Showing papers by "Qian Zhang published in 2012"

Enhancement of thermoelectric figure-of-merit by resonant states of aluminium doping in lead selenide

Abstract: By adding aluminium (Al) into lead selenide (PbSe), we successfully prepared n-type PbSe thermoelectric materials with a figure-of-merit (ZT) of 1.3 at 850 K. Such a high ZT is achieved by a combination of high Seebeck coefficient caused by very possibly the resonant states in the conduction band created by Al dopant and low thermal conductivity from nanosized phonon scattering centers.

Heavy doping and band engineering by potassium to improve the thermoelectric figure of merit in p-type PbTe, PbSe, and PbTe(1-y)Se(y).

Abstract: We present detailed studies of potassium doping in PbTe1–ySey (y = 0, 0.15, 0.25, 0.75, 0.85, 0.95, and 1). It was found that Se increases the doping concentration of K in PbTe as a result of the balance of electronegativity and also lowers the lattice thermal conductivity because of the increased number of point defects. Tuning the composition and carrier concentration to increase the density of states around the Fermi level results in higher Seebeck coefficients for the two valence bands of PbTe1–ySey. Peak thermoelectric figure of merit (ZT) values of ∼1.6 and ∼1.7 were obtained for Te-rich K0.02Pb0.98Te0.75Se0.25 at 773 K and Se-rich K0.02Pb0.98Te0.15Se0.85 at 873 K, respectively. However, the average ZT was higher in Te-rich compositions than in Se-rich compositions, with the best found in K0.02Pb0.98Te0.75Se0.25. Such a result is due to the improved electron transport afforded by heavy K doping with the assistance of Se.

Study of the Thermoelectric Properties of Lead Selenide Doped with Boron, Gallium, Indium, or Thallium

Abstract: Group IIIA elements (B, Ga, In, and Tl) have been doped into PbSe for enhancement of thermoelectric properties. The electrical conductivity, Seebeck coefficient, and thermal conductivity were systematically studied. Room-temperature Hall measurements showed an effective increase in the electron concentration upon both Ga and In doping and the hole concentration upon Tl doping to ∼7 × 1019 cm–3. No resonant doping phenomenon was observed when PbSe was doped with B, Ga, or In. The highest room-temperature power factor ∼2.5 × 10–3 W m–1 K–2 was obtained for PbSe doped with 2 atom % B. However, the power factor in B-doped samples decreased with increasing temperature, opposite to the trend for the other dopants. A figure of merit (ZT) of ∼1.2 at ∼873 K was achieved in PbSe doped with 0.5 atom % Ga or In. With Tl doping, modification of the band structure around the Fermi level helped to increase the Seebeck coefficient, and the lattice thermal conductivity decreased, probably as a result of effective phonon s...

Overexpression of OsPAP10a, A Root-Associated Acid Phosphatase, Increased Extracellular Organic Phosphorus Utilization in Rice

Abstract: Phosphorus (P) deficiency is a major limitation for plant growth and development. Among the wide set of responses to cope with low soil P, plants increase their level of intracellular and secreted acid phosphatases (APases), which helps to catalyze inorganic phosphate (Pi) hydrolysis from organo-phosphates. In this study we characterized the rice (Oryza sativa) purple acid phosphatase 10a (OsPAP10a). OsPAP10a belongs to group Ia of purple acid phosphatases (PAPs), and clusters with the principal secreted PAPs in a variety of plant species including Arabidopsis. The transcript abundance of OsPAP10a is specifically induced by Pi deficiency and is controlled by OsPHR2, the central transcription factor controlling Pi homeostasis. In gel activity assays of root and shoot protein extracts, it was revealed that OsPAP10a is a major acid phosphatase isoform induced by Pi starvation. Constitutive overexpression of OsPAP10a results in a significant increase of phosphatase activity in both shoot and root protein extracts. In vivo root 5-bromo-4-chloro-3-indolyl-phosphate (BCIP) assays and activity measurements on external media showed that OsPAP10a is a root-associated APase. Furthermore, overexpression of OsPAP10a significantly improved ATP hydrolysis and utilization compared with wild type plants. These results indicate that OsPAP10a can potentially be used for crop breeding to improve the efficiency of P use.

