Specific Reaction Time Research Articles

Clinical implications of interictal epileptiform discharges in cognitive functioning in CEC syndrome with evolution into epileptic encephalopathy

ABSTRACTIn epileptic encephalopathies (EE), interictal epileptiform discharges (IEDs) contribute to cognitive impairment. The EE process has been studied in a patient affected by epilepsy with occipital calcification and celiac disease (CEC syndrome) by combining the administration of brain area stimulus specific (visual and auditory) reaction times (RT) during continuous EEG monitoring with the off-line reconstruction of auditory and visual evoked potentials (EP). Visual RT and VEP were abnormal only if recorded concomitantly to the IEDs. Auditory RT and EP were normal. When the EE process is going on, IEDs transiently disrupt aspects of cortical functioning, contributing to the cognitive impairment.

Rheological study on the cure kinetics of two-component addition cured silicone rubber

The cure kinetics for two-component silicone rubber formed by addition reaction was studied by the rheological method. The influence of reaction temperature (T) on the cure kinetics was explored in detail. It was observed that the data of gel time (tgel, i.e. the time when the reaction reaches the gel point) or a specific reaction time (tnc) (defined as the reaction time before which time the influence of confinement of network on the diffusion of reaction components can be neglected) versus T obey certain functional relationship, which was well explained by the cure kinetics model of thermoset network. The cure kinetics for the two-component silicone rubber can be well fitted by the Kamal-Sourour(autocatalyst) reaction model rather than Kissinger model. When the reaction time was before or equal to tnc, the reaction order obtained by the Kamal-Sourour reaction model was 2, which was consistent with the reaction order inferred from the two components chemical reaction when the diffusion of reaction components was not influenced by the formed cross-linked polymer network. When the reaction time was larger than tnc, such as to the end of reaction (te), the influence of confinement of network on the diffusion of reaction components cannot be neglected, and the reaction order obtained by the Kamal-Sourour reaction model was larger than 2. It was concluded that the confinement effect of network had a greater influence on the cure kinetics of the silicone rubber. The reaction rate constants (kr) under different temperatures were also determined by Kamal-Sourour reaction model. The activation energy (E) for the two-component silicone rubber was also calculated from the results of lntgel, lntnc, and lnkr versus 1/T, respectively. The three values of E were close, which indicated that above analyses were self-consistent.

A promoting effect of dilution of Pd sites due to gold surface segregation under reaction conditions on supported Pd–Au catalysts for the selective hydrogenation of 1,5-cyclooctadiene

Restructuration of AuPd/CeO2 catalysts is observed during 1,5-cyclooctadiene hydrogenation, with gold surface segregation in which gold acts as a diluent of Pd surface sites. The composition of the catalyst influences the catalytic behavior, and an optimum is observed at a Pd/Au molar ratio of 0.13, as determined by X-EDS STEM. Pd–Au/CeO2 shows higher hydrogenation rates (11.2×10−5mol/gs) versus the unpromoted Pd/CeO2 catalysts (1.7×10−5mol/gs), and the Pd/TiO2 (7.5×10−5mol/gs) catalysts used as conventional hydrogenation catalysts. Since the active sites are generated under reaction conditions, characterization of the catalysts after quenching the reaction at specific reaction times was required.

Solvent‐free acetylation of lignocellulosic fibers at room temperature: Effect on fiber structure and surface properties

ABSTRACTAcetylation is one of the most interesting chemical treatments to improve the affinity of lignocellulosic fibers with polymeric matrices for the elaboration of several types of composites. In this paper, the acetylation of flax and wood pulp (bleached softwood Kraft pulp and thermomechanical pulp) fibers was carried out at room temperature in a solvent‐free system with acetic anhydride in the presence of sulfuric acid as catalyst. The effect of acetylation on the fine structure of fibers was investigated by spectroscopic methods, while the extent of acetylation was quantified by weight percent gain. The effect of reaction time on fiber morphology was studied at macro‐ and microscale using scanning electron microscopy, optical microscopy, and fiber quality analysis. The evolution of the hydrophobic/hydrophilic character of fibers was determined by contact angle measurements. The wettability of fibers by liquid epoxy resin was also evaluated to confirm the improvement of the affinity of acetylated fibers with the epoxy matrix. It was found that the hydrophilic character of fibers decrease with increasing reaction time, whereas the trend was less pronounced beyond specific reaction times. Acetylated fibers can therefore be potential candidates for replacing nonbiodegradable reinforcing materials in composite applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42247.

