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ABSTRACT: Experiments were conducted to examine the reduction of nitroaromatic compounds (NACs) by Fe(II) associated with iron oxides (goethite, hematite and magnetite) and humic acid. The reduction rate of nitrobenzene decreased in the order of Fe(II) associated with magnetite>Fe(II) associated with goethite>Fe(II) associated with hematite. We proposed a four-step model (adsorption, electron transfer to conduction band, electron transfer to nitrobenzene and electron transfer to crystal lattice) for nitrobenzene reduction by Fe(II) associated with iron oxides. Fe(II)-humic acid complexes did not present reduction capability of nitrobenzene. Furthermore, Humic acid significantly inhibited nitrobenzene reduction by Fe(II) associated with iron oxides. The inhibitory effect of humic acid toward the reduction of nitrobenzene decreased in the order of magnetite>goethite>hematite.
Chemosphere 02/2013; · 3.21 Impact Factor
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ABSTRACT: Thermophilic co-fermentation of cassava stillage (CS) and cassava excess sludge (CES) were investigated for hydrogen and methane production. The highest hydrogen yield (37.1 ml/g-total-VS added) was obtained at VS(CS)/VS(CES) of 7:1, 17% higher than that with CS digestion alone. The CES recycle enhanced the substrate utilization and improved the buffer capacity. Further increase the CES fraction led to changed VFA distribution and more hydrogen consumption. FISH analysis revealed that both hydrogen producing bacteria and hydrogen consuming bacteria were enriched after CES recycled, and the acetobacteria percentage increased to 12.4% at VS(CS)/VS(CES) of 6:2. Relatively high efficient and stable hydrogen production was observed at VS(CS)/VS(CES) of 5:3 without pH adjusted and any pretreatment. The highest total energy yield, the highest COD and VS degradation were obtained at VS(CS)/VS(CES) of 7:1. GFC analysis indicated that the hydrolysis behavior was significantly improved by CES recycle at both hydrogen and methane production phase.
Bioresource technology 06/2012; 120:165-72. · 4.25 Impact Factor
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ABSTRACT: Perfluorinated acids (PFAs) are the subject of increasingly intense environmental research. In this study, sewage sludge samples were collected from 25 wastewater treatment plants (WWTPs) in Shanghai, China to evaluate the levels and profile of C3-C14 PFAs. The results showed a ubiquitous PFAs contamination of sewage sludge in Shanghai with the total PFAs (∑PFAs) range of 126-809 ng g(-1)dw. Perfluorooctanoic acid (PFOA) was found to be the dominant PFA pollutant and its concentration ranged from 23.2 to 298 ng g(-1)dw, much higher than the levels in other countries. Moreover, concentrations of short-chain PFAs (<C6) in sewage sludge were considerable. Following sludge application in agricultural land, the concentrations of PFOA, and perfluorooctane sulfonate (PFOS) are predicted to be 1.08 and 7.53 ng g(-1)dw, respectively, much lower than the corresponding US EPA standards. Nevertheless, further studies are needed to explore the fate of PFAs in sludge-amended soils due to the persistence and bioaccumulation potential of these compounds.
Chemosphere 04/2012; 88(11):1300-5. · 3.21 Impact Factor
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ABSTRACT: Nitrogen removal of wetlands under 40 different inflow loadings were studied in the field during 15 months. The removal efficiency
of four different sets of beds, namely the reed bed, the Zizania caduciflor bed, the mixing planting bed, and the control
bed were studied. The outflow loading and total nitrogen (TN) removal rate of these beds under different inflow loadings and
pollution loadings were investigated. The inflow loadings of 4 subsurface flow systems (SFS) ranged from 400 to 8000 mg·(m2·d)−1, while outflow loadings were less than 7000 mg·(m2·d)−1. The results showed that the inflow and outflow loading of TN removal rate in SFS presented an obvious linear relationship.