Isoleucine or valine deprivation stimulates fat loss via increasing energy expenditure and regulating lipid metabolism in WAT

Abstract: There has been a growing interest in controlling body weight by increasing dietary levels of leucine recently. By contrast, we have focused on studying the effect of deficiency of branched-chain amino acids (BCAAs) leucine on lipid metabolism. We previously have shown that mice fed a leucine-deficient diet for 7 days exhibit significant changes in lipid metabolism as demonstrated by suppressed lipogenesis in the liver and increased fat mobilization in white adipose tissue, the latter of which was found to be caused by increased lipolysis in WAT and uncoupling protein 1 expression in brown adipose tissue. The goal of our current study is to investigate whether the above effects of leucine deficiency can be generalized to the deficiency of other BCAAs including valine and isoleucine. In our current study, we show that valine or isoleucine deficiency has similar effects on reducing fat mass to leucine deprivation, in a similar manner as those observed during leucine deprivation.

Effect of silicon and sodium on thermoelectric properties of thallium-doped lead telluride-based materials.

Abstract: Thallium (Tl)-doped lead telluride (Tl0.02Pb0.98Te) thermoelectric materials fabricated by ball milling and hot pressing have decent thermoelectric properties but weak mechanical strength. Addition of silicon (Si) nanoparticles strengthened the mechanical property by reducing the grain size and defect density but resulted in low electrical conductivity that was not desired for any thermoelectric materials. Fortunately, doping of sodium (Na) into the Si added Tl0.02Pb0.98Te brings back the high electrical conductivity and yields higher figure-of-merit ZT values of ∼1.7 at 770 K. The ZT improvement by Si addition and Na doping in Tl0.02Pb0.98Te sample is the direct result of concurrent electron and phonon engineering by improving the power factor and lowering the thermal conductivity, respectively.

S6K1 in the Central Nervous System Regulates Energy Expenditure via MC4R/CRH Pathways in Response to Deprivation of an Essential Amino Acid

Abstract: It is well established that the central nervous system (CNS), especially the hypothalamus, plays an important role in regulating energy homeostasis and lipid metabolism. We have previously shown that hypothalamic corticotropin-releasing hormone (CRH) is critical for stimulating fat loss in response to dietary leucine deprivation. The molecular mechanisms underlying the CNS regulation of leucine deprivation–stimulated fat loss are, however, still largely unknown. Here, we used intracerebroventricular injection of adenoviral vectors to identify a novel role for hypothalamic p70 S6 kinase 1 (S6K1), a major downstream effector of the kinase mammalian target of rapamycin, in leucine deprivation stimulation of energy expenditure. Furthermore, we show that the effect of hypothalamic S6K1 is mediated by modulation of Crh expression in a melanocortin-4 receptor–dependent manner. Taken together, our studies provide a new perspective for understanding the regulation of energy expenditure by the CNS and the importance of cross-talk between nutritional control and regulation of endocrine signals.

Legumes Can Increase Cadmium Contamination in Neighboring Crops

Abstract: Legumes are widely used in many cropping systems because they share their nitrogen fixation products and phosphorus mobilization activities with their neighbors. In the current study, however, we showed that co-cultivation with legumes increased cadmium (Cd) contamination in the adjacent crops. Both field and mesocosm experiments indicated that legumes increased Cd levels in edible parts and shoots of four neighboring crops and five maize varieties tested, regardless of the Cd levels in the soil. This enhanced Cd accumulation in crops was attributed to root interactions that alter the rhizosphere environment. Co-cultivation with legumes reduced soil pH, which somewhat increased the exchangeable forms of Cd. Our results have demonstrated the inevitable increases in Cd levels of crops as a direct result of co-cultivation with legumes even under situations when these levels are below the permissible threshold. With this new revelation, we need to consider carefully the current cropping systems involving legumes and perhaps to re-design the current and future cropping systems in view of avoiding food contamination by Cd.

