二维无摩擦颗粒体系中阻塞态的压缩过程

数值模拟无摩擦圆盘形颗粒体系的压缩过程,对单分散、双分散、线性作用、赫兹作用等进行对比.数值模拟表明:单分散体系容易晶格化,其临界填充率φC与临界平均接触数ZC都大于双分散的情形.以临界阻塞态为基准,阻塞态在压缩过程中的平均接触数增量ΔZ以及平均重叠量δ随填充率增量Δφ的变化与模拟条件几乎无关,压强P与Δφ的关系决定于作用力的形式,它们都能用幂律关系进行很好的拟合.

摩擦对二维颗粒体系中临界阻塞态的影响

采用离散元法(discrete element method,DEM)对双分散圆盘颗粒体系在均匀压缩过程中的阻塞转变进行数值模拟,讨论了摩擦对临界阻塞态的影响。随着摩擦系数的增大,临界阻塞态的体积分数与平均接触数减小,其力学平均接触数与几何平均接触数的差异增大,同时各种接触类型的百分比也在发生改变。模拟结果还表明,摩擦系数为零以及无穷大的临界阻塞态是等静态堆积,临界阻塞态的体积分数随力学平均接触数呈线性增长的关系。

各向同性压缩过程中圆盘体系的基本性质

结合理论分析与数值模拟研究仅有线性排斥力的二维无序圆盘体系在准静态各向同性压缩过程中的基本性质.引入平均约化重叠量、约化压强等概念,基于微观的力学分析,导出约化压强与体系的组成成分、几何统计量及形变统计量之间的关系.基于数值模拟结果,讨论平均接触数增量、各种接触类型的百分比、平均约化重叠量、约化压强等物理量在大范围压缩的过程中随体积分数增量的变化,给出一个形式简洁的近似约化压强公式.模拟结果表明圆盘体系在远离临界阻塞态及接近临界阻塞态时的压缩响应不同.

A priority-based dynamic load transfer algorithm for cellular/WLAN integrated networks

For the integration network of a cellular network and a wireless local area network （WLAN）, a priority-based dynamic load transfer （PDLT） algorithm is proposed. The dynamic vertical handoffs by call admission control are jointly determined by the network conditions and the traffic characteristics in combination with the location-condition of mobile terminals. When there is no bandwidth resource available in the cellular network or WLAN, the proposed PDLT algorithm allows an incoming voice call or data call within the overlapping area of the cellular network and the WLAN to be directed to the spare network; meanwhile, by dynamically computing the occupancy of the bandwidth resource, the proposed PDLT algorithm also allows an ongoing voice call or data communication to be transferred to the network with a sufficient bandwidth resource according to the given threshold to balance the number of voice/data calls in the two networks. The analysis results of a two-dimensional Markov model and the simulation results show that the PDLT algorithm can effectively enhance the whole integrated network＇ s traffic, reduce the blocking probability of new calls and increase the data throughput, and thus decrease the response time for various services.

Mechanism of benign biliary stricture: A morphological and immunohistochemical study

AIM: To explore the mechanism of benign biliary stricture. METHODS: A model of trauma of bile duct was established in 28 dogs. The anastomosed tissues were resected and examined by light and electron microscopes on day 3, in wk 1, 3 and mo 3, 6 after operation. CD68, TGF-β1 and α-SMA were examined by immunohistochemical staining, respectively. RESULTS: The mucosal epithelium of the bile duct was slowly recovered, chronic inflammation lasted for a long time, fibroblasts proliferated actively, extracellular matrix was over-deposited. Myofibroblasts functioned actively and lasted through the whole process. The expression of macrophages in lamina propria under mucosa, TGF-β1 in granulation tissue, fibroblasts and endothelial cells of blood vessels, oc-SMA in myofiroblasts were rather strong from the 1st wk to the 6th mo after operation. CONCLUSION: The type of healing occurring in bile duct belongs to overhealing. Myofibroblasts are the main cause for scar contracture and stricture of bile duct. High expressions of CD68, TGF-β1 and a-SMA are closely related to the active proliferation of fibroblasts, extracellular matrix over-deposition and scar contracture of bile duct.

Functional and morphological changes of the gut barrier during the restitution process after hemorrhagic shock

