Power-time Curves Research Articles

Drop in mechanical work: A highly reliable fatigue-related output in Wingate All-out Test

BACKGROUND: Mathematical procedures involved in the calculation of fatigue index (FI) and power drop (PD) are the main reasons why these traditional fatigue-related indices of Wingate All-out Test (WAT) are the least reliable indices. OBJECTIVE: To suggest a highly reliable fatigue-related output c alculated by drop in mechanical work production (DMW). METHODS: Twenty-one well-trained male athletes (age: 21.8 ± 1.9 years, peak power [PP]: 14.7 ± 1.3 W ⋅ kg - 1) participated in a series of WAT sessions, using 10% of their body mass as the workload, separated by 2-4 days. These WAT sessions were continued until the difference in PP between successive trials was less than 5%. Traditional FI and PD values were calculated using mean power data obtained from 5, 3, 2 and 1-second time intervals and using instantaneous power data, while DMW was calculated by predetermined areas in power-time curve. RESULTS: Intraclass correlation coefficients (ICC) and coefficient of variations (CV) revealed that DMW had higher reliability level (ICC = 0.92, CV = 4.53%) than that of traditional fatigue-related indices (ICC ≤ 0.91, CV ≥ 5.71%). In addition, DMW had the lowest limit of ``real change'' with 10.2% as the minimum detectable change score at 90% confidence. CONCLUSIONS: DMW might be used as a reliable output to evaluate fatigue-related power data of the anaerobic capability. Besides, Monark Inc. may easily modify its Peak Bike 894E software to make 30-second all-out test more reliable for the assessment of fatigability levels.

Effects of Carbon Numbers and Concentration of Alkanol Cosurfactants on the CMC and Thermodynamic Properties of Span80 in N,N-Dimethylformamide Solvent by Microcalorimetry

The power–time curves of the micelle formation process were determined for nonionic surfactants (Span80) in N,N-dimethylformamide solvent with alkanol (n-heptanol, n-octanol, n-nonanol, n-decanol) by titration microcalorimetry. The critical micelle concentration (CMC), aggregation number (n) and thermodynamic functions (ΔrHmθ, ΔrGmθ, ΔrSmθ) were obtained at different alkanol cosurfactants and concentrations. Effects of carbon numbers and concentration of alkanol cosurfactants on the CMC and thermodynamic properties of Span80 in N,N-dimethylformamide solvent were discussed.

Short-term Resistance and Plyometric Training Improves Eccentric Phase Kinetics in Jumping.

The purpose of this investigation was to examine the effect of an abbreviated resistance and plyometric training program on force- and power-time curve variables during jumping. Nineteen male subjects were assigned to either a training (n = 9) or control group (n = 10). Training consisted of performing 3 sets of 3 repetition squats (90% of 1 repetition maximum [RM]) and 5 sets of 6 repetition drop jumps from 40 cm twice per week for 4 weeks. A 1RM in the squat and countermovement (CMJ) and static jump (SJ) performance was assessed before and after training. Several variables were analyzed for individual subject force- and power-time curves for the jumps. Average force- and power-time curves for all subjects combined were also analyzed. Absolute and relative squat strength significantly increased in training group (p ≤ 0.05). Calculation of variables from individual subject force-time curves during the CMJ indicated a significant decrease in eccentric time, minimum force, and eccentric impulse and significant increase in eccentric rate of force development in training group. Analysis of individual power-time curves in the CMJ also revealed a significant decrease in minimum power and eccentric work and a significant increase in eccentric rate of power development. No significant changes occurred in the variables measured for the SJ. The results of this study indicate that short-term strength and plyometric training may preferentially influence eccentric performance variables during jumping in comparison with longer term training enhancements to the concentric phase performance.

Microcalorimetry studies of the antimicrobial actions of Aconitum alkaloids.

