Intersection Site Research Articles

Achilles tendon regeneration after experimental transverse tenotomy with preserved peritenon and the structures

Introduction The Ponseti method is the first choice for congenital clubfoot with the possibilities of transverse tenotomy being underexplored in repair of the Achilles tendon in pediatric patients.The objective was to identify specific features of the Achilles tendon repair after experimental transverse intersection and preserved peritenon, vessels and nerves of growing rabbits.Material and methods The experimental study included 20 Chinchilla rabbits of both sexes aged 1.0–1.5 months used as a biomodel with a weight of 1476.0 ± 114.3 g. Rabbits were sacrificed in groups of five by air embolism under local anesthesia at 15, 30, 60 and 90 days of surgery.Results The tendon defect zone was represented by small areas of dense fibrous scar tissue with some cellular fibroblasts, and tendon fibers of unremarkable architectonics arranged in a mutually parallel waves could be seen in the layers of connective tissue at 90 days. The thickness of the first-order collagen fibers increased to 8.9 ± 1.32 µm and comparison with the normal value of 9.2 ± 1.88 µm showed no statistically significant difference (p = 0.38). The thickness of the second-order collagen fibers increased to 28.1 ± 1.28 µm during the time, and comparison with the standard measurements of 28.3 ± 2.23 µm demonstrated no statistically significant difference (p = 0.64).Discussion According to the literature, the ability of the tenoblast to synthesize structural proteins and regulatory biomolecules after injury decreases with age and leads to fibrous restoration of the tendon and formation of a permanent scar. Our study on growing rabbits showed that the organotypic structure of the experimental tendon restored at the intersection site at 60 days with the Achilles tendon defect being represented by the tendon-like tissue at 90 days.Conclusion The Achilles tendon was shown to regenerate in optimal conditions after the dissection and preservation of the peritenon, vessels and nerves with tendon tissue being formed within a short time (3 months after the intervention) being identical to the original.

Prediction and effectiveness study of fracture distribution based on an artificial neural network technology and production performance data detection method: a case study of Ordovician carbonate formation in the Tahe oilfield, Tarim Basin

To solve the difficulty of predicting the spatial distribution of fracture linear density and clarify the controlling influence of tectonic factors on the effectiveness of fractures. This article combines core, conventional logging, imaging logging, and 3D seismic volume data and uses artificial intelligence neural network technology combined with the sequential Gaussian method to establish a linear density volume prediction model for fractures in the study area. In addition, production dynamic data are applied to verify the effectiveness of the fractures. The results show that the artificial intelligence neural network technique is highly applicable with an accuracy of up to 76.8% in predicting the fracture linear density. The fracture linear density is controlled by tectonic activity, and the fracture linear density increases sharply in the areas adjacent to the main faults, the fracture superposition site, and the intersection site of multiple faults, with the fracture linear density reaching 8.65 fractures per meter in study areas. The effective distance of fracture connectivity is mostly concentrated between 550 and 670 m. When the difference in fracture density along the structural ridge is between 2 and 4 fractures/meter, the effectiveness of the fractures is strong.

Emerging roles of lysosome homeostasis (repair, lysophagy and biogenesis) in cancer progression and therapy

In the era of personalized therapy, precise targeting of subcellular organelles holds great promise for cancer modality. Taking into consideration that lysosome represents the intersection site in numerous endosomal trafficking pathways and their modulation in cancer growth, progression, and resistance against cancer therapies, the lysosome is proposed as an attractive therapeutic target for cancer treatment. Based on the recent advances, the current review provides a comprehensive understanding of molecular mechanisms of lysosome homeostasis under 3R responses: Repair, Removal (lysophagy) and Regeneration of lysosomes. These arms of 3R responses have distinct role in lysosome homeostasis although their interdependency along with switching between the pathways still remain elusive. Recent advances underpinning the crucial role of (1) ESCRT complex dependent/independent repair of lysosome, (2) various Galectins-based sensing and ubiquitination in lysophagy and (3) TFEB/TFE proteins in lysosome regeneration/biogenesis of lysosome are outlined. Later, we also emphasised how these recent advancements may aid in development of phytochemicals and pharmacological agents for targeting lysosomes for efficient cancer therapy. Some of these lysosome targeting agents, which are now at various stages of clinical trials and patents, are also highlighted in this review.

