ABSTRACT
PURPOSE: This experiment studied the influence of different connection designs of the tapered retention and platform transfer implant on the stress of the abutments and abutment screws. METHODS: Implant models (Platform-switching: 0.2, 0.4, 0.6, 0.8, 1.0 mm; Taper:6°,8°,10°) were established, and Von-mises stress and strain of abutment and abutment screw under different loads were analyzed. RESULTS: With the increase of the platform-switching amount, the peak von-Mises stress and strain of abutment and abutment screw increased. The peak von-Mises stress of the model with platform transfer≥0.8 mm was higher than 690 MPa. In addition, the variation amplitude was horizontal loading>oblique loading>vertical loading. The maximum stress of the abutment was concentrated at the neck of the abutment in 81.67% models. The stress of the abutment screw was concentrated at the turning point of the head and body of abutment screw in all models. CONCLUSIONS: The increase of the amount of platform switching makes the abutment and the abutment screws bear more force in the occlusion process. Therefore, in order to reduce the occurrence of mechanical complications after implantation and restoration, the implant system with the minimum amount of platform transfer should be selected within a certain range. The maximum stress on the abutments and screws exceeds the yield strength of pure titanium in implants with platform-switching amount greater than 0.8 mm, indicating that this design should be selected prudently in clinical practice.
Subject(s)
Dental Abutments , Dental Implants , Biomechanical Phenomena , Bone Screws , Dental Stress Analysis , Finite Element Analysis , Stress, MechanicalABSTRACT
Pelagic sharks are vulnerable to overfishing due to slow growth rates, late-at-maturity and low fecundity, 90% of which are Near Threatened with an elevated risk of extinction according to IUCN Red List Criteria. Trace elements can be accumulated by marine predators and may have detrimental effects on population dynamics. In this study, we analyzed the concentrations of 11 trace elements (Zn, Cu, Cr, Ni, Mn, Se, Co, Hg, Cd, Pb, and As) in muscle and liver tissues of 10 pregnant pelagic thresher sharks (Alopias pelagicus) and their 18 embryos. The results showed that four essential elements (Cu, Cr, Mn, and Se) were accumulated in both tissue types of embryos. Ni and Zn concentrations were higher in embryonic muscle than that in the liver. For nonessential elements, concentrations of As, Cd and Hg in both embryonic tissues were lower than those of their mothers. Though maternal and embryonic tissues had high levels of Hg, the Se/Hg molar ratios in both tissues of the embryo were above 1 with larger values in the embryos, indicating that Se played a protective role against Hg toxicity in embryonic tissues. Liver is the primary energy resource of embryo development. There was no correlation for element concentrations between embryonic and maternal liver tissues, indicating there is a regulatory mechanism to maintain the stability of element contents during maternal transfer in pelagic thresher shark.
Subject(s)
Sharks , Trace Elements , Animals , Conservation of Natural Resources , Environmental Monitoring , Fisheries , Pacific Ocean , Trace Elements/analysisABSTRACT
Stable carbon and nitrogen isotope ratios (δ13C and δ15N, respectively) of multiple tissues with different turnover rates can provide trophic information at different timescales, and thus play an important role in tracing the changes of feeding, habitat utilization and trophic niche of consumers. The δ13C and δ15N contents of muscle, liver and blood of blue sharks (Prionace glauca), longfin mako sharks (Isurus paucus), crocodile sharks (Pseudocarcharias kamoharai) and shortfin mako sharks (I. oxyrinchus) from tropical Atlantic were measured, and the trophic niche was evalua-ted. The results showed that I. oxyrinchus, P. kamoharai, and P. glauca had similar δ15N values, higher than that of I. paucus. Feeding segregation was found between P. glauca and other species, showing unique trophic niche. The largest trophic niche width was observed in I. oxyrinchus, indicating the high diversity of prey and (or) feeding habitats. High trophic niche overlap was found in P. kamoharai and I. oxyrinchus, implying their potential competition for resources. There was no correlation between the differences among tissues in the δ13C or δ15N values and the body size of I. oxyrinchus, P. kamoharai and P. glauca, indicating no recent diet shifts for those species. I. paucus showed significant correlation between δ15N differences in liver, blood and muscle with the shark fork length, indicating its short-term diet shift. The similarity of δ13C and δ15N values and the higher metabolic rates of liver and blood were found in all four shark species, implying the similar incorporation rates of both tissues, which were considered as the short-term indicator of diet.
