Reaction Time Values Research Articles

Differences in Neurocognitive Functions Between Healthy Controls and Anterior Cruciate Ligament-Reconstructed Male Athletes Who Passed or Failed Return to Sport Criteria: A Preliminary Study.

Only 55% of anterior cruciate ligament-reconstructed (ACLR) athletes return to competitive sports. This brings into question the usefulness of current return to sport (RTS) criteria. High cognitive demand of sport environment clarifies the value of incorporating neurocognitive tests when making decisions regarding the time of RTS. This preliminary study aimed to compare the neurocognitive functions between healthy controls and ACLR male athletes who passed or failed RTS criteria. A total of 45 male football players, including 15 ACLR who passed RTS criteria, 15 ACLR who did not pass, and 15 healthy controls participated in this cross-sectional study. The Cambridge Neuropsychological Test Automated Battery was used to measure a battery of neurocognitive tasks, including speed of response, sustained attention, working memory, cognitive flexibility, and response inhibition. The results revealed that compared with both the ACLR-passed and healthy groups, the ACLR-failed group showed greater values of 5-choice movement time (P = .02, P = .01, respectively) but lower values of stop signal reaction time (P = .03, P = .001, respectively) and proportion of successful stops variables (P = .02). In addition, compared with the healthy group, both the ACLR-failed and ACLR-passed groups indicated greater values in between errors (P < .001, P = .008, respectively) and reaction latency variables (P = .002, P = .01, respectively) but lower values of A' (P < .001, P = .007, respectively), probability of hit (P < .001, P = .03, respectively), and percent correct trials variables (P = .006, P = .02, respectively). Our findings indicated deficits in neurocognitive functions in ACLR male athletes. In addition, poor performance in sustained attention, working memory, and cognitive flexibility measures observed in the ACLR-passed group highlighted the necessity for using a multimodal approach via implementation of neurocognitive measures in conjunction with the functional and muscular assessments when making RTS decisions.

Alkali leaching in dissolved oxygen for efficient desulphurization of low-grade Lakhra coal

ABSTRACT Coal is still a great source of energy, but its high sulfur content causes environmental pollution and problems in its processing. This study used a method of combined oxidation and alkali leaching to desulfurize low-grade, high-sulfur Lakhra coal at different ranges of temperature, alkali concentration, leaching time, partial pressure of oxygen, and agitation speed. The optimum values for the leaching reaction were observed to be an alkali (NaOH) concentration of 0.8 mM, a leaching time of 1.5 h, an oxygen partial pressure of 150 psi, and an agitation speed of 800 rpm. The ash content of the coal initially increased at higher values of reaction time and temperature, and then became saturated at a certain peak. The raw coal was characterized for ultimate and proximate analysis, and the product was characterized for ash content and total sulfur content.

