization-generated fluid pressure and deformation-propagated fluid flow during prograde regional metamorphism, J. Geophys. Res.-Solid Earth, 102(B8), 18149-18173, doi:10.1029/97jb00731. Padrón-Navarta, J. A., V. López Sánchez-Vizcaíno, C. J. Garrido, and M. T. Gómez-Pugnaire (2011), Metamorphic record of high-pressure dehydration of antigorite serpentinite to chlorite harzburgite in a subduction setting (Cerro del Almirez, Nevado-Filábride Complex, southern Spain), Journal of Petrology, 52(10), 2047-2078.

Clarifications regarding the use of model-fitting methods of kinetic analysis for determining the activation energy from a single non-isothermal curve.

PubMed

Sánchez-Jiménez, Pedro E; Pérez-Maqueda, Luis A; Perejón, Antonio; Criado, José M

2013-02-05

This paper provides some clarifications regarding the use of model-fitting methods of kinetic analysis for estimating the activation energy of a process, in response to some results recently published in Chemistry Central journal. The model fitting methods of Arrhenius and Savata are used to determine the activation energy of a single simulated curve. It is shown that most kinetic models correctly fit the data, each providing a different value for the activation energy. Therefore it is not really possible to determine the correct activation energy from a single non-isothermal curve. On the other hand, when a set of curves are recorded under different heating schedules are used, the correct kinetic parameters can be clearly discerned. Here, it is shown that the activation energy and the kinetic model cannot be unambiguously determined from a single experimental curve recorded under non isothermal conditions. Thus, the use of a set of curves recorded under different heating schedules is mandatory if model-fitting methods are employed.

Second Harmonic Correlation Spectroscopy: Theory and Principles for Determining Surface Binding Kinetics.

PubMed

Sly, Krystal L; Conboy, John C

2017-06-01

A novel application of second harmonic correlation spectroscopy (SHCS) for the direct determination of molecular adsorption and desorption kinetics to a surface is discussed in detail. The surface-specific nature of second harmonic generation (SHG) provides an efficient means to determine the kinetic rates of adsorption and desorption of molecular species to an interface without interference from bulk diffusion, which is a significant limitation of fluorescence correlation spectroscopy (FCS). The underlying principles of SHCS for the determination of surface binding kinetics are presented, including the role of optical coherence and optical heterodyne mixing. These properties of SHCS are extremely advantageous and lead to an increase in the signal-to-noise (S/N) of the correlation data, increasing the sensitivity of the technique. The influence of experimental parameters, including the uniformity of the TEM00 laser beam, the overall photon flux, and collection time are also discussed, and are shown to significantly affect the S/N of the correlation data. Second harmonic correlation spectroscopy is a powerful, surface-specific, and label-free alternative to other correlation spectroscopic methods for examining surface binding kinetics.

Predicting repeat protein folding kinetics from an experimentally determined folding energy landscape

PubMed Central

Street, Timothy O; Barrick, Doug

2009-01-01

The Notch ankyrin domain is a repeat protein whose folding has been characterized through equilibrium and kinetic measurements. In previous work, equilibrium folding free energies of truncated constructs were used to generate an experimentally determined folding energy landscape (Mello and Barrick, Proc Natl Acad Sci USA 2004;101:14102–14107). Here, this folding energy landscape is used to parameterize a kinetic model in which local transition probabilities between partly folded states are based on energy values from the landscape. The landscape-based model correctly predicts highly diverse experimentally determined folding kinetics of the Notch ankyrin domain and sequence variants. These predictions include monophasic folding and biphasic unfolding, curvature in the unfolding limb of the chevron plot, population of a transient unfolding intermediate, relative folding rates of 19 variants spanning three orders of magnitude, and a change in the folding pathway that results from C-terminal stabilization. These findings indicate that the folding pathway(s) of the Notch ankyrin domain are thermodynamically selected: the primary determinants of kinetic behavior can be simply deduced from the local stability of individual repeats. PMID:19177351

Bisubstrate inhibition: Theory and application to N-acetyltransferases.

PubMed

Yu, Michael; Magalhães, Maria L B; Cook, Paul F; Blanchard, John S

2006-12-12

Bisubstrate inhibitors represent a potentially powerful group of compounds that have found significant therapeutic utility. Although these compounds have been synthesized and tested against a number of enzymes that catalyze sequential bireactant reactions, the detailed theory for predicting the expected patterns of inhibition against the two substrates for various bireactant kinetic mechanisms has, heretofore, not been presented. We have derived the rate equations for all likely sequential bireactant mechanisms and provide two examples in which bisubstrate inhibitors allow the kinetic mechanism to be determined. Bisubstrate inhibitor kinetics is a powerful diagnostic for the determination of kinetic mechanisms.

Thermodynamics and Kinetics of Chemical Equilibrium in Solution.

ERIC Educational Resources Information Center

Leenson, I. A.

1986-01-01

Discusses theory of thermodynamics of the equilibrium in solution and dissociation-dimerization kinetics. Describes experimental procedure including determination of molar absorptivity and equilibrium constant, reaction enthalpy, and kinetics of the dissociation-dimerization reaction. (JM)

Reduced Equations for Calculating the Combustion Rates of Jet-A and Methane Fuel

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2003-01-01

Simplified kinetic schemes for Jet-A and methane fuels were developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) that is being developed at Glenn. These kinetic schemes presented here result in a correlation that gives the chemical kinetic time as a function of initial overall cell fuel/air ratio, pressure, and temperature. The correlations would then be used with the turbulent mixing times to determine the limiting properties and progress of the reaction. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentration of carbon monoxide as a function of fuel air ratio, pressure, and temperature. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates and the values obtained from the equilibrium correlations were then used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide, and NOx were obtained for both Jet-A fuel and methane.

Experimental dynamic metamorphism of mineral single crystals

USGS Publications Warehouse

Kirby, S.H.; Stern, L.A.

1993-01-01

This paper is a review of some of the rich and varied interactions between non-hydrostatic stress and phase transformations or mineral reactions, drawn mainly from results of experiments done on mineral single crystals in our laboratory or our co-authors. The state of stress and inelastic deformation can enter explicitly into the equilibrium phase relations and kinetics of mineral reactions. Alternatively, phase transformations can have prominent effects on theology and on the nature of inelastic deformation. Our examples represent five types of structural phase changes, each of which is distinguished by particular mechanical effects. In increasing structural complexity, these include: (1) displacive phase transformations involving no bond-breaking, which may produce anomalous brittle behavior. A primary example is the a-?? quartz transition which shows anomalously low fracture strength and tertiary creep behavior near the transition temperature; (2) martensitic-like transformations involving transformation strains dominated by shear deformation. Examples include the orthoenstatite ??? clinoenstatite and w u ??rtzite ??? sphalerite transformations; (3) coherent exsolution or precipitation of a mineral solute from a supersaturated solid-solution, with anisotropy of precipitation and creep rates produced under nonhydrostatic stress. Examples include exsolution of corundum from MgO ?? nAl2O3 spinels and Ca-clinopyroxene from orthopyroxene; (4) order-disorder transformations that are believed to cause anomalous plastic yield strengthening, such as MgO - nAl2O3 spinels; and (5) near-surface devolatilization of hydrous silicate single-crystals that produces a fundamental brittleness thought to be connected with dehydration at microcracks at temperatures well below nominal macroscopic dehydration temperatures. As none of these interactions between single-crystal phase transformations and non-hydrostatic stress is understood in detail, this paper serves as a challenge to field structural geologists to test whether interactions of these types occur in nature, and to theoreticians to reach a deeper understanding of the complex relations between phase transformations, the local state of stress and associated deformation and deformation rates. ?? 1993.

Chemistry of Earth's Putative Steam Atmosphere

NASA Astrophysics Data System (ADS)

Fegley, B.; Schaefer, L.

2007-12-01

The concept of a steam atmosphere generated by impact devolatilization of planetesimals accreted during Earth's formation is over 20 years old (Matsui and Abe, 1986; Lange and Ahrens, 1982). Surprisingly, with the possible exception of a few qualitative remarks, no one has critically assessed this scenario. We use thermochemical equilibrium and, where relevant, thermochemical kinetic calculations to model the chemistry of the "steam" atmosphere produced by impact volatilization of different types of accreting material. We present results for our nominal conditions (1500 K, total P = 100 bar). We also studied the effects of variable temperature and total pressure. The composition of the accreting material is modeled using average compositions of the Orgueil CI chondrite, the Murchison CM2 chondrite, the Allende CV3 chondrite, average ordinary (H, L, LL) chondrites, and average enstatite (EH, EL) chondrites. The major gases released from CI and CM chondritic material are H2O, CO2, H2, H2S, CO, CH4, and SO2 in decreasing order of abundance. About 10% of the atmosphere is CO2. The major gases released from CV chondritic material are CO2, H2O, CO, H2, and SO2 in decreasing order of abundance. About 20% of the total atmosphere is steam. The major gases released from average ordinary chondritic material are H2, CO, H2O, CO2, CH4, H2S, and N2 in decreasing order of abundance. The "steam" atmosphere is predominantly H2 + CO with steam being about 10% of the total atmosphere. The major gases released from EH chondritic material are H2, CO, H2O, CO2, N2, and CH4 in decreasing order of abundance. The "steam" atmosphere is predominantly H2 + CO with about 10% of the total atmosphere as steam. This work was supported by the NASA Astrobiology and Origins Programs.

A homogeneous quenching resonance energy transfer assay for the kinetic analysis of the GTPase nucleotide exchange reaction.

PubMed

Kopra, Kari; Ligabue, Alessio; Wang, Qi; Syrjänpää, Markku; Blaževitš, Olga; Veltel, Stefan; van Adrichem, Arjan J; Hänninen, Pekka; Abankwa, Daniel; Härmä, Harri

2014-07-01

A quenching resonance energy transfer (QRET) assay for small GTPase nucleotide exchange kinetic monitoring is demonstrated using nanomolar protein concentrations. Small GTPases are central signaling proteins in all eukaryotic cells acting as a "molecular switches" that are active in the GTP-state and inactive in the GDP-state. GTP-loading is highly regulated by guanine nucleotide exchange factors (GEFs). In several diseases, most prominently cancer, this process in misregulated. The kinetics of the nucleotide exchange reaction reports on the enzymatic activity of the GEF reaction system and is, therefore, of special interest. We determined the nucleotide exchange kinetics using europium-labeled GTP (Eu-GTP) in the QRET assay for small GTPases. After GEF catalyzed GTP-loading of a GTPase, a high time-resolved luminescence signal was found to be associated with GTPase bound Eu-GTP, whereas the non-bound Eu-GTP fraction was quenched by soluble quencher. The association kinetics of the Eu-GTP was measured after GEF addition, whereas the dissociation kinetics could be determined after addition of unlabeled GTP. The resulting association and dissociation rates were in agreement with previously published values for H-Ras(Wt), H-Ras(Q61G), and K-Ras(Wt), respectively. The broader applicability of the QRET assay for small GTPases was demonstrated by determining the kinetics of the Ect2 catalyzed RhoA(Wt) GTP-loading. The QRET assay allows the use of nanomolar protein concentrations, as more than 3-fold signal-to-background ratio was achieved with 50 nM GTPase and GEF proteins. Thus, small GTPase exchange kinetics can be efficiently determined in a HTS compatible 384-well plate format.

Impact erosion of planetary atmospheres

NASA Astrophysics Data System (ADS)

Shuvalov, Valery

1999-06-01

The problem of planetary atmospheres evolution due to impacts of large cosmic bodies was investigated by Ahrens, O'Keefe, Cameron, Hunten and others. These studies were focused mainly on the atmosphere growth under impact devolatilization and atmosphere losses due to escape of high velocity ejecta. Most of the results concerning atmosphere erosion were based on assumption that atmosphere itself does not influence significantly on the ejecta evolution. However more detailed investigations show that atmospheric drag is important at least for 1-10km impactors. From the other hand the theory of large explosions in an exponential atmosphere is not applicable in the case under consideration because of the influence of a trail created during the body flight through the atmosphere. In the present study the problem of 1-10km asteroid impacts against the Earth is investigated with the use of multi-material hydrocode SOVA. This code is similar to the widely used CTH system and allows to model all stages of the impact (penetration into the atmosphere, collision with the ground surface covered by water basin, ejecta evolution). The air mass ejected from each altitude depending on impactor size and velocity is determined. Apart from the impacts into the present-day atmosphere, the erosion of the dense Proto-Atmosphere is also considered.

iSCHRUNK--In Silico Approach to Characterization and Reduction of Uncertainty in the Kinetic Models of Genome-scale Metabolic Networks.

PubMed

Andreozzi, Stefano; Miskovic, Ljubisa; Hatzimanikatis, Vassily

2016-01-01

Accurate determination of physiological states of cellular metabolism requires detailed information about metabolic fluxes, metabolite concentrations and distribution of enzyme states. Integration of fluxomics and metabolomics data, and thermodynamics-based metabolic flux analysis contribute to improved understanding of steady-state properties of metabolism. However, knowledge about kinetics and enzyme activities though essential for quantitative understanding of metabolic dynamics remains scarce and involves uncertainty. Here, we present a computational methodology that allow us to determine and quantify the kinetic parameters that correspond to a certain physiology as it is described by a given metabolic flux profile and a given metabolite concentration vector. Though we initially determine kinetic parameters that involve a high degree of uncertainty, through the use of kinetic modeling and machine learning principles we are able to obtain more accurate ranges of kinetic parameters, and hence we are able to reduce the uncertainty in the model analysis. We computed the distribution of kinetic parameters for glucose-fed E. coli producing 1,4-butanediol and we discovered that the observed physiological state corresponds to a narrow range of kinetic parameters of only a few enzymes, whereas the kinetic parameters of other enzymes can vary widely. Furthermore, this analysis suggests which are the enzymes that should be manipulated in order to engineer the reference state of the cell in a desired way. The proposed approach also sets up the foundations of a novel type of approaches for efficient, non-asymptotic, uniform sampling of solution spaces. Copyright © 2015 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

Oxidizing of ferulic acid with the use of polyoxometalates as catalysts

NASA Astrophysics Data System (ADS)

Povarnitsyna, T. V.; Popova, N. R.; Bogolitsyn, K. G.; Beloglazova, A. L.; Pryakhin, A. N.; Lunin, V. V.

2010-12-01

The kinetics of catalytic oxidation for ferulic acid with polyoxometalates used as catalysts was studied. The effect of pH and concentrations of the principal reacting components on the process kinetics was studied. A kinetic scheme of oxidation is proposed, and the values of a number of kinetic parameters of the process are determined.

Origami Arrays as Substrates for the Determination of Reaction Kinetics Using High-Speed Atomic Force Microscopy.

PubMed

Rahman, Masudur; Day, B Scott; Neff, David; Norton, Michael L

2017-08-01

DNA nanostructures (DN) are powerful platforms for the programmable assembly of nanomaterials. As applications for DN both as a structural material and as a support for functional biomolecular sensing systems develop, methods enabling the determination of reaction kinetics in real time become increasingly important. In this report, we present a study of the kinetics of streptavidin binding onto biotinylated DN constructs enabled by these planar structures. High-speed AFM was employed at a 2.5 frame/s rate to evaluate the kinetics and indicates that the binding fully saturates in less than 60 s. When the the data was fitted with an adsorption-limited kinetic model, a forward rate constant of 5.03 × 10 5 s -1 was found.

Study of Metal-NH[subscript 3] Interfaces (Metal= Cu, Ni, Ag) Using Potentiostatic Curves

ERIC Educational Resources Information Center

Nunes, Nelson; Martins, Angela; Leitao, Ruben Elvas

2007-01-01

Experiment is conducted to determine the kinetic parameters of metal-solution interfaces. During the experiment the kinetic parameters for the interfaces Cu-NH[subscript 3], Ag-NH[subscript 3] and Ni-NH[subscript 3] is easily determined.

Evaluation of the cure kinetics of the wood/pMDI bondline

Treesearch

David P. Harper; Michael P. Wolcott; Timothy G. Rials

2001-01-01

Micro-dielectric analysis (µDEA) and differentia1 scanning calorimetry (DSC) were used to monitor cure of polymeric diphenyl-methane diisocyanate (pMDI) resin with wood strands in a saturated steam environment. A first-order autocatalyzed kinetic model was employed to determine kinetic parameters. The kinetics were found to follow an Arrhenius relation. A single ramp...

Thermogravimetric analysis for the determination of water release rate from microcrystalline cellulose dry powder and wet bead systems.

PubMed

Mayville, Francis C; Wigent, Rodney J; Schwartz, Joseph B

2006-01-01

The purpose of this work was to determine the total amount of water contained in dry powder and wet bead samples of microcrystalline cellulose, MCC, (Avicel PH-101), taken from various stages of the extrusion/marumerization process used to make beads and to determine the kinetic rates of water release from each sample. These samples were allowed to equilibrate in controlled humidity chambers at 25 degrees C. The total amount of water in each sample, after equilibration, was determined by thermogravimetric analysis (TGA) as a function of temperature. The rates of water release from these samples were determined by using isothermal gravimetric analysis (ITGA) as a function of time. Analysis of the results for these studies suggest that water was released from these systems by several different kinetic mechanisms. The water release mechanisms for these systems include: zero order, second order, and diffusion controlled kinetics. It is believed that all three kinetic mechanisms will occur at the same time, however; only one mechanism will be prominent. The prominent mechanism was based on the amount of water present in the sample.

A kinetic study on sesame cake protein hydrolysis by Alcalase.

PubMed

Demirhan, Elçin; Apar, Dilek Kılıç; Özbek, Belma

2011-01-01

In the present study, the hydrolysis of sesame cake protein was performed by Alcalase, a bacterial protease produced by Bacillus licheniformis, to investigate the reaction kinetics of sesame cake hydrolysis and to determine decay and product inhibition effects for Alcalase. The reactions were carried out for 10 min in 0.1 L of aqueous solutions containing 10, 15, 20, 25, and 30 g protein/L at various temperature and pH values. To determine decay and product inhibition effects for Alcalase, a series of inhibition experiments were conducted with the addition of various amounts of hydrolysate. The reaction kinetics was investigated by initial rate approach. The initial reaction rates were determined from the slopes of the linear models that fitted to the experimental data. The kinetic parameters, K(m) and V(max), were estimated as 41.17 g/L and 9.24 meqv/L x min. The Lineweaver-Burk plots showed that the type of inhibition for Alcalase determined as uncompetitive, and the inhibition constant, K(i), was estimated as 38.24% (hydrolysate/substrate mixture). Practical Application: Plant proteins are increasingly being used as an alternative to proteins from animal sources to perform functional roles in food formulation. Knowledge of the kinetics of the hydrolysis reaction is essential for the optimization of enzymatic protein hydrolysis and for increasing the utilization of plant proteins in food products. Therefore, in the present study, the hydrolysis of sesame cake protein was performed by Alcalase, a bacterial protease produced by B. licheniformis, to investigate the reaction kinetics of sesame cake hydrolysis and to determine decay and product inhibition effects for Alcalase.

Solid State Kinetic Parameters and Chemical Mechanism of the Dehydration of CoCl2.6H2O.

ERIC Educational Resources Information Center

Ribas, Joan; And Others

1988-01-01

Presents an experimental example illustrating the most common methods for the determination of kinetic parameters. Discusses the different theories and equations to be applied and the mechanism derived from the kinetic results. (CW)

Fast and calibration free determination of first order reaction kinetics in API synthesis using in-situ ATR-FTIR.

PubMed

Rehbein, Moritz C; Husmann, Sascha; Lechner, Christian; Kunick, Conrad; Scholl, Stephan

2018-05-01

In early stages of drug development only sparse amounts of the key substances are available, which is problematic for the determination of important process data like reaction kinetics. Therefore, it is important to perform experiments as economically as possible, especially in regards to limiting compounds. Here we demonstrate the use of a temperature step experiment enabling the determination of complete reaction kinetics in a single non-isothermal experiment. In contrast to the traditionally used HPLC, the method takes advantage of the high measuring rate and the low amount of labor involved in using in-situ ATR-FTIR to determine time-dependent concentration-equivalent data. Copyright © 2017 Elsevier B.V. All rights reserved.

Kinetic studies of the yeast His-Asp phosphorelay signaling pathway

PubMed Central

Kaserer, Alla O.; Andi, Babak; Cook, Paul F.; West, Ann H.

2010-01-01

For both prokaryotic and eukaryotic His-Asp phosphorelay signaling pathways, the rates of protein phosphorylation and dephosphorylation determine the stimulus-to-response time frame. Thus, kinetic studies of phosphoryl group transfer between signaling partners are important for gaining a full understanding of how the system is regulated. In many cases, the phosphotransfer reactions are too fast for rates to be determined by manual experimentation. Rapid quench flow techniques thus provide a powerful method for studying rapid reactions that occur in the millisecond time frame. In this chapter, we describe experimental design and procedures for kinetic characterization of the yeast SLN1-YPD1-SSK1 osmoregulatory phosphorelay system using a rapid quench flow kinetic instrument. PMID:20946842

A new approach for development of kinetics of wastewater treatment in aerobic biofilm reactor

NASA Astrophysics Data System (ADS)

Goswami, S.; Sarkar, S.; Mazumder, D.

2017-09-01

Biofilm process is widely used for the treatment of a variety of wastewater especially containing slowly biodegradable substances. It provides resistance against toxic environment and is capable of retaining biomass under continuous operation. Development of kinetics is very much pertinent for rational design of a biofilm process for the treatment of wastewater with or without inhibitory substances. A simple approach for development of such kinetics for an aerobic biofilm reactor has been presented using a novel biofilm model. The said biofilm model is formulated from the correlations between substrate concentrations in the influent/effluent and at biofilm liquid interface along with substrate flux and biofilm thickness complying Monod's growth kinetics. The methodology for determining the kinetic coefficients for substrate removal and biomass growth has been demonstrated stepwise along with graphical representations. Kinetic coefficients like K, k, Y, b t, b s, and b d are determined either from the intercepts of X- and Y-axis or from the slope of the graphical plots.

Determination of the Effects of Medium Composition on the Monochloramine Disinfection Kinetics of Nitrosomonas europaea by the Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods ▿

PubMed Central

Wahman, David G.; Schrantz, Karen A.; Pressman, Jonathan G.

2010-01-01

Various medium compositions (phosphate, 1 to 50 mM; ionic strength, 2.8 to 150 meq/liter) significantly affected Nitrosomonas europaea monochloramine disinfection kinetics, as determined by the Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR) methods (lag coefficient, 37 to 490 [LD] and 91 to 490 [PMA-qPCR] mg·min/liter; Chick-Watson rate constant, 4.0 × 10−3 to 9.3 × 10−3 [LD] and 1.6 × 10−3 to 9.6 × 10−3 [PMA-qPCR] liter/mg·min). Two competing effects may account for the variation in disinfection kinetic parameters: (i) increasing kinetics (disinfection rate constant [k] increased, lag coefficient [b] decreased) with increasing phosphate concentration and (ii) decreasing kinetics (k decreased, b increased) with increasing ionic strength. The results support development of a standard medium for evaluating disinfection kinetics in drinking water. PMID:20952645

Iron oxide nanoparticle-based magnetic resonance method to monitor release kinetics from polymeric particles with high resolution.

PubMed

Chan, Minnie; Schopf, Eric; Sankaranarayanan, Jagadis; Almutairi, Adah

2012-09-18

A new method to precisely monitor rapid release kinetics from polymeric particles using super paramagnetic iron oxide nanoparticles, specifically by measuring spin-spin relaxation time (T(2)), is reported. Previously, we have published the formulation of logic gate particles from an acid-sensitive poly-β-aminoester ketal-2 polymer. Here, a series of poly-β-aminoester ketal-2 polymers with varying hydrophobicities were synthesized and used to formulate particles. We attempted to measure fluorescence of released Nile red to determine whether the structural adjustments could finely tune the release kinetics in the range of minutes to hours; however, this standard technique did not differentiate each release rate of our series. Thus, a new method based on encapsulation of iron oxide nanoparticles was developed, which enabled us to resolve the release kinetics of our particles. Moreover, the kinetics matched the relative hydrophobicity order determined by octanol-water partition coefficients. To the best of our knowledge, this method provides the highest resolution of release kinetics to date.

Effect of experimental and sample factors on dehydration kinetics of mildronate dihydrate: mechanism of dehydration and determination of kinetic parameters.

PubMed

Bērziņš, Agris; Actiņš, Andris

2014-06-01

The dehydration kinetics of mildronate dihydrate [3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate] was analyzed in isothermal and nonisothermal modes. The particle size, sample preparation and storage, sample weight, nitrogen flow rate, relative humidity, and sample history were varied in order to evaluate the effect of these factors and to more accurately interpret the data obtained from such analysis. It was determined that comparable kinetic parameters can be obtained in both isothermal and nonisothermal mode. However, dehydration activation energy values obtained in nonisothermal mode showed variation with conversion degree because of different rate-limiting step energy at higher temperature. Moreover, carrying out experiments in this mode required consideration of additional experimental complications. Our study of the different sample and experimental factor effect revealed information about changes of the dehydration rate-limiting step energy, variable contribution from different rate limiting steps, as well as clarified the dehydration mechanism. Procedures for convenient and fast determination of dehydration kinetic parameters were offered. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Can the evolution of nitrogen cycle be traced by the N isotopic composition in mica?

NASA Astrophysics Data System (ADS)

Pinti, D. L.; Hashizume, K.

2011-12-01

A significant portion of nitrogen present in sedimentary rocks has a biological origin, trapped either in organic form, or as ammonium ion substituting potassium in mica. Mica might preserve biological N isotopic signatures (δ15N) in the geological record, allowing the evolution of the N cycle to be traced. However, diagenetic or metamorphic events can modify the pristine N isotopic signature leading to inaccurate interpretations. For example, devolatilization of the rock leads to a reduction in the N abundance and a contemporary increase of the δ15N because 14N escapes faster than 15N. We measured N isotopic compositions in whole rock, mica and feldspars separates from two Archean suites of cherts: 3.5 Ga Kitty's Gap and North Pole sequences in Pilbara, Western Australia and from the 3.45 Ga Hooggenoeg Fm, Barberton Greenstone Belt, South Africa. N was compared with the argon elemental and isotopic composition, because a relation between NH4+, which replaces K+ and radiogenic 40Ar*, which is produced by electron capture of K+ is expected. Both Pilbara and Barberton cherts show a clear correlation between N and 40Ar*, confirming the occurrence of a common speciation. K-Ar dating of the Hooggenoeg Formation mica and feldspars give ages of 2.1 and 1.1 Ga, respectively, indicating that loosely-bounded noble gas 40Ar* is lost from the host mineral during known metamorphic events. Observed correlations between 40Ar* and N suggests that nitrogen, although more strongly bounded as ammonium is also lost, possibly leading to isotopic fractionation. Measured δ15N values, however, are relatively constant (+8.1±0.6% for whole rock and +10.9±1.2% for mica) and do not display an inverse correlation with N abundances. This suggests either 1) that isotopic fractionation is not produced during N loss or; 2) that a process other than devolatilization fractionate N isotopes. Measured δ15N values are at levels far greater than those expected for Early Archean kerogens (0±2%) thus suggesting that fractionation took place but probably is induced by a process other than devolatilization. Step-combustion analyses of N and Ar from Kitty's Gap cherts reveals the presence of an inverse correlation between δ15N values and the 40Ar*/N ratios indicating mixing between two isotopically distinct components. The first, released at temperatures between 400° and 700° C from hydrous minerals, has a δ15N value close or below 0% and is accompanied by radiogenic Ar. The second, void of radiogenic Ar, is released at temperatures >800° C from anhydrous phases and has a δ15N value of +6 to +8%. The first component is likely ammonium replacing K in mica while the second is possibly ammonium adsorbed in-between negatively charged layers of clay minerals. Upon dehydration, the inter-layer site will be "closed", and loosely adsorbed cations are finally trapped in the mineral while noble gas Ar is lost. The higher δ15N in mica is possibly due either to (1) trapping of N representing a later (post-Archean) event, or; (2) fractionation of N with negative δ15N value due to partial release of N from the adsorption site. Mixing between different aliquots of these two components might possibly explain the observed N isotopic variability among micas in the Archean.

Sr-Nd-Pb Isotope Geochemistry of Melange Formation: Implications for Identification of Fluid Sources in the Mantle Wedge and the Arc

NASA Astrophysics Data System (ADS)

Bebout, G. E.; King, R. L.; Moriguti, T.; Nakamura, E.

2004-12-01

Paramount to our ability to decipher the behavior of fluids and melts within the mantle wedge and the overall subduction system are the chemical compositions of rocks adjacent to the slab-mantle interface. Profound metamorphic and metasomatic alteration of pre-subduction lithologies to form melange along the slab-mantle interface may yield rock types inheriting mixed chemical compositions of diverse pre-subduction lithologies. Early work on melange geochemistry indicates competitive effects between mechanical mixing, metasomatism by fluids or melts, and mineral stabilities imposed by the resulting bulk composition. We have explored the Sr-Nd-Pb isotope geochemistry of low- to high-grade melange zones in the Catalina Schist, CA, to address this crucial missing component in studies of subduction-zone mass flux. The Catalina Schist contains lawsonite-albite (LA), lawsonite-blueschist (LB), and amphibolite (AM) facies melange zones, all with mineralogy dominated by talc, chlorite, and Na-Ca amphiboles, with additional minerals such as micas, rutile, zircon, and apatite stabilized based on bulk sample chemistry. Major element compositions vary, from strongly ultramafic in the AM melange, to more crustal-like compositions (i.e., more reminiscent of basaltic to sedimentary protoliths) for LA and LB melange. However, initial Sr and Nd isotope ratios for all grades of melange are essentially indistinguishable, displaying a wide variation from 87Sr/86Sr=0.703-0.709 and ɛ Nd= +15 to -15. Covariations are generally negative, similar to that of the mantle array, but with some samples extending to higher Sr ratios at constant ɛ Nd that probably reflect inheritance of seawater Sr. No clear mixing relationships between 87Sr/86Sr and 1/Sr exist, suggesting either localized buffering of Sr isotope ratios or that mixing relations are obscured by secondary devolatilization. However, a clear mixing trend for Nd indicates two end-members, one a high-concentration, positive ɛ Nd source (AOC?), the other with low-concentration and negative ɛ Nd (devolatilized sediments?). Likewise, initial Pb isotope ratios for all grades of melange form a single array independent of rock type or inferred protolith. Melange matrix of the Catalina Schist preserves initial 206Pb/204Pb of 18.95-19.59, 207Pb/204Pb of 15.61-15.68, and 208Pb/204Pb of 37.85-39.05. Such elevated Pb ratios are typical of subducting oceanic sediments, but not of MORB-like oceanic crust or peridotites of the depleted mantle. The similarity of these initial ratios suggests pervasive alteration of Pb isotope signatures within diverse rock types by fluids during subduction. As Pb concentrations decline from LA/LB to AM melange, this suggests devolatilization of Pb from the ultramafic AM melange will transfer crustal-like Pb isotope ratios. Sr-Nd-Pb isotope systematics for arc volcanic rocks are commonly used as indicators of fluid sources from the subducting slab to the arc magma source region. Our results suggest such an assumption is extremely dangerous, as hybridization processes common to melange zones are more likely to occur along the slab-mantle interface than is preservation of a pre-subduction section. Such metamorphic mediation and buffering of "slab" compositions is essentially unknown, yet our data support an interpretation where these processes impart a fundamental control on the chemistry of fluids passed to the mantle wedge.

Kinetic determinations of accurate relative oxidation potentials of amines with reactive radical cations.

PubMed

Gould, Ian R; Wosinska, Zofia M; Farid, Samir

2006-01-01

Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials.

Assembly kinetics determine the architecture of α-actinin crosslinked F-actin networks.

PubMed

Falzone, Tobias T; Lenz, Martin; Kovar, David R; Gardel, Margaret L

2012-05-29

The actin cytoskeleton is organized into diverse meshworks and bundles that support many aspects of cell physiology. Understanding the self-assembly of these actin-based structures is essential for developing predictive models of cytoskeletal organization. Here we show that the competing kinetics of bundle formation with the onset of dynamic arrest arising from filament entanglements and crosslinking determine the architecture of reconstituted actin networks formed with α-actinin crosslinks. Crosslink-mediated bundle formation only occurs in dilute solutions of highly mobile actin filaments. As actin polymerization proceeds, filament mobility and bundle formation are arrested concomitantly. By controlling the onset of dynamic arrest, perturbations to actin assembly kinetics dramatically alter the architecture of biochemically identical samples. Thus, the morphology of reconstituted F-actin networks is a kinetically determined structure similar to those formed by physical gels and glasses. These results establish mechanisms controlling the structure and mechanics in diverse semiflexible biopolymer networks.

Kinetic study on ferulic acid production from banana stem waste via mechanical extraction

NASA Astrophysics Data System (ADS)

Zainol, Norazwina; Masngut, Nasratun; Khairi Jusup, Muhamad

2018-04-01

Banana is the tropical plants associated with lots of medicinal properties. It has been reported to be a potential source of phenolic compounds such as ferulic acid (FA). FA has excellent antioxidant properties higher than vitamin C and E. FA also have a wide range of biological activities, such as antioxidant activities and anti-microbial activities. This paper presents an experimental and kinetic study on ferulic acid (FA) production from banana stem waste (BSW) via mechanical extraction. The objective of this research is to determine the kinetic parameters in the ferulic acid production. The banana stem waste was randomly collected from the local banana plantation in Felda Lepar Hilir, Pahang. The banana stem juice was mechanically extracted by using sugarcane press machine (KR3176) and further analyzed in high performance liquid chromatography. The differential and integral method was applied to determine the kinetic parameter of the extraction process and the data obtained were fitted into the 0th, 1st and 2nd order of extraction process. Based on the results, the kinetic parameter and R2 value from were 0.05 and 0.93, respectively. It was determined that the 0th kinetic order fitted the reaction processes to best represent the mechanical extraction.

Mechanisms of starch digestion by α-amylase-Structural basis for kinetic properties.

PubMed

Dhital, Sushil; Warren, Frederick J; Butterworth, Peter J; Ellis, Peter R; Gidley, Michael J

2017-03-24

Recent studies of the mechanisms determining the rate and extent of starch digestion by α-amylase are reviewed in the light of current widely-used classifications for (a) the proportions of rapidly-digestible (RDS), slowly-digestible (SDS), and resistant starch (RS) based on in vitro digestibility, and (b) the types of resistant starch (RS 1,2,3,4…) based on physical and/or chemical form. Based on methodological advances and new mechanistic insights, it is proposed that both classification systems should be modified. Kinetic analysis of digestion profiles provides a robust set of parameters that should replace the classification of starch as a combination of RDS, SDS, and RS from a single enzyme digestion experiment. This should involve determination of the minimum number of kinetic processes needed to describe the full digestion profile, together with the proportion of starch involved in each process, and the kinetic properties of each process. The current classification of resistant starch types as RS1,2,3,4 should be replaced by one which recognizes the essential kinetic nature of RS (enzyme digestion rate vs. small intestinal passage rate), and that there are two fundamental origins for resistance based on (i) rate-determining access/binding of enzyme to substrate and (ii) rate-determining conversion of substrate to product once bound.

Optical Biosensing: Kinetics of Protein A-IGG Binding Using Biolayer Interferometry

ERIC Educational Resources Information Center

Wilson, Jo Leanna; Scott, Israel M.; McMurry, Jonathan L.

2010-01-01

An undergraduate biochemistry laboratory experiment has been developed using biolayer interferometry (BLI), an optical biosensing technique similar to surface plasmon resonance (SPR), in which students obtain and analyze kinetic data for a protein-protein interaction. Optical biosensing is a technique of choice to determine kinetic and affinity…

Determination of kinetic energy applied by center pivot sprinklers

USDA-ARS?s Scientific Manuscript database

The kinetic energy of discrete drops impacting a bare soil surface is generally observed to lead to a drastic reduction in water infiltration rate due to soil surface seal formation. Under center pivot sprinkler irrigation, kinetic energy transferred to the soil prior to crop canopy development can...

Kinetic Tetrazolium Microtiter Assay

NASA Technical Reports Server (NTRS)

Pierson, Duane L.; Stowe, Raymond; Koenig, David

1993-01-01

Kinetic tetrazolium microtiter assay (KTMA) involves use of tetrazolium salts and Triton X-100 (or equivalent), nontoxic, in vitro color developer solubilizing colored metabolite formazan without injuring or killing metabolizing cells. Provides for continuous measurement of metabolism and makes possible to determine rate of action of antimicrobial agent in real time as well as determines effective inhibitory concentrations. Used to monitor growth after addition of stimulatory compounds. Provides for kinetic determination of efficacy of biocide, greatly increasing reliability and precision of results. Also used to determine relative effectiveness of antimicrobial agent as function of time. Capability of generating results on day of test extremely important in treatment of water and waste, disinfection of hospital rooms, and in pharmaceutical, agricultural, and food-processing industries. Assay also used in many aspects of cell biology.

Mechanistic Analysis of Oxidative C–H Cleavages Using Inter- and Intramolecular Kinetic Isotope Effects

PubMed Central

Jung, Hyung Hoon; Floreancig, Paul E.

2009-01-01

A series of monodeuterated benzylic and allylic ethers were subjected to oxidative carbon–hydrogen bond cleavage to determine the impact of structural variation on intramolecular kinetic isotope effects in DDQ-mediated cyclization reactions. These values are compared to the corresponding intermolecular kinetic isotope effects that were accessed through subjecting mixtures of non-deuterated and dideuterated substrates to the reaction conditions. The results indicate that carbon–hydrogen bond cleavage is rate determining and that a radical cation is most likely a key intermediate in the reaction mechanism. PMID:20640173

Nucleation and Growth Kinetics from LaMer Burst Data.

PubMed

Chu, Daniel B K; Owen, Jonathan S; Peters, Baron

2017-10-12

In LaMer burst nucleation, the individual nucleation events happen en masse, quasi-simultaneously, and at nearly identical homogeneous conditions. These properties make LaMer burst nucleation important for applications that require monodispersed particles and also for theoretical analyses. Sugimoto and co-workers predicted that the number of nuclei generated during a LaMer burst depends only on the solute supply rate and the growth rate, independent of the nucleation kinetics. Some experiments confirm that solute supply kinetics control the number of nuclei, but flaws in the original theoretical analysis raise questions about the predicted roles of growth and nucleation kinetics. We provide a rigorous analysis of the coupled equations that govern concentrations of nuclei and solutes. Our analysis confirms that the number of nuclei is largely determined by the solute supply and growth rates, but our predicted relationship differs from that of Sugimoto et al. Moreover, we find that additional nucleus size dependent corrections should emerge in systems with slow growth kinetics. Finally, we show how the nucleation kinetics determine the particle size distribution. We suggest that measured particle size distributions might therefore provide ways to test theoretical models of homogeneous nucleation kinetics.

Thermoluminescence glow curve deconvolution and trapping parameters determination of dysprosium doped magnesium borate glass

NASA Astrophysics Data System (ADS)

Salama, E.; Soliman, H. A.

2018-07-01

In this paper, thermoluminescence glow curves of gamma irradiated magnesium borate glass doped with dysprosium were studied. The number of interfering peaks and in turn the number of electron trap levels are determined using the Repeated Initial Rise (RIR) method. At different heating rates (β), the glow curves were deconvoluted into two interfering peaks based on the results of RIR method. Kinetic parameters such as trap depth, kinetic order (b) and frequency factor (s) for each electron trap level is determined using the Peak Shape (PS) method. The obtained results indicated that, the magnesium borate glass doped with dysprosium has two electron trap levels with the average depth energies of 0.63 and 0.79 eV respectively. These two traps have second order kinetic and are formed at low temperature region. The obtained results due to the glow curve analysis could be used to explain some observed properties such as, high thermal fading and light sensitivity for such thermoluminescence material. In this work, systematic procedures to determine the kinetic parameters of any thermoluminescence material are successfully introduced.

A novel determination of calcite dissolution kinetics in seawater

NASA Astrophysics Data System (ADS)

Subhas, Adam V.; Rollins, Nick E.; Berelson, William M.; Dong, Sijia; Erez, Jonathan; Adkins, Jess F.

2015-12-01

We present a novel determination of the dissolution kinetics of inorganic calcite in seawater. We dissolved 13 C -labeled calcite in unlabeled seawater, and traced the evolving δ13 C composition of the fluid over time to establish dissolution rates. This method provides sensitive determinations of dissolution rate, which we couple with tight constraints on both seawater saturation state and surface area of the dissolving minerals. We have determined dissolution rates for two different abiotic calcite materials and three different grain sizes. Near-equilibrium dissolution rates are highly nonlinear, and are well normalized by geometric surface area, giving an empirical dissolution rate dependence on saturation state (Ω) of: This result substantiates the non-linear response of calcite dissolution to undersaturation. The bulk dissolution rate constant calculated here is in excellent agreement with those determined in far from equilibrium and dilute solution experiments. Plots of dissolution versus undersaturation indicates the presence of at least two dissolution mechanisms, implying a criticality in the calcite-seawater system. Finally, our new rate determination has implications for modeling of pelagic and seafloor dissolution. Nonlinear dissolution kinetics in a simple 1-D lysocline model indicate a possible transition from kinetic to diffusive control with increasing water depth, and also confirm the importance of respiration-driven dissolution in setting the shape of the calcite lysocline.

Sulfur degassing due to contact metamorphism during flood basalt eruptions

NASA Astrophysics Data System (ADS)

Yallup, Christine; Edmonds, Marie; Turchyn, Alexandra V.

2013-11-01

We present a study aimed at quantifying the potential for generating sulfur-rich gas emissions from the devolatilization of sediments accompanying sill emplacement during flood basalt eruptions. The potential contribution of sulfur-rich gases from sediments might augment substantially the magma-derived sulfur gases and hence impact regional and global climate. We demonstrate, from a detailed outcrop-scale study, that sulfur and total organic carbon have been devolatilized from shales immediately surrounding a 3-m thick dolerite sill on the Isle of Skye, Scotland. Localized partial melting occurred within a few centimetres of the contact in the shale, generating melt-filled cracks. Pyrite decomposed on heating within 80 cm of the contact, generating sulfur-rich gases (a mixture of H2S and SO2) and pyrrhotite. The pyrrhotite shows 32S enrichment, due to loss of 34S-enriched SO2. Further decomposition and oxidation of pyrrhotite resulted in hematite and/or magnetite within a few cm of the contact. Iron sulfates were produced during retrogressive cooling and oxidation within 20 cm of the contact. Decarbonation of the sediments due to heating is also observed, particularly along the upper contact of the sill, where increasing δ13C is consistent with loss of methane gas. The geochemical and mineralogical features observed in the shales are consistent with a short-lived intrusion, emplaced in <5 h. The dolerite magma contains pervasive pyrite and localized sulfur concentrations greater than the sulfur concentration at sulfide liquid saturation, consistent with addition of sulfur (perhaps from sediments) at a late stage. Our study provides evidence for desulfurization, as well as decarbonation, of shales adjacent to an igneous intrusion. The liberated fluids, rich in sulfur and carbon, are likely to be focused along regions of low pore fluid pressure along the margins of the sill. The sulfur gases liberated from the sediments would have augmented the sulfur dioxide (and hydrogen sulfide) yield of the eruption substantially, had they reached the surface. This enhancement of the magmatic sulfur budget has important implications for the climate impact of large flood basalt eruptions that erupt through thick, volatile-rich sedimentary sequences.

Experimental investigation of wood combustion in a fixed bed with hot air.

PubMed

Markovic, Miladin; Bramer, Eddy A; Brem, Gerrit

2014-01-01

Waste combustion on a grate with energy recovery is an important pillar of municipal solid waste (MSW) management in the Netherlands. In MSW incinerators fresh waste stacked on a grate enters the combustion chamber, heats up by radiation from the flame above the layer and ignition occurs. Typically, the reaction zone starts at the top of the waste layer and propagates downwards, producing heat for drying and devolatilization of the fresh waste below it until the ignition front reaches the grate. The control of this process is mainly based on empiricism. MSW is a highly inhomogeneous fuel with continuous fluctuating moisture content, heating value and chemical composition. The resulting process fluctuations may cause process control difficulties, fouling and corrosion issues, extra maintenance, and unplanned stops. In the new concept the fuel layer is ignited by means of preheated air (T>220 °C) from below without any external ignition source. As a result a combustion front will be formed close to the grate and will propagate upwards. That is why this approach is denoted by upward combustion. Experimental research has been carried out in a batch reactor with height of 4.55 m, an inner diameter of 200 mm and a fuel layer height up to 1m. Due to a high quality two-layer insulation adiabatic conditions can be assumed. The primary air can be preheated up to 350 °C, and the secondary air is distributed via nozzles above the waste layer. During the experiments, temperatures along the height of the reactor, gas composition and total weight decrease are continuously monitored. The influence of the primary air speed, fuel moisture and inert content on the combustion characteristics (ignition rate, combustion rate, ignition front speed and temperature of the reaction zone) is evaluated. The upward combustion concept decouples the drying, devolatilization and burnout phase. In this way the moisture and inert content of the waste have almost no influence on the combustion process. In this paper an experimental comparison between conventional and reversed combustion is presented. Copyright © 2013 Elsevier Ltd. All rights reserved.

Use of Mushroom Tyrosinase to Introduce Michaelis-Menten Enzyme Kinetics to Biochemistry Students

ERIC Educational Resources Information Center

Flurkey, William H.; Inlow, Jennifer K.

2017-01-01

An inexpensive enzyme kinetics laboratory exercise for undergraduate biochemistry students is described utilizing tyrosinase from white button mushrooms. The exercise can be completed in one or two three-hour lab sessions. The optimal amounts of enzyme, substrate (catechol), and inhibitor (kojic acid) are first determined, and then kinetic data is…

A new study of the kinetics of curd production in the process of cheese manufacture.

PubMed

Muñoz, Susana Vargas; Torres, Maykel González; Guerrero, Francisco Quintanilla; Talavera, Rogelio Rodríguez

2017-11-01

We studied the role played by temperature and rennet concentration in the coagulation process for cheese manufacture and the evaluation of their kinetics. We concluded that temperature is the main factor that determines the kinetics. The rennet concentration was unimportant probably due to the fast action of the enzyme chymosin. The Dynamic light scattering technique allowed measuring the aggregate's size and their formation kinetics. The volume fraction of solids was determined from viscosity measurements, showing profiles that are in agreement with the size profiles. The results indicate that the formation of the aggregates for rennet cheese is strongly dependent on temperature and rennet concentration. The results revealed that at 35·5 °C the volume fraction of solids has the maximum slope, indicating that at this temperature the curd is formed rapidly. The optimal temperature throughout the process was established. Second-order kinetics were obtained for the process. We observed a quadratic dependence between the rennet volume and the volume fraction of solids (curd), thereby indicating that the kinetics of the curd production should be of order two.

Thermal oxidative degradation kinetics of agricultural residues using distributed activation energy model and global kinetic model.

PubMed

Ren, Xiu'e; Chen, Jianbiao; Li, Gang; Wang, Yanhong; Lang, Xuemei; Fan, Shuanshi

2018-08-01

The study concerned the thermal oxidative degradation kinetics of agricultural residues, peanut shell (PS) and sunflower shell (SS). The thermal behaviors were evaluated via thermogravimetric analysis and the kinetic parameters were determined by using distributed activation energy model (DAEM) and global kinetic model (GKM). Results showed that thermal oxidative decomposition of two samples processed in three zones; the ignition, burnout, and comprehensive combustibility between two agricultural residues were of great difference; and the combustion performance could be improved by boosting heating rate. The activation energy ranges calculated by the DAEM for the thermal oxidative degradation of PS and SS were 88.94-145.30 kJ mol -1 and 94.86-169.18 kJ mol -1 , respectively. The activation energy obtained by the GKM for the oxidative decomposition of hemicellulose and cellulose was obviously lower than that for the lignin oxidation at identical heating rate. To some degree, the determined kinetic parameters could acceptably simulate experimental data. Copyright © 2018 Elsevier Ltd. All rights reserved.

Catalytic wet oxidation of phenol in a trickle bed reactor over a Pt/TiO2 catalyst.

PubMed

Maugans, Clayton B; Akgerman, Aydin

2003-01-01

Catalytic wet oxidation of phenol was studied in a batch and a trickle bed reactor using 4.45% Pt/TiO2 catalyst in the temperature range 150-205 degrees C. Kinetic data were obtained from batch reactor studies and used to model the reaction kinetics for phenol disappearance and for total organic carbon disappearance. Trickle bed experiments were then performed to generate data from a heterogeneous flow reactor. Catalyst deactivation was observed in the trickle bed reactor, although the exact cause was not determined. Deactivation was observed to linearly increase with the cumulative amount of phenol that had passed over the catalyst bed. Trickle bed reactor modeling was performed using a three-phase heterogeneous model. Model parameters were determined from literature correlations, batch derived kinetic data, and trickle bed derived catalyst deactivation data. The model equations were solved using orthogonal collocations on finite elements. Trickle bed performance was successfully predicted using the batch derived kinetic model and the three-phase reactor model. Thus, using the kinetics determined from limited data in the batch mode, it is possible to predict continuous flow multiphase reactor performance.

