Bulk Kinetics Research Articles

Oil-generation characteristics of Mesozoic syn-rift Madbi source rock in the Masila Basin, Eastern Yemen: New insights from kerogen pyrolysis and bulk kinetic modelling

Organic-rich shale layer is present within the syn-rift Madbi Formation of the Masila Basin, representing excellent oil source rock. Twenty-five representative immature to very early-mature source rock samples from the Upper Jurassic Madbi shale sequences were investigated using bulk and quantitative pyrolysis techniques. The analytical program included TOC, pyrolysis (SRA), pyrolysis GC, bulk kinetics, and kerogen microscopy. The results were used to characterize the kerogen composition and type of petroleum generated during thermal maturation from Madbi source rock and to clarify the variability of the organic matter and their effect on the timing of petroleum generation.Pyrolysis data identified two major organic facies with different petroleum generation characteristics; Type II kerogen with HI values of >400 mg HC/g TOC; Type II/III facies with HI values <400 mg HC/g TOC. This is supported by the abundant liptinitic materials (i.e., alginite, structureless (amorphous), and spores). Pyrolysis GC analysis on extracted rock samples show a dominance of a marine aliphatic-rich organic matter with variable contributions from transported terrestrial organic matter and proved to produce mainly paraffinic–naphthenic–aromatic oils with low wax contents.Bulk kinetic analysis on Madbi shale samples indicate that the Type II facies mostly derived from a homogenous organic matter, spans relatively narrow distribution of activation energy (50–54 kcal/mol) and predicted petroleum formation temperature is very different, with onset (TR 10%) temperatures of ∼125 °C (geological Tmax ∼138 °C). In contrast, the Type II/III facies reveals a relatively broad distribution of activation energies (40 kcal/mol to 62 kcal/mol) that are directly related to the heterogeneity in the organic matter, onset (TR 10%) temperatures of ∼106 °C (geological Tmax ∼139 °C). The bulk kinetic analysis also suggested that the peak generation temperatures (geological Tmax) are variable and ranging from 135 °C to 142 °C, reaching a significant transformation ratio (∼50% TR). Therefore, the Madbi source rock potential could have be generated and expelled mature oils in the Masila Basin.

Hydrocarbon Generation Kinetics of Lacustrine Yanchang Shale in Southeast Ordos Basin, North China

The upper Triassic Yanchang shale in Southeast Ordos Basin (SOB) is a main potential source rock for conventional petroleum fields and has been recently recognized as an important unconventional reservoir. Here, we report on the hydrocarbon potential of this lacustrine shale using bulk and quantitative pyrolysis techniques. The rock samples were taken from the Chang7 and Chang9 intervals of upper Triassic-aged cores. The analytical program included total organic carbon (TOC), Rock-Eval, pyrolysis gas chromatography (Py–GC), source rock analyzer (SRA), and microscale sealed vessel (MSSV) pyrolysis. Phase kinetic modeling was also employed on the basis of these data sets. The results were used to determine the petroleum-type organofacies, bulk hydrocarbon composition during maturation, bulk and compositional kinetics, and phase behavior of fluids generated in the Yanchang shales. The shales proved to contain type II2 kerogen with organic matter in high abundance and generate paraffinic–naphthenic–aromatic (...

Metal-induced crystallization of highly corrugated silicon thick films as potential anodes for Li-ion batteries.