The metabolic activity of organisms can be measured by recording the heat output using microcalorimetry. In this paper, the total alkaloids in the traditional Chinese medicine Radix Aconiti Lateralis were extracted and applied to Escherichia coli and Staphylococcus aureus. The effect of alkaloids on bacteria growth was studied by microcalorimetry. The power-time curves were plotted with a thermal activity monitor (TAM) air isothermal microcalorimeter and parameters such as growth rate constant (μ), peak-time (Tm), inhibitory ratio (I), and enhancement ratio (E) were calculated. The relationships between the concentration of Aconitum alkaloids and μ of E. coli or S. aureus were discussed. The results showed that Aconitum alkaloids had little effect on E. coli and had a potentially inhibitory effect on the growth of S. aureus.

Antibacterial evaluation of flavonoid compounds against E. coli by microcalorimetry and chemometrics.

Fighting against multidrug-resistant bacteria requires reliable methods to evaluate the effect of antibacterial agents. As a universal, non-destructive, and highly sensitive tool, microcalorimetry has been used in many biological investigations to provide continuous real-time monitoring of the metabolic activity. This method, based on heat-flow output, was used to evaluate the influence of two flavonoid compounds (liquiritigenin and liquiritin) on Escherichia coli. Some crucial information, such as the thermogenic power-time curve and thermokinetic parameters of E. coli growth affected by the two compounds, was obtained and further studied by chemometric techniques including similarity analysis, multivariate analysis of variance, and principal component analysis. By comparing the values of two main parameters, k 2 (growth rate constant of the second exponential phase) and Q 1 (heat output of the first exponential growth phase) of E. coli based on the box and whisker plot, liquiritigenin and liquiritin could be differentiated according to their antibacterial effects; liquiritin with IC50 (half-inhibitory concentration) of 198.6 μg mL(-1) expressed a stronger antibacterial effect than liquiritigenin with IC50 of 337.8 μg mL(-1). The glucoside group in liquiritin containing four additional free hydroxyls in the diphenylpropane skeleton was crucial for inducing the antibacterial effect. Liquiritin might be a promising candidate against E. coli. This study provides a valuable method for searching for novel antibacterial agents using microcalorimetry with chemometrics.

Microcalorimetry coupled with statistical analysis techniques for bio-activity evaluation of medicinal animal horns and shells

Microcalorimetry is an important analytical tool continuously measuring the heat output generated in the physical, chemical or biological processes. Here, the microcalorimetric method was used to evaluate the bio-activity differences of seven medicinal animal horns and shells on splenic lymphocytes. The cells were placed in the 20-mL glass ampoules containing RPMI-1640 and the test drugs (10 mg mL−1), and the heat output and motility of the cells were examined with an isothermal microcalorimeter. From the measured power–time curves, some quantitative thermokinetic parameters were obtained. By analyzing these parameters using principal component analysis, two main parameters, the maximum heat-output power P m and total heat output Q, were optimized, through which the effects of the seven drugs on splenic lymphocytes were quickly evaluated: 10 mg mL−1 of Cornu Cervi Pantotrichum showed stronger promotion effect than Cornu Cervi on the growth and proliferation of splenic lymphocytes, whereas the other five horns and shells animal drugs including Cornu Saigae Tataricae, Cornu Caprae Hircus, Cornu Bubali, Squama Manis and Carapax Trionycis at 10 mg mL−1 all inhibited the growth of splenic lymphocytes, and Cornu Saigae Tataricae expressed the strongest inhibitory effect. The result of hierarchical clustering analysis on the quantitative parameters indicated that the drugs with promotion effect on splenic lymphocytes clustered into one group and the other drugs with inhibitory effect consisted of another group. The results have highlighted the bio-activity differences of the seven horns and shells animal drugs referring to immune functions from the cell level, providing meaningful references for the clinical use of the valuable drugs.

Degradation of Fructans and Production of Propionic Acid by Bacteroides thetaiotaomicron are Enhanced by the Shortage of Amino Acids.

