考虑重金属污染岩石侵入面损伤的本构模型

基于酸碱质子理论,探讨了重金属污染物渗入岩石后的侵蚀机制,并通过对流-弥散模型分析了元素铅(Pb)、镉(Cd)、铜(Cu)、锌(Zn)的延伸性能;采用黏弹性和损伤性单体模型组合法建立了重金属污染岩石的三维组合延伸裂变模型,探讨了不同延伸速率下侵入面的变形规律,并通过三轴静载试验对模型拟合结果进行了验证。结果表明:不同的重金属污染物在岩石中的侵入性能与延伸性能不同;岩性不同的污染岩石在同种试验条件下本构曲线与组合模型的拟合结果具有较好的一致性。

Lymph node metastasis in early gastric cancer with submucosal invasion:Feasibility of minimally invasive surgery

AIM:To explore the feasibility of pertorming minimally invasive surgery(MIS)on subsets of submucosal gastric cancers that are unlikely to have regional lymph node metastasis. METHODS:A total of 105 patients underwent radical gastrectomy with lymph node dissection for submucosal gastric cancer at our hospital from January 1995 to December 1995.Besides investigating many clinicopathological features such as tumor size,gross appearance,and differentiation, we measured the depth of invasion into submucosa minutely and analyzed the clinicopathologic features of these patients regarding lymph node metastasis. RESULTS:The rate of lymph node metastasis in cases where the depth of invasion was<500 μm,500-2 000 μm,or >2 000 μm was 9%(2/23),19%(7136),and 33%(15/46), respectively(P<0.05).In univariate analysis,no significant correlation was found between lymph node metastasis and clinicopathological characteristics such as age,sex,tumor location,gross appearance,tumor differentiation,Lauren's classification,and lymphatic invasion.In multivariate analysis, tumor size(>4 cm vs≤2 cm,odds ratio=4.80, P=0.04)and depth of invasion(>2 000 μm vs ≤500 μm, odds ratio=6.81,P=0.02)were significantly correlated with lymph node metastasis.Combining the depth and size in cases where the depth of invasion was less than 500 μm, we found that lymph node metastasis occurred where the tumor size was greater than 4 cm.In cases where the tumor size was less than 2 cm,lymph node metastasis was found only where the depth of tumor invasion was more than 2 000 μm. CONCLUSION:MIS can be applied to submucosal gastric cancer that is less than 2 cm in size and 500 μm in depth.

Possibility of non-invasive diagnosis of gastric mucosal precancerous changes

AIM: To assess the possibility of non-invasive screening of atrophic chronic gastritis for preventing further development of gastric cancer.METHODS: One hundred and seventy-eight consecutive Helicobacter pylori ( H pylori)-positive dyspeptic patients after detection of serum levels of pepsinogen-1 (PG-1) and gastrin-17 (G-17) by enzyme immunoassay were proposed for endoscopy and histology. The serologic and morphologic results were compared with estimating the sensitivity, specificity and prognostic values of the tests.RESULTS: There was statistically significant reverse dependence between the grade of stomach mucosal antral or corpus atrophy and the proper decreasing of serum G17 or PG1 levels. The serologic method was quite sensitive in the diagnosis of non-atrophic and severe antral and corpus gastritis. Also, it was characterized by the high positive and negative prognostic values.CONCLUSION: Detection of serum G-17 and PG1 levels can be offered as the screening tool for atrophic gastritis. The positive serologic results require further chromoendoscopy with mucosal biopsy, for revealing probable progressing of atrophic process with development of intestinal metaplasia, dysplasia or gastric cancer.

