This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact...This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact time constraints of guidance law(ITCG) is derived by using sliding mode control(SMC) and Lyapunov stability theorem. The expected impact time is realized by using the notion of attack process and estimated time-to-go to design sliding mode surface(SMS). ITCG contains equivalent and discontinuous guidance laws, once state variables arrive at SMS,the equivalent guidance law keeps the state variables on SMS,then the discontinuous guidance law enforces state variables to move and reach SMS. The singularity problem of ITCG is also analyzed. Theoretical analysis and numerical simulation results are given to test the effectiveness of ITCG designed in this paper.展开更多
Recently,drug-drug cocrystal attracts more and more attention.It offers a low risk,low-cost but high reward route to new and better medicines and could improve the physiochemical and biopharmaceutical properties of a ...Recently,drug-drug cocrystal attracts more and more attention.It offers a low risk,low-cost but high reward route to new and better medicines and could improve the physiochemical and biopharmaceutical properties of a medicine by addition of a suitable therapeutically effective component without any chemical modification.Having so many advantages,to date,the reported drug-drug cocrystals are rare.Here we review the drug-drug cocrystals that reported in last decade and shed light on the opportunities and challenges for the development of drug-drug cocrystals.展开更多
基于本地化差分隐私的多维分析查询(multi-dimensional analytical query,MDA)已得到了研究者的广泛关注.现有基于最优局部哈希(optimal local Hashing,OLH)机制与层次树结构的扰动方法存在泄露根结点隐私的风险.针对现有结合层次树结...基于本地化差分隐私的多维分析查询(multi-dimensional analytical query,MDA)已得到了研究者的广泛关注.现有基于最优局部哈希(optimal local Hashing,OLH)机制与层次树结构的扰动方法存在泄露根结点隐私的风险.针对现有结合层次树结构的本地扰动机制不足,提出了一种有效且满足本地化差分隐私的MDA查询算法H4MDA (hierarchical structure for MDA),该算法充分利用层次树的横向与纵向结构特征设计了3种基于用户分组策略的本地扰动算法HGRR,LGRR-FD,LGRR.算法HGRR结合层次树横向结构与GRR机制本地扰动用户元组数据,通过摈弃根结点组合来响应MDA查询.不同于HGRR,LGRR-FD算法利用层次树的纵向结构与GRR机制扰动本地数据,同时通过添加假数据来避免叶子结点的隐私泄露.LGRR算法通过摈弃叶子结点层纵向扰动本地数据.收集者结合LGRR的扰动结果利用局部一致性处理技术重构层次树最后两层,通过添加虚拟叶子结点来响应MDA查询,而虚拟叶子结点计数之和等于其父节点计数.HGRR,LGRR-FD,LGRR算法与现有扰动算法在3种数据集上实验结果表明,其响应MDA查询的精度优于同类算法.展开更多
The Tibetan Plateau(TP)is a key region for environmental and climatic research due to its significant linkages with large-scale atmospheric circulation.Understanding the long-term moisture evolution pattern and its fo...The Tibetan Plateau(TP)is a key region for environmental and climatic research due to its significant linkages with large-scale atmospheric circulation.Understanding the long-term moisture evolution pattern and its forcing mechanisms on the TP during the Holocene may provide insights into the interaction between low-latitude climate systems and midlatitude westerlies.Here,we synthesized 27 paleoclimate proxy records covering the past 9500 years.The results of the rotated empirical orthogonal function analysis of the moisture variation revealed spatial-temporal heterogeneity,which was classified into 5 subregions.Proxy records were then compared with the results from the Kiel Climate Model and other paleorecords.The results showed that moisture evolution on the western-southern-central TP was controlled by the Indian summer monsoon(ISM).On the south-eastern TP,moisture change was affected by the interplay between the East Asian summer monsoon(EASM)and the westerlies,as well as the ISM.With diverse patterns of circulation system precipitation,moisture changes recorded in the paleorecords showed spatial-temporal discrepancies,especially during the early to middle Holocene.Moreover,given the anti-phase pattern of summer precipitation in the EASM area under El Nino/Southern Oscillation(ENSO)conditions and the unstable relationship between the ISM and ENSO,it is reasonable to conclude that relatively strong ENSO variability during the late Holocene has contributed to these discrepancies as Asian summer monsoon precipitation has declined.展开更多
A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated p...A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated precursors changed greatly after the source water switching.Average concentrations of N-nitrosodimethylamine（NDMA）,N-nitrosomorpholine（NMOR）,and N-nitrosopyrrolidine（NPYR） in the finished water were6.9,3.3,and 3.1 ng/L,respectively,from June to October when the Luan River water was used as source water,while those of NDMA,N-nitrosomethylethylamine（NMEA）,and NPYR in the finished water were 10.1,4.9,and 4.7 ng/L,respectively,from November to next April when the Yellow River was used.NDMA concentration in the finished water was frequently over the 10 ng/L,i.e.,the notification level of California,USA,which indicated a considerable threat to public health.Weak correlations were observed between N-nitrosamine yield and typical water quality parameters except for the dissolved organic nitrogen.展开更多
A GAC-sand dual media filter （GSF） was devised as an alternative solution for drinking water treatment plant to tackle the raw water polluted by ammonium in place of expensive ozone-GAC processes or bio-pretreatment...A GAC-sand dual media filter （GSF） was devised as an alternative solution for drinking water treatment plant to tackle the raw water polluted by ammonium in place of expensive ozone-GAC processes or bio-pretreatments. The ammonium removal pathways and microbial community in the GSFs were investigated. The concentrations of ammonium, nitrite and nitrate nitrogen were monitored along the filter. Total inorganic nitrogen （TIN） loss occurred during the filtration. For 1 mg ammonium removal, the TIN loss was as high as 0.35 mg, DO consumption was 3.06 mg, and alkalinity consumption was 5.55 rag. It was assumed that both nitrification and denitrification processes occur in the filters to fit the TIN loss and low DO consumption. During the filtration, nitritation, nitrification and nitritation-anaerobic ammonium oxidation processes probably occur, while traditional nitrification and denitrification and simultaneous nitrification and denitrification processes may occur. In the GSFs, Nitrosomonas and Nitrospira are likely to be involved in nitrification processes, while Novosphingobium, Comamonadaceae and Oxalobacteraceae may be involved in denitrification processes.展开更多
