Biomedical subjects

Tao Fang

Publications and source records attributed to Tao Fang.

16 recordsLinked to original sources

PubMed2006

A fragment energy assembler method for Hartree-Fock calculations of large molecules.

We present a fragment energy assembler approach for approximate Hartree-Fock (HF) calculations of macromolecules. In this method, a macromolecule is divided into small fragments with appropriate size, and then each fragment is capped by its neighboring fragments to form a subsystem. The total energy of the target system is evaluated as the sum of the fragment energies of all fragments, which are available from conventional HF calculations on all subsystems. By applying the method to a broad range of molecules, we demonstrate that the present approach could yield satisfactory HF energies for all studied systems.

Journal Article↗

PubMed2006

Structurally well-defined, recoverable C3-symmetric tris(beta-hydroxy phosphoramide)-catalyzed enantioselective borane reduction of ketones.

[reaction: see text] A series of new chiral C(3)-symmetric tris(beta-hydroxy phosphoramide) ligands have been synthesized via the reaction of trisphosphoramide ester and Grignard reagents. The catalytic asymmetric borane reduction of ketones with these new C(3)-symmetric chiral tris(beta-hydroxy phosphoramide)s was investigated. Structurally well-defined, recoverable ligand 1d is an efficient catalyst for the enantioselective borane reduction of both electron-deficient and electron-rich ketones, and high enantioselectivities were achieved (up to 98% ee).

Journal Article↗

PubMed2006

Degradation of 17alpha-ethinylestradiol in aqueous solution by ozonation.

This study investigates the ozonation of 17alpha-ethinylestradiol (EE(2)) in aqueous solution. The affecting factors on the degradation of EE(2) were studied and described in details, such as initial EE(2) concentration, initial pH value and ozone concentration. In addition, some parameters such as pH, electrical conductivity, mineralization efficiency and degradation products were monitored during the process. The mineralization efficiency of EE(2) could reach 53.9%. During the ozonation process the rapid decrease of pH and the sharp increase of electrical conductivity indicated the formation of acidic by-products, small fragments and ions which were confirmed by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC/MS) analysis. Results showed that there were intermediate products of smaller molecule with higher polarity produced during the course of EE(2) degradation. Then a possible reaction pathway for EE(2) degradation involving all intermediates detected is proposed. During the ozonation process EE(2) was first oxidized into hydroxyl-semiquinone isomers which were subsequently degraded into low molecular weight compounds such as oxalic acid, malonate, glutarate, and so on. Furthermore, these organic acids are easily oxidized by ozone into carbon dioxide (CO(2)). This work shows that ozonation process is promising for the removal of EE(2). The results can provide some useful information for the potential treatment of EE(2) by ozonation in aqueous solution.

Chromatography, High Pressure Liquid↗

PubMed2006

GOP-based channel rate allocation using genetic algorithm for scalable video streaming over error-prone networks.

In this paper, we address the problem of unequal error protection (UEP) for scalable video transmission over wireless packet-erasure channel. Unequal amounts of protection are allocated to the different frames (I- or P-frame) of a group-of-pictures (GOP), and in each frame, unequal amounts of protection are allocated to the progressive bit-stream of scalable video to provide a graceful degradation of video quality as packet loss rate varies. We use a genetic algorithm (GA) to quickly get the allocation pattern, which is hard to get with other conventional methods, like hill-climbing method. Theoretical analysis and experimental results both demonstrate the advantage of the proposed algorithm.

Algorithms↗

PubMed2006

[Vertical distribution of species of nitrogen and phosphorus in the sediments of Lake Donghu].

Vertical distributions of species of nitrogen and phosphorus in the sediments of three sampling sites in Lake Donghu were examined and analyzed. pH was combined to be studied at the same time. The results showed that the pH values in sediments were lower than those in overlying water and decreased with depth. The highest concentration of TN and TP occurred in Station 1, where suffered from heavy domestic sewerage. The lowest concentration of TP and TN presented to Station 2, which is located at the center of Lake Donghu. The concentrations of dissolved ammoniac nitrogen (DAN) and dissolved nitrate nitrogen (DNN) of station 1 were higher than the other stations. In recent years, along with the pollution treatment measures, the concentration of TN and TP in station 1 presented a trend of decline. However, the concentration of TN and TP ascends very fast in station 3 and it has been as high as station 1 on the surface sediments. Although phosphorus is the most restricting nutritious element all the same, the concentration of TN descended greatly in the last two decades because of the combined effect of nitrification, denitrification and phosphorus removing bacteria. As a result, the N/P ratio is only about 3.

China↗

PubMed2006

[Profiles of sediment porewater nutrient concentrations on tidal flat of turbidity maximum zone in Changjiang (Yangtze River) estuary].