Silicon has turned into one of the most promising anodes for high energy rechargeable Li-ion batteries. However, a huge volume expansion during alloying with Li always induces serious pulverization/delamination for microsized electrodes as well as undesired accumulation of solid electrolyte interphase (SEI). Many efforts have focused on various nanoengineering and binding strategies to construct integrated, robust ionic/electronic wiring networks but with a trade-off between active/inactive material ratio and performance retention. Here, we first apply a metal-induced crystallization (AIC) principle for immiscible metal/semiconductor systems (Si/Al bilayers in this work) to prepare microthick Si films consisting of a high density of isolated nanocolumns. This method furthermore brings about low temperature crystallization of initial amorphous Si and conformal coating of ion-conductive oxide to enhance the Li transport kinetics of bulk and interface. Both highly satisfactory capacity retention (1650 mAh/g after 500 cycles) and rate performance (∼1000 mAh/g at 8C) are achieved for such thick Si film anodes. This methodology can be used to prepare thick film samples with well-defined nanostructures but free of extra binder and conductive additives. It enables much higher area specific capacity than for inactive-component contained slurry samples and thin film samples. This postdeposition pore-creating can be extended to more alloying or conversion electrodes of thick films for high capacity Li/Na ion batteries.

Single Molecule Activity Measurements of Cytochrome P450 Oxidoreductase Reveal the Existence of Two Discrete Functional States

Electron transfer between membrane spanning oxidoreductase enzymes controls vital metabolic processes. Here we studied for the first time with single molecule resolution the function of P450 oxidoreductase (POR), the canonical membrane spanning activator of all microsomal cytochrome P450 enzymes. Measurements and statistical analysis of individual catalytic turnover cycles shows POR to sample at least two major functional states. This phenotype may underlie regulatory interactions with different cytochromes P450 but to date has remained masked in bulk kinetics. To ensure that we measured the inherent behavior of POR, we reconstituted the full length POR in "native like" membrane patches, nanodiscs. Nanodisc reconstitution increased stability by ∼2-fold as compared to detergent solubilized POR and showed significantly increased activity at biologically relevant ionic strength conditions, highlighting the importance of studying POR function in a membrane environment. This assay paves the way for studying the function of additional membrane spanning oxidoreductases with single molecule resolution.

Kinetics study of solid ammonia borane hydrogen release – modeling and experimental validation for chemical hydrogen storage

Ammonia borane (AB), NH3BH3, is a promising material for chemical hydrogen storage with 19.6 wt% gravimetric hydrogen capacity of which maximum 16.2 wt% hydrogen can be released via an exothermic thermal decomposition below 200 °C. We have investigated the kinetics of hydrogen release from AB and from an AB-methyl cellulose (AB/MC) composite at temperatures of 160-300 °C using both experiments and modeling. The hydrogen release rate at 300 °C is twice as fast as at 160 °C. The purpose of our study was to show safe hydrogen release without thermal runaway effects and to validate system model kinetics. AB/MC released hydrogen at ∼20 °C lower than neat AB and at a faster release rate in that temperature range. Based on the experimental results, the kinetics equations were revised to better represent the growth and nucleation process during decomposition of AB. We explored two different reactor concepts; auger and fixed bed. The current auger reactor concept turned out to not be appropriate, however, we demonstrated safe self-propagation of the hydrogen release reaction of solid AB/MC in a fixed bed reactor.

Molecular viewing of actin polymerizing actions and beyond: Combination analysis of single‐molecule speckle microscopy with modeling, FRAP and s‐FDAP (sequential fluorescence decay after photoactivation)

Live-cell single-molecule imaging is a powerful tool to elucidate the in vivo biochemistry of cytoskeletal proteins. However, it is often somewhat difficult to interpret how a bulk population of the observed molecule might behave as a whole. We review our recent studies in which the combination of image analysis with modeling and bulk kinetics measurements such as FRAP (fluorescence recovery after photobleaching) clarified basic problems in the regulation of actin remodeling pathways.

Kinetics of hydrogen sorption by palladium nanoparticles

The purpose of this communication is to compare the hydriding kinetics of bulk (250 μm) and nano-sized (3.6 nm) palladium particles. Sorption/desorption isotherms have been measured at 25 °C from volumetric experiments. It is shown that nano-particles retain only some of the characteristics of bulk systems. Several major differences such as different hydrogen solubility, different magnitude of hysteresis and different plateau pressure slopes have been observed. Hydrogen sorption/desorption kinetics has been analyzed in the frequency domain. A model has been used to fit experimental impedance diagrams and determine microscopic rate-parameters in the solid solution, two-phase domain and hydride phase. It is shown that microscopic rate parameters of micro- and nano-particles do not significantly differ.

