Inert Products Research Articles

Modeling and forecasting biogas production from anaerobic digestion process for sustainable resource energy recovery

Anaerobic digestion (AD) is one of the most extensively accepted processes for organic waste cleanup, and production of both bioenergy and organic fertilizer. Numerous mathematical models have been conceived for modeling the anaerobic process.In this study, a new modified dynamic mathematical model for the simulation of the biochemical and physicochemical processes involved in the AD process for biogas production was proposed. The model was validated, and a sensitivity analysis based on the OAT approach (one-at-a-time) was carried out as a screening technique to identify the most sensitive parameters. The model was developed by updating the bio-chemical framework and including more details concerning the physico-chemical process. The fraction XP was incorporated into the model as a particulate inert product arising from biomass decay (inoculum). New components were included to distinguish between the substrate and inoculum, and a surface-based kinetics was used to model the substrate disintegration. Additionally, the sulfate reduction process and hydrogen sulfide production have been included. The model was validated using data extracted from the literature. The model's ability to generate accurate predictions was testified using statistical metrics. The model exhibited excellent performance in forecasting the parameters related to the biogas process, with measurements falling within a reasonable error margin. The relative absolute error (rAE) and root mean square error (RMSE) were both less than 5 %, indicating a high ability of the current model in comparison with the literature. Additionally, the scatter index (SI) was below 10 %, and the Nash-Sutcliffe efficiency (NES) approached one, which affirms the model's accuracy and reliability. Finally, the model was applied to investigate the performances of the AD of food waste (FW). The findings of this study support the robustness of the developed model and its applicability as a virtual platform to evaluate the efficiency of the AD treatment and to forecast biogas production and its quality, CO2 emission, and energy potential across various organic solid waste types.

Simultaneous regulation of the solvation shell and electrode interface via a multifunctional and low-cost additive enabling long-life aqueous Zn metal batteries

Zinc metal batteries have great potential for energy storage applications in smart grids. However, the Zn metal anode presents significant challenges, such as the irrepressible growth of zinc dendrites on the anode’s surface, the accumulation of inert products, and the hydrogen evolution reaction. These issues can lead to the decreased cycling stability of the anode. To solve these problems, we developed a method of adding sodium p-toluenesulfonate to the electrolyte to protect the zinc metal anode. Density functional theory calculations show that the −SO3 functional group in sodium p-toluenesulfonate can alter the solvation structure of Zn2+ and adsorb onto the surface of the Zn metal anode. Thus, the Zn||Zn symmetric cell could be cycled stably for over 2000 h, whereas the Zn||Cu half-cell could be cycled stably for over 5000 cycles, with an average Coulombic efficiency of 99.87 %. The Zn||I2 full cell could be cycled stably for 10,000 cycles under test conditions of 1A/g, and the capacity retention rate was 95.49 %. This study provides insights into the use of additives in the electrolytes of zinc metal batteries.

Primaquine-5,6-Orthoquinone Is Directly Hemolytic to Older G6PD Deficient RBCs in a Humanized Mouse Model.

Primaquine and Tafenoquine are the only approved drugs that can achieve a radical cure for Plasmodium vivax malaria but are contraindicated in patients who are deficient in glucose 6-phosphate dehydrogenase (G6PDd) due to risk of severe hemolysis from reactive oxygen species generated by redox cycling of drug metabolites. 5-hydroxyprimaquine and its quinoneimine cause robust redox cycling in red blood cells (RBCs) but are so labile as to not be detected in blood or urine. Rather, the quinoneimine is rapidly converted into primaquine-5,6-orthoquinone (5,6-POQ) that is then excreted in the urine. The extent to which 5,6-POQ contributes to hemolysis remains unclear, although some have suggested that it is a minor toxin that should be used predominantly as a surrogate to infer levels of 5-hydroxyprimaquine. In this report, we describe a novel humanized mouse model of the G6PD Mediterranean variant (hG6PDMed-) that recapitulates the human biology of RBC age-dependent enzyme decay, as well as an isogenic matched control mouse with human nondeficient G6PD hG6PDND In vitro challenge of RBCs with 5,6-POQ causes increased generation of superoxide and methemoglobin. Infusion of treated RBCs shows that 5,6-POQ selectively causes in vivo clearance of older hG6PDMed- RBCs. These findings support the hypothesis that 5,6-POQ directly induces hemolysis and challenges the notion that 5,6-POQ is an inactive metabolic waste product. Indeed, given the extreme lability of 5-hydroxyprimaquine and the relative stability of 5,6-POQ, these data raise the possibility that 5,6-POQ is a major hemolytic primaquine metabolite in vivo. SIGNIFICANCE STATEMENT: These findings demonstrate that 5,6-POQ, which has been considered an inert waste product of primaquine metabolism, directly induces ROS that cause clearance of older G6PDd RBCs. As 5,6-POQ is relatively stable compared with other active primaquine metabolites, these data support the hypothesis that 5,6-POQ is a major toxin in primaquine induced hemolysis. The findings herein also establish a new model of G6PDd and provide the first direct evidence, to our knowledge, that young G6PDd RBCs are resistant to primaquine-induced hemolysis.