Дослідження реакції таеквондистів на об’єкт, що рухається

Purpose: to define features of reaction to a moving object in taekwondo. Material and Methods. The following research methods were used: analysis of scientific and methodological literature and Internet sources; pedagogical observation; psychophysiological measurements; methods of mathematical statistics. Results: the use of non-parametric Mann-Whitney criterion confirmed that the average reaction time for the whole test in older sportsmen is significantly better than in junior sportsmen by 31,39 % (U=5, p&lt;0,01). When analyzing the directionality of the processes of excitation or inhibition, it was found that older athletes had better reaction accuracy than junior athletes (U=10,5, p&lt;0,05). In both groups sportsmen reacted mainly prematurely, but junior taekwondoists reacted prematurely more often by 17,66 % (U=4, p&lt;0,01). According to Spearman's correlation coefficient between the age of sportsmen and the obtained indicators of measurement the following results were obtained: between reaction time and age in the 1st group r=0,26, in the 2nd group r=-0,37 (p&gt;0,05), between exact reactions and age in the 1st group r=0,32, in the 2nd group r=0,68 (p&lt;0,05). According to the analysis of the results of the second measurement, there is no sufficient evidence that the average values of reaction time in both groups before and after the competition are different. After the competition, the accuracy of reactions in sportsmen from group 1 is lower by 31,1 % than before the competition (U=11, p&lt;0,05). In group 2 there were no statistically significant differences between the indicators of reaction accuracy before and after competitions. The U-criterion did not show statistically significant difference between the direction of processes of excitation and inhibition in group 1 and group 2 before and after competitions. In the 1st group Spearman's coefficient testifies to the absence of statistically significant (p&gt;0,05) correlation between the performance of sportsmen at competitions and average reaction time (r=-0,31). The similar correlation was established in group 1 between results at competitions and accuracy of reactions, r=-0,25 (p&gt;0,05). In group 2, there was also no statistically significant (p&gt;0.05) correlation between the results of the competition and the average reaction time (r=0,52). There is a statistically significant strong inverse correlation (p&lt;0,05) in group 2 between the results of athletes in competitions and their reaction accuracy (r=-0,83). Conclusions. The results of the analysis of the reaction to a moving object indicate that there are significant differences between the groups. Highly skilled, older athletes have better ability to adjust nervous processes and shorter reaction times to a moving object. There is a statistically significant correlation between athletes' performance in competitions and the accuracy of their reactions. Indicators such as reaction speed and accuracy are important in taekwondo competitions and should be studied in future research.

Reaction time-induced improvement in hyperthermia properties of cobalt ferrite nanoparticles with different sizes

Chemical reaction conditions involved in the formation of nanoscale materials can enormously affect their properties. However, the correlation between the reaction time (RT) and hyperthermia properties of magnetic nanoparticles (MNPs) is yet to be understood. Here, we synthesize cobalt ferrite magnetic nanoparticles (MNPs) using a thermal decomposition technique with different RT values. The variation in RT (70–180 min) is designed in such a way that the nucleation and growth process can be affected and improved considerably, achieving monodisperse spherical-like MNPs with superparamagnetic nature as confirmed by first-order reversal curve analysis. Hyperthermia properties are studied for cobalt ferrite MNP ferrofluids with different concentrations (1–5 mg/ml) at various magnetic field strengths (100–400 Oe). We obtain a maximum specific loss power (SLP) value of 510 W/g for MNPs synthesized using RT = 150 min. By extracting magnetic characteristic, we find a correlation between SLP and coercive field values as a function of RT, which can shed light on subtle changes in hyperthermia properties of MNPs.

Validation of a Novel Reaction Time Test Specific for Military Personnel

A military-specific reaction time (RT) test was developed to explore its reliability and sensitivity to discriminate between military personnel and sport science students. Fifteen male professional Spanish soldiers and 16 male sport science students completed two RT test modalities: military-specific and nonspecific RT tests. For each RT test modality, both the Simple (i.e.,one stimulus, one response) and the Go, No-Go RT (i.e.,true, and false stimuli, one response) were tested. The military-specific RT test consisted of a video presented through virtual reality glasses of a forest environment in which soldiers would appear from behind different bushes (stimuli) and the response consisted of pressing the button of a gun-shaped mouse (when they saw a soldier pointing a rifle at them). Both Simple and Go, No-Go RT reached acceptable reliability in both populations (coefficient of variation ≤ 9.64%). Military personnel presented a lower RT than sport science students during the military-specific RT test (p ≤ .001), while no differences were obtained during the nonspecific RT test. RT values were not significantly correlated between the military-specific and nonspecific RT tests (r ≤ .02). These findings collectively suggest that the novel military-specific RT test is an ecologically valid alternative to evaluate the information processing abilities of military personnel.

Immediate effects and duration of a short and single application of transcutaneous auricular vagus nerve stimulation on P300 event related potential.

