True Kinetics Research Articles

Global reaction neural networks with embedded stoichiometry and thermodynamics for learning kinetics from reactor data

The digitalization of chemical research and industry is vastly increasing the available data for developing and parametrizing kinetic models. To exploit this data, machine learning approaches are needed that autonomously learn kinetic models from large amounts of reactor data. In this paper we develop such a tool. We present a Global Reaction Neural Network (GRNN) architecture that embeds thermodynamic and stoichiometric prior knowledge for the accurate, robust and data-efficient modelling of chemical kinetics. This network architecture is used in conjunction with neural ODEs to autonomously learn kinetic models directly from reactor data. Using the example of an adiabatic steam reformer, we demonstrate that our approach accurately recovers the true kinetics from reactor data, where conventional neural networks fail. It is further shown that the proposed framework can handle large datasets and learns kinetic models from up to 1000 reactor experiments in around ten minutes. Furthermore, due to the embedded physico-chemical knowledge, our model is robust to significant noise in the data, even in the low-data regime. We anticipate that our approach, in combination with emerging big data frameworks, will greatly increase the availability of accurate kinetic models, providing a boost to model-based reactor design and control.

Macroscopic modelling of the growth and substrate consumption of wild type and genetically modified Pichia pastoris.

Pichia pastoris is a popular yeast platform to generate several industrially relevant products which have applications in a wide range of sectors. The complexities in the processes due to the addition of a foreign gene are not widely explored. Since these complexities can be dependent on the strain characteristics, promoter, and type of protein produced, it is vital to investigate the growth and substrate consumption patterns of the host to facilitate customised process optimisation. In this study, the growth rates of P. pastoris GS115 wild type and genetically modified strains grown on glycerol and methanol in batch cultivation mode were estimated and the model providing the best representation of the true growth kinetics based on substrate consumption was identified. It was observed that the growth of P. pastoris exhibits Haldane kinetics on glycerol rather than the most commonly used Monod kinetics due to the inability of the latter to describe growth inhibition at high concentrations of glycerol. Whereas, the Cardinal Parameter Model, a newly proposed model for this application, was found to be the best fitting to describe the growth of P. pastoris on methanol due to its ability to describe methanol toxicity. Interestingly, the findings from this study concluded that in both substrates, the genetically engineered strain exhibited a higher growth rate compared to the wild type strain. Such an observation has not been established yet in other published works, indicating an opportunity to further optimise the carbon source feeding strategies when the host is grown in fed-batch mode. This article is protected by copyright. All rights reserved.

Tuning the Valence of MnOx Cathodes Reveals the Universality of the Proton‐Coupled Electrodissolution/Electrodeposition Mechanism in Rechargeable Aqueous Zn Batteries

AbstractThe charge storage mechanism of manganese oxides (MnOx) in rechargeable mild aqueous Zn batteries is still a matter of debate, with no consensus on mechanism and charge carriers. In this work, this issue is addressed by relying on a quantitative and comparative electrochemical study of low‐valence crystalline MnOx cathodes in a range of aqueous electrolytes, with a primary focus on spinel Mn3O4. The results demonstrate that the oxidation state of Mn in MnOx structures as well as their degree of crystallinity have little impact on the electrochemical reactivity, all MnOx being fully converted into soluble Mn2+ upon discharge. It is further revealed that this electrodissolution mechanism is affected by Mn3O4 dismutation in the most acidic electrolytes. Accordingly, the true thermodynamics and kinetics of Mn3O4 are only accessible at mildly acidic to neutral pHs. In addition, the study confirms the phase transformation of Mn3O4 to Mn5O8 upon galvanostatic oxidation, and demonstrates that this transformation only proceeds in Mn2+‐free electrolytes, since otherwise amorphous MnO2 electrodeposits on top of Mn3O4. Finally, it is concluded that regardless of the starting MnOx material, after the first discharge or a first charge/discharge cycle, subsequent charge/discharge cycles rely on a reversible proton‐coupled electrodeposition of amorphous MnO2.

Perspective on high-temperature surface oxygen exchange in a porous mixed ionic-electronic conductor for solid oxide cells.