Source rock characteristics and compositional kinetic models of Cretaceous organic rich black shales offshore southwestern Africa

The source rock potential of Cretaceous organic rich whole rock samples from deep sea drilling project (DSDP) wells offshore southwestern Africa was investigated using bulk and quantitative pyrolysis techniques. The sample material was taken from organic rich intervals of Aptian, Albian and Turonian aged core samples from DSDP site 364 offshore Angola, DSDP well 530A north of the Walvis Ridge offshore Namibia, and DSDP well 361 offshore South Africa. The analytical program included TOC, Rock-Eval, pyrolysis GC, bulk kinetics and micro-scale sealed vessel pyrolysis (MSSV) experiments. The results were used to determine differences in the source rock petroleum type organofacies, petroleum composition, gas/oil ratio (GOR) and pressure–volume–temperature (PVT) behavior of hydrocarbons generated from these black shales for petroleum system modeling purposes.The investigated Aptian and Albian organic rich shales proved to contain excellent quality marine kerogens. The highest source rock potential was identified in sapropelic shales in DSDP well 364, containing very homogeneous Type II and organic sulfur rich Type IIS kerogen. They generate P–N–A low wax oils and low GOR sulfur rich oils, whereas Type III kerogen rich silty sandstones of DSDP well 361 show a potential for gas/condensate generation. Bulk kinetic experiments on these samples indicate that the organic sulfur contents influence kerogen transformation rates, Type IIS kerogen being the least stable. South of the Walvis Ridge, the Turonian contains predominantly a Type III kerogen. North of the Walvis Ridge, the Turonian black shales contain Type II kerogen and have the potential to generate P–N–A low and high wax oils, the latter with a high GOR at high maturity.Our results provide the first compositional kinetic description of Cretaceous organic rich black shales, and demonstrate the excellent source rock potential, especially of the Aptian-aged source rock, that has been recognized in a number of the South Atlantic offshore basins.

Efficient and simultaneous generation of hematopoietic and vascular progenitors from human induced pluripotent stem cells

The hematopoietic and vascular lineages are intimately entwined as they arise together from bipotent hemangioblasts and hemogenic endothelial precursors during human embryonic development. In vitro differentiation of human pluripotent stem cells toward these lineages provides opportunities for elucidating the mechanisms of hematopoietic genesis. We previously demonstrated the stepwise in vitro differentiation of human embryonic stem cells (hESC) to definitive erythromyelopoiesis through clonogenic bipotent primitive hemangioblasts. This system recapitulates an orderly hematopoiesis similar to human yolk sac development via the generation of mesodermal-hematoendothelial progenitor cells that give rise to endothelium followed by embryonic primitive and definitive hematopoietic cells. Here, we report that under modified feeder-free endothelial culture conditions, multipotent CD34⁺ CD45⁺ hematopoietic progenitors arise in mass quantities from differentiated hESC and human induced pluripotent stem cells (hiPSC). These hematopoietic progenitors arose directly from adherent endothelial/stromal cell layers in a manner resembling in vivo hematopoiesis from embryonic hemogenic endothelium. Although fibroblast-derived hiPSC lines were previously found inefficient in hemato-endothelial differentiation capacity, our culture system also supported robust hiPSC hemato-vascular differentiation at levels comparable to hESC. We present comparative differentiation results for simultaneously generating hematopoietic and vascular progenitors from both hESC and fibroblast-hiPSC. This defined, optimized, and low-density differentiation system will be ideal for direct single-cell time course studies of the earliest hematopoietic events using time-lapse videography, or bulk kinetics using flow cytometry analyses on emerging hematopoietic progenitors.