The optical inflow loading to run the system was between 2000 to 4000 mg·(m2·d)−1. Average removal rate was between 1062 and 2007 mg·(m2·d)−1. SFS with plant had a better removal rate than the control. TN removal rates of the reed and Zizania caduciflora bed were
63% and 27% higher than the control bed, respectively. The results regarding the TN absorption of plants indicated that the
absorption amount was very limited, less than 5% of the total removal. It proved that plants clearly increase TN removal rates
by improving the water flow, and increasing the biomass, as well as activities of microorganisms around the roots. The research
provided a perspective for understanding the TN removal mechanism and design for SFS.
Frontiers of Environmental Science & Engineering in China 04/2012; 2(1):89-93. · 0.75 Impact Factor
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ABSTRACT: Experiments were conducted to examine of nitrobenzene reduction by steel convert slag (SCS) with Fe(II) system. The results showed SCS with Fe(II) was an effective reductant for nitrobenzene at pH 5.5-6.5. Further analysis suggested Fe(II) was adsorbed by SCS through ion replacement with SCS-bound Ca(II). More than 81% of the total Ca(II) in SCS was replaced with dissolved Fe(II), indicating a high adsorption capacity for Fe(II) (more than 5.82 mmol Fe(II)/g SCS). A three step mechanism (replacement process, conversion process and electron transfer process) was proposed for nitrobenzene reduction by SCS with Fe(II) system. The amount of Ca(II) in SCS determined the adsorption capacity for Fe(II) and further determined the reduction capacity of SCS with Fe(II) system.
Journal of hazardous materials 03/2012; 217-218:416-21. · 4.14 Impact Factor
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Yongchang Chen,
Yuyu Niu,
Shihua Yang,
Xiechao He,
Shaohui Ji,
Wei Si,
Xianghui Tang,
Yunhua Xie,
Hong Wang,
Yongqing Lu, Qi Zhou,
Weizhi Ji
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ABSTRACT: Much effort has been focused on improving assisted reproductive technology procedures in humans and nonhuman primates (NHPs). However, the pregnancy rate after embryo transfer (ET) has not been satisfactory, indicating that some barriers still need to be overcome in this important procedure. One of the key factors is embryo–uterine synchronicity, which is little known in NHPs. The objective of this study was to investigate the available ET time window in rhesus monkey (Macaca mulatta). Eighty-two adult female rhesus monkeys were superovulated with recombinant human FSH. Ovarian phases were identified according to estrogen (E2) and progesterone (P4) levels as well as ovarian examination by ultrasonography and laparoscopy. A total of 259 embryos were transferred by the laparoscopic approach into the oviducts of 63 adult female monkeys. Ovarian phases were divided into late follicular and early luteal phases. Similar pregnancy rates (30–36.4%) were obtained from recipients receiving ET either in their late follicular or early luteal phases, regardless of embryo developmental stages. This study indicates that the available time window for ET in rhesus monkeys is from the late follicular to early luteal phases.
American Journal of Primatology 02/2012; 74(2):165-73. · 2.22 Impact Factor
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ABSTRACT: The possibility of converting hydrogen to methane and simultaneous upgrading of biogas was investigated in both batch tests and fully mixed biogas reactor, simultaneously fed with manure and hydrogen. Batch experiments showed that hydrogen could be converted to methane by hydrogenotrophic methanogenesis with conversion of more than 90% of the consumed hydrogen to methane. The hydrogen consumption rates were affected by both P(H₂) (hydrogen partial pressure) and mixing intensity. Inhibition of propionate and butyrate degradation by hydrogen (1 atm) was only observed under high mixing intensity (shaking speed 300 rpm). Continuous addition of hydrogen (flow rate of 28.6 mL/(L/h)) to an anaerobic reactor fed with manure, showed that more than 80% of the hydrogen was utilized. The propionate and butyrate level in the reactor was not significantly affected by the hydrogen addition. The methane production rate of the reactor with H₂ addition was 22% higher, compared to the control reactor only fed with manure. The CO₂ content in the produced biogas was only 15%, while it was 38% in the control reactor. However, the addition of hydrogen resulted in increase of pH (from 8.0 to 8.3) due to the consumption of bicarbonate, which subsequently caused slight inhibition of methanogenesis.