The surface exchange coefficient (k) of porous mixed ionic-electronic conductors (MIECs) determines the device-level electrochemical performance of solid oxide cells. However, a great difference is reported for k values, which are measured using presently available technologies of electrical conductivity relaxation (ECR), electrochemical impedance spectroscopy (EIS), and oxygen isotope exchange (OIE). In terms of this issue, this perspective paper estimates the possible physiochemical processes for the oxygen reduction reaction (ORR) in porous MIECs by comparing the oxygen supply/consumption fluxes through calculation. Then, the potential problems associated with ECR, EIS, and OIE for application in porous materials are discussed regarding theory, assumptions, sample requirements, and data processing. Finally, gas diffusion effects are revealed by comparing the simulated and measured ECR profiles, which show that the ORR process can be significantly delayed by gas diffusion. This perspective aims to recommend a reasonable method to characterize the true ORR kinetics of porous electrodes and quantify the effect of gas diffusion.

Quantification of the Mesoscale Spatiotemporal Heterogeneities in Nickel-Rich Layered Oxide Cathodes By Raman Spectroscopy

Lithium-ion batteries consisting of the particulate porous electrodes, are the dominant energy storage devices, however, they suffer from random failures and safety-related accidents. Such arbitrary incidents arise from the spatiotemporal heterogeneities occurring due to the material thermodynamics[1] which results to local hot and cold spots and early battery failures. The past investigations of the heterogeneities in the battery materials rely on the sophisticated synchrotron X-ray methods[2]–[4], which are not easily accessible. Instead, in this study, we employ Raman spectroscopy on an in situ benchtop setup which provides several advantages while investigating the true electrochemical kinetics in graphite electrodes, such as: (i) the setup houses practical porous NMC532 cathodes under realistic electrochemical surroundings; (ii) the high resolution of 1-2 µm provides sufficient information on the larger cathode particles; (iii) the method can analyze hundreds of particles, statistically representing the entire composite electrode; and (iv) the spectra can be quantified to reveal the actual reaction area, thus revealing high-fidelity real-time electrochemical performance. We use this simple but precision method to track and analyze the active reaction regions at the mesoscale in the NMC532 electrode to obtain the true local current density, which was found to be an order of magnitude higher than the globally-averaged current density adopted by the existing studies.Raman spectroscopy can distinguish the vibrational modes of NMC532 with varying Li ion concentration. Since NMC532 is a solid-solution material, the Raman spectrum at each selected location can be deconvoluted into three distinct phases: empty, completely lithiated and partially lithiated. The partially lithiated regions participate in the surface reaction and can be identified to reveal the active reaction area. Thus, we quantified the active area fraction under slow galvanostatic conditions and generated a map of active regions with varying global Li ion fractions. Our results show that only 18% – 50% of the total particle area is active at any instant leading to higher local current densities than the globally-averaged electrode responses. The methods developed in this study are critical to estimate the kinetic parameters using true electrochemical responses and further aid in the design of the particulate porous electrodes.

Physiological and Sprint Kinetics Associated With the Yo-Yo Intermittent Recovery Test Level 1 Performances in Soccer Players.

The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) is often utilized to indirectly assess the cardiorespiratory fitness of team-sport athletes due to its proposed association with match-play high-speed running performance and predicted maximal oxygen uptake. No previous research has investigated the relationships between YYIR1 performances, actual oxygen uptake recorded during the YYIR1, and true all-out sprint kinetics (eg,maximal sprint speed, maximal force capacity, and maximal power output), which therefore served as the primary objective of this study. To assess the true physiological kinetics (V˙O2 and heart-rate responses) during the YYIR1 and to evaluate the correlations between the physiological kinetics, sprint kinetics, and YYIR1 performance parameters. A total of 23 amateur male soccer players were recruited for the study (age 22.52 [2.86]y; height 1.75 [0.06]m; body mass 65.61 [8.43]kg). Each participant completed a YYIR1 and 2 all-out sprint tests. Significant differences were observed between actual and predicted maximal oxygen-uptake values (Mdiff = 17.57mL·kg-1·min-1, P < .001, r = .63). Shuttle distances showed statistically significant correlations with maximal sprint speed (r = .42, P = .044) and theoretic maximal speed (r = .44, P = .035). However, no other correlations with sprint kinetic parameters (eg,maximal force or power output) were observed. Practitioners should carefully consider the outcomes and utilities of the parameters derived from the YYIR1. The estimations of maximal oxygen uptake from shuttle performances as a proxy for cardiorespiratory fitness are not adequate. However, shuttle distances appear to be positively associated with all-out sprinting capacities.