Transcutaneous auricular vagus nerve stimulation (taVNS) is a neuromodulatory technique that stimulates the auricular branch of the vagus nerve. The modulation of the locus coeruleus-norepinephrine (LC-NE) network is one of the potential working mechanisms of this method. Our aims were 1-to investigate if short and single applications of taVNS can modulate the P300 cognitive event-related potential (ERP) as an indirect marker that reflects NE brain activation under control of the LC, and 2-to evaluate the duration of these changes. 20 healthy volunteers executed an auditory oddball paradigm to obtain P300 and reaction time (RT) values. Then a 7 min active or sham taVNS period was initiated and simultaneously a new P300 paradigm was performed. We successively repeated the paradigm on 4 occasions with different time intervals up to 56 min after the stimulation onset. During active taVNS an immediate and significant effect of increasing the amplitude and reducing the latency of P300, as well as a shortening in the RT was observed. This effect was prolonged in time up to 28 min. The values then returned to pre-stimulation levels. Sham stimulation did not generate changes. Our results, demonstrate differential facilitating effects in a concrete time window after taVNS. Literature about the modulatory effect of taVNS over P300 ERP shows a wide spread of results. There is not a standardized system for taVNS and currently the great heterogeneity of stimulation approaches concerning targets and parameters, make it difficult to obtain conclusions about this relationship. Our study was designed optimizing several stimulation settings, such as a customized earbud stimulator, enlarged stimulating surface, simultaneous stimulation over the cymba and cavum conchae, a Delayed Biphasic Pulse Burst and current controlled stimulation that adjusted the output voltage and guaranteed the administration of a preset electrical dose. Under our stimulation conditions, targeting vagal nerve fibers via taVNS modulates the P300 in healthy participants. The optimal settings of modulatory function of taVNS on P300, and their interdependency is insufficiently studied in the literature, but our data provides several easily optimizable parameters, that will produce more robust results in future.

Optimized Artificial Intelligent Model to Boost the Efficiency of Saline Wastewater Treatment Based on Hunger Games Search Algorithm and ANFIS

Chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies of saline wastewater treatment indicate the efficiency of the electrochemical oxidation process. Therefore, the main target of this paper is to simultaneously increase COD and TOC removal efficiencies using artificial intelligence and modern optimization. Firstly, an accurate model based on ANFIS was established to simulate the electrochemical oxidation process in terms of reaction time, pH, salt concentration, and DC applied voltage. Compared with ANOVA, thanks to ANFIS modelling, the RMSE values are decreased by 84% and 86%, respectively, for COD and TOC models. Additionally, the coefficient of determination values increased by 3.26% and 7.87% for COD and TOC models, respectively. Secondly, the optimal reaction time values, pH, salt concentration, and applied voltage were determined using the hunger games search algorithm (HGSA). To prove the effectiveness of the HGSA, a comparison with a slime mold algorithm, sine cosine algorithm, and Harris’s hawks optimization was conducted. The optimal values were found at a pH of 8, a reaction time of 36.6 min, a salt concentration of 29.7 g/L, and a DC applied voltage of 9 V. Under this condition, the maximum COD and TOC removal values were 97.6% and 69.4%, respectively. The overall efficiency increased from 76.75% to 83.5% (increased by 6.75%).

Optimizing the production technology of eco-friendly foam polyurethane panels on the continuous line

With the preeminent features of polyurethane (PU) panels such as sound insulation, heat insulation, fireproof, high load capacity, lightweight, high aesthetics, especially using simple and easy assembly construction and move, so new PU panel is now the first choice for construction projects. In this work, the authors study the new generation physical foaming agent cyclopentane that is environmentally friendly and completely does not destroy the ozone layer. Study investigating and evaluating the effect of content of physical foam cyclopentane on free expansion density, reaction time of rigid polyurethane foam (R-PUF), and reaction time values ​​(cream time, gel time, tack-free time, and rise time). The morphology and size of the closed-cell of the R-PUF samples with cyclopentane concentrations increasing from 0% to 20% are observed by the optical microscope image and the closed-cell size distribution chart is determined by IT3 software. In addition, the physical and mechanical properties of dimensional stability and compressive strength were analyzed to evaluate the quality of the expanded R-PUF insulation in the mold using a cyclopentane physical foaming agent. Experimental procedures according to Taguchi's analysis on the continuous production line are aimed at giving optimal parameters for the industrial PU panel manufacturing process. The research results provide an excellent reference value for manufacturers to further improve the performance and quality of PU panels.

