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Biomedical subjects

Peng Zhang

Publications and source records attributed to Peng Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2006

Investigation on the sonocatalytic degradation of parathion in the presence of nanometer rutile titanium dioxide (TiO2) catalyst.

The nanometer rutile titanium dioxide (TiO2) powder was adopted to act as the sonocatalyst after treatment of high-temperature activation and the ultrasound of low power was used as an irradiation source to induce heat-treated TiO2 powder performing sonocatalytic degradation of parathion. Although there are many factors influencing sonocatalytic degradation of parathion, the experimental results demonstrate that the optimal degradation condition of parathion can be obtained when the experimental conditions such as initial concentration of 50 mg/L parathion, addition amount of 1000 mg/L nanometer rutile TiO2, ultrasonic of 30-50 kHz frequency and 50 W output power, acidity of pH 10.0 and temperature of 20 degrees C are adopted. The degradation ratio of parathion surpassed 90% within 120 min ultrasonic irradiation in these optimal experiment conditions. The total degradation process of parathion has been monitored by UV-vis spectra and ion chromatography. At last, the parathions in aqueous solution are completely degraded and become some simple inorganic ions such as NO3(-), PO4(3-), SO4(2-), etc. In addition, the sonocatalytic activities of reused TiO2 catalysts were also studied and found to decline gradually along with the reused times. In this paper, the research on sonocatalytic degradation kinetics was also been performed and found to follow pseudo first-order reaction. All experiments indicated that the sonocatalytic method in the presence of nanometer rutile TiO2 powder was an advisable choice for the treatments of non- or low-transparent organic wastewaters in future.

Catalysis↗
PubMed2006

Phylogeny, evolution, and biogeography of Asiatic Salamanders (Hynobiidae).

We sequenced 15 complete mitochondrial genomes and performed comprehensive molecular phylogenetic analyses to study the origin and phylogeny of the Hynobiidae, an ancient lineage of living salamanders. Our phylogenetic analyses show that the Hynobiidae is a clade with well resolved relationships, and our results contrast with a morphology-based phylogenetic hypothesis. These salamanders have low vagility and are limited in their distribution primarily by deserts, mountains, and oceans. Our analysis suggests that the relationships among living hynobiids have been shaped primarily by geography. We show that four-toed species assigned to Batrachuperus do not form a monophyletic group, and those that occur in Afghanistan and Iran are transferred to the resurrected Paradactylodon. Convergent morphological characters in different hynobiid lineages are likely produced by similar environmental selective pressures. Clock-independent molecular dating suggests that hynobiids originated in the Middle Cretaceous [ approximately 110 million years ago (Mya)]. We propose an "out of North China" hypothesis for hynobiid origins and hypothesize an ancestral stream-adapted form. Given the particular distributional patterns and our molecular dating estimates, we hypothesize that: (i) the interior desertification from Mongolia to Western Asia began approximately 50 Mya; (ii) the Tibetan plateau (at least on the eastern fringe) experienced rapid uplift approximately 40 Mya and reached an altitude of at least 2,500 m; and (iii) the Ailao-Red River shear zone underwent the most intense orogenic movement approximately 24 Mya.

Animals↗
PubMed2006

Social organization of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains, Central China.

Sichuan snub-nosed monkeys were observed for 197 days from 2000 to 2003 in the Qinling Mountains, Central China. The study group was provisioned in 2001 allowing detailed observations of social organization based on individual identification. The group was composed of 45-82 monkeys, all of which belonged to one of 6-8 one-male units (OMU) that foraged to form one big group. The average unit size was 9.0+/-2.3, 8+/-1.5 in the winter and 11.1+/-2.0 in the spring. Immigration or emigration of one-male units to or from the foraging group was observed, as was migration of individuals in and out of OMU, especially for by subadult females and juveniles. Group size therefore tended to fluctuate with the number of OMU and the number of young monkeys present in the group. The OMU in the study area were smaller than those in Shennongjia area. The factors influencing the size of these OMU and the entire group are discussed.

Age Distribution↗
PubMed2006

Vibrational spectroscopic studies of the interaction of water with serine.

The vibrational dynamics of water around serine was investigated by using Raman spectroscopy and inelastic incoherent neutron scattering. Experiments with serine in deuterium oxide were performed to assist the assignment. The study shows that for the serine, the exchange of protons-deuterons on the active -NH3+ and -OH groups were relatively easy, whereas there were hardly any exchanged on the -CH or -CH2- groups. The main features of the spectra for hydrated samples (versus the dry samples) were altered considerably; new sharp peaks in the measured spectra appeared, indicating that the hydrogen bonding between water and serine had disturbed the structure of the serine molecule.