Biotechnology and Bioengineering 11/2011; 109(4):1088-94. · 3.95 Impact Factor
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ABSTRACT: Phosphate removal from polluted water is crucial to preventing eutrophication. Herein, we present the investigation on phosphate adsorption in aqueous solutions by using lanthanum-doped activated carbon fiber (ACF-La). Various batch sorption conditions, e.g., pH, ionic strength, and temperature were tested, and the adsorption mechanisms were discussed. The sorption capacity of ACF-La was higher in acidic solutions than that in basic ones, suggesting that the Lewis acid-base interaction gradually dominated the adsorption process with the increase in pH values. The degree of phosphate removal decreased with the enhancement of the ionic strength of the solution, meaning that the adsorption of phosphate on ACF-La was strongly dependent on ionic strength. Employing the pseudo first- and second-order, and intra-particle diffusion models to evaluate the adsorption kinetics of phosphate onto ACF-La indicated that the second-order model best fits the experimental data. The presence of chloride ion in solutions increased the effect of intra-particle diffusion on the adsorption of phosphate onto ACF-La but reduced the overall rate of the adsorption. The thermodynamic parameters were determined which revealed the feasibility, spontaneity, and endothermic nature of adsorption.
Journal of Colloid and Interface Science 09/2011; 364(2):490-6. · 3.07 Impact Factor
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ABSTRACT: A bipartite graph consists of a set of nodes that can be divided into two partitions such that no edge has both endpoints in the same partition. A semi-bipartite graph is a bipartite graph with edges in one partition. Anchored map is a graph drawing technique for bipartite graphs and provides aesthetically pleasing layouts of graphs with high readability by restricting the positions of nodes in a partition. For this research, the objects of the anchored map technique were extended to semi-bipartite graphs. A hybrid layout style of anchored maps and matrix representations are proposed, and an automatic drawing technique is shown. The proposed technique arranges the nodes in one partition on a circumference like the anchored map of bipartite graphs. It also divides nodes in the other partition with edges into clusters and represents them in the matrix representations to make it easy to see connective subsets.
Information Visualisation (IV), 2011 15th International Conference on; 08/2011
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ABSTRACT: In large-scale cloud computing systems, even a simple user request may go through numerous of services that are deployed on different physical machines. As a result, it is a great challenge to online localize the prime causes of performance degradation in such systems. Existing end-to-end request tracing approaches are not suitable for online anomaly detection because their time complexity is exponential in the size of the trace logs. In this paper, we propose an approach, namely Magnifier, to rapidly diagnose the source of performance degradation in large-scale non-stop cloud systems. In Magnifier, the execution path graph of a user request is modeled by a hierarchical structure including component layer, module layer and function layer, and anomalies are detected from higher layer to lower layer separately. In each layer every node is assigned a newly created identifier in addition to the global identifier of the request, which significantly decreases the size of parsing trace logs and accelerates the anomaly detection process. We conduct extensive experiments over a real-world enterprise system (the Alibaba cloud computing platform) providing services for the public. The results show that Magnifier can locate the prime causes of performance degradation more accurately and efficiently.
Services Computing (SCC), 2011 IEEE International Conference on; 08/2011
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ABSTRACT: We demonstrate AlGaN/GaN tunnel junction FETs (TJ-FET) featuring a metal-2DEG Schottky junction at the source. The TJ-FETs exhibit normally-off operation in an otherwise normally-on as-grown sample owing to a current controlling scheme different from the conventional FETs. The high 2DEG density in AlGaN/GaN heterostructure results in a thin tunnel barrier whose effective thickness is controlled by an overlaying gate electrode. A positive gate bias results in a nanometer-thick barrier with high tunneling current, while a zero gate bias leads to a thicker barrier that effectively blocks the current flow. High drive current (326 mA/mm), low off-state leakage current (10<sup>-8</sup> mA/mm) and high I<sub>ON</sub>/I<sub>OFF</sub> ratio (10<sup>10</sup>) at a drain voltage of 50 V, and high off-state breakdown voltage (557 V) are obtained on a standard GaN-on-Si platform featuring a 1.8 μm buffer.