Plasticity of solid solution Al-Mn and Al-Mn-Si alloys

The influence of Mn and Si on the mechanical properties of solid solution Al-Mn and Al-Mn-Si alloys have been studied at 4 K, 78 K, and 298 K. The solute strengthening potency of the yield strength increases with decreasing temperature. The addition of Si stimulates the precipitation of Mn-containing dispersoids and decreases the solubility of Mn in the Al matrix, reducing the strengthening effect. The alloys exhibit Stage III of declining work hardening rate with the flow stress during the plastic flow at three temperatures. The mean slip length Λ in the work hardening model of Nabarro, Basinski, and Holt (NBH) evaluated from σΘ curves correlates with the scale of the microstructure. The strain rate sensitivity (SRS) measurements conducted at 78 K show positive SRS of Al and the alloys. At 298 K, one observes a change in SRS due to the change of the mechanism from solute-dislocation to dislocation-dislocation dominated interactions. Mn and Si decrease SRS at 298 K. Al-Mn-Si alloys exhibit negative SRS and jerk flow at a sufficiently low strain rate at 298 K. Analysis of the apparent activation volume, distance, and work has been conducted at 78 K and 298 K to understand the rate-controlling mechanisms. The results indicate that dislocation intersections are rate-limiting processes, but the atomistic mechanism of dislocation cutting varies vastly depending on the temperature and alloy composition. It is suggested that at 78 K, forest obstacles are passed by the formation of jogs and sequential activation of individual partials without making constriction to the perfect defect. At 298 K, the cutting involves constriction, the creation of jogs, and the creation of point defects at each intersection site. The calculated activation work and distance provide signatures of these processes.

Capacity at All-Way Stop Control Intersections: Case Study

This paper presents an empirical investigation into the capacity of all-way stop-controlled (AWSC) intersections. Video data was collected over four days at an AWSC intersection site in Bozeman, Montana. The site is characterized by single-lane approaches and high level of vehicular and pedestrian traffic. Using strict protocols, video records were processed at the individual vehicle level and several information metrics were extracted for each vehicle in the data set on all approaches. Study results indicate that the total intersection capacity at the study site varied between 400 and 1,400 vehicles per hour. The study suggests that the wide range of capacity observations is largely associated with the pedestrian crossing activity at the study site. Statistical tests confirmed that both pedestrian crossing activity and the level of conflict have significant effects on intersection capacity at the 95% confidence level. For movement type, the right-turn movement was not found to have a significant effect on intersection capacity while left-turn movement was found to negatively affect the intersection capacity. The results presented in this paper offer valuable information on AWSC intersection capacity, given the limited amount of information in the literature and the dated nature of those empirical observations.

Rate-Controlling Microplastic Processes during Plastic Flow in FCC Metals: Origin of the Variation of Strain Rate Sensitivity in Aluminum from 78 to 300 K

The thermodynamic response of dislocation intersections with forest dislocations and other deformation products is recorded using the Eyring rate relation wherein the application of shear stress increases the probability of activation at a given strain rate and temperature. The inverse activation volume, 1/ν, can be directly determined by instantaneous strain-rate change and its dependence on flow stress, τ, defines the strain-rate sensitivity, S, through the Haasen plot slope. A linear slope over a large strain interval is observed even for a heterogeneous distribution of obstacles that could be of more than one type of obstacles encountered by the gliding dislocation. It was deduced that ν and τ at each activation site are coordinated by the internal stress resulting in constant activation work (k/S). The stress changes from down-rate changes become larger than that from up-rate changes due to the formation of weaker obstacles, resulting in a composite S, whereas only forest dislocations are detected by the up-change. The additivity of 1/ν was used to separate obstacle species in specially prepared AA1100 and super-pure aluminum from 78 to 300 K. The deduction that repulsive intersection is the rate-controlling process and creates vacancies at each intersection site depending on temperature was validated by observing the pinning and depinning of dislocations via pipe diffusion above 125 K. A new method to separate S for dislocation-dislocation intersections from the intersections with other obstacles and their temperature dependence is presented and validated.

