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Search Results: 1 - 10 of 610587 matches for " F-M Li "
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Effects of limited irrigation on yield and water use efficiency of two sequence-replaced winter wheat in Loess Plateau, China
L Liu, B-C Xu, F-M Li
African Journal of Biotechnology , 2007,
Abstract: The effects of irrigation on grain yield and water use efficiency was studied on two sequence replaced dryland winter wheat (Triticum aestivum L.) cultivars, Changwu 135 (CW, a new cultivar) and Pingliang 40 (PL, an old cultivar). Field experiments were carried out on Changwu country on Loess Plateau, China. Whereas the control plots were not irrigated at all, the treatment plots were irrigated three times, the quantity of irrigation being the same (40 mm) each time: at the jointing stage, at booting, and at flowering. Irrigation increased root biomass in each layer of soil in PL. Irrigation made PL produce greater root biomass in deeper soil, enabling the plants to tap larger quantities of water. CW had a harvest index (HI) greater by 0.11 than that of PL under both conditions, and lower shoot and root biomass, which indicates that more dry matter was transported to productive organs, leading to higher yields than PL. CW consumed more water to produce a unit quantity of root biomass and use irrigation less efficiently showing undercompensation, whereas PL showed overcompensation. Higher yield and greater water use efficiency in wheat appear to be associated with smaller root systems and higher harvest index irrespective of irrigation.
纤维化肝窦内皮细胞中基因表达的研究
陈 宏?,Stolz F-M,Dargel R?
西北农林科技大学学报(自然科学版) , 2000,
Abstract: 按照肝脏受taa损伤的程度把试验动物wistar大白鼠分为两组(taa-1和taa-2)。northern杂交分析表明,在taa-1的窦内皮细胞中,bcl-x和bax基因的表达水平轻微降低;随着肝损伤的增加,表达水平再度下降。核run-off转录分析表明,两组的窦内皮细胞、总的rna合成率下降约30%(p<0.001);taa-1、bad、bax和cycline的mrna合成有所降低,而cyclina的mrna合成则明显增加;taa-2、bad、bax和bcl-2的mrna合成增加了2~3倍,bcl-x的mrna合成增加了7倍多。
Plasmonic enhancement of fluorescence and Raman scattering by metal nanotips
N. I. Cade,F. Culfaz,L. Eligal,T. Ritman-Meer,F-M. Huang,F. Festy,D. Richards
Physics , 2008,
Abstract: We report modifications to the optical properties of fluorophores in the vicinity of noble metal nanotips. The fluorescence from small clusters of quantum dots has been imaged using an apertureless scanning near-field optical microscope. When a sharp gold tip is brought close to the sample surface, a strong distance-dependent enhancement of the quantum dot fluorescence is observed, leading to a simultaneous increase in optical resolution. These results are consistent with simulations of the electric field and fluorescence enhancement near plasmonic nanostructures. Highly ordered periodic arrays of silver nanotips have been fabricated by nanosphere lithography. Using fluorescence lifetime imaging microscopy, we have created high resolution spatial maps of the lifetime components of vicinal fluorophores; these show an order of magnitude increase in decay rate from a localized volume around the nanotips, resulting in a commensurate enhancement in the fluorescence emission intensity. Spatial maps of the Raman scattering signal from molecules on the nanotips shows an enhancement of more than 5 orders of magnitude.
