Extent Of Reaction Research Articles

Zeolitization of a devitrified high-silica rhyolitic tuff producing dachiardite: A comparison of hydrothermal experiments with the corresponding reaction progress modeling

We have investigated the hydrothermal alteration of polished wafers of tuff reacted with dilute groundwater at 90 °C, 150 °C and 250 °C for time periods ranging from 2 months to nearly 1 year. The polished rock wafer provided a convenient surface upon which to grow secondary minerals. Reaction product minerals were identified and analyzed at the end of each experiment and, along with the evolving fluid chemistry, were compared to computational results from corresponding reaction progress models.At 250 °C after a few months the run products in the experiment were dominantly the mordenite group zeolite minerals: dachiardite (a Ca-rich variety) and mordenite, itself. At 150 °C after a few months of reaction only minor amounts of clay were produced, but after 1 year of reaction at this temperature both mordenite group zeolites were again present. At this lower temperature the total amount of run products was much smaller. At 90 °C no run products could be seen at all, even after 1 year of reaction. The reaction progress modeling results for reaction products were in good relative agreement with the experimental results.The higher the temperature, and the greater the extent of reaction, the better the fluid phase modeling results agreed with the actual experimental results. At 250 °C the agreement was good for nearly all elements. At 150 °C agreement for pH, SiO2, Na and K were good, but less good for Al, Mg and Ca, especially after short reaction times. At 90 °C agreement for pH, SiO2 and Na was reasonable, but not as good for the other elements, and all modeling results for short reaction times did not match experimental results as well as the longer time results.This study demonstrates that reaction progress modeling provides a powerful tool for predicting hydrothermal rock-water interactions, with results expected to improve, as more and better quality thermodynamic and kinetic data become available and as process-oriented simulators incorporate better and more comprehensive sub-models for mineral dissolution and growth.

Electrospinning of epoxy fibers: Effect of curing conditions on solution rheological behavior

AbstractThe electrospinning of thermoplastic polymers is widely used in applications such as filters and coatings, but has only recently been applied to thermosetting polymers because of their chemical structure and reactivity. Epoxy is a thermosetting polymer which, when combined with a curing agent, chemically reacts to form a crosslinked matrix. In the present study, we demonstrate that to electrospin epoxy and obtain continuous micro and nanofibers, one must precisely control the curing reaction. Epoxy was mixed with triamine curing agent and, to enable electrospinnability, was dissolved in a mixture of tetrahydrofuran and dimethylformamide solvents. We identified a narrow working window wherein a proper solution for electrospinning is close to the gel point, right before the transition from liquid to solid gel state. The solution was characterized by means of (i) Fourier‐transform infrared spectroscopy to monitor the extent of reaction, (ii) steady shear viscosity to detect the divergence near the gel point, and (iii) oscillatory loss and storage shear moduli to identify the liquid‐to‐gel transition. Based on these measurements, it was possible to monitor the chemical transformations that the epoxy solution underwent with time, such as chemical interconnections and gelation, and thus define the working window for electrospinning.

Superior performance of catalytic ozonation on molecular-level transformation of effluent organic matter and self-cleaning property in catalytic ozonation membrane reactor

Catalytic ozonation membrane reactor (COMR) is one of the most promising technologies for municipal wastewater reclamation. Herein, we evaluated superior performance of catalytic ozonation in COMR through filtration of effluent organic matter (EfOM) using the origin and three catalytic membranes. We found that filtration primarily contributed to rejection of protein-like fluorescence enriched in relatively high-oxygen compounds (O/C >0.4) with high molecular weight and catalytic ozonation further removed humic-like materials and highly unsaturated, aromatic and reduced compounds (O/C<0.4; H/C<1.3), demonstrating complementary function of catalytic ozonation and filtration. The superior performance of catalytic ozonation than ozonation is reflected in higher removal of medium molecular weighted humic-like materials and S-containing compounds, enhancing the mineralization and reaction extent of EfOM. Additionally, catalytic ozonation exhibited strong self-cleaning property and eliminated irreversible membrane fouling. Our findings provide molecular-level insights into the reaction mechanism governing the COMR towards municipal wastewater reclamation.

