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The study was carried out to evaluate the pharmacokinetic disposition of enrofloxacin (ENF) with a single dose of 20 mg/kg after oral administration in largemouth bass (Micropterus salmoides) at 28°C. The concentrations of ENF and of its metabolite ciprofloxacin (CIP) in plasma, liver, and muscle plus skin in natural proportions were determined using HPLC. The concentration-time data for ENF in plasma were best described by a two-compartment open model. After oral administration, the maximum ENF concentration (Cmax ) of 10.99 μg/ml was obtained at 0.60 hr. The absorption half-life (T1/2Ka ) of ENF was calculated to be 0.07 hr whereas the elimination half-life (T1/2β ) of the drug was 90.79 hr. The estimates of area under the plasma concentration-time curve (AUC) and apparent volume of distribution (Vd/F) were 1,185.73 μg hr/ml and 2.21 L/kg, respectively. ENF residues were slowly depleted from the liver and muscle plus skin of largemouth bass with the T1/2β of 124.73 and 115.14 hr, respectively. Very low levels of ciprofloxacin were detected in the plasma and tissues. A withdrawal time of 24 days was necessary to ensure that the residues of ENF + CIP in muscle plus skin were less than the maximal residue limit (MRL) of 100 μg/kg established by the European Union.

The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports. The spatial and temporal distribution characteristics of hotspots are analyzed based on the risk assessment model of hotspot constructed in this paper. Firstly, approaches for monitoring of the aerodrome movement were compared. The hotspot recognition algorithm taken into account of whether aircrafts’ taxi track has spatial and temporal overlap based on the aerodrome surveillance radar (ASR) data was presented, by identifying the hotspots through analyzing whether the aircrafts’ time of entering and exiting the same taxiway is overlap or not, and the heading difference and distance of the two aircrafts satisfy the specified threshold constraint condition. Then, the ASR data were divided into several parts, and then airport hotspots were recognized and the spatial and temporal distribution characteristics were analyzed. The risk assessment model of airport safety hotspots was constructed which is taken into account of the conflict probability and its severity consequence. Finally, based on the risk grade assessment criteria and hotspots’ risk value, the risk grade ranking of hotspot in one airport of China was evaluated and designated. According to the result, the spatial and temporal distribution characteristics of airport hotspots were varied with the variation of airport traffic flow and operational mode of runway, which shows that the hotspots have the characteristics of dynamic periodicity and diurnal variation. And the risk assessment results were consistent with experts’ opinions and actual operation condition, which verified the rationality of the hotspot recognition algorithm, risk assessment model as well as the risk grade ranking criteria.

By embedding a fibre Bragg grating (FBG) sensor which had been recalibrated at cryogenic temperatures in the cement-based materials to be tested, the thermal strain of cement-based materials and the factors affecting it could be effectively measured under cryogenic temperatures for its freeze-thaw cycles. The freezing process of pore water was characterized by a differential scanning calorimeter (DSC), and the ice content was calculated by thermoporometry (TPM). The relationship between the freezing process of pore water and the thermal strain was discussed. The results confirmed that FBG sensors could characterize the on-time thermal strain of cement-based materials under cryogenic temperatures. The moisture content and fine aggregate had a great influence on the thermal strain under cryogenic temperatures and its freeze-thaw cycles. Cement paste expanded from −25 °C to −50 °C in the cooling period and contracted from −50 °C to −5°C in the heating period. The residual strain remained in the matrix generated by water freezing between 0℃ and −50℃ after six cryogenic freeze-thaw cycles. Greater thermal strain was generated in the cement paste with a higher moisture content, and fine aggregate obviously increased the thermal strain of cement-based materials. The migration and freezing of pore water are the main reasons for the thermal strain of cement-based materials at cryogenic temperatures.

In this work, a reliable and affordable QuEChERS sampling method is developed for simultaneous detection and quantification of 13 perfluorinated compounds (PFCs) in aquatic products. Liquid chromatography/tandem mass spectrometry (LC-MS/MS) was used for rapid analysis and the analytes were extracted using styrene-divinylbenzene copolymer (PS-DVB). The performances of the sorbents were evaluated based upon parameters, such as recovery and matrix effect. Under optimized conditions, the limits of detection of 13 PFCs were found to be lying within the range of 0.001–0.070 μg kg−1. The application of aquatic sampling demonstrated that ultra-trace levels of PFCs were successfully detected and quantified within the range of 0.028–31.0 μg kg−1 in tilapia (Oreochromis niloticus), salmon (Oncorhynchus mykiss), mussels (Perna viridis) and clam (Ruditapes philippinarum). Compared with the solid phase extraction method, the application of PS-DVB beads as an adsorbent proved to be quicker and successful in the determination of PFCs in aquatic samples.