Complicaciones fetales en las gestaciones gemelares monocoriales biamnióticas: estudio de 94 casos
Sara Arrieta B,María de la Calle F-M,Félix Ome?aca T,Antonio González G
Revista Chilena de Obstetricia y Ginecología , 2012,
Abstract: Antecedentes: El embarazo de gemelos monocoriales tienen un mayor riesgo de mortalidad y morbilidad perinatal, que la gestación única y el embarazo gemelar bicorial. Objetivos: Estudiar la incidencia y el manejo de las complicaciones fetales propias de las gestaciones gemelares monocoriales biamnióticas. Métodos: Se realizó un análisis retrospectivo de 94 embarazos gemelares monocoriales biamnióticos, seguidos en las Consultas de Tocología de Alto Riesgo del Hospital Universitario La Paz de Madrid, entre 2008 y 2010. Resultados: Se recogieron 94 gestaciones monocoriales biamnióticas. Aparecieron complicaciones fetales en el 23,4% de las mismas: síndrome de transfusión feto-fetal en el 9,57% de los casos, retraso del crecimiento intrauterino selectivo en el 11,7 %, muerte fetal intrauterina en el 2,1%, y malformaciones fetales en el 7,4%. Conclusiones: Las gestaciones monocoriales biamnióticas son un tipo de embarazo gemelar de alto riesgo, asociado con más complicaciones fetales y muerte perinatal. Se recomienda un estrecho seguimiento ecográfico cada 2 semanas, desde la semana 16, para diagnosticar y tratar precozmente las complicaciones fetales. Background: The monochorionic twin pregnancy has a higher risk of perinatal mortality and morbidity, than the single gestation and the dichorionic twin gestation. Objectives: To detail the incidence and management of specific fetal complications of monochorionic diamniotic twin pregnancies. Methods: We performed a retrospective analysis of monochorionic diamniotic pregnancies followed in the High Risk Obstetrics Unit of the University Hospital La Paz, Madrid, between 2008-2010. Results: We collected 94 monochorionic diamniotic pregnancies. Fetal complications occurred in 23.4% of them: feto-fetal transfusion syndrome in 9.57% of cases, selective intrauterine growth retardation in 11.7%, stillbirth in 2.1%, and fetal malformations in 7.4%. Conclusions: Monochorionic diamniotic twin pregnancies are a high-risk type of twin pregnancy, associated with an increased risk of death and perinatal complications. Ultrasound monitoring is recommended for uncomplicated monochorionic pregnancies every 2 weeks from week 16, to detect and treat fetal complications.
Study of the TEC data obtained from the DORIS stations in relation to seismic activity
F. Li,M. Parrot
Annals of Geophysics , 2007, DOI: 10.4401/ag-3086
Abstract: Ionospheric data obtained from the DORIS system are used in this paper. The DORIS system is composed of several ground-based beacons which emit at two frequencies (400 MHz and 2 GHz) and of receivers on board several satellites (currently SPOT2, SPOT4, SPOT5, Topex-Poseidon, Jason1 and Envisat). Thanks to the density of its network coverage (?50 stations), DORIS provides information on the ionosphere. The TEC (Total Electron Content) parameter which is the electron density integrated over the vertical could be obtained from DORIS measurements. In a first step, the paper describes the way to obtain the TEC data from the DORIS ionospheric measurements, and comparisons of the results are done with the IRI2001 model. In a second step, TEC values are used to search for correlation between ionospheric perturbations and seismic activity. Earthquakes of magnitude larger than 5 are chosen close to the ground-based DORIS stations. Among other results, the statistics show that, during the night time and at geomagnetic latitude close to the equator (<10°), TEC amplitude fluctuates at the time of the earthquakes as it is expected, but also 2 days and 5 days before.
Tunable optical Aharonov-Bohm effect in a semiconductor quantum ring
Bin Li,F. M. Peeters
Physics , 2012, DOI: 10.1103/PhysRevB.83.115448
Abstract: By applying an electric field perpendicular to a semiconductor quantum ring we show that it is possible to modify the single particle wave function between quantum dot (QD)-like to ring-like. The constraints on the geometrical parameters of the quantum ring to realize such a transition are derived. With such a perpendicular electric field we are able to tune the Aharanov-Bohm (AB) effect for both single particles and for excitons. The tunability is in both the strength of the AB-effect as well as in its periodicity. We also investigate the strain induce potential inside the self assembled quantum ring and the effect of the strain on the AB effect.
Controllable spin singlet - spin triplet transition in three concentric quantum rings through magnetic field and confinement potential
Bin Li,F. M. Peeters
Physics , 2012,
Abstract: We present a theoretical study of the spectrum of electrons confined in triple concentric rings. An unusual ordering and rich variety of angular momentum transitions are found that depend on the coupling between the rings and the confinement potential of the rings. Using the Configuration Interaction (CI) method, we calculated the two electron energy spectrum. Spin singlet to spin triplet transitions of the electron ground state are predicted and a fractional Aharonov-Bohm effect is found. We show that both the period and amplitude of the spin singlet - triplet energy gap depend strongly on the confinement potential and the external magnetic field. The spin singlet - triplet transition is found to depend on the spin Zeeman energy, especially for rings with weak confinement and in the presence of large magnetic field. The amplitude of the spin singlet - triplet energy gap depends on the Land\'{e} $g$-factor but the period of the transitions is independent of $g$.
