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【Objective】 Garlic is a cash crop in Dali, but its irrigation with livestock wastewater risks environmental pollution. This paper studies the combined effect of livestock wastewater irrigation and nitrogen fertilization on growth, yield, water and nitrogen utilization efficiency of garlic, as well as soil nitrogen in attempts to screen a sustainable livestock wastewater irrigation schedule for garlic production in this region. 【Method】 The experiment was conducted at the National Agricultural Environmental Dali Observation and Experimental Station. There were five treatments: freshwater irrigation without nitrogen application (CK), freshwater irrigation with 390 kg/hm2 of nitrogen application (C1), freshwater irrigation with 312 kg/hm2 of nitrogen application (C2), livestock wastewater irrigation without nitrogen application (R1), livestock wastewater irrigation with 150 kg/hm2 of nitrogen application (R2). In each treatment, we measured the growth indexes, including dry weight, height, stem diameter and leaf area index of the garlic at different growing stages, as well as yield, and water and nitrogen use efficiency of the garlic and soil nitrogen content. 【Result】 The growth of the garlic was the best in R2, but was comparable with that in R1 and C1; R2 gave the highest yield. Compared to CK, C1, C2, R1 and R2 increased the bulb yield by 111.30%, 81.23%, 98.19%, and 142.01%, respectively. The nitrogen absorption and use efficiency of R1 and R2 was 154.71% and 92.25% higher than that of C1, respectively; the nitrogen partial factor productivity of R1 and R2 was 110.75% and 47.63% higher than that of C1, respectively. Compared to C1, R1 reduced the irrigation water productivity and soil nitrogen in the 0-40 cm of soil layer by 29.19%, while R2 increased the irrigation water productivity by 2.34% and reduced soil nitrogen in the 0-40 cm of soil by 3.89%, respectively. Compared to C1, R1 and R2 increased nitrogen in the 0-20 cm of soil layer by 170.90% and 255.93% respectively. 【Conclusion】 Livestock wastewater irrigation combined with appropriate base nitrogen fertilization can sustain garlic growth and yield. Livestock wastewater irrigation improved the nitrogen use efficiency and nitrogen partial factor productivity, with limited effect on average soil total nitrogen.

To reduce the coding computational complexity of the rate and distortion calculations in HEVC, a fast TU level rate model with higher accuracy was proposed.The contribution percentages of different syntax elements in entropy coding were evaluated, and syntax element-wise accurate rate models were individually developed to construct the whole TU level model.In addition, coefficient levels were weighted adaptively to distinguish the nonuniform contributions of different coefficients in terms of rate profiling.Moreover, position-wise parameter was defined to depict the distribution patterns for possible non-zero coefficients within one block.The final linear rate model was developed by fine-tuning the model parameters from great amounts of samples in a statistical way.Finally, the transform domain distortion model was also established to bypass unnecessary reconstruction process.Experimental results show that the proposed algorithm can achieve 49.76% complexity reduction with 1.74% BD-BR increase for RA configuration.

In order to improve the anti-wear performance of edible soybean oil (SO) as lubricant, a modified soybean oil (MSO) was synthesized in a mild reaction environment by using enzyme Novozym435 as catalyst to carry out the epoxidation of unsaturated fatty acids in SO with methanol. The structure was characterized by infrared and Raman spectrometers, the thermal oxidation stability was investigated by synchronous thermal analyzer TG-DSC, and the friction and wear performance of MSO was investigated on a four-ball machine. The scanning electron microscope, three-dimensional surface profilometer, and Raman spectroscopy were used to analyze the micro-morphology and composition changes of the frictional spot surface. The results show that the acid value and iodine value of modified soybean oil decrease significantly, the saturated fatty acid content increases, and the thermal oxidation stability is enhanced. The anti-wear performance of MSO is significantly improved, the spot diameter decreases by 25.56%, and the wear volume decreases by 54.18%.The excellent wear resistance of MSO is mainly related to the content of saturated fatty acid, the excellent thermal oxidation stability and the ordered lubrication film formed on the wear surface.Due to the improvement of its thermal oxidation performance,the action time of the formed orderly lubrication film in the lubrication process is greatly increased,so as to more effectively resist the wear in the friction process. [ABSTRACT FROM AUTHOR]

