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Search Results: 1 - 10 of 17160 matches for " Tan Q "
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An analysis of atmospheric CH4 concentrations from 1984 to 2008 with a single box atmospheric chemistry model
Z. Tan,Q. Zhuang
Atmospheric Chemistry and Physics Discussions , 2012, DOI: 10.5194/acpd-12-30259-2012
Abstract: We present a single box atmospheric chemistry model involving atmospheric methane (CH4), carbon monoxide (CO) and radical hydroxyl (OH) to analyze atmospheric CH4 concentrations from 1984 to 2008. When OH is allowed to vary, the modeled CH4 is 20 ppb higher than observations from the NOAA/ESRL and AGAGE networks for the end of 2008. However, when the OH concentration is held constant at 106 molecule cm 3, the simulated CH4 shows a trend approximately equal to observations. Both simulations show a clear slowdown in the CH4 growth rate during recent decades, from about 13 ppb yr 1 in 1984 to less than 5 ppb yr 1 in 2003. Furthermore, if the constant OH assumption is credible, we think that this slowdown is mainly due to a pause in the growth of wetland methane emissions. In simulations run for the Northern and Southern Hemispheres separately, we find that the Northern Hemisphere is more sensitive to wetland emissions, whereas the southern tends to be more perturbed by CH4 transportation, dramatic OH change, and biomass burning. When measured CO values from NOAA/ESRL are used to drive the model, changes in the CH4 growth rate become more consistent with observations, but the long-term increase in CH4 is underestimated. This shows that CO is a good indicator of short-term variations in oxidizing power in the atmosphere. The simulation results also indicate the significant drop in OH concentrations in 1998 (about 5% lower than the previous year) was probably due to an abrupt increase in wetland methane emissions during an intense EI Ni o event. Using a fixed-lag Kalman smoother, we estimate the mean wetland methane flux is about 128 Tg yr 1 through the period 1984–2008. This study demonstrates the effectiveness in examining the role of OH and CO in affecting CH4.
Kinetic analysis of nitric oxide reduction using biogas as reburning fuel
X Wang, Q Zhao, H Tan, T Xu, S Hui
African Journal of Biotechnology , 2009,
Abstract: Biogas was suggested more suitable as reburning fuel to reduce NO emission and Miller-Bowan’s mechanism was performed to analyze the effect of reaction environment in the process of biogas reburning. Results show that the NO reduction efficiency increased with the increase of hydrocarbon in biogas, reburning fuel ratio, initial NO concentration and residence time. When initial NO concentration reached 700 l/l or residence time reaches 2 s, the dependence on initial NO concentration weakened greatly. NO reduction reached maximum at 1200 – 1400 K and enhanced abruptly at the stoichiometric ratio of 0.85 with the decrease of stoichiometirc ratio. The investigations indicated the optimal biogas reburnning technology potential to reduce NO pollution.
Preparation and evaluation of quercetin-loaded lecithin-chitosan nanoparticles for topical delivery
Tan Q, Liu WD, Guo CY, Zhai GX
International Journal of Nanomedicine , 2011, DOI: http://dx.doi.org/10.2147/IJN.S22411
Abstract: eparation and evaluation of quercetin-loaded lecithin-chitosan nanoparticles for topical delivery Original Research (5672) Total Article Views Authors: Tan Q, Liu WD, Guo CY, Zhai GX Published Date August 2011 Volume 2011:6 Pages 1621 - 1630 DOI: http://dx.doi.org/10.2147/IJN.S22411 Qi Tan1, Weidong Liu1,2, Chenyu Guo1, Guangxi Zhai1 1Department of Pharmaceutics, College of Pharmacy, Shandong University, Jinan; 2Department of Pharmacy, Linyi People's Hospital Affiliated to Shandong University, Linyi, People's Republic of China Background: The purpose of this study was to investigate lecithin-chitosan nanoparticles as a topical delivery system for quercetin. Methods: Tocopheryl propylene glycol succinate was chosen to be the surfactant for the nanosystem. The mean particle size of the nanoparticles was 95.3 nm, and the entrapment efficiency and drug loading for quercetin were 48.5% and 2.45%, respectively. Topical delivery in vitro and in vivo of the quercetin-loaded nanoparticles was evaluated using quercetin propylene glycol solution as the control. Results: Compared with quercetin solution, the quercetin-loaded nanoparticles showed higher permeation ability, and significantly increased accumulation of quercetin in the skin, especially in the epidermis. Microstructure observation of the skin surface after administration indicated that the interaction between ingredients of the nanoparticles and the skin surface markedly changed the morphology of the stratum corneum and disrupted the corneocyte layers, thus facilitating the permeation and accumulation of quercetin in skin. Conclusion: Lecithin-chitosan nanoparticles are a promising carrier for topical delivery of quercetin.