Hepatitis C virus activates Bcl-2 and MMP-2 expression through multiple cellular signaling pathways

Abstract: Hepatitis C virus (HCV) infection is associated with numerous liver diseases and causes serious global health problems, but the mechanisms underlying the pathogenesis of HCV infections remain largely unknown. In this study, we demonstrate that signal transducer and activator of transcription 3 (STAT3), matrix metalloproteinase-2 (MMP-2), and B-cell lymphoma 2 (Bcl-2) are significantly stimulated in HCV-infected patients. We further show that HCV activates STAT3, MMP-2, Bcl-2, extracellular regulated protein kinase (ERK), and c-Jun N-terminal kinase (JNK) in infected Huh7.5.1 cells. Functional screening of HCV proteins revealed that nonstructural protein 4B (NS4B) is responsible for the activation of MMP-2 and Bcl-2 by stimulating STAT3 through repression of the suppressor of cytokine signaling 3 (SOCS3). Our results also demonstrate that multiple signaling cascades, including several members of the protein kinase C (PKC) family, JNK, ERK, and STAT3, play critical roles in the activation of MMP-2 and Bcl-2 mediated by NS4B. Further studies revealed that the C-terminal domain (CTD) of NS4B is sufficient for the activation of STAT3, JNK, ERK, MMP-2, and Bcl-2. We also show that amino acids 227 to 250 of NS4B are essential for regulation of STAT3, JNK, ERK, MMP-2, and Bcl-2, and among them, three residues (237L, 239S, and 245L) are crucial for this regulation. Thus, we reveal a novel mechanism underlying HCV pathogenesis in which multiple intracellular signaling cascades are cooperatively involved in the activation of two important cellular factors, MMP-2 and Bcl-2, in response to HCV infection.

Dental functional status with and without tooth replacement in a Chinese adult population.

Abstract: The objective of this study is to investigate the prevalence of missing teeth and prosthodontic replacements in a Chinese adult population using a hierarchical dental functional classification system. A total of 1,462 dentate subjects over 40 years from Shandong Province, China were included and categorized in the functional classification system with and without tooth replacements. Depending on replacements, subjects could be reclassified (promoted) to categories reflecting higher functionality. “Promotions” were considered indicators for prosthodontic effectiveness. Homogeneities after dichotomization into functional categories appeared to be moderate to good. In the “≥10 teeth in each jaw” branch, mean number of teeth and posterior occluding pairs were 27.93 ± 2.74 and 7.10 ± 1.94, respectively. In the branch “<10 teeth in each jaw,” these figures were 16.17 ± 5.54 and 1.49 ± 1.45. Fixed dental prostheses (FDPs) added on average 3.5 artificial teeth; 46% of subjects with FDP promoted to a higher functional level. For removable dental prostheses (RDPs), these numbers were 8.5% and 79%, respectively. Promotion value per tooth added was significantly higher for FDPs. The classification system was able to quantify the effectiveness of teeth replacements. It was shown that RDPs were more effective when higher numbers of teeth were replaced, while FDPs were more effective per artificial tooth added.

Does Light Heterogeneity Affect Structure and Biomass of Submerged Macrophyte Communities

Abstract: Environmental heterogeneity is universal and occurs at various spatial scales. Many studies have examined effects of environmental heterogeneity on growth of individual species, but few have tested the effects on species composition and biomass of plant communities, especially those consisting of submerged macrophytes. Moreover, no study has tested effects of scale of heterogeneity on plant communities. We constructed communities with four submerged macrophytes (i.e., Ceratophyllum demersum, Hydrilla verticillata, Egeria densa and Myriophyllum verticillatum) and subjected the communities to three homogeneous light treatments (100%, 65% and 30% of full light and coded as high, medium and low light treatment, respectively) and two heterogeneous light treatments differing in patch size (large vs. small patch treatment). The total amount of light received by the whole communities in the two patchy treatments was the same as that in the homogeneous medium light treatment. Under homogeneous treatments, decreasing light intensity significantly decreased total biomass, total number of nodes and total shoot length of the submerged macrophyte communities and of H. verticillata and E. densa, but did not significantly affect growth of M. verticillatum or C. demersum. Light heterogeneity, i.e., light patchiness or patch scale, did not affect these three growth variables of the community as well as those of the individual macrophytes. Therefore, light intensity can affect structure and biomass of submerged macrophyte communities, but light heterogeneity may not.