Planning-Level Crash Prediction Models in Southern California

Macro- or planning-level crash prediction models (CPMs) differ from traditional predictive safety models in that they predict crashes for a geographic area rather than at a specific segment or intersection site. These models lend themselves to traditional planning-level activities, particularly when the exact design or dimensions of a road facility have yet to be determined. This paper describes a research effort conducted by the Southern California Association of Governments (SCAG) to develop a series of models to support safety analyses as part of the agency’s quantitative planning approach. The models were found to support SCAG’s planning at two scales: one series of models addressed annual performance measure target setting for the entire SCAG region by predicting severe injuries per year (i.e., annual fatalities, serious injuries, and nonmotorized fatalities and serious injuries), and a second series of models predicted crashes that contribute to agencywide performance measures, but at a community- or neighborhood level. These latter community models predicted crashes at a scale that will assist in evaluating scenarios for future projects or local community growth. The models developed through this research were consistent with previous research and display a promising ability to accurately predict crashes and injuries that are key benchmarks for regional safety planning.

Black carbon and elemental characterization of PM2.5 in dense traffic areas in two cities in Fiji, a Small Island Developing State

PM2.5 characterizations are essential in understanding its impact on the health of the exposed population. Sampled PM2.5 by Mani et al. (2020) was characterized to determine atmospheric metal concentration and inhalation health risk in Suva and Lautoka Cities, the only two cities in Fiji and one of the largest in the South Pacific Islands. Twenty-two elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Si, Sr, V, Zn) were analyzed using ICP-OES. Black Carbon (BC) sampling was also done at three different sites in Suva City, namely, Fiji National University Samabula Intersection site, Suva City Bus Station site and the Reservoir Road Community Settlement Site as well as at Lautoka City Bus Station. Mean BC concentrations over the sampling period were found to be 3.9 ± 2.9 (median = 3.3 μg/m3), 2.6 ± 2.7 μg/m3 (median = 1.7 μg/m3), 2.4 ± 2.3 μg/m3 (median = 1.7 μg/m3) and 4.0 ± 4.7 μg/m3 (median = 2.4 μg/m3) respectively. Health risk assessments (Carcinogenic Risk (CR) and Non-Carcinogenic Risk (HQ)) were also done to assess the risk of inhalation exposure in adults and children. The Hazard Index for children in Lautoka (HI = 1.03) was found to slightly exceed the safe level of 1. This study provides the first inventory of atmospheric particulate bound metal concentrations and diurnal BC profiles in Fiji and informs policy makers and scientists for further studies.

Safety Performance of Rural Curved Corner Intersections with Regional Effects

This study evaluates the intersection of rural roads where a curved roadway segment connects the major flow of through traffic from orthogonal directions. A system of up to three intersections in combination can be represented singly by the situation modeled in this paper as a curved corner intersection site. This paper evaluates the application of random intercept negative binomial (NB) regression modeling to produce safety performance functions, and compares the outcome with NB models using fixed regional effects. At curved corner intersections, installing a combined/merged intersection approach near the midpoint of the curve is a potential countermeasure that by comparison with three-leg configurations experienced 20% fewer intersection crashes. A larger radius of curvature along the curved segment at these types of intersections is also very favorable for safety performance. Each 100 ft increase in the radius of a three-leg or four-leg curved corner intersection is estimated to reduce total non-animal crash occurrence by 5% and 7%, respectively. This study can help safety engineers to prioritize the improvement of rural un-signalized intersections.

In-situ EBSD investigation of plastic damage in a 316 austenitic stainless steel and its molecular dynamics (MD) simulations

The damage evolution process in 316 austenitic stainless steel at the plastic stage were investigated in this paper by using the in-situ EBSD technique and MD simulation in combination. The damage mechanisms of 316 steel are typified by an intergranular and intragranular mixed mode. The in-situ EBSD results showed that the intergranular damage was the defects formation at the GBs, and the twin-GB intersections and the triple GB are the preferred damage sites. While the intragranular damage was manifested by the mixing of lattice orientation change, intragranular flaws appearance, and twin degradation; The MD simulation results manifested that the initial lattice structure changed after the plastic strain, and the continues increase of the atom displacement resulted in the defect formation. The simulation results also verified that the twin-GB intersection site could be a fragile location, the void preferentially appeared here, and the disorder degree of atoms over here were great. In addition, the defects also generated at the triple GB, which indicated that the triple GB could also be a weak location.

Operational Limits and Failure Mechanisms in All-2D van der Waals Vertical Heterostructure Devices with Long-Lived Persistent Electroluminescence.

