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Articles by Li Ma
Total Records ( 4 ) for Li Ma
  Li-Ping Wang , Phillip A. Jackson , Xin Lu , Yuan-Hong Fan , John W. Foreman , Xue-Kuan Chen , Hai-Hua Deng , Cheng Fu , Li Ma and Karen S. Aitken
  Saccharum spontaneum L. has contributed important traits to modern sugarcane (S. spp. L.) cultivars such as adaptation to environmental stress and ratooning ability. There is interest in further use of S. spontaneum in sugarcane improvement for sugar or energy-from-biomass production systems. In this study, parents and progeny from 43 biparental crosses between sugarcane and S. spontaneum clones were evaluated in field trials in China and Australia, along with several commercial cultivars. The S. spontaneum clones were from diverse geographic origins in China. Measurements were made on biomass composition (% dry matter, brix and pol in juice and cane, purity, fiber content) and yield components. Moderate to high (>0.7) broad-sense heritabilities and high genetic variances were observed for most traits. About half the total genetic variance was retained as among-family variance for the biomass composition traits, but this proportion was generally <25% for biomass yields. Midparent values in an independent trial predicted biomass composition traits reasonably well (generally, r > 0.6), but less so for cane and biomass yield (0 < r < 0.4). Genetic correlations between performance of families evaluated in different countries were strong, providing preliminary evidence that results in one country could be used for identifying elite families in the other. Strategies for efficient development and selection of elite clones from S. spontaneum are suggested.
  Xiong Wang , Li Ma and Ze-Xiang Jin
  Fructus Hordei Germinatus (Poaceae, Hordeum) has been traditionally used for treatment of female galactorrhea or Hyperplasia of Mammary Gland (HMG) in China. The overall purpose of this study was to evaluate the Anti-Hyperplasia of Mammary Gland (HMG) effect of Fructus Hordei G Ethanol extract (FHG-E) in HMG rats. Forty virgin female Wistar rats were randomly divided into blank control, HMG Model, Rupisanjie Capsule (RPSJC, positive control) and FHG-E groups, 10 in each. Injection of estrogen and progestogen were given to prepare rat models of HMG, RPSJC and FHG-E were given at the same time. Changes of nipple heights were measured sex hormone levels (E2, P, PRL, FSH and LH) in serum were estimated uterus and ovory index were calculated. Pathologic changes of mammary gland in rats were also observed by microscope. FHG-E could decrease the increased nipple height and uterus index, reduce the numbers of mammary gland lobules and secretion in HMG rats. It could also decrease E2, PRL and FSH levels in serum and increase the serum levels of P and LH significantly compared with the model group. The histopathological observation revealed that FHG-E obviously alleviated the degree of HMG. The contents of total flavonoid total alkaloid and total phenolic contents in the extract were also determined. The results showed that the 50% ethanolic extract from FHE contained total flavonoids 3.95±0.06 mg Quercetin Equivalent (QE)/g extract total alkaloids 42.74±0.08 mg Hordenine Equivalent (HE)/g extract and total phenolics 52.46±0.12 mg Gallic Acid Equivalent (GAE)/g extract. These results suggest FHG-E has therapeutic effects on HMG rats induced by estrogen and progestogen.
  Guanwei Luo , Xiaohong Lv and Li Ma
  An impact oscillator with a frictional slider is considered. The basic function of the investigated system is to overcome the frictional force and move downwards. Based on the analysis of the oscillatory and progressive motions of the system, we introduce an impact Poincaré map with dynamical variables defined at the impact instants. The nonlinear dynamics of the impact system with a frictional slider is analyzed by using the impact Poincaré map. The stability and bifurcations of single-impact periodic motions are analyzed, and some information about the existence of other types of periodic-impact motions is provided. Since the system equilibrium is moving downwards, one way to monitor the progression rate is to calculate its progression in a finite time. The simulation results show that in a finite time, the largest progression of the system is found to occur for period-1 multi-impact motions existing in the regions of low forcing frequencies. Secondly, the progression of the period-1 single-impact motion with peak-impact velocity is also distinct enough. However, it is important to note, that the largest progression for period-1 multi-impact motion existing at a low forcing frequency is not an optimal choice for practical engineering applications. The greater the number of the impacts in an excitation period, the more distinct the adverse effects such as high noise levels and wear and tear caused by impacts. As a result, the progression of the period-1 single-impact motion with the peak-impact velocity is still optimal for practical applications. The influence of parameter variations on the oscillatory and progressive motions of the impact-progressive system are elucidated accordingly, and feasible parameter regions are provided.
  Guanwei Luo , Li Ma and Xiaohong Lv
  A two-degree-of-freedom impact oscillator is considered. The maximum displacement of one of the masses is limited to a threshold value by the symmetrical rigid stops. Impacts between the mass and the stops are described by an instantaneous coefficient of restitution. Dynamics of the system is studied with special attention to periodic-impact motions and bifurcations. Period-one double-impact symmetrical motion and transcendental impact Poincaré map of the system is derived analytically. Stability and local bifurcations of the period-one double-impact symmetrical motions are analyzed by using the impact Poincaré map. The Lyapunov exponents in the vibratory system with impacts are calculated by using the transcendental impact map. The influence of the clearance and excitation frequency on symmetrical double-impact periodic motion and bifurcations is analyzed. A series of other periodic-impact motions are found and the corresponding bifurcations are analyzed. For smaller values of clearance, period-one double-impact symmetrical motion usually undergoes pitchfork bifurcation with decrease in the forcing frequency. For large values of the clearance, period-one double-impact symmetrical motion undergoes Neimark–Sacker bifurcation with decrease in the forcing frequency. The chattering-impact vibration and the sticking phenomena are found to occur in the region of low forcing frequency, which enlarges the adverse effects such as high noise levels, wear and tear and so on. These imply that the dynamic behavior of this system is very rich and complex, varying from different types of periodic motions to chaos, even chattering-impacting vibration and sticking. Chaotic-impact motions are suppressed to minimize the adverse effects by using external driving force, delay feedback and feedback-based method of period pulse.
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