[Purpose/significance] The current research on knowledge exchange in technical Q&A communities is not perfect. This article uses data envelopment analysis method to study the efficiency of knowledge exchange in technical Q&A communities, and finds the differences and changing laws between different sectors to provide references for improving community management and improving the efficiency of knowledge exchange. [Method/process] Based on the construction of the knowledge exchange efficiency evaluation index system, 15 popular sections of the “OSCHINA” community were used as the research samples, and the static and dynamic efficiency values of the knowledge exchange are calculated and analyzed deeply based on the SBM model and the Malmquist index.[Result/conclusion] The average knowledge exchange efficiency among the 15 popular sections of the “OSCHINA” community is good, but the gap between the sections is large, and the overall knowledge exchange efficiency is on the rise trend, mainly because the technological progress change index increases 19.50%. The increasing rate indicates that technological revitalization is the main reason for the increase in the efficiency of knowledge exchange in the “OSCHINA” community, but a certain degree of mismanagement has occurred and the utilization of resources is low.

The aim of this paper is to study the mechanism of the phenomenon named "frequency-shift", which comes from the common observation of nonlinear dynamic characteristic in spacecraft ground vibration test. The frequency response exhibits softening trend during frequency-sweep excitation. Research object in this work consists of a beam clamped at one end and connected by a nonlinear sleeve joint at the other. The joint nonlinearities include longitudinal retaining force, in-plane friction force, preload, coefficient of in-plane friction force and clearance. Their effects on the special characteristic are deter- mined through modal analysis. Additionally, uniform load driving is considered. While discussing the nonlinearity of clearance, an approach called Relative Mode Transfer Method (RMTM) is proposed to treat the impacting system, which is based on mode transfer principle. In particular, the responses are obtained either with or without considering preload. Several key factors which can lead to "frequency-shift" are confirmed. The findings are valuable to gain a further insight. [ABSTRACT FROM AUTHOR]

In order to meet the demand for accurate identification of distant targets by improving the resolution of multi-scale imaging systems, from primary lenses focus, a design scheme of a multi-scale long-focal imaging system based on the Tessar primary lenses is proposed in this paper. Two constraints that need to be added to the primary lenses for meeting the linear arrangement of secondary lenses are analyzed. In response to the problem of the imaging quali-ty degradation of the system as the off-axis angle of the secondary lenses array increases, synergy optimization is applied to the secondary lenses in adjacent areas. Additionally, free-form surface types are used to correct aberrations in the off-axis position optimization of the secondary lenses. The MTF curves of different field-of-view areas are consistent, showing that the system achieves ideal imaging quality across the full field of view. The spatial resolution of the multi-scale imaging system designed using the Tessar primary lenses structure is 14 μrad. Compared to multi-scale systems based on concentric spherical lenses, it is significantly higher.