Topological and kinetic determinants of the modal matrices of dynamic models of metabolism

PubMed Central

2017-01-01

Large-scale kinetic models of metabolism are becoming increasingly comprehensive and accurate. A key challenge is to understand the biochemical basis of the dynamic properties of these models. Linear analysis methods are well-established as useful tools for characterizing the dynamic response of metabolic networks. Central to linear analysis methods are two key matrices: the Jacobian matrix (J) and the modal matrix (M-1) arising from its eigendecomposition. The modal matrix M-1 contains dynamically independent motions of the kinetic model near a reference state, and it is sparse in practice for metabolic networks. However, connecting the structure of M-1 to the kinetic properties of the underlying reactions is non-trivial. In this study, we analyze the relationship between J, M-1, and the kinetic properties of the underlying network for kinetic models of metabolism. Specifically, we describe the origin of mode sparsity structure based on features of the network stoichiometric matrix S and the reaction kinetic gradient matrix G. First, we show that due to the scaling of kinetic parameters in real networks, diagonal dominance occurs in a substantial fraction of the rows of J, resulting in simple modal structures with clear biological interpretations. Then, we show that more complicated modes originate from topologically-connected reactions that have similar reaction elasticities in G. These elasticities represent dynamic equilibrium balances within reactions and are key determinants of modal structure. The work presented should prove useful towards obtaining an understanding of the dynamics of kinetic models of metabolism, which are rooted in the network structure and the kinetic properties of reactions. PMID:29267329

Quantitative Förster resonance energy transfer analysis for kinetic determinations of SUMO-specific protease.

PubMed

Liu, Yan; Song, Yang; Madahar, Vipul; Liao, Jiayu

2012-03-01

Förster resonance energy transfer (FRET) technology has been widely used in biological and biomedical research, and it is a very powerful tool for elucidating protein interactions in either dynamic or steady state. SUMOylation (the process of SUMO [small ubiquitin-like modifier] conjugation to substrates) is an important posttranslational protein modification with critical roles in multiple biological processes. Conjugating SUMO to substrates requires an enzymatic cascade. Sentrin/SUMO-specific proteases (SENPs) act as an endopeptidase to process the pre-SUMO or as an isopeptidase to deconjugate SUMO from its substrate. To fully understand the roles of SENPs in the SUMOylation cycle, it is critical to understand their kinetics. Here, we report a novel development of a quantitative FRET-based protease assay for SENP1 kinetic parameter determination. The assay is based on the quantitative analysis of the FRET signal from the total fluorescent signal at acceptor emission wavelength, which consists of three components: donor (CyPet-SUMO1) emission, acceptor (YPet) emission, and FRET signal during the digestion process. Subsequently, we developed novel theoretical and experimental procedures to determine the kinetic parameters, k(cat), K(M), and catalytic efficiency (k(cat)/K(M)) of catalytic domain SENP1 toward pre-SUMO1. Importantly, the general principles of this quantitative FRET-based protease kinetic determination can be applied to other proteases. Copyright © 2011 Elsevier Inc. All rights reserved.

Assembly Kinetics Determine the Architecture of α-actinin Crosslinked F-actin Networks

PubMed Central

Falzone, Tobias T.; Lenz, Martin; Kovar, David R.; Gardel, Margaret L.

2013-01-01

The actin cytoskeleton is organized into diverse meshworks and bundles that support many aspects of cell physiology. Understanding the self-assembly of these actin-based structures is essential for developing predictive models of cytoskeletal organization. Here we show that the competing kinetics of bundle formation with the onset of dynamic arrest arising from filament entanglements and cross-linking determine the architecture of reconstituted actin networks formed with α-actinin cross-links. Cross-link mediated bundle formation only occurs in dilute solutions of highly mobile actin filaments. As actin polymerization proceeds, filament mobility and bundle formation are arrested concomitantly. By controlling the onset of dynamic arrest, perturbations to actin assembly kinetics dramatically alter the architecture of biochemically identical samples. Thus, the morphology of reconstituted F-actin networks is a kinetically determined structure similar to those formed by physical gels and glasses. These results establish mechanisms controlling the structure and mechanics in diverse semi-flexible biopolymer networks. PMID:22643888

Kinetics of electrolysis current reversal boriding of tool steels in a boron-containing oxychloride melt based on CaCl2

NASA Astrophysics Data System (ADS)

Chernov, Ya. B.; Filatov, E. S.

2017-08-01

The kinetics of thermal diffusion boriding in a melt based on calcium chloride with a boron oxide additive is studied using reversed current. The main temperature, concentration, and current parameters of the process are determined. The phase composition of the coating is determined by a metallographic method.

Steel Wool and Oxygen: A Look at Kinetics

ERIC Educational Resources Information Center

Gordon, James; Chancey, Katherine

2005-01-01

An experiment is demonstrated to determine the percentage of oxygen in air using a pretreated piece of steel wool, which is an alternative to spectroscopic kinetic analysis. Students are able to determine the order of reaction for oxygen in its reaction with the iron in steel wool, and are able to use the existing technology to collect and analyze…

Determination of in vivo RNA kinetics using RATE-seq.

PubMed

Neymotin, Benjamin; Athanasiadou, Rodoniki; Gresham, David

2014-10-01

The abundance of a transcript is determined by its rate of synthesis and its rate of degradation; however, global methods for quantifying RNA abundance cannot distinguish variation in these two processes. Here, we introduce RNA approach to equilibrium sequencing (RATE-seq), which uses in vivo metabolic labeling of RNA and approach to equilibrium kinetics, to determine absolute RNA degradation and synthesis rates. RATE-seq does not disturb cellular physiology, uses straightforward normalization with exogenous spike-ins, and can be readily adapted for studies in most organisms. We demonstrate the use of RATE-seq to estimate genome-wide kinetic parameters for coding and noncoding transcripts in Saccharomyces cerevisiae. © 2014 Neymotin et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Kinetics of the creatine kinase reaction in neonatal rabbit heart: An empirical analysis of the rate equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

McAuliffe, J.J.; Perry, S.B.; Brooks, E.E.

1991-03-12

Here the authors define the kinetics of the creatine kinase (CK) reaction in an intact mammalian heart containing the full rnage of CK isoenzymes. Previously derived kinetic constants were refit for the reaction occurring at 37C. Steady-state metabolite concentrations from {sup 31}P NMR and standard biochemical techniques were determined. {sup 31}P magnetization transfer data were obtained to determine unidirectional creatine kinase fluxes in hearts with differing total creatine contents and differing mitochondrial CK activities during KCl arrest and isovolumic work for both the forward reaction (MgATP synthesis) and reverse reaction (phosphocreatine synthesis). The NMR kinetic data and substrate concentrations datamore » were used in conjunction with a kinetic model based on MM-CK in solution to determine the applicability of the solution-based kinetic models to the CK kinetics of the intact heart. The results indicated that no single set of rate equation constants could describe both the KCl-arrested and working hearts. Analysis of the results indicated that the CK reaction is rate limited in the direction of ATP synthesis, the size of the guanidino substrate pool drives the measured CK flux in the intact heart, and during isovolumic work, the CK reaction operates under saturating conditions; that is, the substrate concentrations are at least 2-fold greater than the K{sub m} or K{sub im} for each substrate. However, during KCl arrest the reaction does not operate under saturating conditions and the CK reaction velocity is strongly influenced by the guanidino substrate pool size.« less

Efficient Generation of Chemiluminescence during the reduction of manganese(IV) ions with lactic acid

NASA Astrophysics Data System (ADS)

Tsaplev, Yu. B.

2016-12-01

The kinetics and mechanism of chemiluminescence during the reduction of manganese(IV) ions with lactic acid in an H2SO4-AcOH medium are studied. Kinetic spectrophotometric measurements are used to determine the profiles of change in the concentrations of Mn(IV) and Mn(III) ions during the reaction. The results from kinetic spectrophotometric measurements are compared to the light yield kinetics. The quantum chemiluminescence and chemiexcitation yields reach record values.

Determination of thermophysical characteristics of vulcanizable rubber products by the mathematical modeling method

NASA Astrophysics Data System (ADS)

Tikhomirov, S. G.; Pyatakov, Y. V.; Karmanova, O. V.; Maslov, A. A.

2018-03-01

The studies of the vulcanization kinetics of elastomers were carried out using a Truck tyre tread rubber compound. The formal kinetic scheme of vulcanization of rubbers sulfur-accelerator curing system was used which generalizes the set of reactions occurring in the curing process. A mathematical model is developed for determining the thermal parameters vulcanizable mixture comprising algorithms for solving direct and inverse problems for system of equations of heat conduction and kinetics of the curing process. The performance of the model is confirmed by the results of numerical experiments on model examples.

Devolatilization Studies of Oil Palm Biomass for Torrefaction Process through Scanning Electron Microscopy

NASA Astrophysics Data System (ADS)

Daud, D.; Abd. Rahman, A.; Shamsuddin, A. H.

2016-03-01

In this work, palm oil biomass consisting of empty fruit bunch (EFB), mesocarp fibre and palm kernel shell (PKS) were chosen as raw material for torrefaction process. Torrefaction process was conducted at various temperatures of 240 °C, 270 °C and 300 °C with a residence time of 60 minutes. The morphology of the raw and torrefied biomass was then observed through Scanning Electron Microscopy (SEM) images. Also, through this experiment the correlation between the torrefaction temperatures with the volatile gases released were studied. From the observation, the morphology structure of the biomass exhibited inter-particle gaps due to the release of volatile gases and it is obviously seen more at higher temperatures. Moreover, the change of the biomass structure is influenced by the alteration of the lignocellulose biomass.

Kinetics of Hydrolysis of Acetic Anhydride by In-Situ FTIR Spectroscopy: An Experiment for the Undergraduate Laboratory

ERIC Educational Resources Information Center

Haji, Shaker; Erkey, Can

2005-01-01

A reaction kinetics experiment for the chemical engineering undergraduate laboratory course was developed in which in-situ Fourier Transfer Infrared spectroscopy was used to measure reactant and product concentrations. The kinetics of the hydrolysis of acetic anhydride was determined by experiments carried out in a batch reactor. The results…

Improvement of Student Understanding of How Kinetic Data Facilitates the Determination of Amino Acid Catalytic Function through an Alkaline Phosphatase Structure/Mechanism Bioinformatics Exercise

ERIC Educational Resources Information Center

Grunwald, Sandra K.; Krueger, Katherine J.

2008-01-01

Laboratory exercises, which utilize alkaline phosphatase as a model enzyme, have been developed and used extensively in undergraduate biochemistry courses to illustrate enzyme steady-state kinetics. A bioinformatics laboratory exercise for the biochemistry laboratory, which complements the traditional alkaline phosphatase kinetics exercise, was…

Second-order kinetic model for the sorption of cadmium onto tree fern: a comparison of linear and non-linear methods.

PubMed

Ho, Yuh-Shan

2006-01-01

A comparison was made of the linear least-squares method and a trial-and-error non-linear method of the widely used pseudo-second-order kinetic model for the sorption of cadmium onto ground-up tree fern. Four pseudo-second-order kinetic linear equations are discussed. Kinetic parameters obtained from the four kinetic linear equations using the linear method differed but they were the same when using the non-linear method. A type 1 pseudo-second-order linear kinetic model has the highest coefficient of determination. Results show that the non-linear method may be a better way to obtain the desired parameters.

Simplified Two-Time Step Method for Calculating Combustion and Emission Rates of Jet-A and Methane Fuel With and Without Water Injection

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2005-01-01

A simplified kinetic scheme for Jet-A, and methane fuels with water injection was developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) or even simple FORTRAN codes. The two time step method is either an initial time averaged value (step one) or an instantaneous value (step two). The switch is based on the water concentration in moles/cc of 1x10(exp -20). The results presented here results in a correlation that gives the chemical kinetic time as two separate functions. This two time step method is used as opposed to a one step time averaged method previously developed to determine the chemical kinetic time with increased accuracy. The first time averaged step is used at the initial times for smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, initial water to fuel mass ratio, temperature, and pressure. The second instantaneous step, to be used with higher water concentrations, gives the chemical kinetic time as a function of instantaneous fuel and water mole concentration, pressure and temperature (T4). The simple correlations would then be compared to the turbulent mixing times to determine the limiting rates of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide and NOx are obtained for Jet-A fuel and methane with and without water injection to water mass loadings of 2/1 water to fuel. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentrations of carbon monoxide and nitrogen oxide as functions of overall equivalence ratio, water to fuel mass ratio, pressure and temperature (T3). The temperature of the gas entering the turbine (T4) was also correlated as a function of the initial combustor temperature (T3), equivalence ratio, water to fuel mass ratio, and pressure.

Human kinetics of orally and intravenously administered low-dose 1,2-(13)C-dichloroacetate.

PubMed

Jia, Minghong; Coats, Bonnie; Chadha, Monisha; Frentzen, Barbara; Perez-Rodriguez, Javier; Chadik, Paul A; Yost, Richard A; Henderson, George N; Stacpoole, Peter W

2006-12-01

Dichloroacetate (DCA) is a putative environmental hazard, owing to its ubiquitous presence in the biosphere and its association with animal and human toxicity. We sought to determine the kinetics of environmentally relevant concentrations of 1,2-(13)C-DCA administered to healthy adults. Subjects received an oral or intravenous dose of 2.5 microg/kg of 1,2-(13)C-DCA. Plasma and urine concentrations of 1,2-(13)C-DCA were measured by a modified gas chromatography-tandem mass spectrometry method. 1,2-(13)C-DCA kinetics was determined by modeling using WinNonlin 4.1 software. Plasma concentrations of 1,2-(13)C-DCA peaked 10 minutes and 30 minutes after intravenous or oral administration, respectively. Plasma kinetic parameters varied as a function of dose and duration. Very little unchanged 1,2-(13)C-DCA was excreted in urine. Trace amounts of DCA alter its own kinetics after short-term exposure. These findings have important implications for interpreting the impact of this xenobiotic on human health.

Development of an ESI-LC-MS-based assay for kinetic evaluation of Mycobacterium tuberculosis shikimate kinase activity and inhibition.

PubMed

Simithy, Johayra; Gill, Gobind; Wang, Yu; Goodwin, Douglas C; Calderón, Angela I

2015-02-17

A simple and reliable liquid chromatography-mass spectrometry (LC-MS) assay has been developed and validated for the kinetic characterization and evaluation of inhibitors of shikimate kinase from Mycobacterium tuberculosis (MtSK), a potential target for the development of novel antitubercular drugs. This assay is based on the direct determination of the reaction product shikimate-3-phosphate (S3P) using electrospray ionization (ESI) and a quadrupole time-of-flight (Q-TOF) detector. A comparative analysis of the kinetic parameters of MtSK obtained by the LC-MS assay with those obtained by a conventional UV-assay was performed. Kinetic parameters determined by LC-MS were in excellent agreement with those obtained from the UV assay, demonstrating the accuracy, and reliability of this method. The validated assay was successfully applied to the kinetic characterization of a known inhibitor of shikimate kinase; inhibition constants and mode of inhibition were accurately delineated with LC-MS.

Oil-generation kinetics for organic facies with Type-II and -IIS kerogen in the Menilite Shales of the Polish Carpathians

USGS Publications Warehouse

Lewan, M.D.; Kotarba, M.J.; Curtis, John B.; Wieclaw, D.; Kosakowski, P.

2006-01-01

The Menilite Shales (Oligocene) of the Polish Carpathians are the source of low-sulfur oils in the thrust belt and some high-sulfur oils in the Carpathian Foredeep. These oil occurrences indicate that the high-sulfur oils in the Foredeep were generated and expelled before major thrusting and the low-sulfur oils in the thrust belt were generated and expelled during or after major thrusting. Two distinct organic facies have been observed in the Menilite Shales. One organic facies has a high clastic sediment input and contains Type-II kerogen. The other organic facies has a lower clastic sediment input and contains Type-IIS kerogen. Representative samples of both organic facies were used to determine kinetic parameters for immiscible oil generation by isothermal hydrous pyrolysis and S2 generation by non-isothermal open-system pyrolysis. The derived kinetic parameters showed that timing of S2 generation was not as different between the Type-IIS and -II kerogen based on open-system pyrolysis as compared with immiscible oil generation based on hydrous pyrolysis. Applying these kinetic parameters to a burial history in the Skole unit showed that some expelled oil would have been generated from the organic facies with Type-IIS kerogen before major thrusting with the hydrous-pyrolysis kinetic parameters but not with the open-system pyrolysis kinetic parameters. The inability of open-system pyrolysis to determine earlier petroleum generation from Type-IIS kerogen is attributed to the large polar-rich bitumen component in S2 generation, rapid loss of sulfur free-radical initiators in the open system, and diminished radical selectivity and rate constant differences at higher temperatures. Hydrous-pyrolysis kinetic parameters are determined in the presence of water at lower temperatures in a closed system, which allows differentiation of bitumen and oil generation, interaction of free-radical initiators, greater radical selectivity, and more distinguishable rate constants as would occur during natural maturation. Kinetic parameters derived from hydrous pyrolysis show good correlations with one another (compensation effect) and kerogen organic-sulfur contents. These correlations allow for indirect determination of hydrous-pyrolysis kinetic parameters on the basis of the organic-sulfur mole fraction of an immature Type-II or -IIS kerogen. ?? 2006 Elsevier Inc. All rights reserved.

Determination of chlorine in atmosphere by kinetic spectrophotometry.

PubMed

Meng, Jian-Xin; Wang, Xiao-Bo; Ruan, Ge-Lan; Li, Guo-Qiang; Deng, Zhao-Xia

2005-03-01

A kinetic method for determination of chlorine in air was described in the present work. The method based on fading of methyl orange (MO) containing solution in air absorption process. A determination limit of 2.64 microg L(-1) was found. With the present method, chlorine concentration could be determined in several minutes with convenient manipulation. As concentration variation of methyl orange in the absorption solution did not affect the experimental results, fabrication and preservation of the stock absorption is also convenient. The present method is promising in monitoring chlorine concentration in atmosphere.

Determination of chlorine in atmosphere by kinetic spectrophotometry

NASA Astrophysics Data System (ADS)

Meng, Jian-Xin; Wang, Xiao-Bo; Ruan, Ge-Lan; Li, Guo-Qiang; Deng, Zhao-Xia

2005-03-01

A kinetic method for determination of chlorine in air was described in the present work. The method based on fading of methyl orange (MO) containing solution in air absorption process. A determination limit of 2.64 μg L -1 was found. With the present method, chlorine concentration could be determined in several minutes with convenient manipulation. As concentration variation of methyl orange in the absorption solution did not affect the experimental results, fabrication and preservation of the stock absorption is also convenient. The present method is promising in monitoring chlorine concentration in atmosphere.

Liquefaction chemistry and kinetics: Hydrogen utilization studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rothenberger, K.S.; Warzinski, R.P.; Cugini, A.V.

1995-12-31

The objectives of this project are to investigate the chemistry and kinetics that occur in the initial stages of coal liquefaction and to determine the effects of hydrogen pressure, catalyst activity, and solvent type on the quantity and quality of the products produced. The project comprises three tasks: (1) preconversion chemistry and kinetics, (2) hydrogen utilization studies, and (3) assessment of kinetic models for liquefaction. The hydrogen utilization studies work will be the main topic of this report. However, the other tasks are briefly described.

Mathematical Description Development of Reactions of Metallic Gallium Using Kinetic Block Diagram

NASA Astrophysics Data System (ADS)

Yakovleva, A. A.; Soboleva, V. G.; Filatova, E. G.

2018-05-01

A kinetic block diagram based on a logical sequence of actions in the mathematical processing of a kinetic data is used. A type of reactions of metallic gallium in hydrochloric acid solutions is determined. It has been established that the reactions of the formation of gallium oxide and its salts proceed independently and in the absence of the diffusion resistance. Kinetic models connecting the constants of the reaction rate with the activation energy and describing the evolution of the process are obtained.

Study on the pulse reaction technique. VI. Kinetics of the reaction of NO with NH/sub 3/ on a V/sub 2/O/sub 5/ catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyamoto, A.; Yamazaki, Y.; Hattori, T.

1982-01-01

In order to examine the applicability of the rectangular pulse technique to the determination of the kinetics of a two-components' reaction on a catalyst in the specified surface state, the kinetics of the reaction of NO with NH/sub 3/ on the V/sub 2/O/sub 5/ catalyst, that is, NO + NH/sub 3/ + VVertical BarO ..-->.. N/sub 2/ + H/sub 2/O + V-OH, has been investigated using the rectangular pulse apparatus. Chromatograms of the individual components have shown that NH/sub 3/ is strongly adsorbed on the catalyst while NO or N/sub 2/ is not or only very weakly adsorbed. The adsorptionmore » of NH/sub 3/ has been approximately described by the Langmuir adsorption isotherm. The yield of N/sub 2/ produced by the reaction has changed significantly with the pusle width. This indicates a separation of NO and NH/sub 3/ in the catalyst bed during the pulse experiments. By analyzing the experimental data with the theory of the pulse technique, the kinetics of the above-mentioned two-components' reaction has successfully been determined and it has agreed with the kinetics of the reaction of NO with NH/sub 3/ under excess oxygen conditions determined by using the continuous flow technique. On the basis of these results, the rectangular pulse technique coupled with the theoretical analsysis of the experimental data has been concluded to be a method effective for the determination of the kinetics of a multicomponents' reaction on a catalyst in the specified surface state.« less

Determination of the Effects of Medium Composition on the Monochloramine Disinfection Kinetics of Nitrosomonas europaea by the Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods

EPA Science Inventory

Various media compositions (phosphate 1-50 mM; ionic strength 2.8-150 meq/L) significantly affected Nitrosomonas europaea monochloramine disinfection kinetics determined by Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR) methods (lag coefficient 37-490...

Simplified Two-Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydorgen/Oxygen

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2005-01-01

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two-time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (> 1 x 10(exp -20) moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/air fuel and for the H2/O2. A similar correlation is also developed using data from NASA s Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). High values of the regression coefficient R2 are obtained.

Summary of Simplified Two Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/Oxygen

NASA Technical Reports Server (NTRS)

Marek, C. John; Molnar, Melissa

2005-01-01

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (greater than l x 10(exp -20)) moles per cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T(sub 4)). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/Air fuel and for H2/O2. A similar correlation is also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T(sub 4)) as a function of overall fuel/air ratio, pressure and initial temperature (T(sub 3)). High values of the regression coefficient R squared are obtained.

Kinetic constrained optimization of the golf swing hub path.

PubMed

Nesbit, Steven M; McGinnis, Ryan S

2014-12-01

This study details an optimization of the golf swing, where the hand path and club angular trajectories are manipulated. The optimization goal was to maximize club head velocity at impact within the interaction kinetic limitations (force, torque, work, and power) of the golfer as determined through the analysis of a typical swing using a two-dimensional dynamic model. The study was applied to four subjects with diverse swing capabilities and styles. It was determined that it is possible for all subjects to increase their club head velocity at impact within their respective kinetic limitations through combined modifications to their respective hand path and club angular trajectories. The manner of the modifications, the degree of velocity improvement, the amount of kinetic reduction, and the associated kinetic limitation quantities were subject dependent. By artificially minimizing selected kinetic inputs within the optimization algorithm, it was possible to identify swing trajectory characteristics that indicated relative kinetic weaknesses of a subject. Practical implications are offered based upon the findings of the study. Key PointsThe hand path trajectory is an important characteristic of the golf swing and greatly affects club head velocity and golfer/club energy transfer.It is possible to increase the energy transfer from the golfer to the club by modifying the hand path and swing trajectories without increasing the kinetic output demands on the golfer.It is possible to identify relative kinetic output strengths and weakness of a golfer through assessment of the hand path and swing trajectories.Increasing any one of the kinetic outputs of the golfer can potentially increase the club head velocity at impact.The hand path trajectory has important influences over the club swing trajectory.

Kinetic Constrained Optimization of the Golf Swing Hub Path

PubMed Central

Nesbit, Steven M.; McGinnis, Ryan S.

2014-01-01

This study details an optimization of the golf swing, where the hand path and club angular trajectories are manipulated. The optimization goal was to maximize club head velocity at impact within the interaction kinetic limitations (force, torque, work, and power) of the golfer as determined through the analysis of a typical swing using a two-dimensional dynamic model. The study was applied to four subjects with diverse swing capabilities and styles. It was determined that it is possible for all subjects to increase their club head velocity at impact within their respective kinetic limitations through combined modifications to their respective hand path and club angular trajectories. The manner of the modifications, the degree of velocity improvement, the amount of kinetic reduction, and the associated kinetic limitation quantities were subject dependent. By artificially minimizing selected kinetic inputs within the optimization algorithm, it was possible to identify swing trajectory characteristics that indicated relative kinetic weaknesses of a subject. Practical implications are offered based upon the findings of the study. Key Points The hand path trajectory is an important characteristic of the golf swing and greatly affects club head velocity and golfer/club energy transfer. It is possible to increase the energy transfer from the golfer to the club by modifying the hand path and swing trajectories without increasing the kinetic output demands on the golfer. It is possible to identify relative kinetic output strengths and weakness of a golfer through assessment of the hand path and swing trajectories. Increasing any one of the kinetic outputs of the golfer can potentially increase the club head velocity at impact. The hand path trajectory has important influences over the club swing trajectory. PMID:25435779

Hydromechanical Modeling of Fluid Flow in the Lower Crust

NASA Astrophysics Data System (ADS)

Connolly, J.

2011-12-01

The lower crust lies within an ambiguous rheological regime between the brittle upper crust and ductile sub-lithospheric mantle. This ambiguity has allowed two schools of thought to develop concerning the nature of fluid flow in the lower crust. The classical school holds that lower crustal rocks are inviscid and that any fluid generated by metamorphic devolatilization is squeezed out of rocks as rapidly as it is produced. According to this school, permeability is a dynamic property and fluid flow is upward. In contrast, the modern school uses concepts from upper crustal hydrology that presume implicitly, if not explicitly, that rocks are rigid or, at most, brittle. For the modern school, the details of crustal permeability determine fluid flow and as these details are poorly known almost anything is possible. Reality, to the extent that it is reflected by inference from field studies, offers some support to both schools. In particular, evidence of significant lateral and channelized fluid flow are consistent with flow in rigid media, while evidence for short (104 - 105 y) grain-scale fluid-rock interaction during much longer metamorphic events, suggests that reaction-generated grain-scale permeability is sealed rapidly by compaction; a phenomenon that is also essential to prevent extensive retrograde metamorphism. These observations provide a compelling argument for recognizing in conceptual models of lower crustal fluid flow that rocks are neither inviscid nor rigid, but compact by viscous mechanisms on a finite time-scale. This presentation will review the principle consequences of, and obstacles to, incorporating compaction in such models. The role of viscous compaction in the lower crust is extraordinarily uncertain, but ignoring this uncertainty in models of lower crustal fluid flow does not make the models any more certain. Models inevitably invoke an initial steady state hydraulic regime. This initial steady state is critical to model outcomes because it determines the compaction time and length scales and, thereby, the response of the system to perturbations. Unfortunately, because metamorphic devolatilization is the most probable source of lower crustal fluids, the assumption of an initial steady state leaves much to be desired. In truth, in the modeling of lower crustal fluid flow, less is known about the initial state than is known about possible perturbations to it, e.g., metamorphic fluid production. Compaction is a bad and good news story. The bad news is that local flow patterns may be influenced by unknowable details; the good news is that compaction-driven fluid flow has a tendency to self-organize. Self-organization eliminates the dependence on details that are present on spatial or temporal scales that are smaller than the compaction length and time scales. Porosity waves are the mechanism for this self-organization, through which dilational deformation is localized in time and space to create pathways for fluid expulsion. The resulting flow patterns are sensitive to material properties and initial state, thus, inversion of natural flow patterns offers the greatest hope for constraining the compaction scales. Knowledge of these scales is also important because they limit the influence of external forcings on flow patterns, e.g., a shear zone may induce lateral or downward fluid flow, but only on the compaction time and length scales.

Kinetic model of water vapour adsorption by gluten-free starch

NASA Astrophysics Data System (ADS)

Ocieczek, Aneta; Kostek, Robert; Ruszkowska, Millena

2015-01-01

This study evaluated the kinetics of water vapour adsorption on the surface of starch molecules derived from wheat. The aim of the study was to determine an equation that would allow estimation of water content in tested material in any timepoint of the adsorption process aimed at settling a balance with the environment. An adsorption isotherm of water vapour on starch granules was drawn. The parameters of the Guggenheim, Anderson, and De Boer equation were determined by characterizing the tested product and adsorption process. The equation of kinetics of water vapour adsorption on the surface of starch was determined based on the Guggenheim, Anderson, and De Boer model describing the state of equilibrium and on the model of a first-order linear inert element describing the changes in water content over time.

Inactivation disinfection property of Moringa Oleifera seed extract: optimization and kinetic studies

NASA Astrophysics Data System (ADS)

Idris, M. A.; Jami, M. S.; Hammed, A. M.

2017-05-01

This paper presents the statistical optimization study of disinfection inactivation parameters of defatted Moringa oleifera seed extract on Pseudomonas aeruginosa bacterial cells. Three level factorial design was used to estimate the optimum range and the kinetics of the inactivation process was also carried. The inactivation process involved comparing different disinfection models of Chicks-Watson, Collins-Selleck and Homs models. The results from analysis of variance (ANOVA) of the statistical optimization process revealed that only contact time was significant. The optimum disinfection range of the seed extract was 125 mg/L, 30 minutes and 120rpm agitation. At the optimum dose, the inactivation kinetics followed the Collin-Selleck model with coefficient of determination (R2) of 0.6320. This study is the first of its kind in determining the inactivation kinetics of pseudomonas aeruginosa using the defatted seed extract.

Elucidation of the naproxen sodium adsorption onto activated carbon prepared from waste apricot: kinetic, equilibrium and thermodynamic characterization.

PubMed

Onal, Y; Akmil-Başar, C; Sarici-Ozdemir, C

2007-09-30

In this study, activated carbon (WA11Zn5) was prepared from waste apricot, which is waste in apricot plants in Malatya, by chemical activation with ZnCl(2). BET surface area of activated carbon is determined as 1060 m(2)/g. The ability of WA11Zn5, to remove naproxen sodium from effluent solutions by adsorption has been studied. Equilibrium isotherms for the adsorption of naproxen sodium on activated carbon were measured experimentally. Results were analyzed by the Langmiur, Freundlich equation using linearized correlation coefficient at 298 K. The characteristic parameters for each isotherm have been determined. Langmiur equation is found to best represent the equilibrium data for naproxen sodium-WA11Zn5 systems. The monolayer adsorption capacity of WA11Zn5 for naproxen sodium was found to be 106.38 mg/g at 298 K. The process was favorable and spontaneous. The kinetics of adsorption of naproxen sodium have been discussed using three kinetic models, i.e., the pseudo first-order model, the pseudo second-order model, the intraparticle diffusion model. Kinetic parameters and correlation coefficients were determined. It was shown that the pseudo second-order kinetic equation could describe the adsorption kinetics for naproxen sodium onto WA11Zn5. The thermodynamic parameters, such as DeltaG degrees , DeltaS degrees and DeltaH degrees, were calculated. The thermodynamics of naproxen sodium-WA11Zn5 system indicates endothermic process.

Effect of biochar particle size on hydrophobic organic compound sorption kinetics: Applicability of using representative size.

PubMed

Kang, Seju; Jung, Jihyeun; Choe, Jong Kwon; Ok, Yong Sik; Choi, Yongju

2018-04-01

Particle size of biochar may strongly affect the kinetics of hydrophobic organic compound (HOC) sorption. However, challenges exist in characterizing the effect of biochar particle size on the sorption kinetics because of the wide size range of biochar. The present study suggests a novel method to determine a representative value that can be used to show the dependence of HOC sorption kinetics to biochar particle size on the basis of an intra-particle diffusion model. Biochars derived from three different feedstocks are ground and sieved to obtain three daughter products each having different size distributions. Phenanthrene sorption kinetics to the biochars are well described by the intra-particle diffusion model with significantly greater sorption rates observed for finer grained biochars. The time to reach 95% of equilibrium for phenanthrene sorption to biochar is reduced from 4.6-17.9days for the original biochars to <1-4.6days for the powdered biochars with <125μm in size. A moderate linear correlation is found between the inverse square of the representative biochar particle radius obtained using particle size distribution analysis and the apparent phenanthrene sorption rates determined by the sorption kinetics experiments and normalized to account for the variation of the sorption rate-determining factors other than the biochar particle radius. The results suggest that the representative biochar particle radius reasonably describes the dependence of HOC sorption rates on biochar particle size. Copyright © 2017 Elsevier B.V. All rights reserved.

Permeabilization Activated Reduction in Fluorescence (PARF): a novel method to measure kinetics of protein interactions with intracellular structures

PubMed Central

Singh, Pali P.; Hawthorne, Jenci L.; Davis, Christie A.; Quintero, Omar A.

2016-01-01

Understanding kinetic information is fundamental in understanding biological function. Advanced imaging technologies have fostered the development of kinetic analyses in cells. We have developed Permeabilization Activated Reduction in Fluorescence (PARF) analysis for determination of apparent t1/2 and immobile fraction, describing the dissociation of a protein of interest from intracellular structures. To create conditions where dissociation events are observable, cells expressing a fluorescently-tagged protein are permeabilized with digitonin, diluting the unbound protein into the extracellular media. As the media volume is much larger than the cytosolic volume, the concentration of the unbound pool decreases drastically, shifting the system out of equilibrium--favoring dissociation events. Loss of bound protein is observed as loss of fluorescence from intracellular structures and can be fit to an exponential decay. We compared PARF dissociation kinetics with previously published equilibrium kinetics as determined by FRAP. PARF dissociation rates agreed with the equilibrium-based FRAP analysis predictions of the magnitude of those rates. When used to investigate binding kinetics of a panel of cytoskeletal proteins, PARF analysis revealed that filament stabilization resulted in slower fluorescence loss. Additionally, commonly used “general” F-actin labels display differences in kinetic properties, suggesting that not all fluorescently-tagged actin labels interact with the actin network in the same way. We also observed differential dissociation kinetics for GFP-VASP depending on which cellular structure was being labeled. These results demonstrate that PARF analysis of non-equilibrium systems reveals kinetic information without the infrastructure investment required for other quantitative approaches such as FRAP, photoactivation, or in vitro reconstitution assays. PMID:27126922

Learning Chemistry from Good and (Why Not?) Problematic Results: Kinetics of the pH-Independent Hydrolysis of 4-Nitrophenyl Chloroformate

ERIC Educational Resources Information Center

El Seoud, Omar A.; Galgano, Paula D.; Are^as, Elizabeth P. G.; Moraes, Jamille M.

2015-01-01

The determination of kinetic data is central to reaction mechanism; science courses usually include experiments on chemical kinetics. Thanks to PC-controlled data acquisition and availability of software, the students calculate rate constants, whether the experiment has been done properly or not. This contrasts with their experience in, e.g.,…

Enzyme Kinetics Experiment with the Multienzyme Complex Viscozyme L and Two Substrates for the Accurate Determination of Michaelian Parameters

ERIC Educational Resources Information Center

Guerra, Nelson Pérez

2017-01-01

A laboratory experiment in which students study the kinetics of the Viscozyme-L-catalyzed hydrolysis of cellulose and starch comparatively was designed for an upper-division biochemistry laboratory. The main objective of this experiment was to provide an opportunity to perform enhanced enzyme kinetics data analysis using appropriate informatics…

Kinetic modeling and fitting software for interconnected reaction schemes: VisKin.

PubMed

Zhang, Xuan; Andrews, Jared N; Pedersen, Steen E

2007-02-15

Reaction kinetics for complex, highly interconnected kinetic schemes are modeled using analytical solutions to a system of ordinary differential equations. The algorithm employs standard linear algebra methods that are implemented using MatLab functions in a Visual Basic interface. A graphical user interface for simple entry of reaction schemes facilitates comparison of a variety of reaction schemes. To ensure microscopic balance, graph theory algorithms are used to determine violations of thermodynamic cycle constraints. Analytical solutions based on linear differential equations result in fast comparisons of first order kinetic rates and amplitudes as a function of changing ligand concentrations. For analysis of higher order kinetics, we also implemented a solution using numerical integration. To determine rate constants from experimental data, fitting algorithms that adjust rate constants to fit the model to imported data were implemented using the Levenberg-Marquardt algorithm or using Broyden-Fletcher-Goldfarb-Shanno methods. We have included the ability to carry out global fitting of data sets obtained at varying ligand concentrations. These tools are combined in a single package, which we have dubbed VisKin, to guide and analyze kinetic experiments. The software is available online for use on PCs.

Probing Aluminum Reactions in Combustion and Explosion Via the Kinetic Isotope Effect

NASA Astrophysics Data System (ADS)

Tappan, Bryce

2015-06-01

The mechanism that controls the reaction speed of aluminum in explosion and combustion is poorly understood, and experimentally difficult to measure. Recently, work in our laboratory has demonstrated that during the combustion of nanoparticulate aluminum with H2O or D2O, different reaction rates due to the kinetic isotope effect are observed. This result is the first-ever observed kinetic isotope effect in a metal combustion reaction and verifies that chemical reaction kinetics play a major role in determining the global burning rate. During or shortly after a detonation, however, the reaction rates are dramatically faster and the physical mechanism controlling Al reaction is likely different than during combustion events. To utilize the kinetic isotope effect to probe Al reactions in detonation, formulations were produced that contain powdered Al in deuterated high explosives and high-fidelity detonation velocity were determined along with PDV measurements to observe early wall velocity expansion measurements. The JWL equation of state was solved to determine temperature, pressure and energies at specific time periods, in addition of Gurney energies, which enables the elucidation of Al reaction extent. By comparison of the Al oxidation with LiF, data indicate that Al oxidation occurs on an extremely fast time scale and isotope effects in both the HE detonation and post-detonation Al reactions are discussed.

The influence of non-ionisable excipients on precipitation parameters measured using the CheqSol method.

PubMed

Etherson, Kelly; Halbert, Gavin; Elliott, Moira

2016-09-01

The aim of this study was to determine the influence of non-ionisable excipients hydroxypropyl-β-cyclodextrin (HPβCD) and poloxamers 407 and 188 on the supersaturation and precipitation kinetics of ibuprofen, gliclazide, propranolol and atenolol induced through solution pH shifts using the CheqSol method. The drug's kinetic and intrinsic aqueous solubilities were measured in the presence of increasing excipient concentrations using the CheqSol method. Experimental data rate of change of pH with time was also examined to determine excipient-induced parachute effects and influence on precipitation rates. The measured kinetic and intrinsic solubilities provide a determination of the influence of each excipient on supersaturation index, and the area under the CheqSol curve can measure the parachute capability of excipients. The excipients influence on precipitation kinetics can be measured with novel parameters; for example, the precipitation pH or percentage ionised drug at the precipitation point, which provide further information on the excipient-induced changes in precipitation performance. This method can therefore be employed to measure the influence of non-ionisable excipients on the kinetic solubility behaviour of supersaturated solutions of ionisable drugs and to provide data, which discriminates between excipient systems during precipitation. © 2016 Royal Pharmaceutical Society.

Chemiomics: network reconstruction and kinetics of port wine aging.

PubMed

Monforte, Ana Rita; Jacobson, Dan; Silva Ferreira, A C

2015-03-11

Network reconstruction (NR) has proven to be useful in the detection and visualization of relationships among the compounds present in a Port wine aging data set. This view of the data provides a considerable amount of information with which to understand the kinetic contexts of the molecules represented by peaks in each chromatogram. The aim of this study was to use NR together with the determination of kinetic parameters to extract more information about the mechanisms involved in Port wine aging. The volatile compounds present in samples of Port wines spanning 128 years in age were measured with the use of GC-MS. After chromatogram alignment, a peak matrix was created, and all peak vectors were compared to one another to determine their Pearson correlations over time. A correlation network was created and filtered on the basis of the resulting correlation values. Some nodes in the network were further studied in experiments on Port wines stored under different conditions of oxygen and temperature in order to determine their kinetic parameters. The resulting network can be divided into three main branches. The first branch is related to compounds that do not directly correlate to age, the second branch contains compounds affected by temperature, and the third branch contains compounds associated with oxygen. Compounds clustered in the same branch of the network have similar expression patterns over time as well as the same kinetic order, thus are likely to be dependent on the same technological parameters. Network construction and visualization provides more information with which to understand the probable kinetic contexts of the molecules represented by peaks in each chromatogram. The approach described here is a powerful tool for the study of mechanisms and kinetics in complex systems and should aid in the understanding and monitoring of wine quality.

Kinetic analysis of interactions of paraoxon and oximes with human, Rhesus monkey, swine, rabbit, rat and guinea pig acetylcholinesterase.

PubMed

Worek, Franz; Aurbek, Nadine; Wille, Timo; Eyer, Peter; Thiermann, Horst

2011-01-15

Previous in vitro studies showed marked species differences in the reactivating efficiency of oximes between human and animal acetylcholinesterase (AChE) inhibited by organophosphorus (OP) nerve agents. These findings provoked the present in vitro study which was designed to determine the inhibition, aging, spontaneous and oxime-induced reactivation kinetics of the pesticide paraoxon, serving as a model compound for diethyl-OP, and the oximes obidoxime, pralidoxime, HI 6 and MMB-4 with human, Rhesus monkey, swine, rabbit, rat and guinea pig erythrocyte AChE. Comparable results were obtained with human and monkey AChE. Differences between human, swine, rabbit, rat and guinea pig AChE were determined for the inhibition and reactivation kinetics. A six-fold difference of the inhibitory potency of paraoxon with human and guinea pig AChE was recorded while only moderate differences of the reactivation constants between human and animal AChE were determined. Obidoxime was by far the most effective reactivator with all tested species. Only minor species differences were found for the aging and spontaneous reactivation kinetics. The results of the present study underline the necessity to determine the inhibition, aging and reactivation kinetics in vitro as a basis for the development of meaningful therapeutic animal models, for the proper assessment of in vivo animal data and for the extrapolation of animal data to humans. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Use of Isoform-Specific UGT Metabolism to Determine and Describe Rates and Profiles of Glucuronidation of Wogonin and Oroxylin A by Human Liver and Intestinal Microsomes

PubMed Central

Zhou, Qiong; Zheng, Zhijie; Xia, Bijun; Tang, Lan; Lv, Chang; Liu, Wei; Liu, Zhongqiu; Hu, Ming

2010-01-01

Purposes Glucuronidation via UDP-glucuronosyltransferases (or UGTs) is a major metabolic pathway. The purposes of this study are to determine the UGT-isoform specific metabolic fingerprint (or GSMF) of wogonin and oroxylin A, and to use isoform-specific metabolism rates and kinetics to determine and describe their glucuronidation behaviors in tissue microsomes. Methods In vitro glucuronidation rates and profiles were measured using expressed UGTs and human intestinal and liver microsomes. Results GSMF experiments indicated that both flavonoids were metabolized mainly by UGT1As, with major contributions from UGT1A3 and UGT1A7-1A10. Isoform-specific metabolism showed that kinetic profiles obtained using expressed UGT1A3 and UGT1A7-1A10 could fit to known kinetic models. Glucuronidation of both flavonoids in human intestinal and liver microsomes followed simple Michaelis-Menten kinetics. A comparison of the kinetic parameters and profiles suggests that UGT1A9 is likely the main isoform responsible for liver metabolism. In contrast, a combination of UGT1As with a major contribution from UGT1A10 contributed to their intestinal metabolism. Correlation studies clearly showed that UGT isoform-specific metabolism could describe their metabolism rates and profiles in human liver and intestinal microsomes. Conclusion GSMF and isoform-specific metabolism profiles can determine and describe glucuronidation rates and profiles in human tissue microsomes. PMID:20411407

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Stephen S.; White, Josh; Hosemann, Peter

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. We measured the oxidation kinetic constant (k) as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3–5 orders of magnitude lower across the experimental temperature range. Our results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

DOE PAGES

Parker, Stephen S.; White, Josh; Hosemann, Peter; ...

2017-11-03

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. We measured the oxidation kinetic constant (k) as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3–5 orders of magnitude lower across the experimental temperature range. Our results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

NASA Astrophysics Data System (ADS)

Parker, Stephen S.; White, Josh; Hosemann, Peter; Nelson, Andrew

2018-02-01

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. The oxidation kinetic constant ( k) was measured as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3-5 orders of magnitude lower across the experimental temperature range. The results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

The main beam correction term in kinetic energy release from metastable peaks.

PubMed

Petersen, Allan Christian

2017-12-01

The correction term for the precursor ion signal width in determination of kinetic energy release is reviewed, and the correction term is formally derived. The derived correction term differs from the traditionally applied term. An experimental finding substantiates the inaccuracy in the latter. The application of the "T-value" to study kinetic energy release is found preferable to kinetic energy release distributions when the metastable peaks are slim and simple Gaussians. For electronically predissociated systems, a "borderline zero" kinetic energy release can be directly interpreted in reaction dynamics with strong curvature in the reaction coordinate. Copyright © 2017 John Wiley & Sons, Ltd.

Single-molecule enzymology of steroid transforming enzymes: Transient kinetic studies and what they tell us.

PubMed

Penning, Trevor M

2016-07-01

Structure-function studies on steroid transforming enzymes often use site-directed mutagenesis to inform mechanisms of catalysis and effects on steroid binding, and data are reported in terms of changes in steady state kinetic parameters kcat, Km and kcat/Km. However, this dissection of function is limited since kcat is governed by the rate-determining step and Km is a complex macroscopic kinetic constant. Often site-directed mutagenesis can lead to a change in the rate-determining step which cannot be revealed by just reporting a decrease in kcat alone. These issues are made more complex when it is considered that many steroid transforming enzymes have more than one substrate and product. We present the case for using transient-kinetics performed with stopped-flow spectrometry to assign rate constants to discrete steps in these multi-substrate reactions and their use to interpret enzyme mechanism and the effects of disease and engineered mutations. We demonstrate that fluorescence kinetic transients can be used to measure ligand binding that may be accompanied by isomerization steps, revealing the existence of new enzyme intermediates. We also demonstrate that single-turnover reactions can provide a klim for the chemical step and Ks for steroid-substrate binding and that when coupled with kinetic isotope effect measurements can provide information on transition state intermediates. We also demonstrate how multiple turnover experiments can provide evidence for either "burst-phase" kinetics, which can reveal a slow product release step, or linear-phase kinetics, in which the chemical step can be rate-determining. With these assignments it becomes more straightforward to analyze the effects of mutations. We use examples from the hydroxysteroid dehydrogenases (AKR1Cs) and human steroid 5β-reductase (AKR1D1) to illustrate the utility of the approach, which are members of the aldo-keto reductase (AKR) superfamily. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Kinetics of Nitrogen Atom Recombination

ERIC Educational Resources Information Center

Brown, G. Ronald; Winkler, C. A.

1977-01-01

Describes a study of the kinetics of the recombination of nitrogen atoms in which concentration-time relations are determined directly by utilizing visual observations of emissions to make gas phase titrations of N atoms with NO. (MLH)

Measurements of Protein Crystal Face Growth Rates

NASA Technical Reports Server (NTRS)

Gorti, S.

2014-01-01

Protein crystal growth rates will be determined for several hyperthermophile proteins.; The growth rates will be assessed using available theoretical models, including kinetic roughening.; If/when kinetic roughening supersaturations are established, determinations of protein crystal quality over a range of supersaturations will also be assessed.; The results of our ground based effort may well address the existence of a correlation between fundamental growth mechanisms and protein crystal quality.

Kinetic processes determining attainable pulse repetition rate in pulsed metal vapor lasers

NASA Astrophysics Data System (ADS)

Petrash, Gueorgii G.

1998-06-01

A review of the investigations of the main processes determining the attainable pulse repetition rate of elemental metal vapor pulsed gas discharge self-terminating lasers, such as copper vapor laser, gold vapor laser, lead vapor laser, is given. Kinetic processes during an excitation pulse and interpulse period are considered as well as experiments with lasers operating at high repetition rate.

A novel robust quantitative Förster resonance energy transfer assay for protease SENP2 kinetics determination against its all natural substrates.

PubMed

Liu, Yan; Shen, Yali; Zheng, Shasha; Liao, Jiayu

2015-12-01

SUMOylation (the process of adding the SUMO [small ubiquitin-like modifier] to substrates) is an important post-translational modification of critical proteins in multiple processes. Sentrin/SUMO-specific proteases (SENPs) act as endopeptidases to process the pre-SUMO or as isopeptidases to deconjugate the SUMO from its substrate. Determining the kinetics of SENPs is important for understanding their activities. Förster resonance energy transfer (FRET) technology has been widely used in biomedical research and is a powerful tool for elucidating protein interactions. In this paper we report a novel quantitative FRET-based protease assay for SENP2 endopeptidase activity that accounts for the self-fluorescent emissions of the donor (CyPet) and the acceptor (YPet). The kinetic parameters, k(cat), K(M), and catalytic efficiency (k(cat)/K(M)) of catalytic domain SENP2 toward pre-SUMO1/2/3, were obtained by this novel design. Although we use SENP2 to demonstrate our method, the general principles of this quantitative FRET-based protease kinetic determination can be readily applied to other proteases.

Kinetics of reactions of aquacobalamin with aspartic and glutamic acids and their amides in water solutions

NASA Astrophysics Data System (ADS)

Bui, T. T. T.; Sal'nikov, D. S.; Dereven'kov, I. A.; Makarov, S. V.

2017-04-01

The kinetics of aquacobalamin reaction with aspartic and glutamic acids, and with their amides in water solutions, is studied via spectrophotometry. The kinetic and activation parameters of the process are determined. It is shown that the reaction product is cobalamin-amino acid complex. The data are compared to results on the reaction between aquacobalamin and primary amines.

Molecular mechanisms of protein aggregation from global fitting of kinetic models.

