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Search Results: 1 - 10 of 84949 matches for " YU Ding-Fang "
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Physics Related with Co-moving Coordinate System
Ding-fang Zeng
Physics , 2005,
Abstract: We derive the metric of an expanding universe with zero accelerations by pure kinematic method. By doing so we expatiate physics related with co-moving coordinate system in details. The most important discovery or our study is, in an expanding universe with zero accelerations, the red-shift of photons from distance galaxies is determined by the co-moving coordinate of the source galaxy instead of the scale factor's time dependence. Our discovery is consistent with the current observed super-novaes's luminosity-distance v.s. red-shift relations.
Emergent time axis from statistic/gravity dualities
Ding-Fang Zeng
Physics , 2014,
Abstract: We discuss a very naive but natural idea that time emerges as the holographic dimension of gauge systems in euclidean space, which take statistic, e.g. Ising model as concrete implementations. By identifying the renormalization group flow of statistic models with the time flow of dual gravities, we get a universe whose evolution history is qualitatively the same as our real world. We comment highlights projected by this idea on the cosmological constant problem and develop preliminary evidences for the validity of this idea.
A Semi-analytical Solution to Classic Yang-Mills Equations with Both Asymptotical Freedom and Confining Features
Ding-fang Zeng
Physics , 2011,
Abstract: It is well known that confinings and asymptotic freedom are properties of quantum chromo-dynamics (QCD). But hints of these features can also be observed at purely classic levels. For this purpose we need to find solutions to the colorly-sourceful Yang-Mills equations with both confining and asymptotic freedom features. We provide such a solution in this paper which at the near-source region is of serial form, while at the far-away region is approximately expressed through simple elementary functions. From the solution, we derive out a classically non-perturbative beta function describing the running of effective coupling constant, which is linear in the couplings both in the infrared and ultraviolet region.
Protecting effect of Cistanche extracts on MPP+-induced injury of the Parkinson's disease cell model
Hu WANG,Ding-fang CAI
Zhong Xi Yi Jie He Xue Bao , 2007,
Abstract: Objective: To investigate the potential protective role of Cistanche extracts on 1-methyl-4-phenylpyridinium ion (MPP+)-induced Parkinson's disease (PD) cellular model, and to find out whether this effect is achieved through the regulation of growth arrest- and DNA damage-induced gene 153 (GADD153).Methods: MPP+-induced cellular injury and the protective effect of Cistanche extracts on the SH-SY5Y cell line viability treated by MPP+ were investigated by using methyl thiazolyl tetrazolium (MTT) assay. The mRNA of GADD153 in SH-SY5Y cell line treated by MPP+ and Cistanche extracts were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). The protein level of GADD153 in SH-SY5Y was assessed by Western blotting.Results: Cistanche extracts (100 μg/ml) increased the cell viability (P<0.01). And the mRNA of GADD153 in the Cistanche extracts pretreatment group was much less than that in the MPP+ group (P<0.01). The result of Western blotting showed that GADD153 had a lower level in the Cistanche extracts pretreatment group, compared with MPP+ group, especially in the 100 μg/ml group (P<0.01).Conclusion: Cistanche extracts pretreatment has a protective effect on the MPP+-treated SH-SY5Y cell line, and its down-regulation of GADD153 may contribute to the effect.
Baryon Asymmetries in the Natural Inflation Model
Nan Li,Ding-fang Zeng
Physics , 2014, DOI: 10.1103/PhysRevD.90.123542
Abstract: A variation of Affleck-Dine mechanism was proposed to generate the observed baryon asymmetry in [1], in which the inflaton was assumed to be a complex scalar field with a weakly broken $U(1)$ symmetry, and the baryon asymmetry generation was easily unified with the stage of inflation and reheating. We adapt this mechanism to natural inflation scenarios and compare the results with those in chaotic inflation models. We compute the net particle number obtained at the end of inflation and transform it into net baryon number after reheatings. We observed that in natural inflation models, the desired baryon-to-photon ratio can be achieved equally well as in chaotic models.