The deposition kinetics of barium sulphate scale: model development

The deposition kinetics of barium sulphate scale: model development

Numerical study of the dehydration and hydration processes of the Ca(OH)2/CaO system in an indirect-direct reactor

Energy storage is important for the application of the discontinuous and unstable renewable energy. The CaO/Ca(OH)2 thermochemical system of high energy density and little heat lose is promising for thermal energy storage, yet the heat and mass transfer processes related to dehydration reaction needs further improvement and the regulation manner related to the hydration reaction needs further investigation. In this work, a hybrid indirect-direct reactor of the CaO/Ca(OH)2 system is proposed with the physicochemical model developed to study the dehydration and hydration processes under different operating and structural conditions, and five indicators are defined to evaluate the overall reaction performance. During the dehydration process, the reactant is indirectly heated by the electrical heater at the reactor outside wall and the reaction proceeds in radial direction which is mainly limited by the poor heat transfer, leading to low energy storage efficiency of 6.1 %. The increase of reactant thermal conductivity and application of high-thermal-conductivity porous channel greatly enhance the heat transfer leading to significant reduction of reaction time and increase of energy storage efficiency up to 25.63 %. During the hydration process, the gas mixture directly contacts and reacts with solid reactant and the reaction proceeds in axial direction with reaction region of “U” shape which is mainly restricted by the reaction equilibrium. The thermal power density and reaction temperature of the hydration process can be regulated by the inlet mass flow rate and the inlet steam mass fraction respectively. The increase of inlet mass flow rate and inlet steam mass fraction leads to higher heat exchange efficiency at the same reaction extent and shorter hydration reaction time. The present study demonstrates the superiority of the indirect-direct type reactor and the performance of which can be further improved by optimizing the geometrical and operating conditions.

Critical Review on Bromate Formation during Ozonation and Control Options for Its Minimization.

Ozone is a commonly applied disinfectant and oxidant in drinking water and has more recently been implemented for enhanced municipal wastewater treatment for potable reuse and ecosystem protection. One drawback is the potential formation of bromate, a possible human carcinogen with a strict drinking water standard of 10 μg/L. The formation of bromate from bromide during ozonation is complex and involves reactions with both ozone and secondary oxidants formed from ozone decomposition, i.e., hydroxyl radical. The underlying mechanism has been elucidated over the past several decades, and the extent of many parallel reactions occurring with either ozone or hydroxyl radicals depends strongly on the concentration, type of dissolved organic matter (DOM), and carbonate. On the basis of mechanistic considerations, several approaches minimizing bromate formation during ozonation can be applied. Removal of bromate after ozonation is less feasible. We recommend that bromate control strategies be prioritized in the following order: (1) control bromide discharge at the source and ensure optimal ozone mass-transfer design to minimize bromate formation, (2) minimize bromate formation during ozonation by chemical control strategies, such as ammonium with or without chlorine addition or hydrogen peroxide addition, which interfere with specific bromate formation steps and/or mask bromide, (3) implement a pretreatment strategy to reduce bromide and/or DOM prior to ozonation, and (4) assess the suitability of ozonation altogether or utilize a downstream treatment process that may already be in place, such as reverse osmosis, for post-ozone bromate abatement. A one-size-fits-all approach to bromate control does not exist, and treatment objectives, such as disinfection and micropollutant abatement, must also be considered.

Electrolytes in Multiple-Phase Hydrogen Storage Reactions

Multiple-phase hydrogen storage materials such as metal alanates and borohydrides, and destabilized systems offer the possibility of high hydrogen storage capacity with favorable thermodynamics. However, the multiphase nature of these materials intrinsically limits the kinetics due to the required transport of species between phases, which are typically in dry powder form. To address this limitation, the influence of added electrolytes is explored. This approach is motivated by analogy with similar multiphase battery reactions that show reduced kinetic limitations while necessarily containing electrolytes. Previous experimental results showing improved kinetics for MgH2/Sn (using a LiBH4/KBH4 eutectic electrolyte) and NaAlH4 (using a diglyme electrolyte) are further analyzed in terms of this analogy. The results show that the analogy is useful and rate constants are increased. Importantly, the inclusion of an electrolyte also appears to alleviate the continuously decreasing rates with the extent of reaction, which is characteristic of many multiphase hydrides. Instead, reaction rates are approximately constant until near completion. Together, these effects can lead to &gt;10× shorter overall reaction times. In addition, new results are presented for the hydrogenation of MgB2 using Li/K/CsI and Li/K/CsCl eutectic electrolytes, where &gt;60% conversion to Mg(BH4)2 was demonstrated at 350 bar.