Harvesting Murine Alveolar Macrophages and Evaluating Cellular Activation Induced by Polyanhydride Nanoparticles

Biodegradable nanoparticles have emerged as a versatile platform for the design and implementation of new intranasal vaccines against respiratory infectious diseases. Specifically, polyanhydride nanoparticles composed of the aliphatic sebacic acid (SA), the aromatic 1,6-bis(p-carboxyphenoxy)hexane (CPH), or the amphiphilic 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) display unique bulk and surface erosion kinetics and can be exploited to slowly release functional biomolecules (e.g., protein antigens, immunoglobulins, etc.) in vivo. These nanoparticles also possess intrinsic adjuvant activity, making them an excellent choice for a vaccine delivery platform. In order to elucidate the mechanisms governing the activation of innate immunity following intranasal mucosal vaccination, one must evaluate the molecular and cellular responses of the antigen presenting cells (APCs) responsible for initiating immune responses. Dendritic cells are the principal APCs found in conducting airways, while alveolar macrophages (AMɸ) predominate in the lung parenchyma. AMɸ are highly efficient in clearing the lungs of microbial pathogens and cell debris. In addition, this cell type plays a valuable role in the transport of microbial antigens to the draining lymph nodes, which is an important first step in the initiation of an adaptive immune response. AMɸ also express elevated levels of innate pattern recognition and scavenger receptors, secrete pro-inflammatory mediators, and prime naïve T cells. A relatively pure population of AMɸ (e.g., greater than 80%) can easily be obtained via lung lavage for study in the laboratory. Resident AMɸ harvested from immune competent animals provide a representative phenotype of the macrophages that will encounter the particle-based vaccine in vivo. Herein, we describe the protocols used to harvest and culture AMɸ from mice and examine the activation phenotype of the macrophages following treatment with polyanhydride nanoparticles in vitro.

Spatial confinement can lead to increased stability of amorphous indomethacin

The aim of this study was to investigate whether the physical stability of amorphous indomethacin can be improved by separating the drug material into small units by the use of microcontainers. Crystallisation from the spatially confined amorphous indomethacin in the microcontainers was determined and compared with the crystallisation kinetics of amorphous bulk indomethacin.Amorphous indomethacin in both a bulk form and contained within microcontainers was prepared by melting of bulk or container-incorporated γ-indomethacin, respectively, followed by quench-cooling. Microcontainers of three different sizes (diameters of 73μm, 174μm and 223μm) were used for the confinement of amorphous indomethacin, in order to elucidate whether the size of the microcontainer had an influence on the stability of the amorphous form. Following preparation, all samples were stored at 30°C and 23% RH. A sample of 100 microcontainers of each size was selected and measured on a Raman microscope over a period of 30days to ascertain whether the indomethacin in each container was amorphous or crystalline. Over time, a crystallisation number was obtained for the amorphous indomethacin in the microcontainers. The crystallisation numbers from the microcontainers were compared with the crystallisation kinetics of the amorphous bulk indomethacin, as determined by FT-Raman spectroscopy.Comparison of the numeric crystallisation in the microcontainers with the crystallisation kinetics of the amorphous bulk indomethacin showed that spatial confinement of indomethacin led to a significantly lower extent of crystallisation of the amorphous form. In the 174μm microcontainers, 29.0±2.6% of the amorphous indomethacin crystallised to the stable γ-form over a period of 30days, whilst 38.3±1.5% of the amorphous indomethacin crystallised in the 223μm microcontainers. Both these values were significantly different from that observed in the amorphous bulk indomethacin, where 51.0% crystallised to the γ-form after 30days. Comparing the 174 and 223μm microcontainers also revealed a significantly greater stabilising effect of the 174μm microcontainers (p-value of 0.0061).Surprisingly, for microcontainers with an inner diameter of 73μm, no stability improvement was found when compared to amorphous bulk indomethacin. It was observed that the amorphous indomethacin within these containers converted to the α-form of indomethacin (a metastable polymorph) which was unexpected at the storage conditions at 30°C and 23% RH.