Effects of conservation tillage and grass-hedge on soil, water, nitrogen and phosphorus loss in sloping cropland

XIAO Bo,YU Ding-Fang,ZHAO Mei,WANG Qing-Hai,SHEN Xiao-Bo,
肖 波
,喻定芳,赵 梅,王庆海,申小波

中国生态农业学报 , 2013,
Abstract: Soil and water loss in sloping croplands has been a major environmental problem across the globe. It has been reported that 28% of soil loss was from sloping croplands that account for only 7% of cultivated land areas. In other words, sloping croplands have been the primary source of runoff and sediment. It is therefore urgent to develop strategies for controlling soil and water loss on sloping croplands across the globe. Although various soil protection techniques (e.g., terrace and contour tillage) have been used in sloping croplands in recent years, the effects of these techniques on soil and water loss remained limited. Conservation tillage with grass-hedge has been effective in reducing soil and water loss in sloping croplands especially in tropical and subtropical regions. These techniques have, however, not been adequately evaluated in North China, thus, which has led to limited adoption by local farmers in this region. In this study, the effects of conservation tillage with grass-hedge on soil, water, nitrogen and phosphorus loss were evaluated under simulated rainfall (rainfall intensity of 60 mm·h-1) from farmland on slopes with 5%, 10%, 15% and 20% gradients in the Changping District of Beijing, China. The results showed that conservation tillage with grass-hedge significantly limited soil, water, nitrogen and phosphorus loss and in the order as follows: conservation tillage with grass-hedge > conventional tillage with grass-hedge > conservation tillage without grass-hedge > conventional tillage without grass-hedge. Runoff under conventional tillage with grass-hedge, conservation tillage without grass-hedge, and conservation tillage with grass-hedge decreased by 56%, 44% and 68%, respectively, compared with conventional tillage without grass-hedge. Correspondingly, soil loss decreased by 66%, 49% and 82%; total nitrogen loss dropped by 56%, 43% and 66%; and total phosphorus decreased by 54%, 40% and 70%, respectively. These results suggested that the integration of conservation tillage and grass-hedge was more effective than sole application of either conservation tillage or grass-hedges in terms of soil, water and nutrient loss control. The results further showed that the effectiveness of conservation tillage and grass-hedge gradually decreased with increasing slope gradient. Although the results suggested that both conservation tillage and grass-hedge significantly limited soil and water loss, their effectiveness was limited under steep slope conditions. Some other engineering techniques (e.g., micro-basin, fish-scale pit, mulch or even landscape shaping) therefore needed to be used in combination in order to prevent soil and water loss under steep slope and intense rain conditions. It was, however, concluded that conservation tillage and grass-hedge were critical for controlled soil, water, nitrogen and phosphorus loss in sloping croplands. These finding was useful in the remediation of soil and water loss in sloping croplands in no
An Ignored Assumption of $Λ$CDM Cosmology and An Old Question: Do We Live On The "Center" of The Universe?
Ding-fang Zeng,Yi-hong Gao
Physics , 2005,
Abstract: We point out that $\Lambda$CDM cosmology has an ignored assumption. That is, the $\Lambda$ component of the universe moves synchronously with ordinary matters on Hubble scales. If cosmological constant is vacuum energy, this assumption may be very difficult to be understood. We then propose a new mechanism which can explain the accelerating recession of super-novaes. That is, considering the pressures originating from the random moving (including Hubble recession) of galaxy clusters and galaxies. We provide an new analytical solution of Einstein equation which may describe a universe whose pressures originating from the random moving of galaxy clusters and galaxies are considered.
Does Standard Cosmology Express Cosmological Principle Faithfully?
Ding-fang Zeng,Hai-jun Zhao
Physics , 2005,
Abstract: In 1+1 dimensional case, Einstein equation cannot give us any information on the evolution of the universe because the Einstein tensor of the system is identically zero. We study such a 1+1 dimensional cosmology and find the metric of it according to cosmological principle and special relativity, but the results contradict the usual expression of cosmological principle of standard cosmology. So we doubt in 1+3 dimensional case, cosmological principle is expressed faithfully by standard cosmology.
A Question About Standard Cosmology and Extremely Dense Stars' Collapsing
Ding-fang Zeng,Yi-hong Gao
Physics , 2005,
Abstract: We ask if the conventional variable separation techniques in the studying of standard cosmology and the collapsing of extremely dense stars introduce Newton's absolute space-time concepts. If this is the case, then a completely relative cosmology is needed. We build the basic frame-works for such a cosmology and illustrate that, the observed luminosity-distance v.s. red-shift relations of supernovaes can be explained naturally even without any conception of dark energies.
Primordial Power Spectrum's Calculation and the Upper Bound on the Number of E-foldings of Inflation
Ding-fang Zeng,Yi-hong Gao
Physics , 2004,
Abstract: In numerical calculations of the primordial power spectrum of perturbations produced during inflation, for very little wavenumber $k$s, to implement the initial conditions required of the perturbation mode functions consistently, we must let the universe experience more e-foldings of inflation than that required of it to solve the horizon, flatness and other pre-inflation problems. However, if the number of e-foldings of inflation has an upper bound, then for perturbations at scales greater than some critical value, the initial conditions required of the mode functions cannot be implemented physically. Because at the inflation beginning point, these perturbation modes lie outside the horizon. We propose that such perturbations do not contribute to the Cosmological Microwave Background Anisotropy (CMBA). Under this proposition, the exceptional lowness of the observed little $l$ muli-poles of CMBA is reproduced numerically. In Linde's $\phi^2$ model, the upper bound on the number of e-foldings of inflation is determined to be 65 approximately.
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