检索结果-南通市图书馆

Performance assessment of two-dimensional hydraulic models for generation of flood inundation maps in mountain river basins

在线全文

学校读者我要写书评

暂无评论

Water Science and Engineering 2019年第1期12卷 11-18页

作者： juan Pinos luis Timbe Department of Water Resources and Environmental Sciences University of Cuenca

Hydraulic models for the generation of flood inundation maps are not commonly applied in mountain river basins because of the difficulty in modeling the hydraulic behavior and the complex topography. This paper presents a comparative analysis of the performance of four twodimensional hydraulic models (HEC-RAS 2D, Iber 2D, Flood Modeller 2D, and PCSWMM 2D) with respect to the generation of flood inundation maps. The study area covers a 5-km reach of the Santa B-arbara River located in the Ecuadorian Andes, at 2330 masl, in Gualaceo. The model's performance was evaluated based on the water surface elevation and flood extent, in terms of the mean absolute difference and measure of fit. The analysis revealed that, for a given case, Iber 2D has the best performance in simulating the water level and inundation for flood events with 20- and 50-year return periods, respectively, followed by Flood Modeller 2D, HEC-RAS 2D, and PCSWMM 2D in terms of their performance. Grid resolution, the way in which hydraulic structures are mimicked, the model code, and the default value of the parameters are considered the main sources of prediction uncertainty.

关键词： Two-dimensional hydraulic models Flood modeling Flood extent Water surface elevation High mountain river Ecuador

Symmetrization for Fractional Elliptic and Parabolic Equations and an Isoperimetric Application(Dedicated to Haim Brezis,great master of analysis,on his 70th birthday)

在线全文

学校读者我要写书评

暂无评论

Chinese Annals of Mathematics,Series B 2017年第2期38卷 661-686页

作者： Yannick SIRE juan luis VAZQUEZ Bruno VOLZONE johns hopkins university Krieger Hall3401 N.Charles StBaltimoreM D21218USA. departamento de matemticas universidad autnoma de madrid28049 M adridSpain dipartimento di ingegneria universit degli studi di napoli"parthenope"80143 Italia.

This paper develops further the theory of symmetrization of fractional Laplacian operators contained in recent works of two of the authors. This theory leads to optimal estimates in the form of concentration comparison inequalities for both elliptic and parabolic equations. The authors extend the theory for the so-called restricted fractional Laplacian defined on a bounded domain Ω of R^N with zero Dirichlet conditions outside of Ω. As an application, an original proof of the corresponding fractional Faber-Krahn inequality is derived. A more classical variational proof of the inequality is also provided.

关键词： Symmetrization, Fractional Laplacian, Nonlocal elliptic and parabolicequations, Faber-Krahn inequality

Experimental analysis of infragravity waves in two eroded microtidal beaches

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2017年第5期36卷 31-43页

作者： MARIO Conde-Frias luis Otero juan Camilo Restrepo juan Carlos Ortiz Geosciences Research Group GE04 Department of PhysicsUniversidad del NorteBarranquilla 081007Colombia

This work aims to contribute to the characterization and understanding ofinfragravity waves on two beaches with erosion problems. For this reason, we have used an array of ADCP and a pressure sensor to measure wave parameters and pressure inside and outside of the surf zone during the dry and rainy period in the beaches of Galerazamba and Manzanillo del Mar （both dissipative and eroded beaches） located in the Colombian Caribbean coast. Based on these measurements, we have carried out a spectral analysis in order to identify the frequency components that characterize the wave and its energy; thus, we identified the characteristic frequencies of iufragravity waves to finally filter the infragravity signal on each beach in different seasonal periods. Among the results of the Welch spectrum applied to surface elevation time series, we found that, the frequencies＇ energy of the sea-swell band decreases due to bottom friction and wave breaking as the wave approaches the shore, while the frequencies＇ energy of the infragravity band increases significantly. In addition, for the wavelet analysis, we could observe how the energy of the infragravity band, especially the lowest frequencies gain energy as the waves approaches the coast. Furthermore, based on the infragravity wave obtained from the extreme wave event registered during the field campaign we can conclude that the contribution of this signal is important in the erosion problems presented in the beaches of Galerazamba and Manzanillo del Mar. Finally, these results show the need to realize other studies that allow us to understand deeply, the role of infragravity waves on the morphological changes that occurs in these beaches.

