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Juan Yang

Publications and source records attributed to Juan Yang.

At least 19 recordsLinked to original sources
PubMed2026

Morphology-engineered NiFe@C nanocages boosting electrochemical quantification of ractopamine in meat samples.

It is essential to acquire efficient electrocatalysts to develop ractopamine (RAC) electrochemical sensors. Herein, we report the synthesis of a series of carbon coated NiFe alloy nanostructures (e.g., NiFe@C nanoparticles, nanocubes and nanocages) using NiFe Prussian blue analogue (PBA) as the precursor. The NiFe@C nanocages exhibited the best electrocatalytic performance for RAC sensing. This is attributed to the embedded NiFe alloy nanoparticles that provide abundant active sites, and the unique nanocage structure facilitates electron transfer pathways while offering a high specific surface area. The resulting sensor achieves a low detection limit (LOD) of 54 nM (S/N = 3) within a linear range of 0.2-12 μM. Moreover, the sensor demonstrates good reproducibility, stability, and excellent long-term stability. Practical applicability was confirmed in meat samples, yielding satisfactory recovery rates ranging from 98% to 108%. A feasible strategy was introduced herein for rational design of metal@carbon electrocatalysts.

Phenethylamines↗
PubMed2006

Laser-induced fluorescence spectra, structure, and the ring-twisting and ring-bending vibrations of 1,4-benzodioxan in its S0 and S1(pi,pi*) states.

The laser-induced fluorescence (LIF) spectra, both the fluorescence excitation spectra (FES) and single vibrational level fluorescence spectra (SVLF) from several different vibronic states, along with the ultraviolet (UV) absorption spectra of 1,4-benzodioxan have been recorded and analyzed. A detailed energy map has been constructed for four low-frequency vibrations and their combinations for both the S(0) and S(1)(pi,pi) electronic states. These are nu(48) (ring-bending), nu(25) (ring-twisting), nu(47) (ring-flapping), and nu(24) (skeletal-twisting). Both the experimental and ab initio calculations show the molecule to be twisted in both the S(0) and S(1)(pi,pi) states with high barriers to planarity. The experimentally determined ring-twisting quantum states, which are confined to the lower regions of the potential energy surface, were used to calculate one-dimensional potential functions in terms of the twisting coordinates, and the extrapolated barriers were estimated to be 5700 and 4200 cm(-1) for the S(0) and S(1) states, respectively. Two-dimensional calculations, which included the interactions with the bending modes, gave values of 3906 and 1744 cm(-1), respectively. The S(0) value compares favorably with the ab initio value of 4095 cm(-1).

Journal Article↗
PubMed2006

Fluorescence and ultraviolet absorption spectra and structure of coumaran and its ring-puckering potential energy function in the S1(pi,pi*) excited state.

The fluorescence excitation (jet cooled), single vibrational level fluorescence, and the ultraviolet absorption spectra of coumaran associated with its S1(pi,pi*) electronic excited state have been recorded and analyzed. The assignment of more than 70 transitions has allowed a detailed energy map of both the S0 and S1 states of the ring-puckering (nu45) vibration to be determined in the excited states of nine other vibrations, including the ring-flapping (nu43) and ring-twisting (nu44) vibrations. Despite some interaction with nu43 and nu44, a one-dimensional potential energy function for the ring puckering very nicely predicts the experimentally determined energy level spacings. In the S1(pi,pi*) state coumaran is quasiplanar with a barrier to planarity of 34 cm(-1) and with energy minima at puckering angles of +/-14 degrees. The corresponding ground state (S0) values are 154 cm(-1) and +/-25 degrees . As is the case with the related molecules indan, phthalan, and 1,3-benzodioxole, the angle strain in the five-membered ring increases upon the pi-->pi* transition within the benzene ring and this increases the rigidity of the attached ring. Theoretical calculations predict the expected increases of the carbon-carbon bond lengths of the benzene ring in S1, and they predict a barrier of 21 cm(-1) for this state. The bond length increases at the bridgehead carbon-carbon bond upon electron excitation to the S1(pi,pi*) state give rise to angle changes which result in greater angle strain and a nearly planar molecule.