A Comparative Study of Specific Reaction Time in Elite Boxers: Differences between Jabs and Crosses

A Comparative Study of Specific Reaction Time in Elite Boxers: Differences between Jabs and Crosses Objective: Reaction time (RT) is the ability to react to a stimulus in the shortest time possible. Despite its importance in boxing performance, no study has investigated specific RTs in boxers executing different fighting techniques. This study compared the RT presented by elite boxers to perform two types of punches (i.e., jabs and crosses). Methods: Twenty-two athletes, members of the Brazilian national team, were positioned in front of a body opponent bag (BOB). A trigger-light device was positioned behind the BOB and connected to a sensor attached to the athletes’ gloves. After a visual stimulus, the boxers were required to hit the BOB as quickly as possible. Athletes performed ten attempts at each type of punch and the six best results were considered for further analysis. Results: Statistically significant differences were noted between jabs and crosses (p<0.001). Conclusion: Our data indicate that boxers are able to react faster when performing jabs than when performing crosses.

Coordination of adaptive working memory and reinforcement learning systems explaining choice and reaction time in a human experiment

Contemporary behavioral learning theory provides a comprehensive description of how we and other animals learn, and places behavioral flexibility and automaticity at heart of adaptive behaviors. However, to our knowledge, the computations supporting the interactions between deliberative and habitual decision-making systems are still poorly understood. Previous functional magnetic resonance imaging (fMRI) results suggest that the dorsal striatum host complementary computations that may differentially support deliberative and habitual processes [1] in the form of a dynamical interplay rather than a serial recruitment of strategies. From the same instrumental task, we develop a dual-system computational model of the two systems that can predict both performance (i.e., participant choices) and modulations in reaction times during learning. The instrumental task is a trial-and-error learning task requiring participants to find the correct associations between color stimuli and finger responses. To model the habitual system, we use a simple Q-learning algorithm (QL) [2] whose properties are fast responses, but slow convergence. For the deliberative (i.e goal-directed) system, we propose a new Bayesian Working Memory (BWM) which searches for information in the history of previous trials and stops as soon as the uncertainty on the action to perform decreases below a certain threshold. Last, we also propose a model for QL and BWM coordination. Currently, most models of system selection tend to control action selection concurrently, using either the deliberative or habitual model according to uncertainty criteria [3,4]. Only one model has investigated the relation between working memory and reinforcement learning [5] without, however explicitly modeling the temporal aspect of memory manipulation. In our approach, we propose a model for QL and BWM coordination. QL and BWM are merged such that the expensive memory manipulation is under control of, among others, the level of convergence of the habitual learning. Consequently, we also predict specific reaction times for each model that can be compared with the evolution of reaction times in instrumental learning tasks. Models are optimized for each subject with the NSGA-2 multi-objective evolutionary algorithm. The first fitness function is the Bayesian Information Criterion for individual choices. The second fitness function is also a likelihood that maximizes the probability of performing reaction times similar to humans. We compare the ability of the new model to explain human behavior with the QL or BWM only, as well as with a combination of these models based on [4], which reveals that the proposed model is in general more accurate. To conclude, we suggest that a close combination of BWM and QL better explains both choices and reaction times for most participants.