Design and fabrication of magnetic cross-linked laccase aggregate using superparamagnetic metal-organic frameworks for phenol removal

Phenolic pollutants represent a significant environmental concern due to their widespread presence in industrial effluents, agricultural runoff, and urban waste streams. Enzymatic bioremediation emerges as a promising approach for the efficient removal of phenolic pollutants from contaminated environments. Laccases exhibit remarkable catalytic capabilities in degrading phenolic compounds into less harmful or even inert products. In this study, magnetic cross-linked laccase aggregate was prepared using superparamagnetic metal-organic frameworks and then was applied for phenol removal. The obtained results showed that the magnetic cross-linked laccase aggregate retains its activity across a broad pH range. Interestingly, (NH4)2SO4 exhibited a positive influence on enzyme activity, resulting in a relative activity of 137.7 %. The findings suggest that an optimal concentration range of 0.4–0.8 % can achieve maximum enzyme activity while avoiding potential negative impacts associated with excessive cross-linking. Optimal pH and temperature conditions were identified for enhanced phenol removal efficiency as pH 4.5 and 45℃, respectively. The investigation revealed the remarkable reusability of the cross-linked enzyme over multiple cycles. Harnessing the power of enzymes for phenolic pollutant remediation holds immense promise for mitigating environmental pollution and safeguarding public health.

Tougher Bioadhesives through Dual Stimulation Strategies.

Carbene-based bioadhesives have favourable attributes for tissue adhesion, including non-specific bonding to wet and dry tissues, but suffer from relatively weak fracture strength after photocuring. Light irradiation of carbene-precursor (diazirine) also creates inert side products that are absent under thermal activation. Herein, a dual activation method combines light irradiation at elevated temperatures for the evaluation of diazirine depletion and effects on cohesive properties. A customized photo/thermal-rheometer evaluates viscoelastic properties, correlated to the kinetics of carbene:diazoalkane ratios via 19F NMR). The latter exploits the sensitive -CF3 functional group to determine joule-based light/temperature kinetics on trifluoroaryl diazirine consumption. The combination of heat and photoactivation produced bioadhesives that are 3× tougher compared to control. Dual thermal/light irradiation may be a strategy to improve viscoelastic dissipation and toughness of photo-activated adhesive resins.

A rechargeable calcium-oxygen battery that operates at room temperature.

Calcium-oxygen (Ca-O2) batteries can theoretically afford high capacity by the reduction of O2 to calcium oxide compounds (CaOx) at low cost1-5. Yet, a rechargeable Ca-O2 battery that operates at room temperature has not been achieved because the CaOx/O2 chemistry typically involves inert discharge products and few electrolytes can accommodate both ahighly reductive Ca metal anode and O2. Here we report a Ca-O2 battery that is rechargeable for 700 cycles at room temperature. Our battery relies on a highly reversible two-electron redox to form chemically reactive calcium peroxide (CaO2) as the discharge product. Using a durable ionic liquid-based electrolyte, this two-electron reaction is enabled by the facilitated Ca plating-stripping in the Ca metal anode at room temperature and improved CaO2/O2 redox in the air cathode. We show the proposed Ca-O2 battery is stable in air and can be made into flexible fibres that are weaved into textile batteries for next-generation wearable systems.