Power Semiconductor Devices and ICs (ISPSD), 2011 IEEE 23rd International Symposium on; 06/2011
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ABSTRACT: Phosphate removal from wastewater is very important for the prevention of eutrophication. Adsorption of phosphate from water was investigated using activated carbon fiber loaded with lanthanum oxide (ACF-La) as a novel adsorbent. The effects of variables (La/ACF mass ratio, impregnation time, activation time, and activation temperature) have been studied by the single-factor method. Response surface methodology (RSM), based on three-variable-three-level Box-Behnken design (BBD), was employed to assess the individual and collective effects of the main independent parameters on the phosphate removal. The optimal conditions within the range studied for preparing ACF-La were found as follows: La/ACF mass ratio of 11.78%, activation time of 2.5h and activation temperature at 650°C, respectively. The phosphate removal using the ACF-La prepared under the optimal conditions was up to 97.6% even when the phosphate concentration in water was 30 mgP/L, indicating that ACF-La may be an effective adsorbent. The results from Fourier transform infrared (FT-IR) spectroscopy and change of pH values associated with the adsorption process revealed that the probable mechanism of phosphate ions onto ACF-La was not only ion exchange and coulomb interaction, but also a result of Lewis acid-base interaction due to La-O coordination bonding.
Journal of hazardous materials 06/2011; 190(1-3):848-55. · 4.14 Impact Factor
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ABSTRACT: Long-term effects of inoculum pretreatments (heat, acid, loading-shock) on hydrogen production from glucose under different temperatures (37 °C, 55 °C) and initial pH (7 and 5.5) were studied by repeated batch cultivations. Results obtained showed that it was necessary to investigate the long-term effect of inoculum pretreatment on hydrogen production since pretreatments may just temporarily inhibit the hydrogen consuming processes. After long-term cultivation, pretreated inocula did not enhance hydrogen production compared to untreated inocula under mesophilic conditions (initial pH 7 and pH 5.5) and thermophilic conditions (initial pH 7). However, pretreatment could inhibit lactate production and lead to higher hydrogen yield under thermophilic conditions at initial pH 5.5. The results further demonstrated that inoculum pretreatment could not permanently inhibit either methanogenesis or homoacetogenesis, and methanogenesis and homoacetogenesis could only be inhibited by proper control of fermentation pH and temperature. Methanogenic activity could be inhibited at pH lower than 6, both under mesophilic and thermophilic conditions, while homoacetogenic activity could only be inhibited under thermophilic condition at initial pH 5.5. Microbial community analysis showed that pretreatment did not affect the dominant bacteria. The dominant bacteria were Clostridium butyricum related organisms under mesophilic condition (initial pH 7 and 5.5), Thermoanaerobacterium sp. related organisms under thermophilic condition (initial pH 7), and Thermoanaerobacterium thermosaccharolyticum related organisms under thermophilic condition (initial pH 5.5). Results from this study clearly indicated that the long-term effects of inoculum pretreatments on hydrogen production, methanogenesis, homoacetogenesis and dominant bacteria were dependent on fermentation temperature and pH.
Biotechnology and Bioengineering 03/2011; 108(8):1816-27. · 3.95 Impact Factor
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ABSTRACT: Dissolved oxygen (DO) concentrations have often been shown to be important to decomposition rates of plant litter and thus may be a key factor in determining the supply of dissolved organic carbon (DOC) and carbon-dependent denitrification in wetlands. During the 2 months operation, DOC accumulation in anaerobic condition was superior to aerobic condition due to higher activities of hydrolase enzymes and lower hydrolysates converted to gaseous C. Also, much higher denitrification rates were observed in wetland when using anaerobic litter leachate as the carbon source, and the available carbon source (ACS) could be used as a good predictor of denitrification rate in wetland. According to the results of this study, extracellular enzymes activities (EEAs) in wetland would change as a short-term consequence of DO. This may alter balance of litter carbon flux and the characteristics of DOC, which may, in turn, have multiple effects on denitrification in wetlands.