High‐Contrast Optical Nitrile‐Rich Molecular Switches: Synthesis of Pyrrol‐2‐ones Containing a Butadienetricarbonitrile Fragment and Kinetics of Their Reversible Interaction with Morpholine

AbstractDirect synthesis of previously undescribed 5‐aryl‐substituted pyrrol‐2‐one derivatives containing a butadienetricarbonitrile (BDTC) acceptor was carried out. The kinetics of their reversible interaction with morpholine accompanied with high‐contrast color changes in acetonitrile solution was studied for the first time. It was found that the electronic effects of substituents in aromatic ring had a direct effect on the reaction rate and extent, that was supported by the observed linearity between the estimated equilibrium constants and the electrophilic Hammett constants.

In situ H2 O2 Generation by Choline Oxidase and Its Application in Amino Polysaccharide Degradation by Coupling to Lytic Polysaccharide Monooxygenase.

Chitin, the most abundant amino polysaccharide in Nature, has many applications in different fields. However, processing of this recalcitrant biopolymer in an environmentally friendly manner remains a major challenge. In this context, lytic polysaccharide monooxygenases (LPMOs) are of interest, as they can act on the most recalcitrant parts of chitin and related insoluble biopolymers such as cellulose. Efficient LPMO catalysis can be achieved by feeding reactions with H2 O2 , but careful control of H2 O2 is required to avoid autocatalytic enzyme inactivation. Herein, we present a coupled enzyme system in which a choline oxidase from Arthrobacter globiformis is employed for controlled in situ generation of H2 O2 that fuels LPMO-catalyzed oxidative degradation of chitin. We show that the rate, stability and extent of the LPMO reaction can be manipulated by varying the amount of choline oxidase and/or its substrate, choline chloride, and that efficient peroxygenase reactions may be achieved using sub-μM concentrations of the H2 O2 -generating enzyme. This coupled system requires only sub-stoichiometric amounts of the reductant that is needed to keep the LPMO in its active, reduced state. It is conceivable that this enzyme system may be used for bioprocessing of chitin in choline-based natural deep eutectic solvents.

Proteomic Characterization of Native and Rearranged Disulfide Bonds in Proteins from Thermally Treated and Commercial Milk Samples.

To investigate thiol-disulfide interchange reactions in heated milk yielding non-native intramolecular rearranged and intermolecular cross-linked proteins, a proteomic study based on nanoLC-ESI-Q-Orbitrap-MS/MS and dedicated bioinformatics was accomplished. Raw milk samples heated for different times and various commercial dairy products were analyzed. Qualitative experiments on tryptic digests of resolved protein mixtures assigned the corresponding disulfide-linked peptides. Results confirmed the limited data available on few milk proteins, generated the widest inventory of components (63 in number) involved in thiol-disulfide exchange processes, and provided novel structural information on S-S-bridged molecules. Quantitative experiments on unresolved protein mixtures from both sample typologies estimated the population of molecules associated with thiol-disulfide reshuffling processes. Disulfide-linked peptides associated with native intramolecular S-S bonds generally showed a progressive reduction depending on heating time/harshness, whereas those related to specific non-native intramolecular/intermolecular ones showed an opposite quantitative trend. This was associated with a temperature-dependent augmented reactivity of definite native protein thiols and S-S bridges, which determined the formation of non-native rearranged monomers and cross-linked oligomers. Results provided novel information for possibly linking the nature and extent of thiol-disulfide exchange reactions in heated milk proteins to the corresponding functional and technological characteristics, with possible implications on food digestibility, allergenicity, and bioactivity.

The extent of reaction traced by determination of N2 content for synthesised cationic biodegradable polymer flocculant

AbstractBiodegradable “green” and safe substitutes to minimize environmental and health risks are drawing extensive attention for research interest. This research aims to create a water‐soluble cationic starch‐grafted biodegradable polymer that can be used as a flocculant. As polymers are strong molecules that carry charges, they are effective flocculants. Saturated polymer chains do not change the pH value on adding to wastewater. The reactive groups of the starch, i.e., hydroxyls, form a complex with cations present in the reagent. According to the proposed strategy outlined in the research, the mechanism of free radical graft copolymerization of ethyl monomers onto starch should proceed as expected. In presence of molecular nitrogen, H+ may be replaced by reactive group R, i.e., CH2CH2N (Et3) (triethylamine) in a highly alkaline medium. During the work, it was observed that starch‐based flocculant exhibits a high degree of cationic charge. Developed cationic flocculant performs well in a liquid dispersion form, is fast‐acting and effective, and is suitable for treating industrial wastewater. It combines low sludge formation with cost‐effectiveness. The paper will discuss important practical considerations to increase the %N2 by changing the reaction parameters of the polymer produced and its effect on flocculation efficiency.