Bacteroides thetaiotaomicron is commonly found in the human colon and stabilizes its ecosystem by catabolism of various polysaccharides. A model of cross-talk between the metabolism of amino acids and fructans in B. thetaiotaomicron was proposed. The growth of B. thetaiotaomicron DSM 2079 in two defined media containing mineral salts and vitamins, and supplemented with either 20 or 2 amino acids, was studied in an isothermal microcalorimeter. The polyfructans inulin (from chicory) and levan (synthesized using levansucrase from Pseudomonas syringae), two fructooligosaccharide preparations with different composition, sucrose and fructose were tested as substrates. The calorimetric power-time curves were substrate specific and typically multiauxic. A surplus of amino acids reduced the consumption of longer oligosaccharides (degree of polymerization > 3). Bacterial growth was not detected either in the carbohydrate free medium containing amino acids or in the medium with inulin as a sole carbohydrate. In amino acid-restricted medium, fermentation leading to acetic acid formation was dominant at the beginning of growth (up to 24 h), followed by increased lactic acid production, and mainly propionic and succinic acids were produced at the end of fermentation. In the medium supplemented with 20 amino acids, the highest production of d-lactate (82 ± 33 mmol/gDW) occurred in parallel with extensive consumption (up to 17 mmol/gDW) of amino acids, especially Ser, Thr, and Asp. The production of Ala and Glu was observed at growth on all substrates, and the production was enhanced under amino acid deficiency. The study revealed the influence of amino acids on fructan metabolism in B. thetaiotaomicron and showed that defined growth media are invaluable in elucidating quantitative metabolic profiles of the bacteria. Levan was shown to act as an easily degradable substrate for B. thetaiotaomicron. The effect of levan on balancing or modifying colon microbiota will be studied in further experiments.

Microcalorimetry coupled with principal component analysis for investigating the anti-Staphylococcus aureus effects of different extracted fractions from Dracontomelon dao

With the prevalence resistance of Staphylococcus aureus to antibacterial agents, developing novel antibacterial agents is urgent. Recently, plant extracts have got more focus. In this study, the power-time curves produced by S. aureus under the action of the four extracted fractions (PE, CHCl3, EtOAc, and n-BuOH fractions) from the leaves of Dracontomelon dao were determined by microcalorimetry, and then some quantitative parameters, such as growth rate constant k, total heat output Qt, maximum heat-output power Pm, and the appearance time tm were obtained. By analyzing the parameters using principal component analysis, the anti-S. aureus effects of the four fractions were systematically evaluated and compared. Meanwhile, the total flavonoid contents in these fractions were analyzed. The results have evidenced that different fractions using various extraction solvents expressed various anti-S. aureus effects, and the inhibitory effects were presented in a flavonoid content-dependent manner. The EtOAc fraction with the highest total flavonoid content (41.86 %) expressed the strongest anti-S. aureus effect with half-inhibitory concentration (IC50) of 83.93 μg mL−1, which might be applied as a novel antibacterial agent in practice for some infectious diseases. In addition, the microcalorimetric method should be strongly suggested in screening for novel antibacterial agents for fighting against pathogenic bacteria.

Study on hot property differences of Aconiti Lateralis Radix Praeparata and its compatibility with different ginger processed products based on bio-thermodynamics