A Co-free layered LiNi0.7Mn0.3O2 cathode material for high-energy and long-life lithium-ion batteries

A Co-free layered cathode material, LiNi0.7Mn0.3O2, was synthesized using the co-precipitation method. The optimum conditions for the cathode were determined on the basis of particle size. The relationship between the cathode material’s particle size and its lithium-ion battery performance was studied on the basis of the capacity and cyclability. The LiNi0.7Mn0.3O2 material exhibited a high reversible capacity of 176mAhg−1 and a high cyclability, with 98% capacity retention after 40 cycles under the optimum conditions with a specific reaction time. A mechanism based on the structures and morphologies of the synthesized cathode materials is proposed.

2-Ethynylpyridine-Promoted Rapid Copper(I) Chloride Catalyzed Azide-Alkyne Cycloaddition Reaction in Water

The copper(I) chloride catalyzed reaction of azides with alkynes in water at room temperature was promoted by the addition of a catalytic amount of 2-ethynylpyridine, affording the corresponding 1,4-disubstituted 1,2,3-triazoles in good yields after a specific reaction time. The catalytic system could be successfully applied to electron-rich, electron-poor, and sterically crowded substrates. A study of the additive effect of pyridine derivatives revealed that alkynyl and 2-pyridyl groups were essential for activating the copper catalyst.

CO2 Sequestration through Mineral Carbonation of Iron Oxyhydroxides

Carbon dioxide sequestration via the use of sulfide reductants and mineral carbonation of the iron oxyhydroxide polymorphs lepidocrocite, goethite, and akaganeite with supercritical CO(2) (scCO(2)) was investigated using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The exposure of the different iron oxyhydroxides to aqueous sulfide in contact with scCO(2) at ∼70-100 °C resulted in the partial transformation of the minerals to siderite (FeCO(3)) and sulfide phases such as pyrite (FeS(2)). The relative yield of siderite to iron sulfide bearing mineral product was a strong function of the initial sulfide concentration. The order of mineral reactivity with regard to the amount of siderite formation in the scCO(2)/sulfide environment for a specific reaction time was goethite < lepidocrocite ≤ akaganeite. Given the presence of goethite in sedimentary formations, this conversion reaction may have relevance to the subsurface sequestration and geologic storage of carbon dioxide.

Time-resolved mid-IR spectroscopy of (bio)chemical reactions in solution utilizing a new generation of continuous-flow micro-mixers

A specially designed micro-mixer made of silicon, calcium fluoride, and silicone with an optical transmission path of 8 μm has been used for mid-IR spectroscopy monitoring of mixing-induced chemical reactions in the low millisecond time regime. The basic principle of the proposed continuous-flow technique is to mix two liquids introduced in two times two alternatingly stacked layers through diffusion at the entrance of a 200 μm wide, 1 cm long micro-fluidic channel also serving as measurement area. By using this special, dedicated arrangement, diffusion lengths and hence the mixing times can be significantly shortened and the overall performance improved in comparison to previous systems and alternative methods. Measurements were carried out in transmission mode using an Fourier transform infrared (FTIR) microscope, recording spectra with spot sizes of 180 × 100 μm(2) each at defined spots along this channel. Each of these spots corresponds to a specific reaction time: moving the measurement spot towards the entry yields shorter reaction times, moving it towards the channel's end gives longer reaction times. This principle is generic in nature and provides a solution for accurate, chemically induced triggering of reactions requiring the mixing of two liquid reagents or reagent solutions. A typical experiment thus yields up to 85 time-coded data points, covering a time span from 1 to 80 ms at a total reagent consumption of only about 125 μL. Using the fast neutralization reaction of acetic acid with sodium hydroxide as a model, the time required for 90% mixing was determined to be around 4 ms. Additionally, first experiments on ubiquitin changing its secondary structure from native to "A-state" were carried out, illustrating the potential for time-resolved measurements of proteins in aqueous solutions.