Journal Article↗
PubMed2006

Brain mechanism of cognitive conflict in a guessing Chinese logogriph task.

To investigate the neural substrates of cognitive conflict in high-level thought processing, we recorded event-related potentials while participants thought about the logogriph answers. We identified three states after the answers were provided: (1) the answer given was just what the participants initially guessed (No-aha answer). (2) Participants could understand the answer given correctly although they had not got the answer themselves (Aha answer). (3) Participants could not understand the correct answer offered (Uncomprehended answer). Results showed that, relative to the No-aha answer, the Aha and Uncomprehended answers elicited more negative event-related potential deflections between 250 and 400 ms. The dipole analysis localized the generator of the difference waves (Aha minus No-aha answer) to the anterior cingulate cortex. Thus, it might reflect the cognitive conflict center between familiar and new ways of processing the logogriphs.

Adult↗
PubMed2006

Genotypic and environmental variation in barley limit dextrinase activity and its relation to malt quality.

Variation in the limit dextrinase activity of barley malt, and the relationships between limit dextrinase activity and malt quality parameters were investigated using eight cultivars grown at seven diverse locations in China for two successive years. Limit dextrinase activity varied with genotype and location, with the levels ranging from 0.245 U/g to 0.980 U/g. The results showed that the variation in limit dextrinase activity was more attributable to the environment (location and year) than to the genotype. The response of limit dextrinase activity to the environment differed markedly among cultivars, and was reflected by large difference in coefficient of variation of cultivars across diverse locations. Regression analysis showed that limit dextrinase activity was negatively correlated with malt viscosity (r=-0.52, P<0.01), positively correlated with Kolbach index (r=0.38, P<0.01) and malt extract (r=0.30, P<0.05), but had no significant correlation with malt protein content and diastatic power.

Beer↗
PubMed2006

[Dynamic changes of morphological parameters of tobacco root in field].

The study with rhizotron showed that the total length of tobacco's second order lateral root had a much more increase than that of first order one, and the root length developed rapidly during 26 to approximately 40 d and 56 to approximately 70 d after transplanting for the second and first order lateral root, respectively. Before tip pruning, the branch root density of tobacco was decreased in order of 10 to approximately 20 > 0 to approximately 10 > 20 to approximately 30 > 30 to approximately 40 cm soil layer. The branch density of main root was the highest in 7 to approximately 21 cm soil layer. The deeper the soil layer, the bigger the ratio of dry weight and root length, but the distribution was reverse at 90 d after transplanting. The first order lateral root length density distributed in "S" curve in 0 to approximately 10 cm soil layer and in double climax curve in 10 to approximately 20, 20 to approximately 30 and 30 to approximately 40 cm soil layers, while the second order lateral root length density became bigger with the course of growth period, which was in "S" curve in 0 to approximately 10 cm soil layer and in single climax curve in other soil layers.

Plant Roots↗
PubMed2006

[Studies on chemical constituents in rhizome of Elaeagnus bockii I].

OBJECTIVE: To study the chemical constituents in the rhizome of Elaeagnus bockii. METHOD: Compounds were isolated by silica gel and Sephadex LH-20 chromatography. Their structures were elucidated by means of spectral analysis. RESULT: Seven compounds were isolated from the rhizomes of E. bockii, and their structures were identified as angelicin (1), psoralen (2), vanillic acid (3), bakuchiol (4), oleanolic acid (5), ursolic acid (6) and beta-sitosterol (7 ). CONCLUSION: All these compounds were obtained from E. bockii for the first time.

Elaeagnaceae↗
PubMed2005

Mechanism of TiO2-assisted photocatalytic degradation of dyes under visible irradiation: photoelectrocatalytic study by TiO2-film electrodes.