Acylation of m-cresol with acetic acid supported by in-situ ester formation on H-ZSM-5 zeolites

Friedel-Crafts acylation of phenolic compounds with carboxylic acids catalyzed by Brønsted-acid zeolites is an interesting reaction that could find application in the production of fuels and chemicals from renewable feedstocks. The mechanism of direct acylation of m-cresol with acetic acid over protonic zeolites and the role that the confining environment may have on reaction rate and product selectivity are topics of current interest. Here, we evaluate this reaction at varying conditions over H-ZSM-5 catalysts with different acid site densities. By decoupling the effect of parasitic phenomena – diffusion and catalyst deactivation – we have been able to evaluate the true kinetics of this reaction. We have found that, in the absence of a solvent, the reaction over H-ZSM-5 zeolites under commonly studied conditions (Si/Al = 40) at 250 °C is often influenced by the diffusion of reactants to active sites. By further decreasing active site density and operating under diffusion-free conditions, the true activation barrier for acetophenone (2-hydroxyl-4-methylacetophenone) formation obtained on H-ZSM-5 under surface-saturation conditions is relatively low (41 kJ/mol). This value is significantly lower than the barrier associated with the dehydration of the carboxylic acid to form surface acyl species when not assisted by the formation of intermediate ester species. Based on reaction kinetic analysis, it is proposed that the formation of acylium ion from adsorbed m-tolyl acetate is the rate-limiting step. However, feeding the intermediate ester – i.e., m-tolyl acetate – to act as acylating agent, results in reduced rates compared to those in which the acylating agent is acetic acid. This result reveals that diffusion of m-tolyl acetate is slow and that the kinetically relevant ester is formed within the confines of the zeolite pores. By co-feeding water with m-tolyl acetate, we reveal that the bulky ester is hydrolyzed to form smaller molecules that diffuse faster inside zeolite pores and subsequently enhance the reaction rate. Vapor phase acylation of m-cresol with acetic acid over low acid site density H-Beta zeolite confirms the role of the active intermediate ester in accelerating the rate of acylated product formation. Catalyst deactivation during reaction increases with the partial pressure of acetic acid, even under the zero-order kinetic regime, during which the partial pressure of produced gaseous ketene remains constant. This result would indicate that this usual coke precursor is not the main cause of deactivation, but rather bulkier compounds formed by subsequent esterification of acetic acid with the acylated product (e.g., 2-hydroxyl-4-methylacetophenone).

Determining robust reaction kinetics from limited data

AbstractAccurate chemical kinetics are essential for reactor design and operation. However, despite recent advances in “big data” approaches, availability of kinetic data is often limited in industrial practice. Herein, we present a comparative proof‐of‐concept study for kinetic parameter estimation from limited data. Cross‐validation (CV) is implemented to nonlinear least‐squares (LS) fitting and evaluated against Markov chain Monte Carlo (MCMC) and genetic algorithm (GA) routines using synthetic data generated from a simple model reaction. As expected, conventional LS is fastest but least accurate in predicting true kinetics. MCMC and GA are effective for larger data sets but tend to overfit to noise for limited data. LS‐CV strongly outperforms these methods at much reduced computational cost, especially for significant noise. Our findings suggest that implementation of CV with conventional regression provides an efficient approach to kinetic parameter estimation with high accuracy, robustness against noise, and only minimal increase in complexity.

Rethinking the design of a 2-methoxy-2-methyl-heptane process by unraveling the true thermodynamics and kinetics

Among other fuel additives — such as MTBE, ETBE, or TAME — 2-methoxy-2-methyl heptane (MMH) can increase the fuel octane number and reduce the CO emission. MMH can be obtained through the exothermal etherification of 2-methyl-1-heptene and methanol. Lately, many researchers have developed more and more efficient processes considering the kinetics corresponding to an endothermal reaction. However, in this work we demonstrate that the reaction is actually quite exothermal, and this has strong impact on the designed process. Also, the vapor–liquid equilibrium data predicted by UNIQUAC model for 2-methoxy-2-methyl heptane and 2-methyl-2-heptanol mixture reveals that product purification is more difficult, and it requires more energy to recover and obtain MMH with high purity. Considering these aspects, the 54.87 ktpy process developed in this paper is more realistic and energy intensive (1.82 kW h/kg MMH), with a TAC of 5.3 M$/year. The controllability of the process is proven for ±20% changes of 2-methoxy-2-methyl-heptane production rate.