Bioresource technology 02/2011; 102(3):2433-40. · 4.25 Impact Factor
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ABSTRACT: Thermophilic anaerobic hydrogen and methane production by co-digestion of cassava stillage (CS) and excess sludge (ES) was investigated in this study. The improved hydrogen and subsequent methane production were observed by co-digestion of CS with certain amount of ES in batch experiments. Compared with one phase anaerobic digestion, two phase anaerobic digestion offered an attractive alternative with more abundant biogas production and energy yield, e.g., the total energy yield in two phase obtained at VS(CS)/VS(ES) of 3:1 was 25% higher than the value of one phase. Results from continuous experiments further demonstrated that VS(CS)/VS(ES) of 3:1 was optimal for hydrogen production with the highest hydrogen yield of 74 mL/gtotal VS added, the balanced nutrient condition with C/N ratio of 1.5 g carbohydrate-COD/gprotein-COD or 11.9 g C/gN might be the main reason for such enhancement. VS(CS)/VS(ES) of 3:1 was also optimal for continuous methane production considering the higher methane yield of 350 mL/gtotal VS added and the lower propionate concentration in the effluent.
Bioresource technology 02/2011; 102(4):3833-9. · 4.25 Impact Factor
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ABSTRACT: The present study investigated a two-stage anaerobic hydrogen and methane process for increasing bioenergy production from organic wastes. A two-stage process with hydraulic retention time (HRT) 3d for hydrogen reactor and 12d for methane reactor, obtained 11% higher energy compared to a single-stage methanogenic process (HRT 15 d) under organic loading rate (OLR) 3 gVS/(L d). The two-stage process was still stable when the OLR was increased to 4.5 gVS/(Ld), while the single-stage process failed. The study further revealed that by changing the HRT(hydrogen):HRT(methane) ratio of the two-stage process from 3:12 to 1:14, 6.7%, more energy could be obtained. Microbial community analysis indicated that the dominant bacterial species were different in the hydrogen reactors (Thermoanaerobacterium thermosaccharolyticum-like species) and methane reactors (Clostridium thermocellum-like species). The changes of substrates and HRT did not change the dominant species. The archaeal community structures in methane reactors were similar both in single- and two- stage reactors, with acetoclastic methanogens Methanosarcina acetivorans-like organisms as the dominant species.
Bioresource technology 02/2011; 102(18):8700-6. · 4.25 Impact Factor
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ABSTRACT: Exploration of biodemulsifiers has become a new research aspect. Using waste frying oils (WFOs) as carbon source to synthesize biodemulsifiers has a potential prospect to decrease production cost and to improve the application of biodemulsifiers in the oilfield. In this study, a demulsifying strain, Alcaligenes sp. S-XJ-1, was investigated to synthesize a biodemulsifier using waste frying oils as carbon source. It was found that the increase of initial pH of culture medium could increase the biodemulsifier yield but decrease the demulsification ratio compared to that using paraffin as carbon source. In addition, a biodemulsifier produced by waste frying oils and paraffin as mixed carbon source had a lower demulsification capability compared with that produced by paraffin or waste frying oil as sole carbon source. Fed-batch fermentation of biodemulsifier using waste frying oils as supplementary carbon source was found to be a suitable method. Mechanism of waste frying oils utilization was studied by using tripalmitin, olein and tristearin as sole carbon sources to synthesize biodemulsifier. The results showed saturated long-chain fatty acid was difficult for S-XJ-1 to utilize but could effectively enhance the demulsification ability of the produced biodemulsifier. Moreover, FT-IR result showed that the demulsification capability of biodemulsifiers was associated with the content of C=O group and nitrogen element.