Photoelectrocatalytic degradation of various dyes under visible light irradiation with a TiO(2) nanoparticles electrode has been investigated to reveal the mechanism for TiO(2)-assisted photocatalytic degradation of dyes. The degradation of both cationic and anionic dyes at different biases, including the change in the degradation rate of the dyes and the photocurrent change with the bias potential, the degraded intermediates, the voltage-induced adsorption of dyes, the accumulation of electrons in the TiO(2) electrode, the effect of various additives such as benzoquinone (BQ) and N,N-dimethyl aniline (DMA), and the formation of active oxygen species such as O(2)(*-) and H(2)O(2) were examined by UV-visible spectroscopy, HPLC, TOC, and spin-trap ESR spectrometry. It was found that the dyes could controllably interact with the TiO(2) surface by external bias changes and charging of dyes. The cationic dyes such as RhB and MG underwent efficient mineralization at negative bias, but the N-dealkylation process predominated at positive bias under visible light irradiation. The discolorations of the anionic dyes SRB and AR could not be accelerated significantly at either negative or positive bias. At a negative bias of -0.6 V vs SCE, O(2)(*-) and dye(*+) were formed simultaneously at the electrode/electrolyte interface during degradation of cationic RhB. In the case of anionic dyes, however, it is impossible for the O(2)(*-) and dye cationic radical to coexist at the electrode/electrolyte surface. Experimental results imply both the superoxide anionic radical and the dye cationic radical are essential to the mineralization of the dyes under visible light-induced photocatalytic conditions.

Adsorption↗
PubMed2005

Degradation of dye pollutants by immobilized polyoxometalate with H2O2 under visible-light irradiation.

A Keggin polyoxometalate (POM, i.e., PW12O40(3-)) and its lacunary derivative are immobilized on an anionic exchange resin through electrostatic interaction at pH 4.6 in an aqueous dispersion. The resin-supported POM thus obtained catalyzes the efficient degradation of cationic dye pollutants in the presence of H2O2 under visible-light irradiation. To evaluate the photocatalytic system, degradation of a rhodamine B (RB) dye was investigated in detail using UV-visible spectroscopy, high performance liquid chromatography, and gas chromatography/mass spectrometry techniques to identify the intermediates and final products. Fluorescence lifetime measurements revealed the electron transfer from the visible-light-excited RB molecules to the POMs. Electron paramagnetic resonance measurements, investigation of the effects of *OH and *OOH scavengers on the photoreaction kinetics, and IR analysis indicated that de-ethylation of RB was due to *OOH radicals, but the decomposition of the conjugated xanthene structure was caused by the peroxo species formed by interaction of H2O2 with the lacunary POM loaded on the resin. A total organic carbon removal of ca. 22% was achieved, and the recycle experiment suggested excellent stability and reusability of the heterogeneous catalyst. On the basis of the experimental results, a photocatalytic mechanism is discussed.

Catalysis↗
PubMed2005

S0 ring-puckering potential energy function for coumaran.

With the aid of a reported inversion splitting value, the far-infrared spectrum resulting from the ring-puckering vibration of coumaran has been reassigned and the one-dimensional potential energy function has been determined. The barrier to planarity is 155 +/- 4 cm(-1) and the dihedral angle is 25 degrees . These results agree well with the millimeter wave spectra values of 152 cm(-1) and 23 degrees , which utilized different data and a different type of potential function for the calculations. The MP2/cc-pvtz ab initio values of 238 cm(-1) and 26.5 degrees agree more poorly. If the benzene ring is assumed to remain rigid, the calculated barrier drops to 204 cm(-1). The puckering potential functions for the ring-flapping and ring-twisting vibrationally excited states were also determined and the barriers were found to be 149 and 156 cm(-1), respectively.

Journal Article↗
PubMed2005

Fabrication of rutile rod-like particle by hydrothermal method: an insight into HNO3 peptization.

In this work, well-crystallized and well-dispersed rod-like TiO(2) rutile particles were prepared by hydrothermally treating acid-peptized TiO(2) sols at relatively low temperatures of 200 and 240 degrees C. Raman spectra, transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the peptized sols before and after hydrothermal treatment. The results showed that HNO(3) peptization of amorphous TiO(2) was able to promote, at room temperature, the formation of crystalline phases of anatase or rutile, at low (HNO(3)/Ti=1) or at high (HNO(3)/Ti=4) concentrations of peptizer, respectively. However, after hydrothermal treatment, well-crystalline rutile developed independent of the starting concentration of the peptizer. The formation of well-dispersed rutile particles is attributed to high long-range electrostatic forces between particles in the presence of the high concentration of the peptizer. The acid peptization would easily break the oxolation bonds between triple bond Ti-O-Ti triple bond, promote the formation of titanium species with fewer oxolation bonds depending on the amount of acid, and create conditions for the formation of rutile nuclei after structural rearrangements.

