Reactive Mechanisms Research Articles

Neurophysiological Measures of Proactive and Reactive Control in Negative Template Use.

In a visual search task, knowing features of distractors in advance leads to a more efficient visual search. Although previous studies suggested that the benefits of these negative cues rely on attentional control, it is unclear whether proactive or reactive control is involved. In this study, we analyzed the EEG data of participants performing a visual search task (n = 14). Participants searched for a shape-defined target after receiving a positive cue (target color), negative cue (distractor color), or neutral cue (non-informative). To examine proactive control, we measured EEG after the cue onset but before visual search. Our time-frequency analysis revealed a higher power of theta oscillations over frontoparietal regions after the negative cues compared with the positive and neutral cues, as well as higher theta phase synchronization within the prefrontal region, demonstrating negative cues rely more heavily on proactive control compared with other cue types. To examine reactive control, we measured EEG after the search onset. We found a lateralization of posterior alpha power toward the target side in both positive and negative cues conditions, with a later lateralization observed after negative cues. Interestingly, we observed a significant relationship between the increase of proactive theta power after negative cues and the decrease of reactive alpha power after the search. This suggests the coordination of proactive and reactive mechanisms lead to the most efficient search.

A Survey on Moving Target Defense: Intelligently Affordable, Optimized and Self-Adaptive

Represented by reactive security defense mechanisms, cyber defense possesses a static, reactive, and deterministic nature, with overwhelmingly high costs to defend against ever-changing attackers. To change this situation, researchers have proposed moving target defense (MTD), which introduces the concept of an attack surface to define cyber defense in a brand-new manner, aiming to provide a dynamic, continuous, and proactive defense mechanism. With the increasing use of machine learning in networking, researchers have discovered that MTD techniques based on machine learning can provide omni-bearing defense capabilities and reduce defense costs at multiple levels. However, research in this area remains incomplete and fragmented, and significant progress is yet to be made in constructing a defense mechanism that is both robust and available. Therefore, we conducted a comprehensive survey on MTD research, summarizing the background, design mechanisms, and shortcomings of MTD, as well as relevant features of intelligent MTD that are designed to overcome these limitations. We aim to provide researchers seeking the future development of MTD with insight into building an intelligently affordable, optimized, and self-adaptive defense mechanism.

Reactive behaviors and mechanisms of cellulose in chemical looping combustions with iron-based oxygen carriers: An experimental combined with ReaxFF MD study

Biomass energy is one of the important and feasible renewable energy resources. Chemical looping combustion (CLC) can meet the requirements of efficient CO2 capture with low energy consumption. The combination of the two factors is intuitive and important for realizing carbon neutral energy processing and conversion. Cellulose is the component with the highest content in biomass. However, there is still a lack of clear understanding of the thermal conversion behavior and microscopic reaction mechanism of cellulose in CLC. In this work, the behaviors and mechanisms of cellulose in CLC with iron-based OCs were studied systematically based on the comprehensive technics of thermo-gravimetric analysis (TGA) experiments, kinetic models and molecular dynamic simulations. The reaction behaviors, kinetic mechanism, and complex reactive networks of cellulose under complex environmental interface conditions of CLC were revealed. Three different stages were revealed for thermal weight loss and reaction behavior of cellulose in CLC via TGA. The effects of different conversion rates and reaction stages on activation energy during CLC were described based on two model-free integration methods. The dynamic evolution of the CLC process was discussed by ReaxFF MD (reactive force field molecular dynamics) simulations. A complex reaction network of cellulose depolymerization and CO2 release in CLC was obtained.

Pressure-Controlled Layer-by-Layer to Continuous Oxidation of ZrS2(001) Surface

Understanding oxidation mechanisms of layered semiconducting transition-metal dichalcogenides (TMDC) is important not only for controlling native oxide formation but also for synthesis of oxide and oxysulfide products. Here, reactive molecular dynamics simulations show that oxygen partial pressure controls not only the ZrS2 oxidation rate but also the oxide morphology and quality. We find a transition from layer-by-layer oxidation to amorphous-oxide-mediated continuous oxidation as the oxidation progresses, where different pressures selectively expose different oxidation stages within a given time window. While the kinetics of the fast continuous oxidation stage is well described by the conventional Deal-Grove model, the layer-by-layer oxidation stage is dictated by reactive bond-switching mechanisms. This work provides atomistic details and a potential foundation for rational pressure-controlled oxidation of TMDC materials.