PubMed

Meisl, Georg; Kirkegaard, Julius B; Arosio, Paolo; Michaels, Thomas C T; Vendruscolo, Michele; Dobson, Christopher M; Linse, Sara; Knowles, Tuomas P J

2016-02-01

The elucidation of the molecular mechanisms by which soluble proteins convert into their amyloid forms is a fundamental prerequisite for understanding and controlling disorders that are linked to protein aggregation, such as Alzheimer's and Parkinson's diseases. However, because of the complexity associated with aggregation reaction networks, the analysis of kinetic data of protein aggregation to obtain the underlying mechanisms represents a complex task. Here we describe a framework, using quantitative kinetic assays and global fitting, to determine and to verify a molecular mechanism for aggregation reactions that is compatible with experimental kinetic data. We implement this approach in a web-based software, AmyloFit. Our procedure starts from the results of kinetic experiments that measure the concentration of aggregate mass as a function of time. We illustrate the approach with results from the aggregation of the β-amyloid (Aβ) peptides measured using thioflavin T, but the method is suitable for data from any similar kinetic experiment measuring the accumulation of aggregate mass as a function of time; the input data are in the form of a tab-separated text file. We also outline general experimental strategies and practical considerations for obtaining kinetic data of sufficient quality to draw detailed mechanistic conclusions, and the procedure starts with instructions for extensive data quality control. For the core part of the analysis, we provide an online platform (http://www.amylofit.ch.cam.ac.uk) that enables robust global analysis of kinetic data without the need for extensive programming or detailed mathematical knowledge. The software automates repetitive tasks and guides users through the key steps of kinetic analysis: determination of constraints to be placed on the aggregation mechanism based on the concentration dependence of the aggregation reaction, choosing from several fundamental models describing assembly into linear aggregates and fitting the chosen models using an advanced minimization algorithm to yield the reaction orders and rate constants. Finally, we outline how to use this approach to investigate which targets potential inhibitors of amyloid formation bind to and where in the reaction mechanism they act. The protocol, from processing data to determining mechanisms, can be completed in <1 d.

Study of the kinetic parameters for synthesis and hydrolysis of pharmacologically active salicin isomer catalyzed by baker's yeast maltase

NASA Astrophysics Data System (ADS)

Veličković, D. V.; Dimitrijević, A. S.; Bihelović, F. J.; Jankov, R. M.; Milosavić, N.

2011-12-01

One of the key elements for understanding enzyme reactions is determination of its kinetic parameters. Since transglucosylation is kinetically controlled reaction, besides the reaction of synthesis, very important is the reaction of enzymatic hydrolysis of created product. Therefore, in this study, kinetic parameters for synthesis and secondary hydrolysis of pharmacologically active α isosalicin by baker's yeast maltase were calculated, and it was shown that specifity of maltase for hydrolysis is approximately 150 times higher then for synthesis.

Use of mushroom tyrosinase to introduce michaelis-menten enzyme kinetics to biochemistry students.

PubMed

Flurkey, William H; Inlow, Jennifer K

2017-05-01

An inexpensive enzyme kinetics laboratory exercise for undergraduate biochemistry students is described utilizing tyrosinase from white button mushrooms. The exercise can be completed in one or two three-hour lab sessions. The optimal amounts of enzyme, substrate (catechol), and inhibitor (kojic acid) are first determined, and then kinetic data is collected in the absence and presence of the inhibitor. A Microsoft Excel template is used to plot the data and to fit the Michaelis-Menten equation to the data to determine the kinetic parameters V max and K m . The exercise is designed to clarify and reinforce concepts covered in an accompanying biochemistry lecture course. It has been used with positive results in an upper-level biochemistry laboratory course for junior/senior students majoring in chemistry or biology. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(3):270-276, 2017. © 2016 The International Union of Biochemistry and Molecular Biology.

Equilibrium and kinetic modelling of chromium(III) sorption by animal bones.

PubMed

Chojnacka, Katarzyna

2005-04-01

The paper discusses sorption of Cr(III) ions from aqueous solutions by animal bones. Animal bones were found to be an efficient sorbent with the maximum experimentally determined sorption capacity in the range 29-194 mg g(-1) that depended on pH and temperature. The maximum experimentally determined sorption capacity was obtained at 50 degrees C, pH 5. Batch kinetics and equilibrium experiments were performed in order to investigate the influence of contact time, initial concentration of sorbate and sorbent, temperature and pH. It was found that sorption capacity increased with increase of Cr(III) concentration, temperature and initial pH of metal solution. Mathematical models describing kinetics and statics of sorption were proposed. It was found that process kinetics followed the pseudo-second-order pattern. The influence of sorbent concentration was described with Langmuir-type equation and the influence of sorbate concentration was described with empirical dependence. The models were positively verified.

Kinetic products in coordination networks: ab initio X-ray powder diffraction analysis.

PubMed

Martí-Rujas, Javier; Kawano, Masaki

2013-02-19

Porous coordination networks are materials that maintain their crystal structure as molecular "guests" enter and exit their pores. They are of great research interest with applications in areas such as catalysis, gas adsorption, proton conductivity, and drug release. As with zeolite preparation, the kinetic states in coordination network preparation play a crucial role in determining the final products. Controlling the kinetic state during self-assembly of coordination networks is a fundamental aspect of developing further functionalization of this class of materials. However, unlike for zeolites, there are few structural studies reporting the kinetic products made during self-assembly of coordination networks. Synthetic routes that produce the necessary selectivity are complex. The structural knowledge obtained from X-ray crystallography has been crucial for developing rational strategies for design of organic-inorganic hybrid networks. However, despite the explosive progress in the solid-state study of coordination networks during the last 15 years, researchers still do not understand many chemical reaction processes because of the difficulties in growing single crystals suitable for X-ray diffraction: Fast precipitation can lead to kinetic (metastable) products, but in microcrystalline form, unsuitable for single crystal X-ray analysis. X-ray powder diffraction (XRPD) routinely is used to check phase purity, crystallinity, and to monitor the stability of frameworks upon guest removal/inclusion under various conditions, but rarely is used for structure elucidation. Recent advances in structure determination of microcrystalline solids from ab initio XRPD have allowed three-dimensional structure determination when single crystals are not available. Thus, ab initio XRPD structure determination is becoming a powerful method for structure determination of microcrystalline solids, including porous coordination networks. Because of the great interest across scientific disciplines in coordination networks, especially porous coordination networks, the ability to determine crystal structures when the crystals are not suitable for single crystal X-ray analysis is of paramount importance. In this Account, we report the potential of kinetic control to synthesize new coordination networks and we describe ab initio XRPD structure determination to characterize these networks' crystal structures. We describe our recent work on selective instant synthesis to yield kinetically controlled porous coordination networks. We demonstrate that instant synthesis can selectively produce metastable networks that are not possible to synthesize by conventional solution chemistry. Using kinetic products, we provide mechanistic insights into thermally induced (573-723 K) (i.e., annealing method) structural transformations in porous coordination networks as well as examples of guest exchange/inclusion reactions. Finally, we describe a memory effect that allows the transfer of structural information from kinetic precursor structures to thermally stable structures through amorphous intermediate phases. We believe that ab initio XRPD structure determination will soon be used to investigate chemical processes that lead intrinsically to microcrystalline solids, which up to now have not been fully understood due to the unavailability of single crystals. For example, only recently have researchers used single-crystal X-ray diffraction to elucidate crystal-to-crystal chemical reactions taking place in the crystalline scaffold of coordination networks. The potential of ab initio X-ray powder diffraction analysis goes beyond single-crystal-to-single-crystal processes, potentially allowing members of this field to study intriguing in situ reactions, such as reactions within pores.

Equilibrium and kinetic adsorption study of a cationic dye by a natural adsorbent--silkworm pupa.

PubMed

Noroozi, B; Sorial, G A; Bahrami, H; Arami, M

2007-01-02

In this work the use of silkworm pupa, which is the waste of silk spinning industries has been investigated as an adsorbent for the removal of C.I. Basic Blue 41. The amino acid nature of the pupa provided a reasonable capability for dye removal. Equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of the dye could be described reasonably well by either Langmuir or Freundlich models. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was determined to be 555 mg/g. Kinetic studies indicated that the adsorption follows pseudo-second-order kinetics with a rate constant of 0.0434 and 0.0572 g/min mg for initial dye concentration of 200 mg/l at 20 and 40 degrees C, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process. The rate constant for intra-particle diffusion was estimated to be 1.985 mg/g min(0.5).

Kinetic study of an enzymic cycling system coupled to an enzymic step: determination of alkaline phosphatase activity.

PubMed Central

Valero, E; Varón, R; García-Carmona, F

1995-01-01

A kinetic study is made of a system consisting of a specific enzymic cycling assay coupled to an enzymic reaction. A kinetic analysis of this system is presented, and the accumulation of chromophore involved in the cycle is seen to be parabolic, i.e. the rate of the reaction increases continuously with constant acceleration. The system is illustrated by the measurement of alkaline phosphatase activity using beta-NADP+ as substrate. The enzymes alcohol dehydrogenase and diaphorase are used to cycle beta-NAD+ in the presence of ethanol and p-Iodonitrotetrazolium Violet. During each turn of the cycle, one molecule of the tetrazolium salt is reduced to an intensely coloured formazan. A simple procedure for evaluating the kinetic parameters involved in the system and for optimizing this cycling assay is described. The method is applicable to the measurement of any enzyme, and its amplification capacity as well as the simplicity of determining kinetic parameters enable it to be employed in enzyme immunoassays to increase the magnitude of the measured response. PMID:7619054

Calcium kinetics with microgram stable isotope doses and saliva sampling

NASA Technical Reports Server (NTRS)

Smith, S. M.; Wastney, M. E.; Nyquist, L. E.; Shih, C. Y.; Wiesmann, H.; Nillen, J. L.; Lane, H. W.

1996-01-01

Studies of calcium kinetics require administration of tracer doses of calcium and subsequent repeated sampling of biological fluids. This study was designed to develop techniques that would allow estimation of calcium kinetics by using small (micrograms) doses of isotopes instead of the more common large (mg) doses to minimize tracer perturbation of the system and reduce cost, and to explore the use of saliva sampling as an alternative to blood sampling. Subjects received an oral dose (133 micrograms) of 43Ca and an i.v. dose (7.7 micrograms) of 46Ca. Isotopic enrichment in blood, urine, saliva and feces was well above thermal ionization mass spectrometry measurement precision up to 170 h after dosing. Fractional calcium absorptions determined from isotopic ratios in blood, urine and saliva were similar. Compartmental modeling revealed that kinetic parameters determined from serum or saliva data were similar, decreasing the necessity for blood samples. It is concluded from these results that calcium kinetics can be assessed with micrograms doses of stable isotopes, thereby reducing tracer costs and with saliva samples, thereby reducing the amount of blood needed.

New Reduced Two-Time Step Method for Calculating Combustion and Emission Rates of Jet-A and Methane Fuel With and Without Water Injection

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2004-01-01

A simplified kinetic scheme for Jet-A, and methane fuels with water injection was developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) or even simple FORTRAN codes that are being developed at Glenn. The two time step method is either an initial time averaged value (step one) or an instantaneous value (step two). The switch is based on the water concentration in moles/cc of 1x10(exp -20). The results presented here results in a correlation that gives the chemical kinetic time as two separate functions. This two step method is used as opposed to a one step time averaged method previously developed to determine the chemical kinetic time with increased accuracy. The first time averaged step is used at the initial times for smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, initial water to fuel mass ratio, temperature, and pressure. The second instantaneous step, to be used with higher water concentrations, gives the chemical kinetic time as a function of instantaneous fuel and water mole concentration, pressure and temperature (T4). The simple correlations would then be compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates were then used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide and NOx were obtained for Jet-A fuel and methane with and without water injection to water mass loadings of 2/1 water to fuel. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentrations of carbon monoxide and nitrogen oxide as functions of overall equivalence ratio, water to fuel mass ratio, pressure and temperature (T3). The temperature of the gas entering the turbine (T4) was also correlated as a function of the initial combustor temperature (T3), equivalence ratio, water to fuel mass ratio, and pressure.

Collisional excitation of interstellar methyl cyanide

NASA Technical Reports Server (NTRS)

Green, Sheldon

1986-01-01

Theoretical calculations are used to determine the collisional excitation rates of methyl cyanide under interstellar molecular cloud conditions. The required Q(L,M) as a function of kinetic temperature were determined by averaging fixed energy IOS (infinite order sudden) results over appropriate Boltzmann distributions of collision energies. At a kinetic temperature of 40 K, rates within a K ladder were found to be accurate to generally better than about 30 percent.

Using a Datalogger to Determine First-Order Kinetics and Calcium Carbonate in Eggshells

ERIC Educational Resources Information Center

Choi, Martin M. F.; Pui Shan Wong

2004-01-01

The applications of a Pasco CI-6532 pressure sensor used in conjunction with a datalogger to monitor the liberation of carbon dioxide in the reaction CaCO3(s) + 2H(super +)(aq) --> Ca(super 2+)(aq) + CO2 (g) + H2O(I) are described. The method serves for the determination of the chemical kinetics of the reaction and also can be extended to…

Co-pyrolysis behavior of fermentation residues with woody sawdust by thermogravimetric analysis and a vacuum reactor.

PubMed

Zheng, Yan; Zhang, Yimin; Xu, Jingna; Li, Xiayang; Charles Xu, Chunbao

2017-12-01

This study aimed at cost-effective utilization of fermentation residues (FR) from biogas project for bio-energy via co-pyrolysis of FR and woody sawdust (WS). In this study, a vacuum reactor was used to study the pyrolysis behaviors of individual and blend samples of FR and WS. Obvious synergistic effects were observed, resulting in a lower char yield but a higher gas yield. The presence of woody sawdust promoted the devolatilization of FR, and improved the syngas (H 2 and CO) content in the gaseous products. Compared to those of the char from pyrolysis of individual feedstock, co-pyrolysis of FR and WS in the vacuum reactor promoted the cracking reactions of large aromatic rings, enlarged the surface area and reduced the oxygenated groups of the resulted char. Copyright © 2017 Elsevier Ltd. All rights reserved.

Coal Combustion Science quarterly progress report, April--June 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardesty, D.R.; Hurt, R.H.; Baxter, L.L.

1992-09-01

The objective of this work is to support the Office of Fossil Energy in executing research on coal combustion science. This project consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center (PETC) Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency (IEA) Coal Combustion Science Project. Specific tasks include: The characterization of the physical and chemical processes that constitute the early devolatilization phase of coal combustion: Characterization of the combustion behavior of selected coals under conditions relevant to industria pulverized coal-fired furnaces; and to establish a quantitative understanding of themore » mechanisms and rates of transformation, fragmentation, and deposition of mineral matter in coal combustion environments as a function of coal type, particle size and temperature, the initial forms and distributions of mineral species in the unreacted coal, and the local gas temperature and composition.« less

Combustion properties of Kraft Black Liquors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frederick, W.J. Jr.; Hupa, M.

1993-04-01

In a previous study of the phenomena involved in the combustion of black liquor droplets a numerical model was developed. The model required certain black liquor specific combustion information which was then not currently available, and additional data were needed for evaluating the model. The overall objectives of the project reported here was to provide experimental data on key aspects of black liquor combustion, to interpret the data, and to put it into a form which would be useful for computational models for recovery boilers. The specific topics to be investigated were the volatiles and char carbon yields from pyrolysismore » of single black liquor droplets; a criterion for the onset of devolatilization and the accompanying rapid swelling; and the surface temperature of black liquor droplets during pyrolysis, combustion, and gasification. Additional information on the swelling characteristics of black liquor droplets was also obtained as part of the experiments conducted.« less

Pre-terrestrial origin of rust in the Nakhla meteorite

NASA Technical Reports Server (NTRS)

Wentworth, Susan J.; Gooding, James L.

1990-01-01

The authors present quantative elemental compositions and summarize textural evidence for the pre-terrestrial origin of rust on the Nakhla meteorite. The material in question is called 'rust' because its phase composition remains unknown. Compelling evidence for the pre-terrestrial origin of the rust is found in rust veins truncated by fusion crust and preserved as faults in sutured igneous crystals. Rust veins that approach the meteorite's fusion crust become discontinuous and exhibit vugs that suggest partial decrepitation; no veins that penetrate the fusion crust have been found. Because the rust probably contains volatile compounds, it is reasonable to expect that heating near the ablation surface (formed during atmospheric entry to Earth) would encourage devolatilization of the rust. Hence, the absence of rust veins in fusion crust and vugs in rust veins near fusion crust clearly imply that the rust existed in the meteorite before atmospheric entry.

Determination of differential cross sections and kinetic energy release of co-products from central sliced images in photo-initiated dynamic processes.

PubMed

Chen, Kuo-mei; Chen, Yu-wei

2011-04-07

For photo-initiated inelastic and reactive collisions, dynamic information can be extracted from central sliced images of state-selected Newton spheres of product species. An analysis framework has been established to determine differential cross sections and the kinetic energy release of co-products from experimental images. When one of the reactants exhibits a high recoil speed in a photo-initiated dynamic process, the present theory can be employed to analyze central sliced images from ion imaging or three-dimensional sliced fluorescence imaging experiments. It is demonstrated that the differential cross section of a scattering process can be determined from the central sliced image by a double Legendre moment analysis, for either a fixed or continuously distributed recoil speeds in the center-of-mass reference frame. Simultaneous equations which lead to the determination of the kinetic energy release of co-products can be established from the second-order Legendre moment of the experimental image, as soon as the differential cross section is extracted. The intensity distribution of the central sliced image, along with its outer and inner ring sizes, provide all the clues to decipher the differential cross section and the kinetic energy release of co-products.

Kinetic parameter estimation model for anaerobic co-digestion of waste activated sludge and microalgae.

PubMed

Lee, Eunyoung; Cumberbatch, Jewel; Wang, Meng; Zhang, Qiong

2017-03-01

Anaerobic co-digestion has a potential to improve biogas production, but limited kinetic information is available for co-digestion. This study introduced regression-based models to estimate the kinetic parameters for the co-digestion of microalgae and Waste Activated Sludge (WAS). The models were developed using the ratios of co-substrates and the kinetic parameters for the single substrate as indicators. The models were applied to the modified first-order kinetics and Monod model to determine the rate of hydrolysis and methanogenesis for the co-digestion. The results showed that the model using a hyperbola function was better for the estimation of the first-order kinetic coefficients, while the model using inverse tangent function closely estimated the Monod kinetic parameters. The models can be used for estimating kinetic parameters for not only microalgae-WAS co-digestion but also other substrates' co-digestion such as microalgae-swine manure and WAS-aquatic plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determination of dosimetric and kinetic features of gamma irradiated solid calcium ascorbate dihydrate using ESR spectroscopy

NASA Astrophysics Data System (ADS)

Tuner, H.

2013-01-01

Effects of gamma radiation on solid calcium ascorbate dihydrate were studied using electron spin resonance (ESR) spectroscopy. Irradiated samples were found to present two specific ESR lines with shoulder at low and high magnetic field sides. Structural and kinetic features of the radicalic species responsible for experimental ESR spectrum were explored through the variations of the signal intensities with applied microwave power, variable temperature, high-temperature annealing and room temperature storage time studies. Dosimetric potential of the sample was also determined using spectrum area and measured signal intensity measurements. It was concluded that three radicals with different spectroscopic and kinetic features were produced upon gamma irradiation.

New insight into the ZnO sulfidation reaction: mechanism and kinetics modeling of the ZnS outward growth.

PubMed

Neveux, Laure; Chiche, David; Pérez-Pellitero, Javier; Favergeon, Loïc; Gay, Anne-Sophie; Pijolat, Michèle

2013-02-07

Zinc oxide based materials are commonly used for the final desulfurization of synthesis gas in Fischer-Tropsch based XTL processes. Although the ZnO sulfidation reaction has been widely studied, little is known about the transformation at the crystal scale, its detailed mechanism and kinetics. A model ZnO material with well-determined characteristics (particle size and shape) has been synthesized to perform this study. Characterizations of sulfided samples (using XRD, TEM and electron diffraction) have shown the formation of oriented polycrystalline ZnS nanoparticles with a predominant hexagonal form (wurtzite phase). TEM observations also have evidenced an outward development of the ZnS phase, showing zinc and oxygen diffusion from the ZnO-ZnS internal interface to the surface of the ZnS particle. The kinetics of ZnO sulfidation by H(2)S has been investigated using isothermal and isobaric thermogravimetry. Kinetic tests have been performed that show that nucleation of ZnS is instantaneous compared to the growth process. A reaction mechanism composed of eight elementary steps has been proposed to account for these results, and various possible rate laws have been determined upon approximation of the rate-determining step. Thermogravimetry experiments performed in a wide range of H(2)S and H(2)O partial pressures have shown that the ZnO sulfidation reaction rate has a nonlinear variation with H(2)S partial pressure at the same time no significant influence of water vapor on reaction kinetics has been observed. From these observations, a mixed kinetics of external interface reaction with water desorption and oxygen diffusion has been determined to control the reaction kinetics and the proposed mechanism has been validated. However, the formation of voids at the ZnO-ZnS internal interface, characterized by TEM and electron tomography, strongly slows down the reaction rate. Therefore, the impact of the decreasing ZnO-ZnS internal interface on reaction kinetics has been taken into account in the reaction rate expression. In this way the void formation at the interface has been modeled considering a random nucleation followed by an isotropic growth of cavities. Very good agreement has been observed between both experimental and calculated rates after taking into account the decrease in the ZnO-ZnS internal interface.

Kinetic analysis of central ( sup 11 C)raclopride binding to D2-dopamine receptors studied by PET--a comparison to the equilibrium analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farde, L.; Eriksson, L.; Blomquist, G.

1989-10-01

(11C)Raclopride binding to central D2-dopamine receptors in humans has previously been examined by positron emission tomography (PET). Based on the rapid occurrence of binding equilibrium, a saturation analysis has been developed for the determination of receptor density (Bmax) and affinity (Kd). For analysis of PET measurements obtained with other ligands, a kinetic three-compartment model has been used. In the present study, the brain uptake of (11C)raclopride was analyzed further by applying both a kinetic and an equilibrium analysis to data obtained from four PET experiments in each of three healthy subjects. First regional CBV was determined. In the second andmore » third experiment, (11C)-raclopride with high and low specific activity was used. In a fourth experiment, the (11C)raclopride enantiomer (11C)FLB472 was used to examine the concentration of free radioligand and nonspecific binding in brain. Radio-activity in arterial blood was measured using an automated blood sampling system. Bmax and Kd values for (11C)raclopride binding could be determined also with the kinetic analysis. As expected theoretically, those values were similar to those obtained with the equilibrium analysis. In addition, the kinetic analysis allowed separate determination of the association and dissociation rate constants, kon and koff, respectively. Examination of (11C)raclopride and (11C)FLB472 uptake in brain regions devoid of specific D2-dopamine receptor binding indicated a fourth compartment in which uptake was reversible, nonstereoselective, and nonsaturable in the dose range studied.« less

Kinetics and mechanism of olefin catalytic hydroalumination by organoaluminum compounds

NASA Astrophysics Data System (ADS)

Koledina, K. F.; Gubaidullin, I. M.

2016-05-01

The complex reaction mechanism of α-olefin catalytic hydroalumination by alkylalanes is investigated via mathematical modeling that involves plotting the kinetic models for the individual reactions that make up a complex system and a separate study of their principles. Kinetic parameters of olefin catalytic hydroalumination are estimated. Activation energies of the possible steps of the schemes of complex reaction mechanisms are compared and possible reaction pathways are determined.

Plasma Assisted Combustion

DTIC Science & Technology

2007-02-28

these pulses was uniform. Dependence of the energy contribution on pressure is showed in the Figure 3.5. It is clearly seen that for the pressure of...note that water–ions kinetics is more important than kinetics of initial substances– ions because water has higher proton affinity energy than... pulsed discharge. 4.3.2 Kinetic model To calculate the densities of active particles, one has to determine electron energy dis- tribution function (EEDF

Kinetics and Mechanisms of Phosphorus Adsorption in Soils from Diverse Ecological Zones in the Source Area of a Drinking-Water Reservoir

PubMed Central

Zhang, Liang; Loáiciga, Hugo A.; Xu, Meng; Du, Chao; Du, Yun

2015-01-01

On-site soils are increasingly used in the treatment and restoration of ecosystems to harmonize with the local landscape and minimize costs. Eight natural soils from diverse ecological zones in the source area of a drinking-water reservoir in central China are used as adsorbents for the uptake of phosphorus from aqueous solutions. The X-ray fluorescence (XRF) spectrometric and BET (Brunauer-Emmett-Teller) tests and the Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectral analyses are carried out to investigate the soils’ chemical properties and their potential changes with adsorbed phosphorous from aqueous solutions. The intra-particle diffusion, pseudo-first-order, and pseudo-second-order kinetic models describe the adsorption kinetic processes. Our results indicate that the adsorption processes of phosphorus in soils occurred in three stages and that the rate-controlling steps are not solely dependent on intra-particle diffusion. A quantitative comparison of two kinetics models based on their linear and non-linear representations, and using the chi-square (χ2) test and the coefficient of determination (r2), indicates that the adsorptive properties of the soils are best described by the non-linear pseudo-second-order kinetic model. The adsorption characteristics of aqueous phosphorous are determined along with the essential kinetic parameters. PMID:26569278

From receptor binding kinetics to signal transduction; a missing link in predicting in vivo drug-action.

PubMed

Nederpelt, Indira; Kuzikov, Maria; de Witte, Wilbert E A; Schnider, Patrick; Tuijt, Bruno; Gul, Sheraz; IJzerman, Adriaan P; de Lange, Elizabeth C M; Heitman, Laura H

2017-10-26

An important question in drug discovery is how to overcome the significant challenge of high drug attrition rates due to lack of efficacy and safety. A missing link in the understanding of determinants for drug efficacy is the relation between drug-target binding kinetics and signal transduction, particularly in the physiological context of (multiple) endogenous ligands. We hypothesized that the kinetic binding parameters of both drug and endogenous ligand play a crucial role in determining cellular responses, using the NK1 receptor as a model system. We demonstrated that the binding kinetics of both antagonists (DFA and aprepitant) and endogenous agonists (NKA and SP) have significantly different effects on signal transduction profiles, i.e. potency values, in vitro efficacy values and onset rate of signal transduction. The antagonistic effects were most efficacious with slowly dissociating aprepitant and slowly associating NKA while the combination of rapidly dissociating DFA and rapidly associating SP had less significant effects on the signal transduction profiles. These results were consistent throughout different kinetic assays and cellular backgrounds. We conclude that knowledge of the relationship between in vitro drug-target binding kinetics and cellular responses is important to ultimately improve the understanding of drug efficacy in vivo.

Ammonium Removal from Aqueous Solutions by Clinoptilolite: Determination of Isotherm and Thermodynamic Parameters and Comparison of Kinetics by the Double Exponential Model and Conventional Kinetic Models

PubMed Central

Tosun, İsmail

2012-01-01

The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients. PMID:22690177

Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.

PubMed

Tosun, Ismail

2012-03-01

The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

Application of vacuum stability test to determine thermal decomposition kinetics of nitramines bonded by polyurethane matrix

NASA Astrophysics Data System (ADS)

Elbeih, Ahmed; Abd-Elghany, Mohamed; Elshenawy, Tamer

2017-03-01

Vacuum stability test (VST) is mainly used to study compatibility and stability of energetic materials. In this work, VST has been investigated to study thermal decomposition kinetics of four cyclic nitramines, 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, CL-20), bonded by polyurethane matrix based on hydroxyl terminated polybutadiene (HTPB). Model fitting and model free (isoconversional) methods have been applied to determine the decomposition kinetics from VST results. For comparison, the decomposition kinetics were determined isothermally by ignition delay technique and non-isothermally by Advanced Kinetics and Technology Solution (AKTS) software. The activation energies for thermolysis obtained by isoconversional method based on VST technique of RDX/HTPB, HMX/HTPB, BCHMX/HTPB and CL20/HTPB were 157.1, 203.1, 190.0 and 176.8 kJ mol-1 respectively. Model fitting method proved that the mechanism of thermal decomposition of BCHMX/HTPB is controlled by the nucleation model while all the other studied PBXs are controlled by the diffusion models. A linear relationship between the ignition temperatures and the activation energies was observed. BCHMX/HTPB is interesting new PBX in the research stage.

Kinetics and equilibria of cyanide binding to prostaglandin H synthase.

PubMed

MacDonald, I D; Dunford, H B

1989-09-01

Cyanide binding to prostaglandin H (PGH) synthase results in a spectral shift in the Soret region. This shift was exploited to determine equilibrium and kinetic parameters of the cyanide binding process. At pH 8.0, ionic strength 0.22 M, 4 degrees C, the cyanide dissociation constant, determined from equilibrium experiments, is (65 +/- 10) microM. The binding rate constant is (2.8 +/- 0.2) x 10(3) M-1 s-1, and the dissociation rate constant is zero within experimental error. Through a kinetic study of the binding process as a function of pH, from pH 3.96 to 8.00, it was possible to determine the pKa of a heme-linked acid group on the enzyme of 4.15 +/- 0.10 with citrate buffer. An apparent pKa of 4.75 +/- 0.03 was determined with acetate buffer; this different value is attributed to complexation of the enzyme with one of the components of the acetate buffer.

Methods for determining the physiological state of a plant

DOEpatents

Kramer, David M.; Sacksteder, Colette

2003-09-23

The present invention provides methods for measuring a photosynthetic parameter. The methods of the invention include the steps of: (a) illuminating a plant leaf until steady-state photosynthesis is achieved; (b) subjecting the illuminated plant leaf to a period of darkness; (c) using a kinetic spectrophotometer or kinetic spectrophotometer/fluorimeter to collect spectral data from the plant leaf treated in accordance with steps (a) and (b); and (d) determining a photosynthetic parameter from the spectral data. In another aspect, the invention provides methods for determining the physiological state of a plant.

Comparison in waterborne Cu, Ni and Pb bioaccumulation kinetics between different gammarid species and populations: Natural variability and influence of metal exposure history.

PubMed

Urien, N; Farfarana, A; Uher, E; Fechner, L C; Chaumot, A; Geffard, O; Lebrun, J D

2017-12-01

Kinetic parameters (uptake from solution and elimination rate constants) of Cu, Ni and Pb bioaccumulation were determined from two Gammarus pulex and three Gammarus fossrum wild populations collected from reference sites throughout France in order to assess the inter-species and the natural inter-population variability of metal bioaccumulation kinetics in that sentinel organism. For that, each population was independently exposed for seven days to either 2.5μgL -1 Cu (39.3nM), 40μgL -1 Ni (681nM) or 10μgL -1 Pb (48.3nM) in laboratory controlled conditions, and then placed in unexposed microcosms for a 7-day depuration period. In the same way, the possible influence of metal exposure history on subsequent metal bioaccumulation kinetics was addressed by collecting wild gammarids from three populations inhabiting stations contaminated either by Cd, Pb or both Pb and Ni (named pre-exposed thereafter). In these pre-exposed organisms, assessment of any changes in metal bioaccumulation kinetics was achieved by comparison with the natural variability of kinetic parameters defined from reference populations. Results showed that in all studied populations (reference and pre-exposed) no significant Cu bioaccumulation was observed at the exposure concentration of 2.5μgL -1 . Concerning the reference populations, no significant differences in Ni and Pb bioaccumulation kinetics between the two species (G. pulex and G. fossarum) was observed allowing us to consider all the five reference populations to determine the inter-population natural variability, which was found to be relatively low (kinetic parameters determined for each population remained within a factor of 2 of the minimum and maximum values). Organisms from the population exhibiting a Pb exposure history presented reduced Ni uptake and elimination rate constants, whereas no influence on Ni kinetic parameters was observed in organisms from the population exhibiting an exposure history to both Ni and Pb. Furthermore Pb bioaccumulation kinetics were unaffected whatever the condition of pre-exposure in natural environment. Finally, these results highlight the complexity of confounding factors, such as metal exposure history, that influence metal bioaccumulation processes and showed that pre-exposure to one metal can cause changes in the bioaccumulation kinetics of other metals. These results also address the question of the underlying mechanisms developed by organisms to cope with metal contamination. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanistic models enable the rational use of in vitro drug-target binding kinetics for better drug effects in patients.

PubMed

de Witte, Wilhelmus E A; Wong, Yin Cheong; Nederpelt, Indira; Heitman, Laura H; Danhof, Meindert; van der Graaf, Piet H; Gilissen, Ron A H J; de Lange, Elizabeth C M

2016-01-01

Drug-target binding kinetics are major determinants of the time course of drug action for several drugs, as clearly described for the irreversible binders omeprazole and aspirin. This supports the increasing interest to incorporate newly developed high-throughput assays for drug-target binding kinetics in drug discovery. A meaningful application of in vitro drug-target binding kinetics in drug discovery requires insight into the relation between in vivo drug effect and in vitro measured drug-target binding kinetics. In this review, the authors discuss both the relation between in vitro and in vivo measured binding kinetics and the relation between in vivo binding kinetics, target occupancy and effect profiles. More scientific evidence is required for the rational selection and development of drug-candidates on the basis of in vitro estimates of drug-target binding kinetics. To elucidate the value of in vitro binding kinetics measurements, it is necessary to obtain information on system-specific properties which influence the kinetics of target occupancy and drug effect. Mathematical integration of this information enables the identification of drug-specific properties which lead to optimal target occupancy and drug effect in patients.

Vortex movement and magnetization of high Tc superconductors

NASA Technical Reports Server (NTRS)

Roytburd, A. L.; Turchinskaya, M. J.

1991-01-01

The basic characteristics of the thermoactivated vortex mobility in Y1Ba2Cu3O7 are determined by measurement of the kinetics of magnetization in two time regimes. The analysis of the kinetics of the approach of the equilibrium results in the activation energy, while the measurement of the log-creep rate allows determination of the activated moment. It is shown that the movement of vortices can be regarded as the diffusion process.

Enzymatic Spectrophotometric Reaction Rate Determination of Glucose in Fruit Drinks and Carbonated Beverages. An Analytical Chemistry Laboratory Experiment for Food Science-Oriented Students

NASA Astrophysics Data System (ADS)

Vasilarou, Argyro-Maria G.; Georgiou, Constantinos A.

2000-10-01

The glucose oxidase-horseradish peroxidase coupled reaction using phenol and 4-aminoantipyrine is used for the kinetic determination of glucose in drinks and beverages. This laboratory experiment demonstrates the implementation of reaction rate kinetic methods of analysis, the use of enzymes as selective analytical reagents for the determination of substrates, the kinetic masking of ascorbic acid interference, and the analysis of glucose in drinks and beverages. The method is optimized for student use in the temperature range of 18-28 °C and can be used in low-budget laboratories equipped with an inexpensive visible photometer. The mixed enzyme-chromogen solution that is used is stable for two months. Precision ranged from 5.1 to 12% RSD for analyses conducted during a period of two months by 48 students.

Indirect determination of the electric field in plasma discharges using laser-induced fluorescence spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaudolon, J., E-mail: julien.vaudolon@cnrs-orleans.fr; Mazouffre, S., E-mail: stephane.mazouffre@cnrs-orleans.fr

2014-09-15

The evaluation of electric fields is of prime interest for the description of plasma characteristics. In this work, different methods for determining the electric field profile in low-pressure discharges using one- and two-dimensional Laser-Induced Fluorescence (LIF) measurements are presented and discussed. The energy conservation, fluid, and kinetic approaches appear to be well-suited for the electric field evaluation in this region of the plasma flow. However, the numerical complexity of a two-dimensional kinetic model is penalizing due to the limited signal-to-noise ratio that can be achieved, making the computation of the electric field subject to large error bars. The ionization contributionmore » which appears in the fluid model makes it unattractive on an experimental viewpoint. The energy conservation and 1D1V kinetic approaches should therefore be preferred for the determination of the electric field when LIF data are used.« less

The influence of different space-related physiological variations on exercise capacity determined by oxygen uptake kinetics.

PubMed

Stegemann, J

1992-07-01

Oxygen uptake kinetics, following defined variations of work load changes allow to estimate the contribution of aerob and anaerob energy supply which is the base for determining work capacity. Under the aspect of long duration missions with application of adequate dosed countermeasures, a reliable estimate of the astronaut's work capacity is important to adjust the necessary inflight training. Since the kinetics of oxygen uptake originate in the working muscle group itself, while measurements are performed at the mouth, various influences within the oxygen transport system might disturb the determinations. There are not only detraining effects but also well-known other influences, such as blood- and fluid shifts induced by weightlessness. They might have an impact on the circulatory system. Some of these factors have been simulated by immersion, blood donation, and changing of the body position.

The influence of different space-related physiological variations on exercise capacity determined by oxygen uptake kinetics

NASA Astrophysics Data System (ADS)

Stegemann, J.

Oxygen uptake kinetics, following defined variations of work load changes allow to estimate the contribution of aerob and anaerob energy supply which is the base for determining work capacity. Under the aspect of long duration missions with application of adequate dosed countermeasures, a reliable estimate of the astronaut's work capacity is important to adjust the necessary inflight training. Since the kinetics of oxygen uptake originate in the working muscle group itself, while measurements are performed at the mouth, various influences within the oxygen transport system might disturb the determinations. There are not only detraining effects but also well-known other influences, such as blood- and fluid shifts induced by weightlessness. They might have an impact on the circulatory system. Some of these factors have been simulated by immersion, blood donation, and changing of the body position.

Examination and evaluation of the use of screen heaters for the measurement of the high temperature pyrolysis kinetics of polyethene and polypropene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westerhout, R.W.J.; Balk, R.H.P.; Meijer, R.

1997-08-01

A screen heater with a gas sweep was developed and applied to study the pyrolysis kinetics of low density polyethene (LDPE) and polypropene (PP) at temperatures ranging from 450 to 530 C. The aim of this study was to examine the applicability of screen heaters to measure these kinetics. On-line measurement of the rate of volatiles formation using a hydrocarbon analyzer was applied to enable the determination of the conversion rate over the entire conversion range on the basis of a single experiment. Another important feature of the screen heater used in this study is the possibility to measure pyrolysismore » kinetics under nearly isothermal conditions. The kinetic constants for LDPE and PP pyrolysis were determined, using a first order model to describe the conversion rate in the 70--90% conversion range and the random chain dissociation model for the entire conversion range. In addition to the experimental work two single particle models have been developed which both incorporate a mass and a (coupled) enthalpy balance, which were used to assess the influence of internal and external heat transfer processes on the pyrolysis process. The first model assumes a variable density and constant volume during the pyrolysis process, whereas the second model assumes a constant density and a variable volume. An important feature of these models is that they can accommodate kinetic models for which no analytical representation of the pyrolysis kinetics is available.« less

Effects of age and step length on joint kinetics during stepping task.

PubMed

Bieryla, Kathleen A; Buffinton, Christine

2015-07-16

Following a balance perturbation, a stepping response is commonly used to regain support, and the distance of the recovery step can vary. To date, no other studies have examined joint kinetics in young and old adults during increasing step distances, when participants are required to bring their rear foot forward. Therefore, the purpose of this study was to examine age-related differences in joint kinetics with increasing step distance. Twenty young and 20 old adults completed the study. Participants completed a step starting from double support, at an initial distance equal to the individual's average step length. The distance was increased by 10% body height until an unsuccessful attempt. A one-way, repeated measures ANOVA was used to determine the effects of age on joint kinetics during the maximum step distance. A two-way, repeated measures, mixed model ANOVA was used to determine the effects of age, step distance, and their interaction on joint kinetics during the first three step distances for all participants. Young adults completed a significantly longer step than old adults. During the maximum step, in general, kinetic measures were greater in the young than in the old. As step distance increased, all but one kinetic measure increased for both young and old adults. This study has shown the ability to discriminate between young and old adults, and could potentially be used in the future to distinguish between fallers and non-fallers. Copyright © 2015 Elsevier Ltd. All rights reserved.

Kinetics and Product Channels in Combustion Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hershberger, John F.

We report study of the chemical kinetics and/or photochemistry of several chemical reactions of potential interest in understanding the gas phase combustion chemistry of nitrogen-containing molecules. Studies completed during the final grant period include determination of quantum yields of the photolysis of HCNO, fulminic acid, a kinetics and product channel study of the reaction of CN radicals with methyl bromide, and study of the products of the reaction of hydroxymethyl radical with nitric oxide.

Scrap tyre pyrolysis: Modified chemical percolation devolatilization (M-CPD) to describe the influence of pyrolysis conditions on product yields.

PubMed

Tan, Vincent; De Girolamo, Anthony; Hosseini, Tahereh; Alhesan, Jameel Aljariri; Zhang, Lian

2018-03-16

This paper attempts to develop a modified chemical percolation devolatilization (M-CPD) model that can include heat transfer, primary pyrolysis and the secondary cracking reactions of volatiles together to describe the pyrolysis of waste scrap tyre chip, as well as to examine the influence of operating conditions on the scrap tyre pyrolysis product yields. Such a study has yet to be conducted in the past, thereby leading to a large knowledge gap failing to understand the pyrolysis of the coarse feedstock appropriately. To validate the developed model, a number of operating parameters including reactor configurations, carrier gas compositions (argon and argon blended with CO 2 and/or steam), scrap tyre chip size (0.5-15.0 mm), terminal pyrolysis temperature (400-800 °C) and heating rate (10 °C/min and 110 °C/min) were examined in a lab-scale fixed-bed pyrolyser, with a particular focus on the secondary cracking extents of the liquid tar. Through both experimental investigation and modelling approach, it was found that significant secondary cracking extent occurred upon the increase in the feedstock size, heating rate and residence time. Upon the fast pyrolysis, the average temperature gap between the centres of the coarse particle and reactor wall could reach a maximum of 115 °C for the tyre chips of 6-15 mm. Consequently, its primary volatiles underwent the secondary cracking reaction at an overall extent of 17% at a terminal temperature of 600 °C and a fast heating rate of 110 °C/min. Consequently, the yield of light gases including methane was increased remarkably. The flow rate of inert carrier gas was also influential in the secondary cracking, in which a maximum tar yield (54 wt%) was reached at a carrier gas flow rate of 1.5  L/min. This indicates the occurrence of secondary cracking has been largely minimised. At a pyrolysis temperature of 600 °C, the addition of CO 2 in the carrier gas had an insignificant effect on the product yield distribution under the slow heating scheme. In contrast, the addition of steam resulted in a slight increase of carbon monoxide, presumably due to the occurrence of gasification reaction. Copyright © 2018 Elsevier Ltd. All rights reserved.

Kinetics and Mechanisms of γ′ Reprecipitation in a Ni-based Superalloy

PubMed Central

Masoumi, F.; Shahriari, D.; Jahazi, M.; Cormier, J.; Devaux, A.

2016-01-01

The reprecipitation mechanisms and kinetics of γ′ particles during cooling from supersolvus and subsolvus temperatures were studied in AD730TM Ni-based superalloy using Differential Thermal Analysis (DTA). The evolution in the morphology and distribution of reprecipitated γ′ particles was investigated using Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Depending on the cooling rate, γ′ particles showed multi or monomodal distribution. The irregularity growth characteristics observed at lower cooling rates were analyzed in the context of Mullins and Sekerka theory, and allowed the determination of a critical size of γ′ particles above which morphological instability appears. Precipitation kinetics parameters were determined using a non-isothermal JMA model and DTA data. The Avrami exponent was determined to be in the 1.5–2.3 range, suggesting spherical or irregular growth. A methodology was developed to take into account the temperature dependence of the rate coefficient k(T) in the non-isothermal JMA equation. In that regard, a function for k(T) was developed. Based on the results obtained, reprecipitation kinetics models for low and high cooling rates are proposed to quantify and predict the volume fraction of reprecipitated γ′ particles during the cooling process. PMID:27338868

[Clinico-statistical study on availability of Esterman disability score for assessment of mobility difficulty in patients with visual field loss].

PubMed

Yamagata, Yoshitaka; Terada, Yuko; Suzuki, Atsushi; Mimura, Osamu

2010-01-01

The visual efficiency scale currently adopted to determine the legal grade of visual disability associated with visual field loss in Japan is not appropriate for the evaluation of disability regarding daily living activities. We investigated whether Esterman disability score (EDS) is suitable for the assessment of mobility difficulty in patients with visual field loss. The correlation between the EDS calculated from Goldmann's kinetic visual field and the degree of subjective mobility difficulty determined by a questionnaire was investigated in 164 patients with visual field loss. The correlation between the EDS determined using a program built into the Humphrey field analyzer and that calculated from Goldmann's kinetic visual field was also investigated. The EDS based on the kinetic visual field was correlated well with the degree of subjective mobility difficulty, and the EDS measured using the Humphrey field analyzer could be estimated from the kinetic visual field-based EDS. Instead of the currently adopted visual efficiency scale, EDS should be employed for the assessment of mobility difficulty in patients with visual field loss, also to establish new judgment criteria concerning the visual field.

Using gamma distribution to determine half-life of rotenone, applied in freshwater.

PubMed

Rohan, Maheswaran; Fairweather, Alastair; Grainger, Natasha

2015-09-15

Following the use of rotenone to eradicate invasive pest fish, a dynamic first-order kinetic model is usually used to determine the half-life and rate at which rotenone dissipated from the treated waterbody. In this study, we investigate the use of a stochastic gamma model for determining the half-life and rate at which rotenone dissipates from waterbodies. The first-order kinetic and gamma models produced similar values for the half-life (4.45 days and 5.33 days respectively) and days to complete dissipation (51.2 days and 52.48 days respectively). However, the gamma model fitted the data better and was more flexible than the first-order kinetic model, allowing us to use covariates and to predict a possible range for the half-life of rotenone. These benefits are particularly important when examining the influence that different environmental factors have on rotenone dissipation and when trying to predict the rate at which rotenone will dissipate during future operations. We therefore recommend that in future the gamma distribution model is used when calculating the half-life of rotenone in preference to the dynamic first-order kinetics model. Copyright © 2015 Elsevier B.V. All rights reserved.

Linear and non-linear regression analysis for the sorption kinetics of methylene blue onto activated carbon.

PubMed

Kumar, K Vasanth

2006-10-11

Batch kinetic experiments were carried out for the sorption of methylene blue onto activated carbon. The experimental kinetics were fitted to the pseudo first-order and pseudo second-order kinetics by linear and a non-linear method. The five different types of Ho pseudo second-order expression have been discussed. A comparison of linear least-squares method and a trial and error non-linear method of estimating the pseudo second-order rate kinetic parameters were examined. The sorption process was found to follow a both pseudo first-order kinetic and pseudo second-order kinetic model. Present investigation showed that it is inappropriate to use a type 1 and type pseudo second-order expressions as proposed by Ho and Blanachard et al. respectively for predicting the kinetic rate constants and the initial sorption rate for the studied system. Three correct possible alternate linear expressions (type 2 to type 4) to better predict the initial sorption rate and kinetic rate constants for the studied system (methylene blue/activated carbon) was proposed. Linear method was found to check only the hypothesis instead of verifying the kinetic model. Non-linear regression method was found to be the more appropriate method to determine the rate kinetic parameters.

Functional efficacy of adenosine A2A receptor agonists is positively correlated to their receptor residence time

PubMed Central

Guo, Dong; Mulder-Krieger, Thea; IJzerman, Adriaan P; Heitman, Laura H

2012-01-01

BACKGROUND AND PURPOSE The adenosine A2A receptor belongs to the superfamily of GPCRs and is a promising therapeutic target. Traditionally, the discovery of novel agents for the A2A receptor has been guided by their affinity for the receptor. This parameter is determined under equilibrium conditions, largely ignoring the kinetic aspects of the ligand-receptor interaction. The aim of this study was to assess the binding kinetics of A2A receptor agonists and explore a possible relationship with their functional efficacy. EXPERIMENTAL APPROACH We set up, validated and optimized a kinetic radioligand binding assay (a so-called competition association assay) at the A2A receptor from which the binding kinetics of unlabelled ligands were determined. Subsequently, functional efficacies of A2A receptor agonists were determined in two different assays: a novel label-free impedance-based assay and a more traditional cAMP determination. KEY RESULTS A simplified competition association assay yielded an accurate determination of the association and dissociation rates of unlabelled A2A receptor ligands at their receptor. A correlation was observed between the receptor residence time of A2A receptor agonists and their intrinsic efficacies in both functional assays. The affinity of A2A receptor agonists was not correlated to their functional efficacy. CONCLUSIONS AND IMPLICATIONS This study indicates that the molecular basis of different agonist efficacies at the A2A receptor lies within their different residence times at this receptor. PMID:22324512

Comparison of RAGE Hydrocode Mars Impact Model Results to Scaling Law Predictions

NASA Astrophysics Data System (ADS)

Plesko, Catherine S.; Wohletz, K. H.; Coker, R. F.; Asphaug, E.; Gittings, M. L.

2007-10-01

Impact devolatilization has been proposed by Segura et al. (2002) and Carr (1996) as a mechanism for triggering sporadic, intense precipitation on Mars. We seek to examine this hypothesis, specifically to determine the lower bound on possible energy/size scales, and thus an upper bound on the frequency of such events. To do this, we employ various analytical and numerical modeling techniques including the RAGE hydrocode. RAGE (Baltrusaitis et al. 1996) is an Eulerian Hydrocode that runs in up to three dimensions and incorporates a variety of detailed equations of state including the temperature-based SESAME tables maintained by LANL. In order to validate RAGE hydrocode results at the scale of moderate to large asteroid impacts, we compare simplified models of vertical impacts of objects of diameter 10 -100 km into homogeneous basalt targets under Martian conditions to pressure scaling law predictions (Holsapple 1993, e.g. Tables 3-4) for the same scenario. Peak pressures are important to the volatile mobilization question (Stewart and Ahrens, 2005), thus it is of primary importance for planned future modeling efforts to confirm that pressures in RAGE are well behaved. Knowledge of the final crater geometry and the fate of ejecta are not required to understand our main question: to what depth and radius are subsurface volatiles are mobilized, for a given impact and target? This effort is supported by LANL/IGPP (CSP, RFC, KHW, MLG) and by NASA PG&G "Small Bodies and Planetary Collisions" (EA).