Four sampling campaigns were conducted in two years to understand the fluctuation of N-Nitrosamines(NAs) and their precursors in one drinking water treatment plant(DWTP) in East China in different seasons.This water s...Four sampling campaigns were conducted in two years to understand the fluctuation of N-Nitrosamines(NAs) and their precursors in one drinking water treatment plant(DWTP) in East China in different seasons.This water supply system has been facing several nitrosamine challenges related with source water, including the switch of water source,high concentration of ammonium, formed NAs and NA formation potential(FP) in source water.Besides, the use of ozonation in the DWTP and chloramination in networks will increase the NDMA concentration in tap water.To address these challenges, the biopretreatment was applied in this DWTP to decrease the concentration of ammonium and NAs.The following biological activated carbon(BAC) will neutralize the nitrosamine increase brought by ozonation.The use of free chlorine in disinfection process will also decrease the NDMA formation compared with chloramination.The results will benefit other cities in China and other countries with similar impacted water sources.展开更多
Powdered activated carbon（PAC） adsorption of two fishy odorants, trans,trans-2,4-heptadienal（HDE） and trans,trans-2,4-decadienal（DDE）, was investigated. Both the pseudo first-order and the pseudo second-order ki...Powdered activated carbon（PAC） adsorption of two fishy odorants, trans,trans-2,4-heptadienal（HDE） and trans,trans-2,4-decadienal（DDE）, was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters（ΔG^0, ΔH^0, and ΔS^0） indicated an exothermic and spontaneous adsorption process. PAC dosage, p H, and natural organic matter（NOM） presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of p H had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at p H 9. The presence of NOM, especially the fraction with molecular weight less than1 k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did.展开更多
A red water phenomenon occurred in several communities few days after the change of water source in Beijing, China in 2008. In this study, the origin of this problem, the mechanism of iron release and various control ...A red water phenomenon occurred in several communities few days after the change of water source in Beijing, China in 2008. In this study, the origin of this problem, the mechanism of iron release and various control measures were investigated. The results indicated that a significant increase in sulphate concentration as a result of the new water source was the cause of the red water phenomenon. The mechanism of iron release was found that the high-concentration sulphate in the new water source disrupted the stable shell of scale on the inner pipe and led to the release of iron compounds. Experiments showed that the iron release rate in the new source water within pipe section was over 11-fold higher than that occurring within the local source water. The recovery of tap water quality lasted several months despite ameliora- tive measures being implemented, including adding phosphate, reducing the overall proportion of the new water source, elevating the pH and alkalinity, and utilizing free chlorine as a disinfectant instead of chloramine. Adding phosphate was more effective and more practical than the other measures. The iron release rate was decreased after the addition of 1.5 mg. L-1 orthophosphate- P, tripolyphosphate-P and hexametaphosphate-P by 68%, 83% and 87%, respectively. Elevating the pH and alkalinity also reduced the iron release rate by 50%. However, the iron release rate did not decreased after replacing chloramine by 0.5-0.8 mg. L-1 of free chlorine as disinfectant.展开更多
An investigation into emergency potable water treatment technologies was conducted to investigate China’s water pollution situation.In order to confirm optimum parameters,the technological efficiency of each pollutan...An investigation into emergency potable water treatment technologies was conducted to investigate China’s water pollution situation.In order to confirm optimum parameters,the technological efficiency of each pollutant was obtained.About 100 contaminants were tested to find the emergency treatment technologies,most of which were found to be positive.This paper presents the three largest and most significant water pollution incidents in China to date,analyzing cases such as the nitrobenzene pollution incident in the Songhua River in November 2005,the cadmium pollution incident in the Beijiang River in December 2005,and the water crisis with odorous tap water in Wuxi City in May 2007.展开更多
XAD-8 resin isolation of organic matter in water was used to divide organic matter into the hydrophobic and hydrophilic fractions. A pilot plant was used to investigate the change in both fractions during conventional...XAD-8 resin isolation of organic matter in water was used to divide organic matter into the hydrophobic and hydrophilic fractions. A pilot plant was used to investigate the change in both fractions during conventional and advanced treatment processes. The treatment of hydrophobic organics （HPO）, rather than hydrophilic organicas （HPI）, should carry greater emphasis due to HPO’s higher trihalomethane formation potential （THMFP） and haloacetic acid formation potential （HAAFP）. The removal of hydrophobic matter and its transmission into hydrophilic matter reduced ultimate DBP yield during the disinfection process. The results showed that sand filtration, ozonation, and biological activated carbon （BAC） filtration had distinct influences on the removal of both organic fractions. Additionally, the combination of processes changed the organic fraction proportions present during treatment. The use of ozonation and BAC maximized organic matter removal efficiency, especially for the hydrophobic fraction. In sum, the combination of pre-ozonation, conventional treatment, and O 3 -BAC removed 48% of dissolved organic carbon （DOC）, 60% of HPO, 30% of HPI, 63% of THMFP, and 85% of HAAFP. The use of conventional treatment and O 3 -BAC without pre-ozonation had a comparable performance, removing 51% of DOC, 56% of HPO, 45% of HPI, 61% of THMFP, and 72% of HAAFP. The effectiveness of this analysis method indicated that resin isolation and fractionation should be standardized as an applicable test to help assess water treatment process efficiency.展开更多
