Biomedical subjects

Xiaoping Jia

Publications and source records attributed to Xiaoping Jia.

3 recordsLinked to original sources

PubMed2006

[Mass-balance ecopath model of Belbu Gulf ecosystem].

Based on the investigation of fishery resources and eco-environment in the Beibu Gulf of northern South China Sea from October 1997 to May 1999, and with EwE software, a mass-balance ecopath model of Beibu Gulf ecosystem was constructed, which consisted of 16 functional groups (boxes) including marine mammals and seabirds, each representing the organisms with similar roles in the food web, and covered the main trophic flow in Beibu Gulf ecosystem. The food web in Beibu Gulf ecosystem was dominated by detrital path, and benthic invertebrate played a significant role in transferring energy from detritus to higher trophic levels. Phytoplankton was the primary producer, and the fractional trophic levels ranged from 1.00 to 4.04, with marine mammals occupying the highest trophic level. By using network analysis, the system network was mapped into a linear food chain, and six discrete trophic levels were found, with a mean transfer efficiency of 12.3% from detritus, and 12.2% from primary producer within the ecosystem. The biomass density of commercially utilized species estimated by the model was 8.7 t x km(-2), and the bioproduction only accounted for 1.81% of the net primary production, which indicated that the system was still in developing status and instable.

Animals↗

PubMed2005

Nonlinear dynamics, granular media and dynamic earthquake triggering.

The 1992 magnitude 7.3 Landers earthquake triggered an exceptional number of additional earthquakes within California and as far north as Yellowstone and Montana. Since this observation, other large earthquakes have been shown to induce dynamic triggering at remote distances--for example, after the 1999 magnitude 7.1 Hector Mine and the 2002 magnitude 7.9 Denali earthquakes--and in the near-field as aftershocks. The physical origin of dynamic triggering, however, remains one of the least understood aspects of earthquake nucleation. The dynamic strain amplitudes from a large earthquake are exceedingly small once the waves have propagated more than several fault radii. For example, a strain wave amplitude of 10(-6) and wavelength 1 m corresponds to a displacement amplitude of about 10(-7) m. Here we show that the dynamic, elastic-nonlinear behaviour of fault gouge perturbed by a seismic wave may trigger earthquakes, even with such small strains. We base our hypothesis on recent laboratory dynamic experiments conducted in granular media, a fault gouge surrogate. From these we infer that, if the fault is weak, seismic waves cause the fault core modulus to decrease abruptly and weaken further. If the fault is already near failure, this process could therefore induce fault slip.

Journal Article↗

PubMed2004

[Ecological characteristics of phytoplankton in coastal area of Pearl River estuary].

Five cruises of phytoplankton survey were made in costal area of Pearl River estuary in 1998-1999. The results showed that 239 species were identified, 72.4% of which belonging to Bacillariophyta, 23.8% to Pyrrophyta, and 3.8% to others. The dominant species were warm and eurythermic species Thalassiothrix frauenfeldii, Nitzschia delicatissima, Thalassiothrix frauenfeldii and Thalassiosira subtilis, and changed with an obvious seasonal succession. The cell density ranged from 0.2 x 10(4) to 2,767.1 x 10(4) cell x m(-3), with an average of 98.7 x 10(4) cell x m(-3), and the mean cell density was obviously higher in summer and winter than in spring and autumn. The regional variation revealed that the cell density in shore area was visibly higher than that in offshore area, and the largest density area was at the southeast of Shangchuan Island all the year around. The range of mean Shannon-Wiener index, Pielou evenness index and biodiversity threshold was 2.63-3.17, 0.53-0.71 and 1.74-2.23, respectively. According to the diversity index, it was concluded that the diversity level of phytoplankton community in coastal area of Pearl River estuary was relatively high and stable.

Biodiversity↗