Aconiti Lateralis Radix Praeparata (ALRP) is commonly used traditional Chinese medicine in clinic, and it is usually in compatibility with ginger including Zingiberis Rhizoma (ZR), Zingiberis Rhizoma Recens (ZRR), and Zingiberis Rhizoma Praeparatum (ZRP) for treatment of diseases. In this paper, microcalorimetry and Cold/Hot plate differentiating technology (CHPD) were employed to explore the hot property differences of ALRP, together with its compatibility with different ginger processed products. By means of principal component analysis (PCA), the heat power of the second peak (P2) and the total heat output (Q) which were the main parameters affecting the E. coli metabolism from the power-time curves were obtained. The results showed that the hot property of ALRP in compatibility with different processed ginger was in order of ZR + ALRP > ZRR + ALRP > ZRP + ALRP > ALRP. Meanwhile, the oxygen consumption and remaining rate (RR) in mice on warm plate suggested that the hot property of ALRP was totally different. The relationships between the main parameters (P2 and Q) values and the observation indexes from CHPD were investigated with canonical correlation analysis. The correlation coefficient showed that parameter Q had a marked correlation with the observation indexes (R > 0.85). Altogether, based on bio-thermodynamics, the hot property differences of ALRP and its compatibility with different ginger processed products followed the order of ZR + ALRP > ZRR + ALRP > ZRP + ALRP > ALRP. This could provide guidance for clinical use of ALRP combining with different ginger processed products.

Study of Antimicrobial Effects of Different Types of Glycyrrhiza Extracts by Microcalorimetry

Recently studies indicate that the microcalorimetry is a suitable measurement for metabolic activities of organisms by recording the rate of heat outputs. In this work, we investigated the growth thermogenic curves of Escherichia coli (E. coli) affected by three kinds of Glycyrrhiza extracts by microcalorimetry. The powertime and exponential phase power-time curves of the E. coli growth at various concentrations of extracts were generated. The kinetic parameters such as the growth rate constants (C), maximum power outputs (Pm), peak times (Tm), and inhibition ratios were calculated and the relationships between Pm or Tm and C were established. Also, the clear correlations among the antimicrobial effects, Pm and C were obtained. The results revealed the Glycyrrhiza extracts had inhibitory activities towards E. coli while the Glycyrrhiza polysaccharides showed the most potent effects.

Past attempts to identify a single physiological parameter as the main indicator of success in the tour de France seem to have failed

Background: Past attempts to identify a single physiological parameter as the main indicator of success in the tour de France seem to have failed. Purpose: To evaluate the validity of the critical power model for the analysis of exhaustive power-time curves of grand tour winners. Methods: The climbing time and the corresponding average climbing power for final and non-final climbs in the tour de France, The Giro and the Vuelta are obtained.  From the final climbs exhaustive (P-t) relations are constructed and analyzed with the Monod-Scherrer critical power model. For each rider we obtained his critical power CP and his anaerobic work capacity AEC. Results and Discussion: We found vast individual variations in CP and AEC. Neither of these single parameters, nor the pairs could identify the necessary quality for success. Winning CP was between minimum 4.82 W/kg (Hesjedal in 2011) and maximum 5.81 W/kg (Indurain in 1994-95). Winning AEC was between minimum 0.75 kJ/kg (Indurain in 1994-95)  and 1.81 kJ/kg (Contador in 2009).  Figure 1 shows the variation in CP and AEC, where the values obtained by Froome in 2012-13 were taken as reference values. Although in 2013 Froome and Contador had almost identical aerobic power, Contador fell short in AEC. This was quite different in his winning Tour 2009, when Contador had superior values both for CP and AEC. The highest historical CP-value is probably for Indurain in 1994, although he combined this with the lowest AEC-value. Hesjedal achieved sub-Froome parameters although he had an almost identical ratio of aerobic to anaerobic components. We see also that Horner’s performance in his Vuelta 2013 is almost identical to Indurain in 1994. Also remarkable is the fact (not shown in fig 1) that the average climbing power of Froome in 14 non-exhaustive climbs of (5.05 ± 0.34) is barely lower than his CP of (5.16 ± 0.02) W/kg. This clearly indicates that modern strategy of the dominant teams is the one of “least controlling power” i.e. riding at a pace just below the leaders CP in order to bring him fresh to the foot of the final climb, but at a pace high enough to exhaust the other contenders. Conclusion: Within the climbing time interval 15 – 60 minutes the Monod-Scherrer critical power model adequately describes the exhausting climbing performances of grand tour champions.In modern cycling the anaerobic component is more important than generally accepted and the practice of estimating the functional threshold power and critical power with a single maximal test over 20 minutes could be invalid. The maximal oxygen uptake for all considered winners is below 90  ml/(min.kg) , with the exception of Indurain in the uncontrolled EPO-years 1994-1995. More investigation of the 2-parameter CP model of the grand tours is necessary and might lead to a performance passport as a supplement to the existing biological passport. Future studies could be facilitated and could gain in public acceptance and credibility with the creation of a public database containing the power data files (SRM, Powertap and others) of all top riders.

