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排序方式: 共有675条查询结果,搜索用时 46 毫秒
81.
应用C.W.Thorn thwaite计算PE与气候分类方法对我国671个气候台站资料计算分析结果,得出可能蒸散的地理回归模型为:APE=2037.98-18.8308LAT(纬度)-4.5801LONG(经度)-0.157861ALT(海拔)APE与湿度指数Im与我国植被的主要类型及其分布格局有密切相关性。其热量指标(APE)界限与北美颇相符合,但Im明显偏低,反映了中国植被的生态特点。研究表明该方法在我国有明显的应用前景。 相似文献
82.
83.
Tnia Barros Antnio Braga Antnio Marinho Jorge Braga 《The Yale journal of biology and medicine》2021,94(4):585
Background: Behçet’s disease (BD) is a rare chronic multisystemic vasculitis of unknown etiology. It is usually diagnosed between the 2nd and 4th decades of life, so its association with pregnancy is not unusual. This study aims to characterize the evolution of pregnancy in a group of pregnant women with BD and the impact of this pathology in embryo-fetal morbidity. Methods: A retrospective case-control study included 49 pregnancies in women suffering from BD, followed in our institution. Pregnancy outcomes were compared with a control group of healthy pregnant women. Two controls per case were randomly selected. Statistical analysis used SPSS 25.0, and a p-value of 0.05 was considered statistically significant. Results: Forty-nine pregnancies were included in 27 patients with BD. BD exacerbation occurred in 32.6% of the pregnancies. There were no significant statistical differences between the two groups regarding the rate of preterm delivery, gestational diabetes, and preeclampsia (p>0.05). In the BD group, we found a higher rate of miscarriage (24.5%) and fetal growth restriction (FGR, 13.3%, p<0.05). In the study group, 13 (32.5%) of the pregnant patients did not need treatment. The cesarean rate was significantly higher in the BD group (43.2% vs 20.4% in the control group, p<0.05), and there were no significant differences in median gestational age at the time of delivery (p>0.05). The birth weight of newborns did not differ significantly between the groups. There was no association of BD with maternal morbidity and neonatal complications. Conclusion: In this study, the majority of pregnant with BD did not present clinical exacerbation of their pathology. However, BD may have an adverse influence on pregnancy outcomes. FGR and miscarriage rates were significantly higher in the study group. 相似文献
84.
Jordi Martí 《Molecular simulation》2017,43(2):134-140
Free energy barriers associated with the transfer of an excess proton in water and related to the potentials of mean force in proton transfer episodes have been computed in a wide range of thermodynamic states, from low-density amorphous ices to high-temperature liquids under the critical point for unconstrained and constrained systems. The latter were represented by set-ups placed inside hydrophobic graphene slabs at the nanometric scale allocating a few water layers, namely one or two in the narrowest case. Water–proton and carbon–proton forces were modelled with a Multi-State Empirical Valence Bond method. As a general trend, a competition between the effects of confinement and temperature is observed on the local hydrogen-bonded structures around the lone proton and, consequently, on the mean force exerted by its environment on the water molecule carrying the proton. Free energy barriers estimated from the computed potentials of mean force tend to rise with the combined effect of increasing temperatures and the packing effect due to a larger extent of hydrophobic confinement. The main reason observed for such enhancement of the free energy barriers was the breaking of the second coordination shell around the lone proton. 相似文献
85.
生境分析与预测是受威胁物种有效保护的基础。本研究通过ArcGIS技术平台,利用MaxEnt模型,结合野外调查获得的海南臭蛙(Odorrana hainanensis)66个分布点数据和17个30 m×30 m分辨率的环境变量数据,对该物种在海南岛内的潜在分布区进行预测,并分析其与环境因子之间的关系。结果显示,海南臭蛙的潜在分布区主要位于海拔200~1 200 m的地区,最适宜的海拔范围是600~1 000 m,总分布面积约2 179 km2。海南臭蛙空间分布具有不连续性,其分布区分为三个斑块,尖峰岭所在地为斑块Ⅰ,霸王岭、鹦哥岭和黎母山所在地为斑块Ⅱ,五指山和吊罗山所在地为斑块Ⅲ。适宜生境分析显示,斑块Ⅰ适宜生境面积为218.4 km2,主要分布在尖峰岭中部的三分区、五分区和南部的南崖;斑块Ⅱ适宜生境面积为963.5 km2,主要分布在霸王岭北部的牙琼、南美岭以及鹦哥岭东部的鹦哥嘴、什寒、秀寨岭和黎母山主峰西侧的四分场;斑块Ⅲ适宜生境面积为997.1 km2,主要分布在五指山西部的那罗岭、南部的好定岭和吊罗山中部的度假村、白水岭以及研究区东部的牛上岭。环境变量分析显示,海拔是影响海南臭蛙分布的最主要环境因子,其次是坡度、距水源距离、归一化植被指数(NDVI)和年降水量,温度、湿度和日照对海南臭蛙的分布影响较小。 相似文献
86.