Research Article Overexpression of OsPAP10a, A Root-Associated Acid Phosphatase, Increased Extracellular Organic Phosphorus Utilization in Rice

Abstract: Phosphorus (P) deficiency is a major limitation for plant growth and development. Among the wide set of responses to cope with low soil P, plants increase their level of intracellular and secreted acid phosphatases (APases), which helps to catalyze inorganic phosphate (Pi) hydrolysis from organo- phosphates. In this study we characterized the rice (Oryza sativa) purple acid phosphatase 10a (OsPAP10a). OsPAP10a belongs to group Ia of purple acid phosphatases (PAPs), and clusters with the principal secreted PAPs in a variety of plant species including Arabidopsis. The transcript abundance of OsPAP10a is specifically induced by Pi deficiency and is controlled by OsPHR2, the central transcription factor controlling Pi homeostasis. In gel activity assays of root and shoot protein extracts, it was revealed that OsPAP10a is a major acid phosphatase isoform induced by Pi starvation. Constitutive overexpression of OsPAP10a results in a significant increase of phosphatase activity in both shoot and root protein extracts. In vivo root 5-bromo-4-chloro-3-indolyl-phosphate (BCIP) assays and activity measurements on external media showed that OsPAP10a is a root-associated APase. Furthermore, overexpression of OsPAP10a significantly improved ATP hydrolysis and utilization compared with wild type plants. These results indicate that OsPAP10a can potentially be used for crop breeding to improve the efficiency of P use.

Patchy distributions of Spirogyra arcta do not affect growth of the submerged macrophyte Ceratophyllum demersum

Abstract: Spatial heterogeneity is common in aquatic conditions, but few studies have examined the effects of heterogeneous distributions of biological factors on aquatic plants. Spirogyra (Spirogyra arcta) coexists with many submerged macrophytes, such as Ceratophyllum demersum, but no study has examined the effects of heterogeneous distributions of spirogyra on the growth of submerged plants. We grew the submerged plant C. demersum in three homogeneous, aquatic conditions (0, 50 and 100% of the water surface in the container was evenly covered by spirogyra, referred to as ‘control’, ‘50%’ and ‘100%’, respectively) and two patchy conditions (the left half of the water surface in the container was not covered by spirogyra and 50% and 100% of the water surface in the right half of the container was evenly covered by spirogyra, referred to as ‘50%-patchy’ and ‘100%-patchy’, respectively). Compared with the control, the 100% treatment greatly decreased the biomass and number of ramets of C. demersum, but the 50% treatment did not. Growth of C. demersum in the left half of the container did not differ significantly between the control and the two heterogeneous treatments (50%-patchy and 100%-patchy). In addition, growth of C. demersum in the right half of the container did not differ between the 100% and the 100%-patchy treatment or between the 50% and the 50%-patchy treatment. Our results suggest that C. demersum can tolerate shading by spirogyra to a certain extent and that heterogeneous distributions of spirogyra do not affect its growth.

Enhancement of Thermoelectric Figure-of-Merit by Resonant States of Aluminum Doping in Lead Selenide

Abstract: By adding aluminium (Al) into lead selenide (PbSe), we successfully prepared n-type PbSe thermoelectric materials with a figure-of-merit (ZT) of 1.3 at 850 K. Such a high ZT is achieved by a combination of high Seebeck coefficient caused by very possibly the resonant states in the conduction band created by Al dopant and low thermal conductivity from nanosized phonon scattering centers.