Effect of Lithium on Growth Process of Environmental Microorganism by Microcalorimetry and SEM

Bacillus thuringiensis (BT) was the typical environmental microorganism.To explore the environmental behavior of lithium, the growth metabolism of BT under Li+ was investigated by microcalorimetry. The power-time curve showed the growth metabolic power-time curve of BT was divided into the bacterial growth phase and sporulation process. Lithium at 0.1-12mmol L-1 revealed no obvious effect to the bacterial growth phase of BT . Li+ at 0.1-4mmol L-1 stimulated the sporulation production and Li+ at 12-16mmol L-1 inhibited that respectively. While the time for initiation to produce sporulation was not influenced. However, the time for initiation to produce sporulation was earlier than the control induced by 8 mmol L-1 of Li+. The interest turning point of microcalorimetric result was confirmed by the following SEM detection. Besides the proof on environmental behavior of lithium, present results may bring related information for BT spores biological engineering transformation.

Closed Loop Power Control Using Third Order Quadratic Approximator

In this paper we introduce a novel bit error rate (BER) feedback transmit power control (TPC) system using a first-time third order quadratic approximation of the power–time curve. This approximation improves the power efficiency of a dual-rate TPC algorithm in terms of reduced total transmit power by smoothing transmit power transients during adaptive iterations. We show that the third order approximator outperforms linear and second order approximators in terms of transmit power savings, sensitivities, error magnitude, and better tracking performance in following reference desired power curves. For the approximator, we determine operational bounds for stability, and demonstrate algorithm behavior using critical valued inputs. In addition we demonstrate value in using a dynamic, rather than static, performance benchmark for quality of service approximation (obtained used scaled maximum acceptable BER), and provide heuristic estimates for the input parameters for the dynamic benchmark.

Microcalorimetric investigation on antibacterial activity of the peptide from Plutella xylostella

The antibacterial activities of a kind of novel peptide from Plutella xylostella (pxCECA1) on methicillin-resistant staphylococcus aureus (MRSA) and Escherichia coli (E. coli) growth were investigated by microcalorimetry. The heat flow power–time curves of MRSA and E. coli growth in the presence of pxCECA1 were recorded using the 3114/3115 Thermal Activity Monitor Air Isothermal Calorimeter based on ampoule mode at 37 °C. Some parameters including growth rate constant k, maximum power output P max, total heat output Qt, generation time t g, growth inhibitory ratio I, and half-inhibitory concentration of the drugs IC50 were obtained to elucidate the antibacterial activity of pxCECA1. The results showed that k, P max, and Q t decreased, but I and t g increased or delayed with the increase in pxCECA1 concentration. The IC50 of pxCECA1 on E. coli was 6.122 μg mL−1 and MRSA was 7.809 μg mL−1. It could be concluded that pxCECA1 had stronger inhibitory effect on E. coli than MRSA. In vivo test was simultaneously performed using an E. coli and MRSA infection model to validate the antibacterial activity of pxCECA1. The results revealed that pxCECA1 with broad spectrum antimicrobial activities hopefully represented a class of promising substitute of antimicrobial agents.

Is it possible to determine physiological quality and best conditions of storage of soybean seeds by isothermal calorimetry?

