Influence of anode current density on carbon parasitic reactions during electrolysis

In the electro-deoxidation process, carbon parasitic reaction (CO₃^2- + 4e^-=C + 3O^2-) usually occurs when using carbon materials as the anode, which leads to increase of the carbon content in the final metal and decrease of the current efficiency of the process. The aim of this work is to reduce the negative effect of carbon parasitic reaction on the electrolysis process by adjusting anode current density. The results indicate that lower graphite anode area can achieve higher current density, which is helpful to increase the nucleation site of CO₂ bubbles. Most of CO₂ would be released from the anode instead of dissolution in the molten CaCl₂ and reacting with O^2- to form CO₃^2-, thus decreasing the carbon parasitic reaction of the process. Furthermore, the results of the compared experiments show that when the anode area decreases from 172.78 to 4.99 cm², CO₂ concentration in the released gases increases significantly, the carbon mass content in the final metal product decreased from 1.09% to 0.13%, and the current efficiency increased from 6.65% to 36.50%. This study determined a suitable anode current density range for reducing carbon parasitic reaction and provides a valuable reference for the selection of the anode in the electrolysis process.     

A generalized cycle life model of rechargeable Li-ion batteries

A generalized first principles based charge-discharge model to simulate the cycle life behavior of rechargeable Li-ion batteries has been developed. The model is based on loss of the active lithium ions due to the electrochemical parasitic reaction and rise of the anode film resistance. The effect of parameters such as depth of discharge (DOD), end of charge voltage (EOCV) and overvoltage of the parasitic reaction on the cycle life behavior has been quantitatively analyzed. The experimental results obtained at charge rate of 1 C, discharge rate of 0.5 C, EOCV of 4.0 V and DOD of 0.4 were used to validate the cycle life model. Good agreement between the simulations and the experiments has been achieved up to 1968 cycles. Simulation of a battery subjected to multiple cycling regimes has also been demonstrated.     

Modelling and simulation of a direct ethanol fuel cell considering multistep electrochemical reactions, transport processes and mixed potentials

In this work a one-dimensional mathematical model of a direct ethanol fuel cell (DEFC) is presented. The electrochemical oxidation of ethanol in the catalyst layers is described by several reaction steps leading to surface coverage with adsorbed intermediates (CH₃CO, CO, CH₃ and OH) and to the final products acetaldehyde, acetic acid and CO₂. A bifunctional reaction mechanism is assumed for the activation of water on a binary catalyst favouring the further oxidation of adsorbates blocking active catalyst sites. The chemical reactions are highly coupled with the charge and reactant transport. The model accounts for crossover of the reactants through the membrane leading to the phenomenon of cathode and anode mixed potentials due to the parasitic oxidation and reduction of ethanol and oxygen, respectively. Polarisation curves of a DEFC were recorded for various ethanol feed concentrations and were used as reference data for the simulation. Based on one set of model parameters the characteristic of electronic and protonic potential, the relative surface coverage and the parasitic current densities in the catalyst layers were studied.     

The oxygen evolution kinetics in sealed rechargeable NiMH batteries

The kinetics of the oxygen evolution reaction (oer) has been investigated in commercial NiMH batteries. The partial oxygen evolution currents have been determined during partial charging by measuring the charge distribution between the main electrochemical charge transfer reaction at the Ni-electrode and the parasitic oxygen evolution reaction. This enabled us to accurately determine the battery State-of-Charge during the entire charging process and to deduce information about the oxygen evolution reaction kinetics as a function of temperature. In addition, the oer kinetics has also been studied under continuous overcharging conditions. Substantial kinetic differences were observed. This has been attributed to the phase modification of nickel-oxyhydroxide induced by prolonged overcharging. The kinetic parameters of the oxygen evolution reaction have been determined, the mechanisms are discussed in detail and the relevant rate equations are derived to enable NiMH battery modelling.     