为扩大大豆油的应用范围，采用脂肪酶Novozym435催化大豆油环氧化改性合成环氧大豆油，对环氧大豆油进行了红外光谱和核磁共振氢谱表征，并考察其流变学和摩擦学性能。结果表明：成功合成了环氧大豆油；相较于大豆油，环氧大豆油的黏度指数增大，黏温性能更优异；相较于矿物润滑油和大豆油，环氧大豆油的平均摩擦系数及磨损体积减少率分别为21.6%、17.0%和71.2%、64.9%，减摩抗磨性能显著提升。环氧大豆油可在摩擦表面形成致密、厚实的物理化学吸附膜，从而有效减摩抗磨，提高润滑性。In order to expand the application range of soybean oil (SO), lipase Novozym435 was used to catalyze the epoxidation modification of SO to synthesize epoxidized soybean oil (ESO), and the ESO was characterized by infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy, and its rheological and tribological properties were investigated. The results showed that the ESO was successfully synthesized; compared with SO, the viscosity index of ESO increased, and the viscosity-temperature performance was better; compared with mineral lubricant and SO, the reduction rates of average friction coefficient and wear volume of the ESO were 21.6%, 17.0%, and 71.2%, 64.9%, respectively, and the friction and wear reduction performance was significantly improved. ESO can form a dense, thick physicochemical adsorption film on the friction surface, thus effectively reducing friction and anti-wear and improving lubricity.

ObjectiveTo examine the equity in human resources allocation in centers for disease prevention and control (CDCs) and to provide evidences for optimizing resource allocation. Methods The data on human resources among CDCs in all administrative regions across China in 2014 and 2019 were collected from China′s Statistical Yearbook of Health and Family Planning – 2015 and China′s Statistical Yearbook of Health – 2020. Then, health resource agglomeration degree (HRAD) was used to evaluate the equity in human resources allocation according to population and geographical area. Results The total number of personnel in CDCs across China decreased by 2.51% from 192 397 in 2014 to 187 564 in 2019. The number of CDCs′ personnel per 10 000 population also showed a shrinking trend at all provincial levels and the number for most provincial level regions did not meet the national standard. In 2019, the proportions of CDC personnel at young age (< 35 years) and middle-aged (35 – 54 years) decreased by 3.8% and 2.4% compared with those in 2014, but the proportion of elderly personnel (≥ 55 years) increased by 6.0% contrasting to that in 2014. The number of personnel with high school/technical secondary school education or below in all CDCs in China decreased from 28.8% in 2014 to 19.4% in 2019, while the number of those with junior college education or above increased from 71.1% in 2014 to 80.6% in 2019. The results of analysis on the equity in human resources allocation showed that the spatial distribution of human resource was unbalanced. The geographical region-specific HRAD index was the highest (indicating a better equity in human resources allocation) for eastern region, followed by that for central and western region; while, the population distribution-specific HRAD index was higher for western region than that for central and eastern region. Conclusion Insufficient total number, serious turnover and unbalanced allocation are main problems in health resources allocation for CDCs in China and the situation needs to be improved for CDCs′ capability construction in China.

How to consecutively track the boost phase and coast phase transitions without any prior information has become a pressing issue. Solving the problem with interacting multiple model is a feasible method. Since the Markov parameter of conventional interacting multiple model is constant, the model switching slows down. An adaptive Markov parameter IMM (AMP-IMM) algorithm is developed based on the modification of posterior information. The Markov transition probabilities can be modified adaptively in the process of filtering by omitting the information of non-matching model and magnifying the matching model information simultaneously during switching. The algorithm accelerates system convergence speed. Simulation results show that the proposed algorithm can consecutively track BM from the boost phase to the coast phase and is more effective than the conventional interacting multiple model. [ABSTRACT FROM AUTHOR]

With the rapid urbanization and industrialization, heavy metal contamination in urban soil and surface dust has received particular attention due to its negative effects on the eco-environment and human health. Contamination and spatio-temporal characteristics, contamination sources, and source apportionment methods, as well as the ecological and health risks of heavy metals in urban soil and surface dust were reviewed. The knowledge gaps in current research and prospects of future works were proposed. Four key points were presented, including improving the research on the interaction mechanism of heavy metals in urban soil and surface dust under complex conditions, enriching verification methods to improve the source apportionment reliability of anthropogenic metals by receptor models, strengthening the research on chemical forms of heavy metals from different sources and their short-term accumulation processes in surface dust, and raising the credibility of ecological and health risk forecast of heavy metals by integrating the improved exposure parameters and chemical forms.