Nanosized sustained-release pyridostigmine bromide microcapsules: process optimization and evaluation of characteristics
Tan Q,Jiang R,Xu M,Liu G
International Journal of Nanomedicine , 2013,
Abstract: Qunyou Tan,1,* Rong Jiang,3,* Meiling Xu,2,4,* Guodong Liu,5,* Songlin Li,1 Jingqing Zhang21Department of Thoracic Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, 2Medicine Engineering Research Center, Chongqing Medical University, 3Stem Cells and Tissue Engineering Research, Chongqing Medical University, 4Department of Pharmacy, Chongqing Emergency Medical Center, 5Eighth Department, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, People’s Republic of China*These authors contributed equally to this workBackground: Pyridostigmine bromide (3-[[(dimethylamino)-carbonyl]oxy]-1-methylpyridinium bromide), a reversible inhibitor of cholinesterase, is given orally in tablet form, and a treatment schedule of multiple daily doses is recommended for adult patients. Nanotechnology was used in this study to develop an alternative sustained-release delivery system for pyridostigmine, a synthetic drug with high solubility and poor oral bioavailability, hence a Class III drug according to the Biopharmaceutics Classification System. Novel nanosized pyridostigmine-poly(lactic acid) microcapsules (PPNMCs) were expected to have a longer duration of action than free pyridostigmine and previously reported sustained-release formulations of pyridostigmine.Methods: The PPNMCs were prepared using a double emulsion-solvent evaporation method to achieve sustained-release characteristics for pyridostigmine. The preparation process for the PPNMCs was optimized by single-factor experiments. The size distribution, zeta potential, and sustained-release behavior were evaluated in different types of release medium.Results: The optimal volume ratio of inner phase to external phase, poly(lactic acid) concentration, polyvinyl alcohol concentration, and amount of pyridostigmine were 1:10, 6%, 3% and 40 mg, respectively. The negatively charged PPNMCs had an average particle size of 937.9 nm. Compared with free pyridostigmine, PPNMCs showed an initial burst release and a subsequent very slow release in vitro. The release profiles for the PPNMCs in four different types of dissolution medium were fitted to the Ritger-Peppas and Weibull models. The similarity between pairs of dissolution profiles for the PPNMCs in different types of medium was statistically significant, and the difference between the release curves for PPNMCs and free pyridostigmine was also statistically significant.Conclusion: PPNMCs prepared by the optimized protocol described here were in the nanometer range and had good uniformity, wit
Characterization, activity, and computer modeling of a molecular inclusion complex containing rifaldazine
Tan Q,He D,Wu M,Yang L
International Journal of Nanomedicine , 2013,
Abstract: Qunyou Tan,1,* Dan He,2,* Mingjun Wu,2,* Lin Yang,3 Yong Ren,4 Juan Liu,2 Jingqing Zhang,21Department of Thoracic Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, 2Medicine Engineering Research Center, Chongqing Medical University, Chongqing, 3Chongqing Institute for Food and Drug Control, Chongqing, 4Center of Drug Discovery, Nanjing Normal University, Nanjing, People's Republic of China*These authors contributed equally to this workBackground: The purpose of this study was to develop, characterize, and investigate a molecular inclusion complex containing rifaldazine with good solubility and antibacterial activity.Methods: Rifaldazine, a lipophilic molecule, was encapsulated into the hydrophobic cavity of -cyclodextrin to form a molecular inclusion complex (RAABCD) with good solubility. RAABCD was prepared in a short time using a solid-state grinding method. The inclusion ratio, binding constant, and change in Gibbs free energy were determined by a phase solubility diagram and/or ultraviolet-visible spectroscopy. Differential scanning calorimetry and Fourier transform infrared spectroscopy of RAABCD were performed. Morphological features of RAABCD were observed by photomicroscopy. The most likely optimal configuration for RAABCD was simulated by computer modeling. Broth macrodilution testing was