Subject(s)
Sharks , Animals , Body Size , Carbon Isotopes , Ecosystem , Nitrogen Isotopes/analysisABSTRACT
Understanding the adaptation of important marine species to environmental changes is critical for evaluating the effects of fisheries and climate change on marine services. The jumbo squid, Dosidicus gigas, is a keystone species in the eastern Pacific, which plays an intermediate role in the marine food web. Better understanding of their responses to climate change would be a big step to understand their population dynamics. In this study, stable isotope and high-throughput 16S rRNA sequencing were used to compare the variation of trophic niche, gut length, and gut microbiota of D. gigas in the eastern equatorial water during normal and El Niño periods. The results showed a significant variation in δ13C values for D. gigas in different periods, indicating differences in their food sources. The main phylum-level gut microbiome included Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Proteobacteria, and Tenericutes. There was no significant difference in the gut microbial composition during normal and El Niño periods, but differences in gut microbial diversity and relative abundance of some phyla bacteria. El Niño events could decrease the trophic niche breadth of D. gigas, and positively impact gut length and gut microbial diversity and richness. Firmicutes, Bacteroidetes, Spirochaetes, WPS-2, and Kiritimatiellaeota had a significant increase in the gut microbiota of D. gigas combined with a more concentrated intraspecific rank of distance during El Niño, suggesting that the changes of habitat and food sources caused by El Niño events could limit the distribution range of D. gigas. D. gigas might change their digestive system to improve the digestive and absorption capacity and enhance their immunocompetence. Such a climate-driven alteration might help D. gigas rapidly adapt to the changes of environmental conditions and food resources under El Niño.
Subject(s)
Gastrointestinal Microbiome , Animals , Decapodiformes , Food Chain , Pacific Ocean , RNA, Ribosomal, 16S/geneticsABSTRACT
PURPOSE: The purpose of this study was to observe the friction and wear characteristics of dental fluorapatite glass ceramics, feldspathic porcelain and natural tooth in dry friction and saliva lubrication. METHODS: Two kinds of veneering porcelain (IPS-emaxcream and Vita vm9) coated zirconia-decorative porcelain double-layer material sample were prepared (size 20 mm × 20 mm × 4.5 mm), each group had 20 specimens. Friction and wear tests were carried out on 2 kinds of zirconia-decorative porcelain sample under dry friction and saliva accompanying environment respectively by setting different sizes of vertical load and sliding frequency using MMV-1 friction and wear testing machine. SPSS 17.0 software package was used for one-way ANOVA and t test to determine whether there were differences in friction coefficient and wear amount between two groups. RESULTS: The dynamic friction coefficient and wear amount of fluorapatite glass ceramics under saliva lubrication condition were significantly greater than those under dry friction condition. On the contrary to fluorapatite glass ceramics, the dynamic friction coefficient and wear amount of feldspathic decorative ceramics under dry friction condition were significantly greater than those under saliva lubrication condition. Under dry friction and saliva lubrication, the wear amount of fluorapatite glass ceramics was significantly smaller than that of feldspathic decorative ceramics. Scanning electron microscopy showed that under saliva lubrication condition, fluorapatite glass ceramics and the corresponding natural teeth had more severe wear surface than dry friction. Under dry friction condition, feldspathic decorative porcelain and corresponding natural teeth wear more seriously than fluorapatite glass ceramic, and the difference in saliva lubrication condition was relatively small. CONCLUSIONS: Compared with feldspathic decorative porcelain, fluorapatite glass ceramics and natural teeth shows superior wear resistance under dry friction condition. The addition of saliva can reduce the difference between the friction and wear performance of the two decorative porcelains.