N-nitrosodimethylamine （NDMA） and several other N-nitrosamines have been detected as disinfection by-products in drinking waters in many countries around the world. An ultra-performance liquid chromatography- tandem...N-nitrosodimethylamine （NDMA） and several other N-nitrosamines have been detected as disinfection by-products in drinking waters in many countries around the world. An ultra-performance liquid chromatography- tandem mass spectrometry method with solid phase extraction sample preparation was developed to study the occurrence of N-nitrosamines in several water treatment plants and distribution systems in China. Isotope labeled N-nitrosodi-n-propylamine-dl4 （NDPA-dl4） was selected as the internal standard for quantification. The solid phase extraction procedures including pH, enrichment process and MS/MS parameters including capillary voltage, cone gas flow, cone voltage, collision energy were optimized to give average recoveries of 26% to 112% for nine N- nitrosamine species. The instrument detection limits were estimated to range from 0.5 to 5μg.L-1 for the nine N- nitrosamine species. NDMA and several other N-nitrosa- mines were found at fairly high concentrations in several water treatment plants and distribution systems. NDMA was found in all locations, and the highest concentrations in cities B, G, T, and W were 3.0, 35.7, 21.3, and 19.7 ng. L 1, respectively. A wide range of N-nitrosamines concentrations and species were observed in different locations. Higher concentrations of N-nitrosamines were detected in distribution systems that were further away from the treatment plants, suggesting that the contact time between the residual disinfectant and natural organic matter may play an important role in the formation of these compounds.展开更多
Non-small-cell lung cancer （NSCLC）, the most common type of lung cancer accounting for 85% of the cases, is often diagnosed at advanced stages owing to the lack of efficient early diagnostic tools. 5-Hydroxymetbylcy...Non-small-cell lung cancer （NSCLC）, the most common type of lung cancer accounting for 85% of the cases, is often diagnosed at advanced stages owing to the lack of efficient early diagnostic tools. 5-Hydroxymetbylcytosine （ShmC） signatures in circulating cell-free DNA （cfDNA） that carries the cancer-specific epigenetic patterns may represent the valuable biomarkers for discriminat- ing tumor and healthy individuals, and thus could be potentially useful for NSCLC diagnosis. Here, we employed a sensitive and reliable method to map genome-wide 5hmC in the cfDNA of Chinese NSCLC patients and detected a significant 5hmC gain in both the gene bodies and promoter regions in the blood samples from tumor patients compared with healthy controls. Specifically, we identi- fied six potential biomarkers from 66 patients and 67 healthy controls （mean decrease accuracy 〉 3.2, P 〈 3.68E-19） using machine-learning-based tumor classifiers with high accuracy. Thus, the unique signature of 5hmC in tumor patient＇s cfDNA identified in our study may provide valuable information in facilitating the development of new diagnostic and therapeutic modalities for NSCLC.展开更多
It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the d...It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the development of practical treatment technologies. In this study, dissolved organic matter （DOM） from two source waters was fractionated with XAD resins and ultra- filtration membranes. The N-nitrosamine formation potential （FP） （ng of N-nitrosamines formed per mg of dissolved organic carbon （DOC）） from raw water and each fraction were measured and correlated with the fluorescence excitation-emission matrix （EEM）, molecular weight （MW） and other assays. The results showed that the hydrophilic fraction had N-nitrosamine FP 1.3 to 3.5 times higher than the hydrophobic fraction from both source waters. The DOM fraction with low MW was the dominant fraction in these two source waters and contributed more precursors for N-nitrosamine formation than the larger MW fraction. The EEM spectra indicated there were notable amounts of soluble microbial products （SMPs） and aromatic proteins in the two studied rivers, which probably originated from wastewater discharge. The SMPs tended to be more closely correlated with N-nitrosodimethylamine formation potential than the other DOM components. Higher N-nitrosamine FP were also related to fractions with lower DOC/DON ratios and lower SUVA254 values.展开更多
The qualified finished water from water treatment plants(WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems(DWDSs), which affected tap water quality seriously. Th...The qualified finished water from water treatment plants(WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems(DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.展开更多
This study focused on evaluating the efficiency of powdered activated carbon （PAC） adsorption process and tackling chlorobenzenes and chlorophenols spill in drinking water source. The adsorption kinetics and PAC＇s ...This study focused on evaluating the efficiency of powdered activated carbon （PAC） adsorption process and tackling chlorobenzenes and chlorophenols spill in drinking water source. The adsorption kinetics and PAC＇s capacities for five chlorobenzenes and three chlorophenols at drinking water contamination levels were studied in order to determine the influence of different functional groups on the adsorption behavior. The results showed that PAC adsorption could be used as an effective emergency drinking water treatment process to remove these compounds. The adsorption kinetics took 30 min to achieve nearly equilibrium and could be described by both pseudo first-order and pseudo second-order models. A mathematic relationship was developed between the pseudo first-order adsorption rate constant, k1, and the solutes＇ properties including lgKow, polarizability and molecular weight. The Freundlich isotherm equation could well describe the adsorption equilibrium behaviors of chlorinated aromatics with r2 from 0.920 to 0.999. The H-bond donor/acceptor group, hydrophobicity, solubility and molecular volume were identified as important solute properties that affect the PAC adsorption capacity. These results could assist water professionals in removing chlorinated aromatics during emergency drinking water treatment.展开更多