done to investigate the antibacterial activity of RAABCD.Results: The inclusion ratio, binding constant, and change in Gibbs free energy, determined by a phase solubility diagram and/or ultraviolet-visible spectroscopy were 1:1, 288.33/261.33 L/mol, and 32.29/31.73 kJ/mol, respectively. Differential scanning calorimetry and Fourier transformed infrared spectra of RAABCD confirmed the molecular interaction between rifaldazine and -cyclodextrin. The morphological difference between irregular and amorphous-shaped RAABCD and columnar-shaped rifaldazine further confirmed the molecular encapsulation of rifaldazine. The most likely optimal configuration for RAABCD was confirmed by computer modeling. Broth macrodilution testing indicated that RAABCD had good antibacterial activity.Conclusion: RAABCD had improved solubility and good activity, and might be a promising alternative for treatment of a range of bacterial infections.Keywords: rifaldazine, cyclodextrin inclusion complex, stoichiometric relationships, differential scanning calorimetry, Fourier transform infrared spectra, computer modeling
Controlled release of chitosan/heparin nanoparticle-delivered VEGF enhances regeneration of decellularized tissue-engineered scaffolds
Tan Q,Tang H,Hu J,Hu Y
International Journal of Nanomedicine , 2011,
Abstract: Qi Tan, Hao Tang, Jianguo Hu, Yerong Hu, Xinmin Zhou, Yunming Tao, Zhongshi WuDepartment of Cardiothoracic Surgery Second Xiangya Hospital, Central South University, Changsha 410011, People's Republic of ChinaAbstract: Regeneration deficiency is one of the main obstacles limiting the effectiveness of tissue-engineered scaffolds. To develop scaffolds that are capable of accelerating regeneration, we created a heparin/chitosan nanoparticle-immobilized decellularized bovine jugular vein scaffold to increase the loading capacity and allow for controlled release of vascular endothelial growth factor (VEGF). The vascularization of the scaffold was evaluated in vitro and in vivo. The functional nanoparticles were prepared by physical self-assembly with a diameter of 67–132 nm, positive charge, and a zeta potential of ~30 mV and then the nanoparticles were successfully immobilized to the nanofibers of scaffolds by ethylcarbodiimide hydrochloride/hydroxysulfosuccinimide modification. The scaffolds immobilized with heparin/chitosan nanoparticles exhibited highly effective localization and sustained release of VEGF for several weeks in vitro. This modified scaffold significantly stimulated endothelial cells' proliferation in vitro. Importantly, utilization of heparin/chitosan nanoparticles to localize VEGF significantly increased fibroblast infiltration, extracellular matrix production, and accelerated vascularization in mouse subcutaneous implantation model in vivo. This study provided a novel and promising system for accelerated regeneration of tissue-engineering scaffolds.Keywords: nanoparticle, scaffolds, VEGF, control release, vascularization, regeneration
Preparation and evaluation of quercetin-loaded lecithin-chitosan nanoparticles for topical delivery
Tan Q,Liu WD,Guo CY,Zhai GX
International Journal of Nanomedicine , 2011,
Abstract: Qi Tan1, Weidong Liu1,2, Chenyu Guo1, Guangxi Zhai11Department of Pharmaceutics, College of Pharmacy, Shandong University, Jinan; 2Department of Pharmacy, Linyi People's Hospital Affiliated to Shandong University, Linyi, People's Republic of ChinaBackground: The purpose of this study was to investigate lecithin-chitosan nanoparticles as a topical delivery system for quercetin.Methods: Tocopheryl propylene glycol succinate was chosen to be the surfactant for the nanosystem. The mean particle size of the nanoparticles was 95.3 nm, and the entrapment efficiency and drug loading for quercetin were 48.5% and 2.45%, respectively. Topical delivery in vitro and in vivo of the quercetin-loaded nanoparticles was evaluated using quercetin propylene glycol solution as the control.Results: Compared with quercetin solution, the quercetin-loaded nanoparticles showed higher permeation ability, and significantly increased accumulation of quercetin in the skin, especially in the epidermis. Microstructure observation of the skin surface after administration indicated that the interaction between ingredients of the nanoparticles and the skin surface markedly changed the morphology of the stratum corneum and disrupted the corneocyte layers, thus facilitating the permeation and accumulation of quercetin in skin.Conclusion: Lecithin-chitosan nanoparticles are a promising carrier for topical delivery of quercetin.Keywords: quercetin, tocopheryl polyethylene glycol succinate, lecithin, chitosan, nanoparticles, topical delivery