Various 2D materials can be assembled into vertical heterostructure stacks that emit strong electroluminescence. However, to date, most work is done using mechanical exfoliated materials, with little insights gained into the operation limits and failure mechanisms due to the limited number of devices produced and the device-to-device variances. However, when using chemical vapor deposition (CVD) grown 2D crystals, it is possible to construct dozens of devices to generate statistics and ensemble insights, providing a viable way toward scalable industrialization of 2D optoelectronics. In particular, the operation lifetime/duration of electroluminescence and subsequent failure mechanisms are poorly understood. Here, we demonstrate that all-2D vertical layered heterostructure (VLH) devices made using CVD-grown materials (Gr:h-BN:WS2:h-BN:Gr) can generate strong red electroluminescence (EL) with continuous operation for more than 2 h in ambient atmospheric conditions under constant bias. Layer-by-layer controlled assembly is used to achieve graphene top and bottom electrodes in a crossbar geometry, with few layered h-BN continuous films as tunnel barriers for direct carrier injection into semiconducting monolayer WS2 single crystals with direct band gap recombination. Tens of the devices were fabricated in a single chip, with strong EL routinely measured under both positive and negative graphene electrode bias. The success rate for EL emission in devices is over 90%. EL starts to be detected at bias values of ∼5 V, with bright red emission located at the crossbar intersection site, with intensity increasing with applied bias. Long-lived persistent EL is demonstrated for more than 2 h without significant degradation of WS2 under high bias conditions of 20 V. In cycling tests, the EL signal peak position and intensity stay almost the same after several ON/OFF cycles with high bias, which proves that our device has good stability and durability when pulsed. Breakdown of the device is shown to occur at a bias value of ∼35 V, whereby current reduces to zero and EL abruptly stops, due to breakdown of the top graphene electrode, associated with local heating accumulation. This study provides a viable way for wafer-scale fabrication of high-performance 2D EL arrays for ultrathin optoelectronic devices and sheds light on the mechanisms of failure and operation limits of EL devices in ambient conditions.

Type of crossing of coal waste dumps by geodynamical dangerous zones

The paper develops the concept of the existence geodynamically dangerous zones in the earth’s crust. These zones affects to the safety of the state of engineering structures and mining operations. The concept of geodynamic zoning is used, according to which geodynamically dangerous zones occurs during the interaction of blocks of the earth’s crust of various hierarchical ranks. On the example of the East Donbass, the typification of the intersection of coal waste dumps with geodynamically dangerous zones is considered. The position of 34 burning and burnt out dumps located near the cities of Shakhty and Novoshakhtinsk, Rostov Region, their size R and the width of geodynamically dangerous zones r are taken in account. Based on the use of geodynamic zoning data, an analysis is made of the nature of the mutual arrangement of carbon rock dumps and the boundaries of blocks of the earth’s crust (geodynamically dangerous zones). It is found 4 types of intersection of the block boundaries and the body of the dumps. The intersection of the first type occurs when R> r and the location of the intersection site entirely under the dump. The intersection of the second type occurs when R <r and the location of the dump entirely in the geodynamically dangerous zone. The intersection of the third type occurs at any ratio of R and r, but the common area overlaps the geodynamically dangerous zone only partially (touch). In the fourth type of intersection, the set of common points R and r is empty (do not intersect). Typification can be used when choosing places for dumping and computer modeling of their thermal state.

Existence of spontaneous symmetry breaking in two-lane totally asymmetric simple exclusion processes with an intersection**Project supported by the National Natural Science Foundation of China (Grant No. 11802003).

We study two-lane totally asymmetric simple exclusion processes (TASEPs) with an intersection. Monte Carlo simulations show that only symmetric phases exist in the system. To verify the existence of asymmetric phases, we carry out a cluster mean-field analysis. Analytical results show that the densities of the two upstream segments of the intersection site are always equal, which indicates that the system is not in asymmetric phases. It demonstrates that the spontaneous symmetry breaking does not exist in the system. The density profiles and the boundaries of the symmetric phases are also investigated. We find that the cluster mean-field analysis shows better agreement with simulations than the simple mean-field analysis where the correlation of sites is ignored.