Partitioning of major and trace inorganic contaminants in fly ash acid mine drainage derived solid residues

Acid mine drainage was reacted with coal fly ash over a 24 h reaction time and species removal trends evaluated. The evolving process water chemistry was modeled by the geochemical code PHREEQC using WATEQ4 database. Mineralogical analysis of the resulting solid residues was done by X-ray diffraction analysis. Selective sequential extraction was used to evaluate the transfer of species from both acid mine drainage and fly ash to less labile mineral phases that precipitated out. The quantity of fly ash, volume of acid mine drainage in the reaction mixture and reaction time dictated whether the final solution at a given contact time will have a dominant acidic or basic character. Inorganic species removal was dependent on the pH regime generated at a specific reaction time. Sulphate concentration was controlled by precipitation of gypsum, barite, celestite and adsorption on iron-oxy-hydroxides at pH > 5.5. Increase of pH in solution with contact time caused the removal of the metal ions mainly by precipitation, co-precipitation and adsorption. PHREEQC predicted precipitation of iron, aluminium, manganese-bearing phases at pH 5.53–9.12. An amorphous fraction was observed to be the most important in retention of the major and minor species at pH > 6.32. The carbonate fraction was observed to be an important retention pathway at pH 4–5 mainly due to initial local pockets of high alkalinity on surfaces of fly ash particles. Boron was observed to have a strong retention in the carbonate fraction.

The kinetics of dithiocarbamate-mediated polyurethane-block-poly(methyl methacrylate) polymers

One important advantage offered by polymeric iniferters is the possibility that polycondensation polymers could be further reacted with vinyl monomers to produce novel block copolymers with interesting properties. The objective of this work was the kinetic investigation of polyurethane-block-poly(methyl methacrylate) (PU-b-PMMA) using dithiocarbamate (DC)-based polyurethane macroiniferter (PUMI) at different concentrations. It is shown that the copolymerization reactions followed the first order dependency. A linear increase of molecular weight with monomer conversion demonstrated that the copolymerization followed the mechanism of controlled radical polymerization. The rate of polymerization (Rp) at specific reaction time increased as the PUMI concentration increased from 0.34 × 10−3 mol/L to 2.74 × 10−3 mol/L, pass through a maxima, and decreased as PUMI concentration was increased beyond 2.74 × 10−3 mol/L. The thermogravimetric analysis showed that both PUMI and PU-b-PMMA degraded in three distinctive stages but the PU-b-PMMA is thermally more stable than the PUMI especially at lower temperatures. Thus, a combination of polycondensation and free radical photopolymerization methods, as demonstrated in this study, could be used to synthesize polyurethane-based block copolymers with tailored chain lengths of different blocks suitable for biomedical applications.

Study on Crosslinking in Diimide Reduction of Nitrile Butadiene Rubber

Abstract Acrylonitrile-butadiene rubber (NBR) in latex form was selectively hydrogenated by redox system consisting of hydrazine hydrate and hydrogen peroxide, with boric acid as catalyst. Soluble hydrogenated NBR latex was obtained; but the coagulated products were gelled on drying. This problem becomes the major obstacle for the hydrogenation technique to be commercialized. It is important to study the crosslinking reaction in the system and to solve the problem. The cause for the crosslink was investigated in three possibilities: (i) crosslinking caused by the hydrogenation of CN group; (ii) by the oxidation of C=C double bonds and (iii) by radicals in the system. The control of the crosslink was also studied. The oil resistant nitrile group —CN on the polymer chain had no change during drying process. There were no signs of carbonyl group C=O formed by oxidation and amine like groups -NH- formed by the hydrogenation of CN in HNBR gel fraction. The newly formed alkoxyl radicals were detected by ESR spectroscopy analysis in the hydrogenation system after specific reaction time. Crosslinking reaction was controlled to a large extent by using hydroquinone as gel inhibitor.