Fluorescence Cross-Correlation Spectroscopy Yields True Affinity and Binding Kinetics of Plasmodium Lactate Transport Inhibitors.

Blocking lactate export in the parasitic protozoan Plasmodium falciparum is a novel strategy to combat malaria. We discovered small drug-like molecules that inhibit the sole plasmodial lactate transporter, PfFNT, and kill parasites in culture. The pentafluoro-3-hydroxy-pent-2-en-1-one BH296 blocks PfFNT with nanomolar efficiency but an in vitro selected PfFNT G107S mutation confers resistance against the drug. We circumvented the mutation by introducing a nitrogen atom as a hydrogen bond acceptor site into the aromatic ring of the inhibitor yielding BH267.meta. The current PfFNT inhibitor efficiency values were derived from yeast-based lactate transport assays, yet direct affinity and binding kinetics data are missing. Here, we expressed PfFNT fused with a green fluorescent protein in human embryonic kidney cells and generated fluorescent derivatives of the inhibitors, BH296 and BH267.meta. Using confocal imaging, we confirmed the location of the proposed binding site at the cytosolic transporter entry site. We then carried out fluorescence cross-correlation spectroscopy measurements to assign true Ki-values, as well as kon and koff rate constants for inhibitor binding to PfFNT wildtype and the G107S mutant. BH296 and BH267.meta gave similar rate constants for binding to PfFNT wildtype. BH296 was inactive on PfFNT G107S, whereas BH267.meta bound the mutant protein albeit with weaker affinity than to PfFNT wildtype. Eventually, using a set of PfFNT inhibitor compounds, we found a robust correlation of the results from the biophysical FCCS binding assay to inhibition data of the functional transport assay.

Operando Quantification of the Mesoscale Spatiotemporal Heterogeneities in Particulate Porous Electrode

Lithium-ion batteries consisting of the particulate porous electrodes, continue to be dominant energy storage devices. While the highly porous structures were introduced in the battery materials to maximize the interfacial area for better overall performance of the system, the appearance of spatiotemporal heterogeneities arising from the material thermodynamics leads to the localization of charge-transfer processes onto a limited portion of the available interfaces. The past investigations of the heterogeneities in the battery materials rely on the synchrotron X-ray[1]–[4], which is a specialized technique and not easily accessible. Instead, in this study, we have fabricated an operando benchtop setup under optical microscope which provides several advantages while investigating the true electrochemical kinetics in graphite electrodes, such as: (i) the setup houses practical porous graphite electrodes under realistic electrochemical surroundings; (ii) the visible light from the optical microscope does not cause any damage to the material; (iii) the method can analyze hundreds of particles, statistically representing the entire composite electrode; and (iv) the setup can capture snapshots every two seconds, thus revealing high-fidelity real-time electrochemical performance. We use this simple but precision method to track and analyze the operando (i.e., local and working) interfaces at the mesoscale in the graphite electrode to obtain the true local current density, which was found to be two orders of magnitude higher than the globally-averaged current density adopted by the existing studies.With our new kinetic theory for the dynamics of the phase evolution, we were able to achieve self-consistent precision understandings of the true local electrochemical kinetics, which have long been inferred only from globally-averaged electrode responses. The kinetic parameters, especially the diffusion coefficient, obtained from analyzing the operando interfacial current density are four orders of magnitude higher than the existing reports, but are much closer to and consistent with the ab initio predictions[5]. Our results therefore resolve the long-standing discrepancy between diffusion coefficients obtained from the traditional experiments and the first principle calculations. Contrary to prevailing beliefs, the electrochemical dynamics is not controlled by the solid-state diffusion process once the spatiotemporal reaction heterogeneities emerge. Traditional electroanalytical models based on planar electrodes that assume diffusion-limited process need to be modified to account for other rate-governing processes. Here, we advocate more careful examination of the phase transformation behaviors at both the micro and meso scales, for which the methods developed here are critical.