Analysis of promoter activity of PtDrl02 gene in white poplars

Abstract: To determine the transcriptional activity of the promoter of Populus TIR (Toll/interleukin-1 receptor domain)-encoding PtDrl02 gene in perennial plants, β-glucuronidase (GUS) gene expression driven by PtDrl02 promoter was analyzed in white poplars. Agrobacterium-mediated transient expression assays indicated that the PtDrl02 promoter was able to direct the GUS reporter gene transcription in stem tissues of both triploid [(Populus tomentosa × P. bolleana) × P. tomentosa, clone ‘L9’] and diploid (P. tomentosa cv. 1521) white poplars, and that the transcript levels seemed to be comparable to each other. In stably transformed P. tomentosa plants, the PtDrl02 promoter directed-gene (GUS) expression behaved in an aerial-specific manner but with a relatively low level in tissues compared to that of the ACTIN reference. Further investigation revealed that the PtDrl02 promoter activity could be induced by wounding, methyl jasmonate (MeJA), salicylic acid (SA), abscisic acid (ABA), or high salinity (NaCl) in transgenic P. tomentosa but with a time-course manner. Intriguingly, dynamic expression of the GUS reporter gene driven by PtDrl02 promoter, over given time periods, appeared to be similar to that of the native pathogenesis-related (PR) protein gene (PtPR-1, PtPR-5, or PtPR-10) in transgenic P. tomentosa plants when exposed to the same inducers. Here it was also evidenced that the PtWRYK1 transcription factor conferred a negative effect on PtDrl02 promoter functions in white poplars. Our work provided new information on PtDrl02 promoter activity in poplars, which could be helpful to increase our understanding of the transcription regulation of the Populus TIR-encoding gene by its promoter.

Effects of Brucella phosphoglucomutase on inducing infection of trophoblastic cells

Abstract: OBJECTIVE: We studied the biological function of Brucella phosphoglucomutase (pgm) gene, and detected the changes of human trophoblast cell invaded by the Brucella pgm mutant and PGM protein. METHODS: Human trophoblast cells were infected by the pgm mutant and PGM protein. The changes of cytokines were detected by enzyme-linked immunosorbent assay, and morphology of cells was identified. RESULTS: PGM protein was purified, and pgm mutant was constructed. The sera of mice immunized by pgm mutant were negative by agglutination test and Standard Tube Agglutination Test for Brucellosis. The cellular morphology of human trophoblast cells infected pgm mutant or PGM protein changed. The adhesion and infection of the pgm mutant reduced more than Brucella vaccine strain M5-90, and human trophoblast cells partially cracked off. The activity of IL-6, TNF-alpha or lactic dehydrogenae increased in human trophoblast cells infected by the pgm mutant more than Brucella vaccine strain M5-90 (P < 0.01), but not for IL-10. Lactic dehydrogenae in human trophoblast cells infected by the PGM Protein increased more than sodium phosphate buffer (P < 0.01), whereas IL-6 and TNF-alpha decreased in human trophoblast cells less than sodium phosphate buffer (P < 0.05). CONCLUSION: The results suggest that the pgm mutant of brucella and PGM protein had the cytotoxic effect for human trophoblast cells with cellular morphology and changes of cytokines.

Landscape Spatial Pattern Analysis for a Traditional Agricultural Landscape of Hani Terrace in Southwestern China

Abstract: The agriculture landscape of the Hani terrace is a representative case of a harmonious blend of the relationships between nature and human culture. With land use and land cover, Landsat TM image and DEM data, the Hani terrace agriculture landscape ecological classification and mapping were carried out using GIS and remote sensing techniques. Based on the analysis of the terrace agricultural landscape spatial patterns with natural, the research mainly showed that the landscape types of "terrace" and "forest" are the dominant elements, the landscape spatial pattern of the Hani terrace agriculture landscape in Yuanyang county not only shows a relative ecological stability with high landscape diversity, but shows an obvious "higher forest - middle village - lower terrace - lowest river" vertical pattern with rather steep slope, especially for quite a few paddy field and dry land whose distribution are in the elevation of 1500~2000 m and on the slope of inconceivably more than 30 °.

Studies on the Bi[subscript 2]Te[subscript 3]–Bi[subscript 2]Se[subscript 3]–Bi[subscript 2]S[subscript 3] system for mid-temperature thermoelectric energy conversion

Abstract: United States. Dept. of Energy. Office of Basic Energy Sciences (Solid-State Solar-Thermal Energy Conversion Center Award DE-SC0001299/DE-FG02-09ER46577)