The aim of the research was to investigate the pharmacokinetics(PK) of enteric-coated mycophenolate sodium(EC-MPS) by quantification of the active metabolite of mycophenolic acid(MPA)after multiple escalating oral dos...The aim of the research was to investigate the pharmacokinetics(PK) of enteric-coated mycophenolate sodium(EC-MPS) by quantification of the active metabolite of mycophenolic acid(MPA)after multiple escalating oral doses in Han kidney transplant recipients. A total of 28 Han postoperative kidney transplant recipients were given a multiple-dose of 540, 720 or 900 mg of EC-MPS two times a day in combination with tacrolimus for 6 days. Blood specimens were collected at each time point from0 to 12 h after EC-MPS administration. MPA plasma concentrations were measured by UPLC–UV. The relationship between the EC-MPS dose and its PK parameters was assessed. In the range from 540 to900 mg, C_(max) and AUC_(0–12h) did not increase with dose escalation. The AUC_(0–12h), C_(max), C_0 and T_(max) for the 540 720 and 900 mg doses were not significantly different, respectively(P 40.05). AUC_0–12 h and C_(max) were increased less than proportionally with increasing EC-MPS dose levels. Inter-individual variability in AUC_(0–12h), C_(max) and C_0 were considerable. Nonlinear PK relationships were found from the doses of 540–900 mg of EC-MPS.展开更多
The extensive use of antibiotics has led to their presence in the aquatic environment, and introduces potential impacts on human and ecological health. The capability of powdered activated carbon （PAC） to remove six...The extensive use of antibiotics has led to their presence in the aquatic environment, and introduces potential impacts on human and ecological health. The capability of powdered activated carbon （PAC） to remove six frequently used quinolone （QN） antibiotics during water treatment was evaluated to improve drinking water safety. The kinetics of QN adsorption by PAC was best described by a pseudo second-order equation, and the adsorption capacity was well described by the Freundlich isotherm equation. Isotherms measured at different pH showed that hydrophobic interaction, electrostatic interaction, and dispersion force were the main mechanisms for adsorption of QNs by PAC. A pH-dependent isotherm model based on the Freundlich equation was developed to predict the adsorption capacity of QNs by PAC at different pH values. This model had excellent prediction capabilities under different laboratory scenarios. Small relative standard derivations （RSDs）, i.e., 0.59%-0.92% for ciprofloxacin and 0.09%-3.89% for enrofloxacin, were observed for equilibrium concentrations above the 0.3 mg/L level. The RSDs increased to 11.9% for ciprofloxacin and 32.1% for enrofloxacin at μg/L equilibrium levels, which is still acceptable. This model could be applied to predict the adsorption of other chemicals having different ionized forms.展开更多
Arsenic （As） spills and sometimes polluted water occurred more frequently sources in recent years in China. It is as urgent need to develop emergency treatment technologies to address the arsenic threat for large-sc...Arsenic （As） spills and sometimes polluted water occurred more frequently sources in recent years in China. It is as urgent need to develop emergency treatment technologies to address the arsenic threat for large-scale water treatment plants. In response, we developed a chemical sedimentation technology to remove arsenic contaminants for water treatment plants. Bench-scale experiments were conducted to investigate the efficiency of arsenic removal and the influencing factors of the chemical sedimentation treatment process. The influencing factors included the choice and dosage of coagulants, the valence of arsenic and pH value of solution. The As（V） contaminants can be almost completely removed by ferric or alum coagulants. The As（III） contaminants are more recalcitrant to chemical sedimentation, 75% for ferric coagulant and 40% for alum coagulant. The quantitative results of arsenic removal load by different ferric or alum coagulants were presented to help determine the parameters for arsenic treatment technology. The dominant mechanism for arsenic removal is static combination, or adsorption of negative arsenic species onto positive ferric hydroxide or alum hydroxide flocs. The efficiency of this treatment technology has also been demonstrated by a real production test in one water treatment plant with arsenicrich source water and one emergency response. This technology was verified to be quick to set-up, easy to operate and highly efficient even for high concentration of arsenic.展开更多
Since the ammonia in the effluent of the tradi-tional water purification process could not meet the supply demand,the advanced treatment of a high concentration of NH4+-N micro-polluted source water by biological acti...Since the ammonia in the effluent of the tradi-tional water purification process could not meet the supply demand,the advanced treatment of a high concentration of NH4+-N micro-polluted source water by biological activated carbon filter(BACF)was tested.The filter was operated in the downflow manner and the results showed that the remov-ing rate of NH_(4)^(+)-N was related to the influent concentration of NH_(4)^(+)-N.Its removing rate could be higher than 95%when influent concentration was under 1.0 mg/L.It could also decrease with the increasing influent concentration when the NH_(4)^(+)-N concentration was in the range from 1.5 to 4.9 mg/L and the dissolved oxygen(DO)in the influent was under 10 mg/L,and the minimum removing rate could be 30%.The key factor of restricting nitrification in BACF was the influent DO.When the influent NH_(4)^(+)-N concentration was high,the DO in water was almost depleted entirely by the nitrifying and hetetrophic bacteria in the depth of 0.4 m filter and the filter layer was divided into aerobic and anoxic zones.The nitrification and degradation of organic matters existed in the aerobic zone,while the denitrification occurred in the anoxic zone.Due to the limited carbon source,the denitrifica-tion could not be carried out properly,which led to the accu-mulation of the denitrification intermediates such as NO_(2)^(−).In addition to the denitrification bacteria,the nitrification and the heterotrophic bacteria existed in the anoxic zone.展开更多
基金supported by the National Natural Science Foundation of China(5137917651679201)
文摘This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact time constraints of guidance law(ITCG) is derived by using sliding mode control(SMC) and Lyapunov stability theorem. The expected impact time is realized by using the notion of attack process and estimated time-to-go to design sliding mode surface(SMS). ITCG contains equivalent and discontinuous guidance laws, once state variables arrive at SMS,the equivalent guidance law keeps the state variables on SMS,then the discontinuous guidance law enforces state variables to move and reach SMS. The singularity problem of ITCG is also analyzed. Theoretical analysis and numerical simulation results are given to test the effectiveness of ITCG designed in this paper.