Rare events and first passage time statistics from the energy landscape.

We analyze the probability distribution of rare first passage times corresponding to transitions between product and reactant states in a kinetic transition network. The mean first passage times and the corresponding rate constants are analyzed in detail for two model landscapes and the double funnel landscape corresponding to an atomic cluster. Evaluation schemes based on eigendecomposition and kinetic path sampling, which both allow access to the first passage time distribution, are benchmarked against mean first passage times calculated using graph transformation. Numerical precision issues severely limit the useful temperature range for eigendecomposition, but kinetic path sampling is capable of extending the first passage time analysis to lower temperatures, where the kinetics of interest constitute rare events. We then investigate the influence of free energy based state regrouping schemes for the underlying network. Alternative formulations of the effective transition rates for a given regrouping are compared in detail to determine their numerical stability and capability to reproduce the true kinetics, including recent coarse-graining approaches that preserve occupancy cross correlation functions. We find that appropriate regrouping of states under the simplest local equilibrium approximation can provide reduced transition networks with useful accuracy at somewhat lower temperatures. Finally, a method is provided to systematically interpolate between the local equilibrium approximation and exact intergroup dynamics. Spectral analysis is applied to each grouping of states, employing a moment-based mode selection criterion to produce a reduced state space, which does not require any spectral gap to exist, but reduces to gap-based coarse graining as a special case. Implementations of the developed methods are freely available online.

Determination of kinetic parameters of exothermic condensed phase reaction using the energetic material ignition delay data

The kinetic parameters of condensed phase global reaction are required to calculate temporal and energetic characteristics of the ignition and combustion of energetic materials (EMs). The heating rate of EM in these processes exceeds 1000 K/s and therefore the kinetic data obtained via using classical thermal analysis methods with heating rate of 1–50 K/min may not provide the processes adequate description. A solution to the problem was suggested more than 50 years ago by Merzhanov who noticed a possibility to determine required kinetic parameters from the EM experimental ignition delays. However, mathematical background and justification for this approach has not been performed. It is commonly assumed that the approach yields the true kinetics at high heating rates of EMs. The present work aims to verify the validity of Merzhanov's approach. Numerical calculations were performed using transient mathematical models of the EM ignition and the results of virtual ignition experiments were processed using Merzhanov's ignition criterion. The deliverables were the values of kinetic parameters that substantially differ from those used as input data in numerical calculations. The paper concludes about necessity of elaborating mathematically substantiated techniques for determining kinetic parameters of global exothermic condensed-phase reaction via using the EM ignition delays.

Pressure DSC for energetic materials. Part 2. Switching between evaporation and thermal decomposition of 3,5-dinitropyrazole

Differential scanning calorimetry at an elevated external pressure (Pressure DSC) allows for shifting the vaporization of a sample to higher temperatures, thus often facilitating the direct observation of its thermal decomposition. In the present work, the thermolysis of a promising energetic material 3,5-dinitropyrazole was studied under pressures up to 10 MPa. The thermokinetic analysis of the datasets acquired at 2 and 5 MPa exhibited a pronounced kinetic compensation, thus allowing to build the joint formal kinetic model. The final kinetic scheme is comprised of the two parallel reactions, viz., the first-order process (Ea = 198 kJ mol−1) along with a first-order autocatalysis (Ea = 127 kJ mol−1). The experiment was complemented with the highly accurate CCSD(T)-F12 quantum chemical calculations. Theory revealed an unusual primary decomposition channel, viz., a sigmatropic [1,5]H-shift followed by the pyrazole ring opening yielding a molecular nitrogen and a nitro radical as simple primary products. Apart from this, the comparative thermogravimetry at a normal pressure yielded the vapor pressure of 3,5-dinitropyrazole along with the internally consistent set of phase change enthalpies. In general, the pressure DSC is a facile technique to study the true decomposition kinetics of the compounds that vaporize/sublime in conventional DSC experiments.