Cancer and non-cancer health risk assessment associated with exposure to non-methane hydrocarbons among roadside vendors in Delhi, India

This study estimates the cancer and non-cancer health risk among the roadside vendors in Delhi, the capital city of India. Air samples of selected NMHCs and their derivatives were collected from four different sites (one traffic intersection, one industrial, and two residential) in Delhi and were analyzed on Gas Chromatograph (GC) to obtain their atmospheric concentrations. At each site, a survey among the roadside vendors was also conducted to obtain information about their bodyweight and exposure to outdoor ambient air. The study reveals that hazard quotient of 1,3-butadiene is greater than one at all the sites, with its maximum value occurring at the industrial site. The major contributors to the workplace cancer risk (WCR) are found to be 1,3-butadiene and chloroform. The overall WCR is observed to be the highest (9.4 × 10−4) at the traffic intersection site, followed by the industrial site (7.0 × 10−4). Cancer incidence data and the population data are also used to estimate the growth of cancer risk in Delhi from 2009 to 2016. Comparison of the WCR values of the four sites with the cancer risk estimated from the cancer incidence data shows that NMHCs and their derivatives are significant contributors to the overall cancer risk in Delhi. Our results suggest that NMHCs and their derivatives need to be given due consideration in the National Cancer Control Programme of India.

The anatomical relationship between the axillary artery and vein investigated by radial coronary angiography.

To reduce the risk of inadvertent arterial puncture and bleeding, we aimed to define a safe puncture site by demonstrating the relation of the axillary artery and vein. The anatomical course and relation as well as crossover sites of the axillary artery and vein, the presence of small arterial bridges over the axillary vein, and validation of commonly preferred axillary venous puncture sites were determined by simultaneous ipsilateral venography in patients (n=111; 80 men, age 60 ± 10 years) who underwent coronary angiography by radial artery access. The axillary vein was detected at the first costa-clavicular intersection in 62% and at the second anterior and third posterior costal intersection in 60% of the patients. Small arterial bridges over the axillary vein were observed in 77% of the patients and more frequently in females and body mass index ≥25kg/m2 (P=0.034 and P=0.03, respectively). The axillary artery crossed the vein in 24% of the patients and almost always within the region close to the first costa-clavicular intersection site. Our study demonstrated a high crossover rate (24%) of axillary artery and vein and a high degree of variation in the course of axillary vein. Small arterial bridges over the axillary vein were observed in 77% of the patients.

SPATIAL VARIABILITY OF HEAVY METAL POLLUTION POTENTIAL FROM AN URBAN ROAD NETWORK

This study investigated the spatial variability of heavy metal emission patterns and associated measures of contamination on Riccarton Campus at Heriot-Watt University in Edinburgh, Scotland. Road deposited sediments were collected from 12-different sites representing typical urban/sub-urban road layout over a 10 month period covering seasonal variations. The heavy metal concentrations of the road sediments collected from different sites of a road were determined by strong nitric acid digestion and atomic absorption spectrometry. The contamination levels of the heavy metals in the road deposited sediments were assessed by the accumulation index, the degree of contamination and the ecological risk index. The outcomes of the investigation showed highly site-specific heavy metal emissions that primarily varied with road lay-out, with also influences from road surface condition, surrounding land use and traffic volume. The degree of contamination and the associated ecological risk index revealed that bus stops, a road bend, a road with speed control measures and a road intersection site were the pollutant hot-spot areas among all the sites that may likely pose moderate to considerable levels of pollution to the nearby water environment.

Damage nucleation from repeated dislocation absorption at a grain boundary

Damage nucleation from repeated dislocation absorption at a grain boundary is simulated with molecular dynamics. At the grain boundary–dislocation intersection site, atomic shuffling events determine how the free volume brought by the incoming dislocation is accommodated. This process in turn determines the crack nucleation mechanism, as well as the critical strain and number of dislocations that can be absorbed before cracking. Slower strain rates promote earlier crack nucleation and a damage nucleation mode where cracking is preceded by dislocation emission. The simulation methodology presented here can be used to probe other types of boundaries as well, although multiple thermodynamically equivalent starting configurations are required to quantify the damage resistance of a given grain boundary.

Computational Investigation of the Lewis Acidity in Three-Dimensional and Corresponding Two-Dimensional Zeolites: UTL vs IPC-1P