文摘Recently,drug-drug cocrystal attracts more and more attention.It offers a low risk,low-cost but high reward route to new and better medicines and could improve the physiochemical and biopharmaceutical properties of a medicine by addition of a suitable therapeutically effective component without any chemical modification.Having so many advantages,to date,the reported drug-drug cocrystals are rare.Here we review the drug-drug cocrystals that reported in last decade and shed light on the opportunities and challenges for the development of drug-drug cocrystals.
文摘基于本地化差分隐私的多维分析查询(multi-dimensional analytical query,MDA)已得到了研究者的广泛关注.现有基于最优局部哈希(optimal local Hashing,OLH)机制与层次树结构的扰动方法存在泄露根结点隐私的风险.针对现有结合层次树结构的本地扰动机制不足,提出了一种有效且满足本地化差分隐私的MDA查询算法H4MDA (hierarchical structure for MDA),该算法充分利用层次树的横向与纵向结构特征设计了3种基于用户分组策略的本地扰动算法HGRR,LGRR-FD,LGRR.算法HGRR结合层次树横向结构与GRR机制本地扰动用户元组数据,通过摈弃根结点组合来响应MDA查询.不同于HGRR,LGRR-FD算法利用层次树的纵向结构与GRR机制扰动本地数据,同时通过添加假数据来避免叶子结点的隐私泄露.LGRR算法通过摈弃叶子结点层纵向扰动本地数据.收集者结合LGRR的扰动结果利用局部一致性处理技术重构层次树最后两层,通过添加虚拟叶子结点来响应MDA查询,而虚拟叶子结点计数之和等于其父节点计数.HGRR,LGRR-FD,LGRR算法与现有扰动算法在3种数据集上实验结果表明,其响应MDA查询的精度优于同类算法.
基金supported by the National Natural Science Foundation of China(Grant No.41775070).
文摘The Tibetan Plateau(TP)is a key region for environmental and climatic research due to its significant linkages with large-scale atmospheric circulation.Understanding the long-term moisture evolution pattern and its forcing mechanisms on the TP during the Holocene may provide insights into the interaction between low-latitude climate systems and midlatitude westerlies.Here,we synthesized 27 paleoclimate proxy records covering the past 9500 years.The results of the rotated empirical orthogonal function analysis of the moisture variation revealed spatial-temporal heterogeneity,which was classified into 5 subregions.Proxy records were then compared with the results from the Kiel Climate Model and other paleorecords.The results showed that moisture evolution on the western-southern-central TP was controlled by the Indian summer monsoon(ISM).On the south-eastern TP,moisture change was affected by the interplay between the East Asian summer monsoon(EASM)and the westerlies,as well as the ISM.With diverse patterns of circulation system precipitation,moisture changes recorded in the paleorecords showed spatial-temporal discrepancies,especially during the early to middle Holocene.Moreover,given the anti-phase pattern of summer precipitation in the EASM area under El Nino/Southern Oscillation(ENSO)conditions and the unstable relationship between the ISM and ENSO,it is reasonable to conclude that relatively strong ENSO variability during the late Holocene has contributed to these discrepancies as Asian summer monsoon precipitation has declined.
基金supported by the National Natural Science Foundation of China (Nos.51290284 and 21477059)the Tsinghua University Initiative Scientific Research Program (No.20131089247)
文摘A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated precursors changed greatly after the source water switching.Average concentrations of N-nitrosodimethylamine（NDMA）,N-nitrosomorpholine（NMOR）,and N-nitrosopyrrolidine（NPYR） in the finished water were6.9,3.3,and 3.1 ng/L,respectively,from June to October when the Luan River water was used as source water,while those of NDMA,N-nitrosomethylethylamine（NMEA）,and NPYR in the finished water were 10.1,4.9,and 4.7 ng/L,respectively,from November to next April when the Yellow River was used.NDMA concentration in the finished water was frequently over the 10 ng/L,i.e.,the notification level of California,USA,which indicated a considerable threat to public health.Weak correlations were observed between N-nitrosamine yield and typical water quality parameters except for the dissolved organic nitrogen.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment(No. 2009ZX07423-003)
文摘A GAC-sand dual media filter （GSF） was devised as an alternative solution for drinking water treatment plant to tackle the raw water polluted by ammonium in place of expensive ozone-GAC processes or bio-pretreatments. The ammonium removal pathways and microbial community in the GSFs were investigated. The concentrations of ammonium, nitrite and nitrate nitrogen were monitored along the filter. Total inorganic nitrogen （TIN） loss occurred during the filtration. For 1 mg ammonium removal, the TIN loss was as high as 0.35 mg, DO consumption was 3.06 mg, and alkalinity consumption was 5.55 rag. It was assumed that both nitrification and denitrification processes occur in the filters to fit the TIN loss and low DO consumption. During the filtration, nitritation, nitrification and nitritation-anaerobic ammonium oxidation processes probably occur, while traditional nitrification and denitrification and simultaneous nitrification and denitrification processes may occur. In the GSFs, Nitrosomonas and Nitrospira are likely to be involved in nitrification processes, while Novosphingobium, Comamonadaceae and Oxalobacteraceae may be involved in denitrification processes.