Subject(s)
Ceramics , Dental Porcelain , Apatites , Friction , Materials Testing , Surface Properties , ZirconiumABSTRACT
The coastal waters in Jiangsu Province have always been an important fishery base since ancient time. In recent years, with the development of the industry in coastal cities, heavy metal pollution is becoming serious in Jiangsu Province. However, the bioaccumulation of heavy metals in the coastal food web is still unclear. In this study, we collected samples (including macroalgae, bivalves, cephalopods, gastropods, crustaceans and fish) through fishery resources survey in the coastal waters of Jiangsu in May 2017 and quantified the main ways of the material circulation and energy flows by constructing the food web using stable carbon and nitrogen isotopes. In addition, the bioaccumulation patterns of eight elements (seven heavy metals and 1 metalloid) through the food chains were investigated. The results showed that there were two energy pathways in this offshore ecosystem: the planktonic food-chain and the benthic food-chain, with Scapharca subcrenata and Phalium strigatum as the primary consumers, respectively. The benthic food-chain was the dominant food chain in energy recycling. The mean concentration of heavy metals from high to low in orga-nisms were Zn, Cu, As, Cd, Cr, Pb, Ni and Hg. The highest concentrations of elements were found in bivalves and the lowest ones in fish. The concentration of As in most species, the levels of Cd in bivalves and Oratosquilla oratoria, the Cr in Coilia mystus and the Zn, Cu, Cr in Ostrea denselamellosa exceeded the proposed health advisory levels. Regarding the bioaccumulation, a decrease in the concentration levels of Zn, Cd and Ni were observed along the planktonic food-chain and a significant positive correlation between Hg and trophic position were found across the benthic food-chain. Other elements had no significant change.
Subject(s)
Environmental Monitoring , Food Chain , Metals, Heavy/analysis , Water Pollutants, Chemical/analysis , Animals , ChinaABSTRACT
As the apex predators of the open ocean ecosystems, pelagic sharks play important roles in stabilizing the marine food web through top-down control. Stable isotope analysis is a powerful tool to investigate the feeding ecology. The carbon and nitrogen isotope ratios can be used to trace food source and evaluate the trophic position of marine organisms. In this study, the isotope values of 130 pelagic sharks from 8 species in Central Eastern Pacific were analyzed and their trophic position and niche were calculated to compare the intra/inter-specific resource partitioning in the Central Eastern Pacific ecosystem. The results exhibited significant differences in both carbon and nitrogen isotope values among the shark species. The trophic levels ranged from 4.3 to 5.4 in the Central Eastern Pacific shark community. The trophic niche of blue sharks and shortfin mako sharks showed no overlap with the other shark species, exhibiting unique ecological roles in the open ocean food web. These data highlighted the diverse roles among pelagic sharks, supporting previous findings that this species is not trophically redundant and the trophic niche of pelagic sharks can not be simply replaced by those of other top predator species.
Subject(s)
Food Chain , Sharks , Animals , Ecology , Ecosystem , Nitrogen Isotopes/analysisABSTRACT
Stable isotope technique was applied to investigate the small and medium-size consumers including not only fish, shrimps, crabs, cephalopods, snails and bivalves, but also the specimens of their potential carbon sources, which were collected in the marine ranching area of Haizhou Bay during the spring of 2015. IsoSource model was adopted to calculate the contribution of potential carbon sources to the consumers. Biospeciemens collected in the summer of 2014 were compared with those in the spring of 2015, aiming to analyze the seasonal variation in the trophic structure of food web. Six quantitative community indices were calculated based on the isotope values of the organisms in Haizhou Bay. The results showed that the δ13C values of consumers ranged from -18.9 to -17.1, and the δ13C values of three potential food sources ranged from -18.1 to -23.4 in the spring of 2015. The calculation results of IsoSource model further demonstrated that the phytoplankton was the most important carbon source for consumers (80.8%), followed by sediment organic matter (10.8%) and particulate organic matter (8.4%). There was a significant difference in the δ13C values between the biospecimens in the summer of 2014 and those in the spring of 2015, while no significant difference was observed in δ15N values. Trophic structure of community-wide differed remarkably in different seasons indicated by the six quantitative community indices. The δ13C range, total area, mean nearest neighbor distance and standard deviation of nearest neighbor distance of the community were much higher in 2014 than those in 2015, but the δ15N range and mean distance to centroid showed no significant change. The trophic structure redundancy was lower in the summer of 2014 compared with that in the spring of 2015, however, the diversity of food resources was higher in the summer of 2014.