关键词： infragravity waves long waves experimental analysis fourier analysis wavelet transform

The political economy of city diplomacy

在线全文

学校读者我要写书评

暂无评论

Economic and Political Studies 2022年第2期10卷 228-249页

作者： juan luis Manfredi-Sanchez Department of International Studies&Journalism University of Castilla-La ManchaToledoSpain

City diplomacy is a major trend in the soft power *** cities face daily political issues deriving from globalisation(such as mass tourism,migration,climate change,and commodifi-cation of culture),they demand for,rather than contesting with a nationstate,an operational reinterpretation of sovereignty ori-ented to solve *** economy approach is a useful method to understand the role of global cities where the nation state has many *** global city establishes rules to influence international legal development and practice,even with-out a traditional legal basis(such as sovereignty,monopoly on violence,and legal exclusivity).As these‘superstar cities’grow,other cities are losing opportunities to develop and take advan-tage of *** risk of inter-urban inequality feeds *** will become the middle power in global political organisations in the future,and political economy will shed light on how power and values operate at the urban level.

关键词： City diplomacy leadership political economy sanctuary city urban agenda

Suspended sediment transport in the Magdalena River(Colombia,South America):Hydrologic regime,rating parameters and effective discharge variability

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2016年第01期31卷 25-35页

作者： Aldemar Higgins juan Camilo Restrepo juan Carlos Ortiz Jorge Pierini luis Otero (UNS-CIC-CCT)

The Magdalena River has the greatest length（1612 km）and drainage area（257400 km2）of any river system in Colombia,and its watershed occupies 24%of the Colombian *** river originates in the Andean Cordillera at an elevation of 3685 m and flows to its mouth in the Caribbean Sea（Bocas de Cenizas）.For this study,information on daily flow discharge（Q）,suspended sediment transport(Qsand mean suspended sediment concentration（Cs）from 1990-2010 for the Magdalena River,based on measurements at the Caiamar gauging station（the closest station to the mouth）,was provided by the Institute of Hydrology,Meteorology and Environmental Studies of Colombia（IDEAM in Spanish）.The mean annual suspended sediment load was 169±73×10～6tyr-1for the period from 1990-1999 and145±47×10～6 t yr1for the period from 2000-2010,amounting to a 14%reduction in the suspended sediment transport rate between the two *** sediment rating curve（Qs=aQb）was also evaluated for these two periods（1990-1999 and 2000-2010）.An analysis of the regression coefficients（a.b）for the two periods showed a decrease in b and an increase in a after 1999,which coincides with a decrease in suspended sediment *** change might be attributed to natural factors,including the accumulation of sediment in the Depresion Momposina and variation in hydro-climatological patterns in the Caribbean *** in effective transport were confirmed using three methods（Log-Normal and Normal distribution,and magnitude-frequency histogram）for the study period.

关键词： Suspended sediment transport Magdalena River Transport regime Effective discharge Sediment rating curve

Reactive oxygen species, nitric oxide and plant cell death associated with caspase-like protease activity during somatic embryogenesis in Fraxinus mandshurica

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Forestry Research 2022年第3期33卷 1005-1017页

作者： Hao Wang Dongyan Zhang juan luis Fernández-Lorenzo Hailong Shen Ling Yang State Key Laboratory of Tree Genetics and Breeding School of ForestryNortheast Forestry UniversityHarbin150040People’s Republic of China Crop Production Department High Polytechnique School of EngineeringSantiago de Compostela UniversityLugoSpain