Journal of Environmental Sciences 01/2011; 23(6):1020-6. · 1.66 Impact Factor
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ABSTRACT: Most of the studies on sewage sludge treatment in literature were conducted for methane generation under acidic or near neutral pH conditions. It was reported in our previous studies that the accumulation of short-chain fatty acids (SCFAs), the preferred carbon source of biological wastewater nutrient removal, was significantly enhanced when sludge was fermented under alkaline conditions, but the optimal pH was temperature-dependent (pH 10 at ambient temperature, pH 9 at mesophilic, and pH 8 at thermophilic), and the maximal SCFAs yields were in the following order: thermophilic pH 8 > mesophilic pH 9 > ambient pH 10 > ambient uncontrolled pH. In this study the kinetic and microbiological features of waste activated sludge fermented in the range of pH 7-10 were investigated to understand the mechanism of remarkably high SCFAs accumulation under alkaline conditions. The developed sludge alkaline fermentation model could be applied to predicate the experimental data in either batch or semicontinuous sludge alkaline fermentation tests, and the relationships among alkaline pH, kinetic parameters, and SCFAs were discussed. Further analyses with fluorescence in situ hybridization (FISH) and PCR-based 16S rRNA gene clone library indicated that both the ratio of bacteria to archaea and the fraction of SCFAs producer accounting for bacteria were in the sequence of thermophilic pH 8 > mesophilic pH 9 > ambient pH 10 > ambient uncontrolled pH, which was in correspondence with the observed order of maximal SCFAs yields.
Environmental Science & Technology 12/2010; 44(24):9343-8. · 4.80 Impact Factor
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ABSTRACT: A biodemulsifier-producing strain of Alcaligenes sp. S-XJ-1, isolated from petroleum-contaminated soil of the Karamay Oilfield, exhibited excellent demulsifying ability. The application of this biodemulsifier significantly improved the quality of separated water compared with the chemical demulsifier, polyether, which clearly indicates that it has potential applications in the crude oil extraction industry. To optimize its biosynthesis, the impacts of carbon sources, nitrogen sources and pH were studied in detail. Paraffin, a hydrophobic carbon source, favored the synthesis of this cell wall associated biodemulsifier. The nitrogen source ammonium citrate stimulated the production and demulsifying performance of the biodemulsifier. An alkaline environment (pH 9.5) of the initial culture medium favored the strain's growth and improved its demulsifying ability. The results showed paraffin, ammonium citrate and pH had significant effects on the production of the biodemulsifier. These three variables were further investigated using a response surface methodology based on a central composite design to optimize the biodemulsifier yield. The optimal yield conditions were found at a paraffin concentration of 4.01%, an ammonium citrate concentration of 8.08 g/L and a pH of 9.35. Under optimal conditions, the biodemulsifier yield from Alcaligenes sp. S-XJ-1 was increased to 3.42 g/L.
Journal of hazardous materials 11/2010; 183(1-3):466-73. · 4.14 Impact Factor
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ABSTRACT: A demulsifying strain (S-XJ-1) was isolated from petroleum-polluted soil and identified as Alcaligenes sp. It showed emulsion breaking ratio of 81.3% for W/O emulsion within 24h when the cell concentration was 500mg/L. Evolution of water droplets during the biological demulsification process was investigated using a Turbiscan stability analyzer and microphotography. Further investigation focused on cell surface hydrophobicity and oil-water interfacial properties. The biological demulsification process began with rapid dispersal of the cells into the oil phase and adsorption onto the oil-water interface. This occurred due to high cell surface hydrophobicity and the presence of amphiphilic compounds in the cell walls. The cells had higher interfacial activity than the emulsifier molecules, and they displaced some of the emulsifier molecules, which effectively reduced the interfacial tension gradient. As a result, the interfacial film strength decreased, the water droplets coalesced and eventually phase separation occurred.
Bioresource technology 11/2010; 101(21):8315-22. · 4.25 Impact Factor