Intravenous Dabigatran Provides Adequate Anticoagulation for Cardiopulmonary Bypass Using a Rabbit Model.

Heparin anticoagulation has been used successfully for cardiopulmonary bypass (CPB). However, an alternative anticoagulant approach is desirable due to the cases of heparin-induced thrombocytopenia. Dabigatran provides anticoagulation for an in vitro model of simulated CPB. The current analysis tests the hypothesis that dabigatran provides sufficient anticoagulation for CPB in intact rabbits. Nonlinear mixed effects models were used to estimate dabigatran parameters for a two-compartment pharmacokinetic model in 10 New Zealand White rabbits. A dabigatran infusion designed to maintain a plasma concentration of 90 µg/ml was run throughout CPB based on the pharmacokinetics. Animals were subjected to sternotomy and anticoagulated with IV dabigatran (six animals) or heparin (four animals). Rabbits were cannulated centrally using the right atrium and ascending aorta and CPB was maintained for 120 min. Measurement of activated clotting time, thromboelastometric reaction time, and blood gases were performed during CPB. Then, the animals were euthanized, and the brain and one kidney were removed for histology. Sections of the arterial filters were inspected using electron microscopy. The observed dabigatran concentrations during CPB were greater than the target concentration, ranging from 137 ± 40 μg/ml at 5 min of CPB to 428 ± 150 μg/ml at 60 min, and 295 ± 35 μg/ml at 120 min. All rabbits completed 2 h of CPB without visible thrombosis. In the two groups, reaction time values were elevated, reaching 10,262 ± 4,198 s (dabigatran group) and 354 ± 141 s (heparin group) at 120 min of CPB. Brains and kidneys showed no evidence of thrombosis or ultrastructural damage. Sections of the arterial line filter showed minimal or no fibrin. There was no significant difference in outcomes between dabigatran- and heparin-treated animals. In this first-use, proof-of-concept study, the authors have shown that dabigatran provides acceptable anticoagulation similar to heparin to prevent thrombosis using a rabbit CPB model.

Adsorption characteristics of dopamine by activated carbon: Experimental and theoretical approach

In this work, we investigate the adsorption mechanism of dopamine (DP) drug using an activated carbon (AC) type through experimental and theoretical data. Experiment series were carried out at different initial values of solution pH, temperature, reaction time and initial drug concentration. The effect of protonation and deprotonation of DP molecule was also investigated. The equilibrium isotherm data were evaluated using the Dubinin-Radushkevich, Langmuir, Temkin and Freundlich models. Elovich, pseudo-first and pseudo-second order kinetic models were used to analyze kinetic data. Here we also used molecular dynamic (MD) simulation and DFT-based computational methods to reach information about the electronic properties of DP drug and its adsorption mechanism that have not been experimentally observed. Experimental results show that the Elovich kinetic model and Langmuir model best describe the adsorption phenomenon. In parallel, the experimental analysis revealed that the adsorption process is spontaneous and endothermic. Dopamine adsorption on AC occurs quickly and is pH and temperature-dependent. Frontier molecular orbital (FMO) energies for neutral, deprotonated and protonated forms of DP were determined and thoroughly explained. The basic medium significantly impacts DP drug adsorption behavior, which has the greatest adsorption energy when the pH is less than 12. It was found that DP adsorption occurs in a bidentate geometry by forming strong bonds between molecular oxygens and carbon atoms on the AC surface. Based on theoretical calculations interaction mechanisms of DP on the AC (001) surface were proposed.

Evaluación cinética de la decoloración fotocatalítica del colorante Synozol Red K3BS utilizando TiO2-anatasa y radiación solar directa

The intense solar radiation of the city of Arequipa has been used as an activation factor for TiO2 anatase to evaluate the decoloration kinetics of the Synozol Red K3BS textile dye. For this purpose, a factorial design (23) was developed to optimize the values of reaction time, pH and TiO2 doses for 200 mL of solution. The optimal factors for the study were: a 60 min duration, a pH of 3 and 0.1 g of photocatalyst. The first-order kinetic model adequately explained the decoloration of a solution at a concentration of 40 mg/L, showing an excellent reaction rate constant &nbsp;and a decoloration percentage of 86.15%.

