Correction: Naked and necked gold nanoparticles prepared by submerged alternating current arc discharge in water.

[This corrects the article DOI: 10.1039/D2RA06050G.].

Necked gold nanoparticles prepared by submerged alternating current arc discharge in water.

The article presents the method of producing gold nanoparticles using a high voltage arc discharge of alternating current with a frequency of 50 Hz in distilled water. The equipment necessary to carry out the process is described, including the construction of the reactor and the power source of a very simple design necessary to generate a high-voltage arc discharge between the electrodes. Arc discharge processes were carried out two times for 2 and 5 minutes, respectively, in ambient conditions without thermostating the reactor, at medium temperature varying in the range of 25-70 °C. The obtained gold nanoparticles were examined by means of various analytical techniques such as UV-vis spectroscopy, zeta potential measurement, energy dispersive X-ray analysis (EDS), X-ray diffraction (XRD). The morphology, surface, and size of the obtained nanoparticles were carried out using transmission electron microscopy (HRTEM) and dynamic light scattering (DLS). The concentration of the obtained colloids were determined using the mass spectrometry ICP-MS technique. The results show that high-voltage AC arc discharge is a simple and effective way to obtain stable gold nanoparticles under environmentally friendly conditions at relatively low production costs, and can be considered as an alternative to arc discharge nanoparticles synthesis by means of direct current (DC) methods.

Effect of hydromassage on changes in blood electrolyte and lactic acid levels and haematocrit value after maximal effort.

In the control group the haematocrit value dropped from a very high level immediately after effort to much below the resting value in the 1st hour, and returned in the 4th hour to the resting value. In subjects submitted to hydromassage between the 15th minute and 45th minute of rest this value decreased slightly below the resting value only in the 2nd hour of rest. Immediately after the exercise a very high plasma potassium concentration was found in both groups, in the 15th minute of rest it decreased below the resting level, and then it increased in the control group reaching a high second peak in the 2nd hour of rest. On the other hand, in subjects having hydromassage no second significant rise of potassium level was observed. In the 2nd hour of rest the potassium level increased only to the initial level and in the 4th hour it remained at that level. The high concentration of plasma lactic acid immediately after the exercise decreased gradually in the subsequent periods of rest reaching the resting level in the control group only in the 4th hour, and in the hydromassage group in the 2nd hour. No significant changes were found in the remaining determined parameters between the studied groups.

The dynamics of changes in blood electrolyte and lactic acid concentrations, haematocrit, arterial blood pressure and heart rate in canoeists during 4 hours of rest after maximal effort.

In 12 canoeists determinations were carried out of the haematocrit value, and plasma concentrations of sodium, potassium and lactic acid during 4 hours of rest following maximal effort. The age of the sportsmen was from 18 to 21 years. The haematocrit was significantly increased immediately after the effort but in the first hour of restitution it fell below the resting value and increased then reaching the initial value only in the 4th hour. Serum lactic acid concentration increased in the first minutes of rest and then it decreased gradually reaching the resting value in the 4th hour. The concentration of sodium was not significantly changed throughout the whole period of restitution, when the haematocrit changes were taken into account. The concentration of potassium was very high immediately after the effort, but it fell below the resting value in the 15th minute, rose to the resting value in the 1st hour and in the 2nd hour it continued to rise much above the resting value, and only in the 4th it decreased again to the initial value. The author supposes that the second rise of the serum potassium level beginning in the 1st hour of restitution after maximal effort could be due to insufficient supply of ATP for maintaining the needs of the ionic pump or to secondary loss of water from the cells with a consequent rise in the intracellular hydrogen ion concentration.

Changes of glucose utilization by erythrocytes, lactic acid concentration in the serum and blood cells, and haematocrit value during one hour rest after maximal effort in individuals differing in physical efficiency.

Glucose utilization by the erythrocytes, lactic acid concentration in the blood and erythrocytes, and haematocrit value were determined before exercise and during one hour rest following maximal exercise in 97 individuals of either sex differing in physical efficiency. In the investigations reported by the author individuals with strikingly high physical fitness performed maximal work one-third greater than that performed by individuals with medium fitness. The serum concentration of lactic acid was in all individuals above the resting value still after 60 minutes of rest. On the other hand, this concentration returned to the normal level in the erythrocytes but only in individuals with strikingly high efficiency. Glucose utilization by the erythrocytes during the restitution period was highest immediately after the exercise in all studied individuals and showed a tendency for more rapid return to resting values again in individuals with highest efficiency. The investigation of very efficient individuals repeated twice demonstrated greater utilization of glucose by the erythrocytes at the time of greater maximal exercise. This was associated with greater lactic acid concentration in the serum and erythrocytes throughout the whole one-hour rest period. The observed facts suggest an active participation of erythrocytes in the process of adaptation of the organism to exercise.

Physical exercise effect on erythrocyte metabolism.

A group of 27 canoeists from the national team and 35 subjects beginning training in a sports discipline were subjected to investigations for determination of glucose utilization by erythrocytes, and the level of lactic acid in these cells and in serum. Furthermore, erythrocyte count and haematocrit value were determined in them. Both groups performed submaximal and maximal work on cycle ergometer. In the trained sportsmen the erythrocyte count and haematocrit value were higher already before exercise. During the exercise the increase in these values, as well as the rise in erythrocyte and serum lactic acid levels were again greater than in untrained freshmen. This difference was caused by the fact that the trained sportsmen performed twice as much work. Glucose utilization by erythrocytes (in vitro) was greatest after maximal exercise in both groups. The differences observed between both groups became manifest during exercise with a greater rise in glucose utilization by the erythrocytes obtained from the trained group. Fifteen minutes after the exercise this utilization fell in both groups below the value obtained before exercise. During the same time erythrocyte count and haematocrit returned to their initial levels.

An influence of exercise of increasing intensity on aminotransferase activity and electrolyte level in red blood cells and blood serum in men with average and very high physical working capacity.

Healthy subjects with average and very high physical working capacity were submitted to two 6-min periods of work on a cycloergometer at the work loads 70 and 90 percent VO2max. Changes in the activity of Asp AT and Al AT as well as in the concentrations of NA, K and lactates in erythrocytes and serum were determined. In the subjects with average physical working capacity the serum concentrations of lactate and sodium, as well as the activity of Asp AT were much more increased than in the highly efficient subjects. In both groups similar changes of electrolyte concentrations in erythrocytes occured. The activity of Al AT was increased only in the group of subjects with high physical working capacity after the first period of work and showed a tendency to return to the resting values after the second period.