Experimental and numerical study on suppressing coal dust deflagration flame with NaHCO3 and MPP

In this paper, the flame propagation behavior and free radical reaction mechanism of two powder explosive suppressants, sodium bicarbonate (NaHCO3) and polyphosphate melamine (MPP), at different additions were investigated using Hartmann experimental system and CHEMKIN-PRO numerical simulation. The results showed that NaHCO3 and MPP showed different inhibitory advantages. MPP mainly suppressed the propagation of flame during the development and rapid rise stages, while NaHCO3 had a better suppression effect at the preliminary stage of explosion. The gas phase kinetic analysis also proved that the NaHCO3 reaction was rapid, and it could decompose and endothermy at the beginning of the explosion, and generate gaseous H2O and CO2 to dilute the concentration of volatile components. Meanwhile, NaOH, NaO, and NaO2 produced by decomposition consumed free radicals and reduced the initial reaction rate of the explosion. In the process of gas phase reaction, MPP continuously reduced the amount of flame free radicals through a inhibition cycle of HPO3 ⇔ PO2, and generated a large number of inert products for inerting fixed carbon, exhibiting better long-term effectiveness. This study can provide a reference for the selection and design of explosion suppressants.

Multiple-peak traveling waves of the Gray-Scott model

We study a reaction-diffusion system which models the pre-mixed isothermal autocatalytic chemical reaction of order m (m > 1) between two chemical species, a reactant A and an auto-catalyst B, A + m B --> (m+1) B, and a linear decay B -->C, where C is an inert product. The special case of m = 2 is the much studied Gray-Scott model, but without feeding. We prove existence of multiple traveling waves which have distinctive number of local maximaor peaks. It shows a new and very distinctive feature of Gray-Scott type of models in generating rich and structurally different traveling pulses than related models in literature such as isothermal autocatalysis without decay, or a bio-reactor model with isothermal autocatalysis of order m + 1 with m-th order of decay.

Strong enhancement on acetaminophen removal in thermal-activated peroxymonosulfate with sodium metaborate: Performance, mechanism, and control of chlorinated by-products formation

This study introduced sodium metaborate (NaBO2) into thermal/PMS system to enhance acetaminophen degradation. The added NaBO2 possessed better performance than sodium tetraborate in accelerating the degradation of acetaminophen with thermal/PMS system over the wide pH range from 3.0 to 11.0. NaBO2 could be partly hydrolyzed to the strong buffer capacity of the pair of H3BO3/B(OH)4− to well keep the reaction solution pH at 9.4–9.7 regardless of the initial pH. HOOB(OH)3− and HOOBO were produced via the reactions between PMS and B(OH)4−/BO2−. 1O2 and HO• were the main ROS accountable for acetaminophen degradation in NaBO2/thermal/PMS system. 1O2 was mainly formed from the self-decomposition of PMS and the reactions between PMS and HOOB(OH)3−/HOOBO. HO• was mainly formed from the thermolysis of the O-O bonds of PMS, HOOB(OH)3− and HOOBO. Three elimination pathways of acetaminophen were proposed according to the identified nine elimination intermediates, and the reaction solution toxicity was significantly decreased in NaBO2/thermal/PMS system. Improving NaBO2 dosage, PMS concentration and reaction temperature could accelerate acetaminophen removal. Cl− and Br− significantly promoted acetaminophen removal, while humic acid had the adverse effect. NaBO2/thermal/PMS system had well anti-interference capacity for actual water constituents. Moreover, the added NaBO2 could significantly inhibit the production of chlorinated by-products via the transformation of the free chlorine to the inert product of B(OH)3OCl− in Cl−-containing water treatment with NaBO2/thermal/PMS system. This study provides an effective method for improving the thermal/PMS system oxidation capacity and suppressing the chlorinated by-products production in Cl−-containing water treatment.