Modification of bimetal Zn/ Mg MOF with nanoparticles Fe3O4 and Fe3O4@SiO2, investigation of the peroxidase-like activity of these compounds by calorimetry and fluorimetry methods

In this article; the bimetal metal-organic framework Zn/Mg (Zn/Mg MOF) is synthesized.Then Zn/Mg MOF bimetal was combined with Fe3O4 and Fe3O4@SiO2, and composites of Fe3O4@ SiO2/MOF/Dextrin, Fe3O4@SiO2/MOF, Fe3O4@MOF/Dextrin and Fe3O4@MOF made. The peroxidase-like activity of these compounds was investigated and compared by calorimetric Resazurin (Rz) and O-phenylenediamine (OPD); (Rz-H2O2, OPD-H2O2) and fluorimetric Rz and terephtalic acid (TA); (Rz-H2O2, TA-H2O2). The Fe3O4@ MOF/Dextrin composite has the highest peroxidase-like activity. The effect factors (amount of pH (6), the values of TA (1.37 mM), H2O2 (0.025 mM), reaction time (8.15 min), and amount of Composite (116.67 mg)) to increase the catalytic activity of Fe3O4@ MOF/Dextrin measured by chemometrics method. The most suitable linear range of the calibration curve by the TA-H2O2 -Composite fluorimetric method is 1–600 μg L−1, and the detection limit is 2.27 μg L−1. The relative standard deviation (RSD%) for measuring concentration atropine 1 μg L−1 (n = 6) is 1.18%. Finally, from this system for measuring atropine extracted by the Liquid-liquid extraction (LLE) method in two types of plants, D. Innoxia north and west and D. stramonium north and west of Iran (118.25 μg L−1, 79.80 μg L−1) and (18.477 μg L−1, 9.27 μg L−1) used, respectively.

STUDY OF THE RHEOLOGICAL PROPERTIES OF COMPOSITE POLYMER STABILIZERS FOR DRILLING FLUIDS

This article presents the results of experimental data on the preparation of a composite heatresistant reagent for drilling fluids, including a modified copolymer based on polyacrylonitrile (by hydrolysis in the absence of a mixture of sodium hydroxide) and vinylsulfonic acid. A thermally stable composite reagent to polyvalent cations has been obtained, which reduces filtration and improves the anti-wear properties of clay suspensions. The values of the optimal reaction time and temperature were determined, the viscosity of the sampled polymer solutions was determined. The ratio of monomers and modification conditions are selected, this ensures a high conversion of monomers, and also increases the yield of the final product. The synthesized polymer of acrylonitrile and in the presence of fatty acids of gossypol resin and sulfuric acid in the pH = 3.5-5.5, with subsequent modification. The synthesized water-soluble polymer has a diphilic structure throughout the structure, the macromolecules of which contain a hydrophobic group and a hydrophilic part. They are able to adsorb and lower the interfacial free energy, which allows them to be classified as high-molecular surfactants.

From tuna viscera to added-value products: A circular approach for fish-waste recovery by green enzymatic hydrolysis

Tuna represents one of the most consumed foods in many parts of the world. It is estimated that about 70 % of the tuna's weight is discarded in the production of canned fillets. This work is focused on the optimization of production of an oil rich in omega-3 from the tuna viscera, provided by a canned tuna production company, using the Alcalase enzyme. Combined use of Design of experiments (DoE), life cycle analysis (LCA), and principal component analysis (PCA) on the collected analytical data made it possible to define the best combination of the values of pH, enzyme/substrate (E/S) ratio, and reaction time, respectively (pH = 8.5), E/S (1 %), and time (120 min), and to better understand the environmental bottleneck of the process. The outcomes of the study demonstrated that the duration of the hydrolysis and the associated electricity consumption is the factor that affects the most the environmental sustainability of the process.