Influence of plasma treatment of carbon blacks on electrochemical activity of Pt/carbon blacks catalysts for DMFCs

In this work, in order to improve the dispersion of platinum catalysts deposited on carbon materials, the effects of surface plasma treatment of carbon blacks (CBs) were investigated. The surface characteristics of the CBs were determined by fourier transformed-infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and Boehm's titration method. The electrochemical properties of the plasma-treated CBs-supported Pt (Pt/CBs) catalysts were analyzed by linear sweep voltammetry (LSV) experiments. From the results of FT-IR and acid–base values, N 2-plasma treatment of the CBs at 300 W intensity led to a formation of a free radical on the CBs. The peak intensity increased with increase of the treatment time, due to the formation of new basic functional groups (such as C–N, C N, –NH 3 +, –NH, and NH) by the free radical on the CBs. Accordingly, the basic values were enhanced by the basic functional groups. However, after a specific reaction time, N 2-plasma treatment could hardly influence on change of the surface functional groups of CBs, due to the disappearance of free radical. Consequently, it was found that optimal treatment time was 30 s for the best electro activity of Pt/CBs catalysts and the N 2-plasma treated Pt/CBs possessed the better electrochemical properties than the pristine Pt/CBs.

Protein Folding Mechanisms Studied by Time-Resolved Electrospray Mass Spectrometry

Mass spectrometry (MS) owes its remarkable rise as a bioanalytical tool to the development of two “soft” ionization techniques: matrix-assisted laser desorption/ ionization (MALDI) (1,2) and electrospray ionization (ESI) (3). The salient feature of soft ionization is that a wide range of analytes, from small metabolites to very large biomolecular systems, can be transferred intact into the gas phase, thus making them amenable to mass spectrometric analysis. For MALDI-MS, the sample is embedded into a crystalline matrix prior to analysis. For ESI, in contrast, ionization is initiated directly from the liquid phase by spraying analyte solution from the tip of an electrically charged capillary. The small droplets formed by the ESI emitter undergo rapid evaporation and fi ssion, ultimately releasing the analyte as multiply protonated (or deprotonated) species (4).

Absorption of HCl by limestone in hot flue gases. Part I: the effects of temperature, gas atmosphere and absorbent quality

In the present work, the objective was to elaborate the chemistry of limestone and HCl in hot flue gases, especially under conditions that are typical of fluidised bed combustors. The effects of temperature, absorbent quality and particle size as well as gas atmosphere on the absorption reactions of HCl have been investigated, as have the products of chlorination. In addition, special emphasis was placed on studying the effects of molten phase formation during limestone chlorination. Experiments were performed in a laboratory using a special thermogravimetric apparatus. In the experiments, the absorption of HCl at 850 °C was found to be strongly dependent on the humidity of the flue gas. The presence of water vapour depressed the attainable conversion at a specific reaction time. Higher conversions to calcium chloride were seen at lower temperatures for the same gas atmosphere in the experiments. This was also true in the presence of CO 2, which led to the recarbonation and chlorination taking place simultaneously at 650 °C. At 850 °C, the chlorination of CaO was not affected by the presence of CO 2. At 650 °C, the concurrent recarbonation of CaO led to higher conversions for chlorination than was achieved when CO 2 was not present in the reacting gas. From the tested absorbent materials, the Nordkalk Kurevere dolomite gave the highest conversions. Furthermore, the smaller the absorbent particles, the higher the reactivities and conversions that were achieved at 650 °C. At 850 °C, the effect of particle size on the conversion of CaO was most likely interfered with by the formation of a molten product phase. This work on the absorption of HCl has shown the phenomenon to be very complex and affected by several factors that are not fully understood. Molten product phases were observed to form at both temperatures that were studied, which significantly complicated the interpretation of the experimental results.

Aqueous Oxidation of Sulfur(IV) Catalyzed by Manganese(II): A Generalized Simple Kinetic Model