Nowadays, China is faced with two strategic tasks:improving ecological environmental quality and realizing carbon neutrality and carbon peaking. Synergy to reduce pollution and carbon emissions has become an inevitable choice for the comprehensive green transition of economic and social development in China. The electric power sector will play an important role in the transition process. Based on different power demand scenarios, a multi-objective model was constructed to achieve carbon peaking and carbon neutrality at a low cost, and the optimal path scheme of carbon emission reduction synergy was obtained. The results showed that under the premise of achieving carbon peaking and carbon neutrality as scheduled, pollution reduction and carbon reduction had good synergies, and their synergistic control could effectively facilitate the realization of the low-carbon transition. Optimizing the power generation structure of the electric power sector was the key measure to achieving the synergistic effect of pollution reduction and carbon reduction. During the study period, the proportion of thermal power decreased continuously, and the proportion of clean power exceeded 92.5%. The emissions of carbon dioxide and major air pollutants were significantly different under different power demands. Carbon dioxide emissions were most affected by power demand. The peak carbon dioxide emissions under low power demand, medium power demand, and high power demand were 9.416 billion, 10.409 billion, and 10.746 billion t, respectively. The emissions of sulfur dioxide, nitrogen oxide, and particulate matter also showed an increasing trend in the low power demand, medium power demand, and high power demand scenarios. The increase in power demand only increased the pressure of power generation structure adjustment within the electric power sector, without affecting the output and activity level of other sectors, that is, the pressure of emission reduction in the electric power sector caused by power demand did not show the trend of transmission between sectors.

The tumor microenvironment (TME), the environment of tumorigenesis and tumor progression, incorporates multiple types of cells and non-cellular components. TME plays an important role in tumorigenesis and tumor progression. Due to the abnormal proliferation of tumors, the TME has a unique chemophysiology environment and complex metabolic patterns, which subsequently affects the role of immune cells. Understanding the metabolic patterns of TME can help us develop immunotherapy regimens that target TME. Microbial metabolism and lipid metabolism, the key metabolic processes of TME, have emerged as important foci of research. The metabolites released by the microbiome and the reprogramming of cellular lipid metabolism affect the subsistence of tumor and immune cells. In this review, we summarized the composition and metabolic characteristics of TME and discussed the latest research progress in microbial metabolism and lipid metabolism in TME. We also provided an update on relevant metabolic regulatory targets and immunotherapy strategies, stressing that identifying highly effective therapeutic targets, in spite of the apparent difficulty, is what future research should be focused on., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Groundwater is an important water source in the central Guohe River basin but pollution and water quality deterioration present a significant challenge. Here, 80 groups of groundwater samples were collected between June and September 2019 including 61 groups of shallow groundwater samples, 9 groups of middle groundwater samples, and 10 groups of deep groundwater samples. The hydrochemical characteristics and formation mechanisms of groundwater at these different depths were analyzed using statiatical techniques, Piper triangular diagrams, Gibbs figures, and ion ratios. The following results were noted:① Groundwater is weakly alkaline overall, and the dominant anion and cation at different depths were HCO 3 - and Na + . The shallow and deep groundwater mainly consist of fresh water while the middle groundwater is mainly brackish water. The hydrochemical typology of the shallow groundwater was mainly HCO 3 -Ca·Mg and HCO 3 -Na·Mg. HCO 3 ·SO 4 ·Cl-Na was found to be the dominant hydrochemical typology in the middle and deep groundwater. ② The chemical composition of the groundwater shows notable vertical variations. With depth, the mean mass concentrations of TDS, Na + , Mg 2+ , Cl - , SO 4 2- , and HCO 3 - first increase and then decreasing, while the mean mass concentration of Ca 2+ gradually decreases. These vertical differences are closely related to the sedimentary environment of the aquifer and the intensity of water-rock interaction. ③ The formation of groundwater hydrochemical characteristics is influenced by water-rock interactions, cation exchange, and human activities, with water-rock interaction dominated by sodium silicate dissolution. Human activities generally have the greatest impact on the shallow groundwater. ④ The water quality of the deep groundwater is notably better than that of the shallow and middle groundwater. However, excessive exploitation of the deep groundwater resource has led to the formation of a regional groundwater funnel, enhancing the difference in middle and deep groundwater levels. To reduce the risk of ground subsidence and the contamination of the deep water with middle brackish water, deep groundwater exploitation wells should be carefully positioned and regulated.