MOCVD生长GaN的反应动力学分析与数值模拟

提出了GaN生长的主反应和寄生化学反应模型,用主反应和与主反应平行进行的寄生反应来描述GaN的实际生长过程,并将此数值模拟得到的GaN沉积速率和文献中的实验数据进行了对比,发现与在实际MOCVD反应器上相同反应条件时得到的实验数据吻合较好。此外还发现TMGa浓度对GaN的生长速率有较大影响,但并非简单的线性关系。     

Current efficiency and kinetics of cobalt electrodeposition in acid chloride solutions. Part I: The influence of current density,pH and temperature

In the electrodeposition of cobalt in chloride electrolytes the evolution of hydrogen is a parasitic reaction. On a rotating platinum disc electrode the current efficiency was calculated as the charge used for anodic dissolution of cobalt at a potential where no other reactions were taking place, divided by the total cathodic charge used for cobalt deposition. The results show that the current efficiency could be measured accurately in this way. In part I the current efficiency and deposition potential are studied as a function of current density and pH. The results show an increase in current efficiency with increasing current density, pH and temperature. The results also indicate a change in the reaction mechanism for electrodeposition when the pH is changed.     

High-performance KNN piezoceramics with reproducibility and chemical stability. Part I: Solid-state reaction route

(K,Na)NbO₃-based compounds are attracting much attention for their high potential as Pb-free piezoelectric ceramics. They have, however, three major drawbacks to overcome in order to achieve a mature development: densification, reproducibility, and chemical stability. In this first part, based on standard solid-state reaction, the way to synthesize high-density homogeneous ceramics with high piezoelectric performance and chemical stability is elucidated. It relies on a low-temperature spark-plasma sintering process, after the raw materials have been finely pulverized prior to reaction. The reproducibility, however, remains a pending issue due to the unavoidable random formation of parasitic phases.     

改善锂硫电池循环性能的研究进展

综述了制约锂硫电池循环性能的因素和正极、负极、电解质对锂硫电池循环性能改善的影响。介绍了制约锂硫电池循环性能的主要因素：不可逆硫化锂的形成、硫正极多孔结构的失效和电解液组分与锂负极的副反应。分别介绍了改善锂硫电池循环性能的途径：合适的黏合剂、碳材料、正极制备工艺,锂负极保护技术,合理组分的电解质,电池结构与设计。并在此基础上对今后的发展趋势进行了展望。     

High phospholipase content of intestines of mice infected withHymenolepis nana

Infection with the tapewormHymenolepis nana results in the presence of very high amounts of phospholipase in the small intestine of the mouse. The time course and location of this response and its changes following treatment with anti-inflammatory and antiparasitic agents indicate that the enzyme accumulation is part of the reaction of the host to parasitic invasion.     

变电站寄生回路的产生及排查方法

分析目前变电站常见的几类寄生回路的特点及产生原因,并分别针对各类寄生回路提出排查的方法和具体步骤。     

Plant Parasites under Pressure: Effects of Abiotic Stress on the Interactions between Parasitic Plants and Their Hosts

Parasitic angiosperms, comprising a diverse group of flowering plants, are partially or fully dependent on their hosts to acquire water, mineral nutrients and organic compounds. Some have detrimental effects on agriculturally important crop plants. They are also intriguing model systems to study adaptive mechanisms required for the transition from an autotrophic to a heterotrophic metabolism. No less than any other plant, parasitic plants are affected by abiotic stress factors such as drought and changes in temperature, saline soils or contamination with metals or herbicides. These effects may be attributed to the direct influence of the stress, but also to diminished host availability and suitability. Although several studies on abiotic stress response of parasitic plants are available, still little is known about how abiotic factors affect host preferences, defense mechanisms of both hosts and parasites and the effects of combinations of abiotic and biotic stress experienced by the host plants. The latter effects are of specific interest as parasitic plants pose additional pressure on contemporary agriculture in times of climate change. This review summarizes the existing literature on abiotic stress response of parasitic plants, highlighting knowledge gaps and discussing perspectives for future research and potential agricultural applications.     