Optimising Hydrogel Release Profiles for Viro-Immunotherapy Using Oncolytic Adenovirus Expressing IL-12 and GM-CSF with Immature Dendritic Cells

Sustained-release delivery systems, such as hydrogels, significantly improve cancer therapies by extending the treatment efficacy and avoiding excess wash-out. Combined virotherapy and immunotherapy (viro-immunotherapy) is naturally improved by these sustained-release systems, as it relies on the continual stimulation of the antitumour immune response. In this article, we consider a previously developed viro-immunotherapy treatment where oncolytic viruses that are genetically engineered to infect and lyse cancer cells are loaded onto hydrogels with immature dendritic cells (DCs). The time-dependent release of virus and immune cells results in a prolonged cancer cell killing from both the virus and activated immune cells. Although effective, a major challenge is optimising the release profile of the virus and immature DCs from the gel so as to obtain a minimum tumour size. Using a system of ordinary differential equations calibrated to experimental results, we undertake a novel numerical investigation of different gel-release profiles to determine the optimal release profile for this viro-immunotherapy. Using a data-calibrated mathematical model, we show that if the virus is released rapidly within the first few days and the DCs are released for two weeks, the tumour burden can be significantly decreased. We then find the true optimal gel-release kinetics using a genetic algorithm and suggest that complex profiles present unnecessary risk and that a simple linear-release model is optimal. In this work, insight is provided into a fundamental problem in the growing field of sustained-delivery systems using mathematical modelling and analysis.

Activity Coefficients for Liquid Organic Reactions: Towards a Better Understanding of True Kinetics with the Synthesis of Jasmin Aldehyde as Showcase.

The aldol condensation of benzaldehyde and heptanal is taken as an example of reversible liquid phase organic reactions to show that inclusion of activity coefficients reveal distinct differences in conversion and product distribution when different solvents methanol, ethanol, n-propanol, or n-butanol are used. The purpose of this work is to show a pronounced solvent effect for a given set of identical kinetic parameters, i.e., the same liquid phase kinetics can result in different conversion and yield values, depending on the choice of solvent. It was shown that subsequent parameter estimation without inclusion of the activity coefficients resulted in a pronounced deviation from the ‘true’ kinetics, up to a factor of 30. It is proposed that the usage of average activity coefficients gives already a significant improvement, resulting in acceptable parameter estimates.

Impact of defect-driven surface inhomogeneity and minimal island formation on temperature-programmed desorption spectra: A kinetic Monte Carlo study

Inhomogeneity often manifests itself on surfaces with pre-adsorbed adsorbates in which islands have widely-disparate sizes due to the presence of distinct morphological features or perhaps even impurities, or defects. In this kinetic Monte Carlo study, we developed a model in which these defects are in the form of vacancy clusters or chains and grow progressively longer with each repeated adsorption-desorption cycle owing to repeated stress that a substrate is subjected to with each cycle. We then explored different simulation-imposed conditions – vacancy or defect concentration as well as maximum vacancy chain length – and noted their impact on the resulting temperature-programmed desorption spectra. We found that growing chains can induce single desorption peak to progressively shift, then split into two closely-overlapping ones over a course of several such cycles. Interestingly, such evolving peaks may hide the true desorption kinetics since calculation of desorption order may yield unconventional, non-integer values – neither zero, first or second-order. We also observed that for the same vacancy concentration, peak-splitting becomes more pronounced with increasing maximum chain length. Analysis of simulation data also revealed that unlike bigger and more compact islands, small ones follow first-order desorption kinetics rather than half-order kinetics.

Modeling mafic carbonation efficiency using mafic rock chemistries from Nevada, USA

Mineral carbonation is one of the many ways that are being actively investigated to sequester point-source carbon dioxide emissions. However, relations between reaction conditions, variations in reactant mineral composition, and carbon sequestration potential are poorly understood. In this study we used reaction path geochemical modeling to evaluate carbon sequestration potential during ex-situ mineral carbonation of ten mafic rock samples from Nevada, USA. Models were run using arbitrary dissolution kinetics at temperatures between 0 and 200 °C. A subset of models were run using true dissolution kinetics. In the models, carbon is sequestered in 5 mineral phases: magnesite, siderite, dolomite, calcite, and dawsonite, with magnesite and dolomite the most abundant. Dawsonite sequesters carbon at T > 150 °C in most of the arbitrary kinetics models but is not a significant carbon sink in the models using true dissolution kinetics. The arbitrary kinetics models resulted in 4.5–13 mol of carbon sequestered per kg of reacted mafic rock. True kinetics models only resulted in 1–2 mol of carbon sequestered, but the models only reacted 12.5 to 15 wt percent of the mafic rock inputs. Product minerals using the arbitrary kinetics model have volumes 150%–470% larger than the reactant volumes, whereas using true kinetics the models have a modest increase. Modeling presented herein confirms several areas of Nevada as having potential for mafic rock carbonation, some of which are located near existing coal- and natural gas-fired power plants. As shown in this study, reaction path modeling is a vital and inexpensive tool to help optimize costs and reaction conditions for ex-situ mafic rock carbonation projects.