Hydrogen Bonding↗
PubMed2006

Shock wave propagation in vibrofluidized granular materials.

Shock wave formation and propagation in vertically vibrated quasi-two-dimensional granular materials are studied by digital high speed photography. Steep density and temperature wave fronts form at the bottom of the granular layer when the layer collides with vibrating plate. Then the fronts propagate upwards through the layer. The temperature front is always in the transition region between the upward and downward granular flows. The effects of driving parameters and particle number on the shock are also explored.

Journal Article↗
PubMed2006

Known-plaintext attack on optical encryption based on double random phase keys.

We demonstrate a new approach to known-plaintext attack on an optical encryption scheme based on double random phase keys. With this attack an opponent can access both random phase keys with the help of the phase retrieval technique. This demonstration shows that an optical encryption scheme based on double random encoding is vulnerable to known-plaintext attack.

Journal Article↗
PubMed2006

Synthesis, structures, and luminescent properties of phenol-pyridyl boron complexes.

Syntheses of the four mixed phenol-pyridine derivatives 1,6-bis(2-hydroxyphenyl)pyridyl boron naphthalene (1), 1,6-bis(2-hydroxy-5-methylphenyl)pyridyl boron naphthalene (2), 1,6-bis(2-hydroxyphenyl)pyridyl boron 2-methoxylbenzene (3), and 1,6-bis(2-hydroxy-5-methylphenyl)pyridyl boron 2-methoxylbenzene (4) are reported. The structures of the boron compounds 1, 3, and 4 were determined by single-crystal X-ray diffraction. The molecular packing is characterized by intermolecular pi...pi and hydrogen-bonding interactions. DSC analysis demonstrates that 1 and 2 have good thermal stability with higher glass transition temperatures (Tg) and melting points (Tm) than 3 and 4. Boron complexes 1-4 display bright blue luminescence in solution and the solid state. White and blue electroluminescent (EL) devices were fabricated successfully using these boron compounds.

Boron Compounds↗
PubMed2006

One-dimensional spatial dark soliton-induced channel waveguides in lithium niobate crystal.

The anisotropic dependence of the formation of one-dimensional (1-D) spatial dark solitons on the orientation of intensity gradients in lithium niobate crystal is numerically specified. Based on this, we propose an approach to fabricate channel waveguides by employing 1-D spatial dark solitons. By exposure of two 1-D dark solitons with different orientations, channel waveguides can be created. The structures of the channel waveguides can be tuned by adjustment of the widths of the solitons and/or the angles between the two exposures. A square channel waveguide is experimentally demonstrated in an iron-doped lithium niobate crystal by exposure of two orthogonal 1-D dark solitons in sequence.

Journal Article↗
PubMed2006

Hyperhomocysteinemia and low plasma folate as risk factors for central retinal vein occlusion: a case-control study in a Chinese population.

PURPOSE: To determine whether hyperhomocysteinemia and low plasma folate are risk factors for central retinal vein occlusion (CRVO) in the Chinese population. METHODS: A matched case-control study was conducted between July 2004 and May 2005. The study cohort consisted of 64 individuals that had been diagnosed to have CRVO and 64 normal controls (matched for age, gender, hypertension, smoking and drinking habits). None of the cases or controls had a history of diabetes, glaucoma, medication or any other vascular events that might minimize the influence on plasma homocysteine levels. A cross-sectional analysis among the 64 cases was performed to compare the prevalence of hyperhomocysteinemia and low plasma folate among subjects with and without ischemia and subjects with age above 45 and below 45 years. Plasma homocysteine level was measured by means of high-performance liquid chromatography and plasma folate concentration by radioimmunoassay. RESULTS: The CRVO patients had a significantly higher homocysteine level (13.83+/-1.71 micromol/l) than the normal controls (8.05+/-0.58 micromol/l; p=0.003). The plasma folate levels were significantly lower in CRVO patients than in controls (5.62+/-0.39 ng/dl vs 7.23+/-0.60 ng/dl; p=0.032). A 1 micromol/l increase of plasma homocysteine level was associated with an odds ratio of 1.368. Hyperhomocysteinemia was defined as a homocysteine level of >14.97 micromol/l and was seen in 11 patients in the ischemic group, significantly more often than in the non-ischemic group (5 patients; p=0.030). CONCLUSIONS: The results suggest that hyperhomocysteinemia and low plasma folate are independent risk factors for CRVO and are associated with the development of CRVO in the Chinese population.