KINETICS AND MECHANISMS OF SOIL BIOGEOCHEMICAL PROCESSES

EPA Science Inventory

The application of kinetic studies to soil chemistry is useful to determine reaction mechanisms and fate of nutrients and environmental contaminants. How deeply one wishes to query the mechanism depends on the detail sought. Reactions that involve chemical species in more than on...

Chemiomics: Network Reconstruction and Kinetics of Port Wine Aging

DOE PAGES

Monforte, Ana Rita; Jacobson, Dan; Silva Ferreira, A. C.

2015-02-11

Network reconstruction (NR) has proven to be useful in the detection and visualization of relationships among the compounds present in a Port wine aging data set. This view of the data provides a considerable amount of information with which to understand the kinetic contexts of the molecules represented by peaks in each chromatogram. The aim of this paper was to use NR together with the determination of kinetic parameters to extract more information about the mechanisms involved in Port wine aging. The volatile compounds present in samples of Port wines spanning 128 years in age were measured with the usemore » of GC-MS. After chromatogram alignment, a peak matrix was created, and all peak vectors were compared to one another to determine their Pearson correlations over time. A correlation network was created and filtered on the basis of the resulting correlation values. Some nodes in the network were further studied in experiments on Port wines stored under different conditions of oxygen and temperature in order to determine their kinetic parameters. The resulting network can be divided into three main branches. The first branch is related to compounds that do not directly correlate to age, the second branch contains compounds affected by temperature, and the third branch contains compounds associated with oxygen. Compounds clustered in the same branch of the network have similar expression patterns over time as well as the same kinetic order, thus are likely to be dependent on the same technological parameters. Network construction and visualization provides more information with which to understand the probable kinetic contexts of the molecules represented by peaks in each chromatogram. Finally, the approach described here is a powerful tool for the study of mechanisms and kinetics in complex systems and should aid in the understanding and monitoring of wine quality.« less

Predictive value of tracer studies for /sup 131/I treatment in hyperthyroid cats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broome, M.R.; Turrel, J.M.; Hays, M.T.

In 76 cats with hyperthyroidism, peak thyroidal radioiodine (/sup 131/I) uptakes and effective half-lives were determined after administration of tracer and therapeutic activities of /sup 131/I. In 6 additional hyperthyroid cats, only peak thyroidal uptakes after administration of tracer and therapeutic activities of /sup 131/I were determined. Good correlation was found between peak thyroidal uptakes of tracer and therapeutic /sup 131/I; however, only fair correlation was observed between effective half-lives. In 79% of the cats, the effective half-life for therapeutic /sup 131/I was longer than that for tracer /sup 131/I. After administration of therapeutic activity of /sup 131/I, monoexponential andmore » biphasic decay curves were observed in 51 and 16 cats, respectively. Using therapeutic kinetic data, radiation doses to the thyroid gland were calculated retrospectively on the basis of 2 methods for determining the activity of /sup 131/I administered: (1) actual administration of tracer-compensated activity and (2) hypothetic administration of uniform activity (3 mCi). Because of the good predictive ability of tracer kinetic data for the therapeutic kinetic data, the tracer-compensated radiation doses came significantly (P = 0.008) closer to the therapeutic goal than did the uniform-activity doses. In addition, the use of tracer kinetic information reduced the extent of the tendency for consistently high uniform-activity doses. A manual method for acquiring tracer kinetic data was developed and was an acceptable alternative to computerized techniques. Adoption of this method gives individuals and institutions with limited finances the opportunity to characterize the iodine kinetics in cats before proceeding with administration of therapeutic activities of /sup 131/I.« less

Metabolic control analysis using transient metabolite concentrations. Determination of metabolite concentration control coefficients.

PubMed Central

Delgado, J; Liao, J C

1992-01-01

The methodology previously developed for determining the Flux Control Coefficients [Delgado & Liao (1992) Biochem. J. 282, 919-927] is extended to the calculation of metabolite Concentration Control Coefficients. It is shown that the transient metabolite concentrations are related by a few algebraic equations, attributed to mass balance, stoichiometric constraints, quasi-equilibrium or quasi-steady states, and kinetic regulations. The coefficients in these relations can be estimated using linear regression, and can be used to calculate the Control Coefficients. The theoretical basis and two examples are discussed. Although the methodology is derived based on the linear approximation of enzyme kinetics, it yields reasonably good estimates of the Control Coefficients for systems with non-linear kinetics. PMID:1497632

Adsorption kinetics of c-Fos and c-Jun to air-water interfaces.

PubMed

Del Boca, Maximiliano; Nobre, Thatyane Morimoto; Zaniquelli, Maria Elisabete Darbello; Maggio, Bruno; Borioli, Graciela A

2007-11-01

The kinetics of adsorption to air-water interfaces of the biomembrane active transcription factors c-Fos, c-Jun and their mixtures is investigated. The adsorption process shows three distinct stages: a lag time, a fast pseudo zero-order stage, and a halting stage. The initial stage determines the course of the process, which is concentration dependent until the end of the fast stage. We show that c-Fos has faster adsorption kinetics than c-Jun over all three stages and that the interaction between both proteins is apparent in the adsorption profiles of the mixtures. Protein molecular reorganization at the interface determines the transition to the final adsorption stage of the pure proteins as well as that of the mixtures.

Substrate degradation by the proteasome: a single-molecule kinetic analysis

PubMed Central

Lu, Ying; Lee, Byung-hoon; King, Randall W; Finley, Daniel; Kirschner, Marc W

2015-01-01

To address how the configuration of conjugated ubiquitins determines the recognition of substrates by the proteasome, we analyzed the degradation kinetics of substrates with chemically defined ubiquitin configurations. Contrary to the view that a tetraubiquitin chain is the minimal signal for efficient degradation, we find that distributing the ubiquitins as diubiquitin chains provides a more efficient signal. To understand how the proteasome actually discriminates among ubiquitin configurations, we developed single-molecule assays that distinguished intermediate steps of degradation kinetically. The level of ubiquitin on a substrate drives proteasome-substrate interaction, whereas the chain structure of ubiquitin affects translocation into the axial channel on the proteasome. Together these two features largely determine the susceptibility of substrates for proteasomal degradation. PMID:25859050

Constitution of Drop-Tube-Generated Coal Chars from Vitrinite- and Inertinite-Rich South African Coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Louw, Enette B.; Mitchell, Gareth D.; Wang, Juan

The structural transformations of coal and the resultant char morphologies are strongly dependent on the initial structure and degree of thermoplasticity achieved during coal-to-char transition. These are a function of petrographic composition, rank, particle size, and heating rate and strongly affect combustion behavior. This study compares the devolatilization and subsequent combustion behavior of an inertinite-rich (87.7% dmmf) and a vitrinite-rich (91.8% dmmf) South African coal, wet-screened to a narrow particle size distribution of 200 x 400 mesh. Pyrolysis chars were generated under rapid-heating conditions (104-105 °C/s) in a drop-tube reactor to closely resemble chars generated in pulverized combustion conditions. Themore » inertinite-rich coal took ~ 400 ms to devolatilize in the drop-tube, compared to only ~ 240 ms for the vitrinite-rich sample. The chemical and physical structure (the constitution) of the chars were investigated through a range of chemical, physical, and optical characteristics including the maceral differences, and high ash yields. To evaluate the combustion reactivity non-isothermal burn-out profiles were obtained through thermogravimetrical analyses (TGA) in air. The vitrinite-rich char had on average 20% higher reaction rates than the inertinite-rich char under the various combustion conditions. The char samples were de-ashed with HCl and HF acid which resulted in an increase in combustion reactivity. The maximum reaction rate of the high-ash (36% ash yield) inertinite-rich char increased with 80% after de-ashing. While the vitrinite-rich char with an ash yield of 15%, had a 20% increase in reactivity after de-ashing. The ash acted as a barrier, and the removal of ash most likely increased the access to reactive surface area. The chemical and physical structures of the chars were characterized through a range of different analytical techniques to quantify the factors contributing to reactivity differences. The morphologies of the chars were characterized with SEM and optical microscopy, while quantitative information on the ordered nature of chars was obtained through XRD on de-ashed chars. The inertinite-rich coal experienced limited fluidity during heat-treatment, resulting in slower devolatilization, limited growth in crystallite height (11.8 to 12.6Å), only rounding of particle edges, and producing > 40% of mixed-dense type chars. The vitrinite-char showed more significant structural transformations; producing mostly (80%) extensively swollen crassisphere, tenuisphere, and network-type chars, and XRD showed a large increase in crystallite height (4.3 to 11.7Å). Nitrogen adsorption and small-angle X-ray scattering (SAXS) were utilized to compare the nitrogen surface areas and pore size distributions. Both chars were mostly mesoporous but the inertinite-rich char had double the average pore size, which also resulted in a larger nitrogen surface area since nitrogen can only access surface areas in larger pores. The BET surface area was 3.9 and 2.7 m2/g for the inertinite- and vitrinite-rich chars respectively. SAXS data showed that the vitrinite-rich char had 60% higher frequencies of pores in the micropore range. Helium porosimetry indicated that the inertinite-rich coal and resultant char had higher densities than the vitrinite coal and char; 1.6 and 2.0 g/cm3, compared to 1.3 and 1.9 g/cm3 (dry basis). Non-isothermal TGA burnout profiles showed the inertinite-rich char had a burnout temperature of 680°C, slightly higher than the vitrinite-rich char’s 650 °C. This, along with the peak shape and position in the burnout profiles indicate that the vitrinite-rich char has a higher reactivity. The higher reactivity is due to a combination of factors likely including less organization, grater porosity and access to the reactive site, less ash blocking, and char morphology differences.« less

Combined TGA-MS kinetic analysis of multistep processes. Thermal decomposition and ceramification of polysilazane and polysiloxane preceramic polymers.

PubMed

García-Garrido, C; Sánchez-Jiménez, P E; Pérez-Maqueda, L A; Perejón, A; Criado, José M

2016-10-26

The polymer-to-ceramic transformation kinetics of two widely employed ceramic precursors, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (TTCS) and polyureamethylvinylsilazane (CERASET), have been investigated using coupled thermogravimetry and mass spectrometry (TG-MS), Raman, XRD and FTIR. The thermally induced decomposition of the pre-ceramic polymer is the critical step in the synthesis of polymer derived ceramics (PDCs) and accurate kinetic modeling is key to attaining a complete understanding of the underlying process and to attempt any behavior predictions. However, obtaining a precise kinetic description of processes of such complexity, consisting of several largely overlapping physico-chemical processes comprising the cleavage of the starting polymeric network and the release of organic moieties, is extremely difficult. Here, by using the evolved gases detected by MS as a guide it has been possible to determine the number of steps that compose the overall process, which was subsequently resolved using a semiempirical deconvolution method based on the Frasier-Suzuki function. Such a function is more appropriate that the more usual Gaussian or Lorentzian functions since it takes into account the intrinsic asymmetry of kinetic curves. Then, the kinetic parameters of each constituent step were independently determined using both model-free and model-fitting procedures, and it was found that the processes obey mostly diffusion models which can be attributed to the diffusion of the released gases through the solid matrix. The validity of the obtained kinetic parameters was tested not only by the successful reconstruction of the original experimental curves, but also by predicting the kinetic curves of the overall processes yielded by different thermal schedules and by a mixed TTCS-CERASET precursor.

Evaluation of kinetic uncertainty in numerical models of petroleum generation

USGS Publications Warehouse

Peters, K.E.; Walters, C.C.; Mankiewicz, P.J.

2006-01-01

Oil-prone marine petroleum source rocks contain type I or type II kerogen having Rock-Eval pyrolysis hydrogen indices greater than 600 or 300-600 mg hydrocarbon/g total organic carbon (HI, mg HC/g TOC), respectively. Samples from 29 marine source rocks worldwide that contain mainly type II kerogen (HI = 230-786 mg HC/g TOC) were subjected to open-system programmed pyrolysis to determine the activation energy distributions for petroleum generation. Assuming a burial heating rate of 1??C/m.y. for each measured activation energy distribution, the calculated average temperature for 50% fractional conversion of the kerogen in the samples to petroleum is approximately 136 ?? 7??C, but the range spans about 30??C (???121-151??C). Fifty-two outcrop samples of thermally immature Jurassic Oxford Clay Formation were collected from five locations in the United Kingdom to determine the variations of kinetic response for one source rock unit. The samples contain mainly type I or type II kerogens (HI = 230-774 mg HC/g TOC). At a heating rate of 1??C/m.y., the calculated temperatures for 50% fractional conversion of the Oxford Clay kerogens to petroleum differ by as much as 23??C (127-150??C). The data indicate that kerogen type, as defined by hydrogen index, is not systematically linked to kinetic response, and that default kinetics for the thermal decomposition of type I or type II kerogen can introduce unacceptable errors into numerical simulations. Furthermore, custom kinetics based on one or a few samples may be inadequate to account for variations in organofacies within a source rock. We propose three methods to evaluate the uncertainty contributed by kerogen kinetics to numerical simulations: (1) use the average kinetic distribution for multiple samples of source rock and the standard deviation for each activation energy in that distribution; (2) use source rock kinetics determined at several locations to describe different parts of the study area; and (3) use a weighted-average method that combines kinetics for samples from different locations in the source rock unit by giving the activation energy distribution for each sample a weight proportional to its Rock-Eval pyrolysis S2 yield (hydrocarbons generated by pyrolytic degradation of organic matter). Copyright ?? 2006. The American Association of Petroleum Geologists. All rights reserved.

Kinetic damping in the spectra of the spherical impedance probe

NASA Astrophysics Data System (ADS)

Oberrath, J.

2018-04-01

The impedance probe is a measurement device to measure plasma parameters, such as electron density. It consists of one electrode connected to a network analyzer via a coaxial cable and is immersed into a plasma. A bias potential superposed with an alternating potential is applied to the electrode and the response of the plasma is measured. Its dynamical interaction with the plasma in an electrostatic, kinetic description can be modeled in an abstract notation based on functional analytic methods. These methods provide the opportunity to derive a general solution, which is given as the response function of the probe–plasma system. It is defined by the matrix elements of the resolvent of an appropriate dynamical operator. Based on the general solution, a residual damping for vanishing pressure can be predicted and can only be explained by kinetic effects. In this paper, an explicit response function of the spherical impedance probe is derived. Therefore, the resolvent is determined by its algebraic representation based on an expansion in orthogonal basis functions. This allows one to compute an approximated response function and its corresponding spectra. These spectra show additional damping due to kinetic effects and are in good agreement with former kinetically determined spectra.

The influence of pH adjustment on kinetics parameters in tapioca wastewater treatment using aerobic sequencing batch reactor system

NASA Astrophysics Data System (ADS)

Mulyani, Happy; Budianto, Gregorius Prima Indra; Margono, Kaavessina, Mujtahid

2018-02-01

The present investigation deals with the aerobic sequencing batch reactor system of tapioca wastewater treatment with varying pH influent conditions. This project was carried out to evaluate the effect of pH on kinetics parameters of system. It was done by operating aerobic sequencing batch reactor system during 8 hours in many tapioca wastewater conditions (pH 4.91, pH 7, pH 8). The Chemical Oxygen Demand (COD) and Mixed Liquor Volatile Suspended Solids (MLVSS) of the aerobic sequencing batch reactor system effluent at steady state condition were determined at interval time of two hours to generate data for substrate inhibition kinetics parameters. Values of the kinetics constants were determined using Monod and Andrews models. There was no inhibition constant (Ki) detected in all process variation of aerobic sequencing batch reactor system for tapioca wastewater treatment in this study. Furthermore, pH 8 was selected as the preferred aerobic sequencing batch reactor system condition in those ranging pH investigated due to its achievement of values of kinetics parameters such µmax = 0.010457/hour and Ks = 255.0664 mg/L COD.

Competition between crystallization and vitrification of the rigid amorphous fraction in poly(3-hydroxybutyrate)

NASA Astrophysics Data System (ADS)

Di Lorenzo, Maria Laura; Righetti, Maria Cristina; Gazzano, Massimo

2012-07-01

Semicrystalline polymers have a metastable nanophase structure, where the various nanophases can be crystal, liquid, glass, or mesophase. This multi-level structure is determined by a competition among self-organization, crystallization, and vitrification of the amorphous segments and is established during material processing. The kinetics of such competition is here determined for poly(3-hydroxybutyrate) (PHB), as vitrification/devitrification of the rigid amorphous fraction strongly affects crystallization kinetics of PHB.

A Census of Plasma Waves and Structures Associated With an Injection Front in the Inner Magnetosphere

NASA Astrophysics Data System (ADS)

Malaspina, David M.; Ukhorskiy, Aleksandr; Chu, Xiangning; Wygant, John

2018-04-01

Now that observations have conclusively established that the inner magnetosphere is abundantly populated with kinetic electric field structures and nonlinear waves, attention has turned to quantifying the ability of these structures and waves to scatter and accelerate inner magnetospheric plasma populations. A necessary step in that quantification is determining the distribution of observed structure and wave properties (e.g., occurrence rates, amplitudes, and spatial scales). Kinetic structures and nonlinear waves have broadband signatures in frequency space, and consequently, high-resolution time domain electric and magnetic field data are required to uniquely identify such structures and waves as well as determine their properties. However, most high-resolution fields data are collected with a strong bias toward high-amplitude signals in a preselected frequency range, strongly biasing observations of structure and wave properties. In this study, an ˜45 min unbroken interval of 16,384 samples/s field burst data, encompassing an electron injection event, is examined. This data set enables an unbiased census of the kinetic structures and nonlinear waves driven by this electron injection, as well as determination of their "typical" properties. It is found that the properties determined using this unbiased burst data are considerably different than those inferred from amplitude-biased burst data, with significant implications for wave-particle interactions due to kinetic structures and nonlinear waves in the inner magnetosphere.

Grain growth kinetics of ringwoodite and majorite garnet mixtures and implications for the rheology of the transition zone

NASA Astrophysics Data System (ADS)

Ezad, I.; Dobson, D. P.; Brodholt, J. P.; Thomson, A.; Hunt, S.

2017-12-01

The grain size of the transition zone is a poorly known but important geophysical parameter. Among others, the grain size may control the rheology, seismic attenuation and radiative thermal conductivity of the mantle. However, the grain size of the transition zone minerals ringwoodite (Mg,Fe)2SiO4 and majorite garnet MgSiO3 under appropriate zone conditions is currently unknown and there are very few experiments with which to constrain it. In order to determine the grain size of the transition zone, the grain growth kinetics must be determined for a range of mantle compositions. We have, therefore, experimentally determined the grain growth kinetics of the lowermost transition zone minerals through multi anvil experiments at University College London (UCL). This is achieved through a comprehensive set of time series experiments at pressures of 21 GPa and temperatures relevant to the transition zone. We have also determined the effect of varying water content, oxygen fugacity, iron content and aluminium content also discussed by Dobson and Mariani., (2014). Our initial grain growth experiments conducted at 1200°C and 1400°C at 18 GPa show extremely slow grain growth kinetics; time series experiments extended to 105.8 seconds are unable to produce grains larger than 100 nm. This suggests that fine-grained material at the base of the transition zone will persist on geological timescales. Such small grains size suggests that diffusion creep might be the dominant deformation mechanism in this region. Reference: Dobson, D.P., Mariani, E., 2014. The kinetics of the reaction of majorite plus ferropericlase to ringwoodite: Implications for mantle upwellings crossing the 660 km discontinuity. Earth Planet. Sci. Lett. 408, 110-118. doi:10.1016/j.epsl.2014.10.009

Use of biochemical kinetic data to determine strain relatedness among Salmonella enterica subsp. enterica isolates.

PubMed

de la Torre, E; Tello, M; Mateu, E M; Torre, E

2005-11-01

Classical biotyping characterizes strains by creating biotype profiles that consider only positive and negative results for a predefined set of biochemical tests. This method allows Salmonella subspecies to be distinguished but does not allow serotypes and phage types to be distinguished. The objective of this study was to determine the relatedness of isolates belonging to distinct Salmonella enterica subsp. enterica serotypes by using a refined biotyping process that considers the kinetics at which biochemical reactions take place. Using a Vitek GNI+ card for the identification of gram-negative organisms, we determined the biochemical kinetic reactions (28 biochemical tests) of 135 Salmonella enterica subsp. enterica strains of pig origin collected in Spain from 1997 to 2002 (59 Salmonella serotype Typhimurium strains, 25 Salmonella serotype Typhimurium monophasic variant strains, 25 Salmonella serotype Anatum strains, 12 Salmonella serotype Tilburg strains, 7 Salmonella serotype Virchow strains, 6 Salmonella serotype Choleraesuis strains, and 1 Salmonella enterica serotype 4,5,12:-:- strain). The results were expressed as the colorimetric and turbidimetric changes (in percent) and were used to enhance the classical biotype profile by adding kinetic categories. A hierarchical cluster analysis was performed by using the enhanced profiles and resulted in 14 clusters. Six major clusters grouped 94% of all isolates with a similarity of > or =95% within any given cluster, and eight clusters contained a single isolate. The six major clusters grouped not only serotypes of the same type but also phenotypic serotype variations into individual clusters. This suggests that metabolic kinetic reaction data from the biochemical tests commonly used for classic Salmonella enterica subsp. enterica biotyping can possibly be used to determine the relatedness between isolates in an easy and timely manner.

CALIBRATION OF FULL-SCALE OZONATION SYSTEMS WITH CONSERVATIVE AND REACTIVE TRACERS

EPA Science Inventory

A full-scale ozonation reactor was characterized with respect to the overall oxidation budget by coupling laboratory kinetics with reactor hydraulics. The ozone decomposition kinetics and the ratio of the OH radical to the ozone concentration were determined in laboratory batch ...

Optimization of High-Throughput Sequencing Kinetics for determining enzymatic rate constants of thousands of RNA substrates

PubMed Central

Niland, Courtney N.; Jankowsky, Eckhard; Harris, Michael E.

2016-01-01

Quantification of the specificity of RNA binding proteins and RNA processing enzymes is essential to understanding their fundamental roles in biological processes. High Throughput Sequencing Kinetics (HTS-Kin) uses high throughput sequencing and internal competition kinetics to simultaneously monitor the processing rate constants of thousands of substrates by RNA processing enzymes. This technique has provided unprecedented insight into the substrate specificity of the tRNA processing endonuclease ribonuclease P. Here, we investigate the accuracy and robustness of measurements associated with each step of the HTS-Kin procedure. We examine the effect of substrate concentration on the observed rate constant, determine the optimal kinetic parameters, and provide guidelines for reducing error in amplification of the substrate population. Importantly, we find that high-throughput sequencing, and experimental reproducibility contribute their own sources of error, and these are the main sources of imprecision in the quantified results when otherwise optimized guidelines are followed. PMID:27296633

Global Kinetic Constants for Thermal Oxidative Degradation of a Cellulosic Paper

NASA Technical Reports Server (NTRS)

Kashiwagi, Takashi; Nambu, Hidesaburo

1992-01-01

Values of global kinetic constants for pyrolysis, thermal oxidative degradation, and char oxidation of a cellulosic paper were determined by a derivative thermal gravimetric study. The study was conducted at heating rates of 0.5, 1, 1.5, 3, and 5 C/min in ambient atmospheres of nitrogen, 0.28, 1.08, 5.2 percent oxygen concentrations, and air. Sample weight loss rate, concentrations of CO, CO2, and H2O in the degradation products, and oxygen consumption were continuously measured during the experiment. Values of activation energy, preexponential factor, orders of reaction, and yields of CO, CO2, H2O, total hydrocarbons, and char for each degradation reaction were derived from the results. Heat of reaction for each reaction was determined by differential scanning calorimetry. A comparison of the calculated CO, CO2, H2O, total hydrocarbons, sample weight loss rate, and oxygen consumption was made with the measured results using the derived kinetic constants, and the accuracy of the values of kinetic constants was discussed.

Drainage and Stratification Kinetics of Foam Films

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Sharma, Vivek

2014-03-01

Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Foam lifetime, drainage kinetics and stability are strongly influenced by surfactant type (ionic vs non-ionic), and added proteins, particles or polymers modify typical responses. The rate at which fluid drains out from a foam film, i.e. drainage kinetics, is determined in the last stages primarily by molecular interactions and capillarity. Interestingly, for certain low molecular weight surfactants, colloids and polyelectrolyte-surfactant mixtures, a layered ordering of molecules, micelles or particles inside the foam films leads to a stepwise thinning phenomena called stratification. Though stratification is observed in many confined systems including foam films containing particles or polyelectrolytes, films containing globular proteins seem not to show this behavior. Using a Scheludko-type cell, we experimentally study the drainage and stratification kinetics of horizontal foam films formed by protein-surfactant mixtures, and carefully determine how the presence of proteins influences the hydrodynamics and thermodynamics of foam films.

Determination of kinetic parameters for 123-I thyroid uptake in healthy Japanese

NASA Astrophysics Data System (ADS)

Kusuhara, Hiroyuki; Maeda, Kazuya

2017-09-01

The purpose of this study was to compare the kinetic parameters for iodide thyroid accumulation in Japanese today with previously reported values. We determined the thyroid uptake of 123-I at 24 hours after the oral administration in healthy male Japanese without any diet restriction. The mean value was 16.1±5.4%, which was similar or rather lower than those previously reported in Japan (1958-1972). Kinetic model analysis was conducted to obtain the clearance for thyroid uptake from the blood circulation. The thyroid uptake clearance of 123-I was 0.540±0.073 ml/min, which was almost similar to those reported previously. There is no obvious difference in the thyroid uptake for 24 hours, and kinetic parameters in healthy Japanese for these 50 years. The fraction of distributed to the thyroid gland is lower than the ICRP reference man, and such difference must be taken into consideration to estimate the radiation exposure upon Fukushima accident in Japan.

Determination of Kinetic Parameters for the Thermal Decomposition of Parthenium hysterophorus

NASA Astrophysics Data System (ADS)

Dhaundiyal, Alok; Singh, Suraj B.; Hanon, Muammel M.; Rawat, Rekha

2018-02-01

A kinetic study of pyrolysis process of Parthenium hysterophorous is carried out by using thermogravimetric analysis (TGA) equipment. The present study investigates the thermal degradation and determination of the kinetic parameters such as activation E and the frequency factor A using model-free methods given by Flynn Wall and Ozawa (FWO), Kissinger-Akahira-Sonuse (KAS) and Kissinger, and model-fitting (Coats Redfern). The results derived from thermal decomposition process demarcate decomposition of Parthenium hysterophorous among the three main stages, such as dehydration, active and passive pyrolysis. It is shown through DTG thermograms that the increase in the heating rate caused temperature peaks at maximum weight loss rate to shift towards higher temperature regime. The results are compared with Coats Redfern (Integral method) and experimental results have shown that values of kinetic parameters obtained from model-free methods are in good agreement. Whereas the results obtained through Coats Redfern model at different heating rates are not promising, however, the diffusion models provided the good fitting with the experimental data.

Virus Neutralisation: New Insights from Kinetic Neutralisation Curves

PubMed Central

Magnus, Carsten

2013-01-01

Antibodies binding to the surface of virions can lead to virus neutralisation. Different theories have been proposed to determine the number of antibodies that must bind to a virion for neutralisation. Early models are based on chemical binding kinetics. Applying these models lead to very low estimates of the number of antibodies needed for neutralisation. In contrast, according to the more conceptual approach of stoichiometries in virology a much higher number of antibodies is required for virus neutralisation by antibodies. Here, we combine chemical binding kinetics with (virological) stoichiometries to better explain virus neutralisation by antibody binding. This framework is in agreement with published data on the neutralisation of the human immunodeficiency virus. Knowing antibody reaction constants, our model allows us to estimate stoichiometrical parameters from kinetic neutralisation curves. In addition, we can identify important parameters that will make further analysis of kinetic neutralisation curves more valuable in the context of estimating stoichiometries. Our model gives a more subtle explanation of kinetic neutralisation curves in terms of single-hit and multi-hit kinetics. PMID:23468602

Enzymatic Kinetic Isotope Effects from First-Principles Path Sampling Calculations.

PubMed

Varga, Matthew J; Schwartz, Steven D

2016-04-12

In this study, we develop and test a method to determine the rate of particle transfer and kinetic isotope effects in enzymatic reactions, specifically yeast alcohol dehydrogenase (YADH), from first-principles. Transition path sampling (TPS) and normal mode centroid dynamics (CMD) are used to simulate these enzymatic reactions without knowledge of their reaction coordinates and with the inclusion of quantum effects, such as zero-point energy and tunneling, on the transferring particle. Though previous studies have used TPS to calculate reaction rate constants in various model and real systems, it has not been applied to a system as large as YADH. The calculated primary H/D kinetic isotope effect agrees with previously reported experimental results, within experimental error. The kinetic isotope effects calculated with this method correspond to the kinetic isotope effect of the transfer event itself. The results reported here show that the kinetic isotope effects calculated from first-principles, purely for barrier passage, can be used to predict experimental kinetic isotope effects in enzymatic systems.

Combustor kinetic energy efficiency analysis of the hypersonic research engine data

NASA Astrophysics Data System (ADS)

Hoose, K. V.

1993-11-01

A one-dimensional method for measuring combustor performance is needed to facilitate design and development scramjet engines. A one-dimensional kinetic energy efficiency method is used for measuring inlet and nozzle performance. The objective of this investigation was to assess the use of kinetic energy efficiency as an indicator for scramjet combustor performance. A combustor kinetic energy efficiency analysis was performed on the Hypersonic Research Engine (HRE) data. The HRE data was chosen for this analysis due to its thorough documentation and availability. The combustor, inlet, and nozzle kinetic energy efficiency values were utilized to determine an overall engine kinetic energy efficiency. Finally, a kinetic energy effectiveness method was developed to eliminate thermochemical losses from the combustion of fuel and air. All calculated values exhibit consistency over the flight speed range. Effects from fuel injection, altitude, angle of attack, subsonic-supersonic combustion transition, and inlet spike position are shown and discussed. The results of analyzing the HRE data indicate that the kinetic energy efficiency method is effective as a measure of scramjet combustor performance.

Determination of Percent Body Fat Using 3D Whole Body Laser Scanning: A Preliminary Investigation

DTIC Science & Technology

2006-11-01

S.B., Lohman, T.G., Wang, Z., and Going, S.B., 2005: Human body composition: Human Kinetics : Champaign, IL. Heyward, V.H. and Wagner, D.R...2004: Applied body composition assessment: Human Kinetics : Champaign, IL. Hodgdon, J.A., and Beckett, M.B., 1984a: Prediction of percent body fat...ethnicity. In: Human body Composition., Heymsfield, S.B., Lohman, T.G., Wang, Z., and Going, S.B (eds.). Human Kinetics : Champaign, IL. Marriott

Determining Li+-Coupled Redox Targeting Reaction Kinetics of Battery Materials with Scanning Electrochemical Microscopy.

PubMed

Yan, Ruiting; Ghilane, Jalal; Phuah, Kia Chai; Pham Truong, Thuan Nguyen; Adams, Stefan; Randriamahazaka, Hyacinthe; Wang, Qing

2018-02-01

The redox targeting reaction of Li + -storage materials with redox mediators is the key process in redox flow lithium batteries, a promising technology for next-generation large-scale energy storage. The kinetics of the Li + -coupled heterogeneous charge transfer between the energy storage material and redox mediator dictates the performance of the device, while as a new type of charge transfer process it has been rarely studied. Here, scanning electrochemical microscopy (SECM) was employed for the first time to determine the interfacial charge transfer kinetics of LiFePO 4 /FePO 4 upon delithiation and lithiation by a pair of redox shuttle molecules FcBr 2 + and Fc. The effective rate constant k eff was determined to be around 3.70-6.57 × 10 -3 cm/s for the two-way pseudo-first-order reactions, which feature a linear dependence on the composition of LiFePO 4 , validating the kinetic process of interfacial charge transfer rather than bulk solid diffusion. In addition, in conjunction with chronoamperometry measurement, the SECM study disproves the conventional "shrinking-core" model for the delithiation of LiFePO 4 and presents an intriguing way of probing the phase boundary propagations induced by interfacial redox reactions. This study demonstrates a reliable method for the kinetics of redox targeting reactions, and the results provide useful guidance for the optimization of redox targeting systems for large-scale energy storage.

Barrierless growth of precursor-free, ultrafast laser-fragmented noble metal nanoparticles by colloidal atom clusters - A kinetic in situ study.

PubMed

Jendrzej, Sandra; Gökce, Bilal; Amendola, Vincenzo; Barcikowski, Stephan

2016-02-01

Unintended post-synthesis growth of noble metal colloids caused by excess amounts of reactants or highly reactive atom clusters represents a fundamental problem in colloidal chemistry, affecting product stability or purity. Hence, quantified kinetics could allow defining nanoparticle size determination in dependence of the time. Here, we investigate in situ the growth kinetics of ps pulsed laser-fragmented platinum nanoparticles in presence of naked atom clusters in water without any influence of reducing agents or surfactants. The nanoparticle growth is investigated for platinum covering a time scale of minutes to 50days after nanoparticle generation, it is also supplemented by results obtained from gold and palladium. Since a minimum atom cluster concentration is exceeded, a significant growth is determined by time resolved UV/Vis spectroscopy, analytical disc centrifugation, zeta potential measurement and transmission electron microscopy. We suggest a decrease of atom cluster concentration over time, since nanoparticles grow at the expense of atom clusters. The growth mechanism during early phase (<1day) of laser-synthesized colloid is kinetically modeled by rapid barrierless coalescence. The prolonged slow nanoparticle growth is kinetically modeled by a combination of coalescence and Lifshitz-Slyozov-Wagner kinetic for Ostwald ripening, validated experimentally by the temperature dependence of Pt nanoparticle size and growth quenching by Iodide anions. Copyright © 2015. Published by Elsevier Inc.

A Study of the Optimal Model of the Flotation Kinetics of Copper Slag from Copper Mine BOR

NASA Astrophysics Data System (ADS)

Stanojlović, Rodoljub D.; Sokolović, Jovica M.

2014-10-01

In this study the effect of mixtures of copper slag and flotation tailings from copper mine Bor, Serbia on the flotation results of copper recovery and flotation kinetics parameters in a batch flotation cell has been investigated. By simultaneous adding old flotation tailings in the ball mill at the rate of 9%, it is possible to increase copper recovery for about 20%. These results are compared with obtained copper recovery of pure copper slag. The results of batch flotation test were fitted by MatLab software for modeling the first-order flotation kinetics in order to determine kinetics parameters and define an optimal model of the flotation kinetics. Six kinetic models are tested on the batch flotation copper recovery against flotation time. All models showed good correlation, however the modified Kelsall model provided the best fit.

Multi-scale analysis of compressible fluctuations in the solar wind

NASA Astrophysics Data System (ADS)

Roberts, Owen W.; Narita, Yasuhito; Escoubet, C.-Philippe

2018-01-01

Compressible plasma turbulence is investigated in the fast solar wind at proton kinetic scales by the combined use of electron density and magnetic field measurements. Both the scale-dependent cross-correlation (CC) and the reduced magnetic helicity (σm) are used in tandem to determine the properties of the compressible fluctuations at proton kinetic scales. At inertial scales the turbulence is hypothesised to contain a mixture of Alfvénic and slow waves, characterised by weak magnetic helicity and anti-correlation between magnetic field strength B and electron density ne. At proton kinetic scales the observations suggest that the fluctuations have stronger positive magnetic helicities as well as strong anti-correlations within the frequency range studied. These results are interpreted as being characteristic of either counter-propagating kinetic Alfvén wave packets or a mixture of anti-sunward kinetic Alfvén waves along with a component of kinetic slow waves.

Nonlinear Analyte Concentration Gradients for One-Step Kinetic Analysis Employing Optical Microring Resonators

PubMed Central

Marty, Michael T.; Kuhnline Sloan, Courtney D.; Bailey, Ryan C.; Sligar, Stephen G.

2012-01-01

Conventional methods to probe the binding kinetics of macromolecules at biosensor surfaces employ a stepwise titration of analyte concentrations and measure the association and dissociation to the immobilized ligand at each concentration level. It has previously been shown that kinetic rates can be measured in a single step by monitoring binding as the analyte concentration increases over time in a linear gradient. We report here the application of nonlinear analyte concentration gradients for determining kinetic rates and equilibrium binding affinities in a single experiment. A versatile nonlinear gradient maker is presented, which is easily applied to microfluidic systems. Simulations validate that accurate kinetic rates can be extracted for a wide range of association and dissociation rates, gradient slopes and curvatures, and with models for mass transport. The nonlinear analyte gradient method is demonstrated with a silicon photonic microring resonator platform to measure prostate specific antigen-antibody binding kinetics. PMID:22686186

Nonlinear analyte concentration gradients for one-step kinetic analysis employing optical microring resonators.

PubMed

Marty, Michael T; Sloan, Courtney D Kuhnline; Bailey, Ryan C; Sligar, Stephen G

2012-07-03

Conventional methods to probe the binding kinetics of macromolecules at biosensor surfaces employ a stepwise titration of analyte concentrations and measure the association and dissociation to the immobilized ligand at each concentration level. It has previously been shown that kinetic rates can be measured in a single step by monitoring binding as the analyte concentration increases over time in a linear gradient. We report here the application of nonlinear analyte concentration gradients for determining kinetic rates and equilibrium binding affinities in a single experiment. A versatile nonlinear gradient maker is presented, which is easily applied to microfluidic systems. Simulations validate that accurate kinetic rates can be extracted for a wide range of association and dissociation rates, gradient slopes, and curvatures, and with models for mass transport. The nonlinear analyte gradient method is demonstrated with a silicon photonic microring resonator platform to measure prostate specific antigen-antibody binding kinetics.

Limiting Energy Dissipation Induces Glassy Kinetics in Single-Cell High-Precision Responses

PubMed Central

Das, Jayajit

2016-01-01

Single cells often generate precise responses by involving dissipative out-of-thermodynamic-equilibrium processes in signaling networks. The available free energy to fuel these processes could become limited depending on the metabolic state of an individual cell. How does limiting dissipation affect the kinetics of high-precision responses in single cells? I address this question in the context of a kinetic proofreading scheme used in a simple model of early-time T cell signaling. Using exact analytical calculations and numerical simulations, I show that limiting dissipation qualitatively changes the kinetics in single cells marked by emergence of slow kinetics, large cell-to-cell variations of copy numbers, temporally correlated stochastic events (dynamic facilitation), and ergodicity breaking. Thus, constraints in energy dissipation, in addition to negatively affecting ligand discrimination in T cells, can create a fundamental difficulty in determining single-cell kinetics from cell-population results. PMID:26958894

Cure Kinetics of Benzoxazine/Cycloaliphatic Epoxy Resin by Differential Scanning Calorimetry

NASA Astrophysics Data System (ADS)

Gouni, Sreeja Reddy

Understanding the curing kinetics of a thermoset resin has a significant importance in developing and optimizing curing cycles in various industrial manufacturing processes. This can assist in improving the quality of final product and minimizing the manufacturing-associated costs. One approach towards developing such an understanding is to formulate kinetic models that can be used to optimize curing time and temperature to reach a full cure state or to determine time to apply pressure in an autoclave process. Various phenomenological reaction models have been used in the literature to successfully predict the kinetic behavior of a thermoset system. The current research work was designed to investigate the cure kinetics of Bisphenol-A based Benzoxazine (BZ-a) and Cycloaliphatic epoxy resin (CER) system under isothermal and nonisothermal conditions by Differential Scanning Calorimetry (DSC). The cure characteristics of BZ-a/CER copolymer systems with 75/25 wt% and 50/50 wt% have been studied and compared to that of pure benzoxazine under nonisothermal conditions. The DSC thermograms exhibited by these BZ-a/CER copolymer systems showed a single exothermic peak, indicating that the reactions between benzoxazine-benzoxazine monomers and benzoxazine-cycloaliphatic epoxy resin were interactive and occurred simultaneously. The Kissinger method and isoconversional methods including Ozawa-Flynn-Wall and Freidman were employed to obtain the activation energy values and determine the nature of the reaction. The cure behavior and the kinetic parameters were determined by adopting a single step autocatalytic model based on Kamal and Sourour phenomenological reaction model. The model was found to suitably describe the cure kinetics of copolymer system prior to the diffusion-control reaction. Analyzing and understanding the thermoset resin system under isothermal conditions is also important since it is the most common practice in the industry. The BZ-a/CER copolymer system with 75/25 wt% ratio which exhibited high glass transition temperature compared to polybenzoxazine was investigated under isothermal conditions. The copolymer system exhibited the maximum reaction rate at an intermediate degree of cure (20 to 40%), indicating that the reaction was autocatalytic. Similar to the nonisothermal cure kinetics, Kamal and Sourour phenomenological reaction model was adopted to determine the kinetic behavior of the system. The theoretical values based on the developed model showed a deviation from the obtained experimental values, which indicated the change in kinetics from a reaction-controlled mechanism to a diffusion-controlled mechanism with increasing reaction conversion. To substantiate the hypothesis, Fournier et al's diffusion factor was introduced into the model, resulting in an agreement between the theoretical and experimental values. The changes in cross-linking density and the glass transition temperature (Tg) with increasing epoxy concentration were investigated under Dynamic Mechanical Analyzer (DMA). The BZ-a/CER copolymer system with the epoxy content of less than 40 wt% exhibited the greatest Tg and cross-linking density compared to benzoxazine homopolymer and other ratios.

Kinetic Determinants of Reactive Strength in Highly Trained Sprint Athletes.

PubMed

Douglas, Jamie; Pearson, Simon; Ross, Angus; McGuigan, Mike

2018-06-01

Douglas, J, Pearson, S, Ross, A, and McGuigan, M. Kinetic determinants of reactive strength in highly trained sprint athletes. J Strength Cond Res 32(6): 1562-1570, 2018-The purpose of this study was to determine the braking and propulsive phase kinetic variables underpinning reactive strength in highly trained sprint athletes in comparison with a nonsprint-trained control group. Twelve highly trained sprint athletes and 12 nonsprint-trained participants performed drop jumps (DJs) from 0.25, 0.50, and 0.75 m onto a force plate. One familiarization session was followed by an experimental testing session within the same week. Reactive strength index (RSI), contact time, flight time, and leg stiffness were determined. Kinetic variables including force, power, and impulse were assessed within the braking and propulsive phases. Sprint-trained athletes demonstrated higher RSI vs. nonsprint-trained participants across all drop heights {3.02 vs. 2.02; ES (±90% confidence limit [CL]): 3.11 ± 0.86}. This difference was primarily attained by briefer contact times (0.16 vs. 0.22 seconds; effect size [ES]: -1.49 ± 0.53) with smaller differences observed for flight time (0.50 vs. 0.46 seconds; ES: 0.53 ± 0.58). Leg stiffness, braking and propulsive phase force, and power were higher in sprint-trained athletes. Very large differences were observed in mean braking force (51 vs. 38 N·kg; ES: 2.57 ± 0.73) which was closely associated with contact time (r ±90% CL: -0.93 ± 0.05). Sprint-trained athletes exhibited superior reactive strength than nonsprint-trained participants. This was due to the ability to strike the ground with a stiffer leg spring, an enhanced expression of braking force, and possibly an increased utilization of elastic structures. The DJ kinetic analysis provides additional insight into the determinants of reactive strength which may inform subsequent testing and training.

Dynamic identification of growth and survival kinetic parameters of microorganisms in foods

USDA-ARS?s Scientific Manuscript database

Inverse analysis is a mathematical method used in predictive microbiology to determine the kinetic parameters of microbial growth and survival in foods. The traditional approach in inverse analysis relies on isothermal experiments that are time-consuming and labor-intensive, and errors are accumula...

Quantifying fat, oil, and grease deposit formation kinetics

USDA-ARS?s Scientific Manuscript database

Fat, oil, and grease (FOG) deposits formed in sanitary sewers are calcium-based saponified solids that are responsible for a significant number of nationwide sanitary sewer overflows (SSOs) across United States. In the current study, the kinetics of lab-based saponified solids were determined to un...

Kinetics of nickel electrodeposition from low electrolyte concentration and at a narrow interelectrode gap

NASA Astrophysics Data System (ADS)

Widayatno, Tri

2015-12-01

Electrodeposition of nickel onto copper in a system of low Ni2+ concentration and at a narrow interelectrode gap has been carried out. This electrochemical system was required for maskless pattern transfer through electroplating (Enface technique). Kinetics of Electrochemical reaction of Nickel is relatively slow, where such electrochemical system has never been used in this technology. Study on the kinetics of the electrochemical reaction of nickel in such system is essential due to the fact that the quality of an electrodeposited nickel is affected by kinetics. Analytical and graphical methods were utilised to determine kinetic parameters. The kinetic model was approximated by Butler-Volmer and j-η equation. Kinetic parameters such as exchange current density (j0) and charge transfer coefficient (α) were also graphically determined using the plot of η vs. log|j| known as Tafel plot. The polarisation data for an unstirred 0.19 M nickel sulfamate solution at 0.5 mV/s scan rate and RDE system was used. The results indicate that both methods are fairly accurate. For the analytical, the Tafel slope, the exchange current density, and charge transfer coefficient were found to be 149 mV/dec, 1.60 × 10-4 mA/cm2, and 0.39 respectively, whilst for the graphical method were 159 mV/dec, 3.16 × 10-4 mA/cm2, and 0.37. The kinetics parameters in this current study were also compared to those in literature. Significant differences were observed which might be due to the effect of composition and concentration of the electrolytes, operating temperature, and pH leading to the different reaction mechanism. However, the results obtained in this work are in the range of acceptable values. These kinetic parameters will then be used in further study of nickel deposition by modelling and simulation

The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

NASA Astrophysics Data System (ADS)

Basuki, Rahmat; Santosa, Sri Juari; Rusdiarso, Bambang

2017-03-01

Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g-1, equilibrium constant (K) was 5.651 (mol/L)-1, and multilayer sorption capacity was 2.646 × 10-2 mol g-1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. Adsorption rate constant (ka) from this novel expression was 43.178 min-1 (mol/L)-1 and desorption rate constant (kd) was 1.250 × 10-2 min-1. Application of the kinetics model on sorption Cd(II) onto HD-HA showed the nearly all of models gave a good linearity. However, only this proposed kinetics expression has good relation with Langmuir model. The novel kinetics expression proposed in this paper seems to be more realistic and reasonable and close to the experimental real condition because the value of ka/kd (3452 (mol/L)-1) was fairly close with K from Langmuir isotherm model (5651 (mol/L)-1). Comparison of this novel kinetics expression with well-known Lagergren pseudo-first order kinetics and Ho pseudo-second order kinetics was also critically discussed in this paper.

The effects of surface chemistry of mesoporous silica materials and solution pH on kinetics of molsidomine adsorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolinina, E.S.; Parfenyuk, E.V., E-mail: terrakott37@mail.ru

2014-01-15

Adsorption kinetics of molsidomine on mesoporous silica material (UMS), the phenyl- (PhMS) and mercaptopropyl-functionalized (MMS) derivatives from solution with different pH and 298 K was studied. The adsorption kinetics was found to follow the pseudo-second-order kinetic model for all studied silica materials and pH. Effects of surface functional groups and pH on adsorption efficiency and kinetic adsorption parameters were investigated. At all studied pH, the highest molsidomine amount is adsorbed on PhMS due to π–π interactions and hydrogen bonding between surface groups of PhMS and molsidomine molecules. An increase of pH results in a decrease of the amounts of adsorbedmore » molsidomine onto the silica materials. Furthermore, the highest adsorption rate kinetically evaluated using a pseudo-second-order model, is observed onto UMS and it strongly depends on pH. The mechanism of the adsorption process was determined from the intraparticle diffusion and Boyd kinetic film–diffusion models. The results showed that the molsidomine adsorption on the silica materials is controlled by film diffusion. Effect of pH on the diffusion parameters is discussed. - Graphical abstract: The kinetic study showed that the k{sub 2} value, the rate constant of pseudo-second order kinetic model, is the highest for molsidomine adsorption on UMS and strongly depends on pH because it is determined by availability and accessibility of the reaction sites of the adsorbents molsidomine binding. Display Omitted - Highlights: • The adsorption capacities of UMS, PhMS and MMS were dependent on the pH. • At all studied pH, the highest molsidomine amount is adsorbed on PhMS. • The highest adsorption rate, k{sub 2}, is observed onto UMS and strongly depends on pH. • Film diffusion was the likely rate-limiting step in the adsorption process.« less

Redefining the utility of the three-isotope method

NASA Astrophysics Data System (ADS)

Cao, Xiaobin; Bao, Huiming

2017-09-01

The equilibrium isotope fractionation factor αeq is a fundamental parameter in the study of stable isotope effects. Experimentally, it has been difficult to establish that a system has attained equilibrium. The three-isotope method, using the initial trajectory of changing isotope ratios (e.g. 16O, 17O, and 18O) to deduce the final equilibrium point of isotope exchange, has long been hailed as the most rigorous experimental approach. However, over the years some researchers have cautioned on the limitations of this method, but the foundation of three-isotope method has not been properly examined and the method is still widely used in calibrating αeq for both traditional and increasingly non-traditional isotope systems today. Here, using water-water and dissolved CO2-water oxygen exchange as model systems, we conduct an isotopologues-specific kinetic analysis of the exchange processes and explore the underlying assumptions and validity of the three-isotope method. We demonstrate that without knowing the detailed exchange kinetics a priori the three-isotope method cannot lead to a reliable αeq. For a two-reservoir exchanging system, α determined by this method may be αeq, kinetic isotope effect, or apparent kinetic isotope effect, which can all bear different values. When multiple reservoirs exist during exchange, the evolving trajectory can be complex and hard to predict. Instead of being a tool for αeq determination, three-isotope method should be used as a tool for studying kinetic isotope effect, apparent kinetic isotope effect, and detailed exchange kinetics in diverse systems.