Subject(s)
Food Chain , Nitrogen Isotopes , Animals , Bays , Carbon Isotopes , China , SeasonsABSTRACT
Stable isotope analysis has been widely used in marine food web studies. An appropriate isotopic baseline is essential for calculating diet or trophic position of marine organisms when using stable isotopic data. This paper provided an overview of the selection of isotopic baselines for four ty-pical marine ecosystems, i.e. estuary and bay, neritic zone, oceanic zone, and deep sea. The interferential factors of baseline selection and the significance of compound specific stable isotope in minimizing the effects of temporal-spatial variations of isotopic baseline were summarized, and the issues needed to be solved in this field and several directions for further research were presented. It would provide a beneficial reference for further research on stable isotope ecology in marine ecosystems.
Subject(s)
Carbon Isotopes , Food Chain , Nitrogen Isotopes , Ecology , Ecosystem , Oceans and SeasABSTRACT
As a pelagic cephalopod and one of the main target species of Chinese distant water fishery, jumbo squids (Dosidicus gigas) play a major role in the marine ecosystems of the eastern Pacific. Understanding the feeding ecology and migration patterns of jumbo squids is of importance for better utilizing the resources. The isotopic signatures of gladius, have been proved to be a powerful tool to reveal high resolution and ontogenic variations in individual foraging strategies of squids; which is an archival tissue with no elemental turnover after formation. In this study, the growth equation of gladius proostracum was established based on the age information determined by statolith. Gladius was cut successionally by the growth curve of gladius proostracum, the stable isotopic values of the gladius profiles were determined, and the feeding ecology and migration patterns of jumbo squids during its growth process were investigated. Results showed that the jumbo squids began to migrate after 180 days of postnatal, and their trophic levels tended to decrease throughout the life span. These results demonstrated the feasibility of using continuous sampling hard tissue to study the feeding ecology and habitat transfer of jumbo squids.
Subject(s)
Animal Migration , Decapodiformes/physiology , Ecosystem , Animals , Carbon Isotopes/analysis , Ecology , Nitrogen Isotopes/analysis , PeruABSTRACT
Based on the data of lake survey conducted during 2008-2009 and the published data of the trophic ecology of key species, the exploited freshwater ecosystem of Lake Taihu was described using Ecopath with Ecosim 6.1 with the aim of characterizing its functioning and structure. The model comprised 20 functional groups including primary producers, the main species of fishes, nonfish vertebrates, and detritus. Results showed that the functional groups were organized into four aggregated trophic levels with the highest levels corresponding to the top predators, culters. Two trophic pathways were found in Lake Taihu, the detrital pathway and grazing pathway. The detrital pathway dominated in the ecosystem. As a consequence of the low ecotrophic efficiency of primary producer and detritus (trophic level I ), the accumulating detrital sediments continually released waste nutrients back into the system, resulting in its internal pollution. Considering Odum and Ulanowicz's theory of ecosystem development, the ecosystem was placed on a low developmental stage with high net primary production (NPP), net primary production/total respiration (NPP/R) and lower connectance index (CI), system omnivory index (SOI), and Finn' s cycling index (FCI). The results of mixed trophic impacts and keystone species selection showed that the increasingly intensive fishing exerted a negative effect on the ecosystem, and the top-down effects of top predators were becoming much obviously reduced.