Effect of deacetylation of chitosan on physicochemical properties, antioxidant and antibacterial activities of chitosan-mannose derivatives.

This paper investigates the physical, chemical, and antibacterial properties of water-soluble chitosan derivatives. Preparation of the water-soluble chitosan derivatives was done by the Maillard reaction (MR) between chitosan (the degree of deacetylation (DD) being 50%, 70%, and 90%) and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan-mannose Maillard reaction products (Mc-mrps) were carried out. Based on the experimental data obtained from the Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Pyrolysis-gas chromatography-mass analysis (PY-GC-MS), and 1H-NMR, the Mc-mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△E), and solubility (p<0.05). The zeta potential and particle size of the Mc-mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram-positive (S.aureus and Bacillus subtilis) and Gram-negative bacteria (E.coli and Salmonella typhimurium) as well as antioxidant activity were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan. The results of the study suggest that chitosan was derived with mannose to yield a novel, water-soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc-mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. This article is protected by copyright. All rights reserved.

Covalent Adduct Formation between β-Lactoglobulin and Flavor Compounds under Thermal Treatments That Mimic Food Pasteurization or Sterilization.

Thermal processing (e.g., pasteurization and sterilization) is a critical step ensuring the microbial safety of our foods. Previous work from our laboratory has examined the covalent reactions occurring between proteins and a broad selection of flavor compounds under ambient storage temperatures (25-45 °C). However, similar research on reactions of flavor compounds with a protein under thermal processing conditions has not been investigated. In the current study, covalent adduct formation between β-lactoglobulin (BLG) and 46 flavor compounds encompassing 13 different classes of functional groups was investigated under pasteurization and sterilization conditions by UPLC-ESI-QTOF-MS. BLG was chosen as a representative protein for this study because it is structurally well characterized, its molecular weight is well suited for ESI-MS analysis (18.2 kDa), and it is broadly used in the food industry. Schiff base, aza-Michael addition, and disulfide linkages were the main types of covalent interactions occurring across the reactive samples. Among them, isothiocyanates, aldehydes, and thiol-containing compounds were generally very reactive. Increasing the severity of the thermal treatment [high-temperature-short-time (HTST) pasteurization, in-container pasteurization (IC), and ultra-high-temperature (UHT) sterilization conditions] accelerated the reactions of BLG with flavor compounds, which revealed reactivity of three flavor compounds not previously observed to react at room temperature (eugenol, 4-vinyl phenol, and 3-nonen-2-one). Ketones [other than 2-hydroxy-3-methyl-2-cyclopenten-1-one (cyclotene), diketones, and unsaturated ketones], alcohols, acids, alkenes (terpenes), esters, lactones, 3-acetylpyridine, methyl anthranilate, vanillin, 2-methylthiophene, and dimethyl sulfone did not show measurable reactivity with BLG under the thermal processing conditions examined. An overall view of the data shows that the HTST heat treatment (72 °C for 15 s) had the least effect on the extent of reaction while in-container pasteurization conditions (63 °C for 30 min) produced a similar extent of reaction as the UHT (130 °C 30 s) heat treatment. These varying extents of adductation are in reasonable accord with what one might expect, given that the rates of most classes of chemical reactions occurring near ambient temperature increase by a factor of 2-4 for each increase of 10 K in temperature. Unfortunately, our methodology did not permit us to obtain meaningful data using the most aggressive standard sterilization thermal conditions (110 °C for 30 min) because extensive aggregation/coagulation removed essentially all of the BLG protein from the reaction mixtures prior to MS analysis.