Unraveling the Antibacterial and Iron Chelating Activity ofN‐Oxide Hydroxy‐Phenazine natural Products and Synthetic Analogs againstStaphylococcus aureus

AbstractPhenazines are redox‐active secondary metabolites produced by many microorganisms, especially by bacteria. These compounds are often produced at high cell densities in various niches.Pseudomonasstrains are the most common phenazine producers, and phenazine production in these bacteria is controlled by quorum sensing, a mechanism that enables bacteria to collectively respond to changes in cell density. As phenazines exhibit a wide range of activities against many different species, this has led to increased interest and studies related to their mechanisms of action. In this work, we have investigated and evaluated the activity of an array of phenazine‐based natural products and their analogs on Gram‐positive bacteria that share the same natural niches withPseudomonas, such as the human pathogenStaphylococcus aureus. This human pathogen plays a major role in lung infections and is often found in such infections together withP. aeruginosa. Among the screened compounds, hydroxyl‐containing phenazines with a 5,10‐dioxide scaffold were found to exhibit potent inhibitory effects on the growth ofS. aureus. The natural product iodinin (1,6‐dihydroxyphenazine 5,10‐dioxide, 6), which was chosen as a model for this class of compounds has been found to strongly chelate iron (II), thus we examined the potential role of iron starvation in suppressing the growth of this pathogen by these phenazines that are generally linked to reactive oxygen species formation mechanisms. Our results suggest that chelation of essential metals, leading to a lack of important nutrients could have a significant contribution to the antibacterial activity of these phenazines, alongside with ROS production, DNA damage and oxidative stress.

Continuous Hot‐Dip Galvanizing of Medium‐Manganese Third‐Generation Advanced High‐Strength Steels

The effects of process atmosphere oxygen partial pressure (pO2) on the preimmersion surface structures, interfacial reactive wetting products, and reactive wetting mechanisms of two prototype (0.15–0.20)C–(5.6–5.9)Mn–(0.4–1.9)Al–(1.1–1.5)Si–(0–0.6)Cr (wt%) third‐generation advanced high‐strength steels during continuous hot‐dip galvanizing are determined. In this study, the two‐stage thermal processing routes employed comprise an austenitization anneal followed by flash pickling and an intercritical anneal. All annealing treatments are conducted in a N2–5 vol% H2 process atmosphere with a controlled dew point. The substrates are austenitized at dew points of –30 or –10 °C, intercritically annealed at a dew point of –30, –10, or +5 °C, and then galvanized using a conventional 0.2 wt% Al (dissolved) bath. The preimmersion surfaces comprise a near‐pure Fe layer with dispersed nanoscaled oxide nodules. The primary reactive wetting mechanism is the direct wetting of the surface Fe, while oxide wetting, oxide cracking and liftoff, and oxide bridging by the liquid metal bath are secondary reactive wetting mechanisms. Zn ingress into the substrate via pores in the oxide network from selective dissolution during flash pickling is also noted. A well‐developed Fe2Al5–xZnx interfacial layer is observed for all metallic coating conditions. The resultant coatings show outstanding adherence after ASTM three‐point bend testing.

Wettability and Reactivity of Liquid Magnesium with a Pure Silver Substrate

For the first time, experimental data on the high-temperature interaction of liquid Mg with pure Ag are presented. The study was performed by the sessile drop method and capillary purification procedure. The test was carried out under isothermal conditions at 720 °C in a protective atmosphere of Ar + 5 wt.% H2. The solidified couple was subjected to detailed microstructural observations by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS). Under the used conditions, immediately after contact with the Ag substrate, liquid Mg drop showed a good wetting (θ0 ~ 65°) followed by fast spreading over the substrate in subsecond time to form the final contact angle of θf ~ 31°.SEM/EDS analysis showed that θf is apparent because of a deep crater (200 μm) formed in the substrate under the drop by the dissolution of Ag in liquid Mg. SEM/EDS observations of complex structural transformations in the Mg/Ag couple due to high-temperature contact and subsequent cooling are in good agreement with the Ag-Mg phase diagram. Besides substrate dissolution, the interaction between liquid Mg and solid Ag at 720 °C is accompanied with the alloying of the Mg drop with Ag and the formation of a continuous layer of the β-AgMg phase at the Mg/Ag interface. During cooling, the chemical composition of the Mg(Ag) drop continuously changes, and this process is followed by the formation of the β-AgMg phase by secondary precipitation from Ag-saturated liquid, a partial transformation of the β-AgMg to ε′-Ag17Mg54 phase by peritectic reaction, followed by the solid-state transformation of the ε′-phase to the ε-AgMg3 phase, and finally, the solidification of residual liquid in the form of the two-phase eutectic mixture of AgMg4 + (Mg). The results obtained suggest that a very good wetting and fast spreading observed experimentally for the Mg/Ag couple is caused by high reactivity between liquid Mg and Ag substrate leading to the combined effect of two reactive wetting mechanisms, i.e. through dissolutive wetting and wetting through the formation of the interfacial reaction product (β-phase).