Automated Transition State Theory Calculations for High-Throughput Kinetics.

PubMed

Bhoorasingh, Pierre L; Slakman, Belinda L; Seyedzadeh Khanshan, Fariba; Cain, Jason Y; West, Richard H

2017-09-21

A scarcity of known chemical kinetic parameters leads to the use of many reaction rate estimates, which are not always sufficiently accurate, in the construction of detailed kinetic models. To reduce the reliance on these estimates and improve the accuracy of predictive kinetic models, we have developed a high-throughput, fully automated, reaction rate calculation method, AutoTST. The algorithm integrates automated saddle-point geometry search methods and a canonical transition state theory kinetics calculator. The automatically calculated reaction rates compare favorably to existing estimated rates. Comparison against high level theoretical calculations show the new automated method performs better than rate estimates when the estimate is made by a poor analogy. The method will improve by accounting for internal rotor contributions and by improving methods to determine molecular symmetry.

Kinetics of the sorption of triterpene saponin by hypercrosslinked polystyrene

NASA Astrophysics Data System (ADS)

Mironenko, N. V.; Brezhneva, T. A.; Selemenev, V. F.

2013-03-01

The kinetics of sorption of triterpene saponin by the polymer sorbent NM-200 is considered. The influence of the surface activity of glycoside on the rate of formation and structure of the adsorption layer on the sorbent's surface is established. The rate-determining step of sorption is found to be diffusion into the sorbent grain. The value of the activation energy demonstrates the determining role of dispersion forces in the interaction between triterpene saponin and the polymer sorbent MN-200.

Evaluation of the Kinetic Property of Single-Molecule Junctions by Tunneling Current Measurements.

PubMed

Harashima, Takanori; Hasegawa, Yusuke; Kiguchi, Manabu; Nishino, Tomoaki

2018-01-01

We investigated the formation and breaking of single-molecule junctions of two kinds of dithiol molecules by time-resolved tunneling current measurements in a metal nanogap. The resulting current trajectory was statistically analyzed to determine the single-molecule conductance and, more importantly, to reveal the kinetic property of the single-molecular junction. These results suggested that combining a measurement of the single-molecule conductance and statistical analysis is a promising method to uncover the kinetic properties of the single-molecule junction.

Kinetic parameters and structural variations in Cu-Al-Mn and Cu-Al-Mn-Mg shape memory alloys

NASA Astrophysics Data System (ADS)

Canbay, Canan Aksu

2017-02-01

In this work polycrystalline Cu-Al-Mn and Cu-Al-Mn-Mg SMAs were fabricated by arc melting. The thermal analysis was made to determine the characteristic transformation temperatures of the samples and kinetic parameters. Also the effect of Mg on transformation temperatures and kinetic parameters detected. The structural analysis was made to designate the diffraction planes of martensite phase at room temperature and this was supported by optical measurement observations.

Nonisothermal Analysis of Solution Kinetics by Spreadsheet Simulation

ERIC Educational Resources Information Center

de Levie, Robert

2012-01-01

A fast and generally applicable alternative solution to the problem of determining the useful shelf life of medicinal solutions is described. It illustrates the power and convenience of the combination of numerical simulation and nonlinear least squares with a practical pharmaceutical application of chemical kinetics and thermodynamics, validated…

Monochloramine disinfection kinetics of Nitrosomonas europaea by propidium monoazide quantitative PCR and Live/Dead BacLight Methods

EPA Science Inventory

Monochloramine disinfection kinetics were determined for the pure culture ammonia-oxidizing bacterium Nitrosomonas europaea (ATCC 19718) by two culture independent methods: (1) LIVE/DEAD® BacLight™ (LD) and (2) propidium monoazide quantitative PCR (PMA-qPCR). Both methods were f...

Growth Kinetics and Modeling of ZnO Nanoparticles

ERIC Educational Resources Information Center

Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.; Voelcker, Nico H.; Ford, Michael J.; Waclawik, Eric R.

2005-01-01

The technique for producing quantum-sized zinc oxide (ZnO) particles is much safer than a technique that used hydrogen sulfide gas to produce cadmium sulfide and zinc sulfide nanoparticles. A further advantage of this method is the ability to sample the solution over time and hence determine the growth kinetics.

Oxidation kinetics of some Ni-Cr alloys.

PubMed

Baran, G

1983-01-01

Oxidation kinetics of four Ni-Cr alloys and a high-purity nickel standard was determined under isothermal conditions in an air atmosphere. In addition, weight gains of the alloys were measured during a simulated pre-oxidation treatment. The alloys' behavior suggests that mechanisms of oxidation vary with temperature and alloy composition.

Kinetic Fluorescence Experiment for the Determination of Thiamine.

ERIC Educational Resources Information Center

Bower, Nathan W.

1982-01-01

Background information, procedures, and typical results are provided for an experiment which integrates principles of fluorescent and kinetic analysis. In the procedure, mecuric chloride is used as a selective oxidizing agent for converting thiamine to thiochrome. The experiment can be completed in a two-hour laboratory period. (Author/JN)

Kinetics of Carbaryl Hydrolysis: An Undergraduate Environmental Chemistry Laboratory

ERIC Educational Resources Information Center

Hawker, Darryl

2015-01-01

Kinetics is an important part of undergraduate environmental chemistry curricula and relevant laboratory exercises are helpful in assisting students to grasp concepts. Such exercises are also useful in general chemistry courses because students can see relevance to real-world issues. The laboratory exercise described here involves determination of…

A novel approach to the experimental study on methane/steam reforming kinetics using the Orthogonal Least Squares method

NASA Astrophysics Data System (ADS)

Sciazko, Anna; Komatsu, Yosuke; Brus, Grzegorz; Kimijima, Shinji; Szmyd, Janusz S.

2014-09-01

For a mathematical model based on the result of physical measurements, it becomes possible to determine their influence on the final solution and its accuracy. However, in classical approaches, the influence of different model simplifications on the reliability of the obtained results are usually not comprehensively discussed. This paper presents a novel approach to the study of methane/steam reforming kinetics based on an advanced methodology called the Orthogonal Least Squares method. The kinetics of the reforming process published earlier are divergent among themselves. To obtain the most probable values of kinetic parameters and enable direct and objective model verification, an appropriate calculation procedure needs to be proposed. The applied Generalized Least Squares (GLS) method includes all the experimental results into the mathematical model which becomes internally contradicted, as the number of equations is greater than number of unknown variables. The GLS method is adopted to select the most probable values of results and simultaneously determine the uncertainty coupled with all the variables in the system. In this paper, the evaluation of the reaction rate after the pre-determination of the reaction rate, which was made by preliminary calculation based on the obtained experimental results over a Nickel/Yttria-stabilized Zirconia catalyst, was performed.

Determination of biodegradability kinetics of RCRA compounds using respirometry for structure-activity relationships

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tabak, H.H.; Desai, S.; Govind, R.

1990-01-01

Electrolytic respirometry is attaining prominence in biodegradation studies and is becoming one of the more suitable experimental methods for measuring the biodegradability and the kinetics of biodegradation of toxic organic compounds by the sewage, sludge, and soil microbiota and for determining substrate inhibitory effects to microorganisms in wastewater treatment systems. The purpose of the study was to obtain information on biological treatability of the benzene, phenol, phthalate, ketone organics and of the Superfund CERCLA organics bearing wastes in wastewater treatment systems which will support the development of an EPA technical guidance document on the discharge of the above organics tomore » POTWs. The paper discusses the experimental design and procedural steps for the respirometric biodegradation and toxicity testing approach for individual organics or specific industrial wastes at different concentration levels in a mineral salts medium. A developed multi-level protocol is presented for determination of the biodegradability, microbial acclimation to toxic substrates and first order kinetic parameters of biodegradation for estimation of the Monod kinetic parameter of toxic organic compounds, in order to correlate the extent and rate of biodegradation with a predictive model based on chemical properties and molecular structure of these compounds. Respirometric biodegradation/inhibition and biokinetic data are provided for representative RCRA alkyl benzene and ketone organics.« less

Kinetics of methane hydrate decomposition studied via in situ low temperature X-ray powder diffraction.

PubMed

Everett, S Michelle; Rawn, Claudia J; Keffer, David J; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy J

2013-05-02

Gas hydrate is known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Based on results from the decomposition of three nominally similar methane hydrate samples, the kinetics of two regions, 180-200 and 230-260 K, within the overall decomposition range 140-260 K, were studied by in situ low temperature X-ray powder diffraction. The kinetic rate constants, k(a), and the reaction mechanisms, n, for ice formation from methane hydrate were determined by the Avrami model within each region, and activation energies, E(a), were determined by the Arrhenius plot. E(a) determined from the data for 180-200 K was 42 kJ/mol and for 230-260 K was 22 kJ/mol. The higher E(a) in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

Utilization of integrated Michaelis-Menten equations for enzyme inhibition diagnosis and determination of kinetic constants using Solver supplement of Microsoft Office Excel.

PubMed

Bezerra, Rui M F; Fraga, Irene; Dias, Albino A

2013-01-01

Enzyme kinetic parameters are usually determined from initial rates nevertheless, laboratory instruments only measure substrate or product concentration versus reaction time (progress curves). To overcome this problem we present a methodology which uses integrated models based on Michaelis-Menten equation. The most severe practical limitation of progress curve analysis occurs when the enzyme shows a loss of activity under the chosen assay conditions. To avoid this problem it is possible to work with the same experimental points utilized for initial rates determination. This methodology is illustrated by the use of integrated kinetic equations with the well-known reaction catalyzed by alkaline phosphatase enzyme. In this work nonlinear regression was performed with the Solver supplement (Microsoft Office Excel). It is easy to work with and track graphically the convergence of SSE (sum of square errors). The diagnosis of enzyme inhibition was performed according to Akaike information criterion. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

PubMed

Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

2017-05-09

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Susan M; Rawn, Claudia J; Keffer, David J.

Gas hydrates are known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice termed self-preservation or anomalous preservation. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Two regions of slowed decomposition for methane hydrate, 180 200 K and 230 260 K, were observed, and the kinetics were studied by in situ low temperature x-ray powder diffraction. The kinetic constants for ice formation from methane hydrate were determined by the Avrami model within each region and activation energies, Ea, were determined by the Arrhenius plot.more » Ea determined from the data for 180 200 K was 42 kJ/mol and for 230 260 K was 22 kJ/mol. The higher Ea in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.« less

Determination of thiourea in fruit juice by a kinetic spectrophotometric method.

PubMed

Abbasi, Shahryar; Khani, Hossein; Hosseinzadeh, Laleh; Safari, Zhila

2010-02-15

A catalytic kinetic method is described for determination of trace levels of thiourea based on its catalytic effect on the oxidation of Janus green (JG) by potassium iodate in hydrochloric acid media. The reaction was monitored by measuring the decrease in absorbance of the dye at 610 nm after 25 min. The effect of some factors on the reaction speed was investigated. The developed method allowed the determination of thiourea in range of 0.01-12.00 mg L(-1) with good precision, accuracy and the detection limit was 0.008 mg L(-1). Most of foreign species do not interfere with the determination. The method was found to be sensitive, selective and was applied to the determination of thiourea in fruit juices and orange peel.

Spectral study of wintertime kinetic energy of the Northern Hemisphere in the troposphere

NASA Technical Reports Server (NTRS)

Lee, H. N.; Zhao, Z.; Kao, S. K.

1983-01-01

Characteristics of the kinetic energy of wind fields at various pressure levels were analyzed, and significant wavenumbers in the wavenumber-frequency domain were identified. The nonlinear interaction terms of the kinetic energy equation were examined, and the distribution of the kinetic energy at the 850 mb, 500 mb, and 200 mb levels was calculated. A 5 deg latitude-longitude square grid was used, with NMC data for the 1975-1976 winter in the 20-60 deg N at 500 mb and 20-85 deg N for the 200 mb and 850 mb levels. The kinetic energy distribution was determined to be geography-dependent, with wavenumbers 6-9 westerly waves in the midfrequency range contributing significantly to kinetic energy maxima over the North Pacific and the east coast of North America. The contribution of the nonlinear interactions of these waves, which correspond to the longitudinal convergence of the kinetic energy flux, was found to be larger than the meridional convergence of the kinetic energy flux, and to occur mainly between 30-50 deg N. The nonlinear interactions were a negative contribution over the North Pacific at the 200 mb level.

On-Line Analysis and Kinetic Behavior of Arsenic Release during Coal Combustion and Pyrolysis.

PubMed

Shen, Fenghua; Liu, Jing; Zhang, Zhen; Dai, Jinxin

2015-11-17

The kinetic behavior of arsenic (As) release during coal combustion and pyrolysis in a fluidized bed was investigated by applying an on-line analysis system of trace elements in flue gas. This system, based on inductively coupled plasma optical emission spectroscopy (ICP-OES), was developed to measure trace elements concentrations in flue gas quantitatively and continuously. Obvious variations of arsenic concentration in flue gas were observed during coal combustion and pyrolysis, indicating strong influences of atmosphere and temperature on arsenic release behavior. Kinetic laws governing the arsenic release during coal combustion and pyrolysis were determined based on the results of instantaneous arsenic concentration in flue gas. A second-order kinetic law was determined for arsenic release during coal combustion, and the arsenic release during coal pyrolysis followed a fourth-order kinetic law. The results showed that the arsenic release rate during coal pyrolysis was faster than that during coal combustion. Thermodynamic calculations were carried out to identify the forms of arsenic in vapor and solid phases during coal combustion and pyrolysis, respectively. Ca3(AsO4)2 and Ca(AsO2)2 are the possible species resulting from As-Ca interaction during coal combustion. Ca(AsO2)2 is the most probable species during coal pyrolysis.

Integral Design Methodology of Photocatalytic Reactors for Air Pollution Remediation.

PubMed

Passalía, Claudio; Alfano, Orlando M; Brandi, Rodolfo J

2017-06-07

An integral reactor design methodology was developed to address the optimal design of photocatalytic wall reactors to be used in air pollution control. For a target pollutant to be eliminated from an air stream, the proposed methodology is initiated with a mechanistic derived reaction rate. The determination of intrinsic kinetic parameters is associated with the use of a simple geometry laboratory scale reactor, operation under kinetic control and a uniform incident radiation flux, which allows computing the local superficial rate of photon absorption. Thus, a simple model can describe the mass balance and a solution may be obtained. The kinetic parameters may be estimated by the combination of the mathematical model and the experimental results. The validated intrinsic kinetics obtained may be directly used in the scaling-up of any reactor configuration and size. The bench scale reactor may require the use of complex computational software to obtain the fields of velocity, radiation absorption and species concentration. The complete methodology was successfully applied to the elimination of airborne formaldehyde. The kinetic parameters were determined in a flat plate reactor, whilst a bench scale corrugated wall reactor was used to illustrate the scaling-up methodology. In addition, an optimal folding angle of the corrugated reactor was found using computational fluid dynamics tools.

Systems biology from micro-organisms to human metabolic diseases: the role of detailed kinetic models.

PubMed

Bakker, Barbara M; van Eunen, Karen; Jeneson, Jeroen A L; van Riel, Natal A W; Bruggeman, Frank J; Teusink, Bas

2010-10-01

Human metabolic diseases are typically network diseases. This holds not only for multifactorial diseases, such as metabolic syndrome or Type 2 diabetes, but even when a single gene defect is the primary cause, where the adaptive response of the entire network determines the severity of disease. The latter may differ between individuals carrying the same mutation. Understanding the adaptive responses of human metabolism naturally requires a systems biology approach. Modelling of metabolic pathways in micro-organisms and some mammalian tissues has yielded many insights, qualitative as well as quantitative, into their control and regulation. Yet, even for a well-known pathway such as glycolysis, precise predictions of metabolite dynamics from experimentally determined enzyme kinetics have been only moderately successful. In the present review, we compare kinetic models of glycolysis in three cell types (African trypanosomes, yeast and skeletal muscle), evaluate their predictive power and identify limitations in our understanding. Although each of these models has its own merits and shortcomings, they also share common features. For example, in each case independently measured enzyme kinetic parameters were used as input. Based on these 'lessons from glycolysis', we will discuss how to make best use of kinetic computer models to advance our understanding of human metabolic diseases.

The transport kinetics and selectivity of HpUreI, the urea channel from Helicobacter pylori†

PubMed Central

Gray, Lawrence R; Gu, Sean X; Quick, Matthias; Khademi, Shahram

2017-01-01

Helicobacter pylori’s unique ability to colonize and survive in the acidic environment of the stomach is critically dependent on uptake of urea through the urea channel, HpUreI. Hence, HpUreI may represent a promising target for the development of specific drugs against this human pathogen. To obtain insight into the structure/function relationship of this channel, we have developed conditions for the high-yield expression and purification of stable recombinant HpUreI that allowed its detailed kinetic characterization in solubilized form and reconstituted into liposomes. Detergent-solubilized HpUreI forms homo-trimer, as determined by chemical cross-linking. Urea dissociation kinetics of purified HpUreI were determined by means of the scintillation proximity assay (SPA), whereas urea efflux was measured in HpUreI-containing proteoliposomes using stopped-flow spectrometry to determine the kinetics and selectivity of the urea channel. The kinetic analyses revealed that urea conduction in HpUreI is pH sensitive and saturable with a half-saturation concentration (or K0.5) of ~163 mM. Binding of urea by HpUreI was increased at lower pH; however, the apparent affinity of urea binding (~150 mM) was not significantly pH dependent. The solute selectivity analysis indicated that HpUreI is highly selective for urea and hydroxyurea. Removing either amino group of urea molecules diminishes their permeability through HpUreI. Similar to urea conduction, water diffusion through HpUreI is pH-dependent with low water permeability at neutral pH. PMID:21877689

Evaluating rainfall kinetic energy - intensity relationships with observed disdrometric data

NASA Astrophysics Data System (ADS)

Angulo-Martinez, Marta; Begueria, Santiago; Latorre, Borja

2016-04-01

Rainfall kinetic energy is required for determining erosivity, the ability of rainfall to detach soil particles and initiate erosion. Its determination relay on the use of disdrometers, i.e. devices capable of measuring the drop size distribution and velocity of falling raindrops. In the absence of such devices, rainfall kinetic energy is usually estimated with empirical expressions relating rainfall energy and intensity. We evaluated the performance of 14 rainfall energy equations in estimating one-minute rainfall energy and event total energy, in comparison with observed data from 821 rainfall episodes (more than 100 thousand one-minute observations) by means of an optical disdrometer. In addition, two sources of bias when using such relationships were evaluated: i) the influence of using theoretical terminal raindrop fall velocities instead of measured values; and ii) the influence of time aggregation (rainfall intensity data every 5-, 10-, 15-, 30-, and 60-minutes). Empirical relationships did a relatively good job when complete events were considered (R2 > 0.82), but offered poorer results for within-event (one-minute resolution) variation. Also, systematic biases where large for many equations. When raindrop size distribution was known, estimating the terminal fall velocities by empirical laws produced good results even at fine time resolution. The influence of time aggregation was very high in the estimated kinetic energy, although linear scaling may allow empirical correction. This results stress the importance of considering all these effects when rainfall energy needs to be estimated from more standard precipitation records. , and recommends the use of disdrometer data to locally determine rainfall kinetic energy.

Characterization of 12 GnRH peptide agonists - a kinetic perspective.

PubMed

Nederpelt, Indira; Georgi, Victoria; Schiele, Felix; Nowak-Reppel, Katrin; Fernández-Montalván, Amaury E; IJzerman, Adriaan P; Heitman, Laura H

2016-01-01

Drug-target residence time is an important, yet often overlooked, parameter in drug discovery. Multiple studies have proposed an increased residence time to be beneficial for improved drug efficacy and/or longer duration of action. Currently, there are many drugs on the market targeting the gonadotropin-releasing hormone (GnRH) receptor for the treatment of hormone-dependent diseases. Surprisingly, the kinetic receptor-binding parameters of these analogues have not yet been reported. Therefore, this project focused on determining the receptor-binding kinetics of 12 GnRH peptide agonists, including many marketed drugs. A novel radioligand-binding competition association assay was developed and optimized for the human GnRH receptor with the use of a radiolabelled peptide agonist, [(125) I]-triptorelin. In addition to radioligand-binding studies, a homogeneous time-resolved FRET Tag-lite™ method was developed as an alternative assay for the same purpose. Two novel competition association assays were successfully developed and applied to determine the kinetic receptor-binding characteristics of 12 high-affinity GnRH peptide agonists. Results obtained from both methods were highly correlated. Interestingly, the binding kinetics of the peptide agonists were more divergent than their affinities with residence times ranging from 5.6 min (goserelin) to 125 min (deslorelin). Our research provides new insights by incorporating kinetic, next to equilibrium, binding parameters in current research and development that can potentially improve future drug discovery targeting the GnRH receptor. © 2015 The British Pharmacological Society.

Characterization of 12 GnRH peptide agonists – a kinetic perspective

PubMed Central

Nederpelt, Indira; Georgi, Victoria; Schiele, Felix; Nowak‐Reppel, Katrin; Fernández‐Montalván, Amaury E.; IJzerman, Adriaan P.

2015-01-01

Background and Purpose Drug‐target residence time is an important, yet often overlooked, parameter in drug discovery. Multiple studies have proposed an increased residence time to be beneficial for improved drug efficacy and/or longer duration of action. Currently, there are many drugs on the market targeting the gonadotropin‐releasing hormone (GnRH) receptor for the treatment of hormone‐dependent diseases. Surprisingly, the kinetic receptor‐binding parameters of these analogues have not yet been reported. Therefore, this project focused on determining the receptor‐binding kinetics of 12 GnRH peptide agonists, including many marketed drugs. Experimental Approach A novel radioligand‐binding competition association assay was developed and optimized for the human GnRH receptor with the use of a radiolabelled peptide agonist, [125I]‐triptorelin. In addition to radioligand‐binding studies, a homogeneous time‐resolved FRET Tag‐lite™ method was developed as an alternative assay for the same purpose. Key Results Two novel competition association assays were successfully developed and applied to determine the kinetic receptor‐binding characteristics of 12 high‐affinity GnRH peptide agonists. Results obtained from both methods were highly correlated. Interestingly, the binding kinetics of the peptide agonists were more divergent than their affinities with residence times ranging from 5.6 min (goserelin) to 125 min (deslorelin). Conclusions and Implications Our research provides new insights by incorporating kinetic, next to equilibrium, binding parameters in current research and development that can potentially improve future drug discovery targeting the GnRH receptor. PMID:26398856

Amyloglucosidase enzymatic reactivity inside lipid vesicles

PubMed Central

Li, Mian; Hanford, Michael J; Kim, Jin-Woo; Peeples, Tonya L

2007-01-01

Efficient functioning of enzymes inside liposomes would open new avenues for applications in biocatalysis and bioanalytical tools. In this study, the entrapment of amyloglucosidase (AMG) (EC 3.2.1.3) from Aspergillus niger into dipalmitoylphosphatidylcholine (DPPC) multilamellar vesicles (MLVs) and large unilamellar vesicles (LUVs) was investigated. Negative-stain, freeze-fracture, and cryo-transmission electron microscopy images verified vesicle formation in the presence of AMG. Vesicles with entrapped AMG were isolated from the solution by centrifugation, and vesicle lamellarity was identified using fluorescence laser confocal microscopy. The kinetics of starch hydrolysis by AMG was modeled for two different systems, free enzyme in aqueous solution and entrapped enzyme within vesicles in aqueous suspension. For the free enzyme system, intrinsic kinetics were described by a Michaelis-Menten kinetic model with product inhibition. The kinetic constants, Vmax and Km, were determined by initial velocity measurements, and Ki was obtained by fitting the model to experimental data of glucose concentration-time curves. Predicted concentration-time curves using these kinetic constants were in good agreement with experimental measurements. In the case of the vesicles, the time-dependence of product (glucose) formation was experimentally determined and simulated by considering the kinetic behavior of the enzyme and the permeation of substrate into the vesicle. Experimental results demonstrated that entrapped enzymes were much more stable than free enyzme. The entrapped enzyme could be recycled with retention of 60% activity after 3 cycles. These methodologies can be useful in evaluating other liposomal catalysis operations. PMID:18271982

Evaluation of the kinetic energy of the torso by magneto-inertial measurement unit during the sit-to-stand movement.

PubMed

Lepetit, Kevin; Ben Mansour, Khalil; Boudaoud, Sofiane; Kinugawa-Bourron, Kiyoka; Marin, Frédéric

2018-01-23

Sit-to-stand tests are used in geriatrics as a qualitative issue in order to evaluate motor control and stability. In terms of measured indicators, it is traditionally the duration of the task that is reported, however it appears that the use of the kinetic energy as a new quantitative criterion allows getting a better understanding of musculoskeletal deficits of elderly subjects. The aim of this study was to determine the feasibility to obtain the measure of kinetic energy using magneto-inertial measurement units (MIMU) during sit-to-stand movements at various paces. 26 healthy subjects contributed to this investigation. Measured results were compared to a marker-based motion capture using the correlation coefficient and the normalized root mean square error (nRMSE). nRMSE were below 10% and correlation coefficients were over 0.97. In addition, errors on the mean kinetic energy were also investigated using Bland-Altman 95% limits of agreement (0.63 J-0.77 J), RMSE (0.29 J-0.38 J) and correlation coefficient (0.96-0.98). The results obtained highlighted that the method based on MIMU data could be an alternative to optoelectronic data acquisition to assess the kinetic energy of the torso during the sit-to-stand test, suggesting this method as being a promising alternative to determine kinetic energy during the sit-to-stand movement. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fuzzy Performance between Surface Fitting and Energy Distribution in Turbulence Runner

PubMed Central

Liang, Zhongwei; Liu, Xiaochu; Ye, Bangyan; Brauwer, Richard Kars

2012-01-01

Because the application of surface fitting algorithms exerts a considerable fuzzy influence on the mathematical features of kinetic energy distribution, their relation mechanism in different external conditional parameters must be quantitatively analyzed. Through determining the kinetic energy value of each selected representative position coordinate point by calculating kinetic energy parameters, several typical algorithms of complicated surface fitting are applied for constructing microkinetic energy distribution surface models in the objective turbulence runner with those obtained kinetic energy values. On the base of calculating the newly proposed mathematical features, we construct fuzzy evaluation data sequence and present a new three-dimensional fuzzy quantitative evaluation method; then the value change tendencies of kinetic energy distribution surface features can be clearly quantified, and the fuzzy performance mechanism discipline between the performance results of surface fitting algorithms, the spatial features of turbulence kinetic energy distribution surface, and their respective environmental parameter conditions can be quantitatively analyzed in detail, which results in the acquirement of final conclusions concerning the inherent turbulence kinetic energy distribution performance mechanism and its mathematical relation. A further turbulence energy quantitative study can be ensured. PMID:23213287

Extracting surface diffusion coefficients from batch adsorption measurement data: application of the classic Langmuir kinetics model.

PubMed

Chu, Khim Hoong

2017-11-09

Surface diffusion coefficients may be estimated by fitting solutions of a diffusion model to batch kinetic data. For non-linear systems, a numerical solution of the diffusion model's governing equations is generally required. We report here the application of the classic Langmuir kinetics model to extract surface diffusion coefficients from batch kinetic data. The use of the Langmuir kinetics model in lieu of the conventional surface diffusion model allows derivation of an analytical expression. The parameter estimation procedure requires determining the Langmuir rate coefficient from which the pertinent surface diffusion coefficient is calculated. Surface diffusion coefficients within the 10 -9 to 10 -6  cm 2 /s range obtained by fitting the Langmuir kinetics model to experimental kinetic data taken from the literature are found to be consistent with the corresponding values obtained from the traditional surface diffusion model. The virtue of this simplified parameter estimation method is that it reduces the computational complexity as the analytical expression involves only an algebraic equation in closed form which is easily evaluated by spreadsheet computation.

The effects of kinetic structure and micrograph content on achievement in reading micrographs by college biology students

NASA Astrophysics Data System (ADS)

Johnson, Virginia Abbott; Lockard, J. David

The effects of kinetic structure and micrograph content on student achievement of reading micrograph skills were examined. The purpose of the study was to determine which form of kinetic structure, high or low, and/or micrograph content, unified or varied, was most effective and if there were any interactive effects. Randomly assigned to four treatment groups, 100 introductory college biology students attended three audiovisual presentations and practice sessions on reading light, transmission electron, and scanning electron micrographs. The micrograph skills test, administered at two points in time, assessed knowledge acquisition and retention. The test measured general concept skills and actual reading micrograph skills separately. All significant tests were considered with an = 0.05. High kinetic structure was found to be more effective than low kinetic structure in developing general concepts about micrographs. This finding supports Anderson's kinetic theory research. High kinetic structure instruction does not affect actual reading micrograph skills, but micrograph content does. Unified micrograph content practice sessions were more effective than varied micrograph content practice sessions. More attention should be given to the visual components of perceptual learning tasks.

Quantitative pharmacological analysis of antagonist binding kinetics at CRF1 receptors in vitro and in vivo

PubMed Central

Ramsey, Simeon J; Attkins, Neil J; Fish, Rebecca; van der Graaf, Piet H

2011-01-01

BACKGROUND AND PURPOSE A series of novel non-peptide corticotropin releasing factor type-1 receptor (CRF1) antagonists were found to display varying degrees of insurmountable and non-competitive behaviour in functional in vitro assays. We describe how we attempted to relate this behaviour to ligand receptor-binding kinetics in a quantitative manner and how this resulted in the development and implementation of an efficient pharmacological screening method based on principles described by Motulsky and Mahan. EXPERIMENTAL APPROACH A non-equilibrium binding kinetic assay was developed to determine the receptor binding kinetics of non-peptide CRF1 antagonists. Nonlinear, mixed-effects modelling was used to obtain estimates of the compounds association and dissociation rates. We present an integrated pharmacokinetic–pharmacodynamic (PKPD) approach, whereby the time course of in vivo CRF1 receptor binding of novel compounds can be predicted on the basis of in vitro assays. KEY RESULTS The non-competitive antagonist behaviour appeared to be correlated to the CRF1 receptor off-rate kinetics. The integrated PKPD model suggested that, at least in a qualitative manner, the in vitro assay can be used to triage and select compounds for further in vivo investigations. CONCLUSIONS AND IMPLICATIONS This study provides evidence for a link between ligand offset kinetics and insurmountable/non-competitive antagonism at the CRF1 receptor. The exact molecular pharmacological nature of this association remains to be determined. In addition, we have developed a quantitative framework to study and integrate in vitro and in vivo receptor binding kinetic behaviour of CRF1 receptor antagonists in an efficient manner in a drug discovery setting. PMID:21449919

CURRENT AND KINETIC HELICITY OF LONG-LIVED ACTIVITY COMPLEXES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komm, Rudolf; Gosain, Sanjay, E-mail: komm@nso.edu

2015-01-01

We study long-lived activity complexes and their current helicity at the solar surface and their kinetic helicity below the surface. The current helicity has been determined from synoptic vector magnetograms from the NSO/SOLIS facility, and the kinetic helicity of subsurface flows has been determined with ring-diagram analysis applied to full-disk Dopplergrams from NSO/GONG and SDO/HMI. Current and kinetic helicity of activity complexes follow the hemispheric helicity rule with mainly positive values (78%; 78%, respectively, with a 95% confidence level of 31%) in the southern hemisphere and negative ones (80%; 93%, respectively, with a 95% confidence level of 22% and 14%,more » respectively) in the northern hemisphere. The locations with the dominant sign of kinetic helicity derived from Global Oscillation Network Group (GONG) and SDO/HMI data are more organized than those of the secondary sign even if they are not part of an activity complex, while locations with the secondary sign are more fragmented. This is the case for both hemispheres even for the northern one where it is not as obvious visually due to the large amount of magnetic activity present as compared to the southern hemisphere. The current helicity shows a similar behavior. The dominant sign of current helicity is the same as that of kinetic helicity for the majority of the activity complexes (83% with a 95% confidence level of 15%). During the 24 Carrington rotations analyzed here, there is at least one longitude in each hemisphere where activity complexes occur repeatedly throughout the epoch. These ''active'' longitudes are identifiable as locations of strong current and kinetic helicity of the same sign.« less

The Kinematics and Kinetics of the Running Pattern of Two-, Four-, and Six-Year-Old Children.

ERIC Educational Resources Information Center

Fortney, Virginia L.

1983-01-01

The running patterns of two-, four-, and six-year-old children were analyzed to determine how age and sex differences affected selected kinematic and kinetic variables. Differences tended to involve displacement, velocity, and magnitude of force measures. Sex differences concerning the leg swing were noted. (Author/PP)

Kinetic Modeling of Polychlorinated Dibenzo-p-dioxin and Dibenzofuran Formation Based on Carbon Degradation Reactions

EPA Science Inventory

Combustion experiments in a laboratory-scale fixed bed reactor were performed to determine the role of temperature and time in PCDD/F formation allowing a global kinetic expression to be written for PCDD/F formation due to soot oxidation in fly ash deposits. Rate constants were c...

Employing Magnetic Levitation to Monitor Reaction Kinetics and Measure Activation Energy

ERIC Educational Resources Information Center

Benz, Lauren; Cesafsky, Karen E.; Le, Tran; Park, Aileen; Malicky, David

2012-01-01

This article describes a simple and inexpensive undergraduate-level kinetics experiment that uses magnetic levitation to monitor the progress and determine the activation energy of a condensation reaction on a polymeric solid support. The method employs a cuvette filled with a paramagnetic solution positioned between two strong magnets. The…

Direct dynamic kinetic analysis and computer simulation of growth of Clostridium perfringens in cooked turkey during cooling

USDA-ARS?s Scientific Manuscript database

This research applied a new one-step methodology to directly construct a tertiary model for describing the growth of C. perfringens in cooked turkey meat under dynamically cooling conditions. The kinetic parameters of the growth models were determined by numerical analysis and optimization using mu...

Photolysis of nonylphenol ethoxylates: the determination of the degradation kinetics and the intermediate products.

PubMed

Chen, Ling; Zhou, Hai-Yun; Deng, Qin-Ying

2007-06-01

The photolysis of nonylphenol ethoxylates with an average oligomers length of ten ethoxylate units (NPEO(10)) in aqueous solution under UV, as well as the influence of humic acid (HA) on the photolysis was studied. A 125W high-pressure mercury lamp was employed as the light source. The intermediate products from the photolysis were determined by LC-MS. The results indicated that NPEO(10) underwent direct photolysis upon exposed to UV. The degradation pathway was complex. Besides the generally proposed degradation pathway of ethylene oxide (EO) side chains shortening, the oxidation of alkyl chain and EO chain led to intermediates having both a carboxylated (as well as carbonylated) ethoxylate and alkyl chain of varying lengths. The hydrogenation of benzene ring was also detected. The kinetics data showed that the first order reaction kinetics could be well used to describe the kinetics of NPEO(10) degradation. In the presence of dissolved organic matter by HA addition, the performance of NPEO(10) photodegradation was reduced. The photolysis rate decreased with increased HA concentration.

Precise non-steady-state characterization of solid active materials with no preliminary mechanistic assumptions

DOE PAGES

Constales, Denis; Yablonsky, Gregory S.; Wang, Lucun; ...

2017-04-25

This paper presents a straightforward and user-friendly procedure for extracting a reactivity characterization of catalytic reactions on solid materials under non-steady-state conditions, particularly in temporal analysis of products (TAP) experiments. The kinetic parameters derived by this procedure can help with the development of detailed mechanistic understanding. The procedure consists of the following two major steps: 1) Three “Laplace reactivities” are first determined based on the moments of the exit flow pulse response data; 2) Depending on a select kinetic model, kinetic constants of elementary reaction steps can then be expressed as a function of reactivities and determined accordingly. In particular,more » we distinguish two calculation methods based on the availability and reliability of reactant and product data. The theoretical results are illustrated using a reverse example with given parameters as well as an experimental example of CO oxidation over a supported Au/SiO 2 catalyst. The procedure presented here provides an efficient tool for kinetic characterization of many complex chemical reactions.« less

Theoretical study of the gas-phase structures of sodiated and cesiated leucine and isoleucine: zwitterionic structure disfavored in kinetic method experiments.

PubMed

Rozman, Marko

2005-10-01

The most stable charge-solvated (CS) and zwitterionic (ZW) structures of sodiated and cesiated leucine and isoleucine were studied by density functional theory methods. According to the Boltzmann distribution in gas phase, both forms of LeuNa+ and IleNa+ exist, but in LeuCs+ and IleCs+, the ZW forms are dominant. Results for the sodiated compounds are consistent with the relationship found between decrease in relative stability of CS versus ZW form and aliphatic amino acid side chain length. The observed degeneracy in energy for IleNa+ conformers is at odds with kinetic method results. Additional calculations showed that kinetic method structural determinations for IleNa+ do not reflect relative order of populations in the lowest energy conformers. Since complexation of cationized amino acids into ion-bound dimers disfavors ZW structure by approximately 8 kJ mol(-1), it is suggested that for energy close conformers of sodium-cationized amino acids, the kinetic method may not be reliable for structural determinations. Copyright (c) 2005 John Wiley & Sons, Ltd.

Kinetics of Electrocatalytic Reactions from First-Principles: A Critical Comparison with the Ab Initio Thermodynamics Approach.

PubMed

Exner, Kai S; Over, Herbert

2017-05-16

Multielectron processes in electrochemistry require the stabilization of reaction intermediates (RI) at the electrode surface after every elementary reaction step. Accordingly, the bond strengths of these intermediates are important for assessing the catalytic performance of an electrode material. Current understanding of microscopic processes in modern electrocatalysis research is largely driven by theory, mostly based on ab initio thermodynamics considerations, where stable reaction intermediates at the electrode surface are identified, while the actual free energy barriers (or activation barriers) are ignored. This simple approach is popular in electrochemistry in that the researcher has a simple tool at hand in successfully searching for promising electrode materials. The ab initio TD approach allows for a rough but fast screening of the parameter space with low computational cost. However, ab initio thermodynamics is also frequently employed (often, even based on a single binding energy only) to comprehend on the activity and on the mechanism of an electrochemical reaction. The basic idea is that the activation barrier of an endergonic reaction step consists of a thermodynamic part and an additional kinetically determined barrier. Assuming that the activation barrier scales with thermodynamics (so-called Brønsted-Polanyi-Evans (BEP) relation) and the kinetic part of the barrier is small, ab initio thermodynamics may provide molecular insights into the electrochemical reaction kinetics. However, for many electrocatalytic reactions, these tacit assumptions are violated so that ab initio thermodynamics will lead to contradictions with both experimental data and ab initio kinetics. In this Account, we will discuss several electrochemical key reactions, including chlorine evolution (CER), oxygen evolution reaction (OER), and oxygen reduction (ORR), where ab initio kinetics data are available in order to critically compare the results with those derived from a simple ab initio thermodynamics treatment. We show that ab initio thermodynamics leads to erroneous conclusions about kinetic and mechanistic aspects for the CER over RuO 2 (110), while the kinetics of the OER over RuO 2 (110) and ORR over Pt(111) are reasonably well described. Microkinetics of an electrocatalyzed reaction is largely simplified by the quasi-equilibria of the RI preceding the rate-determining step (rds) with the reactants. Therefore, in ab initio kinetics the rate of an electrocatalyzed reaction is governed by the transition state (TS) with the highest free energy G rds # , defining also the rate-determining step (rds). Ab initio thermodynamics may be even more powerful, when using the highest free energy of an reaction intermediate G max (RI) rather than the highest free energy difference between consecutive reaction intermediates, ΔG loss , as a descriptor for the kinetics.

Limiting Energy Dissipation Induces Glassy Kinetics in Single-Cell High-Precision Responses.

PubMed

Das, Jayajit

2016-03-08

Single cells often generate precise responses by involving dissipative out-of-thermodynamic-equilibrium processes in signaling networks. The available free energy to fuel these processes could become limited depending on the metabolic state of an individual cell. How does limiting dissipation affect the kinetics of high-precision responses in single cells? I address this question in the context of a kinetic proofreading scheme used in a simple model of early-time T cell signaling. Using exact analytical calculations and numerical simulations, I show that limiting dissipation qualitatively changes the kinetics in single cells marked by emergence of slow kinetics, large cell-to-cell variations of copy numbers, temporally correlated stochastic events (dynamic facilitation), and ergodicity breaking. Thus, constraints in energy dissipation, in addition to negatively affecting ligand discrimination in T cells, can create a fundamental difficulty in determining single-cell kinetics from cell-population results. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Chloroperoxidase-catalyzed oxidation of 4,6-dimethyldibenzothiophene as dimer complexes: evidence for kinetic cooperativity.

PubMed

Torres, Eduardo; Aburto, Jorge

2005-05-15

A sigmoidal kinetic behavior of chloroperoxidase for the oxidation of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in water-miscible organic solvent is for the first time reported. Kinetics of 4,6-DMDBT oxidation showed a cooperative profile probably due to the capacity of chloroperoxidase to recognize a substrate dimer (pi-pi dimer) in its active site. Experimental evidence is given for dimer formation and its presence in the active site of chloroperoxidase. The kinetic data were adjusted for a binding site able to interact with either monomer or dimer substrates, producing a cooperative model describing a one-site binding of two related species. Determination of kinetics constants by iterative calculations of possible oxidation paths of 4,6-DMDBT suggests that kinetics oxidation of dimer substrate is preferred when compared to monomer oxidation. Steady-state fluorometry of substrate in the absence and presence of chloroperoxidase, described by the spectral center of mass, supports this last conclusion.

VO2 kinetics of constant-load exercise following bed-rest-induced deconditioning

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Goldwater, D. J.; Sandler, H.

1984-01-01

Previous studies have shown that the oxygen uptake kinetics during exercise and recovery may be changed by alterations in work intensity, prior exercise, muscle group involvement, ambient conditions, posture, disease state, and level of physical conditioning. However, the effects of detraining on oxygen uptake kinetics have not been determined. The present investigation has the objective to determine the effects of deconditioning following seven days of continuous head-down bed rest on changes in steady-state oxygen uptake, O2 deficit, and recovery oxygen uptake during the performance of constant-load exercise. The obtained results may provide support for previous proposals that submaximal oxygen uptake was significantly reduced following bed rest. The major finding was that bed-rest deconditioning resulted in a reduction of total O2 transport/utilization capacity during the transient phase of upright but not supine exercise.

Three dimensional fluid-kinetic model of a magnetically guided plasma jet

NASA Astrophysics Data System (ADS)

Ramos, Jesús J.; Merino, Mario; Ahedo, Eduardo

2018-06-01

A fluid-kinetic model of the collisionless plasma flow in a convergent-divergent magnetic nozzle is presented. The model combines the leading-order Vlasov equation and the fluid continuity and perpendicular momentum equation for magnetized electrons, and the fluid equations for cold ions, which must be solved iteratively to determine the self-consistent plasma response in a three-dimensional magnetic field. The kinetic electron solution identifies three electron populations and provides the plasma density and pressure tensor. The far downstream asymptotic behavior shows the anisotropic cooling of the electron populations. The fluid equations determine the electric potential and the fluid velocities. In the small ion-sound gyroradius case, the solution is constructed one magnetic line at a time. In the large ion-sound gyroradius case, ion detachment from magnetic lines makes the problem fully three-dimensional.

Effect of medium acidity on the thermodynamics and kinetics of the reaction of pyridoxal 5'-phosphate with isoniazid in an aqueous solution

NASA Astrophysics Data System (ADS)

Gamov, G. A.; Zavalishin, M. N.; Usacheva, T. R.; Sharnin, V. A.

2017-05-01

Thermodynamic characteristics of the formation of the Schiff base between isoniazid and pyridoxal 5'-phosphate in an aqueous solution at different pH values of a medium are determined by means of spectrophotometry and calorimetric titration. The process kinetics is studied spectrophotometrically, and the reaction rate constants for the formation of the imine at different acidities of a medium are determined. Biochemical aspects of the binding of pyridoxal 5'-phosphate into stable compounds are discussed.

Annealing kinetics of latent particle tracks in Durango apatite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afra, B.; Rodriguez, M. D.; Giulian, R.

2011-02-01

Using synchrotron small-angle x-ray scattering we determine the ''latent'' track morphology and the track annealing kinetics in the Durango apatite. The latter, measured during ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallization of the damaged material. The resolution of fractions of a nanometer with which the track radii are determined, as well as the nondestructive, artefact-free measurement methodology shown here, provides an effective means for in-depth studies of ion-track formation in natural minerals under a wide variety of geological conditions.

Annealing kinetics of latent particle tracks in Durango apatite

NASA Astrophysics Data System (ADS)

Afra, B.; Lang, M.; Rodriguez, M. D.; Zhang, J.; Giulian, R.; Kirby, N.; Ewing, R. C.; Trautmann, C.; Toulemonde, M.; Kluth, P.

2011-02-01

Using synchrotron small-angle x-ray scattering we determine the “latent” track morphology and the track annealing kinetics in the Durango apatite. The latter, measured during ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallization of the damaged material. The resolution of fractions of a nanometer with which the track radii are determined, as well as the nondestructive, artefact-free measurement methodology shown here, provides an effective means for in-depth studies of ion-track formation in natural minerals under a wide variety of geological conditions.

An investigation into the crystallization tendency/kinetics of amorphous active pharmaceutical ingredients: A case study with dipyridamole and cinnarizine.

PubMed

Baghel, Shrawan; Cathcart, Helen; Redington, Wynette; O'Reilly, Niall J

2016-07-01

Amorphous drug formulations have great potential to enhance solubility and thus bioavailability of BCS class II drugs. However, the higher free energy and molecular mobility of the amorphous form drive them towards the crystalline state which makes them unstable. Accurate determination of the crystallization tendency/kinetics is the key to the successful design and development of such systems. In this study, dipyridamole (DPM) and cinnarizine (CNZ) have been selected as model compounds. Thermodynamic fragility (mT) was measured from the heat capacity change at the glass transition temperature (Tg) whereas dynamic fragility (mD) was evaluated using methods based on extrapolation of configurational entropy to zero [Formula: see text] , and heating rate dependence of Tg [Formula: see text] . The mean relaxation time of amorphous drugs was calculated from the Vogel-Tammann-Fulcher (VTF) equation. Furthermore, the correlation between fragility and glass forming ability (GFA) of the model drugs has been established and the relevance of these parameters to crystallization of amorphous drugs is also assessed. Moreover, the crystallization kinetics of model drugs under isothermal conditions has been studied using Johnson-Mehl-Avrami (JMA) approach to determine the Avrami constant 'n' which provides an insight into the mechanism of crystallization. To further probe into the crystallization mechanism, the non-isothermal crystallization kinetics of model systems were also analysed by statistically fitting the crystallization data to 15 different kinetic models and the relevance of model-free kinetic approach has been established. The crystallization mechanism for DPM and CNZ at each extent of transformation has been predicted. The calculated fragility, glass forming ability (GFA) and crystallization kinetics are found to be in good correlation with the stability prediction of amorphous solid dispersions. Thus, this research work involves a multidisciplinary approach to establish fragility, GFA and crystallization kinetics as stability predictors for amorphous drug formulations. Copyright © 2016 Elsevier B.V. All rights reserved.

Aerobic Fitness Level Typical of Elite Athletes is not Associated With Even Faster VO2 Kinetics During Cycling Exercise

PubMed Central

Figueira, Tiago R.; Caputo, Fabrizio; Machado, Carlos E.P.; Denadai, Benedito S.

2008-01-01

The aim of this study was to address the question if the VO2 kinetics is further improved as the aerobic training status increases from trained to elite level athletes. Maximal oxygen uptake (VO2max), work-rate associated to VO2max (IVO2max) and VO2 kinetics of moderate (Mod) and maximal exercise (Max) were determined in fifty- five subjects. Then, they were assigned into three groups: low (LF), intermediate (IF) and high (HF) aerobic fitness level. In average, the VO2max of LF, IF and HF groups were, respectively, 36.0 ± 3.1, 51.1 ± 4.5 and 68.1 ± 3.9 ml·kg·min-1 (p ≤ 0.05 among each other). VO2 kinetics mean response time of both exercise intensities were significantly faster (p ≤ 0.05) in HF (Mod, 27.5 ± 5.5 s; Max, 32.6 ± 8.3 s) and IF (Mod, 25.0 ± 3.1 s; Max, 42.6 ± 10.4 s) when compared to LF (Mod, 35.7 ± 7.9 s; Max: 57.8 ± 17.8 s). We can conclude that VO2 kinetics is improved as the fitness level is increased from low to intermediate but not further improved as the aerobic fitness level increases from intermediate to high. Key points Currently, it is reasonable to believe that the rate-limiting step of VO2 kinetics depends on exercise intensity. The well known physiological adaptations induced by endurance training are likely the most extreme means to overcome rate-limiting steps determining VO2 kinetics across exercise intensities. However, exercise adaptation leading individuals to the high-end of aerobic fitness level range (VO2max > 65 ml.kg.min-1) is not able to further improve VO2 kinetics during both, moderate and maximal intensity exercise. PMID:24150145

A gas-liquid system for enzyme kinetic studies of volatile organic chemicals. Determination of enzyme kinetic constants and partition coefficients of trichloroethylene.