Sulfide Immobilization: Investigating the Impact of a Protective Sulfide-Bearing Layer Formed by Siderite (FeCO3)

Sulfate-rich wastewater poses ecological hazards to freshwater ecosystems, and sulfate is highly regulated in many Minnesota lakes. Biological sulfate reduction results in the reduction of sulfate to sulfide, and this process is used to remediate acid mine drainage. Theoretically, the aqueous sulfide can be immobilized into a solid-phase material and removed from the aqueous system. This study focuses on sulfide immobilization using iron-bearing waste minerals. Specifically, the extent of reaction of siderite (FeCO3), an abundant ferrous mineral in some mining wastes, with sulfide was studied. Mildly acidic batch reactors containing powdered siderite were consecutively injected with a sodium sulfide solution. Solid reaction products were identified and characterized using powder X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Mackinawite (FeS) appeared to be the most abundant product, with greigite (Fe3S4) also detected. Results reveal that the immobilization capacity of sulfide by siderite is limited by the concentration of the Fe2+(aq) presented in the system immediately before the initial sulfide exposure as the Fe2+(aq) levels are not replenished after sulfidation. These results improve our understanding of the sulfidation of siderite and provide insight to improve the viability of using siderite-containing mining waste rock in a sulfate remediation technology.

Simultaneous rheology and cure kinetics dictate thermal post-curing of thermoset composite resins for material extrusion.

Thermoset composites are excellent candidates for material extrusion because they shear thin during extrusion but retain their shape once deposited via a yield stress. However, thermal post-curing is often required to solidify these materials, which can destabilize printed parts. Elevated temperatures can decrease the rheological properties responsible for stabilizing the printed structure before crosslinking solidifies the material. These properties, namely the storage modulus and yield stress, must therefore be characterized as a function of temperature and extent of reaction for various filler loadings. This work utilizes rheo-Raman spectroscopy to measure the storage modulus and dynamic yield stress as a function of temperature and conversion in epoxy-amine resins with fumed silica mass fractions up to 10 %. Both rheological properties are sensitive to conversion and particle loading, but only the dynamic yield stress is reduced by elevated temperatures early in the cure. Notably, the dynamic yield stress increases with conversion well before the chemical gel point. These findings motivate a two-step cure protocol that starts at a low temperature to mitigate the drop in dynamic yield stress, then ramps up to a high temperature when the dynamic yield stress is no longer at risk of decreasing to rapidly drive conversion to near completion. The results suggests that structural stability can be improved without resorting to increasing filler content, which limits control over the final properties, laying the groundwork for future studies to evaluate the stability improvements provided by the multi-step curing schedules.

Transition Metal-Promoted Mg-Fe Mixed Oxides for Conversion of Ethanol to Valuable Products.

The conversion of ethanol into petrochemicals, such as ethyl and butyl acetate, butanol, hexanol, and so forth was studied. The conversion was catalyzed by Mg-Fe mixed oxide modified with a second transition metal (Ni, Cu, Co, Mn, or Cr). The main aim was to describe the influence of second transition metal on (i) the catalyst itself and (ii) reaction products such as ethyl acetate, butanol, hexanol, acetone, and ethanal. Moreover, the results were compared with the results of pure Mg-Fe. The reaction was carried out in the gas phase in a flow reactor with a weight hour space velocity of 4.5 h-1 for 32 h at three reaction temperatures (280, 300, and 350 °C). The metals Ni and Cu in Mg-Fe oxide enhanced the ethanol conversion due to the population of active dehydrogenation sites. Despite the lower acido-basicity, Cu, Co, and Ni supported the yield of ethyl acetate, and Cu and Ni also promoted the yield of higher alcohols. Ni was related to the extent of the gasification reactions. Moreover, long-term stability (by leaching of metals) test was carried out for all catalysts (128 h).

Household-scale treatment units for reductive removal of hexavalent chromium from groundwater

Legacy chromium-laden hazardous industrial solid waste has been a major reason for severe groundwater pollution in low-to-middle income countries, often impacting marginalized communities who lack access to centralized water treatment solutions for their potable needs. This study aimed to develop low-cost, simple-to-adopt, and robust decentralized treatment units for total Cr removal using methods that do not generate toxic sludge post-treatment. The research involved a systematic comparison of the extents and rates of Cr (VI) reduction in groundwaters using ferrous iron (Fe (II)) for chemical coagulation (CC) with Fe (II) sulphate and for electrocoagulation (EC) with iron electrodes in batch experiments over a range of Cr (VI) (1.5–13 mg L−1) and Fe(II) (3–42 mg L−1) concentrations. While complete Cr removal was achieved by CC within 5 min, the extent of Fe(II)-Cr(VI) reaction depended on initial Fe(II) dosage. In contrast, the reaction kinetics of EC was controlled by initial Cr(VI) concentration and Fe(II) dosing rate, with the extent of reaction determined by the duration of current applied. Time-dependent Cr(VI) and Fe(II) concentrations in groundwater were modelled using rate equations and constants derived from past studies performed on simpler matrices. Subsequently, treatment units that combined either CC- or EC-based Cr(VI) reduction with sand filtration, to remove generated Fe(III)-Cr(III)-oxyhydroxide colloids, were built to obtain potable groundwater. Efficiencies of Cr(VI) removal from spiked and real-contaminated groundwaters by CC- and EC-based treatment units were ~98 % and >99 %, respectively. Although EC-based unit was more efficient than CC-based unit for groundwaters with initial Cr(VI) >4 mg L−1, it exhibited longer treatment time. The costs of treated water for EC and CC were estimated to be USD 0.05 and USD 0.13 per 100 L, respectively. Results indicated that point-of-use decentralized Cr(VI) treatment units could be a promising solution for marginalized communities.