Reactive and microbial inhibitory mechanisms depicting the panoramic view of pH stress effect on common biological nitrification

pH is a crucial factor of microbial nitrification, which often combines with high-strength ammonium to influence nitrogen removal pathway in wastewater treatment. However, the detailed inhibitory mechanisms of pH stress are not sufficiently disclosed yet. In this study, the pH stress effect on nitrification was comprehensively studied by a set of experiments which identified the reactivity of nitrification processes and activity of nitrifiers, the time dependence of inhibition effect and the hybrid pH stress effect with ammonium. The results revealed two distinct inhibitory mechanisms dominating in alkaline and acid ranges. In alkaline range (pH > 8), pH stress causes physiological damages on microorganisms which is named as microbial inhibition. It has the features of less recoverability of nitrifiers, time-dependent inhibition effect and low pH-tolerance of nitrite oxidation bacteria. Free ammonia enhanced microbial inhibition and greatly promoted nitrite accumulation. A novel reactive inhibition mechanism dominated in acid range (pH < 7) was disclosed. It only impedes ammonia oxidation process (AOP) but not impair microbial activity obviously and the effect is time-independent. The mechanism was clarified from H+ transport because AOP involved H+ production. The H+ transport was impeded under acid stress owing to the decrease of pH gradient across cell membrane. The two mechanisms formed a panoramic view of pH stress effect on nitrification advancing the understanding of nitrifier adaptability and nitritation regulation in wastewater treatment processes.

Continuous operation of fungal wheel reactor based on solid-state fermentation for the removal of pharmaceutical and personal care products

Wood-rotting fungi and their enzymatic systems represent promising biocatalysts for the removal of pharmaceuticals and personal care products (PPCPs) from wastewater. We designed a fungal wheel reactor (FWR) based on solid-state fermentation (SSF) of Trametes versicolor and a lignocellulosic substrate, which was used as an immobilization carrier for fungal biomass and the sole initial nutrient source for producing fungal oxidative enzymes. Three pharmaceutical and personal care products, acetaminophen, bisphenol A and carbamazepine, were spiked into the synthetic wastewater and the treatment was carried out under non-sterile conditions. Acetaminophen was completely removed from the FWR until laccase was observed. The acetaminophen removal efficiency was retrieved by replacing the fungal wheel with fresh SSF products. Bisphenol A and carbamazepine were removed via enzymatic activity and adsorption. When the fungal wheel was replaced, acetaminophen began to be completely removed, even after laccase depletion. The microbial community analysis indicated that the continuous removal of acetaminophen was mainly due to the high proportion of T. versicolor. The relative abundance of the co-occurring microbial community might be responsible for the divergence in acetaminophen removal between two of fungal wheel-replaced reactors. Overall, FWRs are promising tools for the removal of PPCPs by highly reactive enzymatic mechanisms as well as adsorption on the carrier surface. By replacing SSF and settled microbial communities, FWRs may continuously contribute to bioremediation over a long-term period.

Distributed control strategy for voltage and frequency restoration and accurate reactive power-sharing for islanded microgrid

For a conventional droop-controlled islanded microgrid, the poor reactive power-sharing and drop of bus voltage and frequency caused by line impedance mismatch and droop characteristics are inevitable. So far, consensus-based distributed control algorithms, in which a secondary control layer with the integration of voltage and frequency restoration and reactive power-sharing compensation mechanisms, has been treated as a promising solution. However, for most of the currently available distributed algorithms, it is the active power-sharing rather than the reactive power-sharing that was made the control goal, which is opposite to the fact that accurate power-sharing could always hold considering the integration effect in the active power control loop. Although a few recently published distributed algorithms added the reactive power-sharing goal in the second control layer, the system efficiency and reliability may deteriorate because a large circulating current could be induced at the malfunction of the communication network since there is no virtual impedance injected at the bottom control layer to limit that. This paper proposes a voltage and frequency restoration method based on the dynamic average consensus algorithm and an accurate reactive power-sharing method based on a first-order consensus algorithm and virtual impedance method. A simple pseudo-unidirectional communication network with a narrow communication band is adopted for the proposed distributed control to lower the communication burden and system complexity. The operational principle is first analyzed in detail. The proposed strategy is easily implementable and features not breaking droop characteristics. Then simulations and hardware-in-the-loop (HIL) real-time experiments verify the proposed approach.