Distribution of Enthalpy in Rotating Detonation Engine

In Rotating Detonation Engine (RDE), the detonation wave rotates inside the annulus of thecombustor. After initiation by a pre-detonator, this detonation wave can be sustained by thecontinuous supply of fuel and oxidiser. The frequency of rotation is reported to be of the orderof 5-10 KHz indicating a near continuous operation which can be used in rocket andairbreathing propulsion systems. An experimental study on the RDE is being carried out atNational Centre for Combustion Research and Development (NCCRD), Indian Institute ofTechnology (IIT), Madras using hydrogen and air system. In addition,N2H4 - N2O4 hypergolicsystemreported in literature is considered for comparative study. In order to understand thevarious processes undergone by the flow through the RDE, a detailed thermodynamic analysisis performed. The procedure is explained in greater detail for the better understanding of thevarious state properties in the entire flow field. The flow field comprises of detonation wave,trailing oblique shock wave and Prandtl- Mayer expansion waves. There are two slip lines,one separating the fresh reactants and inert combustion products of the previous cycle ofdetonation wave propagation and another separating the products of detonation combustionand the shocked inert products. Though all the state properties will be evaluated, the enthalpydistribution is considered in the entire flow field of RDE and discussed. This provides theknowledge of the energy availability in various flow regimes and the extent of energyconversion due to detonative combustion, flow expansion, shock compression, and axial flowexciting through the combustor outlet. Propulsion parameters such as axial specific thrust andspecific impulse are computed to show the capability of this modelling approach.

Inhibition of transition-metal dissolution with an inert soluble product interface constructed by high-concentration electrolyte

The formation of a compact and stable cathode electrolyte interphase (CEI) film is a promising way to improve the high voltage resistance of lithium-ion batteries (LIBs). However, challenges arise due to the corrosion of hydrogen fluoride (HF) and the dissolution of transition metal ions (TMs) in harsh conditions. To address this issue, researchers have constructed an anion-derived CEI film enriched with LiF and LiPO2F2 soluble product on the surface of LiNi0.5Mn1.5O4 (LNMO) cathode in highly concentrated electrolytes (HCEs). The strong binding of LiF and LiPO2F2 generated an inert LiPO2F2 soluble product interface, which inhibited HF corrosion and maintained the spinel structure of LNMO, contributing to a capacity retention of 92% after 200 cycles at 55°C in the resulting cell with a soluble LiPO2F2-containing CEI film. This new approach sheds light on improving the electrode/electrolyte interface for high-energy LIBs.

Stability Criteria for Self-Propagating Reaction Waves in Co/Al Multilayers.

The propagation of self-sustained formation reactions in sputter-deposited Co/Al multilayers is known to exhibit a design-dependent instability. Multilayers having thin bilayers (<55 nm period) exhibit stable propagating waves, whereas those with a larger period react unstably. The specific two-dimensional (2D) instability observed involves the transverse propagation of a band in front of a stalled front commonly referred to as a "spin band." Previous finite-element studies have shown that these instabilities are thermodynamically driven by the forward conduction of heat away from the flame front. However, the magnitude of that loss is inherently tied to the bilayer design in traditional bimetallic multilayers, which couples any proposed stability criteria to a varying critical diffusion distance. This work utilizes a recently developed class of materials known as "inert-mediated reactive multilayers" to decouple the thermodynamic and kinetic contributions to propagating wave stability by reducing the stored chemical energy density in normally stable bilayer designs. By depositing an inert product phase (B2-CoAl) within the mid-plane of Co and Al reactant layers, spin instabilities arise as a function of both diluted volume and critical diffusion distance. From there, a stability criterion is determined for Co/Al multilayers based on enthalpy loss from the reaction zone, and its physical significance is explored.

Experimental study on inert products, moisture, and particle size effect on the minimum ignition energy of combustible dusts

Handling combustible dusts not only continues to pose a risk to industry but can also affect the safety of society. Explosion risk could be avoided or mitigated trying to guarantee inherent safety throughout the product life chain. One way to reduce the risks when dealing with combustible dust is to increase the Minimum Ignition Energy (MIE) in order to decrease combustible dust ignition sensitivity. To achieve this decrease, the inertization technique, also known as moderation, will be used. It consists of adding inert powders or humidity to the combustible dust. As sometimes end-users also must deal with the handling of flammable dusts, this study aims to find the most optimal inert for toner waste from printers and Holi powder (organic coloured dust from Indian parties), taking Lycopodium as a reference. Calcium carbonate, sodium bicarbonate and gypsum are proposed as inert materials. In addition, with the aim of giving a second use to biomass boiler waste or boiler slagging, this waste will be analyzed as inert, as well as how humidity affects the combustible dusts. Then, sodium bicarbonate will be tested at different granulometries to evaluate the effect of particle size on moderation process. The tests were carried out in the modified Hartmann apparatus or MIKE 3.0. Mechanisms such as decomposition of inert dust have been analyzed by thermogravimetric analysis (TGA)). The results show that gypsum and moisture are the best performing inert followed by calcium carbonate. Boiler slagging and solid bicarbonate contribute to a decrease in the MIE in some of the tests. The reasons for this deviation are discussed in the presented article. When sodium bicarbonate is analyzed at different particle sizes, it is found that the optimum particle size does not match the particle size of the combustible dust. According to the tests, there is an optimum point for which the inert powder provides better results.

