Biomedical subjects

Jianmei Liu

Publications and source records attributed to Jianmei Liu.

4 recordsLinked to original sources

PubMed2006

[Application and verification of distributed model in simulating watershed evapotranspiration].

Based on the conventional observed meteorological data during 1989 approximately 2000, a distributed model was employed to simulate the temporal and spatial distribution of the potential and actual evapotranspiration in the upper Zagunao watershed of Sichuan Province. Grids of 500 m and step of 1 d were used to describe the spatial and temporal heterogeneity and variability in the study area. The potential evapotranspiration was simulated by a deformation form of Penman-Monteith Equation, and a method for calculating actual evapotranspiration was proposed, with the underlying conditions considered. The results showed that the relative error of the normal annual evapotranspiration in the 12 years between the simulation and the calculation was 3.47%, with a reasonable temporal and spatial distribution. The research results provided an effective method for the distributed rainfall-runoff model in simulating actual evapotranspiration.

Mathematics↗

PubMed2005

Energy adaptation to glucocorticoid-induced hyperleptinemia in human beings.

Recombinant leptin therapy potently decreases food intake and body weight in aleptinemic individuals with leptin gene mutations. However, it is unknown whether manipulation of endogenous leptin secretion alters ingestive behavior in otherwise healthy subjects. We therefore assessed energy consumption during administration of hydrocortisone (HC), a known leptin secretagogue. Six healthy adults were admitted overnight on 2 occasions and given HC (12.5 mg/h IV) or saline infusion for 24 hours (8:00 am -8:00 am ) in a randomized crossover design. Total energy and macronutrient intake was calculated using a computerized nutrient analysis program. Blood sampling for measurement of leptin, cortisol, glucose, and insulin was performed at baseline and every 1 to 2 hours. A rise in plasma leptin level was noted after approximately 5 hours of HC infusion and was sustained throughout the study period. The total energy consumed was 3004 +/- 231 kcal for saline and 2486 +/- 214 kcal for HC ( P = .005); breakfast energy values on day 1 were similar but energy values consumed at lunch, dinner, and day 2 breakfast were all significantly lower during induced hyperleptinemia. Analysis of macronutrients indicated significant decreases in carbohydrate and fat intake during glucocorticoid-induced hyperleptinemia as compared with placebo. These results indicate that stimulation of native leptin secretion decreases energy consumption, similar to the effect observed with recombinant leptin therapy. To our knowledge, this is the first report documenting anti-ingestive responses to a leptin secretagogue. Because chronic glucocorticoid therapy is fraught with adverse effects, we suggest that nonsteroidal or steroidomimetic leptin secretagogues may be good candidates for anorectic and antiobesity drug development.

Blood Glucose↗

PubMed2005

[Construction and verification of distributed rain-runoff model for forested watershed in alpine and gorge region].

Considering of the main hydrological characteristics in the upper Zagunao River watershed of the upper reach of Minjiang River, general hydrological models were selected to construct the distributed rainfall-runoff process model for the forested watershed in typical alpine and gorge terrains. Calibration of too many regional parameters was avoided to assure the transportability of the models in similar watersheds. Two flow series of 1 000 hours in 1999 and 2000 were simulated by using the distributed model. The runoff hydrograph, accumulative runoff volume, peak discharge, and peak time showed good fittings with observed series. The simple structure and less empirical parameters gave the distributed model the ability to simulate the rainfall-runoff processes in similar watershed across scales, which provided the basic approach to the hydrological scaling research.

Ecosystem↗

PubMed2003

[Research progress on hydrological scaling].

With the development of hydrology and the extending effect of mankind on environment, scale issue has become a great challenge to many hydrologists due to the stochasticism and complexity of hydrological phenomena and natural catchments. More and more concern has been given to the scaling issues to gain a large-scale (or small-scale) hydrological characteristic from a certain known catchments, but hasn't been solved successfully. The first part of this paper introduced some concepts about hydrological scale, scale issue and scaling. The key problem is the spatial heterogeneity of catchments and the temporal and spatial variability of hydrological fluxes. Three approaches to scale were put forward in the third part, which were distributed modeling, fractal theory and statistical self similarity analyses. Existing problems and future research directions were proposed in the last part.

Models, Theoretical↗