• Isothermal calorimetry can detect the reason for soybean seeds low germination power. • Specific enthalpy change during soybean seeds imbibition show three phases with respect to seeds water content. • For a vigorous root protrusion, the enthalpy change value due to water–seed interaction for the three phases should be similar. Seeds of soybean, cv. DM5.8RR of two different physiological qualities were germinated and monitored by isothermal calorimetry and imbibition methods. Also, seeds stored at 25 °C under different vapor pressures were analyzed. Results showed that those seeds with lower physiological quality, lot 1 (germination power of 62%) had a much higher speed of water uptake than seeds with a germination power of 93%, lot 3. Thus, endothermic peaks could be observed in the specific thermal power time curves of germination of seeds of lot 1 which were related to anoxia. Seeds of lot 3 with different initial water content, iWC, showed three phases of imbibition where the third also involved metabolism. Apparently, when the enthalpy change value of water–seed interaction of the three phases is similar, roots protrude with vigor. Such was the case for soybean seeds with 0.084 and 0.101 g g −1 iWC.

Comparison of anti-bacterial activity of three types of di-O-caffeoylquinic acids in Lonicera japonica flowers based on microcalorimetry

The anti-bacterial activities of three types of di-O-caffeoylquinic acids (diCQAs) in Lonicera japonica flowers, a traditional Chinese medicine (TCM), on Bacillus shigae growth were investigated and compared by microcalorimetry. The three types of diCQAs were 3, 4-di-O-caffeoylquinic acid (3, 4-diCQA), 3, 5-di-O-caffeoylquinic acid (3, 5-diCQA), and 4, 5-di-O-caffeoylquinic acid (4, 5-diCQA). Some qualitative and quantitative information of the effects of the three diCQAs on metabolic power-time curves, growth rate constant k, maximum heat-output power Pm, and the generation time tG, total heat output Qt, and growth inhibitory ratio I of B. shigae were calculated. In accordance with a thermo-kinetic model, the corresponding quantitative relationships of k, Pm, Qt, I and c were established. Also, the half-inhibitory concentrations of the drugs (IC50) were obtained by quantitative analysis. Based on the quantity-activity relationships and the IC50 values, the sequence of inhibitory activity was 3, 5-diCQA > 4, 5-diCQA > 3, 4-diCQA. The results illustrate the possibility that the caffeoyl ester group at C-5 is the principal group that has a higher affinity for the bacterial cell, and that the intramolecular distance of the two caffeoyl ester groups also has an important influence on the anti-bacterial activities of the diCQAs.

Determination of Optimal Reaction Conditions and Influence of Metal Ions on Cellulose Degradation by Cellulase in the Dioctyl Sulfosuccinate Sodium Salt (AOT)/n-Hexanol/Cyclohexane Reversed Micelle System

The power-time curves of the cellulose degradation by cellulase were determined under the different conditions with the existence of metal ions or not in the dioctyl sulfosuccinate sodium salt (AOT)/n-hexanol/cyclohexane reverse micelle system by the microcalorimeter method. From these curves, the Michaelis constant and the maximum reaction rate of this reaction were obtained. The optimum T, pH and Wo were determined as Wo = 3.011, pH = 5.015, and T = 315.43 K. Under these optimum reaction conditions, the power-time curves of the cellulose degradation by the cellulase with the metal ions were also obtained. The apparent Michaelis constant and the maximum reaction velocity were gained. The relationship between the apparent Michaelis constant and the concentration of the metal ions was established, and the influence of metal ions was discussed as well. The results indicate that some metal ions have promotion roles on the reaction. However, others could inhibit the reaction. These results are significant for the theoretical and application in the field of reverse micelles enzyme catalysis system.