The lead dioxide electrode

The recent literature dealing with the redox mechanism of the lead-acid cell positive electrode is reviewed. The basis electrochemistry of lead dioxide in its various polymorphic modifications and states of subdivision is considered in relation to the important aspects of electrode technology of which the major industrial application of the material is the conventional lead-acid cell. The proposed mechanism of the reduction (discharge) of lead dioxide in various acidic solutions are considered in relation to the present state of electrode kinetic theory. The reverse reaction by which lead dioxide is formed and the parasitic intrusion of the self discharge are dealt with as a precursor to the total cyclic process. It is concluded that in a number of respects the mechanisms proposed do not adequately represent the totality of the experimental observations. Such shortcomings are emphasized and extensions to present research are proposed.     

The Effect of Virulence and Resistance Mechanisms on the Interactions between Parasitic Plants and Their Hosts

Parasitic plants have a unique heterotrophic lifestyle based on the extraction of water and nutrients from host plants. Some parasitic plant species, particularly those of the family Orobanchaceae, attack crops and cause substantial yield losses. The breeding of resistant crop varieties is an inexpensive way to control parasitic weeds, but often does not provide a long-lasting solution because the parasites rapidly evolve to overcome resistance. Understanding mechanisms underlying naturally occurring parasitic plant resistance is of great interest and could help to develop methods to control parasitic plants. In this review, we describe the virulence mechanisms of parasitic plants and resistance mechanisms in their hosts, focusing on obligate root parasites of the genera Orobanche and Striga. We noticed that the resistance (R) genes in the host genome often encode proteins with nucleotide-binding and leucine-rich repeat domains (NLR proteins), hence we proposed a mechanism by which host plants use NLR proteins to activate downstream resistance gene expression. We speculated how parasitic plants and their hosts co-evolved and discussed what drives the evolution of virulence effectors in parasitic plants by considering concepts from similar studies of plant–microbe interaction. Most previous studies have focused on the host rather than the parasite, so we also provided an updated summary of genomic resources for parasitic plants and parasitic genes for further research to test our hypotheses. Finally, we discussed new approaches such as CRISPR/Cas9-mediated genome editing and RNAi silencing that can provide deeper insight into the intriguing life cycle of parasitic plants and could potentially contribute to the development of novel strategies for controlling parasitic weeds, thereby enhancing crop productivity and food security globally.     

The influence of electrolyte composition on electrochemical ferrate(VI) synthesis. Part I: anodic dissolution kinetics of pure iron

The influence of anolyte composition and temperature on the anode dissolution kinetics of pure iron and subsequent ferrate(VI) production was studied by means of potentiodynamic voltammetry and electrochemical impedance spectroscopy. The results obtained were verified by batch electrolyses. Pure NaOH, KOH, and mixtures thereof were used as an anolyte. The motivation for this study is to understand in more detail the electrolysis process at which ferrate(VI) is electrochemically produced in situ in the solid form which is more suitable for practical utilization. A significant impact of the anolyte composition on the system behavior was indicated. It is related to the solubility of the anode dissolution products in the anolyte. It was concluded that the fast reaction kinetics in the transpassive potential region is connected with a deterioration of the ferrate(VI) synthesis efficiency. This is explained by the kinetic enhancement corresponding to the intensification of oxygen evolution as a parasitic reaction.     