Toward an Understanding of Bimetallic MXene Solid‐Solution in Binder‐Free Electrocatalyst Cathode for Advanced Li–CO2 Batteries

AbstractLi–CO2 batteries have received extensive attention due to their high energy storage capacity and utilization of CO2 resources. Herein, bimetallic MXene solid‐solution TiVC is prepared and combined with highly conductive graphene for the construction of binder‐free electrocatalyst cathodes for Li–CO2 batteries. Considering the electronic structure, the unique synergy effect between Ti and V in TiVC enhances the interfacial chemical bonding ability, facilitates sufficient exposure of active sites and promotes catalytic interfacial structural reformation, thereby promoting the reversible formation and decomposition of the chemically inert discharge product Li2CO3. Meanwhile, the abundant pores and excellent electron transfer ability of graphene aerogel are conducive to the gas diffusion and ion transport, thus reducing the mass and charge transfer resistance. As a result, the assembled Li–CO2 battery presents an excellent discharge capacity of 27 880 mAh g−1 with a stable discharge plateau of 2.77 V and low overpotential of 1.5 V based on the TiVC‐graphene aerogel electrocatalytic cathode. The density functional theory calculations are further performed to deeply reveal the unique electronic structure information between Ti and V in the solid‐solution TiVC. This study provides inspiration for exploring more bimetallic MXene solid solutions and developing advanced cathode catalysts for flexible Li–CO2 batteries.

Study of Photocatalytic Oxidation of Micropollutants in Water and Intensification Case Study

During the last decades, heterogenous photocatalysis has shown as the most promising advanced oxidation process for the removal of micropollutants due to degradation rate, sustainability, non-toxicity, and low-cost. Synergistic interaction of light irradiation, photocatalysts, and highly reactive species are used to break down pollutants toward inert products. Even though titanium dioxide (TiO2) is the most researched photocatalyst, to overcome shortcomings, various modifications have been made to intensify photocatalytic activity in visible spectra range among which is modification with multiwalled carbon nanotubes (MWCNTs). Therefore, photocatalytic oxidation and its intensification by photocatalyst’s modification was studied on the example of four micropollutants (diclofenac, DF; imidacloprid, IMI; 1-H benzotriazole, BT; methylene blue, MB) degradation. Compound parabolic collector (CPC) reactor was used as, nowadays, it has been considered the state-of-the-art system due to its usage of both direct and diffuse solar radiation and quantum efficiency. A commercially available TiO2 P25 and nanocomposite of TiO2 and MWCNT were immobilized on a glass fiber mesh by sol-gel method. Full-spectra solar lamps with appropriate UVB and UVA irradiation levels were used in all experiments. Photocatalytic degradation of DF, IMI, BT, and MB by immobilized TiO2 and TiO2/CNT photocatalysts was achieved. Mathematical modelling which included mass transfer and photon absorption was applied and intrinsic reaction rate constants were estimated: kDF=3.56 × 10−10s−1W−0.5m1.5, kIMI=8.90 × 10−11s−1W−0.5m1.5, kBT=1.20 × 10−9s−1W−0.5m1.5, kMB=1.62 × 10−10s−1W−0.5m1.5. Intensification of photocatalysis by TiO2/CNT was observed for DF, IMI, and MB, while that was not the case for BT. The developed model can be effectively applied for different irradiation conditions which makes it extremely versatile and adaptable when predicting the degradation extents throughout the year using sunlight as the energy source at any location.