PubMed

Hwang, I Y; Reardon, K F; Tessari, J D; Yang, R S

1996-04-01

A gas-liquid system was developed for enzyme kinetic study with volatile organic chemicals (VOCs) by modification of the gas uptake method for the in vivo physiologically based pharmacokinetic experiment. This gas-liquid system, designed in our laboratory, is composed of: 1) a diffusion chamber for adjusting initial vapor concentration by mixing ambient air and the VOCs; 2) a condenser for maintaining the liquid level in the incubation chamber; 3) a stainless-steel metal bellows pump for recirculating vapor in this system; 4) a gas chromatograph equipped with an autosampler and a flame ionization detector; and 5) a computer for controlling automation and data processing. Trichloroethylene (TCE) was used as a model chemical, and enzyme kinetics were studied by measuring the depletion of TCE in the gas phase of the system. TCE-at initial concentrations of 56, 620, and 1240 ppm-was incubated with rat liver microsomes and a NADPH regenerating system in a 100-ml round-bottom flask. Based on parallel enzyme assays using p-nitrophenol as a substrate, cytochrome P450IIE1, activity remained stable up to 3 hr under the incubation conditions (37 degrees C and pH 7.4) whereas addition of glutathione into the incubation mixture did not affect TCE metabolism. Kinetic constants were analyzed using a two-compartment pharmacokinetic model and the computer software SimuSolv. Statistical optimization using the maximum-likelihood method produced apparent in vitro Vmax and KM values of 0.55 nmol/mg protein/min and 0.9 microM, respectively. In addition, this newly developed methodology has a number of advantages over those reported in the literature, including the potential utility of determining tissue partition coefficients of VOCs for physiologically based pharmacokinetic modeling. We conclude that this gas-liquid system is suitable for determination of kinetic constants near realistic environmental concentrations of VOCs including TCE.

Pore Fluid Extraction by Reactive Solitary Waves in 3-D

NASA Astrophysics Data System (ADS)

Omlin, Samuel; Malvoisin, Benjamin; Podladchikov, Yury Y.

2017-09-01

In the lower crust, viscous compaction is known to produce solitary porosity and fluid pressure waves. Metamorphic (de)volatilization reactions can also induce porosity changes in response to the propagating fluid pressure anomalies. Here we present results from high-resolution simulations using Graphic Processing Unit parallel processing with a model that includes both viscous (de)compaction and reaction-induced porosity changes. Reactive porosity waves propagate in a manner similar to viscous porosity waves, but through a different mechanism involving fluid release and trap in the solid by reaction. These waves self-generate from red noise or an ellipsoidal porosity anomaly with the same characteristic size and abandon their source region to propagate at constant velocity. Two waves traveling at different velocities pass through each other in a soliton-like fashion. Reactive porosity waves thus provide an additional mechanism for fluid extraction at shallow depths with implications for ore formation, diagenesis, metamorphic veins formation, and fluid extraction from subduction zones.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenstreet, S.; Gladman, B.; Ngo, H.

While computing an improved near-Earth object (NEO) steady-state orbital distribution model, we discovered in the numerical integrations the unexpected production of retrograde orbits for asteroids that had originally exited from the accepted main-belt source regions. Our model indicates that {approx}0.1% (a factor of two uncertainty) of the steady-state NEO population (perihelion q < 1.3 AU) is on retrograde orbits. These rare outcomes typically happen when asteroid orbits flip to a retrograde configuration while in the 3:1 mean-motion resonance with Jupiter and then live for {approx}0.001 to 100 Myr. The model predicts, given the estimated near-Earth asteroid (NEA) population, that amore » few retrograde 0.1-1 km NEAs should exist. Currently, there are two known MPC NEOs with asteroidal designations on retrograde orbits which we therefore claim could be escaped asteroids instead of devolatilized comets. This retrograde NEA population may also answer a long-standing question in the meteoritical literature regarding the origin of high-strength, high-velocity meteoroids on retrograde orbits.« less

FeO and H-2O and the homogeneous accretion of the earth

NASA Technical Reports Server (NTRS)

Lange, M. A.; Ahrens, T. J.

1983-01-01

Shock devolatilization recovery data for brunite (Mg(OH)2) shocked to 13 and 23 GPa are presented. These data combined with previous data for serpentine (Mg3Si2O5(OH)4) are used to constrain the minimum size terrestrial planet for which planetesimal infall will result in an impact generated water atmosphere. Assuming, in hydrous phyllosilicates, model calculations simulating the interaction of metallic iron with impact released free water on the surface of the accreting Earth were carried out. It is assumed that the reaction of water with iron in the presence of enstatite is the prime source of the terrestrial FeO component of silicates and oxides. Lower and upper bounds on the terrestrial FeO budget are based on mantle FeO content and possible incorporation of FeO in the outer core. We demonstrate that the iron water reaction would result in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed.

FeO and H2O and the homogeneous accretion of the earth

NASA Technical Reports Server (NTRS)

Lange, M. A.; Ahrens, T. J.

1984-01-01

Shock devolatilization recovery data for brunite (Mg(OH)2) shocked to 13 and 23 GPa are presented. These data combined with previous data for serpentine (Mg3Si2O5(OH)4) are used to constrain the minimum size terrestrial planet for which planetesimal infall will result in an impact generated water atmosphere. Assuming, in hydrous phyllosilicates, model calculations simulating the interaction of metallic iron with impact released free water on the surface of the accreting earth were carried out. It is assumed that the reaction of water with iron in the presence of enstatite is the prime source of the terrestrial FeO component of silicates and oxides. Lower and upper bounds on the terrestrial FeO budget are based on mantle FeO content and possible incorporation of FeO in the outer core. We demonstrate that the iron water reaction would resuit in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed.

Evolution of microstructure and elastic wave velocities in dehydrated gypsum samples

NASA Astrophysics Data System (ADS)

Milsch, Harald; Priegnitz, Mike

2012-12-01

We report on changes in P and S-wave velocities and rock microstructure induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air, at ambient pressure, and temperatures between 378 and 423 K. Dehydration did not proceed homogeneously but via a reaction front moving sample inwards separating an outer highly porous rim from the remaining gypsum which, above approximately 393 (±5) K, concurrently decomposed into hemihydrate. Overall porosity was observed to continuously increase with reaction progress from approximately 2% for fully hydrated samples to 30% for completely dehydrated ones. Concurrently, P and S-wave velocities linearly decreased with porosity from 5.2 and 2.7 km/s to 1.0 and 0.7 km/s, respectively. It is concluded that a linearized empirical Raymer-type model extended by a critical porosity term and based on the respective time dependent mineral and pore volumes reasonably replicates the P and S-wave data in relation to reaction progress and porosity.

Characteristics of oily sludge combustion in circulating fluidized beds.

PubMed

Zhou, Lingsheng; Jiang, Xiumin; Liu, Jianguo

2009-10-15

Incineration of oily sludge in circulating fluidized beds may be an effective way for its management in some cases. The objective of the present paper is to investigate combustion characteristics of oily sludge, which would be helpful and useful for the design and simulation of a circulating fluidized bed. Firstly, the pyrolysis and combustion of oily sludge were studied through some thermal analyses, which included the thermogravimetric (TG) analysis and the differential thermal analytical (DTA) analysis. It was found that the combustion of oily sludge might be the combustion of its pyrolysis products. Secondly, an experiment for measuring of main components of the volatile from oily sludge pyrolysis was carried out. Some mathematic correlations about the compositions of volatile from oily sludge devolatilization were achieved from the experimental results. Finally, the combustion characteristics of oily sludge was studied in a lab-scale circulating fluidized bed, which could obtain some information about the location of release and combustion of the volatiles.

Effect of drying conditions on drying kinetics and quality of aromatic Pandanus amaryllifolius leaves.

PubMed

Rayaguru, Kalpana; Routray, Winny

2010-12-01

Pandanus amaryllifolius is a plant with aromatic leaves, which impart the characteristic flavour of aromatic rice. The quality of aromatic Pandanus leaves dried at low temperature (35 °C) and low RH (27%) in a heat pump dryer was evaluated and compared with those obtained from hot air drying at 45 °C. Thin-layer drying kinetics has been studied for both the conditions. To determine the kinetic parameters, the drying data were fitted to various semi-theoretical models. The goodness of fit was determined using the coefficient of determination, reduced chi square, and root mean square error. Aroma, colour, and overall acceptability determination of fresh and dried leaves were made using sensory evaluation. Drying of leaves took place mainly under the falling-rate period. The Page equation was found to be best among the proposed models to describe the thin-layer drying of Pandanus leaves with higher coefficient of determination. The effective moisture diffusivity values were also determined. The effect of low RH was prominent during the initial drying when the product was moist. The effect of temperature was prominent in the later part of drying, which acted as a driving force for moisture diffusion and hence the total drying time was reduced. Retention of aromatic compound 2-acetyl-1-pyrroline content was more in low temperature dried samples with higher sensory scores.

Water sorption equilibria and kinetics of henna leaves

NASA Astrophysics Data System (ADS)

Sghaier, Khamsa; Peczalski, Roman; Bagane, Mohamed

2018-05-01

In this work, firstly the sorption isotherms of henna leaves were determined using a dynamic vapor sorption ( DVS) device at 3 temperatures (30, 40, 50 °C). The equilibrium data were well fitted by the GAB model. Secondly, drying kinetics were measured using a pilot convective dryer for 3 air temperatures (same as above), 3 velocities (0.5, 1, 1.42 m/s) and 4 relative humidities (20, 30, 35, 40%). The drying kinetic coefficients were identified by fitting the DVS and pilot dryer data by Lewis semi-empirical model. In order to compare the obtained kinetic parameters with literature, the water diffusivities were also identified by fitting the data by the simplified solution of fickian diffusion equation. The identified kinetic coefficient was mainly dependent on air temperature and velocity what proved that it represented rather the external transfer and not the internal one.

General theory of the multistage geminate reactions of the isolated pairs of reactants. II. Detailed balance and universal asymptotes of kinetics.

PubMed

Kipriyanov, Alexey A; Doktorov, Alexander B

2014-10-14

The analysis of general (matrix) kinetic equations for the mean survival probabilities of any of the species in a sample (or mean concentrations) has been made for a wide class of the multistage geminate reactions of the isolated pairs. These kinetic equations (obtained in the frame of the kinetic approach based on the concept of "effective" particles in Paper I) take into account various possible elementary reactions (stages of a multistage reaction) excluding monomolecular, but including physical and chemical processes of the change in internal quantum states carried out with the isolated pairs of reactants (or isolated reactants). The general basic principles of total and detailed balance have been established. The behavior of the reacting system has been considered on macroscopic time scales, and the universal long-term kinetics has been determined.

Kinetic Study on the Esterification of Palm Fatty Acid Distillate (PFAD) Using Heterogeneous Catalyst

NASA Astrophysics Data System (ADS)

Rofiqah, U.; Djalal, R. A.; Sutrisno, B.; Hidayat, A.

2018-05-01

Esterification with heterogeneous catalysts is believed to have advantages compared to homogeneous catalysts. Palm Fatty Acid Distillate (PFAD) was esterified by ZrO2 -SO4 2-/natural zeolite at temperature variation of 55°C, 60°C, and 65°C to produce biodiesel. Determination of reaction kinetics was done by experiment and modeling. Kinetic study was approached using pseudo-homogeneous model of first order. For experiment, reaction kinetics were 0.0031 s-1, 0.0054 s-1, and 0.00937 s-1 for a temperature of 55 °C, 60 °C and 65 °C, respectively. For modelling, reaction kinetics were 0.0030 s-1, 0.0055 s-1, and 0.0090 s-1 for a temperature of 55°C, 60°C and 65°C, respectively. Rate and conversion of reaction are getting increased by increasing temperature.

Kinetics from Replica Exchange Molecular Dynamics Simulations.

PubMed

Stelzl, Lukas S; Hummer, Gerhard

2017-08-08

Transitions between metastable states govern many fundamental processes in physics, chemistry and biology, from nucleation events in phase transitions to the folding of proteins. The free energy surfaces underlying these processes can be obtained from simulations using enhanced sampling methods. However, their altered dynamics makes kinetic and mechanistic information difficult or impossible to extract. Here, we show that, with replica exchange molecular dynamics (REMD), one can not only sample equilibrium properties but also extract kinetic information. For systems that strictly obey first-order kinetics, the procedure to extract rates is rigorous. For actual molecular systems whose long-time dynamics are captured by kinetic rate models, accurate rate coefficients can be determined from the statistics of the transitions between the metastable states at each replica temperature. We demonstrate the practical applicability of the procedure by constructing master equation (Markov state) models of peptide and RNA folding from REMD simulations.

Paralinear Oxidation of Silicon Nitride in a Water Vapor/Oxygen Environment

NASA Technical Reports Server (NTRS)

Fox, Dennis S.; Opila, Elizabeth J.; Nguyen, QuynhGiao; Humphrey, Donald L.; Lewton, Susan M.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Three silicon nitride materials were exposed to dry oxygen flowing at 0.44 cm/s at temperatures between 1200 and 1400 C. Reaction kinetics were measured with a continuously recording microbalance. Parabolic kinetics were observed. When the same materials were exposed to a 50% H2O - 50% O2 gas mixture flowing at 4.4 cm/s, all three types exhibited paralinear kinetics. The material is oxidized by water vapor to form solid silica. The protective silica is in turn volatilized by water vapor to form primarily gaseous Si(OH)4. Nonlinear least squares analysis and a paralinear kinetic model were used to determine both parabolic and linear rate constants from the kinetic data. Volatilization of the protective silica scale can result in accelerated consumption of Si3N4. Recession rates under conditions more representative of actual combustors are compared to the furnace data.

V̇O2 and HR kinetics before and after International Space Station missions.

PubMed

Hoffmann, U; Moore, A D; Koschate, J; Drescher, U

2016-03-01

Heart rate (HR), pulmonary and muscle oxygen uptake ([Formula: see text]O2pulm, [Formula: see text]O2musc) kinetics after changes of work rate (WR) indicate regulatory characteristics related to aerobic metabolism. We analysed whether the kinetics of HR, [Formula: see text]O2pulm and [Formula: see text]O2musc are slowed after missions to the International Space Station (ISS). The changes of the kinetics were correlated with [Formula: see text]O2peak data. 10 astronauts [4 females, 6 males, age: 48.0 ± 3.8 years, height: 176 ± 7 cm, mass: 74.5 ± 15.9 kg (mean ± SD)] performed an incremental test to determine [Formula: see text]O2peak (before missions on L-110 days, after return on R+1/+10/+36 days), and a cardio-respiratory kinetics test (CRKT) with randomized 30-80 W WR changes to determine HR, [Formula: see text]O2pulm and [Formula: see text]O2musc kinetics by time-series analysis (L-236/-73, R+6/+21). Kinetics were summarized by maximum and related lag of cross-correlation function (CCFmax, CCFlag) of WR with the analysed parameter. Statistically, significant changes were also found for CCFmax([Formula: see text]O2musc) between L-236 and R+6 (P = 0.010), L-236 and R+21 (P = 0.030), L-72 and R+6 (P = 0.043). Between pre-to-post mission change in [Formula: see text]O2peak and CCFmax(HR), a correlation was shown (r SP = 0.67, P = 0.017). The [Formula: see text]O2musc kinetics changes indicate aerobic detraining effects which are present up to 21 days following space flight. The correlations between changes in [Formula: see text]O2peak and HR kinetics illustrate the key role of cardiovascular regulation in [Formula: see text]O2peak. The addition of CRKT to ISS flight is recommended to obtain information regarding the potential muscular and cardiovascular deconditioning. This allows a reduction in the frequency of higher intensity testing during flight.

Stability-indicating LC assay for butenafine hydrochloride in creams using an experimental design for robustness evaluation and photodegradation kinetics study.

PubMed

Barth, Aline Bergesch; de Oliveira, Gabriela Bolfe; Malesuik, Marcelo Donadel; Paim, Clésio Soldatelli; Volpato, Nadia Maria

2011-08-01

A stability-indicating liquid chromatography method for the determination of the antifungal agent butenafine hydrochloride (BTF) in a cream was developed and validated using the Plackett-Burman experimental design for robustness evaluation. Also, the drug photodegradation kinetics was determined. The analytical column was operated with acetonitrile, methanol and a solution of triethylamine 0.3% adjusted to pH 4.0 (6:3:1) at a flow rate of 1 mL/min and detection at 283 nm. BTF extraction from the cream was done with n-butyl alcohol and methanol in ultrasonic bath. The performed degradation conditions were: acid and basic media with HCl 1M and NaOH 1M, respectively, oxidation with H(2)O(2) 10%, and the exposure to UV-C light. No interference in the BTF elution was verified. Linearity was assessed (r(2) = 0.9999) and ANOVA showed non-significative linearity deviation (p > 0.05). Adequate results were obtained for repeatability, intra-day precision, and accuracy. Critical factors were selected to examine the method robustness with the two-level Plackett-Burman experimental design and no significant factors were detected (p > 0.05). The BTF photodegradation kinetics was determined for the standard and for the cream, both in methanolic solution, under UV light at 254 nm. The degradation process can be described by first-order kinetics in both cases.

Quantitative in vivo receptor binding. III. Tracer kinetic modeling of muscarinic cholinergic receptor binding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frey, K.A.; Hichwa, R.D.; Ehrenkaufer, R.L.

1985-10-01

A tracer kinetic method is developed for the in vivo estimation of high-affinity radioligand binding to central nervous system receptors. Ligand is considered to exist in three brain pools corresponding to free, nonspecifically bound, and specifically bound tracer. These environments, in addition to that of intravascular tracer, are interrelated by a compartmental model of in vivo ligand distribution. A mathematical description of the model is derived, which allows determination of regional blood-brain barrier permeability, nonspecific binding, the rate of receptor-ligand association, and the rate of dissociation of bound ligand, from the time courses of arterial blood and tissue tracer concentrations.more » The term ''free receptor density'' is introduced to describe the receptor population measured by this method. The technique is applied to the in vivo determination of regional muscarinic acetylcholine receptors in the rat, with the use of (TH)scopolamine. Kinetic estimates of free muscarinic receptor density are in general agreement with binding capacities obtained from previous in vivo and in vitro equilibrium binding studies. In the striatum, however, kinetic estimates of free receptor density are less than those in the neocortex--a reversal of the rank ordering of these regions derived from equilibrium determinations. A simplified model is presented that is applicable to tracers that do not readily dissociate from specific binding sites during the experimental period.« less

One step sintering of homogenized bauxite raw material and kinetic study

NASA Astrophysics Data System (ADS)

Gao, Chang-he; Jiang, Peng; Li, Yong; Sun, Jia-lin; Zhang, Jun-jie; Yang, Huan-ying

2016-10-01

A one-step sintering process of bauxite raw material from direct mining was completed, and the kinetics of this process was analyzed thoroughly. The results show that the sintering kinetics of bauxite raw material exhibits the liquid-phase sintering behavior. A small portion of impurities existed in the raw material act as a liquid phase. After X-ray diffraction analyses, scanning electron microscopy observations, and kinetics calculations, sintering temperature and heating duration were determined as the two major factors contributing to the sintering process and densification of bauxite ore. An elevated heating temperature and longer duration favor the densification process. The major obstacle for the densification of bauxite material is attributed to the formation of the enclosed blowhole during liquid-phase sintering.

Minimal Model of Quantum Kinetic Clusters for the Energy-Transfer Network of a Light-Harvesting Protein Complex.

PubMed

Wu, Jianlan; Tang, Zhoufei; Gong, Zhihao; Cao, Jianshu; Mukamel, Shaul

2015-04-02

The energy absorbed in a light-harvesting protein complex is often transferred collectively through aggregated chromophore clusters. For population evolution of chromophores, the time-integrated effective rate matrix allows us to construct quantum kinetic clusters quantitatively and determine the reduced cluster-cluster transfer rates systematically, thus defining a minimal model of energy-transfer kinetics. For Fenna-Matthews-Olson (FMO) and light-havrvesting complex II (LCHII) monomers, quantum Markovian kinetics of clusters can accurately reproduce the overall energy-transfer process in the long-time scale. The dominant energy-transfer pathways are identified in the picture of aggregated clusters. The chromophores distributed extensively in various clusters can assist a fast and long-range energy transfer.

Practical Approaches to Protein Folding and Assembly

PubMed Central

Walters, Jad; Milam, Sara L.; Clark, A. Clay

2009-01-01

We describe here the use of several spectroscopies, such as fluorescence emission, circular dichroism, and differential quenching by acrylamide, in examining the equilibrium and kinetic folding of proteins. The first section regarding equilibrium techniques provides practical information for determining the conformational stability of a protein. In addition, several equilibrium-folding models are discussed, from two-state monomer to four-state homodimer, providing a comprehensive protocol for interpretation of folding curves. The second section focuses on the experimental design and interpretation of kinetic data, such as burst-phase analysis and exponential fits, used in elucidating kinetic folding pathways. In addition, simulation programs are used routinely to support folding models generated by kinetic experiments, and the fundamentals of simulations are covered. PMID:19289201

Removal of humic acid from aqueous solution using dual PMMA/PVDF composite nanofiber: kinetics study

NASA Astrophysics Data System (ADS)

Zulfikar, M. A.; Afrianingsih, I.; Bahri, A.; Nasir, M.; Alni, A.; Setiyanto, H.

2018-05-01

The removal of humic acid from aqueous solution using dual poly(methyl methacrylate)/polyvinyl difluoride composite nanofiber under the influence of concentration has been studied. The experiments were performed using humic acid (HA) as an adsorbate at concentration in the range of 50-200 mg/L. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to describe the kinetic data and the rate constants were evaluated. It was observed that the amount of humic acid removed decrease with increasing concentration. The kinetic study revealed that pseudo-second order model fitted well the kinetic data, while the external diffusion or boundary layer diffusion was the main rate determining step in the removal process.

Objectives and Capabilities of the Deep Space 2 (DS2) Evolved Water Experiment

NASA Astrophysics Data System (ADS)

Yen, A. S.; Murray, B.; Zent, A. P.

1999-09-01

The New Millennium Deep Space 2 (DS2) Mars Microprobes will impact the surface of Mars at a latitude of approximately 75 degrees South on December 3, 1999. The primary objective of this mission is to demonstrate penetrator technologies for future scientific applications. Nonetheless, measurements will be obtained with the goal of characterizing the atmospheric structure during entry as well as the penetrability, thermal conductivity, and water ice content of the polar layered terrains. In addition to demonstrating the ability to collect a subsurface sample, the evolved water experiment will test models of the south polar regions which indicate that water ice is stable at depths of 4 to 20 cm and greater [Paige and Keegan, 1994]. This prediction for the presence of ice is in contrast to atmospheric circulation models which suggest that water is irreversibly lost from southern latitudes and that the only extensive, permanent ice deposits are located in the northern hemisphere [Houben et al., 1997]. Furthermore, MOC images from the 1998 aerobraking phase suggest a rougher and perhaps more devolatilized surface than inferred from Viking and Mariner 9 data. Thus, the direct determination of the presence or absence of near-surface ice by the DS2 probes is important in the resolution of the fundamental questions about Mars regarding the global inventory of water and the climate history. In pursuit of these objectives, a 160 milliliter soil sample will be actively collected by a miniature drill and analyzed for water ice both thermally and spectroscopically. Specific capabilities and detection limits for the abundance of water ice will be presented at the meeting.

Carbon attrition during the circulating fluidized bed combustion of a packaging-derived fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mastellone, M.L.; Arena, U.

1999-05-01

Cylindrical pellets of a market-available packaging-derived fuel, obtained from a mono-material collection of polyethylene terephthalate (PET) bottles, were batchwise fed to a laboratory scale circulating fluidized bed (CFB) combustor. The apparatus, whose riser was 41 mm ID and 4 m high, was operated under both inert and oxidizing conditions to establish the relative importance of purely mechanical attrition and combustion-assisted attrition in generating carbon fines. Silica sand particles of two size distributions were used as inert materials. For each run, carbon load and carbon particle size distribution in the riser and rates of attrited carbon fines escaping the combustor weremore » determined as a function of time. A parallel investigation was carried out with a bubbling fluidized bed (BFB) combustor to point out peculiarities of attrition in CFB combustors. After devolatilization, PET pellets generated fragile aggregates of char and sand, which easily crumbled, leading to single particles, partially covered by a carbon-rich layer. The injected fixed carbon was therefore present in the bed in three phases: an A-phase, made of aggregates of sand and char, an S-phase, made of individual carbon-covered sand particles and an F-phase, made of carbon fines, abraded by the surfaces of the A- and S-phases. The effects of the size of inert material on the different forms under which fixed carbon was present in the bed and on the rate of escape of attrited carbon fines from the combustor were investigated. Features of carbon attrition in CFB and BFB combustors are discussed.« less

Non-Isothermic Chemical Kinetics in the Undergraduate Laboratory: Arrhenius Parameters from Experiments with Hyperbolic Temperature Variation.

ERIC Educational Resources Information Center

Salvador, F.; And Others

1984-01-01

Describes a method which adapts itself to the characteristics of the kinetics of a chemical reaction in solution, enabling students to determine the Arrhenius parameters with satisfactory accuracy by means of a single non-isothermic experiment. Both activation energy and the preexponential factor values can be obtained by the method. (JN)

UNDERSTANDING CHLORINE AND CHLORAMINE DECAY KINETICS IN OLD CAST IRON PIPES, 2. CONVERSION FROM CONVENTIONAL TREATMENT TO MICROFILTRATION IN A SMALL WATER SYSTEM

EPA Science Inventory

This insitu pipe loop study was designed to determine the disinfectant kinetics associated with very old unlined cast iron pipelines with both chlorine and chloramination residuals. An abandoned 90-year-old unlined cast iron pipeline about 2000 ft long was acclimated to conduct a...

KINETIC DISTRIBUTION MODEL OF EVAPORATION, BIOSORPTION AND BIODEGRADATION OF POLYCHLORINATED BIPHENYLS (PCBS) IN THE SUSPENSION OF PSEUDOMONAS STUTZERI. (R826652)

EPA Science Inventory

Abstract

Kinetics of distribution of PCBs in an active bacterial suspension of Pseudomonas stutzeri was studied by monitoring the evaporated amounts and the concentration remaining in the liquid medium with the biomass. To determine the biodegradation rate const...

Kinetic tetrazolium microtiter assay

NASA Technical Reports Server (NTRS)

Pierson, Duane L. (Inventor); Stowe, Raymond P. (Inventor); Koeing, David W. (Inventor)

1992-01-01

A method for conducting an in vitro cell assay using a tetrazolium indicator is disclosed. The indicator includes a nonionic detergent which solubilizes a tetrazolium reduction product in vitro and has low toxicity for the cells. The incubation of test cells in the presence of zolium bromide and octoxynol (TRITON X-100) permits kinetics of the cell metabolism to be determined.

Synthesis and Characterization of Liquid Crystalline Epoxy Resins

DTIC Science & Technology

2014-01-01

Temperature dependence of the four parameters in the Burgers model. ......... 81 Figure 4.7 Dependence of creep compliance on creep time at different...Kinetic parameters for LCERs. ......................................................................... 65 Table 3.4 Kinetic parameters for non-LCERs...curing in a high strength magnetic field. The orientation was quantified by an orientation parameter determined with two-dimensional X-ray diffraction

Detection of kinetic change points in piece-wise linear single molecule motion

NASA Astrophysics Data System (ADS)

Hill, Flynn R.; van Oijen, Antoine M.; Duderstadt, Karl E.

2018-03-01

Single-molecule approaches present a powerful way to obtain detailed kinetic information at the molecular level. However, the identification of small rate changes is often hindered by the considerable noise present in such single-molecule kinetic data. We present a general method to detect such kinetic change points in trajectories of motion of processive single molecules having Gaussian noise, with a minimum number of parameters and without the need of an assumed kinetic model beyond piece-wise linearity of motion. Kinetic change points are detected using a likelihood ratio test in which the probability of no change is compared to the probability of a change occurring, given the experimental noise. A predetermined confidence interval minimizes the occurrence of false detections. Applying the method recursively to all sub-regions of a single molecule trajectory ensures that all kinetic change points are located. The algorithm presented allows rigorous and quantitative determination of kinetic change points in noisy single molecule observations without the need for filtering or binning, which reduce temporal resolution and obscure dynamics. The statistical framework for the approach and implementation details are discussed. The detection power of the algorithm is assessed using simulations with both single kinetic changes and multiple kinetic changes that typically arise in observations of single-molecule DNA-replication reactions. Implementations of the algorithm are provided in ImageJ plugin format written in Java and in the Julia language for numeric computing, with accompanying Jupyter Notebooks to allow reproduction of the analysis presented here.

Cardiorespiratory Kinetics Determined by Pseudo-Random Binary Sequences - Comparisons between Walking and Cycling.

PubMed

Koschate, J; Drescher, U; Thieschäfer, L; Heine, O; Baum, K; Hoffmann, U

2016-12-01

This study aims to compare cardiorespiratory kinetics as a response to a standardised work rate protocol with pseudo-random binary sequences between cycling and walking in young healthy subjects. Muscular and pulmonary oxygen uptake (V̇O 2 ) kinetics as well as heart rate kinetics were expected to be similar for walking and cycling. Cardiac data and V̇O 2 of 23 healthy young subjects were measured in response to pseudo-random binary sequences. Kinetics were assessed applying time series analysis. Higher maxima of cross-correlation functions between work rate and the respective parameter indicate faster kinetics responses. Muscular V̇O 2 kinetics were estimated from heart rate and pulmonary V̇O 2 using a circulatory model. Muscular (walking vs. cycling [mean±SD in arbitrary units]: 0.40±0.08 vs. 0.41±0.08) and pulmonary V̇O 2 kinetics (0.35±0.06 vs. 0.35±0.06) were not different, although the time courses of the cross-correlation functions of pulmonary V̇O 2 showed unexpected biphasic responses. Heart rate kinetics (0.50±0.14 vs. 0.40±0.14; P=0.017) was faster for walking. Regarding the biphasic cross-correlation functions of pulmonary V̇O 2 during walking, the assessment of muscular V̇O 2 kinetics via pseudo-random binary sequences requires a circulatory model to account for cardio-dynamic distortions. Faster heart rate kinetics for walking should be considered by comparing results from cycle and treadmill ergometry. © Georg Thieme Verlag KG Stuttgart · New York.

Quantification of biodegradation for o-xylene and naphthalene using first order decay models, Michaelis-Menten kinetics and stable carbon isotopes.

PubMed

Blum, Philipp; Hunkeler, Daniel; Weede, Matthias; Beyer, Christof; Grathwohl, Peter; Morasch, Barbara

2009-04-01

At a former wood preservation plant severely contaminated with coal tar oil, in situ bulk attenuation and biodegradation rate constants for several monoaromatic (BTEX) and polyaromatic hydrocarbons (PAH) were determined using (1) classical first order decay models, (2) Michaelis-Menten degradation kinetics (MM), and (3) stable carbon isotopes, for o-xylene and naphthalene. The first order bulk attenuation rate constant for o-xylene was calculated to be 0.0025 d(-1) and a novel stable isotope-based first order model, which also accounted for the respective redox conditions, resulted in a slightly smaller biodegradation rate constant of 0.0019 d(-1). Based on MM-kinetics, the o-xylene concentration decreased with a maximum rate of k(max)=0.1 microg/L/d. The bulk attenuation rate constant of naphthalene retrieved from the classical first order decay model was 0.0038 d(-1). The stable isotope-based biodegradation rate constant of 0.0027 d(-1) was smaller in the reduced zone, while residual naphthalene in the oxic part of the plume further downgradient was degraded at a higher rate of 0.0038 d(-1). With MM-kinetics a maximum degradation rate of k(max)=12 microg/L/d was determined. Although best fits were obtained by MM-kinetics, we consider the carbon stable isotope-based approach more appropriate as it is specific for biodegradation (not overall attenuation) and at the same time accounts for the dominant electron-accepting process. For o-xylene a field based isotope enrichment factor epsilon(field) of -1.4 could be determined using the Rayleigh model, which closely matched values from laboratory studies of o-xylene degradation under sulfate-reducing conditions.

Kinetics and selectivity of 2-propanol conversion on oxidized anatase TiO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rekoske, J.E.; Barteau, M.A.

1997-01-01

The steady-state kinetics of 2-propanol decomposition on oxidized anatase TiO{sub 2} have been determined at temperatures ranging from 448 to 598 K and 2-propanol partial pressures from 8.9 to 102.7 Torr. The effects of the addition of O{sub 2} and water to the carrier gas were also investigated. The steady-state reaction results primarily in the formation of a dehydration product, propylene, and a dehydrogenation product, acetone, with small amounts of carbon oxides also being observed. Depending on the reaction conditions, the selectivity to either propylene or acetone can range between 5 and 95%. The rate of dehydrogenation increases dramatically withmore » the addition of both O{sub 2} and water, while the dehydration rate is unaffected by their presence. Accordingly, the kinetics of 2-propanol decomposition were investigated using both air and an inert carrier. Using air as the carrier gas, the dehydration and dehydrogenation reactions were determined to be approximately one-half order with respect to 2-propanol partial pressure. The activation energies determined for the two processes are substantially different, 68 kJ mol{sup -1} for dehydrogenation and 130 kJ mol{sup -1} for dehydration, as evidenced by the strong temperature dependence of the decomposition selectivity. Using an inert carrier, the reaction kinetics depend in a complex fashion on the conversion of 2-propanol. The dependence on conversion was found to arise from the influence of water on the dehydrogenation kinetics. The presence of water, whether produced by 2-propanol dehydration or added independently, was found to increase the rate of 2-propanol dehydrogenation. 48 refs., 9 figs., 6 tabs.« less

Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

USGS Publications Warehouse

Ni, Y.; Ma, Q.; Ellis, G.S.; Dai, J.; Katz, B.; Zhang, S.; Tang, Y.

2011-01-01

Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using ??D values in ethane from several basins in the world are in close agreement with similar predictions based on the ??13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that ??D values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that ??D values in ethane might be more suitable for modeling than comparable values in methane and propane. ?? 2011 Elsevier Ltd.

Kinetics of bacterial phospholipase C activity at micellar interfaces: effect of substrate aggregate microstructure and a model for the kinetic parameters.

PubMed

Singh, Jasmeet; Ranganathan, Radha; Hajdu, Joseph

2008-12-25

Activity at micellar interfaces of bacterial phospholipase C from Bacillus cereus on phospholipids solubilized in micelles was investigated with the goal of elucidating the role of the interface microstructure and developing further an existing kinetic model. Enzyme kinetics and physicochemical characterization of model substrate aggregates were combined, thus enabling the interpretation of kinetics in the context of the interface. Substrates were diacylphosphatidylcholine of different acyl chain lengths in the form of mixed micelles with dodecyldimethylammoniopropanesulfonate. An early kinetic model, reformulated to reflect the interfacial nature of the kinetics, was applied to the kinetic data. A better method of data treatment is proposed, use of which makes the presence of microstructure effects quite transparent. Models for enzyme-micelle binding and enzyme-lipid binding are developed, and expressions incorporating the microstructural properties are derived for the enzyme-micelle dissociation constant K(s) and the interface Michaelis-Menten constant, K(M). Use of these expressions in the interface kinetic model brings excellent agreement between the kinetic data and the model. Numerical values for the thermodynamic and kinetic parameters are determined. Enzyme-lipid binding is found to be an activated process with an acyl chain length dependent free energy of activation that decreases with micelle lipid molar fraction with a coefficient of about -15RT and correlates with the tightness of molecular packing in the substrate aggregate. Thus, the physical insight obtained includes a model for the kinetic parameters that shows that these parameters depend on the substrate concentration and acyl chain length of the lipid. Enzyme-micelle binding is indicated to be hydrophobic and solvent mediated with a dissociation constant of 1.2 mM.

Investigation of Coal-biomass Catalytic Gasification using Experiments, Reaction Kinetics and Computational Fluid Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Battaglia, Francine; Agblevor, Foster; Klein, Michael

A collaborative effort involving experiments, kinetic modeling, and computational fluid dynamics (CFD) was used to understand co-gasification of coal-biomass mixtures. The overall goal of the work was to determine the key reactive properties for coal-biomass mixed fuels. Sub-bituminous coal was mixed with biomass feedstocks to determine the fluidization and gasification characteristics of hybrid poplar wood, switchgrass and corn stover. It was found that corn stover and poplar wood were the best feedstocks to use with coal. The novel approach of this project was the use of a red mud catalyst to improve gasification and lower gasification temperatures. An important resultsmore » was the reduction of agglomeration of the biomass using the catalyst. An outcome of this work was the characterization of the chemical kinetics and reaction mechanisms of the co-gasification fuels, and the development of a set of models that can be integrated into other modeling environments. The multiphase flow code, MFIX, was used to simulate and predict the hydrodynamics and co-gasification, and results were validated with the experiments. The reaction kinetics modeling was used to develop a smaller set of reactions for tractable CFD calculations that represented the experiments. Finally, an efficient tool was developed, MCHARS, and coupled with MFIX to efficiently simulate the complex reaction kinetics.« less

Kinetic Temperature and Electron Density Measurement in an Inductively Coupled Plasma Torch using Degenerate Four-Wave Mixing

NASA Technical Reports Server (NTRS)

Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

2008-01-01

Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

Ozonation of hospital raw wastewaters for cytostatic compounds removal. Kinetic modelling and economic assessment of the process.

PubMed

Ferre-Aracil, J; Valcárcel, Y; Negreira, N; de Alda, M López; Barceló, D; Cardona, S C; Navarro-Laboulais, J

2016-06-15

The kinetics of the ozone consumption for the pretreatment of hospital wastewater has been analysed in order to determine the reaction rate coefficients between the ozone and the readily oxidisabled organic matter and cytostatic compounds. The wastewater from a medium size hospital was treated with ozone and peroxone methodologies, varying the ozone concentration, the reaction time and the hydrogen peroxide doses. The analysis shows that there are four cytostatic compounds, i.e. irinotecan, ifosfamide, cyclophosphamide and capecitabine, detected in the wastewaters and they are completely removed with reasonably short times after the ozone treatment. Considering the reactor geometry, the gas hydrodynamics, the mass transfer of ozone from gas to liquid and the reaction of all oxidisable compounds of the wastewater it is possible to determine the chemical ozone demand, COzD, of the sample as 256mgO3L(-1) and the kinetic rate coefficient with the dissolved organic matter as 8.4M(-1)s(-1). The kinetic rate coefficient between the ozone and the cyclophosphamide is in the order of 34.7M(-1)s(-1) and higher for the other cytostatics. The direct economic cost of the treatment was evaluated considering this reaction kinetics and it is below 0.3€/m(3) under given circumstances. Copyright © 2016 Elsevier B.V. All rights reserved.

Maintenance of supersaturation I: indomethacin crystal growth kinetic modeling using an online second-derivative ultraviolet spectroscopic method.

PubMed

Patel, Dhaval D; Joguparthi, Vijay; Wang, Zeren; Anderson, Bradley D

2011-07-01

Formulations that produce supersaturated solutions after their oral administration have received increased attention as a means to improve bioavailability of poorly water-soluble drugs. Although it is widely recognized that excipients can prolong supersaturation, the mechanisms by which these beneficial effects are realized are generally unknown. Difficulties in separately measuring the kinetics of nucleation and crystal growth have limited progress in understanding the mechanisms by which excipients contribute to the supersaturation maintenance. This paper describes the crystal growth kinetic modeling of indomethacin, a poorly water-soluble drug, from supersaturated aqueous suspensions using a newly developed, online second-derivative ultraviolet spectroscopic method. The apparent indomethacin equilibrium solubility after crystal growth at a high degree of supersaturation (S=6) was approximately 55% higher than the indomethacin equilibrium solubility determined prior to growth, which was attributed to the deposition of a higher energy indomethacin form on the seed crystals. The indomethacin crystal growth kinetics (S=6) was of first order. By comparing the mass transfer coefficients from indomethacin dissolution and crystal growth, it was shown that the indomethacin crystal growth kinetics at S=6 was bulk diffusion controlled. The change in indomethacin seed crystal size distribution before and after crystal growth was determined and modeled using a mass-balance relationship. Copyright © 2011 Wiley-Liss, Inc. and the American Pharmacists Association

The mechanical response of talin

NASA Astrophysics Data System (ADS)

Yao, Mingxi; Goult, Benjamin T.; Klapholz, Benjamin; Hu, Xian; Toseland, Christopher P.; Guo, Yingjian; Cong, Peiwen; Sheetz, Michael P.; Yan, Jie

2016-07-01

Talin, a force-bearing cytoplasmic adapter essential for integrin-mediated cell adhesion, links the actin cytoskeleton to integrin-based cell-extracellular matrix adhesions at the plasma membrane. Its C-terminal rod domain, which contains 13 helical bundles, plays important roles in mechanosensing during cell adhesion and spreading. However, how the structural stability and transition kinetics of the 13 helical bundles of talin are utilized in the diverse talin-dependent mechanosensing processes remains poorly understood. Here we report the force-dependent unfolding and refolding kinetics of all talin rod domains. Using experimentally determined kinetics parameters, we determined the dynamics of force fluctuation during stretching of talin under physiologically relevant pulling speeds and experimentally measured extension fluctuation trajectories. Our results reveal that force-dependent stochastic unfolding and refolding of talin rod domains make talin a very effective force buffer that sets a physiological force range of only a few pNs in the talin-mediated force transmission pathway.

Visible-Light Initiated Free-Radical/Cationic Ring-Opening Hybrid Photopolymerization of Methacrylate/Epoxy: Polymerization Kinetics, Crosslinking Structure, and Dynamic Mechanical Properties.

PubMed

Ge, Xueping; Ye, Qiang; Song, Linyong; Misra, Anil; Spencer, Paulette

2015-04-01

The effects of polymerization kinetics and chemical miscibility on the crosslinking structure and mechanical properties of polymers cured by visible-light initiated free-radical/cationic ring-opening hybrid photopolymerization are determined. A three-component initiator system is used and the monomer system contains methacrylates and epoxides. The photopolymerization kinetics is monitored in situ by Fourier transform infrared-attenuated total reflectance. The crosslinking structure is studied by modulated differential scanning calorimetry and dynamic mechanical analysis. X-ray microcomputed tomography is used to evaluate microphase separation. The mechanical properties of polymers formed by hybrid formed by free-radical polymerization. These investigations mark the first time that the benefits of the chain transfer reaction between epoxy and hydroxyl groups of methacrylate, on the crosslinking network and microphase separation during hybrid visible-light initiated photopolymerization, have been determined.

Light-Curing Volumetric Shrinkage in Dimethacrylate-Based Dental Composites by Nanoindentation and PAL Study.

PubMed

Shpotyuk, Olha; Adamiak, Stanislaw; Bezvushko, Elvira; Cebulski, Jozef; Iskiv, Maryana; Shpotyuk, Oleh; Balitska, Valentina

2017-12-01

Light-curing volumetric shrinkage in dimethacrylate-based dental resin composites Dipol® is examined through comprehensive kinetics research employing nanoindentation measurements and nanoscale atomic-deficient study with lifetime spectroscopy of annihilating positrons. Photopolymerization kinetics determined through nanoindentation testing is shown to be described via single-exponential relaxation function with character time constants reaching respectively 15.0 and 18.7 s for nanohardness and elastic modulus. Atomic-deficient characteristics of composites are extracted from positron lifetime spectra parameterized employing unconstrained x3-term fitting. The tested photopolymerization kinetics can be adequately reflected in time-dependent changes observed in average positron lifetime (with 17.9 s time constant) and fractional free volume of positronium traps (with 18.6 s time constant). This correlation proves that fragmentation of free-volume positronium-trapping sites accompanied by partial positronium-to-positron traps conversion determines the light-curing volumetric shrinkage in the studied composites.

Description of jambolan (Syzygium cumini (L.)) anthocyanin extraction kinetics at different stirring frequencies of the medium using diffusion models

NASA Astrophysics Data System (ADS)

da Silva, Wilton Pereira; Nunes, Jarderlany Sousa; Gomes, Josivanda Palmeira; de Araújo, Auryclennedy Calou; e Silva, Cleide M. D. P. S.

2018-05-01

Anthocyanin extraction kinetics was described for jambolan fruits. The spherical granules obtained were dried at 40 °C and the average radius of the sphere equivalent to the granules was determined. Solid-solvent ratio was fixed at 1:20 and temperature at 35 °C. A mixture of ethyl alcohol and hydrochloric acid (85:15) was used as solvent. Experiments were conducted with the following stirring frequencies: 0, 50, 100 and 150 rpm. Two diffusion models were used to describe the extraction process. The first one used an analytical solution, with boundary condition of the first kind. The second one used a numerical solution, with boundary condition of the third kind. The second model was the most adequate, and its results were used to determine empirical equations relating the process parameters with the stirring frequency, allowing to simulate new extraction kinetics.

Adaptive characterization of recrystallization kinetics in IF steel by electron backscatter diffraction.

PubMed

Kim, Dong-Kyu; Park, Won-Woong; Lee, Ho Won; Kang, Seong-Hoon; Im, Yong-Taek

2013-12-01

In this study, a rigorous methodology for quantifying recrystallization kinetics by electron backscatter diffraction is proposed in order to reduce errors associated with the operator's skill. An adaptive criterion to determine adjustable grain orientation spread depending on the recrystallization stage is proposed to better identify the recrystallized grains in the partially recrystallized microstructure. The proposed method was applied in characterizing the microstructure evolution during annealing of interstitial-free steel cold rolled to low and high true strain levels of 0.7 and 1.6, respectively. The recrystallization kinetics determined by the proposed method was found to be consistent with the standard method of Vickers microhardness. The application of the proposed method to the overall recrystallization stages showed that it can be used for the rigorous characterization of progressive microstructure evolution, especially for the severely deformed material. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Fluxgate magnetorelaxometry for characterization of hydrogel polymerization kinetics and physical entrapment capacity.

PubMed

Heim, E; Harling, S; Ludwig, F; Menzel, H; Schilling, M

2008-05-21

Hydrogels have the potential for providing drug delivery systems with long release rates. The polymerization kinetics and the physical entrapment capacity of photo-cross-linked hydroxyethyl methacrylate hydroxyethylstarch hydrogels are investigated with a non-destructive method. For this purpose, superparamagnetic nanoparticles as replacements for biomolecules are used as probes. By analyzing their magnetic relaxation behavior, the amounts of physically entrapped and mobile nanoparticles can be determined. The hydrogels were loaded with five different concentrations of nanoparticles. Different methods of analysis of the relaxation curves and the influence of the microviscosity are discussed. This investigation allows one to optimize the UV light irradiation time and to determine the amount of physically entrapped nanoparticles in the hydrogel network. It was found that the polymerization kinetics is faster for decreasing nanoparticle concentration but not all nanoparticles can be physically entrapped in the network.

Processing of extraterrestrial materials by high temperature vacuum vaporization

NASA Technical Reports Server (NTRS)

Grimley, R. T.; Lipschutz, M. E.

1983-01-01

It is noted that problems associated with the extraction and concentration of elements and commpounds important for the construction and operation of space habitats have received little attention. High temperature vacuum vaporization is considered a promising approach; this is a technique for which the space environment offers advantages in the form of low ambient pressures and temperatures and the possibility of sustained high temperatures via solar thermal energy. To establish and refine this new technology, experimental determinations must be made of the material release profiles as a function of temperature, of the release kinetics and chemical forms of material being transported, and of the various means of altering release kinetics. Trace element data determined by neutron activation analysis of meteorites heated to 1400 C in vacuum is summarized. The principal tool, high temperature spectrometry, is used to examine the vaporization thermodynamics and kinetics of major and minor elements from complex multicomponent extraterrestrial materials.

Upper limb joint kinetic analysis during tennis serve: Assessment of competitive level on efficiency and injury risks.

PubMed

Martin, C; Bideau, B; Ropars, M; Delamarche, P; Kulpa, R

2014-08-01

The aim of this work was to compare the joint kinetics and stroke production efficiency for the shoulder, elbow, and wrist during the serve between professionals and advanced tennis players and to discuss their potential relationship with given overuse injuries. Eleven professional and seven advanced tennis players were studied with an optoelectronic motion analysis system while performing serves. Normalized peak kinetic values of the shoulder, elbow, and wrist joints were calculated using inverse dynamics. To measure serve efficiency, all normalized peak kinetic values were divided by ball velocity. t-tests were used to determine significant differences between the resultant joint kinetics and efficiency values in both groups (advanced vs professional). Shoulder inferior force, shoulder anterior force, shoulder horizontal abduction torque, and elbow medial force were significantly higher in advanced players. Professional players were more efficient than advanced players, as they maximize ball velocity with lower joint kinetics. Since advanced players are subjected to higher joint kinetics, the results suggest that they appeared more susceptible to high risk of shoulder and elbow injuries than professionals, especially during the cocking and deceleration phases of the serve. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Chiral anomaly, Berry phase, and chiral kinetic theory from worldlines in quantum field theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Niklas; Venugopalan, Raju

Here, we outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry’s phase is obtained in a consistent non-relativistic adiabatic limit. The chiral anomaly, in contrast, arises from the phase of the fermion determinant; its topological properties are therefore distinct from those of the Berry phase.more » We show that the imaginary contribution to the fermion determinant too can be expressed as a point particle world-line path integral and derive the corresponding anomalous axial vector current. Our results can be used to derive a covariant relativistic chiral kinetic theory including the effects of topological fluctuations that has overlap with classical-statistical simulations of the CME at early times and anomalous hydrodynamics at late times.« less

Phase-plane analysis of the totally asymmetric simple exclusion process with binding kinetics and switching between antiparallel lanes

PubMed Central

Kuan, Hui-Shun; Betterton, Meredith D.