Properties of cement-based materials at cryogenic temperatures are quite different from those at room temperatures. The strength of mortars at cryogenic temperatures was experimentally studied and an empirical model was established. The freezing thermodynamic process of pore water and pore size distribution in mortars were characterized by differential scanning calorimeter (DSC) and thermoporometry (TPM), respectively. The relationship between the increased cryogenic strength and pore ice formation was discussed. The results showed that flexural strength of mortars increased at a higher rate than compressive strength. Water content and initial strength at room temperatures were the main factors influencing the cryogenic strength. Higher water content and higher initial strength resulted in higher cryogenic strength. Ice formation in pores is one of the main reasons for the mortar’s cryogenic strength increase. Nearly half of the water remained unfrozen in pores with radius less than 40 nm at −40 °C. Both ice formed in capillary pores and gel pores contributes to the strength increase observed at cryogenic temperatures.

Enrofloxacin (ENR) is effective in the prevention and treatment of bacterial infections caused by various fish pathogenic bacteria such as Aeromonas spp., Vibrio spp., Nocardia and Yersinia spp. The purpose of this work was to explore the pharmacokinetics (PK), tissue distribution, and depletion of ENR and its main metabolite, ciprofloxacin (CIP), in northern snakehead (Channa argus) reared at 25 °C during and after repeated oral dose of 10 mg/kg animal body weight per day for a total of 5 days. ENR and CIP concentrations were simultaneously determined in the plasma, liver, kidney, gill, and muscle with adhering skin by HPLC with fluorescence detection. Using a non-compartmental analysis, PK parameters were derived from the mean concentration versus time data of ENR and CIP. The results showed a slow absorption, long half-life and wide tissue distribution of ENR in the northern snakehead. The maximum concentrations of ENR in the plasma, muscle plus skin, liver, kidney, and gill tissues were observed at 3, 6, 6, 6, and 9 h post treatment, respectively, and the corresponding depletion half-lives (T1/2z) were 78.00, 83.24, 82.56, 126.07, and 68.70 h, respectively. The extent of ENR distribution into the tissues followed the decreasing order of liver > kidney > gill > plasma > muscle plus skin. The highest concentrations of both ENR and CIP were observed in the liver, suggesting that liver is the major site of ENR metabolism in northern snakehead. The Cmax/MIC and AUC24/MIC ratios obtained in the present study indicated that the ENR regimen employed would be effective in treatment of infections caused by susceptible strains with MIC values below 0.7 μg/mL. Based on the calculation results, a reasonable withdrawal period should not be less than 18 days at 25 °C for ENR in northern snakehead after treatment ceased.

The Asian giant softshell turtle, Pelochelys cantorii, is endangered and has been designated as a first-grade protected animal in China. This article reports the results of a study on the reproductive biology of Asian giant softshell turtles. Two individuals, a male and a female from the Suijiang River in Guangning County, Guangdong Province, were introduced into captivity 8 yrs ago. The 2 turtles have engaged in mating activity since April 2014, and the female laid a total of 66 eggs in 2014 (25 eggs on 15 June, 22 eggs on 30 June, and 19 eggs on 14 July). The egg laying took an average of 50.6 min. Egg shape was spherical, and mean (± SD) egg mass was 13.27 ± 0.97 g, with mean diameter 2.90 ± 0.12 cm. The viability rate was 46% and the hatching rate 33%, and only 10 neonates successfully hatched. Hatchling body weight averaged 10.0 ± 0.56 g, carapace length averaged 42.25 ± 3.69 mm, carapace width averaged 40.25 ± 1.58 mm, and carapace height averaged 12.54 ± 0.91 mm. The juvenile turtles diffe...

The pharmacokinetics of cefquinome was studied in plasma after a single dose (10 mg/kg) of intramuscular (i.m.) or intraperitoneal (i.p.) administration to tilapia (Oreochromis niloticus) in freshwater at 30 °C. Ten fish per sampling point were examined after treatment. The data were fitted to two-compartment open models following both routes of administration. The estimates of total body clearance (CL/F), volume of distribution (Vd/F), and absorption half-life (T1/2ka ) were 0.049 and 0.037 L/h/kg, 0.41 and 0.33 L/kg, and 0.028 and 0.035 h following i.m. and i.p. administration, respectively. After i.m. injection, the elimination half-life (T1⁄2β ) was calculated to be 5.81 h, the maximum plasma concentration (Cmax ) to be 49.40 μg/mL, the time to peak plasma cefquinome concentration (Tmax ) to be 0.14 h, and the area under the plasma concentration-time curve (AUC) to be 204.6 μg h/mL. Following i.p. administration, the corresponding estimates were 6.05 h, 44.39 μg/mL, 0.17 h and 267.8 μg h/mL. The minimum inhibitory concentrations of cefquinome, determined for 30 strains of Streptococcus agalactiae isolated from diseased tilapia, ranged from 0.015 to 0.12 μg/mL. Results from these studies support that 10 mg cefquinome/kg body weight daily could be expected to control tilapia bacterial pathogens inhibited in vitro by a minimal inhibitory concentration value of ≤2 μg/mL.