Atomistic simulations of Au-silica nanocomposite film growth

The growth of Au-silica nanocomposite film is simulated in the framework of kinetic three dimensional lattice Monte Carlo simulations considering the basic phenomena in the deposition process. In case of co-sputter deposition, the growth kinetics of nanoparticles has been studied taking into consideration the effect of the energetic sputtered species reaching the surface of the film during deposition. Formation of Au nanorod like structures are predicted under certain growth conditions particularly when surface diffusion assisted phase separation plays the dominant role and bulk kinetics is frozen. The observed dependence of the Au nanoparticle size on Au/silica ratio is in agreement with the experimental results.

Dynamics of Exciton Relaxation in LH2 Antenna Probed by Multipulse Nonlinear Spectroscopy

We explain the relaxation dynamics in the LH2-B850 antenna as revealed by multipulse pump-dump-probe spectroscopy (Th. A. Cohen Stuart, M. Vengris, V. I. Novoderezhkin, R. J. Cogdell, C. N. Hunter, R. van Grondelle, submitted). The theory of pump-dump-probe response is evaluated using the doorway-window approach in combination with the modified Redfield theory. We demonstrate that a simultaneous fit of linear spectra, pump-probe, and pump-dump-probe kinetics can be obtained at a quantitative level using the disordered exciton model, which is essentially the same as used to model the spectral fluctuations in single LH2 complexes (Novoderezhkin, V.; Rutkauskas, D.; van Grondelle, R. Biophys. J. 2006, 90, 2890). The present studies suggest that the observed relaxation rates are strongly dependent on the realization of the disorder. A big spread of the rates (exceeding 3 orders of magnitude) is correlated with the disorder-induced changes in delocalization length and overlap of the exciton wave functions. We conclude that the bulk kinetics reflect a superposition of many pathways corresponding to different physical limits of energy transfer, varying from sub-20 fs relaxation between delocalized and highly spatially overlapping exciton states to >20 ps jumps between states localized at the opposite sides of the ring.

Heterogeneous and homogeneous crystal nucleation in colloidal hard-sphere like microgels at low metastabilities

We studied the crystallization kinetics of the homogeneous bulk as well as of the heterogeneous wall crystallization in a colloidal hard sphere model system within the fluid crystal coexistence region. Using time resolved static light scattering and Bragg microscopy we determined several parameters characterizing the crystallization process (induction times, growth coefficients, nucleation rate densities,…). By performing further analysis according to classical nucleation theory we can show that wall crystallization is favored by a vanishing nucleation barrier height leading to the conclusion that a hard sphere crystal completely wets a structureless hard wall.

Numerical analysis of growth kinetics of bulk III‐V crystals grown by liquid phase electroepitaxy

AbstractResults of time‐dependent simulations of growth of bulk binary III–V crystals by current controlled liquid phase electroepitaxy (LPEE) are presented using GaAs as example. Without any electrical current the LPEE system is isothermal, kept at 1073 K, thus no growth occurs. The electric current density of 10 A/cm2 leads to ohmic heating of the entire system, Peltier cooling of the Ga‐GaAs(seed) interface and electromigration of As species in liquid Ga. Neither Peltier nor Joule effects are considered at the source/solution interface since in the configuration chosen the electric current bypasses the source crystal. The Peltier‐induced cooling and electromigration of As induce growth of GaAs, originally at the rate of 0.5 μm/min. As the growth proceeds, the Peltier cooling is overcompensated by Joule heating, which leads to the reduction of growth rate and finally to standstill. It is shown that the LPEE growth is strongly time dependent, leading to the change of crystallization front, reflecting the fastest growth rate at the center of the crucible and the slowest, close to the crucible wall. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Deactivation studies of Fischer–Tropsch synthesis on nano-structured iron catalyst