A novel green IFR system: Design of a self-assembled peanut shell-based flame retardant and its fire performance in EP

Carbon derived from peanut shell (CPS) with 2D structure has been proved to own sufficient thermal stability and is a promising flame retardant (FR) additive for EP in our previous work. To further explore the feasibility of implementing CPS into the intumescent fire retardant (IFR) system, a novel green IFR system was first proposed in this study. Environmental-friendly chemicals phytic acid (PA) and melamine were self-assembled on the carbon's surface through the hydrothermal method. Cone calorimeter test results reveal that 3 wt% loading of the proposed IFR reduces total heat release (THR) by 38.8 % and total smoke release (TSR) by 31.3 %. What's more, the char residue grows significantly, from 5.8 % to 14.3 %. The fire retardancy mechanism was also studied. For the gaseous phase, the release of inert gas products from melamine prevents volatile decomposition products into the combustion zone. In terms of the solid phase, a synergistic barrier effect is provided by 2D structure of peanut shell derived carbon and the intumescent residue with a compact exterior layer, protecting the underlying polymer matrix. This green IFR system provides better fire performance, which can be a potential alternative for EP and extend its application.

Actualizing concept without language: a diffractive analysis of educational practice for children with disabilities with handmade manipulative materials in Japan

This study reconsidered educational materials by analyzing educators’ opinions regarding handmade manipulative materials (HMMs) for children with profound intellectual and multiple disabilities in Japan. Instead of concurring with the view that educational materials are static and inert products, the author adopted an agential realist perspective and considered them as agencies working and becoming with teachers and children. The author interviewed two retired teachers who had spent more than 30 years in HMM production and analyzed the obtained data using a diffractive methodology. Findings showed that making and remaking HMMs allowed teachers and children to engage with actualizing concepts without language and demonstrated the open-ended nature of learning for teachers and children with HMMs.

Education

This issue of SIAM Review presents two papers in the Education section. The first paper, “Deforming $\|\cdot\|_1$ into $\|\cdot\|_\infty$ via Polyhedral Norms: A Pedestrian Approach,” is contributed by Manlio Gaudioso and Jean-Baptiste Hiriart-Urruty. The paper starts from the well-known properties of the $\ell_p$-norms in the Euclidean space $\mathbb{R}^n$. For $x\in\mathbb{R}^n$ and $p\geq 1$, the norm is given by $\|x\|_p=\big(\sum_{i=1}^n |x_i|^p\big)^\frac{1}{p}$ with the limiting case $p\to\infty$ providing the norm $\|x\|_\infty=\max_{1\leq i\leq n} |x_i|.$ The unit balls determined by the norms for $p=1$ and $p=\infty$ are polyhedral, while for $p\in (1,\infty)$ the unit ball has a smooth surface. Furthermore, the unit balls become larger when $p$ grows. One can represent the polyhedral norms (for $p=1$ or $p=\infty$) as maxima of linear forms, and this observation motivates the following notion. For an integer $k$ with value between 1 and $n$, we define the following real-valued function: \[ N_k(x)=\max\|x_i_1|+|x_i_2|+\dots+|x_i_k|: 1łeq i_1 <\dots <i_k łeq n\. \] It is not difficult to check that $N_k$ is a norm, $N_1$ is the infinity norm, $N_n$ is the $\ell_1$-norm, and $N_k$ provides a value between them. In this way, the $\ell_1$ ball is deformed into the $\ell_\infty$ ball using only polyhedral convex sets. The authors discuss the properties and some representations of these norms. They provide the distance between the unit balls when $k$ changes, and discuss the relations of $N_k$ to support functions and gauges. Special cases for $n=3$ or 4 are examined and illustrated. Conjugate duality is invoked to present the dual norm to $N_k$ and the respective dual ball. The authors point out the relevance of these norms to some modern optimization problems, in which a sparse solution is desired. The polyhedral representation of the norms also facilitates numerical methods. The paper is written in a clear and engaging manner and is accessible to advanced undergraduate students who are familiar with basic notions of convex analysis. The paper “Analyzing Pattern Formation in the Gray--Scott Model: An XPPAUT Tutorial” is presented by Demi L. Gandy and Martin R. Nelson. It discusses a mathematical model of autocatalytic chemical processes that may lead to spontaneous formation of spatial and spatio-temporal patterns. The authors focus on a reaction-diffusion model, introduced by Gray and Scott, in which a pair of two chemicals, one reacting and one diffusing, can give rise to formation of spots, stripes, spirals, and other patterns. The model consists of two partial differential equations (PDEs) describing the process, in which two generic chemicals U and V react to produce a product P. It assumes that U is continuously supplied and the inert product P is continuously removed. The model uses the concentrations of U and V, the rate of replenishment of U, and the rate at which V decays to produce P. It also uses two diffusion constants, representing the rate at which each chemical moves spatially. The paper explains the main steps of the analysis of this model for the purpose of identifying pattern formation and illustrates this using an example. The first step is to understand the dynamics of the corresponding homogeneous system, which is obtained by neglecting the diffusion terms. Once the spatial dependence is removed the PDE system reduces to a pair of ordinary differential equations. The steady states are identified and their stability is characterized. The key step is to understand how changes of the parameters impact the steady states. At this point, software named XPPAUT may be used to compute bifurcation diagrams in order to gain more detailed information about periodic structures. Further, the spatial terms are reintroduced and one has to examine how these terms give rise to spatially inhomogeneous solutions. The authors describe the capabilities of XPPAUT and give instructions for its use. They also use MATLAB to visualize some patterns and make all code used in the paper freely available online at https://github.com/martinrnelson/GrayScott. The targeted audience is students who have completed an introductory course on dynamical systems and bifurcation theory, have some familiarity with PDEs such as the heat equation, and have knowledge of basic numerical method techniques.