Microcalorimetry coupled with chemometric techniques for toxicity evaluation of Radix Aconiti Lateralis Preparata (Fuzi) and its processed products on Escherichia coli

As a widely used traditional Chinese medicine (TCM), Radix Aconiti Lateralis Preparata (Fuzi) is not only efficacious but also poisonous. Its toxicity and processed products should be taken into account and effectively evaluated. In this study, a non-invasive and non-destructive microcalorimetric method was employed to evaluate and compare the toxicity of Fuzi and its three processed products including Yanfupian, Heifupian, and Danfupian on Escherichia coli (E. coli). Some important metabolic information, such as the power-time curves and some quantitative thermokinetic parameters including growth rate constant k, heat output power P, inhibitory ratio I, and half inhibitory concentration IC50, of E. coli growth affected by various concentrations of Fuzi and its processed products were obtained. Combined with chemometric techniques including multivariate analysis of variance and principal component analysis on this information, it could be seen that Fuzi and its processed products could be distinguished according to their toxic effects on E. coli. The IC50 values of 14.6 mg/mL for Fuzi, 59.2 mg/mL for Yanfupian, 118.3 mg/mL for Heifupian, and 182.7 mg/mL for Danfupian illustrated that the sequence of toxicity on E. coli was Fuzi > Yanfupian > Heifupian > Danfupian. This study provided a useful method and idea of the combination of microcalorimetry and chemometrics for studying the toxic effects of TCMs and other substances.

Physiological tests for early detection of rigid ryegrass (Lolium rigidum Goud.) resistance to fenoxaprop-P

The study aimed to determine the usefulness of isothermal calorimetry and FT-Raman spectroscopy for the early evaluation of rigid ryegrass resistance to fenoxaprop-P ethyl (active ingredient one of aryloxyphenoxypropionate herbicides). The calorimetric measurements were done on the 4-day-old seedlings of susceptible and resistant biotypes of rigid ryegrass (Lolium rigidum Goud.) for 72 h, at 20 °C. It was observed that the specific thermal power–timecurves of the susceptible and resistant biotypes growing on water (control) were qualitatively similar. Herbicides changed the shape of the specific thermal power–time curves of both biotypes. Furthermore, the total specific thermal energy was significantly higher for the seedlings of resistant biotype, growing both on water or herbicide, as compared to the susceptible ones. The analysis of the seedlings’ endosperm, conducted using FT-Raman spectroscopy, showed a weaker intensity of the bands in the spectra derived from the resistant biotype. Differences in the specific thermal power–time curves and FT-Raman spectra between susceptible and resistant biotypes growing on water indicate that the sensitive and resistant biotypes are metabolically and chemically different already in the early stages of the seedling growth. We conclude that isothermal calorimetry and FT-Raman spectroscopy are efficient tools for the early detection of rigid ryegrass resistance to fenoxaprop-P ethyl.

Toxicity of perfluorooctanoic acid to Pseudomonas putida in the aquatic environment

Perfluorinated compounds are potential persistent organic pollutants which attracted much concerns in recent years. Thus relevant toxicity data of perfluorooctanoic acid (PFOA) are vitally important for identification of possible risk in the aquatic environment. In the present study, the acute toxic effect of PFOA in the absence and presence of either chromium (III) or tetra butyl ammonium (TBA) towards Pseudomonas putida in the aquatic environment was investigated by microcalorimetry. The thermokinetic parameters including growth rate constant (k), inhibitory ratio, and half inhibitory concentration, were calculated and compared using the data obtained from the power–time curves. Our work revealed the toxicity of PFOA under three experimental conditions in a descending sequence: PFOA, PFOA+Cr3+, and PFOA+TBA. The results highlighted that the presence of un-ionized NH3 in the test solutions could not be a potential significant contributor to the observed toxicity of PFOA. In addition, PFOA interacted antagonistically with Cr3+ and TBA. TBA was found to substantially enhance the surface pressure of PFOA which could be related with the toxicity of PFOA. The higher surface pressure caused for the reduction in toxicity. Thus the results highlighted the potential toxicological risk associated with this surfactant in the aquatic ecosystems.