Catalytic cracking of heavy atmospheric gas oil to light olefins over ZSM-5 zeolite: Effect of crystal size in the absence/presence of steam

The catalytic cracking of heavy atmospheric gas oil (AGO) has been investigated to study the effect of ZSM-5 zeolite crystal size on the selectivity to light olefin in the absence and presence of steam. Dodecane (used as model compound) and heavy AGO feed streams were utilized to study the influence of changing pore shape selectivity when comparing cracking performance by nano and micro ZSM-5 zeolites. The zeolites were characterized using BET, XRD NMR, NH3-TPD and Py-FTIR. In the presence of steam, the short pores length nano ZSM-5 crystals showed enhanced catalytic cracking activity and selectivity to light olefins. The nano ZSM-5 catalyst promoted higher selectivity to light olefins through β-scission while reducing the extent of hydrogenation reactions towards the formation of liquefied petroleum gas components (LPG). In contrast, the long pores length of micro ZSM-5 tended to favor the production of more naphtha, kerosene and LPG through hydrogen transfer routes, resulting in lower selectivity to light olefins. The resulting propylene/ethylene (P/E) ratios were altered by the type of feed used, cracking reaction temperature, influence of steam and catalyst crystal size. Specifically, higher P/E ratio was achieved over nano ZSM-5 zeolite, especially with the cracking of heavy AGO feed in the presence of steam, due to an increase of monomolecular reactions through β-scission cracking mechanism.

Retirement from elite sport and self-esteem: a longitudinal study over 12 years.

This study examined the complex associations between athletic retirement and self-esteem among former elite athletes. With reference to theoretical and empirical work on the quality of the transition out of sport, information was collected from 290 (junior) elite athletes in a retrospective-prospective design: at the first measurement, active athletes assessed satisfaction with their sporting career, athletic identity, and self-esteem. At the second measurement (12 years later), the now former athletes rated transition characteristics of their career ending, sporting career success, emotional reactions to career termination, extent of necessary adjustment required following athletic retirement, duration and quality of adjustment, and self-esteem. Structural equation modelling revealed that neither sporting career success nor sporting career satisfaction had a direct effect on adjustment. However, athletic identity and retirement planning predicted the extent of adjustment, which in turn predicted the duration and quality of adjustment, and ultimately self-esteem. Voluntariness, timeliness, and perceptions of gain predicted emotional reactions towards career termination, which also predicted the duration of adjustment. Extent of adjustment and emotional reactions mediated between preconditions of career termination and transition characteristics and self-esteem. While self-esteem after career termination was predominantly predicted by self-esteem 12 years earlier, perceived quality of adjustment to career termination had a significant effect on self-esteem in the post-athletic career. These results complement existing literature illustrating that athletic retirement is a complex and dynamic process and the quality of this transition has a small, but still noteworthy effect on self-esteem, a central construct for well-being.

Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

Formation behaviors of rod-like reactive shaped charge penetrator (RRSCP) and their effects on damage capability are investigated by experiments and numerical simulations. The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used. Three types of spherical-segment aluminum-polytetrafluoroethylene-copper (Al-PTFE-Cu) reactive liners with Cu contents of 0%, 46.6%, and 66% are fabricated and tested. The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect, but the tail skirts disappear over time. Moreover, rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact. From simulation analysis, the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning, forming a leading reactive penetrator and a following chemical energy cluster. The unique formation structure determines the damage modes of the aluminum plate and the steel plate. Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content. With increasing Cu content, the velocity, activation extent, and reaction extent of Al-PTFE-Cu RRSCP decrease, which contribute to elongation and alleviate the negative effects of chemical reactions on elongation, significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration. However, the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.