7-溴-6-氯-4(3H)-喹诺酮的合成

球虫病是一种对家禽肠道有损害的寄生虫病。常山酮是一种较好的抗球虫药物,但是长期以来由于价格昂贵,限制了其在临床上的广泛应用。7-溴-6-氯-4(3H)-喹诺酮是合成抗球虫药物常山酮的重要中间体。以间氯甲苯作为起始原料,经溴化、氧化、氨化、环化共4步反应,合成了标题化合物,总收率50.61%。并用MS和1HNMR进行了结构表征。     

Cinchona Alkaloid‐Catalyzed Enantioselective Direct Aldol Reaction of N‐Boc‐Oxindoles with Polymeric Ethyl Glyoxylate

The first enantioselective direct aldol addition of N‐Boc‐oxindoles to polymeric ethyl glyoxylate is presented. The reaction is performed by using as low as 0.1 mol% (DHQ)₂PHAL and gives access to α‐hydroxycarboxylate derivatives bearing adjacent secondary alcohol and quaternary stereocenters with high levels of diastereo‐ and enantiocontrol. The use of ethyl glyoxylate in its polymeric form represents an important advantage for synthetic applications and allows us to directly install a C₂ unit ready to be converted in useful building blocks. A further one‐pot protection/deprotection sequence catalyzed by Zn(ClO₄)₂⋅6 H₂O preserved the α‐hydroxycarboxylates from racemization by means of a parasitic alcohol‐catalyzed retroaldol reaction.     

Direct electrochemical detosylation of tetratosylcyclen to cyclen with carbon cathodes

The electrochemical detosylation of tetratosylcyclen to cyclen (1,4,7,10-tetraazacyclododecane) in aprotic solvents at a carbon cathode was investigated both in a bench-scale batch electrochemical reactor and in a continuous batch recirculation reaction system equipped with a parallel-plate electrochemical cell. Yields and faradaic efficiency in cyclen, respectively, of 80 and 55% were obtained in the bench-scale reactor working in acetonitrile. It was found that the faradaic efficiency in cyclen depends on the competition between the reduction of the tetratosylcyclen and parasitic processes as the reduction of the tetraalkylammonium cations present in the supporting electrolyte. We have observed that the nature of the anolyte and catholyte and the concentrations of the substrate, the supporting electrolyte and the proton donor species dramatically influence the performances of the process.     

Inhibiting effect of oxidized zirconium on parasitic cathodic reactions in the sodium chlorate process Part I: Hypochlorite reduction

To clarify the effect of oxidized zirconium on parasitic cathodic reactions in the chlorate process, electrochemical studies were carried out at laboratory scale. The techniques used were cyclic voltammetry and recording of polarization curves. In this paper the reduction of hypochlorite ions to chloride ions was studied. It is shown that oxidized zirconium cathodes reduces the rate of hypochlorite reduction, although not entirely inhibiting it, which is mainly related to a lowered active area due to the porous layer of zirconium dioxide. Further, it has also been shown that the oxidized samples are partly passivated, giving high overvoltages for the hydrogen evolution reaction. These overvoltages gradually decrease during cathodic polarization due to the simultaneous reduction of the zirconium oxide. Studies of the selectivity indicate that hypochlorite reduction occurs on the oxidised zirconium cathodes to a high extent, the thermal oxide being somewhat better. This further proves that zirconium oxide is not a suitable cathode material for the sodium chlorate process.     

Hydrogen incorporation in Ni–P films prepared by electroless deposition

Electroless NiP films, with 12 to 16 wt % P, were deposited from a moderately acid solution. Thermogravimetric analysis indicates the presence of occluded hydrogen in the layers, which desorbs upon heating. The amount of incorporated hydrogen decreases when the pH of the solution or the nickel sulfate concentration is increased; by contrast it increases with hypophosphite concentration. Cyclic voltammetry, using an electrochemical quartz crystal microbalance, confirms the existence of parasitic reactions, namely the reduction of protons of the solvent during the cathodic process and oxidation of hydrogen during the dissolution of the layers. This behaviour is in qualitative agreement with the proposed reaction scheme.     

Influence of Ragweed (Ambrosia trifida) on Plant Parasitic Nematodes

The roots of ragweed Ambrosia trifida exude chemical compounds that have insecticidal activities. This paper reports a survey conducted in a soybean field infested with ragweed to determine if the ragweed affected the populations of plant parasitic nematodes. There was a strong indication that the ragweed decreased populations of plant parasitic nematodes in some cases.