Journal Article↗
PubMed2005

Reducing misclassification in assignment of timing of events during pregnancy.

BACKGROUND: Perinatal epidemiology studies often collect only the calendar month in which an event occurs in early pregnancy because it is difficult for women to recall a specific day when queried later in pregnancy or postpartum. Lack of day information may result in incorrect assignment of completed gestational month because calendar months and pregnancy months are not aligned. METHODS: To examine the direction and magnitude of misclassification, we compared 3 methods for assignment of completed gestational month: 1) calendar month difference, 2) conditional month difference, and 3) imputed month midpoint. We used data from the Pregnancy, Infection, and Nutrition Study for simulations. RESULTS: Calendar month difference misclassified 54% of events as 1 month later in pregnancy compared with the actual completed month of gestation. Each of the other 2 methods misclassified approximately 12% of events to 1 month earlier and 12% to 1 month later. CONCLUSIONS: Calendar month difference, a common method, has the greatest misclassification. Conditional month difference and imputed month midpoint, which require little effort to implement, are superior to calendar month difference for reducing misclassification.

Cohort Studies↗
PubMed2005

Predictors of vaginal bleeding during the first two trimesters of pregnancy.

This study evaluates maternal age, race, cigarette smoking, prior spontaneous abortion, prior induced abortion, and prior preterm birth in relation to vaginal bleeding during the first two trimesters of pregnancy. Information on vaginal bleeding and predictors came from the Pregnancy, Infection, and Nutrition Study, which enrolled 2806 pregnant women at 24-29 weeks' gestation during 1995-2000 in central North Carolina, USA. Generalised estimating equations were applied to take into account repeated episodes of vaginal bleeding during pregnancy. Women with advanced maternal age and passive smoking exposure were more likely to experience more intense vaginal bleeding during pregnancy, as were women with prior preterm birth. More intense bleeding was also more likely to be reported among women with multiple prior spontaneous abortions or multiple prior induced abortions, but not among women with a single prior spontaneous or induced abortion. The combination of prior spontaneous and induced abortion showed a dose-response association with the occurrence of vaginal bleeding during pregnancy.

Abortion, Habitual↗
PubMed2005

[Genetic analysis of starch branching enzyme activity in rice grain].

To make an genetic analysis of starch branching enzyme (Q enzyme) inheritance, which is important in catalyzing the formation of amylopectin and thereby raising the amylopectin/amylose ratio of starch in rice grains, a linkage map of 207 DNA markers were constructed by using 247 recombinant inbred lines derived from an indica-indica rice cross Zhenshan 97B/Milyang46. In 2002 and 2003, the activities of starch branching enzyme of the parents and 247 RILs were measured 10 d and 20 d respectively after flowering (Table 1). A total of 3 quantitative trait loci (QTLs) were detected to have significant additive effects on Q enzyme activities 10 d after flowering with 10% phenotypic variations explained for the three QTLs (Table 2, Fig.1). Meanwhile, qQ10-6 with significant QTL x environment interaction was detected. Epistasis analysis detected 5 and 2 significant additive-by-additive interactions for Q enzyme 10 d and 20 d respectively after flowering (Table 3), and three pairs of QTLs 10 d after flowering with significant epistasis x environment interactions were detected, explaining 3% to 12% of the phenotypic variation. The results showed that the environmental factors had obvious effect on the gene expression of Q enzyme activity in rice grain. Meanwhile, the location of qQ10-6 in relation to that of QTLs for gelatinization temperature, gene loci involved in ADPG pyrophosphorylase and soluble starch synthase were discussed with the help of a genetic map.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2004

Vaginal bleeding during pregnancy and preterm birth.