基金supported by the National Science Foundation Committee of China (No.21777079)the National Water Major Project (No.2017ZX07201002)+2 种基金the National Geographic Air and Water Conservation Fund (No.#GEFC-07-16)the Committee of Science and Technology Innovation of Shenzhen (No.JCYJ20170817161942307)the open project of State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University (No.19Y02ESPCT).
文摘Four sampling campaigns were conducted in two years to understand the fluctuation of N-Nitrosamines(NAs) and their precursors in one drinking water treatment plant(DWTP) in East China in different seasons.This water supply system has been facing several nitrosamine challenges related with source water, including the switch of water source,high concentration of ammonium, formed NAs and NA formation potential(FP) in source water.Besides, the use of ozonation in the DWTP and chloramination in networks will increase the NDMA concentration in tap water.To address these challenges, the biopretreatment was applied in this DWTP to decrease the concentration of ammonium and NAs.The following biological activated carbon(BAC) will neutralize the nitrosamine increase brought by ozonation.The use of free chlorine in disinfection process will also decrease the NDMA formation compared with chloramination.The results will benefit other cities in China and other countries with similar impacted water sources.
基金supported by the National Natural Science Foundation of China (No. 51290284)
文摘Powdered activated carbon（PAC） adsorption of two fishy odorants, trans,trans-2,4-heptadienal（HDE） and trans,trans-2,4-decadienal（DDE）, was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters（ΔG^0, ΔH^0, and ΔS^0） indicated an exothermic and spontaneous adsorption process. PAC dosage, p H, and natural organic matter（NOM） presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of p H had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at p H 9. The presence of NOM, especially the fraction with molecular weight less than1 k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did.
文摘A red water phenomenon occurred in several communities few days after the change of water source in Beijing, China in 2008. In this study, the origin of this problem, the mechanism of iron release and various control measures were investigated. The results indicated that a significant increase in sulphate concentration as a result of the new water source was the cause of the red water phenomenon. The mechanism of iron release was found that the high-concentration sulphate in the new water source disrupted the stable shell of scale on the inner pipe and led to the release of iron compounds. Experiments showed that the iron release rate in the new source water within pipe section was over 11-fold higher than that occurring within the local source water. The recovery of tap water quality lasted several months despite ameliora- tive measures being implemented, including adding phosphate, reducing the overall proportion of the new water source, elevating the pH and alkalinity, and utilizing free chlorine as a disinfectant instead of chloramine. Adding phosphate was more effective and more practical than the other measures. The iron release rate was decreased after the addition of 1.5 mg. L-1 orthophosphate- P, tripolyphosphate-P and hexametaphosphate-P by 68%, 83% and 87%, respectively. Elevating the pH and alkalinity also reduced the iron release rate by 50%. However, the iron release rate did not decreased after replacing chloramine by 0.5-0.8 mg. L-1 of free chlorine as disinfectant.
基金the Ministry of Construction P.R.China(Grant No.06-k4-36).
文摘An investigation into emergency potable water treatment technologies was conducted to investigate China’s water pollution situation.In order to confirm optimum parameters,the technological efficiency of each pollutant was obtained.About 100 contaminants were tested to find the emergency treatment technologies,most of which were found to be positive.This paper presents the three largest and most significant water pollution incidents in China to date,analyzing cases such as the nitrobenzene pollution incident in the Songhua River in November 2005,the cadmium pollution incident in the Beijiang River in December 2005,and the water crisis with odorous tap water in Wuxi City in May 2007.
基金supported by the National Natural Science Foundation of China(No.50708050)the National Water Special Program of China(No.2008ZX07420-005)
文摘XAD-8 resin isolation of organic matter in water was used to divide organic matter into the hydrophobic and hydrophilic fractions. A pilot plant was used to investigate the change in both fractions during conventional and advanced treatment processes. The treatment of hydrophobic organics （HPO）, rather than hydrophilic organicas （HPI）, should carry greater emphasis due to HPO’s higher trihalomethane formation potential （THMFP） and haloacetic acid formation potential （HAAFP）. The removal of hydrophobic matter and its transmission into hydrophilic matter reduced ultimate DBP yield during the disinfection process. The results showed that sand filtration, ozonation, and biological activated carbon （BAC） filtration had distinct influences on the removal of both organic fractions. Additionally, the combination of processes changed the organic fraction proportions present during treatment. The use of ozonation and BAC maximized organic matter removal efficiency, especially for the hydrophobic fraction. In sum, the combination of pre-ozonation, conventional treatment, and O 3 -BAC removed 48% of dissolved organic carbon （DOC）, 60% of HPO, 30% of HPI, 63% of THMFP, and 85% of HAAFP. The use of conventional treatment and O 3 -BAC without pre-ozonation had a comparable performance, removing 51% of DOC, 56% of HPO, 45% of HPI, 61% of THMFP, and 72% of HAAFP. The effectiveness of this analysis method indicated that resin isolation and fractionation should be standardized as an applicable test to help assess water treatment process efficiency.