AIM： To investigate the functional, morphological changes of the gut barrier during the restitution process after hemorrhagic shock, and the regional differences of the large intestine and small intestine in response to ischemia/ reperfusion injury. METHODS： Forty-seven Sprague-Dawley rats with body weight of 250-300 g were divided into two groups： control group （sham shock n = 5） and experimental group （n = 42）. Experimental group was further divided into six groups （n = 7 each） according to different time points after the hemorrhagic shock, including 0^th group, 1^st group, 3^rd group, 6th h group, 12^th group and 24^th group. All the rats were gavaged with 2 mL of suspension of lactulose （L） （100 mg/2 mL） and mannitol （M） （50 mg/each） at the beginning and then an experimental rat model of hemorrhagic shock was set up. The specimens from jejunum, ileum and colon tissues and the blood samples from the portal vein were taken at 0, 1, 3, 6, 12 and 24 h after shock resuscitation, respectively. The morphological changes of the intestinal mucosa, including the histology of intestinal mucosa, the thickness of mucosa, the height of villi, the index of mucosal damage and the numbers of goblet cells, were determined by light microscope and/or electron microscope. The concentrations of the bacterial endotoxin lipopolysaccharides （LPS） from the portal vein blood, which reflected the gut barrier function, were examined by using Limulus test. At the same time point, to evaluate intestinal permeability, all urine was collected and the concentrations of the metabolically inactive markers such as L and M in urine were measured by using GC-9A gas chromatographic instrument.RESULTS： After the hemorrhagic shock, the mucosal epithelial injury was obvious in small intestine even at the 0th h, and it became more serious at the 1^stand the 3^rd h. The tissue restitution was also found after 3 h, though the injury was still serious. Most of the injured mucosal restitution was established after 6 h and completed in 24 h. Two distinct models of cell deathapoptosis and necrosis-were involved in the destruction of rat intestinal epithelial cells. The number of goblet cells on intestinal mucosa was reduced significantly from 0 to 24 h （the number from 243±13 to 157±9 for ileum, 310±19 to 248±18 for colon; r= -0.910 and -0.437 respectively, all P〈0.001）, which was the same with the large intestine, but the grade of injury was lighter with the values of mucosal damage index in 3 h for jejunum, ileum, and colon being 2.8, 2.6, 1.2, respectively. The mucosal thickness and the height of villi in jejunum and ileum diminished in 1 h （the average height decreased from 309±24 to 204±23 pm and 271±31 to 231±28 pm, r = -0.758 and -0.659, all P〈0.001, the thickness from 547±23 to 418±28μm and 483±45 to 364±35μm, r= -0.898 and -0.829, all P〈0.001）, but there was no statistical difference in the colon （F= 0.296, P = 0.934）. Compared with control group, the urine L/M ratio and the blood LPS concentration in the experimental groups raised significantly, reaching the peak in 3-6 h （L/M： control vs 3 h vs6 h was 0.029±0.09 vs 0.063±0.012 vs 0.078±0.021, r = -0.786, P〈0.001; LPS： control vs3 h vs6 h was 0.09±0.021 vs 0.063±0.012 vs0.25±0.023, r=- -0.623, P〈0.001）, and it kept increasing in 24 h. CONCLUSION： The gut barrier of the rats was seriously damaged at the early phase of ischemic reperfusion injury after hemorrhagic shock, which included the injury and atrophy in intestinal mucosa and the increasing of intestinal permeability. Simultaneously, the intestinal mucosa also showed its great repairing potentiality, such as the improvement of the intestinal permeability and the recovery of the morphology at different phases after ischemic reperfusion injury. The restitution of gut barrier function was obviously slower than that of the morphology and there was no direct correlation between them. Compared with the small intestine, the large intestine had stronger potentiality against injury. The reduction of the amount of intestinal goblet cells by injury did not influence the ability of intestinal mucosal restitution at a certain extent and it appeared to be intimately involved in the restitution of the epithelium.

GENETIC POLYMORPHISM IN HUMAN β-DEFENSIN-1 AND CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN HAN POPULATION IN SOUTH OF CHINA

Objective To investigate the correlation between human β-defensin-1 (HBD-1) exon 2 variations and chronic obstructive pulmonary disease susceptibility in Han population in south of China. Methods The frequency of polymorphic genotypes of HBD-1 exon 2 (1654G/A) was examined in 120 COPD patients (COPD group) and 108 smokers without COPD (control group) by restriction fragment length polymorphism. Results The frequencies of polymorphic genotypes in HBD-1 exon 2 in COPD group were G/G 82.50%, G/A 10.83%, and A/A 6.67%. The frequencies of polymorphic genotypes in control group were G/G 95.37%, G/A 3.70%, and A/A 0.93%. It showed significant difference between two groups(P<0.01). The differences in allele frequencies were also significant between two groups (G allele frequency: 87.92% vs 97.22%; A allele frequency: 12.08% vs 2.78%; P<0.01). The G→A mutation rised along with the severity of the COPD. Conclusion The genetic polymorphism in HBD-1 exon 2 gene might be associated with the susceptibility to COPD in Han population of South China.

Association of Xenobiotic Detoxification Enzymes Gene Polymorphism in Predisposition of Bronchial Asthma and Chronic Obstructive Pulmonary Disease

Glutathione-S-transferase （GST） family enzymes are implicated in the pathopbysiology of bronchial asthma （BA） and chronic obstructive pulmonary disease （COPD）. In some cases both illnesses exhibit similar pathomorphologic and clinical features, indicating common genetic basis of predisposing to development of disease. To assess genetic susceptibility we conducted association analysis of glutathione-S-transferases Mu （M）, Theta （T） and Pi （P） gene polymorphism with disease development in 85 adult asthma, 60 COPD subjects and 64 control subjects. Present investigation of GST gene polymorphisms indicates that GSTM1 and GSTT null alleles are associated with predisposition for COPD and they do not appear to play a substantial role in susceptibility to BA. However, homozygote ＋/＋ and heterozygote ＋/0 genotypes of GSTT1 revealed to be associated with increasing of IgE level in serum in BA patients. Our findings suggest that the 105 Val variant of GSTP1 contributed to the increasing risk of developing of both diseases, and more likely for COPD.

Singlet-State Preparation for Three Λ-type Atoms with Rydberg Blockade Mechanism

A proposal for the generation of singlet states of three A-type Rydberg atoms is presented via the interaction between a separate Rydberg state and an EPR pair. Different from previous schemes, we do not need to couple ground states by using microwave lights but to set appropriate frequency detuning between lasers and two atomic transitions between ground states and Rydberg levels to eliminate the degenerate of the two ground states, making the present protocol more easily in experiment. Moreover, a series of numerical simulations are made to show the feasibility.