The reaction kinetics of S(IV) autoxidation catalyzed by Mn(II) in the pH range 3–5 typical for atmospheric liquid water, was investigated. For reactions with pH maintained constant during the reaction course, the predictions obtained by a simple integral approach cover kinetic results only for concentrations of HSO 3 − up to 0.2 mM at pH 4.5. Thus, a generalized simple kinetic model, which can be used for predicting the reaction kinetics in wider concentration, pH and temperature ranges, was derived. This model is based on the assumption that the reaction rate is proportional to the concentration of a transient manganese-sulfito complex formed in the initial step of a radical chain mechanism. In the proposed power law rate equation $${}^{ - r}{\text{S}}({\text{IV}}) = k \cdot [{\text{MnHSO}}_{\text{3}}^{{\text{(}}a - 1{\text{) + }}} ]^2 \cdot \frac{1} {{[{\text{H}}^ + ]^{0.5} }},$$ the concentration of complex is calculated from the stability constant K and concentrations of reactants at a specific reaction time. This rate equation adequately predicts the reaction kinetics in the pH range 3–5, in the concentration ranges 0.1 ≤ [HSO 3 − ] ≤ 0.4 mM and 2 ≤ [Mn(II)] ≤ 14.6 μM. For the temperature range 15–35 °C, the estimated value for activation energy is 92.0 ± 0.1 kJ mol−1 and the Gibbs free energy of formation of the manganese-sulfito complex is −20.4 ± 0.3 kJ mol−1. Furthermore, the kinetics for catalytic reactions with pH maintained constant during the reaction course as well as with initial pH adjusted only at the start of the reaction, is described satisfactorily by the present model.

Effect of temperature on the crosslink densities of nitrile rubber and carboxylated nitrile rubber with zinc peroxide

AbstractWe studied the crosslinking of conventional nitrile rubber with metal peroxide at varying temperatures. Crosslink density, measured by swelling in the solvent until equilibrium, and the reaction rate increased with temperature, suggesting that crosslinking is a function of peroxide decomposition. At a specific reaction time, some peroxide remained in the unreacted form in the final product. This was not observed when the reaction temperature was sufficiently high to achieve total decomposition of the peroxide (190–200°C). When a carboxylated nitrile rubber was crosslinked, the same results were obtained. However, in this case, exclusively ionic or a combination of ionic and covalent crosslinks were generated, depending on the vulcanization temperature used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 335–340, 2002

Solution viscosity increase in fusion synthesis of Ca/Mg‐resinates

AbstractThe effect of Ca/Mg‐resinate concentration on solution viscosity was studied in toluene. The viscosity was observed to increase drastically above a specific concentration value. The change in viscosity dependence on concentration implies a transition from a dilute to a concentrated regime, where viscous dissipation is governed by resinate molecular interactions and excluded volume effects. The concept of critical resinate concentration, ccrit, was applied and used to explain the nonlinear solution‐viscosity increase during the resinate synthesis. Ca/Mg‐resinates were synthesized by the fusion method at 265°C in a laboratory‐scale batch reactor. During the syntheses the increase in 50 wt. % toluene solution viscosity of the resinate turned almost exponential at a specific reaction time, denoted by t50. Based on the apparent reaction kinetics, a semiempirical model with two estimated parameters was derived for the solution viscosity to be used for the prediction of the t50, time of resinate syntheses.

Preliminary Investigation of Manganese-Catalyzed Ozonation for the Destruction of Atrazine

A preliminary experimental study conducted with a conventional bubble ozonation contactor column has shown that small amounts of Mn(II) greatly enhanced the destruction of atrazine by ozone. There is an inversely linear relationship between the dosed Mn(II) concentration and the residual ozone concentration at a specific reaction time. The ozone transfer efficiency into water is greater with the increase of Mn(II) dosage. Hydrous manganese dioxide prepared by reacting permanganate with manganese sulfate, also was shown to be effective in catalyzing the destruction of atrazine by ozone. The efficiency of catalytic activity for the destruction of atrazine caused by preformed hydrous Mn(IV) is slightly lower than the case of Mn(II). A lower residual ozone value using manganese dioxide compared to the case of ozone alone suggests that ozone also may be decomposed by hydrous Mn(IV). However, a commercial MnO2 did not show any catalytic activity for atrazine destruction. The very much greater degree of atrazine oxidation by manganese-catalyzed ozonation compared to ozone alone is speculated to be the result of the generation of highly oxidative intermediate species such as hydroxyl radicals during the reaction between ozone and manganese species.