文摘N-nitrosodimethylamine （NDMA） and several other N-nitrosamines have been detected as disinfection by-products in drinking waters in many countries around the world. An ultra-performance liquid chromatography- tandem mass spectrometry method with solid phase extraction sample preparation was developed to study the occurrence of N-nitrosamines in several water treatment plants and distribution systems in China. Isotope labeled N-nitrosodi-n-propylamine-dl4 （NDPA-dl4） was selected as the internal standard for quantification. The solid phase extraction procedures including pH, enrichment process and MS/MS parameters including capillary voltage, cone gas flow, cone voltage, collision energy were optimized to give average recoveries of 26% to 112% for nine N- nitrosamine species. The instrument detection limits were estimated to range from 0.5 to 5μg.L-1 for the nine N- nitrosamine species. NDMA and several other N-nitrosa- mines were found at fairly high concentrations in several water treatment plants and distribution systems. NDMA was found in all locations, and the highest concentrations in cities B, G, T, and W were 3.0, 35.7, 21.3, and 19.7 ng. L 1, respectively. A wide range of N-nitrosamines concentrations and species were observed in different locations. Higher concentrations of N-nitrosamines were detected in distribution systems that were further away from the treatment plants, suggesting that the contact time between the residual disinfectant and natural organic matter may play an important role in the formation of these compounds.
基金supported by grants from the Ministry of Science and Technology of China (Grant No. 2016YFC0900300)National Natural Science Foundation of China (Grant Nos. 31670895, U1504831, 31430022, 31670824, 31400672, and 81703598)+3 种基金Major Science and Technology Project of Henan Province (Grant No. 161100310100)Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB14030300)Foundation for University Young Key Teacher of Henan Province (Grant No. 2015GGJS-162)Science and Technology Project of Henan Province (Grant No.162102310199), China
文摘Non-small-cell lung cancer （NSCLC）, the most common type of lung cancer accounting for 85% of the cases, is often diagnosed at advanced stages owing to the lack of efficient early diagnostic tools. 5-Hydroxymetbylcytosine （ShmC） signatures in circulating cell-free DNA （cfDNA） that carries the cancer-specific epigenetic patterns may represent the valuable biomarkers for discriminat- ing tumor and healthy individuals, and thus could be potentially useful for NSCLC diagnosis. Here, we employed a sensitive and reliable method to map genome-wide 5hmC in the cfDNA of Chinese NSCLC patients and detected a significant 5hmC gain in both the gene bodies and promoter regions in the blood samples from tumor patients compared with healthy controls. Specifically, we identi- fied six potential biomarkers from 66 patients and 67 healthy controls （mean decrease accuracy 〉 3.2, P 〈 3.68E-19） using machine-learning-based tumor classifiers with high accuracy. Thus, the unique signature of 5hmC in tumor patient＇s cfDNA identified in our study may provide valuable information in facilitating the development of new diagnostic and therapeutic modalities for NSCLC.
基金supported by the National Natural Science Foundation of China (No.51078208)the Major Science and Technology Program for Water Pollution Control and Treatment(No.2008ZX07420-005,2008X07423-002)
文摘It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the development of practical treatment technologies. In this study, dissolved organic matter （DOM） from two source waters was fractionated with XAD resins and ultra- filtration membranes. The N-nitrosamine formation potential （FP） （ng of N-nitrosamines formed per mg of dissolved organic carbon （DOC）） from raw water and each fraction were measured and correlated with the fluorescence excitation-emission matrix （EEM）, molecular weight （MW） and other assays. The results showed that the hydrophilic fraction had N-nitrosamine FP 1.3 to 3.5 times higher than the hydrophobic fraction from both source waters. The DOM fraction with low MW was the dominant fraction in these two source waters and contributed more precursors for N-nitrosamine formation than the larger MW fraction. The EEM spectra indicated there were notable amounts of soluble microbial products （SMPs） and aromatic proteins in the two studied rivers, which probably originated from wastewater discharge. The SMPs tended to be more closely correlated with N-nitrosodimethylamine formation potential than the other DOM components. Higher N-nitrosamine FP were also related to fractions with lower DOC/DON ratios and lower SUVA254 values.
基金supported by the Shandong Provincial Key Research and Development Program- Major Scientific and Technological Innovation Project (No. 2020CXGC011406)the R&D project of Suzhou Water Resource and Management (No. 2020011)the National Water Major Project (Nos. 2018ZX07111-006 , 2012ZX07404-002 , 2012ZX07403-001)。
文摘The qualified finished water from water treatment plants(WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems(DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.
文摘This study focused on evaluating the efficiency of powdered activated carbon （PAC） adsorption process and tackling chlorobenzenes and chlorophenols spill in drinking water source. The adsorption kinetics and PAC＇s capacities for five chlorobenzenes and three chlorophenols at drinking water contamination levels were studied in order to determine the influence of different functional groups on the adsorption behavior. The results showed that PAC adsorption could be used as an effective emergency drinking water treatment process to remove these compounds. The adsorption kinetics took 30 min to achieve nearly equilibrium and could be described by both pseudo first-order and pseudo second-order models. A mathematic relationship was developed between the pseudo first-order adsorption rate constant, k1, and the solutes＇ properties including lgKow, polarizability and molecular weight. The Freundlich isotherm equation could well describe the adsorption equilibrium behaviors of chlorinated aromatics with r2 from 0.920 to 0.999. The H-bond donor/acceptor group, hydrophobicity, solubility and molecular volume were identified as important solute properties that affect the PAC adsorption capacity. These results could assist water professionals in removing chlorinated aromatics during emergency drinking water treatment.