The adsorption and catalytic properties of three-dimensional zeolite UTL were investigated computationally along with properties of its two-dimensional analogue IPC-1P that can be obtained from UTL by a removal of D4R units. Adsorption properties and Lewis acidity of extra-framework Li(+) sites were investigated for both two- and three-dimensional forms of UTL using the carbon monoxide as a probe molecule. The CO adsorption enthalpies, calculated with various dispersion-corrected DFT methods, including DFT/CC, DFT-D2, and vdW-DF2, and the CO stretching frequencies obtained with the νCO/rCO correlation method are compared for corresponding Li(+) sites in 3D and 2D UTL zeolite. For the majority of framework Al positions the Li(+) cation is preferably located in one of the channel wall sites and such sites remains unchanged upon the 3D → 2D UTL transformation; consequently, the adsorption enthalpies become only slightly smaller in 2D UTL (less than 3 kJ mol(-1)) due to the missing part of dispersion interactions and νCO becomes also only up to 5 cm(-1) smaller in 2D UTL due to the missing repulsion with framework oxygen atoms from the opposite site of the zeolite channel (effect from the top). However, when Li(+) is located in the intersection site in 3D UTL (about 20% probability), its coordination with the framework is significantly increased in 2D UTL and that is accompanied by significant decrease of both νCO (about 20 cm(-1)) and adsorption enthalpy (about 20 kJ mol(-1)). Because the intersection sites in 3D UTL are the most active adsorption and catalytic Lewis sites, the results reported herein suggest that the 3D → 2D transformation of UTL zeolite is connected with partial decrease of zeolite activity in processes driven by Lewis acid sites.

象山港网箱养殖区沉积物的古菌空间分布

PDF HTML阅读 XML下载 导出引用 引用提醒 象山港网箱养殖区沉积物的古菌空间分布 DOI: 10.5846/stxb201212041745 作者: 作者单位: 宁波大学海洋学院,宁波大学海洋学院,宁波大学海洋学院,宁波大学海洋学院,宁波大学海洋学院,宁波大学海洋学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41101234）；浙江省教育厅科研项目（Y201121499）；宁波大学学科项目（xkl11090）；国家863资助项目（2012AA092001） The archaeal spatial distribution in sediments of cage culture area in Xiangshan Bay, Zhejiang, China Author: Affiliation: School of Marine Science, Ningbo University,School of Marine Science,Ningbo University,School of Marine Science,Ningbo University,School of Marine Science,Ningbo University,School of Marine Science,Ningbo University,School of Marine Science,Ningbo University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对象山港网箱养殖区及其周边沉积物中古菌群落的空间分布进行研究，应用基于16S rRNA基因的T-RFLP（末端限制性片段多态性分析）技术分析象山港网箱养殖区及其周边不同深度沉积物中古菌的群落结构和多样性，并构建克隆文库进行系统发育学分析。测定沉积物各项理化因子，通过PCA和RDA分析了古菌群落分布及其与环境因子之间的关系。结果表明，泉古菌是港口沉积物中的优势古菌群，占古菌群落的50%以上。网箱养殖区沉积物的古菌群落结构较非养殖区简单，多样性降低。非养殖区古菌群落随深度呈现有规律的变化。营养盐类和pH是造成养殖区域古菌群落结构区别于非养殖区域的主要环境因素。 Abstract:Archaea was distributed widely in marine environments. It plays an important role in nutrient and energy cycling in marine ecosystems. For studying the archaeal spatial distribution in sediment of cage culture area, archaeal community structures in sediments were investigated in July 2011, in Xiangshan Bay, Zhejiang Province, China. Sediments used in this paper were as the same as described previously[1]: a control or check site (CK), an intersection site 6-8 km from the aquaculture site (IS), and a cage culture site (AC). For sub-sampling, sediments were cut into several sections throughout their depth: a (0-5 cm), b (5-10 cm), c (10-15 cm), d (15-20 cm), e (20-25 cm) and f (50-55 cm). Physiochemical factors (NH4+, NO2-, NO3-, SiO32- and P) of sediments were analyzed in laboratory after transport with liquid nitrogen. Based on 16S rRNA gene, the structure and diversity of archaeal communities in sediments were analyzed by T-RFLP (Terminal Restriction Fragment Length Polymorphism), which was conducted after amplification of the archaeal 16S rRNA partial gene using a fluorescent primer pair 109F /934R-FAM and digestion by TaqI (T^CGA). Archaeal 16S rRNA gene clone library was constructed using DNA extracted from layer 0-5 cm sediment of the CK site, and the following phylogenetic analysis was carried out using ARB software. In agreement with other studies, Crenarchaeota is the dominant archaea in marine sediment. T-RFLP profiles showed that the dominant T-RF of 188 bp, affiliated to Crenarchaeota, occupied 80.3% in the cage culture site, more than it in the check site (61.2%). While, the kingdoms Euryarchaeota and Crenarchaeota were present equally in clone library and methanogens constituted a small proportion of the archaeal community. Because the check site is near to East Sea with a higher salinity, T-RF of 78 bp, belonged Halobacteriales, emerged in its upper layers (0-20 cm) sediments and was more abundant than it in other sites. Principal component analysis for the archaeal 16S rRNA gene T-RFLP using R software indicated a complete separation of archaeal communities of the cage culture sit from the check site. And archaeal communities of the intersection site were in the middle. An obvious difference of archaeal communities in the check site sediments at various depths was indicated by PCA. T-RFs of 78 bp, 88 bp, 383 bp and 188 bp related archaea may be the main microorganisms who made the difference among horizontal and vertical distribution. Although calculation of Shannon diversity index H' and evenness index E' showed large errors in parallels, comparing with the check site, the diversity of archaeal communities in cage culture sediments displayed a dropping tendency. Redundancy analysis of archaeal community compositions and environmental factors of sediments in different sites and depths suggested that nutritive salt and pH mainly affected the distribution of archaeal in horizontal by aquaculture. Eh and ammonium were tend to have a relation with archaeal vertical distribution, especially in the check site. In short, aquaculture affected the spatial distribution of uncultivated archaea. 参考文献 相似文献 引证文献