Quantifying nitrous oxide emissions from Chinese grasslands with a process-based model
F. Zhang,J. Qi,F. M. Li,C. S. Li
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-1675-2010
Abstract: As one of the largest land cover types, grassland can potentially play an important role in the ecosystem services of natural resources in China. Nitrous oxide (N2O) is a major greenhouse gas emitted from grasslands. Current N2O inventory at regional or national level in China relies on the emission factor method, and is based on limited measurements. To improve inventory accuracy and capture the spatial variability of the N2O emissions under the diverse climate, soil and management conditions across China, we adopted an approach that uses a process-based biogeochemical model, DeNitrification-DeComposition (DNDC) in this study, to map the N2O emissions from China's grasslands. The DNDC was linked to a GIS database of spatially distributed information of climate, soil, vegetation and management at county-level for all grasslands in China. Daily weather data from 2000–2007 based on the national network of 670 meteorological stations were utilized in the model simulations. The results were validated against observations from several grasslands in China and from other countries. The modelled results showed a clear geographic pattern of N2O emissions from China's grasslands. A high-emission strip was found that stretched from northeast to central China, along the eastern boundary of the temperate grassland region adjacent to the major agricultural regions. The grasslands in the western mountain regions, however, emitted much less N2O. The regional average of N2O emission rates was 0.23, 0.11 and 0.39 kg N ha 1y 1 for the temperate, montane and tropical/subtropical grasslands, respectively. The national N2O emission was 76.5 Gg N from the 337 million ha of grasslands in China. The modelled results were in good agreement with observations (R2=0.64 for 11 datasets), suggesting that the process-based model can be used to capture the spatial dynamics of N2O emissions as an effective alternative to statistical method currently used in China.
Quantifying nitrous oxide emissions from Chinese grasslands with a process-based model
F. Zhang,J. Qi,F. M. Li,C. S. Li
Biogeosciences (BG) & Discussions (BGD) , 2010, DOI: 10.5194/bg-7-2039-2010
Abstract: As one of the largest land cover types, grassland can potentially play an important role in the ecosystem services of natural resources in China. Nitrous oxide (N2O) is a major greenhouse gas emitted from grasslands. Current N2O inventory at a regional or national level in China relies on the emission factor method, which is based on limited measurements. To improve the accuracy of the inventory by capturing the spatial variability of N2O emissions under the diverse climate, soil and management conditions across China, we adopted an approach by utilizing a process-based biogeochemical model, DeNitrification-DeComposition (DNDC), to quantify N2O emissions from Chinese grasslands. In the present study, DNDC was tested against datasets of N2O fluxes measured at eight grassland sites in China with encouraging results. The validated DNDC was then linked to a GIS database holding spatially differentiated information of climate, soil, vegetation and management at county-level for all the grasslands in the country. Daily weather data for 2000–2007 from 670 meteorological stations across the entire domain were employed to serve the simulations. The modelled results on a national scale showed a clear geographic pattern of N2O emissions. A high-emission strip showed up stretching from northeast to central China, which is consistent with the eastern boundary between the temperate grassland region and the major agricultural regions of China. The grasslands in the western mountain regions, however, emitted much less N2O. The regionally averaged rates of N2O emissions were 0.26, 0.14 and 0.38 kg nitrogen (N) ha 1 y 1 for the temperate, montane and tropical/subtropical grasslands, respectively. The annual mean N2O emission from the total 337 million ha of grasslands in China was 76.5 ± 12.8 Gg N for the simulated years.
A New Method for Riccati Differential Equations Based on Reproducing Kernel and Quasilinearization Methods
F. Z. Geng,X. M. Li
Abstract and Applied Analysis , 2012, DOI: 10.1155/2012/603748
Abstract: We introduce a new method for solving Riccati differential equations, which is based on reproducing kernel method and quasilinearization technique. The quasilinearization technique is used to reduce the Riccati differential equation to a sequence of linear problems. The resulting sets of differential equations are treated by using reproducing kernel method. The solutions of Riccati differential equations obtained using many existing methods give good approximations only in the neighborhood of the initial position. However, the solutions obtained using the present method give good approximations in a larger interval, rather than a local vicinity of the initial position. Numerical results compared with other methods show that the method is simple and effective.
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