EPR spectrum via entangled states for an Exchange-Coupled Dimer of Single-Molecule Magnets
Xu Chang-Tan,Liang J-Q
Physics , 2006, DOI: 10.1140/epjb/e2005-00146-y
Abstract: Multi-high-frequency electron paramagnetic resonance(EPR) spectrum for a supermolecular dimer $[ Mn_4]_2$ of single-molecule magnets recently reported [S. Hill, R. S. Edwards, N. Aliaga-Alcalde and G. Christou(HEAC), Science 302, 1015 (2003)] is studied in terms of the perturbation method in which the high-order corrections to the level splittings of degenerate states are included. It is shown that the corresponding eigenvectors are composed of entangled states of two molecules. The EPR-peak positions are calculated in terms of the eigenstates at various frequencies. From the best fit of theoretical level splittings with the measured values we obtain the anisotropy constant and exchange coupling which are in agreement with the corresponding values of experimental observation. Our study confirms the prediction of HEAC that the two $Mn_4$ units within the dimer are coupled quantum mechanically by the antiferromagnetic exchange interaction and the supermolecular dimer behaviors in analogy with artificially fabricated quantum dots.
Optimal Charging of Electric Vehicles in Smart Grid: Characterization and Valley-Filling Algorithms
Niangjun Chen,Chee Wei Tan,Tony Q. S. Quek
Computer Science , 2012,
Abstract: Electric vehicles (EVs) offer an attractive long-term solution to reduce the dependence on fossil fuel and greenhouse gas emission. However, a fleet of EVs with different EV battery charging rate constraints, that is distributed across a smart power grid network requires a coordinated charging schedule to minimize the power generation and EV charging costs. In this paper, we study a joint optimal power flow (OPF) and EV charging problem that augments the OPF problem with charging EVs over time. While the OPF problem is generally nonconvex and nonsmooth, it is shown recently that the OPF problem can be solved optimally for most practical power networks using its convex dual problem. Building on this zero duality gap result, we study a nested optimization approach to decompose the joint OPF and EV charging problem. We characterize the optimal offline EV charging schedule to be a valley-filling profile, which allows us to develop an optimal offline algorithm with computational complexity that is significantly lower than centralized interior point solvers. Furthermore, we propose a decentralized online algorithm that dynamically tracks the valley-filling profile. Our algorithms are evaluated on the IEEE 14 bus system, and the simulations show that the online algorithm performs almost near optimality ($<1%$ relative difference from the offline optimal solution) under different settings.
Al doped graphene: A promising material for hydrogen storage at room temperature
Z. M. Ao,Q. Jiang,R. Q. Zhang,T. T. Tan,S. Li
Physics , 2008, DOI: 10.1063/1.3103327
Abstract: A promising material for hydrogen storage at room temperature-Al doped graphene was proposed theoretically by using density functional theory calculation. Hydrogen storage capacity of 5.13 wt% was predicted at T = 300 K and P = 0.1 Gpa with adsorption energy Eb = -0.260 eV/H2. This is close to the target of 6 wt% and satisfies the requirement of immobilization hydrogen with Eb of -0.2 ~ -0.4 eV/H2 at ambient temperature and modest pressure for commercial applications specified by U.S. Department of Energy. It is believed that the doped Al varies the electronic structures of both C and H2. The bands of H2 overlapping with those of Al and C synchronously are the underlying mechanism of hydrogen storage capacity enhancement.
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