Contrasting responses of native and alien plant species to soil properties shed new light on the invasion of dune systems

Aims Among terrestrial ecosystems,coastal sandy dunes are particularly prone to alien plant invasion.Many studies related the invasion of dune habitats to anthropic causes,but less is known about the role of soil properties and plant traits in plant invasion.In this study,we tested the relationships between soil features and alien plant invasion in dune systems,focusing on the interplay between soil nutrients,soil salinity and plant functional traits.Methods Study sites were sandy barrier islands of the Marano and Grado lagoon(northern Adriatic Sea).One hundred plots(4 m×4 m)were selected within 10 areas according to the main habitats occurring along the ecological gradient of dune system(foredune,backdune and saltmarsh).In each plot,we recorded all plant species occurrence and abundance and we collected a soil core.For each soil sample,soil texture,conductivity(as proxy of soil salinity),organic carbon and nitrogen content were analyzed and related to the species number and cover of native and alien plants.Variation of main reproductive and vegetative functional traits among habitats was also analyzed for both alien and native species.Important Findings Soil properties were strongly related to overall plant diversity,by differently affecting alien and native species pools.In backdune,the most invaded habitat,a high soil conductivity limited the number of alien species,whereas the content of soil organic carbon increased along with alien plant abundance,suggesting also the occurrence of potential feedback processes between plant invasion and soil.We found a significant convergence between native and alien plant functional trait spectra only in backdune habitat,where environmental conditions ameliorate and plant competition increases.Our findings suggest that in harsh conditions only native specialized plants can thrive while at intermediate conditions,soil properties gradient acts in synergy with plant traits to curb/facilitate alien plant richness.

Real-Time Distributed Fiber Optic Sensor for Security Systems： Performance, Event Classification and Nuisance Mitigation

The success of any perimeter intrusion detection system depends on three important performance parameters： the probability of detection （POD）, the nuisance alarm rate （NAR）, and the false alarm rate （FAR）. The most fundamental parameter, POD, is normally related to a number of factors such as the event of interest, the sensitivity of the sensor, the installation quality of the system, and the reliability of the sensing equipment. The suppression of nuisance alarms without degrading sensitivity in fiber optic intrusion detection systems is key to maintaining acceptable performance. Signal processing algorithms that maintain the POD and eliminate nuisance alarms are crucial for achieving this. In this paper, a robust event classification system using supervised neural networks together with a level crossings （LCs） based feature extraction algorithm is presented for the detection and recognition of intrusion and non-intrusion events in a fence-based fiber-optic intrusion detection system. A level crossings algorithm is also used with a dynamic threshold to suppress torrential rain-induced nuisance alarms in a fence system. Results show that rain-induced nuisance alarms can be suppressed for rainfall rates in excess of 100mm/hr with the simultaneous detection of intrusion events. The use of a level crossing based detection and novel classification algorithm is also presented for a buried pipeline fiber optic intrusion detection system for the suppression of nuisance events and discrimination of intrusion events. The sensor employed for both types of systems is a distributed bidirectional fiber-optic Mach-Zehnder （MZ） interferometer.

Similarity in fine-to-total root mass ratio leads to comparative plant-soil feedbacks between co-occurring native and invasive plants

Aims Soil biota can affect plant-plant interactions and non-native plant invasions via plant-soil feedback(PSF).Understanding the drivers underlying interspecific variations in PSF is im portant for predicting the role of soil biota in non-native plant invasions.Recent studies found that PSF could be predicted by plant traits.The success of plant invasions is also linked with plant traits,suggesting a potential linkage between PSF and plant invasion via plant traits,but has not yet been tested.Here,we compared PSF between six phylogenetically paired co-occurring native and invasive plants,and explored the potential linkage between PSF with plant root traits.Methods We conducted a two-phase PSF experiment.Field collected soils were conditioned by the six plant species for 3 months firstly,then seedllings of these plants were grown in living or sterilized soils that had been conditioned by conspecific vs.heterospecific(the conge ner/confamilial species)individuals.We estimated effects of biota in conspecific(conspecific PSF)or heterospecific(heterospecific PSF)soils relative to sterilized soils,and the relative effects of biota in conspecific vs.heterospecific soils(PSF-away)on plant biomass.Important Findings In general,soil biota suppressed plant growth,and there were no differences in conspecific PSF,heterospecific PSF and PSF-away between native and invasive plants.PSF increased with rising plant fineto-total root mass ratio in the presence of soil biota,and its value was comparable between native and invasive plants.Our results indicate that similarity in plant fine-to-total root mass ratio that predicted PSF may have partially led to the comparable PSFs between these native and invasive plants.Studies exploring the linkages among plant traits,PSF and plant invasions with more plants,in particular phylogenetically distant plants,are needed to improve our understanding of the role of soil biota in plant invasions.