2016-01-01

Motor protein motion on biopolymers can be described by models related to the totally asymmetric simple exclusion process (TASEP). Inspired by experiments on the motion of kinesin-4 motors on antiparallel microtubule overlaps, we analyze a model incorporating the TASEP on two antiparallel lanes with binding kinetics and lane switching. We determine the steady-state motor density profiles using phase-plane analysis of the steady-state mean field equations and kinetic Monte Carlo simulations. We focus on the density-density phase plane, where we find an analytic solution to the mean field model. By studying the phase-space flows, we determine the model’s fixed points and their changes with parameters. Phases previously identified for the single-lane model occur for low switching rate between lanes. We predict a multiple coexistence phase due to additional fixed points that appear as the switching rate increases: switching moves motors from the higher-density to the lower-density lane, causing local jamming and creating multiple domain walls. We determine the phase diagram of the model for both symmetric and general boundary conditions. PMID:27627345

Chiral anomaly, Berry phase, and chiral kinetic theory from worldlines in quantum field theory

DOE PAGES

Mueller, Niklas; Venugopalan, Raju

2018-03-21

Here, we outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry’s phase is obtained in a consistent non-relativistic adiabatic limit. The chiral anomaly, in contrast, arises from the phase of the fermion determinant; its topological properties are therefore distinct from those of the Berry phase.more » We show that the imaginary contribution to the fermion determinant too can be expressed as a point particle world-line path integral and derive the corresponding anomalous axial vector current. Our results can be used to derive a covariant relativistic chiral kinetic theory including the effects of topological fluctuations that has overlap with classical-statistical simulations of the CME at early times and anomalous hydrodynamics at late times.« less

Study on Kinetic Mechanism of Bastnaesite Concentrates Decomposition Using Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Cen, Peng; Wu, Wenyuan; Bian, Xue

2018-06-01

The thermal decomposition of bastnaesite concentrates using calcium hydroxide was studied. Calcium hydroxide can effectively inhibit the emission of fluorine during roasting by transforming it to calcium fluoride. The decomposition rate increased with increasing reaction temperature and amount of calcium hydroxide. The decomposition kinetics were investigated. The decomposition reaction was determined to be a heterogeneous gas-solid reaction, and it followed an unreacted shrinking core model. By means of the integrated rate equation method, the reaction was proven to be kinetically first order. Different reaction models were fit to the experimental data to determine the reaction control process. The chemical reaction at the phase interface controlled the reaction rate in the temperatures ranging from 673 K to 773 K (400 °C to 500 °C) with an apparent activation energy of 82.044 kJ·mol-1. From 773 K to 973 K (500 °C to 700 °C), diffusion through the solid product's layer became the determining step, with a lower activation energy of 15.841 kJ·mol-1.

Fluid-related inclusions in Alpine high-pressure peridotite reveal trace element recycling during subduction-zone dehydration of serpentinized mantle (Cima di Gagnone, Swiss Alps)

NASA Astrophysics Data System (ADS)

Scambelluri, Marco; Pettke, Thomas; Cannaò, Enrico

2015-11-01

Serpentinites release at sub-arc depths volatiles and several fluid-mobile trace elements found in arc magmas. Constraining element uptake in these rocks and defining the trace element composition of fluids released upon serpentinite dehydration can improve our understanding of mass transfer across subduction zones and to volcanic arcs. The eclogite-facies garnet metaperidotite and chlorite harzburgite bodies embedded in paragneiss of the subduction melange from Cima di Gagnone derive from serpentinized peridotite protoliths and are unique examples of ultramafic rocks that experienced subduction metasomatism and devolatilization. In these rocks, metamorphic olivine and garnet trap polyphase inclusions representing the fluid released during high-pressure breakdown of antigorite and chlorite. Combining major element mapping and laser-ablation ICP-MS bulk inclusion analysis, we characterize the mineral content of polyphase inclusions and quantify the fluid composition. Silicates, Cl-bearing phases, sulphides, carbonates, and oxides document post-entrapment mineral growth in the inclusions starting immediately after fluid entrapment. Compositional data reveal the presence of two different fluid types. The first (type A) records a fluid prominently enriched in fluid-mobile elements, with Cl, Cs, Pb, As, Sb concentrations up to 103 PM (primitive mantle), ∼102 PM Tl, Ba, while Rb, B, Sr, Li, U concentrations are of the order of 101 PM, and alkalis are ∼2 PM. The second fluid (type B) has considerably lower fluid-mobile element enrichments, but its enrichment patterns are comparable to type A fluid. Our data reveal multistage fluid uptake in these peridotite bodies, including selective element enrichment during seafloor alteration, followed by fluid-rock interaction along with subduction metamorphism in the plate interface melange. Here, infiltration of sediment-equilibrated fluid produced significant enrichment of the serpentinites in As, Sb, B, Pb, an enriched trace element pattern that was then transferred to the fluid released at greater depth upon serpentine dehydration (type A fluid). The type B fluid hosted by garnet may record the composition of the chlorite breakdown fluid released at even greater depth. The Gagnone study-case demonstrates that serpentinized peridotites acquire water and fluid-mobile elements during ocean floor hydration and through exchange with sediment-equilibrated fluids in the early subduction stages. Subsequent antigorite devolatilization at subarc depths delivers aqueous fluids to the mantle wedge that can be prominently enriched in sediment-derived components, potentially triggering arc magmatism without the need of concomitant dehydration/melting of metasediments or altered oceanic crust.

Fluidized bed combustion of pelletized biomass and waste-derived fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chirone, R.; Scala, F.; Solimene, R.

2008-10-15

The fluidized bed combustion of three pelletized biogenic fuels (sewage sludge, wood, and straw) has been investigated with a combination of experimental techniques. The fuels have been characterized from the standpoints of patterns and rates of fuel devolatilization and char burnout, extent of attrition and fragmentation, and their relevance to the fuel particle size distribution and the amount and size distribution of primary ash particles. Results highlight differences and similarities among the three fuels tested. The fuels were all characterized by limited primary fragmentation and relatively long devolatilization times, as compared with the time scale of particle dispersion away frommore » the fuel feeding ports in practical FBC. Both features are favorable to effective lateral distribution of volatile matter across the combustor cross section. The three fuels exhibited distinctively different char conversion patterns. The high-ash pelletized sludge burned according to the shrinking core conversion pattern with negligible occurrence of secondary fragmentation. The low-ash pelletized wood burned according to the shrinking particle conversion pattern with extensive occurrence of secondary fragmentation. The medium-ash pelletized straw yielded char particles with a hollow structure, resembling big cenospheres, characterized by a coherent inorganic outer layer strong enough to prevent particle fragmentation. Inert bed particles were permanently attached to the hollow pellets as they were incorporated into ash melts. Carbon elutriation rates were very small for all the fuels tested. For pelletized sludge and straw, this was mostly due to the shielding effect of the coherent ash skeleton. For the wood pellet, carbon attrition was extensive, but was largely counterbalanced by effective afterburning due to the large intrinsic reactivity of attrited char fines. The impact of carbon attrition on combustion efficiency was negligible for all the fuels tested. The size distribution of primary ash particles liberated upon complete carbon burnoff largely reflected the combustion pattern of each fuel. Primary ash particles of size nearly equal to that of the parent fuel were generated upon complete burnoff of the pelletized sludge. Nonetheless, secondary attrition of primary ash from pelletized sludge is large, to the point where generation of fine ash would be extensive over the typical residence time of bed ash in fluidized bed combustors. Very few and relatively fine primary ash particles were released after complete burnoff of wood pellets. Primary ash particles remaining after complete burnoff of pelletized straw had sizes and shapes that were largely controlled by the occurrence of ash agglomeration phenomena. (author)« less

Volatile (Li, B, F and Cl) mobility during amphibole breakdown in subduction zones

NASA Astrophysics Data System (ADS)

Debret, Baptiste; Koga, Kenneth T.; Cattani, Fanny; Nicollet, Christian; Van den Bleeken, Greg; Schwartz, Stephane

2016-02-01

Amphiboles are ubiquitous minerals in the altered oceanic crust. During subduction, their breakdown is governed by continuous reactions up to eclogitic facies conditions. Amphiboles thus contribute to slab-derived fluid throughout prograde metamorphism and continuously record information about volatile exchanges occurring between the slab and the mantle wedge. However, the fate of volatile elements and especially halogens, such as F and Cl, in amphibole during subduction is poorly constrained. We studied metagabbros from three different localities in the Western Alps: the Chenaillet ophiolite, the Queyras Schistes Lustrés and the Monviso meta-ophiolitic complexes. These samples record different metamorphic conditions, from greenschist to eclogite facies, and have interacted with different lithologies (e.g. sedimentary rocks, serpentinites) from their formation at mid-oceanic ridge, up to their devolatilization during subduction. In the oceanic crust, the initial halogen budget is mostly stored in magmatic amphibole (F = 300-7000 ppm; Cl = 20-1200 ppm) or in amphibole corona (F = 100-7000 ppm; Cl = 80-2000 ppm) and titanite (F = 200-1500 ppm; Cl < 200 ppm) formed during hydrothermal seafloor alteration. It is thus the fate of these phases that govern the halogen fluxes between the crust and the overlying mantle and/or the plate interface in subduction zones. Li and B are poorly stored in the oceanic crust (< 5 ppm). In subduction zones, prograde metamorphism of metagabbros is first marked by the crystallization of glaucophane at the expense of magmatic and amphibole coronas. This episode is accompanied with a decrease of halogen concentrations in amphiboles (< 200 ppm of F and Cl) suggesting that these elements can be transferred to the mantle wedge by fluids. In the Queyras Schistes Lustrés complex, the intense deformation and the abundant devolatilization of metasedimentary rocks produce large fluid flows that promote rock chemical hybridization (metasomatic mixing with hybrid composition between metasedimentary rock and metagabbro) at the metasedimentary rock/metagabbro contacts. Such fluid/rock interactions result in a strong addition of Li in glaucophane (up to 600 ppm) whereas halogen concentrations are unaffected. At eclogite facies conditions, metagabbros display low halogens concentrations (< 20 ppm of F and < 100 ppm of Cl) relative to altered oceanic crust (F = 40-650 ppm; Cl = 40-1400 ppm) suggesting that these elements are continuously released by fluids during the first 30-80 km of subduction whatever the tectonic environment (e.g. slab, plate interface) and the considered fluid/rock interactions.

Kinetics of Adsorption of Diethylene-triaminomethylated Polyacrylamide on Dispersed Kaolin Accompanied by Flocculation.

PubMed

Kislenko; Verlinskaya

1999-08-01

The kinetics of the adsorption of diethylene-triaminomethylated polyacrylamide on kaolin dispersed in water has been investigated. An influence of the flocculation of kaolin dispersion on polymer adsorption has been found. The kinetics of particle aggregation under the influence of dissolved polymer has been studied. Polymer adsorption and particle aggregation proceed simultaneously, accompanied by a steady decrease in the amount of adsorbed polymer per unit mass of kaolin. A mathematical model of the adsorption process, consistent with the experimental data, is described. The rate constants and their ratios have been determined. Copyright 1999 Academic Press.

Program Helps To Determine Chemical-Reaction Mechanisms

NASA Technical Reports Server (NTRS)

Bittker, D. A.; Radhakrishnan, K.

1995-01-01

General Chemical Kinetics and Sensitivity Analysis (LSENS) computer code developed for use in solving complex, homogeneous, gas-phase, chemical-kinetics problems. Provides for efficient and accurate chemical-kinetics computations and provides for sensitivity analysis for variety of problems, including problems involving honisothermal conditions. Incorporates mathematical models for static system, steady one-dimensional inviscid flow, reaction behind incident shock wave (with boundary-layer correction), and perfectly stirred reactor. Computations of equilibrium properties performed for following assigned states: enthalpy and pressure, temperature and pressure, internal energy and volume, and temperature and volume. Written in FORTRAN 77 with exception of NAMELIST extensions used for input.

Study on copper kinetics in processing sulphide ore mixed with copper and zinc with sulfuric acid leaching under pressure

NASA Astrophysics Data System (ADS)

Wen-bo, LUO; Ji-kun, WANG; Yin, GAN

2018-01-01

Sulphide ore mixed with copper and zinc is processed with pressure acid leaching. Research is conducted on the copper kinetic. The stirring rate is set at 600 rpm which could eliminate the influence of external diffusions. Research is conducted on the factors affecting the copper leaching kinetic are temperature, pressure, concentration of sulfuric acid, particle size. The result shows that the apparent activity energy is 50.7 KJ/mol. We could determine that the copper leaching process is shrinking core model of chemical reaction control and work out the leaching equation.

Energy spectrum and kinetics of the fusing particles

NASA Astrophysics Data System (ADS)

Ryutov, D. D.; Putvinski, s. V.; Yushmanov, P. N.; TAE Team

2017-10-01

The fusing particles (e.g., D and T, or p and 11B) contribution to the reaction rate can be found by the integration of the fusion reactivity over the particle distribution functions. The distribution function (e.g., Maxwellian) is depleted in the energy range determined by the highest reactivity and has to be replenished by particle collisions. The kinetics of the replenishment process may affect the rate of fusion energy release. We present a simple analysis of the corresponding kinetic problems for the conditions typical for the standard and advanced-fuel fusion reactions and assess the possible effect on the reaction yield.

Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coloma Ribera, R., E-mail: r.colomaribera@utwente.nl; Kruijs, R. W. E. van de; Yakshin, A. E.

2015-08-07

In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

Effect of surfactant on kinetics of thinning of capillary bridges

NASA Astrophysics Data System (ADS)

Nowak, Emilia; Kovalchuk, Nina; Simmons, Mark

2015-11-01

Kinetics of thinning of capillary bridges is of great scientific and industrial interest being of vital importance for example in various emulsification and microfluidic processes. It is well known that the rate of bridge thinning is proportional to the interfacial tension. Therefore it is expected that the process should slow down by addition of surfactant. The kinetics of capillary bridges in the presence of surfactant was studied by the dripping of liquid from a capillary tip under conditions of nearly zero flow rate (We << 1). The tested liquids were aqueous solutions of sodium lauryl ether sulphate (SLES), which is broadly used in personal care products. The viscosity, surfactant activity and adsorption kinetics have been controlled by addition of glycerol and sodium chloride. The study has shown that the kinetics of capillary bridges are determined by dynamic surface tension rather than by its equilibrium value. In particular, the kinetics of the bridge thinning for the 0.1 g L-1 aqueous SLES solution is practically the same as that of pure water despite twice lower equilibrium surface tension. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

SigrafW: An easy-to-use program for fitting enzyme kinetic data.

PubMed

Leone, Francisco Assis; Baranauskas, José Augusto; Furriel, Rosa Prazeres Melo; Borin, Ivana Aparecida

2005-11-01

SigrafW is Windows-compatible software developed using the Microsoft® Visual Basic Studio program that uses the simplified Hill equation for fitting kinetic data from allosteric and Michaelian enzymes. SigrafW uses a modified Fibonacci search to calculate maximal velocity (V), the Hill coefficient (n), and the enzyme-substrate apparent dissociation constant (K). The estimation of V, K, and the sum of the squares of residuals is performed using a Wilkinson nonlinear regression at any Hill coefficient (n). In contrast to many currently available kinetic analysis programs, SigrafW shows several advantages for the determination of kinetic parameters of both hyperbolic and nonhyperbolic saturation curves. No initial estimates of the kinetic parameters are required, a measure of the goodness-of-the-fit for each calculation performed is provided, the nonlinear regression used for calculations eliminates the statistical bias inherent in linear transformations, and the software can be used for enzyme kinetic simulations either for educational or research purposes. Persons interested in receiving a free copy of the software should contact Dr. F. A. Leone. Copyright © 2005 International Union of Biochemistry and Molecular Biology, Inc.

New types of experimental data shape the use of enzyme kinetics for dynamic network modeling.

PubMed

Tummler, Katja; Lubitz, Timo; Schelker, Max; Klipp, Edda

2014-01-01

Since the publication of Leonor Michaelis and Maude Menten's paper on the reaction kinetics of the enzyme invertase in 1913, molecular biology has evolved tremendously. New measurement techniques allow in vivo characterization of the whole genome, proteome or transcriptome of cells, whereas the classical enzyme essay only allows determination of the two Michaelis-Menten parameters V and K(m). Nevertheless, Michaelis-Menten kinetics are still commonly used, not only in the in vitro context of enzyme characterization but also as a rate law for enzymatic reactions in larger biochemical reaction networks. In this review, we give an overview of the historical development of kinetic rate laws originating from Michaelis-Menten kinetics over the past 100 years. Furthermore, we briefly summarize the experimental techniques used for the characterization of enzymes, and discuss web resources that systematically store kinetic parameters and related information. Finally, describe the novel opportunities that arise from using these data in dynamic mathematical modeling. In this framework, traditional in vitro approaches may be combined with modern genome-scale measurements to foster thorough understanding of the underlying complex mechanisms. © 2013 FEBS.

Degradation kinetics of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside during hot air and vacuum drying in mulberry (Morus alba L.) fruit: A comparative study based on solid food system.

PubMed

Zhou, Mo; Chen, Qinqin; Bi, Jinfeng; Wang, Yixiu; Wu, Xinye

2017-08-15

The aim of this study is to ascertain the degradation kinetic of anthocyanin in dehydration process of solid food system. Mulberry fruit was treated by hot air and vacuum drying at 60 and 75°C. The contents of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside were determined by using high performance liquid chromatography. Kinetic and thermodynamic parameters were calculated for analysing the degradation characteristics. Model fitting results showed monomeric anthocyanin degradations were followed the second-order kinetic. Vacuum drying presented high kinetic rate constants and low t 1/2 values. Thermodynamic parameters including the activation energy, enthalpy change and entropy change appeared significant differences between hot air and vacuum drying. Both heating techniques showed similar effects on polyphenol oxidase activities. These results indicate the anthocyanin degradation kinetic in solid food system is different from that in liquid and the oxygen can be regarded as a catalyst to accelerate the degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pressure dependence of the photocycle kinetics of bacteriorhodopsin.

PubMed Central

Klink, B U; Winter, R; Engelhard, M; Chizhov, I

2002-01-01

The pressure dependence of the photocycle kinetics of bacteriorhodopsin from Halobacterium salinarium was investigated at pressures up to 4 kbar at 25 degrees C and 40 degrees C. The kinetics can be adequately modeled by nine apparent rate constants, which are assigned to irreversible transitions of a single relaxation chain of nine kinetically distinguishable states P(1) to P(9). All states except P(1) and P(9) consist of two or more spectral components. The kinetic states P(2) to P(6) comprise only the two fast equilibrating spectral states L and M. From the pressure dependence, the volume differences DeltaV(o)(LM) between these two spectral states could be determined that range from DeltaV(o)(LM) = -11.4 +/- 0.7 ml/mol (P(2)) to DeltaV(o)(LM) = 14.6 +/- 2.8 mL/mol (P(6)). A model is developed that explains the dependence of DeltaV(o)(LM) on the kinetic state by the electrostriction effect of charges, which are formed and neutralized during the L/M transition. PMID:12496115

[superscript 31]P NMR of the Pyruvate Kinase Reaction: An Undergraduate Experiment in Enzyme Kinetics

ERIC Educational Resources Information Center

Werner, R. Marshall; Johnson, Austin

2017-01-01

Understanding how to perform an enzyme assay is a critical learning skill in the undergraduate biochemistry curriculum. Students in biochemistry typically have been exposed to the use of NMR spectroscopy as a tool to determine chemical structure, but rarely are they exposed to the utility of NMR to evaluate enzyme kinetics. Furthermore, coverage…

Kinetic properties of two Rhizopus exo-polygalacturonase enzymes hydrolyzing galacturonic acid oligomers using isothermal titration calorimetry

USDA-ARS?s Scientific Manuscript database

The kinetic characteristics of two Rhizopus oryzae exo-polygalacturonases acting on galacturonic acid oligomers (GalpA) were determined using isothermal titration calorimetry (ITC). RPG15 hydrolyzing (GalpA)2 demonstrated a Km of 55 uM and kcat of 10.3 s^-1^ while RPG16 was shown to have greater af...

Real-Time Enzyme Kinetics by Quantitative NMR Spectroscopy and Determination of the Michaelis-Menten Constant Using the Lambert-W Function

ERIC Educational Resources Information Center

Her, Cheenou; Alonzo, Aaron P.; Vang, Justin Y.; Torres, Ernesto; Krishnan, V. V.

2015-01-01

Enzyme kinetics is an essential part of a chemistry curriculum, especially for students interested in biomedical research or in health care fields. Though the concept is routinely performed in undergraduate chemistry/biochemistry classrooms using other spectroscopic methods, we provide an optimized approach that uses a real-time monitoring of the…

Modelling the effect of acoustic waves on the thermodynamics and kinetics of phase transformation in a solution: Including mass transportation

NASA Astrophysics Data System (ADS)

Haqshenas, S. R.; Ford, I. J.; Saffari, N.

2018-01-01

Effects of acoustic waves on a phase transformation in a metastable phase were investigated in our previous work [S. R. Haqshenas, I. J. Ford, and N. Saffari, "Modelling the effect of acoustic waves on nucleation," J. Chem. Phys. 145, 024315 (2016)]. We developed a non-equimolar dividing surface cluster model and employed it to determine the thermodynamics and kinetics of crystallisation induced by an acoustic field in a mass-conserved system. In the present work, we developed a master equation based on a hybrid Szilard-Fokker-Planck model, which accounts for mass transportation due to acoustic waves. This model can determine the kinetics of nucleation and the early stage of growth of clusters including the Ostwald ripening phenomenon. It was solved numerically to calculate the kinetics of an isothermal sonocrystallisation process in a system with mass transportation. The simulation results show that the effect of mass transportation for different excitations depends on the waveform as well as the imposed boundary conditions and tends to be noticeable in the case of shock waves. The derivations are generic and can be used with any acoustic source and waveform.

Modeling the kinetics of survival of Staphylococcus aureus in regional yogurt from goat's milk.

PubMed

Bednarko-Młynarczyk, E; Szteyn, J; Białobrzewski, I; Wiszniewska-Łaszczych, A; Liedtke, K

2015-01-01

The aim of this study was to determine the kinetics of the survival of the test strain of Staphylococcus aureus in the product investigated. Yogurt samples were contaminated with S. aure to an initial level of 10(3)-10(4) cfu/g. The samples were then stored at four temperatures: 4, 6, 20, 22°C. During storage, the number of S. aureus forming colonies in a gram of yogurt was determined every two hours. Based on the results of the analysis culture the curves of survival were plotted. Three primary models were selected to describe the kinetics of changes in the count of bacteria: Cole's model, a modified model of Gompertz and the model of Baranyi and Roberts. Analysis of the model fit carried out based on the average values of Pearson's correlation coefficient, between the modeled and measured values, showed that the Cole's model had the worst fit. The modified Gompertz model showed the count of S. aureus as a negative value. These drawbacks were not observed in the model of Baranyi and Roberts. For this reason, this model best reflects the kinetics of changes in the number of staphylococci in yogurt.

Ion-polycyclic aromatic hydrocarbon collisions: kinetic energy releases for specific fragmentation channels

NASA Astrophysics Data System (ADS)

Reitsma, G.; Zettergren, H.; Boschman, L.; Bodewits, E.; Hoekstra, R.; Schlathölter, T.

2013-12-01

We report on 30 keV He2 + collisions with naphthalene (C10H8) molecules, which leads to very extensive fragmentation. To unravel such complex fragmentation patterns, we designed and constructed an experimental setup, which allows for the determination of the full momentum vector by measuring charged collision products in coincidence in a recoil ion momentum spectrometer type of detection scheme. The determination of fragment kinetic energies is found to be considerably more accurate than for the case of mere coincidence time-of-flight spectrometers. In fission reactions involving two cationic fragments, typically kinetic energy releases of 2-3 eV are observed. The results are interpreted by means of density functional theory calculations of the reverse barriers. It is concluded that naphthalene fragmentation by collisions with keV ions clearly is much more violent than the corresponding photofragmentation with energetic photons. The ion-induced naphthalene fragmentation provides a feedstock of various small hydrocarbonic species of different charge states and kinetic energy, which could influence several molecule formation processes in the cold interstellar medium and facilitates growth of small hydrocarbon species on pre-existing polycyclic aromatic hydrocarbons.

Modelling the effect of acoustic waves on the thermodynamics and kinetics of phase transformation in a solution: Including mass transportation.

PubMed

Haqshenas, S R; Ford, I J; Saffari, N

2018-01-14

Effects of acoustic waves on a phase transformation in a metastable phase were investigated in our previous work [S. R. Haqshenas, I. J. Ford, and N. Saffari, "Modelling the effect of acoustic waves on nucleation," J. Chem. Phys. 145, 024315 (2016)]. We developed a non-equimolar dividing surface cluster model and employed it to determine the thermodynamics and kinetics of crystallisation induced by an acoustic field in a mass-conserved system. In the present work, we developed a master equation based on a hybrid Szilard-Fokker-Planck model, which accounts for mass transportation due to acoustic waves. This model can determine the kinetics of nucleation and the early stage of growth of clusters including the Ostwald ripening phenomenon. It was solved numerically to calculate the kinetics of an isothermal sonocrystallisation process in a system with mass transportation. The simulation results show that the effect of mass transportation for different excitations depends on the waveform as well as the imposed boundary conditions and tends to be noticeable in the case of shock waves. The derivations are generic and can be used with any acoustic source and waveform.

Experimental and modeling study on decomposition kinetics of methane hydrates in different media.

PubMed

Liang, Minyan; Chen, Guangjin; Sun, Changyu; Yan, Lijun; Liu, Jiang; Ma, Qinglan

2005-10-13

The decomposition kinetic behaviors of methane hydrates formed in 5 cm3 porous wet activated carbon were studied experimentally in a closed system in the temperature range of 275.8-264.4 K. The decomposition rates of methane hydrates formed from 5 cm3 of pure free water and an aqueous solution of 650 g x m(-3) sodium dodecyl sulfate (SDS) were also measured for comparison. The decomposition rates of methane hydrates in seven different cases were compared. The results showed that the methane hydrates dissociate more rapidly in porous activated carbon than in free systems. A mathematical model was developed for describing the decomposition kinetic behavior of methane hydrates below ice point based on an ice-shielding mechanism in which a porous ice layer was assumed to be formed during the decomposition of hydrate, and the diffusion of methane molecules through it was assumed to be one of the control steps. The parameters of the model were determined by correlating the decomposition rate data, and the activation energies were further determined with respect to three different media. The model was found to well describe the decomposition kinetic behavior of methane hydrate in different media.

Determination of kinetic parameters of 1,3-propanediol fermentation by Clostridium diolis using statistically optimized medium.

PubMed

Kaur, Guneet; Srivastava, Ashok K; Chand, Subhash

2012-09-01

1,3-propanediol (1,3-PD) is a chemical compound of immense importance primarily used as a raw material for fiber and textile industry. It can be produced by the fermentation of glycerol available abundantly as a by-product from the biodiesel plant. The present study was aimed at determination of key kinetic parameters of 1,3-PD fermentation by Clostridium diolis. Initial experiments on microbial growth inhibition were followed by optimization of nutrient medium recipe by statistical means. Batch kinetic data from studies in bioreactor using optimum concentration of variables obtained from statistical medium design was used for estimation of kinetic parameters of 1,3-PD production. Direct use of raw glycerol from biodiesel plant without any pre-treatment for 1,3-PD production using this strain investigated for the first time in this work gave results comparable to commercial glycerol. The parameter values obtained in this study would be used to develop a mathematical model for 1,3-PD to be used as a guide for designing various reactor operating strategies for further improving 1,3-PD production. An outline of protocol for model development has been discussed in the present work.

A kinetic study of ferrocenium cation decomposition utilizing an integrated electrochemical methodology composed of cyclic voltammetry and amperometry.

PubMed

Singh, Archana; Chowdhury, Debarati Roy; Paul, Amit

2014-11-21

A novel, easy, quick, and inexpensive integrated electrochemical methodology composed of cyclic voltammetry and amperometry has been developed for the determination of the kinetic stability of higher oxidation states for inorganic complexes. In this study, ferrocene and its derivatives have been used as model systems and the corresponding ferrocenium cations were generated in situ during the electrochemical experiments to determine their kinetic stabilities. The study found that the ferrocenium cations decompose following the first-order kinetics at 27 ± 3 °C in the presence of ambient oxygen and water. The half-lives of the ferrocenium, carboxylate ferrocenium, and decamethyl ferrocenium cations were found to be 1.27 × 10(3), 1.52 × 10(3), and ≫11.0 × 10(3) s, respectively, in acetonitrile solvent having a 0.5 M tetrabutylammonium hexafluorophosphate electrolyte. These results are in agreement with the previous reports, i.e. the ferrocenium cation is unstable whereas the decamethyl ferrocenium cation has superior stability. The new methodology has been established by performing various experiments using different concentrations of ferrocene, variable scan rates in cyclic voltammetry, different time periods for amperometry, and in situ spectroelectrochemical experiments.

A Method for Decomposition of the Basic Reaction of Biological Macromolecules into Exponential Components

NASA Astrophysics Data System (ADS)

Barabash, Yu. M.; Lyamets, A. K.

2016-12-01

The structural and dynamical properties of biological macromolecules under non-equilibrium conditions determine the kinetics of their basic reaction to external stimuli. This kinetics is multiexponential in nature. This is due to the operation of various subsystems in the structure of macromolecules, as well as the effect of the basic reaction on the structure of macromolecules. The situation can be interpreted as a manifestation of the stationary states of macromolecules, which are represented by monoexponential components of the basic reaction (Monod-Wyman-Changeux model) Monod et al. (J Mol Cell Biol 12:88-118, 1965). The representation of multiexponential kinetics of the basic reaction in the form of a sum of exponential functions (A(t)={sum}_{i=1}^n{a}_i{e}^{-{k}_it}) is a multidimensional optimization problem. To solve this problem, a gradient method of optimization with software determination of the amount of exponents and reasonable calculation time is developed. This method is used to analyze the kinetics of photoinduced electron transport in the reaction centers (RC) of purple bacteria and the fluorescence induction in the granum thylakoid membranes which share a common function of converting light energy.

Influence of porogen nature on the kinetic and potential efficiencies of divinylbenzene-based monolithic sorbents in gas chromatography

NASA Astrophysics Data System (ADS)

Korolev, A. A.; Shiryaeva, V. E.; Popova, T. P.; Kanat'eva, A. Yu.; Kurganov, A. A.

2015-02-01

It has been shown that using Poppe curves for characterization of monolithic sorbents makes it possible to optimize conditions for both the synthesis of monoliths intended for high-speed analysis and achievement of the best separation efficiency. The influence of the nature of a porogen on the kinetic efficiency of monolithic sorbents in high-pressure gas chromatography has been considered. It has been found that the nature of the porogen alcohol determines to a considerable extent the structure of the monolith and its kinetic efficiency. The sorbents prepared with the use of octanol-1 and dodecanol-1 have shown the best kinetic characteristics; however, minimal HETP values have been observed for the columns prepared using hexanol-1 as a porogen.

Oxidation of isoniazid by quinolinium dichromate in an aqueous acid medium and kinetic determination of isoniazid in pure and pharmaceutical formulations.

PubMed

Kulkarni, Raviraj M; Bilehal, Dinesh C; Nandibewoor, Sharanappa T

2004-04-01

The kinetics of oxidation of isoniazid in acidic medium was studied spectrophotometrically. The reaction between QDC and isoniazid in acid medium exhibits (4:1) stoichiometry (QDC:isoniazid). The reaction showed first order kinetics in quinolinium dichromate (QDC) concentration and an order of less than unity in isoniazid (INH) and acid concentrations. The oxidation reaction proceeds via a protonated QDC species, which forms a complex with isoniazid. The latter decomposes in a slow step to give a free radical derived from isoniazid and an intermediate chromium(V), which is followed, by subsequent fast steps to give the products. The reaction constants involved in the mechanism are evaluated. Isoniazid was analyzed by kinetic methods in pure and pharmaceutical formulations.

Reliability and Validity of Kinetic and Kinematic Parameters Determined With Force Plates Embedded Under a Soil-Filled Baseball Mound.

PubMed

Yanai, Toshimasa; Matsuo, Akifumi; Maeda, Akira; Nakamoto, Hiroki; Mizutani, Mirai; Kanehisa, Hiroaki; Fukunaga, Tetsuo

2017-08-01

We developed a force measurement system in a soil-filled mound for measuring ground reaction forces (GRFs) acting on baseball pitchers and examined the reliability and validity of kinetic and kinematic parameters determined from the GRFs. Three soil-filled trays of dimensions that satisfied the official baseball rules were fixed onto 3 force platforms. Eight collegiate pitchers wearing baseball shoes with metal cleats were asked to throw 5 fastballs with maximum effort from the mound toward a catcher. The reliability of each parameter was determined for each subject as the coefficient of variation across the 5 pitches. The validity of the measurements was tested by comparing the outcomes either with the true values or the corresponding values computed from a motion capture system. The coefficients of variation in the repeated measurements of the peak forces ranged from 0.00 to 0.17, and were smaller for the pivot foot than the stride foot. The mean absolute errors in the impulses determined over the entire duration of pitching motion were 5.3 N˙s, 1.9 N˙s, and 8.2 N˙s for the X-, Y-, and Z-directions, respectively. These results suggest that the present method is reliable and valid for determining selected kinetic and kinematic parameters for analyzing pitching performance.

Mechanistic Kinetic Modeling of Thiol-Michael Addition Photopolymerizations via Photocaged "Superbase" Generators: An Analytical Approach.

PubMed

Claudino, Mauro; Zhang, Xinpeng; Alim, Marvin D; Podgórski, Maciej; Bowman, Christopher N

2016-11-08

A kinetic mechanism and the accompanying mathematical framework are presented for base-mediated thiol-Michael photopolymerization kinetics involving a photobase generator. Here, model kinetic predictions demonstrate excellent agreement with a representative experimental system composed of 2-(2-nitrophenyl)propyloxycarbonyl-1,1,3,3-tetramethylguanidine (NPPOC-TMG) as a photobase generator that is used to initiate thiol-vinyl sulfone Michael addition reactions and polymerizations. Modeling equations derived from a basic mechanistic scheme indicate overall polymerization rates that follow a pseudo-first-order kinetic process in the base and coreactant concentrations, controlled by the ratio of the propagation to chain-transfer kinetic parameters ( k p / k CT ) which is dictated by the rate-limiting step and controls the time necessary to reach gelation. Gelation occurs earlier as the k p / k CT ratio reaches a critical value, wherefrom gel times become nearly independent of k p / k CT . The theoretical approach allowed determining the effect of induction time on the reaction kinetics due to initial acid-base neutralization for the photogenerated base caused by the presence of protic contaminants. Such inhibition kinetics may be challenging for reaction systems that require high curing rates but are relevant for chemical systems that need to remain kinetically dormant until activated although at the ultimate cost of lower polymerization rates. The pure step-growth character of this living polymerization and the exhibited kinetics provide unique potential for extended dark-cure reactions and uniform material properties. The general kinetic model is applicable to photobase initiators where photolysis follows a unimolecular cleavage process releasing a strong base catalyst without cogeneration of intermediate radical species.

Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.

PubMed

Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

2015-01-01

Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants. Copyright © 2014. Published by Elsevier B.V.

Kinetic determination of propranolol in tablets by oxidation with ceric sulphate.

PubMed

Sultan, S M; Altamrah, S A; Aziz Alrahman, A M; Alzamil, I Z; Karrar, M O

1989-01-01

A simple and accurate kinetic method for the determination of propranolol has been developed. Cerium(IV) sulphate (0.5 M) is used to oxidize propranolol in 2 M sulphuric acid at room temperature to the ketone form that absorbs light at a lambda max of 525 nm. The fixed-concentration method is used by recording the exact time, t(s), taken for the reaction to reach a fixed absorbance of 0.100. The unknown concentration, c(M), of propranolol is calculated from the equation: l/t = 0 0.000217 + 0.03 c. The method has been applied to the determination of propranolol in proprietary tablets and the results were compared with those obtained by the B.P. and other standard methods.

Methodology for extracting local constants from petroleum cracking flows

DOEpatents

Chang, Shen-Lin; Lottes, Steven A.; Zhou, Chenn Q.

2000-01-01

A methodology provides for the extraction of local chemical kinetic model constants for use in a reacting flow computational fluid dynamics (CFD) computer code with chemical kinetic computations to optimize the operating conditions or design of the system, including retrofit design improvements to existing systems. The coupled CFD and kinetic computer code are used in combination with data obtained from a matrix of experimental tests to extract the kinetic constants. Local fluid dynamic effects are implicitly included in the extracted local kinetic constants for each particular application system to which the methodology is applied. The extracted local kinetic model constants work well over a fairly broad range of operating conditions for specific and complex reaction sets in specific and complex reactor systems. While disclosed in terms of use in a Fluid Catalytic Cracking (FCC) riser, the inventive methodology has application in virtually any reaction set to extract constants for any particular application and reaction set formulation. The methodology includes the step of: (1) selecting the test data sets for various conditions; (2) establishing the general trend of the parametric effect on the measured product yields; (3) calculating product yields for the selected test conditions using coupled computational fluid dynamics and chemical kinetics; (4) adjusting the local kinetic constants to match calculated product yields with experimental data; and (5) validating the determined set of local kinetic constants by comparing the calculated results with experimental data from additional test runs at different operating conditions.

Energy dynamics and current sheet structure in fluid and kinetic simulations of decaying magnetohydrodynamic turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makwana, K. D., E-mail: kirit.makwana@gmx.com; Cattaneo, F.; Zhdankin, V.

Simulations of decaying magnetohydrodynamic (MHD) turbulence are performed with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k{sub ⊥}{sup −1.3}. The kinetic code shows a spectral slope of k{submore » ⊥}{sup −1.5} for smaller simulation domain, and k{sub ⊥}{sup −1.3} for larger domain. We estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. This work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.« less

[Study on the kinetic fluorimetric determination of tannins in tea].

PubMed

Feng, Su-ling; Tang, Jun-ming; Fan, Jing

2003-04-01

A simple and highly sensitive kinetic fluorimetric method is proposed for the determination of trace tannins, based on the activation of tannins on the oxidation of pyronine Y by hydrogen peroxide catalyzed by Cu(II) ion. The effects of some experimental conditions were investigated and discussed in detail. The fixed reaction time procedure was used to determine the fluorescence intensity of the system. The calibration curve of tannin was linear in the range of 0.06-0.96 mg.L-1, and the detection limit for tannin was 0.032 mg.L-1. The relative standard deviation for the measurement of 0.32 mg.L-1 tannin (n = 11) was 2.3%. The proposed method has been successfully applied to the determination of tannins in tea. The results obtained were compared with those provided by the Folin-Ciocalteu method.

Kinetics of the cellular decomposition of supersaturated solid solutions

NASA Astrophysics Data System (ADS)

Ivanov, M. A.; Naumuk, A. Yu.

2014-09-01

A consistent description of the kinetics of the cellular decomposition of supersaturated solid solutions with the development of a spatially periodic structure of lamellar (platelike) type, which consists of alternating phases of precipitates on the basis of the impurity component and depleted initial solid solution, is given. One of the equations, which determines the relationship between the parameters that describe the process of decomposition, has been obtained from a comparison of two approaches in order to determine the rate of change in the free energy of the system. The other kinetic parameters can be described with the use of a variational method, namely, by the maximum velocity of motion of the decomposition boundary at a given temperature. It is shown that the mutual directions of growth of the lamellae of different phases are determined by the minimum value of the interphase surface energy. To determine the parameters of the decomposition, a simple thermodynamic model of states with a parabolic dependence of the free energy on the concentrations has been used. As a result, expressions that describe the decomposition rate, interlamellar distance, and the concentration of impurities in the phase that remain after the decomposition have been derived. This concentration proves to be equal to the half-sum of the initial concentration and the equilibrium concentration corresponding to the decomposition temperature.

Development and characterization of a dynamic lesion phantom for the quantitative evaluation of dynamic contrast-enhanced MRI.

PubMed

Freed, Melanie; de Zwart, Jacco A; Hariharan, Prasanna; Myers, Matthew R; Badano, Aldo

2011-10-01

To develop a dynamic lesion phantom that is capable of producing physiological kinetic curves representative of those seen in human dynamic contrast-enhanced MRI (DCE-MRI) data. The objective of this phantom is to provide a platform for the quantitative comparison of DCE-MRI protocols to aid in the standardization and optimization of breast DCE-MRI. The dynamic lesion consists of a hollow, plastic mold with inlet and outlet tubes to allow flow of a contrast agent solution through the lesion over time. Border shape of the lesion can be controlled using the lesion mold production method. The configuration of the inlet and outlet tubes was determined using fluid transfer simulations. The total fluid flow rate was determined using x-ray images of the lesion for four different flow rates (0.25, 0.5, 1.0, and 1.5 ml/s) to evaluate the resultant kinetic curve shape and homogeneity of the contrast agent distribution in the dynamic lesion. High spatial and temporal resolution x-ray measurements were used to estimate the true kinetic curve behavior in the dynamic lesion for benign and malignant example curves. DCE-MRI example data were acquired of the dynamic phantom using a clinical protocol. The optimal inlet and outlet tube configuration for the lesion molds was two inlet molds separated by 30° and a single outlet tube directly between the two inlet tubes. X-ray measurements indicated that 1.0 ml/s was an appropriate total fluid flow rate and provided truth for comparison with MRI data of kinetic curves representative of benign and malignant lesions. DCE-MRI data demonstrated the ability of the phantom to produce realistic kinetic curves. The authors have constructed a dynamic lesion phantom, demonstrated its ability to produce physiological kinetic curves, and provided estimations of its true kinetic curve behavior. This lesion phantom provides a tool for the quantitative evaluation of DCE-MRI protocols, which may lead to improved discrimination of breast cancer lesions.

Kinetics and Near-Infrared Spectroscopy of Organic Peroxy Radicals

NASA Astrophysics Data System (ADS)

Smarte, M. D.; Okumura, M.

2016-12-01

Organic peroxy radicals are important intermediates in atmospheric chemistry with fates that control the rate of radical propagation in an oxidation mechanism. Laboratory methods for detecting peroxy radicals are essential to measuring precise rate constants that constrain these fates. In this work, we discuss the use of near-infrared cavity ringdown spectroscopy to detect organic peroxy radicals for the purpose of laboratory kinetics measurements. We focus on chlorine-substituted peroxy radicals generated in the oxidation of alkenes by chlorine, a minor tropospheric oxidant found in marine and coastal regions. Previous kinetics experiments on peroxy radicals have largely used UV absorption spectroscopy via the dissociative B-X transition. However, the spectra produced are featureless and exhibit substantial overlap; determining the concentration profile of an individual peroxy radical can be an arduous task. In our work, we probe the forbidden peroxy radical A-X transition in the near-infrared. While this approach requires overcoming small cross sections ( 10-21 cm2), the A state is bound and leads to structured absorption spectra that may be useful in constraining the kinetics of mixtures of organic peroxy radicals formed in the oxidation of complex hydrocarbons. Only a few kinetics studies utilizing the A-X transition exist in the literature and they are focused on small, unsubstituted species. This presentation explores the ability of the A-X transition to unravel the kinetics of more complex peroxy radicals in laboratory experiments using several example systems: (1) Determining rate constants for the self and cross reactions of β-chloroethylperoxy and HO2. (2) Detecting the second generation of peroxy radicals formed from alkoxy radical decomposition in the chlorine-initiated oxidation of 2-butene. (3) Observing different rates of reactivity with NO across the pool of peroxy radical isomers formed in the chlorine-initiated oxidation of isoprene.

Bright flash response recovery of mammalian rods in vivo is rate limited by RGS9

PubMed Central

Peinado Allina, Gabriel; Fortenbach, Christopher; Gross, Owen P.; Pugh, Edward N.

2017-01-01

The temporal resolution of scotopic vision is thought to be constrained by the signaling kinetics of retinal rods, which use a highly amplified G-protein cascade to transduce absorbed photons into changes in membrane potential. Much is known about the biochemical mechanisms that determine the kinetics of rod responses ex vivo, but the rate-limiting mechanisms in vivo are unknown. Using paired flash electroretinograms with improved signal-to-noise, we have recorded the amplitude and kinetics of rod responses to a wide range of flash strengths from living mice. Bright rod responses in vivo recovered nearly twice as fast as all previous recordings, although the kinetic consequences of genetic perturbations previously studied ex vivo were qualitatively similar. In vivo, the dominant time constant of recovery from bright flashes was dramatically reduced by overexpression of the RGS9 complex, revealing G-protein deactivation to be rate limiting for recovery. However, unlike previous ex vivo recordings, dim flash responses in vivo were relatively unaffected by RGS9 overexpression, suggesting that other mechanisms, such as calcium feedback dynamics that are strongly regulated by the restricted subretinal microenvironment, act to determine rod dim flash kinetics. To assess the consequences for scotopic vision, we used a nocturnal wheel-running assay to measure the ability of wild-type and RGS9-overexpressing mice to detect dim flickering stimuli and found no improvement when rod recovery was speeded by RGS9 overexpression. These results are important for understanding retinal circuitry, in particular as modeled in the large literature that addresses the relationship between the kinetics and sensitivity of retinal responses and visual perception. PMID:28302678

Measuring the Impact of AGN Outflows via Intensive UV and X-ray Monitoring Campaigns

NASA Astrophysics Data System (ADS)

Kriss, Gerard

2015-08-01

Observations of AGN outflows have progressed from the era of single-object surveys to intensive monitoring campaigns spanning weeks to months. The combination of multiple observations, improved temporal coverage, multi-wavelength monitoring in both the X-ray and UV bands, and the baseline of prior historical observations has enabled determinations of the locations, mass flux, and kinetic luminosities of the outflowing absorbing gas in several AGN, notably Mrk 509, NGC 5548, Mrk 335, and NGC 985. Another intensive campaign is planned for 2015-2016 on NGC 7469. In all cases, the mass flux and kinetic energy is dominated by the higher-ionization X-ray absorbing gas. But the higher-resolution UV observations give a kinematically resolved picture of the overall outflow. In most cases, the outflowing gas is located at parsec to kpc scales, with insufficient kinetic luminosity to have an evolutionary impact on the host galaxy. Typically, the kinetic luminosity is less than a percent of the Eddington luminosity. In some cases, transient, broad UV absorption troughs have appeared (e.g., Mrk 335 and NGC 5548), with variability timescales suggesting locations near the broad-line region of the AGN. Yet these higher-velocity outflows also have low-impact kinetic luminosities. In the best-studied case of NGC 5548, the strength of the broad UV absorption lines varies with the degree of soft X-ray obscuration first revealed by XMM-Newton spectra. The lower-ionization, narrow associated absorption lines in the UV spectrum of NGC 5548 that appeared concurrently with the soft X-ray obscuration vary in response to the changing UV flux on a daily basis. The intensive monitoring allows us to fit time-dependent photoionization models to the UV-absorbing gas, allowing precise determinations of the locations, mass flux, and kinetic luminosities of the absorbers.

Utilization of powdered waste sludge (PWS) for removal of textile dyestuffs from wastewater by adsorption.

PubMed

Ozmihci, Serpil; Kargi, Fikret

2006-11-01

Acid pre-treated powdered waste sludge (PWS) was used for removal of textile dyestuffs from aqueous medium by adsorption as an alternative to the use of powdered activated carbon (PAC). The rate and extent of dysetuff removals were determined for four different dyestuffs at different PWS concentrations varying between 1 and 6 gl(-1). Biosorbed dyestuff concentrations at equilibrium decreased with increasing PWS concentration for all dyestuffs tested. PWS was more effective for adsorption of Remazol red RR and Chrisofonia direct yellow 12 as compared to the other dyestuffs tested. More than 80% percent dyestuff removal was obtained for all dyestuffs at PWS concentrations above 4 gl(-1) after 6h of incubation. Similar to percent dyestuff removal, the rate of adsorption was maximum at a PWS concentration of 4 gl(-1). Kinetics of adsorption of dyestuffs was investigated by using the first- and second-order kinetic models and the kinetic constants were determined. Second-order kinetics was found to fit the experimental data better than the first-order model for all dyestuffs tested. Adsorption isotherms were established for all dyestuffs used and the isotherm constants were determined by using the experimental data. Langmuir and the generalized adsorption isotherms were found to be more suitable than the Freundlich isotherm for correlation of equilibrium adsorption data. Acid pre-treated PWS was proven to be an effective adsorbent for dyestuff removal as compared to the other adsorbents reported in literature studies.