Training effect on sex-based differences in components of the Shepard and Metzler mental rotation task

BackgroundSpatial ability has been reported to indicate sex-based differences in humans, mainly assessed by Shepard and Metzler mental rotation task (SM-MRT). Most performances in earlier studies have been evaluated by the mean value of reaction time and/or accuracy. The performance indexes might not be sensitive measures of mental rotation. Sex-based differences in the performance might also be involved in the spatial experience of the subject at the time. This study observed variations in components of the SM-MRT over repetition.MethodsMale (n = 17) and female (n = 17) subjects completed 20 days of repeating the SM-MRT. The slope and intercept of the function performance (reaction time) to the angular disparity are calculated; the slope of this function indexes the mental rotation (main-process), and the intercept indexes the other sub-processes.ResultsA significant main effect of sex was obtained on the slope. The intercept also showed a tendency toward statistical difference. The interactions between the sexes and the day were not significant for the indices. Statistical testing for coefficient of variations (CV) indicated no sex-based difference in the effect of the intercept throughout the experiment day. The CV of the slope, however, showed tendencies toward sex-based difference from days 7 to 12.ConclusionsThe difference between the sexes in performance on the slope was sustained throughout the experimental period. A few female subjects who demonstrated larger slope values than male subjects caused the sex difference. The learning rate of mental rotation may be an inherent spatial ability.

Acute effects of aerobic versus resistance exercises on cognitive function in individuals with intellectual disability.

This study compared the acute effects of aerobic (AE) and resistance (RE) exercise on reaction time (RT) and working memory (WM) in individuals with intellectual disability. RT tests and Corsi test for WM were performed before and after three intervention sessions: AE, RE, or control session consisting on watching video. The RT values decreased significantly (p < .001) after both of AE and RE with higher extend after the RE but did not vary following the control session. Corsi scores increased significantly (p < .001) after AE but not after RE or control session. These findings suggest that the effects of acute exercise on cognitive function in individuals with intellectual disability depend on the exercise mode as well as the nature of the cognitive task. The RE seems to be more recommended for RT enhancement whereas only the aerobic one could improve WM in these individuals.

Reaction Time Based Cognitive Functions and Associated Recovery Heart Rate in Medical Student

Introduction: Physical activity is an indicator of physical function that preserve or promotes cerebral blood flow which in turn is associating with better functioning cognitive function. Cognitive functions can be assessed using reaction time. It is the ability to quick motor response to definite stimulus, while the time that elapses between the sensory stimulation and the motor activity.&#x0D; Aims: To assess the cognitive function of medical students using visual &amp; auditory reaction times in different fitness groups and to correlate values of reaction times to recovery heart rate.&#x0D; Methods: In this cross-sectional study, 57 consenting healthy medical students age 17-30 years, underwent 3-Minutes Step Test to assess their physical fitness along with Auditory reaction time and Visual reaction time to assess their cognitive function. Based on Recovery heart rate which was calculated after 3-Minute step test. Students were categorized into four groups that is good, satisfactory, poor and very poor their Auditory reaction time and Visual reaction time T were measured for these groups.&#x0D; Results: Results showed Auditory reaction time and Visual reaction time was statistically significant when all groups of physically fitness were compared (p-0.014). When pairs of groups were compared significant differences of Auditory reaction time was found good fitness level Vs very poor fitness level in Auditory reaction time (p0.008) and significant difference of Visual reaction time was found between good fitness level Vs satisfactory fitness level in Visual reaction time (p-0.028). Comparison of many other pairs of fitness groups found to be non-significant.&#x0D; Conclusion: Good fitness level has higher cognition which can be achieved by doing physical activity to improve the fitness level.