Adult↗
PubMed2006

A study of the reaction of N+ with O2: experimental quantification of NO+(a 3Sigma+) production (298-500 K) and computational study of the overall reaction pathways.

The product branching ratios for NO+(X 1Sigma+) and NO+(a 3Sigma+) produced from the reaction of N+ with O2 have been measured at 298 and 500 K in a selected ion flow tube. Approximately 0.5% of the total products are in NO+(a) at both temperatures, despite the fact that the reaction to form NO+(a) is 0.3 eV exothermic. High-level ab initio calculations of the potential energy surfaces for the N+ + O2 reaction show that the reaction from N+(3P) + O2(3Sigma(g)) reactants starts with an efficient early stage charge transfer to the N(2D) + O2+(X 2Pi) channel, which gives rise to the O2+(X 2Pi) product and, at the same time, serves as the starting point for all of the reaction channels leading to NO+ and O+ products. Pathways to produce NO+(a 3Sigma+) are found to be less favorable than pathways leading to the major product NO+(X 1Sigma+). Production of N(2D) has implications for the concentration of NO in the mesosphere.

Journal Article↗
PubMed2006

An experimental and theoretical study of ring closing dynamics in HN3.

We report on an H(D)-atom Rydberg tagging experiment for H(D)N(3) photolysis providing detailed dynamical information on the wavelength dependence of the H(D) + N(3) channel. We observe subtle yet striking changes in the photochemical dynamics as the photolysis energy passes through approximately 5.6 eV. In addition to producing linear azide with an average of approximately 40% of available energy appearing as translation, a second H(D)-atom producing channel grows in above this energy releasing only about 15%. An observed (inverse) isotope effect suggests that statistical decomposition on S(0) is unimportant. High level ab initio quantum chemical calculations reveal a transition state to cyclization of the N(3) moiety in H(D)N(3) on the first excited singlet (S(1)) surface that is close in energy to the experimentally observed threshold energy for this "slow channel". Furthermore, the translational energy release of the "slow channel" is energetically consistent with cyclic-N(3) formation. This work provides the clearest presently available insights into how ring closure can occur in azide photochemistry.

Azides↗
PubMed2006

[Histochemical and ultrastructure study of bile cast in liver transplantation patients].

OBJECTIVE: To investigate the histological components and solubility of the bile-cast, and to study the pathological course of bile cast formation. METHODS: HE staining, bilirubin staining (Gmelin reaction), Masson's staining, alcian blue staining and fibrin staining (weigert's) were performed on the formalin-fixed paraffin-embedded section of the bile cast. Ultrastructure was examined under the scanning electron microscope. Solubility test was also conducted using chymotrypsin, heparin, trypsin solution, HCl and NaOH solution to dissolve the bile-cast. RESULTS: The major components of the bile-cast were bilirubin crystals and collagen fibers. Between the mass of collagen fibers there was certain blood vessel structure. Necrosis bile duct structure was not found in the cast. Under the scanning electron microscope, four kinds of crystal morphologies were viewed. There were some mucoid mass and necrosis defluvium epithelial cells in the bile cast. Solubility test showed that the bile cast could be partial dissolved in NaOH solution (pH = 12.5). No dissolution was found in HCl solution (pH = 5.0), chymotrypsin solution, heparin and trypsin solution. CONCLUSIONS: Collagen fibers work as framework in the bile cast with bilirubin crystal filling between the framework. The emergence of fibroblast and blood vessels indicated the formation of bile cast might be the course of exudation and organization due to bile duct epithelium damage. Bile cast could be partially dissolved in alkaline solution, but could not be dissolved in acid solution, or in chymotrypsin, heparin and trypsin solutions.

Bile Duct Diseases↗
PubMed2006

Improvement of proline enantioselective stationary phases by replacing the 9-fluorenylmethoxycarbonyl group.