目的探讨不同方式干预孕期运动与妊娠期糖代谢异常的关系及对妊娠结局的影响。方法将300例孕14周单胎孕妇按阶段分为两组各150例,干预组对孕妇进行评估,建立孕妇档案,孕期通过个体化运动干预,给予孕妇个体化、具体的适度运动处方及给予督导规律运动;对照组采用传统的产前检查及常规护理。观察比较两组孕妇血糖变化、体重增长及妊娠结局。结果干预组空腹,餐后2h血糖值,妊娠末期体重,发生糖代谢异常,早产儿、新生儿窒息、巨大儿以及剖宫产率均低于对照组,差异有统计学意义(P0.05)。结论通过个体化护理对孕期运动进行干预,有效控制血糖值,降低母婴并发症的发生。 相似文献
87.
Korotkov SM Emel'yanova LV Yagodina OV 《Journal of biochemical and molecular toxicology》2008,22(3):148-157
We studied action of inorganic phosphate (P(i)) on toxic effects of Tl+ in isolated rat liver mitochondria. This is a convenient model to study the toxicity of heavy metals. P(i) markedly retarded contraction of energized mitochondria swollen in the TlNO3 medium and even stronger stimulated swelling and state 4 of succinate-energized mitochondria in the TlNO3 medium. A valinomycin-induced decrease of K+-diffusion potential was also accelerated by Tl+ in the presence of P(i). The mitochondrial permeability transition pore in the medium containing Ca2+, TlNO3, and nitrates of univalent cations was distinctly stimulated by P(i). However, P(i) did not affect both the Tl+-stimulated swelling of nonenergized mitochondria in the TlNO3 medium and swelling of energized mitochondria in the Tl acetate medium. Respiration stimulated by 2,4-dinitrophenol and monoamine oxidase activity of energized mitochondria were not affected by Tl+ regardless of the presence of P(i). We suggested that stimulation by P(i) of toxic action of Tl+ in mitochondria and cells could be due to even greater enhancement of uncoupling of mitochondria as shown by an additional increase of swelling and state 4, and in the greater probability of opening of MPTP in the presence of P(i) and Ca2+. 相似文献
88.
89.
Apostolos Siapatis Marianna Giannoulaki Vasilis D. Valavanis Andreas Palialexis Eudoxia Schismenou Athanassios Machias Stylianos Somarakis 《Hydrobiologia》2008,612(1):281-295
The invasive ctenophore Mnemiopsis leidyi was accidentally introduced into the Black Sea in the early 1980s and it was first sighted in the Aegean Sea (Eastern Mediterranean)
in the early 1990s. This article presents a first attempt to develop a predictive spatial model based on M. leidyi presence data and satellite environmental data from the Aegean Sea during early summer, in order to identify those areas
in the Greek Seas and the entire Mediterranean basin that could serve as potential habitat for the species. Generalized additive models (GAM) were applied. The final GAM model indicated higher probability of finding M. leidyi present in depths of 65–135 m and sea surface temperature values of 21–25°C. Furthermore, the significant interaction between
photosynthetically active radiation (PAR) and sea level anomaly (SLA) indicated a higher probability of M. leidyi presence in low values of PAR and SLA. In the next step, the final GAM was applied in a prediction grid of mean monthly satellite
values for June 2004–2006 in order to estimate probability of M. leidyi presence in the Hellenic Seas and the whole Mediterranean basin at a GIS resolution of 4 km. In the Aegean Sea, species potential
habitat included areas influenced by the Black Sea Water (e.g. Thracian Sea, Limnos-Imvros plateau), gulfs that are affected
by river runoffs, such as the Thermaikos, Strymonikos and Patraikos gulfs, or areas with strong anthropogenic influence such
as the Saronikos gulf. Areas with the same environmental conditions as those in Aegean Sea have been indicated in certain
spots of the Levantine Sea as well as in coastal waters of Egypt and Libya, although their spatial extent varied largely among
years examined. However, the occurrence of conditions that are linked to high probability of M. leidyi presence does not necessarily mean that these areas can support successful reproduction, high population or bloom levels,
since these depend on a combination of temperature, salinity, food availability and the abundance of predators.
Guest editor: V. D. Valavanis
Essential Fish Habitat Mapping in the Mediterranean 相似文献
90.
Eudoxia Schismenou Marianna Giannoulaki Vasilis D. Valavanis Stylianos Somarakis 《Hydrobiologia》2008,612(1):201-214
Anchovy and round sardinella are two important small pelagic species in the Mediterranean that spawn during the summer period.
This is a first attempt to model and predict the two species’ potential spawning habitats in this area. Generalized additive
models (GAMs) were constructed based on satellite environmental variables and presence/absence egg data, available from ichthyoplankton
surveys conducted in the North Aegean Sea during early summer (June 2003–2006). These models were subsequently used to predict
the probability of anchovy and round sardinella spawning in the Greek Seas as well as the entire Mediterranean and Black Sea
during the same month of the year. The interaction of bottom depth and chlorophyll explained most of the deviance in the presence/absence
GAMs of both species, indicating spawning over continental shelf areas with increased surface chlorophyll values. Round sardinella
spawned closer to coast than anchovy. Predicted potential spawning areas for anchovy and round sardinella in unsampled areas
of the Greek Seas and the entire Mediterranean and Black Sea were in good agreement with existing information on the distribution
and extent of the spawning grounds, especially for anchovy. Modeling the species’ reproductive activity in relation to easily
accessible environmental information and applying the models in a predictive way could be an initial, low-cost step to designate
potential spawning fish habitats.
Guest editor: V. D. Valavanis
Essential Fish Habitat Mapping in the Mediterranean 相似文献