Plant-plant interactions vary greatly along a flooding gradient in a dam-induced riparian habitat.

Plant-plant interactions under extreme environmental stress are still controversial. The stress gradient hypothesis (SGH) proposes that facilitation prevails under extreme environmental stresses, while an alternative view states that facilitation collapses or even switches back to competition at the extreme end of stress gradients. However, how the relationship between plant-plant interaction and periodic extreme flooding stress varies and its underlying mechanism are still unclear in a dam-regulated riparian ecosystem. We established a controlled experiment using two dominant species pairs (Cynodon dactylon-Cyperus rotundus and C. dactylon-Xanthium sibiricum) in the water level fluctuating zone of the Three Gorges Dam to examine their growth responses to the periodic extreme flooding stress. The results showed that as flooding stress increased, the competitive effect of C. dactylon on X. sibiricum shifted to facilitation, whereas the effect of X. sibiricum on C. dactylon maintained a strong inhibition. The plant height of X. sibiricum was the most important driver of the interaction between X. sibiricum and C. dactylon along the flooding gradient. The net effect of C. dactylon on C. rotundus shifted from neutral to negative, and the inhibitory effect of C. rotundus on C. dactylon became stronger at the extreme end of flooding stress. The root biomass of the two species was the key trait regulating their interaction with increasing flooding stress. Overall, the SGH was partially supported along our periodic extreme flooding stress gradient. Aboveground resource (light) might be the dominant factor driving the response of the interaction between annual plants and perennial clonal plants to periodic flooding stress, whereas belowground resource (water and nutrients) was probably the dominant factor for perennial clonal plants. Our study will help to further understand the environmental responses of plant-plant relationships and their regulatory mechanism, and the succession of riparian plant communities under extreme environmental changes, providing a basic theoretical basis and data support for the ecological restoration and management of riparian wetland vegetation.

Correlation of caries susceptibility with different means of tooth surface and patients' oral hygiene habits after interproximal enamel reduction in clinical practice / 中华医学美学美容杂志

Objective To explore the correlation of caries susceptibility of patients with the immediate tooth polish,application of fluoride,and the patients' oral hygiene habits after interproximal enamel reduction (IER) in clinical practice.Methods The present study retrospectively collected 45 cases of IER (18 males and 27 females) in 196 tooth sites.Each sample was examined clinically and radiologically to obtain the incidence of caries,and the outcome was correlated with amount of IER,tooth polish,application of fluoride,and the brushing method and frequency for statistical analysis.Results The present study showed that there was no statistical significance among the amount of IER,the site of IER,the patients' brushing method,and the gender with the susceptibility of caries.However,there was statistical significance among the application of fluoride,tooth polish and brushing frequency with the susceptibility of caries.Conclusions The current research suggests that it is desirable to polish tooth and apply fluoride for patients with IER in clinical practices.In the meanwhile,the clinician should pay attention to patients' oral hygiene habits,especially brushing frequency,due to the positive correlation between the brushing frequency and incidence of caries.

Treatment of acute obstructive cased by colorectal cancer / 国际外科学杂志

Objective To investigate the treatment of acute obstructive colorectal cancer.Methods The clinical data of 26 cases with acute obstructive colorectal cancer were analysed retrospectively and relevant literatures were reviewed.Results Radical right hemicolectomy was performed in 9 patients with obstructive right colonic cancer.Among 17 patients with obstructive left colorectal cancer,one-stage radical resection was perfomed in 12 cases,including one-stage anastomosis in 4 cases and Hartmann's operation in 8 cases.Palliative colostomy was performed in 3 cases.Right hemicolectomy and sigmoid colon loop colostomy was performed in 1 case of rectum cancer with ascending colon strangulation.One case refused surgery.Two cases died of MODS and 1 case with inflammatory ileus recovering from conservative treatment after operation.In the course of disease,septic shock and MODS happened in 3 cases,lung infection in 5 cases,heart disease in 2 cases and Hypoalbuminemia in 16 cases.Conclusions One-stage radical colectomy and anastomosis should be performed in patients with obstructive right colonic cancer.In order to reduce toxin absorption and prevent the deterioration of disease,Bowel decompression and removal of inflammatory exudate should be performed in patients with obstructive left colorectal cancer according to the damage control theory.Then effective and safe operation should be chosen in accordance with patients' status.Anti-infection and nutrition support treatment must be strengthened after operation.

The advance of experimental cell division biomechanics / 生物医学工程学杂志

The advance of experimental cell division and proliferation in the field of cell biomechanics is presented in this paper. The emphasis is placed on the research in the mechanics mechanism of cleavage furrow and in the measurement of constricting force about cleavage furrow.

Stability analysis of micropipette aspiration of cell by liquid drop modeling / 生物医学工程学杂志

A generally realized phenomenon in the suction experiment of cells is that if the aspiration pressure is larger than a certain threshold, cell flows continuously into the pipette. The point of the threshold aspiration pressure at which the cell can still be held in a stable equilibrium is called the critical point of aspiration. Here we represent a theoretical analysis of the equilibrium behavior and stability of cell by liquid drop model. In the method of analysis, the areal change due to a small movement deltaL of the portion of the membrane in pipette is given to the first approximation. The threshold pressure and the critical point are shown as simple formulas of the model parameters and inner relative radius of pipette. The results derived from formulas are consistent with rigorous ones by numerical computation in the approximate range.

The biomechanical model of cytokinesis in animal cells / 生物医学工程学杂志

As the basis of cell proliferation, cytokinesis involves the division of the cytoplasm and the plasma membrane into two. In this paper a few models on the active deformation mechanism during cytokinesis process are presented. Discussions are made onvarious models, conclusions, differences between the numerical results and the corresponding experimental results.

Mechanical strain of different waveform and frequency inhibits proliferation of lung adenocarcinoma cell in vitro / 生物医学工程学杂志

The effects of waveform and frequency on proliferation of human lung adenocarcinoma cell line A549 were studied by FX-4000 strain unit . The results showed that cellular proliferation index (PI) reduced significantly in squarewave group when compared with the control after A549 cells were subjected to collagen I 0-25% elongation at frequency 20 cycles/min, 40 cycles/min and 60 cycles/min for 2h. The PI showed no distinct difference in trianglewave group. The PI increased in heartwave group. These data indicate that A549 cells do respond to physiological strain in vitro. The effects of squarewave and 60 cycles/min tension may be optimal for inhibiting the proliferation of A549 cells. To select appropriate waveform and frequency will be of paramount importance to inhibiting proliferation of A549 cells.