Insights into the organic semiconducting photosensitizers for hypoxia-tolerant type I photodynamic therapy

Photodynamic therapy (PDT) is a promising approach to treat cancer and microbial infections due to its minimal invasiveness, high spatiotemporal selectivity, tissue specificity, and low toxicity. Depending on the reactive oxygen species generation mechanisms, PDT can be classified as type I and type II. To date, most reported photosensitizers are based on the type II PDT mechanism, which produces toxic singlet oxygen and requires an abundant and continuous supply of oxygen molecules. Unfortunately, in typical solid tumor microenvironments, vascular abnormalities and rapid metabolisms lead to oxygen deficiency, severely compromising type II PDT's effectiveness. To address this issue, type I PDT with less oxygen consumption has been developed as an effective way to overcome the limitations of traditional type II PDT. In this contribution, we focus on the recent advances in type I organic semiconducting photosensitizers (OSPs), including organic semiconducting small molecules, conjugated polymers, and covalent organic frameworks for advanced hypoxia-tolerant PDT. The conceptual framework and general properties of these OSPs are firstly introduced, followed by introducing OSPs with different chemical structures for type I PDT. Finally, the overall conclusion, insightful perspective, and future direction of the efforts of OSPs for advanced biological applications are outlined.

C60 fullerene attenuates muscle force reduction in a rat during fatigue development

C60 fullerene (C60) as a nanocarbon particle, compatible with biological structures, capable of penetrating through cell membranes and effectively scavenging free radicals, is widely used in biomedicine. A protective effect of C60 on the biomechanics of fast (m. gastrocnemius) and slow (m. soleus) muscle contraction in rats and the pro- and antioxidant balance of muscle tissue during the development of muscle fatigue was studied compared to the same effect of the known antioxidant N-acetylcysteine (NAC). C60 and NAC were administered intraperitoneally at doses of 1 and 150 mg kg−1, respectively, daily for 5 days and 1 h before the start of the experiment. The following quantitative markers of muscle fatigue were used: the force of muscle contraction, the level of accumulation of secondary products of lipid peroxidation (TBARS) and the oxygen metabolite H2O2, the activity of first-line antioxidant defense enzymes (superoxide dismutase (SOD) and catalase (CAT)), and the condition of the glutathione system (reduced glutathione (GSH) content and the activity of the glutathione peroxidase (GPx) enzyme). The analysis of the muscle contraction force dynamics in rats against the background of induced muscle fatigue showed, that the effect of C60, 1 h after drug administration, was (15–17)% more effective on fast muscles than on slow muscles. A further slight increase in the effect of C60 was revealed after 2 h of drug injection, (7–9)% in the case of m. gastrocnemius and (5–6)% in the case of m. soleus. An increase in the effect of using C60 occurred within 4 days (the difference between 4 and 5 days did not exceed (3–5)%) and exceeded the effect of NAC by (32–34)%. The analysis of biochemical parameters in rat muscle tissues showed that long-term application of C60 contributed to their decrease by (10–30)% and (5–20)% in fast and slow muscles, respectively, on the 5th day of the experiment. At the same time, the protective effect of C60 was higher compared to NAC by (28–44)%. The obtained results indicate the prospect of using C60 as a potential protective nano agent to improve the efficiency of skeletal muscle function by modifying the reactive oxygen species-dependent mechanisms that play an important role in the processes of muscle fatigue development.

Triterpenoids and ultrasound dual-catalytic nanoreactor ignites long-lived hypertoxic reactive species storm for deep tumor treatment

Inducing redox imbalance in cancer cells aided by external stimuli is a promising strategy to treat cancer. However, maximizing efficacious reactive species content with durable effects in deep tumors remains to be challenging. Here, we report an herbal medicine-based nanoreactor (OH7) self-assembled by oleanolic acid (OA) and two sonosensitizers. OH7 couples two cascade reactions under sonication, including dual-sonosensitizer-participated consecutive reactions for generating long-living peroxyl radical (ROO•) and OA-participated serial reactions for forming highly cytotoxic peroxynitrite (ONOO−). The site-directed reactive species burst exerts excellent cytotoxicity on two-dimensional cancer cell cultures and multicellular tumor spheroids. The high elasticity of OH7 for deep tumor transportation, the enhanced intratumoral convection by ultrasound, and the formation of ONOO− to destroy extracellular matrix jointly facilitate satisfactory penetration depth of sonosensitizers. Of note, the deep penetration and the long-lived hypertoxic reactive species generating ability can realize effective tumor inhibition by systemic administration. This study opens up new insights into the reactive species-related bioactive mechanisms to support green development of biocompatible high-performance sonocatalytic nanoreactor for potential clinical applications.