Reversible Metal Ion/Complex Binding to Chitin Controlled by Ligand, Redox, and Photochemical Reactions and Active Movement of Chitin on Aquatic Arthropods

There is strong adsorption of metal ions and their complexes to chitin, which depends on both the oxidation and complexation states of many of the said elements (whereas others display chemical reactions detectable via electrochemical methods while being retained by chitin); thus, ad- and desorption at ambient water concentrations (often in the nMol/L range) are controlled by the presence and photochemical properties (concerning Eu and probably U and Ag) of mainly biogenic organic matter (both DOC and POC, and DON). With chitin forming the outer hull of mobile organisms (animals), this biopolymer is expected to take part in metal distribution in aquatic (limnetic and riverine) ecosystems. Having studied the attachment of many different elements to both crayfish and grafted (marine shrimp) chitin, with the highest accumulations observed in Bi, V, Ni, and LREEs, one should consider secondary biochemical transformations which take place at different water and sediment levels. After chitin had been embedded into sediment, methanogenesis (which requires Ni), Bi, and Sb biomethylations and photodesorption in the illuminated water column will occur if there are appropriate organics, causing the vertical separation of Eu from other REEs, at least during the daytime. Eutrophication will enhance both the production and especially the photooxidation rates of organics in water because phosphorylated sugars and lipids are formed quantitatively within min P, which enter water and undergo Eu-mediated photooxidation much more readily. Another biopolymer, gelatin, acts as an inert matrix-enhancing organic photooxidation product via Eu, producing chemical waves, indicating autocatalysis upon light impact. From the redox-related photodesorption of metal analytes from chitin, both sensors and devices for (light-assisted) electrochemical energy conversion are being developed by our workgroup. The electrochemical determination of adsorption thermodynamics on chitin is thus directly linked to its applications in environmental monitoring and technology.

Products of catalytic oxidative coupling of methane to improve thermal efficiency in natural gas engines

Pretreating natural gas using catalytic oxidative coupling of methane (OCM) produces ethylene and ethane, both species that increase fuel reactivity, thus increasing the potential to expand the operability range of highly efficient compression ignition combustion in natural gas engines. This paper presents the first experimental results on the impact of OCM product species on engine thermal efficiency and operability range. In the work, a benchtop experiment was conducted to generate a product species distribution from OCM over a Sr/La2O3 catalyst. A computational study using known chemical mechanisms was then employed to investigate the laminar flame speed and ignition delay of the OCM-modified fuel. Finally, engine experiments in both spark-ignition and compression-ignition combustion modes were carried out using a variable compression ratio single-cylinder engine. Results from the benchtop catalyst experiments showed that practical fuel conversion for single-pass OCM resulted in 18 % methane conversion, 60 % C2 selectivity, and 10.8 % C2 yield at a molar C/O ratio of 6. After determining realistic fuel blending ratios for engine operation, the numerical simulation results showed that fuel reactivity and ignition delay improved compared to with methane alone, while laminar flame speed decreased due to higher dilution from the presence of inert OCM products. Engine experimental results confirmed that OCM products have an advantage in CI mode due to reduced ignition delay time. The CI operating range was widely expanded, and approximately 9.9% thermal efficiency gain was achieved. By contrast, efficiency in SI mode was reduced when using OCM products due to an increase in combustion duration and retarded combustion phasing.