This study investigated the relation between self-reported vaginal bleeding during pregnancy and preterm birth in a prospective cohort of 2,829 pregnant women enrolled from prenatal clinics between 1995 and 2000 in central North Carolina. The overall association between vaginal bleeding and preterm birth was modest (risk ratio (RR) = 1.3, 95% confidence interval (CI): 1.1, 1.6). Bleeding in the first trimester only was associated with earlier preterm birth (< or =34 weeks' gestation) (RR = 1.6, 95% CI: 1.1, 2.4) and preterm birth due to preterm premature rupture of the membranes (PPROM) (RR = 1.9, 95% CI: 1.1, 3.3). Bleeding in both trimesters was associated with preterm birth due to preterm labor (RR = 3.6, 95% CI: 1.9, 6.8). Bleeding of multiple episodes, on multiple days, and with more total blood loss was associated with an approximate twofold increased risk of earlier preterm birth, PPROM, and preterm labor. In contrast, bleeding in the second trimester only, of a single episode, on a single day, and with less total blood loss was not associated with any category of preterm birth. Vaginal bleeding was not associated with preterm birth among African Amercians (RR = 1.2, 95% CI: 0.9, 1.7). This study indicates that more intense but not less intense bleeding is associated with earlier preterm birth and spontaneous preterm birth presenting as PPROM or preterm labor, and it suggests that bleeding is less predictive of preterm birth among African-American compared with White women.

Adult↗
PubMed2004

Sol-gel preparation and in vitro test of fluorapatite/hydroxyapatite films.

Fluorapatite/hydroxyapatite (FA/HA) films have been demonstrated to be a good alternative to pure hydroxyapatite (HA) ones in medical applications because of their bioactivity and relatively low solubility. In this study, Ca(NO(3))(2), P(2)O(5), and HPF(6) were used to prepare FA/HA films on Ti6Al4V substrate with the use of a sol-gel method. The F contents in the films could be tailored by adjusting the amount of HPF(6) added. The in vitro evaluation of the films was carried out in both SBF9# solution and TRIS buffer solution. The films with appropriate F contents showed a better ability to induce calcium phosphate deposition on their surfaces than either pure HA film and FA/HA films with even higher F content, as well as smaller dissolution amounts than HA film in TRIS buffer solution. Hence, the FA/HA films obtained in this work integrate both good bioactivity and stability, and could be a better choice for bioactive film on titanium alloys to produce high-quality implants.

Apatites↗
PubMed2004

Risks of selected congenital malformations among offspring of mixed race-ethnicity.

BACKGROUND: Little is known about the occurrence of specific congenital malformations among offspring of mixed race-ethnicity. METHODS: Using data from a population-based registry, we explored the occurrence of selected malformation phenotypes in offspring to parents who were of different race-ethnicity. Data were derived from the California Birth Defects Monitoring Program, a population-based active surveillance system for collecting information on infants and fetuses with congenital malformations using multiple source ascertainment. Approximately 2.6 million live births and stillbirths occurred during 1989-2000. Information on parental race-ethnicity (non-Hispanic white, Hispanic, black, and Asian) was obtained from birth certificates and fetal death files. Malformation phenotypes studied were spina bifida, anencephaly, cleft lip, cleft palate, tetralogy of Fallot, d-transposition of great arteries, hypospadias, small intestinal atresia, preaxial polydactyly, microtia, and hypertrophic pyloric stenosis. RESULTS: A total of 11.2% of births were to parents of mixed race-ethnicity. Compared to births of parents who were both white, moderately increased risks (risk ratio >/= 1.7) of anencephaly, polydactyly, and microtia, and decreased risks (risk ratio </= 0.6) of hypospadias and hypertrophic pyloric stenosis were observed among births of several mixed race-ethnicity groups. For anencephaly, polydactyly, and microtia, but not other phenotypes, the risks were different depending on whether maternal versus paternal race-ethnicity was considered. Risks observed between births of a nonwhite parent and a white parent and births of parents who were both nonwhite were similar for most malformation phenotypes. CONCLUSIONS: Some malformation phenotypes appear to vary in their risk based on mixed racial-ethnic groupings.

California↗