Human breast cancer resistance protein (BCRP), an ATP-binding cassette (ABC) efflux transporter, is mainly responsible for the transport of many endogenous and xenobiotics. BCRP is expressed in different tissues, such as placental, intestinal epithelium, endothelial cells of brain microvessels, and renal proximal tubular cells. BCRP is considered as one of the key factor for the drug-drug interaction and individual difference in drug therapy. The review will provide an overview of the current knowledge on the discovery of BCRP and its physical function, transport mechanism, substrate and inhibitors, as well as its effect on the drug pharmacokinetics.

Objective: To observe effects and mechanism of Dinggui gel paste analgesic anti-inflammatory., Methods: Eighty-four male KM mice weighted from 18 to 22 g and aged 4 to 5 weeks were randomly divided into 7 groups, named blank group, model group, matrix control group, Votalin group, high dosage of Dinggui gel paste group with group, equivalent dosage of Dinggui gel paste group, Dinggui gel paste group, 12 mice in each group. Except blank and model group, the other groups were paste ointment for 7 days, and one time a day, matrix control group were pasted isodose blank matrix gel patch. Pain threshold were tested at 30, 60, 90 and 120 min after the last ad-ministration. Hot plate test were performed by injection of 5% formalin for 20 µL on right hindfoot sole after the last administration. The cumulative time of mice licking right rear foot were observed at stage of I and II, and content of IL-1, TNF-α were tested by ELISA method. Differences of weight between right and left ears were measured by ear swelling method and anti-inflammation experiment., Results: In hot plate test at 90 min, pain threshold in equivalent dosage of Dinggui gel paste group was (24.87 ± 14.67) s and (15.28 ± 8.23) s in model group; (26.33 ± 15.45) s in high dosage of Dinggui gel paste group and (15.31 ± 5.02) s in model group at 120 min in hot plate test, there were no statistical differences between two groups. Pain period at stage I, licking cumulative time in high dosage of Dinggui gel paste group was (66.70 ± 22.83) s and (101.80 ± 33.65) s in model group,and had significant differences between two groups; there were statistical differences in licking cumulative time at stage I of pain period among high dosage of Dinggui gel paste group (51.30 ± 43.60)s, equivalent dosage of Dinggui gel paste group (64.00 ± 47.27) sand model group (109.50 ± 36.78) s. Content of IL-1 in model group was (28.70 ± 8.24) ng/L and (13.33 ± 2.20) ng/L in high dosage of Dinggui gel paste group, there was obvious meaning between two groups; There were significant differences in TNF-α content among model group (93.60 ± 23.65) ng/L,high dosage of Dinggui gel paste group (63.21 ± 10.54)ng/L and equivalent dosage of Dinggui gel paste group (72.69 ± 16.26) ng/L; while there were no statistical meaning in ear swelling degree among model group (5.73 ± 0.80) mg,high dosage of Dinggui gel paste group (5.42 ± 0.68) mg and equivalent dosage of Dinggui gel paste group (4.98 ± 1.52) mg., Conclusion: Dinggui gel paste could increase pain threshold, reduce licking accumulative time, and decrease ear swelling degree, and relief pain by regulating level of TNF-α and IL-1.