Microplastics from agricultural plastic mulch films: A mini-review of their impacts on the animal reproductive system.

Plastic mulch films (PMFs) are widely used to improve crop quality and quantity. Although they provide a range of benefits, they degrade into widespread microplastics (MPs), which can cause an unavoidable risk of environmental problems. The residue of PMFs is a significant source of MPs in soils, which can then spread into various ecosystems and be easily absorbed by organisms due to their small size, and subsequently transported through food chain. Notably, MPs have been found in the human placenta, stool and blood, raising an urgent reminder of the potential dangers of MPs to human health. This review summarizes recent studies concerning the effects of MPs on the reproductive system in soil invertebrates, aquatic animals and rodents of both sexes and the mechanisms by which MPs affect the animal reproductive system. The studies on females demonstrated that MPs decrease oocyte quantity and quality, and induce ovary fibrosis, pyroptosis and apoptosis of granulosa cells. In addition, disrupted integrity of the blood-testis barrier, damaged spermatogenesis and compromised sperm quality have been shown in most studies on male animals. The studies on the mechanisms of these effects have provided evidence that MPs act on the animal reproductive system through reactive oxygen species-related mechanisms by initiating the Wnt/β-Catenin and NLRP3/Caspase-1 pathways in females, and the Nrf2/HO-1/NF-κB, p38 MAPK and MAPK/Nrf2 pathways in males. Taken together, these studies reveal the reproductive toxicity of MPs from PMF on animals and serve as a reminder to properly dispose of PMF waste.

Reactivity of cemented paste backfill containing polycarboxylate-based superplasticizer

Superplasticizers are used in the preparation of cemented paste backfill (CPB) to improve its rheological properties. CPB produced from sulphide-bearing tailings can generate acid mine drainage (AMD), which has negative environmental impact. The AMD potential can be assessed based on the reactivity of the CPB when exposed to the atmosphere. However, the effect of superplasticizers on the reactivity of CPB is unknown. This paper presents findings from experimental investigations on the effects of polycarboxylate superplasticizers (PCSP) on the reactivity of CPB containing pyrite. The reactivity of cured CPB specimens was determined by monitoring the rate of oxygen consumption in an enclosed chamber. Microstructural tests, namely mercury intrusion porosimetry, X-ray diffraction, and thermogravimetric analyses were also carried out to have a better understanding of the reactive mechanisms. The results obtained show that the addition of PCSP leads to a proportionate reduction of reactivity. The admixture causes the refinement of the pore structure of the CPB by mainly improving binder hydration and self-consolidation. It was also observed that less pyrite crystals were present in the CPB containing the superplasticizer. High curing temperature was also found to improve binder hydration, leading to a decrease in reactivity of CPB with PCSP. Due to the micro-filer effects on the CPB pore structure, partial replacement of cement with fly ash and blast furnace slag also decreases the reactivity of CPB. These research findings will be valuable for the design of cost-effective, more environmentally friendly and sustainable CPB structures.

Very important, yet very neglected: Where do local communities stand when examining social sustainability in major construction projects?

Major construction projects are characterized by a heterogeneous audience of stakeholders who can create severe reputational risk to project organizations when not properly addressed. The inclusion and support that project organizations devote to local communities form a crucial part of a project's delivery and social sustainability considerations, yet this has only recently attracted attention in project studies. To address social sustainability, project managers should reinforce accountability and the inclusion of ‘new voices’ in the project decision-making process. Through mixed-methods research, this paper contributes to the project stakeholder engagement discourse and normative stance of stakeholder theory concerning the role of local communities and examines the ways in which inclusion can provide a response to the sustainability challenges of major projects. Findings suggest means-ends decoupling situations where current project management practices towards communities' engagement are weakly linked to their goals and induced by convergent pressures and reactive mechanisms, thus preventing an inclusive decision-making process.