Effects of a rehabilitation program for Parkinson’s patients on reaction and movement time: an electromyographic study

Purpose: The aim of the study was to investigate the effects of a rehabilitation program consisting of specific exercises for Parkinson's Disease (PD) patients on reaction time (RT), movement time (MT), quality of life and disease activity.&#x0D; Materials and Methods: A total of 26 idiopathic PD patients were included in the study. The exercises specific to Parkinson’s were applied to the patients for 16 weeks. The evaluation of the patients were done before and after the treatment. The disease severity was measured with Unified Parkinson’s Disease Rating Scale (UPDRS), quality of life was measured with Short Form-36 (SF-36). RT and MT measurements were done electromyographically.&#x0D; Results: There was no statistically significant difference in UPDRS total and sub-section values and SF-36 quality of life evaluation before and after the exercise program. While a significant decrease was observed in the RT values of the patients after the 16 week exercise program compared to prior to the program (Deltoid RT 370.46 ± 25 to 219.58 ± 17, biceps RT 370.42 ± 27 to 216.49 ± 14 and triceps RT 445.21 ± 31 to 247.53 ± 23, respectively).&#x0D; Conclusion: In PD, the rehabilitation program specific to the disease leads to a significant decrease in RT. Although the exercise has no statistically significant effect on disease activity, quality of life and MT values, it was seen that it still led to improvement.

Effect of Micro Nano-Structured Copper Additives with Different Morphology on Tribological Properties and Conductivity of Lithium Grease

ABSTRACT In order to explore the effect of micro nano-structured copper additives with different morphology on tribological properties and conductivity of lithium base grease, nano-sized copper sheets (denoted as Cu NSs), micro-sized copper wires (denoted as Cu MWs) and copper particles (denoted as Cu Ps) between micrometer and nanometer scale were prepared by liquid-phase chemical methods. The effects of synthetic variables such as reaction temperature, reaction time and pH value of reactant solution on the morphology of the final products were investigated. The as-prepared Cu NSs, Cu MWs, and Cu Ps were characterized by field emission scanning electron microscopy and X-ray diffraction. Their effects on the tribological properties and conductivity of lithium grease were investigated via ball-on-disk sliding tests and contact resistance measurements as well as morphology and element composition analyses of worn block surface. The experimental results show that the morphology of the product is significantly affected by the experimental conditions. This makes it feasible to fabricate copper additives with desired morphology by properly tuning the reaction conditions. Besides, the as-prepared copper additives can improve the tribological properties and conductivity of lithium base grease, because they can be adhered and deposited on rubbed steel surfaces to form boundary lubricating films consisting of cuprous oxide, cupric oxide, ferric oxide and other oxides.

Thermal behavior and antibacterial studies of a carbonate Mg–Al-based layered double hydroxide (LDH) for in vivo uses

The goal of this work is to study the thermal behavior and the antibacterial properties of a MgAl-CO3 layered double hydroxide (LDH), which demonstrated high efficiency in removing chromium (VI) from contaminated industrial wastewater. The compound has been synthesized via co-precipitation route (direct method) followed by hydrothermal treatment, obtaining nanoscopic crystallites with a partially disordered (turbostratic) structure. After its synthesis, the compound was characterized by means of X-ray powder diffraction, field emission scanning electron microscope, inductively coupled plasma atomic emission spectroscopy and analysis and Fourier transform infrared spectroscopy. On the other hand, with the view to check the drug delivery and surgical tools usage of MgAl-CO3, antibacterial tests, performed according to the Kirby–Bauer method, revealed the inability the growth of the pathogenic bacterial strains. Thermogravimetry and differential thermal analysis revealed that evolution of water from the material occurs in two stages upon heating and a noticeable interaction takes place between water (in the vapor phase) and MgAl-CO3. Kinetic analysis of both steps provides almost constant values of activation energy, with the following average values in the range 0.1 < a < 0.9: E1 = (66 ± 9) kJ mol‒1; E2 = (106 ± 7) kJ mol‒1. Finally, prediction of reasonable reaction times extrapolated at 25 and 37 °C has been made from kinetic parameters of the first step, while almost unrealistic reaction time values were determined using the same procedure with kinetic parameters related to the second step.