The role of 9-fluorenylmethoxycarbonyl (Fmoc) in previously reported proline enantioselective stationary phases was investigated. Seven stationary phases in which the Fmoc group was replaced by other groups were prepared and evaluated in normal phase mode. The Fmoc group proved nonessential for the broad enantioselectivity observed, as the stationary phase with a trimethylacetyl (Tma) group proved much more effective than the one with the Fmoc group. For the 53 analytes studied, the stationary phase with the Tma group resolved 39, while the one with the Fmoc group resolved 19. Separation factors achieved for the stationary phase with the Tma group are also significantly higher than those for the stationary phase with the Fmoc group. The stationary phase with the (-)-2-(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)propionyl (Tapa) group provides very different selectivity profile when compared to the one with the Tma group. In most of the proline stationary phases studied, pi-pi interaction is not the dominant interaction for the enantioselective recognition.

Fluorenes↗
PubMed2006

Investigation of novel quantum dots/proteins/cellulose bioconjugate using NSOM and fluorescence.

We investigated the engineered bioconjugate of cadmium selenide core/zinc sulfide shell, (CdSe)ZnS, quantum dots (QDs) with genetically modified proteins using fluorescence spectroscopy, near-field scanning optical microscopy (NSOM) and spectroscopy (NSOS). The protein polymer was allowed to self-assemble to the bacterial microcrystalline cellulose surface through the cellulosic binding domain. Results from the sample containing the QDs/protein/cellulose assemblies suggest that QDs were arrayed along the cellulose surface. The spectroscopic change of spectroscopic properties of the QDs upon bioconjugation, indicating the interaction among the immobilized QDs and between the constructed protein and QDs.

Buffers↗
PubMed2006

Role of positive selection in the retention of duplicate genes in mammalian genomes.

The question of how duplicate genes are retained in a population remains controversial. The duplication-degeneration-complementation model, which involves no positive selection, stipulates a higher retention rate of duplicate genes in a small population than in a large one. This model has been accepted by many evolutionists. However, we found considerably more retentions and fewer losses of duplicate genes in the mouse genome than in the human genome, although the population size of rodents is in general larger than that of primates. Indeed, in nearly every interval of synonymous divergence between duplicate genes, the number of gene retentions in mouse is larger than that in human. Our findings suggest a more important role of positive selection in duplicate retention than duplication-degeneration-complementation. In addition, certain functional categories show a higher tendency of lineage-specific expansion than expected, suggesting lineage-specific selection or functional bias in retained duplicates.

Animals↗
PubMed2006

Shear stress regulation of Krüppel-like factor 2 expression is flow pattern-specific.

Flow patterns in blood vessels contribute to focal distribution of atherosclerosis; the underlying mechanotransduction pathways remain to be investigated. We demonstrate that different flow patterns elicit distinct responses of Krüppel-like factor-2 (KLF2) in endothelial cells (ECs) in vitro and in vivo. While pulsatile flow with a significant forward direction induced sustained expression of KLF2 in cultured ECs, oscillatory flow with little forward direction caused prolonged suppression after a transient induction. The suppressive effect of oscillatory flow was Src-dependent. Immunohistochemical studies on ECs at arterial branch points revealed that KLF2 protein levels were related to local hemodynamics. Such flow-associated expression patterns were also demonstrated in a rat aortic restenosis model. Inhibition of KLF2 with siRNA sensitized ECs to oxidized LDL-induced apoptosis, indicating a protective role of KLF2. In conclusion, differential regulation of KLF2 may mediate the distinct vascular effects induced by various patterns of shear stress.

Animals↗
PubMed2006

Molecular characterization of geminivirus-derived small RNAs in different plant species.

DNA geminiviruses are thought to be targets of RNA silencing. Here, we characterize small interfering (si) RNAs-the hallmarks of silencing-associated with Cabbage leaf curl begomovirus in Arabidopsis and African cassava mosaic begomovirus in Nicotiana benthamiana and cassava. We detected 21, 22 and 24 nt siRNAs of both polarities, derived from both the coding and the intergenic regions of these geminiviruses. Genetic evidence showed that all the 24 nt and a substantial fraction of the 22 nt viral siRNAs are generated by the dicer-like proteins DCL3 and DCL2, respectively. The viral siRNAs were 5' end phosphorylated, as shown by phosphatase treatments, and methylated at the 3'-nucleotide, as shown by HEN1 miRNA methylase-dependent resistance to beta-elimination. Similar modifications were found in all types of endogenous and transgene-derived siRNAs tested, but not in a major fraction of siRNAs from a cytoplasmic RNA tobamovirus. We conclude that several distinct silencing pathways are involved in DNA virus-plant interactions.

Arabidopsis↗