Max-consensus protocol to determine the regulated node in distributed voltage regulation

Literature that deals with optimal voltage regulation in the power distribution grid often neglects the impact of communication on their control strategies or makes hard assumptions about the communication network. This paper extends a nearly optimal reactive power allocation mechanisms for distributed renewable energy sources with communication considerations and proposes a max-consensus-based communication schema to determine the regulated node in a distributed manner. The proposed consensus mechanisms is validated by co-simulation of a multi-agent system, the IEEE 906 low voltage test feeder and a simple communication simulator to evaluate the impact of message delay and communication network topology.

Monitoring, evaluation, accountability, and learning (MEAL) in anticipatory action—earth observation as a game changer

For many decades, humanitarian assistance relied on emergency response, triggering both funding and operational activities only after disaster impacts had been recorded. In recent years, many humanitarian actors have joined forces to complement traditional, reactive mechanisms with a forward-looking approach that can be activated before a disaster strikes. Anticipatory action (AA) uses forecasts of extreme weather events and combines them with risk information to identify and implement locally-led early actions with the goal of protecting lives and livelihoods more efficiently. AA is still a relatively new approach. Hence, monitoring, evaluation, accountability and learning (MEAL) is crucial to measure its effectiveness and adjust where necessary, as well as for (government) donors that want to see the added value of their investment maximized. However, evidence-based studies that investigate potential limitations and the exact impact pathway of AA at household level are time-consuming, costly, and therefore scarce. Satellite earth observation can become a game changer in AA by strengthening the evidence base via rapid, low-cost assessments. Both commercial and freely available satellite-derived data have reached an unprecedented level of quality, spatial, and temporal resolution. Simultaneously, there are major uncertainties regarding where, when, how, and under what conditions satellite data can support MEAL for AA at all. We argue that satellite data for an advanced MEAL framework should be considered already in the design phase of AA projects and that the translation of satellite data into actionable information will require a cross-cutting community of practice.

Cuticular wax removal on reactive oxygen species-related mechanisms and on the quality of Hami melon cultivars

Epicuticular wax is the outermost protective layer of fruit against abiotic stress. It is easily removed or destroyed during the postharvest transportation and handling of fruit. In this study, the effects of wax layer removal on the postharvest quality of Hami melon fruit and its possible mechanism were explored. The results showed that wax removal accelerated fruit softening, water loss, and decay, reduced sensory and nutritional quality, and shortened shelf life. At the end of storage, the antioxidant enzyme activity and non-enzymatic antioxidant content of wax-removed fruit were reduced, while the accumulation of reactive oxygen species and lipid peroxidation were accelerated. Moreover, the organelle membrane structure and plastids were destroyed. Therefore, epicuticular wax layer plays an important role in maintaining postharvest fruit quality. This study will improve our understanding of the biological function of Hami melon fruit epicuticular wax and helpful for developing effective preservation measures to delay fruit decay.

Further transformation of the primary ozonation products of tramadol- and venlafaxine N-oxide: Mechanistic and structural considerations

Ozonation has been used to effectively remove micropollutants from the secondary effluent in several wastewater treatment plants. It is known that ozonation transforms tertiary amine compounds into their respective N-oxides, however in an earlier study a mass balance could not be closed at elevated ozone concentrations, leading to the assumption that more ozonation products are possible. This study was conducted to elucidate which (hitherto unknown) ozonation products can be formed from venlafaxine and tramadol when ozonating wastewater. Ozonation experiments were performed with tramadol and venlafaxine N-oxide in two different set-ups. Both tramadol- and venlafaxine N-oxide degraded during ozonation in pure (deionized) water in both semi-continuous and batch mode ozonation set-ups. 13 and 17 new transformation products were detected from tramadol- and venlafaxine N-oxide respectively, using high resolution mass spectrometry with ESI(+) ionization. Empirical chemical formulas were proposed based on the determination of the exact masses and interpretation of the product ion spectra. These transformation products result from the addition of one to three oxygen atoms and removal of C, –CH2, C2H2, C3H6, etc., from the parent molecule, respectively. Quenching experiments suggested that most of the transformation products originated from the direct reaction with ozone (eight for tramadol N-oxide and ten for venlafaxine N-oxide), whereas fewer products originated from the reaction with OH radicals (three for tramadol N-oxide and three for venlafaxine N-oxide). Reaction mechanisms and chemical structures of products are proposed, based on the available active sites and past literature on ozone reaction mechanisms. The experimental results are compared to theory and literature on ozone reactive sites and ozone reaction mechanisms. All in all this shows that there can be multiple ozonation products, and ozonation pathways can be complex, even if initially only one ozonation product is formed.