The oxidation of Fe(II) with Cu(II) in acidic sulfate solutions with air at elevated pressures

The oxidation of ferrous ions in acidic sulfate solutions in the presence of cupric ions at elevated air pressures was investigated in a high-intensity gas–liquid contactor. The study was required for the design of the regeneration steps of the novel Vitrisol® desulphurization process. The effects of the Fe2+ concentration, Cu2+ concentration, Fe3+ concentration, initial H2SO4 concentration, and partial oxygen pressure on the reaction rate were determined at three different temperatures, i.e., T = 50 °C, 70 °C, and 90 °C. Most of the experiments were determined to be affected by the mass transfer of oxygen, and therefore true intrinsic kinetics could not be fully determined. An increase in Fe2+ and Cu2+ concentrations, as well as the partial pressure of oxygen and temperature, increased the Fe2+ oxidation rate. H2SO4 did not influence the Fe2+ oxidation rate. An increase in Fe3+ concentration decreased the Fe2+ oxidation rate. Although determined from experiments partially affected by mass transfer, a first order of reaction in Fe2+ was observed, fractional orders in both Cu2+ and O2 were measured, a zero order in H2SO4 was determined, and a negative, fractional order in Fe3+ was obtained. The activation energy was estimated to be 31.3 kJ/mol.

Cytomegalovirus Late Protein pUL31 Alters Pre-rRNA Expression and Nuclear Organization during Infection.

The replication cycle of human cytomegalovirus (CMV) leads to drastic reorganization of domains in the host cell nucleus. However, the mechanisms involved and how these domains contribute to infection are not well understood. Our recent studies defining the CMV-induced nuclear proteome identified several viral proteins of unknown functions, including a protein encoded by the UL31 gene. We set out to define the role of UL31 in CMV replication. UL31 is predicted to encode a 74-kDa protein, referred to as pUL31, containing a bipartite nuclear localization signal, an intrinsically disordered region overlapping arginine-rich motifs, and a C-terminal dUTPase-like structure. We observed that pUL31 is expressed with true late kinetics and is localized to nucleolin-containing nuclear domains. However, pUL31 is excluded from the viral nuclear replication center. Nucleolin is a marker of nucleoli, which are membrane-less regions involved in regulating ribosome biosynthesis and cellular stress responses. Other CMV proteins associate with nucleoli, and we demonstrate that pUL31 specifically interacts with the viral protein, pUL76. Coexpression of both proteins altered pUL31 localization and nucleolar organization. During infection, pUL31 colocalizes with nucleolin but not the transcriptional activator, UBF. In the absence of pUL31, CMV fails to reorganize nucleolin and UBF and exhibits a replication defect at a low multiplicity of infection. Finally, we observed that pUL31 is necessary and sufficient to reduce pre-rRNA levels, and this was dependent on the dUTPase-like motif in pUL31. Our studies demonstrate that CMV pUL31 functions in regulating nucleolar biology and contributes to the reorganization of nucleoli during infection.IMPORTANCE Nucleolar biology is important during CMV infection with the nucleolar protein, with nucleolin playing a role in maintaining the architecture of the viral nuclear replication center. However, the extent of CMV-mediated regulation of nucleolar biology is not well established. Proteins within nucleoli regulate ribosome biosynthesis and p53-dependent cellular stress responses that are capable of inducing cell cycle arrest and/or apoptosis, and they are proposed targets for cancer therapies. This study establishes that CMV protein pUL31 is necessary and sufficient to regulate nucleolar biology involving the reorganization of nucleolar proteins. Understanding these processes will help define approaches to stimulate cellular intrinsic stress responses that are capable of inhibiting CMV infection.