Effect of interactions between boron (B) and antimony on the uptake and accumulation by rice (Oryza sativa L.) seedling was investigated in solution culture. The results showed that Sb(III) and Sb(V) could inhibit rice growth and Sb(III) was more toxic than Sb(V). Concentrations of B in rice roots and shoots were significantly affected by the addition of Sb(III) and Sb(V). The addition of 30 μmol x L(-1) Sb(III) could significantly decrease B of rice shoots and roots by 57.6% and 75.6%, and 30 μmol x L(-1) Sb(V) could decrease B of rice roots by 16.0%, compared with the control treatment, when the B concentration was 0.5 mg x L(-1). Equally, adding B also significantly affected the concentrations of Sb in rice roots and shoots. The addition of 2.0 mg x L(-1) B could decrease the concentrations of Sb in rice roots and shoots,by 39.1% and 9.2%, respectively, compared with 0.5 mg x L(-1) B, when the Sb(III) concentration was 10 μmol x L(-1). Adding 2.0 mg x L(-1) B could decreasd Sb concentrations in rice roots by 13.9%, compared with 0.5 mg x L(-1) B, when the Sb(V) concentration was 10 μmol x L(-1). Furthermore, adding B had significant effect on bioaccumulation factor and distribution ratio of Sb in rice roots and shoots. The results of the study demonstrated that Sb pollution in farmland could be alleviated by adding B fertilizer, thus protecting human health from Sb pollution.

Rare earth elements content in farmland soils and crops of the surrounding copper mining and smelting plant in Jiangxi province was studied. The results showed that copper mining and smelting could increase the content of rare earth elements in soils and crops. Rare earth elements content in farmland soils of the surrounding Yinshan Lead Zinc Copper Mine and Guixi Smelting Plant varied from 112.42 to 397.02 mg x kg(-1) and 48.81 to 250.06 mg x kg(-1), and the average content was 254.84 mg x kg(-1) and 144.21 mg x kg(-1), respectively. The average contents of rare earth elements in soils in these two areas were 1.21 times and 0.68 times of the background value in Jiangxi province, 1.36 times and 0.77 times of the domestic background value, 3.59 times and 2.03 times of the control samples, respectively. Rare earth elements content in 10 crops of the surrounding Guixi Smelting Plant varied from 0.35 to 2.87 mg x kg(-1). The contents of rare earth elements in the leaves of crops were higher than those in stem and root. The contents of rare earth elements in Tomato, lettuce leaves and radish leaves were respectively 2.87 mg x kg(-1), 1.58 mg x kg(-1) and 0.80 mg x kg(-1), which were well above the hygienic standard limit of rare earth elements in vegetables and fruits (0.70 mg x kg(-1)). According to the health risk assessment method recommended by America Environmental Protection Bureau (USEPA), we found that the residents' lifelong average daily intake of rare earth elements was 17.72 mg x (kg x d)(-1), lower than the critical value of rare earth elements damage to human health. The results suggested that people must pay attention to the impact of rare earth elements on the surrounding environment when they mine and smelt copper ore in Jiangxi.

Gindenosides are the active ingredients of Panax ginseng. 20 (S) -protopanaxadiolocotillol type epimers are the main metabolites of 20 (S) -protopanaxadiol. The previous studies showed that there are stereoselectivity difference in pharmacodynamics and pharmacokinetics between 24R-epimer and 24S-epimer. The purpose of this study was to explore the excretion of the epimers in bile, feces and urine of rat. Liquid chromatography tandem mass spectrometry method has been performed for determination of 24R-epimer and 24S-epimer in bile, feces and urine. 24R-epimer or 24S-epimer was intragastric administered to rats at a single dose of 10 mg x kg(-1). Results showed that after administration the recovery of 24R-epimer and 24S-epimer in feces was 17.69% and 17.09%, respectively, while both of the two epimers were hardly detected in urine. The 48 h cumulative biliary excretion rate of 24R-epimer was 8.01% after administration, while only 1.47% for 24S-epimer. It indicated that there are stereoselectivity in biliary excretion of the epimers with intragastric administration.