The single-dose disposition kinetics of the antibiotic marbofloxacin were determined in Chinese soft-shelled turtles (n = 10) after oral and intramuscular (i.m.) dose of 10 mg/kg bodyweight. The in vitro and ex vivo activities of marbofloxacin in serum against a pathogenic strain of Aeromonas hydrophila were determined. A concentration-dependent antimicrobial activity of marbofloxacin was confirmed for levels lower than 4 × MIC. For in vivo PK data, values of AUC: minimum inhibitory concentration (MIC) ratio for serum were 1166.6 and 782.4 h, respectively, after i.m. and oral dosing of marbofloxacin against a pathogenic strain of A. hydrophila (MIC = 0.05 μg/mL). The ex vivo growth inhibition data after oral dosing were fitted to the inhibitory sigmoid Emax equation to provide the values of AUC/MIC required to produce bacteriostasis, bactericidal activity and elimination of bacteria. The respective values were 23.79, 36.35 and 126.46 h. It is proposed that these findings might be used with MIC50 or MIC90 data to provide a rational approach to the design of dosage schedules, which optimize efficacy in respect of bacteriological as well as clinical cures.

China is the largest freshwater aquaculture producer and antibiotics consumer in the world, and rivers in China are generally polluted by antibiotics. However, there is little information available regarding the linkage of antibiotics in aquaculture and the aquatic environment. Therefore, this study investigated the fate of antibiotics in several open water culture-based freshwater aquafarms, including integrated livestock/fish systems and non-integrated fish ponds, and explored the contamination profiles of antibiotics in the Beijiang River. Then the study tried to clarify the two-way interaction of antibiotics in aquaculture and the environment. The results showed that, when compared with the effluent from livestock farms and wastewater treatment plants, the contribution of antibiotics from non-integrated fish pond water without livestock sewage input was limited, while that of effluent from the integrated livestock/fish system was quite high. The total concentrations of antibiotics detected in the aquafarm source water were similar to those in the upper river water and generally higher than those in the corresponding fish pond water, implying that the occurrence of antibiotics in intensive aquafarms can mainly be attributed to the antibiotic residues in nearby river water. Overall, the results underscore the need to develop a sewage infrastructure for the treatment of effluent from integrated livestock/fish aquafarms, and suggest that open water culture-based fish farms should be located far from seriously contaminated sections of rivers.

The Asian giant softshell turtle, Pelochelys cantorii (Trionychidae), is endangered and was designated as a First Grade Protected Animal in China in 1989 and listed as Endangered on the International Union for Conservation of Nature Red List in 2000; the species has suffered a gradual reduction in its range, its total population has decreased, and the need to protect this species has been ignored. We investigated 13 nature reserves with P. cantorii as the main object of protection and 5 captive-breeding centers; we also present the results from a questionnaire sent to one nature reserve. We summarize the distribution and habitat characteristics, evaluate the species' conservation status in each nature reserve, analyze the causes of extinction, and put forward our proposal for the protection of P. cantorii.

The pharmacokinetics of enrofloxacin (ENR) was studied in crucian carp (Carassius auratus gibelio) after single administration by intramuscular (IM) injection and oral gavage (PO) at a dose of 10 mg/kg body weight and by 5 mg/L bath for 5 hr at 25°C. The plasma concentrations of ENR and ciprofloxacin (CIP) were determined by HPLC. Pharmacokinetic parameters were calculated based on mean ENR or CIP concentrations using WinNonlin 6.1 software. After IM, PO and bath administration, the maximum plasma concentration (Cmax) of 2.29, 3.24 and 0.36 μg/ml was obtained at 4.08, 0.68 and 0 hr, respectively; the elimination half-life (T1/2β) was 80.95, 62.17 and 61.15 hr, respectively; the area under the concentration–time curve (AUC) values were 223.46, 162.72 and 14.91 μg hr/ml, respectively. CIP, an active metabolite of enrofloxacin, was detected and measured after all methods of drug administration except bath. It is possible and practical to obtain therapeutic blood concentrations of enrofloxacin in the crucian carp using IM, PO and bath immersion administration.