Kv11.1 (hERG)-induced cardiotoxicity: a molecular insight from a binding kinetics study of prototypical Kv11.1 (hERG) inhibitors

PubMed Central

Yu, Z; IJzerman, A P; Heitman, L H

2015-01-01

Background and Purpose Drug-induced arrhythmia due to blockade of the Kv11.1 channel (also known as the hERG K+ channel) is a frequent side effect. Previous studies have primarily focused on equilibrium parameters, i.e. affinity or potency, of drug candidates at the channel. The aim of this study was to determine the kinetics of the interaction with the channel for a number of known Kv11.1 blockers and to explore a possible correlation with the affinity or physicochemical properties of these compounds. Experimental Approach The affinity and kinetic parameters of 15 prototypical Kv11.1 inhibitors were evaluated in a number of [3H]-dofetilide binding assays. The lipophilicity (logKW-C8) and membrane partitioning (logKW-IAM) of these compounds were determined by means of HPLC analysis. Key Results A novel [3H]-dofetilide competition association assay was set up and validated, which allowed us to determine the binding kinetics of the Kv11.1 blockers used in this study. Interestingly, the compounds' affinities (Ki values) were correlated to their association rates rather than dissociation rates. Overall lipophilicity or membrane partitioning of the compounds were not correlated to their affinity or rate constants for the channel. Conclusions and Implications A compound's affinity for the Kv11.1 channel is determined by its rate of association with the channel, while overall lipophilicity and membrane affinity are not. In more general terms, our findings provide novel insights into the mechanism of action for a compound's activity at the Kv11.1 channel. This may help to elucidate how Kv11.1-induced cardiotoxicity is governed and how it can be circumvented in the future. PMID:25296617

TECHNICAL NOTE: System for monitoring the evolution of the thermal expansion coefficient and autogenous deformation of hardening materials

NASA Astrophysics Data System (ADS)

Viviani, M.; Glisic, B.; Smith, I. F. C.

2006-12-01

This article presents an experimental system developed to determine the kinetic parameters of hardening materials. Kinetic parameters allow computation of the degree of reaction indices (DRIs). DRIs are used in predictive formulae for strength and are used to decouple the autogenous deformation (AD) and thermal deformation (TD). Although there are several methods to determine values for kinetic reaction parameters, most require extensive testing and large databases. A measurement system has been developed in order to determine kinetic parameters. The measurement system consists of optical fiber sensors embedded in specimens that are cured at varying temperatures and conditions. Sensors are used in pairs inside each specimen, and each pair has two deformation sensors that, aside from their axial stiffness, have the same characteristics. The study of the interaction between sensors and hardening material leads to establishment of a link between the deformations measured and the degree of reaction, by means of the newly developed concept of the equivalency point. The equivalency point is assumed to be an indicator of the degree of reaction and it allows the determination of the apparent activation energy (Ea) which defines the equivalent time. Equivalent time is a degree of reaction index (DRI) and it accounts for the combined effect of time and temperature in concrete. This new methodology has been used to predict the compressive strength and separate the AD and thermal expansion coefficient (TEC) in seven types of concrete. The measurement system allows gathering of data necessary for fast and efficient predictions. Due to its robustness and reduced dimensions it also has potential for in situ application.

Trapped particle stability for the kinetic stabilizer

NASA Astrophysics Data System (ADS)

Berk, H. L.; Pratt, J.

2011-08-01

A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favourable field-line curvature exists. The window of operation is determined for achieving magnetohydrodynamic (MHD) stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analysed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic-stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore, a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region.

Solidification kinetics of a Cu-Zr alloy: ground-based and microgravity experiments

NASA Astrophysics Data System (ADS)

Galenko, P. K.; Hanke, R.; Paul, P.; Koch, S.; Rettenmayr, M.; Gegner, J.; Herlach, D. M.; Dreier, W.; Kharanzhevski, E. V.

2017-04-01

Experimental and theoretical results obtained in the MULTIPHAS-project (ESA-European Space Agency and DLR-German Aerospace Center) are critically discussed regarding solidification kinetics of congruently melting and glass forming Cu50Zr50 alloy samples. The samples are investigated during solidification using a containerless technique in the Electromagnetic Levitation Facility [1]. Applying elaborated methodologies for ground-based and microgravity experimental investigations [2], the kinetics of primary dendritic solidification is quantitatively evaluated. Electromagnetic Levitator in microgravity (parabolic flights and on board of the International Space Station) and Electrostatic Levitator on Ground are employed. The solidification kinetics is determined using a high-speed camera and applying two evaluation methods: “Frame by Frame” (FFM) and “First Frame - Last Frame” (FLM). In the theoretical interpretation of the solidification experiments, special attention is given to the behavior of the cluster structure in Cu50Zr50 samples with the increase of undercooling. Experimental results on solidification kinetics are interpreted using a theoretical model of diffusion controlled dendrite growth.

Kinetic study of olive oil degradation monitored by fourier transform infrared spectrometry. Application to oil characterization.

PubMed

Román Falcó, Iván P; Grané Teruel, Nuria; Prats Moya, Soledad; Martín Carratalá, M Luisa

2012-11-28

A new approach for the determination of kinetic parameters of the cis/trans isomerization during the oxidation process of 24 virgin olive oils belonging to 8 different varieties is presented. The accelerated process of degradation at 100 °C was monitored by recording the Fourier transform infrared spectra. The parameters obtained confirm pseudo-first-order kinetics for the degradation of cis and the appearance of trans double bonds. The kinetic approach affords the induction time and the rate coefficient; these parameters are related to the fatty acid profile of the fresh olive oils. The data obtained were used to compare the oil stability of the samples with the help of multivariate statistical techniques. Fatty acid allowed a classification of the samples in five groups, one of them constituted by the cultivars with higher stability. Meanwhile, the kinetic parameters showed greater ability for the characterization of olive oils, allowing the classification in seven groups.

Kinetic profile of amyloid formation in the presence of an aromatic inhibitor by nuclear magnetic resonance.

PubMed

Liu, Gai; Gaines, Jennifer C; Robbins, Kevin J; Lazo, Noel D

2012-10-11

The self-assembly of amyloid proteins into β-sheet rich assemblies is associated with human amyloidoses including Alzheimer's disease, Parkinson's disease, and type 2 diabetes. An attractive therapeutic strategy therefore is to develop small molecules that would inhibit protein self-assembly. Natural polyphenols are potential inhibitors of β-sheet formation. How these compounds affect the kinetics of self-assembly studied by thioflavin T (ThT) fluorescence is not understood primarily because their presence interferes with ThT fluorescence. Here, we show that by plotting peak intensities from nuclear magnetic resonance (NMR) against incubation time, kinetic profiles in the presence of the polyphenol can be obtained from which kinetic parameters of self-assembly can be easily determined. In applying this technique to the self-assembly of the islet amyloid polypeptide in the presence of curcumin, a biphenolic compound found in turmeric, we show that the kinetic profile is atypical in that it shows a prenucleation period during which there is no observable decrease in NMR peak intensities.

Kinetic modeling of kraft delignification of Eucalyptus globulus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos, A.; Rodriguez, F.; Gilarranz, M.A.

1997-10-01

A kinetic model for the kraft pulping delignification of Eucalyptus globulus is proposed. This model is discriminated among some kinetic expressions often used in the literature, and the kinetic parameters are determined by fitting of experimental results. A total of 25 isothermal experiments at liquor-to-wood ratios of 50 and 5 L/kg have been carried out. Initial, bulk, and residual delignification stages have been observed during the lignin removal, the transitions being, referring to the lignin initial content, about 82 and 3%. Carbohydrate removal and effective alkali-metal and hydrosulfide consumption have been related with the lignin removal by means of effectivemore » stoichiometric coefficients for each stage, coefficients also being calculated by fitting of the experimental data. The kinetic model chosen has been used to simulate typical kraft pulping experiments carried out at nonisothermal conditions, using a temperature ramp. The model yields simulated values close to those obtained experimentally for the wood studied and also ably reproduces the trends of the literature data.« less

Co-pyrolysis kinetics of sewage sludge and bagasse using multiple normal distributed activation energy model (M-DAEM).

PubMed

Lin, Yan; Chen, Zhihao; Dai, Minquan; Fang, Shiwen; Liao, Yanfen; Yu, Zhaosheng; Ma, Xiaoqian

2018-07-01

In this study, the kinetic models of bagasse, sewage sludge and their mixture were established by the multiple normal distributed activation energy model. Blending with sewage sludge, the initial temperature declined from 437 K to 418 K. The pyrolytic species could be divided into five categories, including analogous hemicelluloses I, hemicelluloses II, cellulose, lignin and bio-char. In these species, the average activation energies and the deviations situated at reasonable ranges of 166.4673-323.7261 kJ/mol and 0.1063-35.2973 kJ/mol, respectively, which were conformed to the references. The kinetic models were well matched to experimental data, and the R 2 were greater than 99.999%y. In the local sensitivity analysis, the distributed average activation energy had stronger effect on the robustness than other kinetic parameters. And the content of pyrolytic species determined which series of kinetic parameters were more important. Copyright © 2018 Elsevier Ltd. All rights reserved.

Kinetic and equilibrium characteristics of sorption of saponin of Quillaja Saponaria Molina on chitosan

NASA Astrophysics Data System (ADS)

Mironenko, N. V.; Smuseva, S. O.; Brezhneva, T. A.; Selemenev, V. F.

2016-12-01

The equilibrium and kinetic curves of the sorption of saponin of Quillaja saponaria molina on chitosan were analyzed. The inner diffusion was found to be limiting, and its coefficients were calculated. It was found that the form of the curves of the sorption isotherms of saponin is determined by the competing processes of association in solution and absorption by chitosan.

A Simple Laboratory Experiment to Determine the Kinetics of Mutarotation of D-Glucose Using a Blood Glucose Meter

ERIC Educational Resources Information Center

Perles, Carlos E.; Volpe, Pedro L. O.

2008-01-01

A simple commercial blood glucose meter is used to follow the kinetics of mutarotation of D-glucose in aqueous solution. The results may be compared with those obtained using an automatic polarimeter, if this is available This experiment is proposed for use by students in a general chemistry, biology, organic chemistry, and physical chemistry…

Chemical reactions at aqueous interfaces

NASA Astrophysics Data System (ADS)

Vecitis, Chad David

2009-12-01

Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1) Adsorption of dilute PFOS(aq) and PFOA(aq) to acoustically cavitating bubble interfaces was greater than equilibrium expectations due to high-velocity bubble radial oscillations; 2) Relative ozone oxidation kinetics of aqueous iodide, sulfite, and thiosulfate were at variance with previously reported bulk aqueous kinetics; 3) Organics that directly chelated with the anode surface were oxidized by direct electron transfer, resulting in immediate carbon dioxide production but slower overall oxidation kinetics. Chemical reactions at aqueous interfaces can be the rate-limiting step of a reaction network and often display novel mechanisms and kinetics as compared to homogeneous chemistry.

Binding kinetics of five drugs to beta2-adrenoceptor using peak profiling method and nonlinear chromatography.

PubMed

Liang, Yuan; Wang, Jing; Fei, Fuhuan; Sun, Huanmei; Liu, Ting; Li, Qian; Zhao, Xinfeng; Zheng, Xiaohui

2018-02-23

Investigations of drug-protein interactions have advanced our knowledge of ways to design more rational drugs. In addition to extensive thermodynamic studies, ongoing works are needed to enhance the exploration of drug-protein binding kinetics. In this work, the beta2-adrenoceptor (β 2 -AR) was immobilized on N, N'-carbonyldiimidazole activated amino polystyrene microspheres to prepare an affinity column (4.6 mm × 5.0 cm, 8 μm). The β 2 -AR column was utilized to determine the binding kinetics of five drugs to the receptor. Introducing peak profiling method into this receptor chromatographic analysis, we determined the dissociation rate constants (k d ) of salbutamol, terbutaline, methoxyphenamine, isoprenaline hydrochloride and ephedrine hydrochloride to β 2 -AR to be 15 (±1), 22 (±1), 3.3 (±0.2), 2.3 (±0.2) and 2.1 (±0.1) s -1 , respectively. The employment of nonlinear chromatography (NLC) in this case exhibited the same rank order of k d values for the five drugs bound to β 2 -AR. We confirmed that both the peak profiling method and NLC were capable of routine measurement of receptor-drug binding kinetics. Compared with the peak profiling method, NLC was advantageous in the simultaneous assessment of the kinetic and apparent thermodynamic parameters. It will become a powerful method for high throughput drug-receptor interaction analysis. Copyright © 2018 Elsevier B.V. All rights reserved.

Calcium tracer kinetics show decreased irreversible flow to bone in glucocorticoid treated patients.

PubMed

Goans, R E; Weiss, G H; Abrams, S A; Perez, M D; Yergey, A L

1995-06-01

Osteopenia resulting from pharmacologic doses of glucocorticoids is well known. Previously, there has been no satisfactory quantitative model describing the kinetics of calcium flow in subjects on chronic steroid use. A mathematical model of calcium isotope interaction with bone is described and applied to determine an estimate of kinetic parameters characterizing these changes. Calcium tracer dilution kinetics after a bolus injection of 42Ca were measured in 14 subjects with juvenile dermatomyositis, 6 on prednisone regimens and 8 on treatment regimens without prednisone. Irreversible tracer loss from plasma bone is found to be significantly reduced (P = 0.043) in the glucocorticoid-treated patients compared with patients on nonsteroid regimens. Reversible flow to bone is noted to be similar in the two groups. These results suggest a direct effect of glucocorticoids on osteoblast function.

The mechanism of ureido-pyrimidinone:2,7-diamido-naphthyridine complexation and the presence of kinetically controlled pathways in multicomponent hydrogen-bonded systems.

PubMed

de Greef, Tom F A; Ligthart, G B W L; Lutz, Martin; Spek, Anthony L; Meijer, E W; Sijbesma, Rint P

2008-04-23

The kinetics of association of ureido-pyrimidinone (U) dimers, present either in the 4[1H]-keto form or in the pyrimidin-4-ol form, with 2,7-diamido-1,8-naphthyridine (N) into a complementary heterodimer have been investigated. The formation of heterodimers with 2,7-diamido-1,8-naphthyridine from pyrimidin-4-ol dimers is much faster than from 4[1H]-pyrimidinone dimers. Using a combination of simple measurements and simulations, evidence for a bimolecular tautomerization step is presented. Finally, the acquired kinetic knowledge of the different pathways leading from ureido-pyrimidinone homodimers to ureido-pyrimidinone:diamido-naphthyridine (U:N) heterodimers allows the prediction and observation of kinetically determined ureido-pyrimidinone heterodimers which slowly convert back to the corresponding homodimers.

Methodologies for extracting kinetic constants for multiphase reacting flow simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, S.L.; Lottes, S.A.; Golchert, B.

1997-03-01

Flows in industrial reactors often involve complex reactions of many species. A computational fluid dynamics (CFD) computer code, ICRKFLO, was developed to simulate multiphase, multi-species reacting flows. The ICRKFLO uses a hybrid technique to calculate species concentration and reaction for a large number of species in a reacting flow. This technique includes a hydrodynamic and reacting flow simulation with a small but sufficient number of lumped reactions to compute flow field properties followed by a calculation of local reaction kinetics and transport of many subspecies (order of 10 to 100). Kinetic rate constants of the numerous subspecies chemical reactions aremore » difficult to determine. A methodology has been developed to extract kinetic constants from experimental data efficiently. A flow simulation of a fluid catalytic cracking (FCC) riser was successfully used to demonstrate this methodology.« less

Data Acquisition Systems

NASA Technical Reports Server (NTRS)

1994-01-01

In the mid-1980s, Kinetic Systems and Langley Research Center determined that high speed CAMAC (Computer Automated Measurement and Control) data acquisition systems could significantly improve Langley's ARTS (Advanced Real Time Simulation) system. The ARTS system supports flight simulation R&D, and the CAMAC equipment allowed 32 high performance simulators to be controlled by centrally located host computers. This technology broadened Kinetic Systems' capabilities and led to several commercial applications. One of them is General Atomics' fusion research program. Kinetic Systems equipment allows tokamak data to be acquired four to 15 times more rapidly. Ford Motor company uses the same technology to control and monitor transmission testing facilities.

First kinetic discrimination between carbon and oxygen reactivity of enols.

PubMed

García-Río, Luis; Mejuto, Juan C; Parajó, Mercedes; Pérez-Lorenzo, Moisés

2008-11-07

Nitrosation of enols shows a well-differentiated behavior depending on whether the reaction proceeds through the carbon (nucleophilic catalysis is observed) or the oxygen atom (general acid-base catalysis is observed). This is due to the different operating mechanisms for C- and O-nitrosation. Nitrosation of acetylacetone (AcAc) shows a simultaneous nucleophilic and acid-base catalysis. This simultaneous catalysis constitutes the first kinetic evidence of two independent reactions on the carbon and oxygen atom of an enol. The following kinetic study allows us to determine the rate constants for both reaction pathways. A similar reactivity of the nucleophilic centers with the nitrosonium ion is observed.

Dehydration of detomidine hydrochloride monohydrate.

PubMed

Veldre, K; Actiņš, A; Jaunbergs, J

2011-10-09

The thermodynamic stability of detomidine hydrochloride monohydrate has been evaluated on the basis of phase transition kinetics in solid state. A method free of empirical models was used for the treatment of kinetic data, and compared to several known solid state kinetic data processing methods. Phase transitions were monitored by powder X-ray diffraction (PXRD) and thermal analysis. Full PXRD profiles were used for determining the phase content instead of single reflex intensity measurements, in order to minimize the influence of particle texture. We compared the applicability of isothermal and nonisothermal methods to our investigation of detomidine hydrochlorine monohydrate dehydration. Copyright © 2011 Elsevier B.V. All rights reserved.

Influence of oxalic acid on the dissolution kinetics of manganese oxide

NASA Astrophysics Data System (ADS)

Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

2012-11-01

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.

Theoretical study of gas hydrate decomposition kinetics: model predictions.

PubMed

Windmeier, Christoph; Oellrich, Lothar R

2013-11-27

In order to provide an estimate of intrinsic gas hydrate dissolution and dissociation kinetics, the Consecutive Desorption and Melting Model (CDM) was developed in a previous publication (Windmeier, C.; Oellrich, L. R. J. Phys. Chem. A 2013, 117, 10151-10161). In this work, an extensive summary of required model data is given. Obtained model predictions are discussed with respect to their temperature dependence as well as their significance for technically relevant areas of gas hydrate decomposition. As a result, an expression for determination of the intrinsic gas hydrate decomposition kinetics for various hydrate formers is given together with an estimate for the maximum possible rates of gas hydrate decomposition.

In situ synchrotron investigation of grain growth behavior of nano-grained UO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yinbin; Yao, Tiankai; Lian, Jie

Here, we report on the study of grain growth kinetics in nano-grained UO 2 samples. Dense nano-grained UO 2 samples with well-controlled stoichiometry and grain size were fabricated using the spark plasma sintering technique. To determine the grain growth kinetics at elevated temperatures, a synchrotron wide-angle X-ray scattering (WAXS) study was performed in situ to measure the real-time grain size evolution based on the modified Williamson-Hall analysis. The unique grain growth kinetics of nanocrystalline UO 2 at 730 °C and 820 °C were observed and explained by the difference in mobility of various grain boundaries.

In situ synchrotron investigation of grain growth behavior of nano-grained UO 2

DOE PAGES

Miao, Yinbin; Yao, Tiankai; Lian, Jie; ...

2017-01-09

Here, we report on the study of grain growth kinetics in nano-grained UO 2 samples. Dense nano-grained UO 2 samples with well-controlled stoichiometry and grain size were fabricated using the spark plasma sintering technique. To determine the grain growth kinetics at elevated temperatures, a synchrotron wide-angle X-ray scattering (WAXS) study was performed in situ to measure the real-time grain size evolution based on the modified Williamson-Hall analysis. The unique grain growth kinetics of nanocrystalline UO 2 at 730 °C and 820 °C were observed and explained by the difference in mobility of various grain boundaries.

[The accuracy of rapid equilibrium assumption in steady-state enzyme kinetics is the function of equilibrium segment structure and properties].

PubMed

Vrzheshch, P V

2015-01-01

Quantitative evaluation of the accuracy of the rapid equilibrium assumption in the steady-state enzyme kinetics was obtained for an arbitrary mechanism of an enzyme-catalyzed reaction. This evaluation depends only on the structure and properties of the equilibrium segment, but doesn't depend on the structure and properties of the rest (stationary part) of the kinetic scheme. The smaller the values of the edges leaving equilibrium segment in relation to values of the edges within the equilibrium segment, the higher the accuracy of determination of intermediate concentrations and reaction velocity in a case of the rapid equilibrium assumption.

The kinetic friction of ZnO nanowires on amorphous SiO2 and SiN substrates

NASA Astrophysics Data System (ADS)

Roy, Aditi; Xie, Hongtao; Wang, Shiliang; Huang, Han

2016-12-01

ZnO nanowires were bent on amorphous SiO2 and SiN substrates in an ambient atmosphere using optical nanomanipulation. The kinetic friction between the nanowires and substrate was determined from the bent shape of the nanowires. The kinetic friction force per unit area, i.e. frictional shear stress, for the ZnO/SiO2 and ZnO/SiN nanowire/substrate systems being measured were 1.05 ± 0.28 and 2.08 ± 0.33 MPa, respectively. The surface roughness and the Hamaker constant of SiO2 and SiN substrates had significant effect on the frictional stresses.

Navigating ligand protein binding free energy landscapes: universality and diversity of protein folding and molecular recognition mechanisms

NASA Astrophysics Data System (ADS)

Verkhivker, Gennady M.; Rejto, Paul A.; Bouzida, Djamal; Arthurs, Sandra; Colson, Anthony B.; Freer, Stephan T.; Gehlhaar, Daniel K.; Larson, Veda; Luty, Brock A.; Marrone, Tami; Rose, Peter W.

2001-03-01

Thermodynamic and kinetic aspects of ligand-protein binding are studied for the methotrexate-dihydrofolate reductase system from the binding free energy profile constructed as a function of the order parameter. Thermodynamic stability of the native complex and a cooperative transition to the unique native structure suggest the nucleation kinetic mechanism at the equilibrium transition temperature. Structural properties of the transition state ensemble and the ensemble of nucleation conformations are determined by kinetic simulations of the transmission coefficient and ligand-protein association pathways. Structural analysis of the transition states and the nucleation conformations reconciles different views on the nucleation mechanism in protein folding.

qPIPSA: Relating enzymatic kinetic parameters and interaction fields

PubMed Central

Gabdoulline, Razif R; Stein, Matthias; Wade, Rebecca C

2007-01-01

Background The simulation of metabolic networks in quantitative systems biology requires the assignment of enzymatic kinetic parameters. Experimentally determined values are often not available and therefore computational methods to estimate these parameters are needed. It is possible to use the three-dimensional structure of an enzyme to perform simulations of a reaction and derive kinetic parameters. However, this is computationally demanding and requires detailed knowledge of the enzyme mechanism. We have therefore sought to develop a general, simple and computationally efficient procedure to relate protein structural information to enzymatic kinetic parameters that allows consistency between the kinetic and structural information to be checked and estimation of kinetic constants for structurally and mechanistically similar enzymes. Results We describe qPIPSA: quantitative Protein Interaction Property Similarity Analysis. In this analysis, molecular interaction fields, for example, electrostatic potentials, are computed from the enzyme structures. Differences in molecular interaction fields between enzymes are then related to the ratios of their kinetic parameters. This procedure can be used to estimate unknown kinetic parameters when enzyme structural information is available and kinetic parameters have been measured for related enzymes or were obtained under different conditions. The detailed interaction of the enzyme with substrate or cofactors is not modeled and is assumed to be similar for all the proteins compared. The protein structure modeling protocol employed ensures that differences between models reflect genuine differences between the protein sequences, rather than random fluctuations in protein structure. Conclusion Provided that the experimental conditions and the protein structural models refer to the same protein state or conformation, correlations between interaction fields and kinetic parameters can be established for sets of related enzymes. Outliers may arise due to variation in the importance of different contributions to the kinetic parameters, such as protein stability and conformational changes. The qPIPSA approach can assist in the validation as well as estimation of kinetic parameters, and provide insights into enzyme mechanism. PMID:17919319

Single-Molecule Imaging of RNA Splicing in Live Cells.

PubMed

Rino, José; Martin, Robert M; Carvalho, Célia; de Jesus, Ana C; Carmo-Fonseca, Maria

2015-01-01

Expression of genetic information in eukaryotes involves a series of interconnected processes that ultimately determine the quality and amount of proteins in the cell. Many individual steps in gene expression are kinetically coupled, but tools are lacking to determine how temporal relationships between chemical reactions contribute to the output of the final gene product. Here, we describe a strategy that permits direct measurements of intron dynamics in single pre-mRNA molecules in live cells. This approach reveals that splicing can occur much faster than previously proposed and opens new avenues for studying how kinetic mechanisms impact on RNA biogenesis. © 2015 Elsevier Inc. All rights reserved.

Evaluation of pulsed streamer corona experiments to determine the O* radical yield

NASA Astrophysics Data System (ADS)

van Heesch, E. J. M.; Winands, G. J. J.; Pemen, A. J. M.

2008-12-01

The production of O* radicals in air by a pulsed streamer plasma is studied by integration of a large set of precise experimental data and the chemical kinetics of ozone production. The measured data comprise ozone production, plasma energy, streamer volume, streamer length, streamer velocity, humidity and gas-flow rate. Instead of entering input parameters into a kinetic model to calculate the end products the opposite strategy is followed. Since the amount of end-products (ozone) is known from the measurements the model had to be applied in the reverse direction to determine the input parameters, i.e. the O* radical concentration.

Hip joint kinetics in the table tennis topspin forehand: relationship to racket velocity.

PubMed

Iino, Yoichi

2018-04-01

The purpose of this study was to determine hip joint kinetics during a table tennis topspin forehand, and to investigate the relationship between the relevant kinematic and kinetic variables and the racket horizontal and vertical velocities at ball impact. Eighteen male advanced table tennis players hit cross-court topspin forehands against backspin balls. The hip joint torque and force components around the pelvis coordinate system were determined using inverse dynamics. Furthermore, the work done on the pelvis by these components was also determined. The peak pelvis axial rotation velocity and the work done by the playing side hip pelvis axial rotation torque were positively related to the racket horizontal velocity at impact. The sum of the work done on the pelvis by the backward tilt torques and the upward joint forces was positively related to the racket vertical velocity at impact. The results suggest that the playing side hip pelvis axial rotation torque exertion is important for acquiring a high racket horizontal velocity at impact. The pelvis backward tilt torques and upward joint forces at both hip joints collectively contribute to the generation of the racket vertical velocity, and the mechanism for acquiring the vertical velocity may vary among players.

Modelling nifedipine photodegradation, photostability and actinometric properties.

PubMed

Maafi, Wassila; Maafi, Mounir

2013-11-01

The photodegradation of drugs obeying unimolecular mechanisms such as that of nifedipine (NIF) were usually characterised in the literature by zero-, first- and second-order kinetics. This approach has been met with varying success. This paper addresses this issue and proposes a novel approach for unimolecular photodegradation kinetics. The photodegradation of the cardiovascular drug nifedipine is investigated within this framework. Experimental kinetic data of nifedipine photodegradation were obtained by continuous monochromatic irradiation and DAD analysis. Fourth-order Runge-Kutta calculated kinetic data served for the validation of the new semi-empirical integrated rate-law model proposed in this study. A new model equation has been developed and proposed which faithfully describes the kinetic behaviour of NIF in solution for non-isosbestic irradiations at wavelengths where both NIF and its photoproduct absorb. NIF absolute quantum yield values were determined and found to increase with irradiation wavelength according to a defined sigmoid relationship. The effects of increasing NIF or excipients' concentrations on NIF kinetics were successfully modelled and found to improve NIF photostability. The potential of NIF for actinometry has been explored and evaluated. A new reaction order (the so-called Φ-order) has been identified and specifically proposed for unimolecular photodegradation reactions. The semi-empirical and integrated rate-law models facilitated reliable kinetic studies of NIF photodegradation as an example of AB(1Φ) unimolecular reactions. It allowed filling a gap in kinetic studies of drugs since, thus far, thermal first-order or a combination of first- and zero- order kinetic equations were generally applied for drug photoreactions in the literature. Also, a new reaction order, the "Φ-order", has been evidenced and proposed as a specific alternative for photodegradation kinetics. Copyright © 2013 Elsevier B.V. All rights reserved.

Simultaneous spectrophotometric determination of paracetamol and salicylamide in human serum and pharmaceutical formulations by a differential kinetic method.

PubMed

Zarei, Ali Reza; Afkhami, Abbas; Sarlak, Nahid

2005-01-01

A rapid, simple, and sensitive differential kinetic method is presented for the determinations of acetaminophen (also known as paracetamol) and salicylamide. The method is based on their oxidation reaction by Fe3+ ion in the presence of 1, 10-phenanthroline as indicator. The reactions can be monitored spectrophotometrically by measuring the increase in the absorbance of the solution at 510 nm. Two times were selected one in which only paracetamol is oxidized by Fe3+ ion and the other in which both drugs are oxidized by Fe3+ ion. The data were evaluated by the proportional equations method. The method allowed the simultaneous determination of paracetamol and salicylamide at concentrations between 0.5-20 and 1-40 microg/mL with relative standard deviations of 3.47 and 2.58%, respectively. The method was applied to the simultaneous determination of paracetamol and salicylamide in human serum and pharmaceutical formulations.

A kinetic method for the determination of thiourea by its catalytic effect in micellar media

NASA Astrophysics Data System (ADS)

Abbasi, Shahryar; Khani, Hossein; Gholivand, Mohammad Bagher; Naghipour, Ali; Farmany, Abbas; Abbasi, Freshteh

2009-03-01

A highly sensitive, selective and simple kinetic method was developed for the determination of trace levels of thiourea based on its catalytic effect on the oxidation of janus green in phosphoric acid media and presence of Triton X-100 surfactant without any separation and pre-concentration steps. The reaction was monitored spectrophotometrically by tracing the formation of the green-colored oxidized product of janus green at 617 nm within 15 min of mixing the reagents. The effect of some factors on the reaction speed was investigated. Following the recommended procedure, thiourea could be determined with linear calibration graph in 0.03-10.00 μg/ml range. The detection limit of the proposed method is 0.02 μg/ml. Most of foreign species do not interfere with the determination. The high sensitivity and selectivity of the proposed method allowed its successful application to fruit juice and industrial waste water.

Micelle Morphology and Mechanical Response of Triblock Gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seitz, Michelle E.; Burghardt, Wesley R.; Shull, Kenneth R.

2010-01-12

The effect of polymer concentration on mechanical response and micelle morphology of ABA and AB copolymers in B-selective solvents has been systematically studied. Micelle morphology was determined using a combination of small-angle X-ray scattering, shear, and birefringence while mechanical response at low and high strains was determined using indentation techniques. Self-consistent field theory calculations were used to determine micelle volume fraction profiles and to construct an equilibrium phase map. The transition from spherical to cylindrical micelles increases the triblock gel modulus and energy dissipation. Combining knowledge of gel relaxation time, which determines the rate at which the gel can equilibratemore » its micelle structure, with the equilibrium phase map allows estimation of the experimental temperatures and time scales over which kinetic trapping will arrest micelle structure evolution. Kinetic trapping enables cylindrical morphologies to be obtained at significantly lower polymer fractions than is possible in equilibrated systems.« less

On the equilibrium between proton kappa distribution and compressible kinetic Alfvenic fluctuations

NASA Astrophysics Data System (ADS)

Yoon, P. H.

2017-12-01

Protons with a quasi inverse power law energetic population featuring the property f v-α, with α close to 5, are pervasively observed in the heliosphere. While many theoretical attempts have been made in order to describe such a feature, the so-called pump acceleration mechanism put forth by Fisk & Gloeckler is one of the most prominent theories. Their mechanism involves the low-frequency compressional fluctuations accelerating the protons. This presentation aims to reformulate the problem from the perspective of the steady state solution of the self-consistent plasma kinetic theory involving compressible kinetic Alfvenic fluctuations. By considering the steady state proton particle kinetic equation and quasi-linear wave kinetic for the kinetic Alfvenic turbulence we seek to obtain concomitant solutions for both proton velocity distribution function and the spectral intensity for kinetic Alfvenic fluctuation. It is found that the kappa distribution for the protons is a legitimate, if not unique, solution. The steady state spectrum of kinetic Alfvenic fluctuation is also obtained. The present investigation demonstrates that the kappa distribution for the protons featuring energetic tail population characterized by f v-2κ-2, where κ is the parameter for kappa distribution, may represent the background population of the protons in the heliosphere. However, it is speculated that in order to uniquely determine the value of κ, which must be close to 1.5 for asymptotic behavior of f v-5, one must have an additional constraint that involves the balance of nonlinear mode coupling terms in the wave kinetic equation.

Energy dynamics and current sheet structure in fluid and kinetic simulations of decaying magnetohydrodynamic turbulence

DOE PAGES

Makwana, K. D.; Zhdankin, V.; Li, H.; ...

2015-04-10

We performed simulations of decaying magnetohydrodynamic (MHD) turbulence with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k-1.3⊥k⊥-1.3. The kinetic code shows a spectral slope of k-1.5⊥k⊥-1.5 for smallermore » simulation domain, and k-1.3⊥k⊥-1.3 for larger domain. We then estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. Finally, this work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.« less

Energy dynamics and current sheet structure in fluid and kinetic simulations of decaying magnetohydrodynamic turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makwana, K. D.; Zhdankin, V.; Li, H.

We performed simulations of decaying magnetohydrodynamic (MHD) turbulence with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k-1.3⊥k⊥-1.3. The kinetic code shows a spectral slope of k-1.5⊥k⊥-1.5 for smallermore » simulation domain, and k-1.3⊥k⊥-1.3 for larger domain. We then estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. Finally, this work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.« less

Development of high performance particle in cell code for the exascale age

NASA Astrophysics Data System (ADS)

Lapenta, Giovanni; Amaya, Jorge; Gonzalez, Diego; Deep-Est H2020 Consortium Collaboration

2017-10-01

Magnetized plasmas are most effectively described by magneto-hydrodynamics, MHD, a fluid theory based on describing some fields defined in space: electromagnetic fields, density, velocity and temperature of the plasma. However, microphysics processes need kinetic theory, where statistical distributions of particles are governed by the Boltzmann equation. While fluid models are based on the ordinary space and time, kinetic models require a six dimensional space, called phase space, besides time. The two methods are not separated but rather interact to determine the system evolution. Arriving at a single self-consistent model is the goal of our research. We present a new approach developed with the goal of extending the reach of kinetic models to the fluid scales. Kinetic models are a higher order description and all fluid effects are included in them. However, the cost in terms of computing power is much higher and it has been so far prohibitively expensive to treat space weather events fully kinetically. We have now designed a new method capable of reducing that cost by several orders of magnitude making it possible for kinetic models to study macroscopic systems. H2020 Deep-EST consortium (European Commission).

Kinetics of human immunodeficiency virus budding and assembly

NASA Astrophysics Data System (ADS)

Zhang, Rui; Nguyen, Toan

2009-03-01

Human immunodeficiency virus (HIV) belongs to a large family of RNA viruses, retroviruses. Unlike budding of regular enveloped viruses, retroviruses bud concurrently with the assembly of retroviral capsids on the cell membrane. The kinetics of HIV (and other retroviruses) budding and assembly is therefore strongly affected by the elastic energy of the membrane and fundamentally different from regular viruses. The main result of this work shows that the kinetics is tunable from a fast budding process to a slow and effectively trapped partial budding process, by varying the attractive energy of retroviral proteins (call Gags), relative to the membrane elastic energy. When the Gag-Gag attraction is relatively high, the membrane elastic energy provides a kinetic barrier for the two pieces of the partial capsids to merge. This energy barrier determines the slowest step in the kinetics and the budding time. In the opposite limit, the membrane elastic energy provides not only a kinetic energy barrier, but a free energy barrier. The budding and assembly is effectively trapped at local free energy minimum, corresponding to a partially budded state. The time scale to escape from this metastable state is exponentially large. In both cases, our result fit with experimental measurements pretty well.

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

NASA Technical Reports Server (NTRS)

Raj. Sai V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 +/- 9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

NASA Technical Reports Server (NTRS)

Raj. Sai V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

NASA Technical Reports Server (NTRS)

Raj, S. V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Energy landscapes, folding mechanisms, and kinetics of RNA tetraloop hairpins.

PubMed

Chakraborty, Debayan; Collepardo-Guevara, Rosana; Wales, David J

2014-12-31

RNA hairpins play a pivotal role in a diverse range of cellular functions, and are integral components of ribozymes, mRNA, and riboswitches. However, the mechanistic and kinetic details of RNA hairpin folding, which are key determinants of most of its biological functions, are poorly understood. In this work, we use the discrete path sampling (DPS) approach to explore the energy landscapes of two RNA tetraloop hairpins, and provide insights into their folding mechanisms and kinetics in atomistic detail. Our results show that the potential energy landscapes have a distinct funnel-like bias toward the folded hairpin state, consistent with efficient structure-seeking properties. Mechanistic and kinetic information is analyzed in terms of kinetic transition networks. We find microsecond folding times, consistent with temperature jump experiments, for hairpin folding initiated from relatively compact unfolded states. This process is essentially driven by an initial collapse, followed by rapid zippering of the helix stem in the final phase. Much lower folding rates are predicted when the folding is initiated from extended chains, which undergo longer excursions on the energy landscape before nucleation events can occur. Our work therefore explains recent experiments and coarse-grained simulations, where the folding kinetics exhibit precisely this dependency on the initial conditions.

Kinetic Roughening Transition and Energetics of Tetragonal Lysozyme Crystal Growth

NASA Technical Reports Server (NTRS)

Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

2004-01-01

Interpretation of lysozyme crystal growth rates using well-established physical theories enabled the discovery of a phenomenon possibly indicative of kinetic roughening. For example, lysozyme crystals grown above a critical supersaturation sigma, (where supersaturation sigma = ln c/c(sub eq), c = the protein concentration and c(sub eq) = the solubility concentration) exhibit microscopically rough surfaces due to the continuous addition of growth units anywhere on the surface of a crystal. The rate of crystal growth, V(sub c), for the continuous growth process is determined by the continuous flux of macromolecules onto a unit area of the crystal surface, a, from a distance, xi, per unit time due to diffusion, and a probability of attachment onto the crystal surface, expressed. Based upon models applied, the energetics of lysozyme crystal growth was determined. The magnitudes of the energy barriers of crystal growth for both the (110) and (101) faces of tetragonal lysozyme crystals are compared. Finally, evidence supportive of the kinetic roughening hypothesis is presented.

Real-time reliable determination of binding kinetics of DNA hybridization using a multi-channel graphene biosensor

NASA Astrophysics Data System (ADS)

Xu, Shicai; Zhan, Jian; Man, Baoyuan; Jiang, Shouzhen; Yue, Weiwei; Gao, Shoubao; Guo, Chengang; Liu, Hanping; Li, Zhenhua; Wang, Jihua; Zhou, Yaoqi

2017-03-01

Reliable determination of binding kinetics and affinity of DNA hybridization and single-base mismatches plays an essential role in systems biology, personalized and precision medicine. The standard tools are optical-based sensors that are difficult to operate in low cost and to miniaturize for high-throughput measurement. Biosensors based on nanowire field-effect transistors have been developed, but reliable and cost-effective fabrication remains a challenge. Here, we demonstrate that a graphene single-crystal domain patterned into multiple channels can measure time- and concentration-dependent DNA hybridization kinetics and affinity reliably and sensitively, with a detection limit of 10 pM for DNA. It can distinguish single-base mutations quantitatively in real time. An analytical model is developed to estimate probe density, efficiency of hybridization and the maximum sensor response. The results suggest a promising future for cost-effective, high-throughput screening of drug candidates, genetic variations and disease biomarkers by using an integrated, miniaturized, all-electrical multiplexed, graphene-based DNA array.

Novel laser gain and time-resolved FTIR studies of photochemistry

NASA Technical Reports Server (NTRS)

Leone, Stephen R.

1990-01-01

Several techniques are discussed which can be used to explore laboratory photochemical processes and kinetics relevant to planetary atmospheres; these include time-resolved laser gain-versus-absorption spectroscopy and time-resolved Fourier transform infrared (FTIR) emission studies. The laser gain-versus-absorption method employed tunable diode and F-center lasers to determine the yields of excited photofragments and their kinetics. The time-resolved FTIR technique synchronizes the sweep of a commercial FTIR with a pulsed source of light to obtain emission spectra of novel transient species in the infrared. These methods are presently being employed to investigate molecular photodissociation, the yields of excited states of fragments, their subsequent reaction kinetics, Doppler velocity distributions, and velocity-changing collisions of translationally fast atoms. Such techniques may be employed in future investigations of planetary atmospheres, for example to study polycyclic aromatic hydrocarbons related to cometary emissions, to analyze acetylene decomposition products and reactions, and to determine spectral features in the near infrared and infrared wavelength regions for planetary molecules and clusters.

Investigation of the first-order phase transition kinetics using the method of pulsed photothermal surface deformation: radial measurements

NASA Astrophysics Data System (ADS)

Vintzentz, S. V.; Sandomirsky, V. B.

1992-09-01

An extension of the photothermal surface deformation (PTSD) method to study the macroscopic kinetics of the first-order phase transition (PTr) is given. The movement of the phase interface (PI) over a surface with a PTr locally induced in the subsurface volume by a focused laser pulse is investigated for the first time using radial measurements of the PTSD kinetics. For the known metal-to-semiconductor PTr in VO 2 (a good model system) a procedure is suggested for measuring the maximum size rsm of the "hot" (metal) phase on the surface (a parameter most difficult to determine) as well as for estimating the velocity of the PI movement over the surface, vs, and in the bulk, vb. Besides, it is shown that the PTSD method may be used to determine the "local" threshold energy E0 needed for the laser-induced PTr and the "local" latent heat L of the PTr. This demonstrates the feasibility of scanning surface E0- and L-microscopy.

Parametric Investigation of the Isothermal Kinetics of Growth of Graphene on a Nickel Catalyst in the Process of Chemical Vapor Deposition of Hydrocarbons

NASA Astrophysics Data System (ADS)

Futko, S. I.; Shulitskii, B. G.; Labunov, V. A.; Ermolaeva, E. M.

2016-11-01

A kinetic model of isothermal synthesis of multilayer graphene on the surface of a nickel foil in the process of chemical vapor deposition, on it, of hydrocarbons supplied in the pulsed regime is considered. The dependences of the number of graphene layers formed and the time of their growth on the temperature of the process, the concentration of acetylene, and the thickness of the nickel foil were calculated. The regime parameters of the process of chemical vapor deposition, at which single-layer graphene and bi-layer graphene are formed, were determined. The dynamics of growth of graphene domains at chemical-vapor-deposition parameters changing in wide ranges was investigated. It is shown that the time dependences of the rates of growth of single-layer graphene and bi-layer graphene are nonlinear in character and that they are determined by the kinetics of nucleation and growth of graphene and the diffusion flow of carbon atoms in the nickel foil.

Oxidation of trimethoprim by ferrate(VI): kinetics, products, and antibacterial activity.

PubMed

Anquandah, George A K; Sharma, Virender K; Knight, D Andrew; Batchu, Sudha Rani; Gardinali, Piero R

2011-12-15

Kinetics, stoichiometry, and products of the oxidation of trimethoprim (TMP), one of the most commonly detected antibacterial agents in surface waters and municipal wastewaters, by ferrate(VI) (Fe(VI)) were determined. The pH dependent second-order rate constants of the reactions of Fe(VI) with TMP were examined using acid-base properties of Fe(VI) and TMP. The kinetics of reactions of diaminopyrimidine (DAP) and trimethoxytoluene (TMT) with Fe(VI) were also determined to understand the reactivity of Fe(VI) with TMP. Oxidation products of the reactions of Fe(VI) with TMP and DAP were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Reaction pathways of oxidation of TMP by Fe(VI) are proposed to demonstrate the cleavage of the TMP molecule to ultimately result in 3,4,5,-trimethoxybenzaldehyde and 2,4-dinitropyrimidine as among the final identified products. The oxidized products mixture exhibited no antibacterial activity against E. coli after complete consumption of TMP. Removal of TMP in the secondary effluent by Fe(VI) was achieved.

Irreversible thermodynamics of Poisson processes with reaction.

PubMed

Méndez, V; Fort, J

1999-11-01

A kinetic model is derived to study the successive movements of particles, described by a Poisson process, as well as their generation. The irreversible thermodynamics of this system is also studied from the kinetic model. This makes it possible to evaluate the differences between thermodynamical quantities computed exactly and up to second-order. Such differences determine the range of validity of the second-order approximation to extended irreversible thermodynamics.

Nanointerface-driven reversible hydrogen storage in the nanoconfined Li-N-H system

DOE PAGES

Wood, Brandon C.; Stavila, Vitalie; Poonyayant, Natchapol; ...

2017-01-20

Internal interfaces in the Li 3N/[LiNH 2 + 2LiH] solid-state hydrogen storage system alter the hydrogenation and dehydrogenation reaction pathways upon nanosizing, suppressing undesirable intermediate phases to dramatically improve kinetics and reversibility. Finally, the key role of solid interfaces in determining thermodynamics and kinetics suggests a new paradigm for optimizing complex hydrides for solid-state hydrogen storage by engineering internal microstructure.

Simplified half-life methods for the analysis of kinetic data

NASA Technical Reports Server (NTRS)

Eberhart, J. G.; Levin, E.

1988-01-01

The analysis of reaction rate data has as its goal the determination of the order rate constant which characterize the data. Chemical reactions with one reactant and present simplified methods for accomplishing this goal are considered. The approaches presented involve the use of half lives or other fractional lives. These methods are particularly useful for the more elementary discussions of kinetics found in general and physical chemistry courses.

The Kinetics of Bainitic Transformation of Roll Steel 75Kh3MF

NASA Astrophysics Data System (ADS)

Kletsova, O. A.; Krylova, S. E.; Priymak, E. Yu.; Gryzunov, V. I.; Kamantsev, S. V.

2018-01-01

The critical points of steel 75Kh3MF and the temperature of the start of martensitic transformation are determined by a dilatometric method. The thermokinetic and isothermal diagrams of decomposition of supercooled austenite are plotted. The microstructure and microhardness of steel specimens cooled at different rates are studied. The kinetics of the occurrence of bainitic transformation in the steel is calculated using the Austin-Ricket equation.

A Microscale Approach to Chemical Kinetics in the General Chemistry Laboratory: The Potassium Iodide Hydrogen Peroxide Iodine-Clock Reaction

ERIC Educational Resources Information Center

Sattsangi, Prem D.

2011-01-01

A microscale laboratory for teaching chemical kinetics utilizing the iodine clock reaction is described. Plastic pipets, 3 mL volume, are used to store and deliver precise drops of reagents and the reaction is run in a 24 well plastic tray using a total 60 drops of reagents. With this procedure, students determine the rate of reaction and the…

Lignin transformations and reactivity upon ozonation in aqueous media

NASA Astrophysics Data System (ADS)

Khudoshin, A. G.; Mitrofanova, A. N.; Lunin, V. V.

2012-03-01

The reaction of ozone with lignin in aqueous acidic solutions is investigated. The Danckwerst model is used to describe the kinetics of gas/liquid processes occurring in a bubble reactor. The efficient ozonation rate of a soluble lignin analog, sodium lignosulfate, is determined. The main lines of the reaction between ozone and lignin are revealed on the basis of kinetic analysis results and IR and UV spectroscopy data.

Determination of Dacarbazine Φ-Order Photokinetics, Quantum Yields, and Potential for Actinometry.

PubMed

Maafi, Mounir; Lee, Lok-Yan

2015-10-01

The characterization of drugs' photodegradation kinetics is more accurately achieved by means of the recently developed Φ-order kinetics than by the zero-, first-, and/or second-order classical treatments. The photodegradation of anti-cancer dacarbazine (DBZ) in ethanol has been investigated and found to obey Φ-order kinetics when subjected to continuous and monochromatic irradiation of various wavelengths. Its photochemical efficiency was proven to be wavelength dependent in the 220-350 nm range, undergoing a 50-fold increase. Albeit this variation was well defined by a sigmoid pattern, the overall photoreactivity of DBZ was proven to depend also on the contributions of reactants and experimental attributes. The usefulness of DBZ to serve as a drug-actinometer has been investigated using the mathematical framework of Φ-order kinetics. It has been shown that DBZ in ethanol can represent a good candidate for reliable actinometry in the range 270-350 nm. A detailed and easy-to-implement procedure has been proposed for DBZ actinometry. This procedure could advantageously be implemented prior to the determination of the photodegradation quantum yields. This approach might be found useful for the development of many drug actinometers as alternatives to quinine hydrochloride. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Rate-determining Step of Flap Endonuclease 1 (FEN1) Reflects a Kinetic Bias against Long Flaps and Trinucleotide Repeat Sequences.

PubMed

Tarantino, Mary E; Bilotti, Katharina; Huang, Ji; Delaney, Sarah

2015-08-21

Flap endonuclease 1 (FEN1) is a structure-specific nuclease responsible for removing 5'-flaps formed during Okazaki fragment maturation and long patch base excision repair. In this work, we use rapid quench flow techniques to examine the rates of 5'-flap removal on DNA substrates of varying length and sequence. Of particular interest are flaps containing trinucleotide repeats (TNR), which have been proposed to affect FEN1 activity and cause genetic instability. We report that FEN1 processes substrates containing flaps of 30 nucleotides or fewer at comparable single-turnover rates. However, for flaps longer than 30 nucleotides, FEN1 kinetically discriminates substrates based on flap length and flap sequence. In particular, FEN1 removes flaps containing TNR sequences at a rate slower than mixed sequence flaps of the same length. Furthermore, multiple-turnover kinetic analysis reveals that the rate-determining step of FEN1 switches as a function of flap length from product release to chemistry (or a step prior to chemistry). These results provide a kinetic perspective on the role of FEN1 in DNA replication and repair and contribute to our understanding of FEN1 in mediating genetic instability of TNR sequences. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.