基金supported by the youth fund of The First Affiliated Hospital of Zhengzhou University
文摘The aim of the research was to investigate the pharmacokinetics(PK) of enteric-coated mycophenolate sodium(EC-MPS) by quantification of the active metabolite of mycophenolic acid(MPA)after multiple escalating oral doses in Han kidney transplant recipients. A total of 28 Han postoperative kidney transplant recipients were given a multiple-dose of 540, 720 or 900 mg of EC-MPS two times a day in combination with tacrolimus for 6 days. Blood specimens were collected at each time point from0 to 12 h after EC-MPS administration. MPA plasma concentrations were measured by UPLC–UV. The relationship between the EC-MPS dose and its PK parameters was assessed. In the range from 540 to900 mg, C_(max) and AUC_(0–12h) did not increase with dose escalation. The AUC_(0–12h), C_(max), C_0 and T_(max) for the 540 720 and 900 mg doses were not significantly different, respectively(P 40.05). AUC_0–12 h and C_(max) were increased less than proportionally with increasing EC-MPS dose levels. Inter-individual variability in AUC_(0–12h), C_(max) and C_0 were considerable. Nonlinear PK relationships were found from the doses of 540–900 mg of EC-MPS.
基金supported by the National Natural Science Foundation of China(Nos.51290284,and 21477059)the Tsinghua University Initiative Scientific Research Program(No.20131089247)the National Water Major Project(No.2015ZX07 402-002)
文摘The extensive use of antibiotics has led to their presence in the aquatic environment, and introduces potential impacts on human and ecological health. The capability of powdered activated carbon （PAC） to remove six frequently used quinolone （QN） antibiotics during water treatment was evaluated to improve drinking water safety. The kinetics of QN adsorption by PAC was best described by a pseudo second-order equation, and the adsorption capacity was well described by the Freundlich isotherm equation. Isotherms measured at different pH showed that hydrophobic interaction, electrostatic interaction, and dispersion force were the main mechanisms for adsorption of QNs by PAC. A pH-dependent isotherm model based on the Freundlich equation was developed to predict the adsorption capacity of QNs by PAC at different pH values. This model had excellent prediction capabilities under different laboratory scenarios. Small relative standard derivations （RSDs）, i.e., 0.59%-0.92% for ciprofloxacin and 0.09%-3.89% for enrofloxacin, were observed for equilibrium concentrations above the 0.3 mg/L level. The RSDs increased to 11.9% for ciprofloxacin and 32.1% for enrofloxacin at μg/L equilibrium levels, which is still acceptable. This model could be applied to predict the adsorption of other chemicals having different ionized forms.
文摘Arsenic （As） spills and sometimes polluted water occurred more frequently sources in recent years in China. It is as urgent need to develop emergency treatment technologies to address the arsenic threat for large-scale water treatment plants. In response, we developed a chemical sedimentation technology to remove arsenic contaminants for water treatment plants. Bench-scale experiments were conducted to investigate the efficiency of arsenic removal and the influencing factors of the chemical sedimentation treatment process. The influencing factors included the choice and dosage of coagulants, the valence of arsenic and pH value of solution. The As（V） contaminants can be almost completely removed by ferric or alum coagulants. The As（III） contaminants are more recalcitrant to chemical sedimentation, 75% for ferric coagulant and 40% for alum coagulant. The quantitative results of arsenic removal load by different ferric or alum coagulants were presented to help determine the parameters for arsenic treatment technology. The dominant mechanism for arsenic removal is static combination, or adsorption of negative arsenic species onto positive ferric hydroxide or alum hydroxide flocs. The efficiency of this treatment technology has also been demonstrated by a real production test in one water treatment plant with arsenicrich source water and one emergency response. This technology was verified to be quick to set-up, easy to operate and highly efficient even for high concentration of arsenic.
文摘Since the ammonia in the effluent of the tradi-tional water purification process could not meet the supply demand,the advanced treatment of a high concentration of NH4+-N micro-polluted source water by biological activated carbon filter(BACF)was tested.The filter was operated in the downflow manner and the results showed that the remov-ing rate of NH_(4)^(+)-N was related to the influent concentration of NH_(4)^(+)-N.Its removing rate could be higher than 95%when influent concentration was under 1.0 mg/L.It could also decrease with the increasing influent concentration when the NH_(4)^(+)-N concentration was in the range from 1.5 to 4.9 mg/L and the dissolved oxygen(DO)in the influent was under 10 mg/L,and the minimum removing rate could be 30%.The key factor of restricting nitrification in BACF was the influent DO.When the influent NH_(4)^(+)-N concentration was high,the DO in water was almost depleted entirely by the nitrifying and hetetrophic bacteria in the depth of 0.4 m filter and the filter layer was divided into aerobic and anoxic zones.The nitrification and degradation of organic matters existed in the aerobic zone,while the denitrification occurred in the anoxic zone.Due to the limited carbon source,the denitrifica-tion could not be carried out properly,which led to the accu-mulation of the denitrification intermediates such as NO_(2)^(−).In addition to the denitrification bacteria,the nitrification and the heterotrophic bacteria existed in the anoxic zone.