Azole fungicides have been reported to be accumulated in fish tissue. In this study, a sensitive and robust method using high-performance liquid chromatography-tandem mass spectrometry combined with ultrasonic extraction, solid-liquid clean-up, liquid-liquid extraction and solid-phase extraction (SPE) for enrichment and purification have been proposed for determination of azole fungicides in fish muscle samples. According to the results of non-statistical analysis and statistical analysis, ethyl acetate, primary secondary amine (PSA) and mixed-mode cation exchange cartridge (MCX) were confirmed as the best extraction solvent, clean-up sorbent and SPE cartridge, respectively. The satisfied recoveries (81.7-104%) and matrix effects (-6.34-7.16%), both corrected by internal standards, were performed in various species of fish muscle matrices. Method quantification limits of all azoles were in the range of 0.07-2.83ng/g. This optimized method was successfully applied for determination of the target analytes in muscle samples of field fish from Beijiang River and its tributaries. Three azole fungicides including climbazole, clotrimazole and carbendazim were detected at ppb levels in fish muscle tissues. Therefore, this analytical method is practical and suitable for further clarifying the contamination profiles of azole fungicides in wild fish species.

To enhance the operational safety of civil aviation, based on the data of civil aviation unsafe incidents on 2006-2015, the assessment index was constructed with typical accident and incident events, and the operational safety risk assessment model based on grey whitening clustering was proposed in this paper. Then the weight of each index is determined by the principle of maximizing deviation. Finally, the safety risk in these 10 years was evaluated by actual operation data. According to the result, it was consistent with the actual operation of civil aviation, which verified the rationality of the safety risk assessment indexes taking into account of the typical accidents and incidents. It had changed the traditional safety assessment index and methods of civil aviation based on people, machines, environment and administration, which had positive significance to improve the safety production capacity of civil aviation.

The northern snakehead (Channa argus) and blotched snakehead (Channa maculata) and their reciprocal hybrids have played important roles in the Chinese freshwater aquaculture industry, with an annual production in China exceeding 400 thousand tons. While these are popular aquaculture breeds in China, it is not easy to identify northern snakehead, blotched snakehead, and their hybrids. Thus, a method should be developed to identify these varieties. To distinguish between the reciprocal hybrids (C. argus ♀ × C. maculata ♂ and C. maculata ♀ × C. argus ♂), the mitochondrial genome sequences of northern snakehead and blotched snakehead and their reciprocal hybrids were compared. Following the alignment and analysis of mtDNA sequences of northern snakehead, blotched snakehead and their hybrids, two pairs of specific primers were designed based on identified differences ranging from 12S rRNA to 16S rRNA gene. The BY1 primers amplified the same bands in the blotched snakehead and the hybrid (C. maculata ♀ × C. argus ♂), while producing no products in northern snakehead and the hybrid (C. argus ♀ × C. maculata ♂). Amplification with WY1 yielded the opposite results. Then, 30 individuals per fish were randomized to verify the primers, and the results showed that the primers were specific for breeds, as intended. The specific primers can not only simply distinguish between two kinds of hybrids, but also rapidly identify the two parents. This study provides a method of molecular marker identification to identify reciprocal hybrids.

The complete mitochondrial DNA of Channa argus, Channa maculata, C. maculate ♀ × C. argus ♂ and C. argus ♀ × C. maculata ♂ were sequenced to characterize and compare their mitochondrial genomes. The lengths were 16,558, 16,559, 16,558 and 16,559 bp respectively. Start codon of 13 protein-coding genes was ATG, except that COI was GTG. The control region of the mitogenome were 907, 908, 907 and 908 bp in C. argus, C. maculata and their reciprocal hybrids (C. argus ♀ × C. maculata ♂ and C. maculate ♀ × C. argus ♂), respectively.

With the increasing number of flights, the confliction troubles and runway incursions arise, especially in the large airports. To guarantee safety of surface movements, it is necessary to develop Advanced Surface Movement Guidance and Control System (A-SMGCS). This paper focuses on the controller synthesis of A-SMGCS based on discrete event supervisory control theory. During the controller designing process, controlled movements model based on Petri net is proposed, the confliction avoidance problem existing in airport movements is transformed into the state forbidden problem of controlled Petri net. To achieve the forbidden state avoidance and keep the maximum freedom for movement objects, the control problems are sorted into single-object and multi-objects constraint controlling by constraint forms. Complementary place technique and fusion technique are adopted into the two scenarios respectively. The result of simulation indicates that controller designed can detect the potential confliction efficiently and increase the capacity of airport considerably.