象山港网箱养殖对近海沉积物细菌群落的影响

Microorganisms play important roles in biogeochemical cycling such as organic matter decomposition and energy transformation.Recently,rapid development of aquaculture has caused a large influx of introduced organic matter into Xiangshan Bay,Zhejiang Province,China.At the same time,many ecological problems have developed in this coastal site.Study of the influence of aquaculture on microbial diversity in sediments is important for the structural and functional assessment of coastal ecosystems.In this paper,sediments in three sites were investigated in July 2011: a control or check site(CK),an intersection site 6—8 km from the aquaculture site(IS),and a cage culture site(AC).As the physicochemical background showed,total organic carbon in those three sites was different.Several physiochemical factors(T,pH,Eh and SO2-4) were analyzed.The temperatures of sediments in Xiangshan Bay decreased with depth,but remained between 23.0—26.5 ℃ in the upper 55 cm layer.The pH of sediments was slightly alkaline,but was elevated slightly in the AC site,although all of the sediments had pH values of 7.6—7.9.The effect of aquaculture on SO2-4 was not significant.However,as expected,the measurement of Eh showed sediment in the CK site had the highest oxidation-reduction potential.Following with physiochemical analysis,the structure and diversity of bacterial communities in sediments from Xiangshan Bay were analyzed by Terminal Restriction Fragment Length Polymorphism(T-RFLP) analysis and cloning/sequencing.Total nucleic acids was extracted from the sediment core.T-RFLP analysis was conducted after amplification of the bacterial 16S rRNA partial gene using a fluorescent primer pair 27-FAM/907R and digestion by Msp I(C^CGG).A bacterial 16S rRNA partial gene clone library was constructed using DNA extracted from the upper 5 cm sediment layer of the CK region,and the phylogenic relationships were analyzed using the neighbor-joining method in ARB software.Our results revealed sediments from Xiangshan Bay had a highly diverse bacterial community,mainly including Proteobacteria,Firmicutes,Gemmatimonadetes,Actinobacteria,Thermomicrobia,Nitrospirae,Acidobacteria,Fusobacteria,Bacteroidetes,Planctomycetes and OP11.Thermomicrobia was the most abundant group in all sediments and layers,while the abundance of Proteobacteria was elevated in the surface layer of the CK site,making up as much as 23.7% of the clone library.The diversity index H′ is an effective method of assessing microbial diversity.In this study,the diversity index H′ was calculated based on T-RFLP relative abundance results.Generally,the bacterial diversity indices were CK IS AC.Surface layer sediments in the CK site showed the highest bacterial diversity(H′=3.83±0.01).The lowest diversity(H′=3.01±0.27) was in the 50—55 cm deep sediment in the AC site.The evenness indices were stable in the CK site(around 0.93),but also decreased in the AC site,especially in deeper layers.In the IS site,both diversity indices and evenness indices were intermediate between the CK and AC sites indicating the cage culture not only changed Eh and pH in sediments in Xiangshan Bay,but also decreased their bacterial diversity and changed the structure of the bacterial community.The bacterial community of coastal sediments was changing from a stable,highly diverse structure to an unstable structure with low diversity.Human activity such as aquaculture imports large amounts of organic matter,which not only modifies natural conditions but also leads to systemic simplification of the bacterial ecosystem.Sustainable and environmental friendly aquaculture methods should be searched for and found.