Profiles of nutrients (i.e., NH4+, NO2-, NO3-, PO4(3-), and SiO3(2-)) in porewater of sediment were investigated monthly in the intertidal flat of Chongming Dongtan in Changjiang (Yangtze River) estuary during March 2005 to February 2006. The results indicate that concentrations of NH4+ and SiO3(2-) in porewater are always in the range of 200 micromol/L to 500 micromol/L and show different patterns of distribution profile among high, middle, and low marshes. Compared to high and middle marsh, low marsh, without vegetation coverage and of coarser grain size, generally contains higher NH4+ and lower SiO3(21) concentrations. SiO3(2-) concentrations are predominantly determined by seasonal temperature change, but variations of NH4+ are more complicated and prone to exhibit lower values in spring and summer when the vegetation above show relatively high growth rate. Concentrations of NO2- + NO3- and PO4(3-) in porewater are commonly much lower than NH4+ and SiO3(2-) by 2 to 3 orders of magnitude, however, due to factors such as bioturbation, the concentrations in top sediment may be higher than 10 micromol/L. The relatively high NO3- concentration in top sediment,together with the rapid transfer from oxygenic to anoxic environment, make it possible that significant denitrification happens, which may draw its remarkable influence on the biogeochemical cycles of nutrient elements in the land-sea interaction area in Changjiang (Yangtze River) estuary.

China↗

PubMed2005

Synthesis of C3-symmetric tris(beta-hydroxy amide) ligands and their Ti(IV) complex-catalyzed enantioselective alkynylation of aldehydes.

[reaction: see text]. A series of new chiral C3-symmetric tris(beta-hydroxy amide) ligands have been synthesized via the reaction of 1,3,5-benzenetricarboxylic chloride and optically pure amino alcohols (up to 96% yield). The asymmetric catalytic alkynylation of aldehydes with these new C3-symmetric chiral tris(beta-hydroxy amide) ligands and Ti (O(i)'Pr)4 was investigated. Ligand 4c synthesized from (1R,2S)-(-)-2-amino-1,2-diphenylethanol is effective for the enantioselective alkynylation of various aldehydes, and high enantioselectivity was obtained with aromatic aldehydes and alpha,beta-unsaturated aldehyde (up to 92% ee).

Journal Article↗

PubMed2005

An efficient fragment-based approach for predicting the ground-state energies and structures of large molecules.

An efficient fragment-based approach for predicting the ground-state energies and structures of large molecules at the Hartree-Fock (HF) and post-HF levels is described. The physical foundation of this approach is attributed to the "quantum locality" of the electron correlation energy and the HF total energy, which is revealed by a new energy decomposition analysis of the HF total energy proposed in this work. This approach is based on the molecular fractionation with conjugated caps (MFCC) scheme (Zhang, D. W.; Zhang, J. Z. H. J. Chem. Phys. 2003, 119, 3599), by which a macromolecule is partitioned into various capped fragments and conjugated caps formed by two adjacent caps. We find that the MFCC scheme, if corrected by the interaction between non-neighboring fragments, can be used to predict the total energy of large molecules only from energy calculations on a series of small subsystems. The approach, named as energy-corrected MFCC (EC-MFCC), computationally achieves linear scaling with the molecular size. Our test calculations on a broad range of medium- and large molecules demonstrate that this approach is able to reproduce the conventional HF and second-order Moller-Plesset perturbation theory (MP2) energies within a few millihartree in most cases. With the EC-MFCC optimization algorithm described in this work, we have obtained the optimized structures of long oligomers of trans-polyacetylene and BN nanotubes with up to about 400 atoms, which are beyond the reach of traditional computational methods. In addition, the EC-MFCC approach is also applied to estimate the heats of formation for a series of organic compounds. This approach provides an appealing approach alternative to the traditional additivity rules based on either bond or group contributions for the estimation of thermochemical properties.

Gramicidin↗

PubMed2005

Asymmetric Henry reaction catalyzed by C2-symmetric tridentate bis(oxazoline) and bis(thiazoline) complexes: metal-controlled reversal of enantioselectivity.

[reaction: see text] C(2)-symmetric tridentate bis(oxazoline) and bis(thiazoline) ligands with a diphenylamine backbone have been investigated in the catalytic asymmetric Henry reaction of alpha-keto esters with different Lewis acids. Their Cu(OTf)(2) complexes furnished S enantiomers, while Et(2)Zn complexes afforded R enantiomers, both of them with higher enantioselectivities (up to 85% ee). Reversal of enantioselectivity in asymmetric Henry reactions was achieved with the same chiral ligand by changing the Lewis acid center from Cu(II) to Zn(II). The results show that the NH group in C(2)-symmetric tridentate chiral ligands plays a very important role in controlling both the yields and enantiofacial selectivity of the Henry products.

Journal Article↗

PubMed2005

Kinetics of the oxidation of MCRR by potassium permanganate.

The occurrence of the microcystins in the water bodies, especially in drinking water resources, has received considerable attentions. In situ chemical oxidation is a promising cost-effective treatment method to remove MC from water body. This research investigated the reaction kinetics of the oxidation of MCRR by permanganate. Experimental results indicate that the reaction is second order overall and first order with respect to both permanganate and MCRR, and has an activation energy of 18.9 kJ/mol. The second-order rate constant ranges from 0.154 to 0.225 l/mg/min at temperature from 15 to 30 degrees C. The MCRR degradation rates can be accelerated through increasing reaction temperature and oxidant concentration. The reaction under acid conditions was slightly faster than under alkaline conditions. The half-life of the reaction was less than 1min, and more than 99.5% of MCRR was degraded within 10min.