Deactivation kinetics of bulk and nano-structured microemulsion prepared iron catalysts were studied in Fischer–Tropsch synthesis (FTS), from fitting of data to a generalized power-law expression (GPLE), r d = k d ( a − a ∞) m . Conventional bulk iron catalyst was prepared by general bulk co-precipitation method and nano-structured iron catalyst was prepared by microemulsion method. A deactivation model involving parallel paths is proposed, i.e. simultaneous conversion of (a) atomic to polymeric to graphitic carbon and (b) active carbon-rich carbides to inactive carbon-poor carbides. Compositions of bulk iron phase and phase transformations of carbonaceous species during catalyst deactivation in FTS reaction were characterized by temperature-programmed surface reaction with hydrogen (TPSR-H 2), XRD and TEM techniques.

Is the In Vitro Ejection of Bacteriophage DNA Quasistatic? A Bulk to Single Virus Study

Bacteriophage T5 DNA ejection is a complex process that occurs on several timescales in vitro. By using a combination of bulk and single phage measurements, we quantitatively study the three steps of the ejection—binding to the host receptor, channel-opening, and DNA release. Each step is separately addressed and its kinetics parameters evaluated. We reconstruct the bulk kinetics from the distribution of single phage events by following individual DNA molecules with unprecedented time resolution. We show that, at the single phage level, the ejection kinetics of the DNA happens by rapid transient bursts that are not correlated to any genome sequence defects. We speculate that these transient pauses are due to local phase transitions of the DNA inside the capsid. We predict that such pauses should be seen for other phages with similar DNA packing ratios.

Devitrification kinetics of bulk and pulverized sodium metaphosphate glassy phase

Crystallization kinetics of bulk and pulverized glass samples of the system mol% 50Na 2O:50P 2O 5 have been investigated through isothermal as well as non-isothermal DSC studies. Analysis of the crystallization exotherms reveals that the bulk sodium metaphosphate glass undergoes single-stage crystallization with an order parameter (Avrami constant) of 2.7 ± 0.1 and an activation energy for crystallization equal to 142.5 kJ/mol, suggesting internal (bulk) crystallization of the glass. The activation energy for structural relaxation, evaluated by the analysis of the dependence of T g on different heating rates, turns out to be 534.8 kJ/mol. The exotherm peaks of pulverized glasses exhibit a shift in the crystallization temperature, T c along with a change in the height and width of the peak. The pulverized glass sample undergoes surface crystallization, with almost the same value of activation energy for crystallization as that of bulk glass. The single-stage crystallization mechanism of sodium metaphosphate (bulk and pulverized) glass is closely associated with Johnson–Mehl–Avrami (JMA) model.

Surface and Bulk Kinetics of Lithium-Ions in Graphitic Anodes Using First Principles Calculations and Kinetic Monte Carlo

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Investigating Surface vs Bulk Kinetics in the Formation of a Molecular Complex via Solid-State Reaction by Simultaneous Raman/X-ray Powder Diffraction

The charge-transfer molecular complex fluorene/7,7,8,8-tetracyanoquinodimethane (TCNQ) was obtained by an unprecedented in situ solid-state direct synthesis. The reaction advancement was monitored with Raman spectroscopy and high-resolution X-ray powder diffraction (XRPD). The experiments were performed with a novel setup (SNBL, Grenoble) capable of combining both techniques simultaneously at in situ conditions. Raman spectroscopy allowed the characterization of the reaction kinetics during the initial steps at the surface of the TCNQ crystallites, when no or very little reaction is observed by the XRPD probe. From Rietveld refinement of the synchrotron XRPD data, the time evolution of the amounts of reactants and product was obtained for the reaction proceeding into the bulk of the TCNQ crystals, together with the crystal size analysis. These data were analyzed exploiting the Avrami equation to obtain rate constants, reaction orders, and activation energies. The reaction, after starting at the surface of...