This study was aimed to investigate the therapeutic effect of two molecular targeted therapeutic drugs, tyrosine kinase inhibitors gefitinib and lapatinib, on JAK2 V617F positive myeloproliferative disorders (MPD). The human leukemia cell line (HEL cell line) carrying JAK2 V617F mutation was treated with gefitinib (0.5, 1, 5, 10, 25 µmol/L) and lapatinib (0.5, 1, 2, 4, 8, 16 µmol/L) respectively. MTT method was used to detect HEL cell proliferation. The apoptotic rate and cell cycle were measured by flow cytometry. The results showed that gefitinib could significantly inhibit the proliferation of HEL cells in a dose-dependent manner, it's correlation coefficients for 24 and 48 h were 0.991 and 0.895 respectively. IC(50) at 48 h was 5.4 µmol/L. Gefitinib could effectively induce apoptosis of HEL cells in a dose-dependent manner (r = 0.896). Otherwise, gefitinib could arrest HEL cells at G(0)/G(1) phase. The inhibitory effect of lapatinib was less than gefitinib, it's IC(50) of inhibiting proliferation of HEL cells was 19.6 µmol/L. It is concluded that both gefitinib and lapatinib can inhibit the proliferation of HEL cells. These two tyrosine kinase inhibitors can be used for researching of targeted therapy of JAK2 V617 positive MPD.

In the area around an antimony-lead smelter, soil and soil water samples were collected from different soil profiles in vegetable field, uncultivated field and wood field. The distribution and migration of heavy metals in soil profile were investigated. In soil, Sb, Pb, Cu and Cd are found to accumulate in the topsoil layer, and decrease rapidly with the depth. However, Sb, Pb, and As appear to accumulate below 60 cm. Sb and As show a much stronger affinity to the pore water than Pb. In consequence, different soil utilization types lead to different effects of heavy metals migration in soil profile. Furthermore, Sb and As show a higher potential to migrate along the soil profile than that of Pb. In addition, the high content of heavy metals in the topsoil may be absorbed by crops post to desorption in soil water, and possibly form a threat to human health.

This paper presents a new gas flow measurement system, which works by calorimetric sensors and DSP wavelet transform signal processing. The system is achieved by specific hardware including flow sensors, voltage amplifier, A/D converter, DSP, heat control circuits as well as supporting software and algorithm. The main advantages of the scheme include its high precision, stable performance and high noise rejection. It can be applied to especially under small tidal volume and low-flow conditions.

The characteristics of chloramphenicol and tetracyclines in municipal sewage and Naming River of Guiyang City were studied, using solid-phase extraction with high-performance liquid chromatography-UV detection. The average concentration of chloramphenicol, oxytetracycline, tetracycline and chlortetracycline in municipal sewage is 27.0, 2.3, 11.0 and 1.1 microg x L(-1) at northern outfall, and 21.2, 2.1, 9.5 and 0.5 microg x L(-1) at southern outfall. Nanming River is influenced by many antibiotic sources which include agriculture land, surface waste and municipal sewage, and the municipal sewage is the most important one. The concentration of chloramphenicol, oxytetracycline and tetracycline in river water ranges from 2.1 to 19.0 microg x L(-1), ND to 3.0 microg x L(-1) and 0.8 to 6.8 microg x L(-1) in winter, and 0.2 to 1.3 microg x L(-1), ND to 0.03 microg x L(-1), 0.2 to 0.3 microg x L(-1) in summer. Chlortetracycline was only detected in winter with the concentration range of 0.09 to 0.14 microg x L(-1). The average concentration of the four compounds in sediment is 147.6, 76.6, 99.2 and 1.6 microg x kg(-1) in winter, 195.8, 89.1, 34.4 and 9.0 microg x kg(-1) in summer, respectively. The antibiotics concentration of both river water and sewage shows a seasonal variation.