Cyanobacteria↗

PubMed2005

[Spectral similarity measure and retrieval based on the complete spectral reflectance and absorption feature--nonlinear spectral angle mapper].

A novel method for spectral similarity measure, which is called nonlinear spectral angle mapper, is presented. In this method, on one hand, nonlinear transformation and removing high relativity among bands are used through kernel PCA; on the other hand, the feature of both spectral reflection and absorption are combined in transformed space. At last, spectral angle mapper is used to measure spectral similarity. The authors' experiments show that this method is effective in spectral similarity retrieval.

Absorption↗

PubMed2005

[Method of algae-bacterium biofilm to improve the water quality in eutrophic waters].

The quality of eutrophic waters was improved by the algae-bacterium biofilm, which covered over the artificial aquatic mat made from a kind of mend macromolecule material. Two series of experiments show that using the artificial aquatic mat technique, algae bloom was inhibited markedly. At the eleventh day, the transparency was increased from 6 cm to 62 cm; and the concentrations of COD(Mn), TP, TN and NH4(+) -N were decreased to 92.89%, 49.25% , 94.97% and 70.15% respectively. The DO concentration also kept in certain satisfied level for using the algae-bacterium biofilm method. The suitable and economical density was about 8 - 16 bunchs/m(2) when the ratio of the artificial aquatic mat length to water depth was 0.7.

Bacteria↗

PubMed2005

[Spectral feature-based hyperspectral RS image retrieval].

Oriented to the demands of vast RS information management for RS image retrieval, the applications of spectral features are discussed by taking hyperspectral RS image as an example. It is proposed that spectral features-based retrieval includes two modes: retrieval based on point mask an dpolygon mask. The most key issues in retrieval are spectral features extraction andsimilarity measure. The spectral vector can be used to retrieval directly, and the spectral angle and spectral information divergence (SID) are effective in similarity measure. The local maximum and minimum in reflectance spectral curve, corresponding to reflectance apex and absorption apex, can be used to retrieval also, but effective matching strategy should be adopted. The quantitative indexes for spectral curves such as moment, fractal and entropy are not suitable to retrieval because of poor similarity measure performance.

Algorithms↗

PubMed2005

[The analysis of error sources for SAM and its improvement algorithms].

Based on the analysis of the error sources for spectral anglemapping (SAM), several key elements are pointed out, i.e. the change of wave band location, the change of the attribution ratio, the random change of attribution, and the whole translation of wave band. After the above-mentioned four error sources are analyzed, the authors present several improvement algorithms, viz. calculating the spectral angle with grouping, normalization and intersection. The grouping method can resolve the pseudo-similar problem, because it considers both spectral global features and local features. Calculating spectral angle with normalization restrains those random errors in original data by normalizing the spectral vectors. The intersection method can eliminate the error elicited by the whole wave translation. Therefore, it can be employed to correctly identify spectral class. Experiments show that those improvement algorithms are effective and can be used to process spectral data with errors.

Algorithms↗

PubMed2004

Acid volatile sulfide and simultaneously extracted metals in the sediment cores of the Pearl River Estuary, South China.

The acid-volatile sulfide (AVS), simultaneously extracted metals (SEM), total metals, and chemical partitioning in the sediment cores of the Pearl River Estuary (PRE) were studied. The concentrations of total metals, AVS, and SEM in the sediment cores were generally low in the river outlet area, increased along the seaward direction, and decreased again at the seaward boundary of the estuary. The amounts of AVS were generally greater in deeper sediments than in surface sediments. SEM/AVS was >1 in the surface sediments and in the river outlet cores. The ratio was <1 in the sediments down the profiles, suggesting that AVS might play a major role in binding heavy metals in the deep sediments of the PRE. The SEM may contain different chemical forms of trace metals in the sediments, depending on the metal reaction with 1M cold HCl in the AVS procedure compared with the results of the sequential chemical extraction. The SEM/AVS ratio prediction may overestimate trace metal availability even in the sediments with high AVS concentrations.

Biological Availability↗

PubMed2004

Combination of supercritical CO2 and vacuum distillation for the fractionation of bergamot oil.

Supercritical CO2 can be used to separate oxygenated compounds from essential oils. This technique still cannot replace vacuum distillation as an industrial process because of low recoveries and inconsistent results. In the present work, a comparison between the two methods was made in terms of composition, recovery, and color. Vacuum distillation and supercritical CO2 are complementary processes for producing high quality oxygenated compounds with high recovery rates. The former is more suitable for removing monoterpenes at low fraction temperatures (< or =308 K), and the latter is more suitable for separating oxygenated compounds from pigments and waxes. Consequently, the two methods were combined. For supercritical CO2 fractionation, the parameters of pressure, temperature gradient, and the ratio of solvent to feed were investigated for the fractionation of oxygenated compounds with high recoveries (> or =85%) and without other macromolecules, such as pigments and waxes.

Chemical Fractionation↗