Subject(s)
Ecosystem , Lakes , Models, Biological , Animals , Environmental Pollution , Fresh WaterABSTRACT
Cephalopods play an important role in marine food webs, however, knowledge about their complex life history, especially their feeding ecology, remains limited. With the rapidly increasing use of stable isotope analysis (SIA) in ecology, it becomes a powerful tool and complement of traditional methods for investigating the trophic ecology and migration patterns of invertebrates. Here, after summarizing the current methods for trophic ecology investigation of cephalopods, applications of SIA in studying the trophic ecology of cephalopods were reviewed, including the key issues such as standardization of available tissues for SIA analyzing, diet shift and migration patterns of cephalopods, with the aim of advancing its application in the biology of cephalopods in the future.
Subject(s)
Cephalopoda , Isotopes/analysis , Animals , Diet , Ecology/methods , Food ChainABSTRACT
With the rapidly increasing use of stable isotope analysis (SIA) in ecology, it becomes a powerful tool and complement to traditional methods for investigating the trophic ecology of animals. Sharks play a keystone role in marine food webs as the apex predators and are recently becoming the frontier topic of food web studies and marine conservation because of their unique characteristics of evolution. Recently, SIA has recently been applied to trophic ecology studies of shark species. Here, we reviewed the current applications of SIA in shark species, focusing on available tissues for analyzing, standardized analytical approaches, diet-tissue discrimination factors, diet shift investigation, migration patterns predictions and niche-width analyses, with the aim of getting better understanding of stable-isotope dynamics in shark biology and ecology research.
Subject(s)
Animal Migration , Diet/veterinary , Food Chain , Sharks/physiology , Animals , IsotopesABSTRACT
Stable isotope analysis (SIA) has become an important tool to investigate diet shift, habitat use and trophic structure of animal population. Muscle is considered to be the most common tissue for SIA, however, lipid content in muscle causes a considerable bias to the interpretation of isotopic ratios of animals. Neon flying squid (Ommastrephes bartramii) is an important economic cephalopod of Chinese distant water fishery, and plays a major role in marine ecosystems. In this study, the effects of lipid extraction on stable isotope ratios of the muscles of 53 neon flying squids were investigated and the interference mechanism of lipid in SIA was clarified with the aim of contrasting the suitability of different lipid correction models of stable carbon isotope. Results showed that the stable carbon and nitrogen isotopic values of non-lipid extracted samples significantly increased after lipid extractions by 0.71 per thousand and 0.47 per thousand, respectively, which suggested that lipid extraction in cephalopod isotope study is needed prior to stable carbon isotope analysis but not recommended for stable nitrogen isotope analysis. The results could help remove the effects of lipid contents and standardize SIA muscle samples, thereby getting better understanding of the isotopic change of neon flying squids in the future.
Subject(s)
Carbon Isotopes/analysis , Decapodiformes/chemistry , Lipids/chemistry , Muscles/chemistry , Nitrogen Isotopes/analysis , Animals , Carbon , Diet , NitrogenABSTRACT
The canal-lining project in Hetao Irrigation District (HID) for water-saving irrigation has been implemented for many years. By using statistical method, ordinary Kriging, and software ArcGIS 9.0, this paper analyzed the spatiotemporal variation of groundwater table depth and salinity in HID in September, 2001 and 2009. In the meantime, the vegetation distribution on the both shores of the lining part and non-lining part of Yangjiahe channel was also investigated. After the many years implementation of the project, the water diversion amount in HID in 2009 was reduced to 44.5 x 10(8) m3. The region area of groundwater table with a depth of 2.5-3.0 m was increased from 1.2 x 10(4) hm2 in 2001 to 9.11 x 10(4) hm2 in 2009. The region area of groundwater table with a depth of 2.0-2.5 m in 2009 took 80% of the total area of HID. In the northwestern region of HID, the groundwater salinity had reduced from 5000-10000 mg x L(-1) to 3000-5000 mg x L(-1). In Wulate irrigation region, the areas of salt water belt and half-salt water belt were increasing. After the canal-lining of Yangjiahe channel, the plant species and diversity index on both shores reduced, and some herbaceous plants with shallow roots showed degradation signs. The implementation of the project and the reduction of water diversion for irrigation did not exert negative effects on the maintenance of water surface area of Wuliangsuhai Lake.