Programmed cell death occurs in browning explants of Fraxinus mandshurica during somatic embryogenesis, but the underlying mechanism is unclear. In this study, single cotyledons of zygotic embryos of F. mandshurica were used as explants. Mitochondrial structure and function, caspase-3-like protease activity, hydrogen peroxide metabolism, and nitric oxide accumulation induced by high concentrations of sucrose and plant growth regulators were studied. The results show that plant growth regulators induced somatic embryogenesis and also promoted explant browning. High sucrose concentrations had similar effects. High concentrations of sucrose and plant growth regulators led to the accumulation of hydrogen peroxide and nitric oxide which induced changes in mitochondrial structure and function such as modifications in mitochondrial morphology, increased membrane permeability, decreased membrane potential, and the release of cytochrome c into the cytoplasm. An increase in caspase-3-like protease activity triggered programmed cell death in some browning explant cells. During somatic embryogenesis there were increased activities of superoxide dismutase, peroxidase, and catalase, which are associated with hydrogen peroxide metabolism and jointly maintain reactive oxygen species levels. Intracellular nitric oxide synthase and nitrate reductase activities were not significantly correlated with nitric oxide content. Instead, intracellular nitric oxide may be derived from non-enzymatic reactions. Our results indicate that hydrogen peroxide and nitric oxide may function as signals, playing key roles in somatic embryogenesis and programmed cell death of explant cells of F. mandshurica. The interaction between nitric oxide and reactive oxygen species determines the occurrence of programmed cell death in explant cells;somatic embryogenesis and programmed cell death are positively regulated by hydrogen peroxide. However, the regulation of nitric oxide is complex.

关键词： Manchurian ash Somatic embryogenesis Programmed cell death Mitochondria Reactive oxide species Nitric oxide

The Role of the Solar Cycle in the Relationship Between the North Atlantic Oscillation and Northern Hemisphere Surface Temperatures

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2007年第2期24卷 191-198页

作者： Laura DE LA TORRE luis GIMENO juan Antonio AEL Raquel NIETO Universidad de Vigo Facultad de Ciencias de Ourense 32004OurenseSpain

The North Atlantic Oscillation （NAO） is one of the leading modes of climate variability in the Northern Hemisphere. It has been shown that it clearly relates to changes in meteorological variables, such as surface temperature, at hemispherical scales. However, recent studies have revealed that the NAO spatial pattern also depends upon solar forcing. Therefore, its effects on meteorological variables must vary depending upon this factor. Moreover, it could be that the Sun affects climate through variability patterns, a hypothesis that is the focus of this study. We find that the relationship between the NAO/AO and hemispheric temperature varies depending upon solar activity. The results show a positive significant correlation only when solar activity is high. Also, the results support the idea that solar activity influences tropospheric climate fluctuations in the Northern Hemisphere via the fluctuations of the stratospheric polar vortex .

关键词： solar activity North Atlantic Oscillation Arctic Oscillation Northern Hemisphere surface temperature

Implications of denitrification in the ecological status of an urban river using enzymatic activities in sediments as an indicator

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2019年第1期31卷 255-268页

作者： Jessica Unda-Calvo Miren Martínez-Santos Estilita Ruiz-Romera juan luis Lechuga-Crespo Department of Chemical and Environmental Engineering University of the Basque Country

A better understanding of the effects of a number of environmental factors on denitrification is vital for analyzing its role as nitrogen sink and providing deeper knowledge about the ecological status of a nitrate-rich ecosystem. Since few studies have addressed the occurrence and implications of denitrification in river sediments, and complexity of interactions among all these environmental factors makes comprehension of the process difficult, the potential of sediments from the Deba River to attenuate nitrate excess through denitrification was investigated. For this purpose, we adapted an in vitro method to measure activities of two enzymes contributing to the entire multiple-step nitrate reduction: Nitrate Reductase and Nitrite Reductase. The environmental features that influence both or single enzymatic activities were identified as oxygen availability,regulated directly by the moisture content or indirectly through the aerobic respiration,organic matter and nitrate content of sediments, and electrical conductivity and exchangeable sodium percentage of water. Additionally, our results showed that Nitrate Reductase catalyzes the principal limiting step of denitrification in sediments. Therefore,taking this enzymatic activity as an indicator, the southern part of the Deba River catchment presented low potential to denitrify but nitrate-limited sediments, whereas the middle and northern parts were characterized by high denitrification potential but nitraterich sediments. In general, this study on denitrifying enzymatic activities in sediments evaluates the suitability of the management of the effluents from wastewater treatment plants and municipal sewages to ensure a good ecological status of the Deba River.

关键词： Urban catchment Sediments Denitrification Enzymatic activity Ecological status

COVID-19 and Indirect Liver Injury:A Narrative Synthesis of the Evidence

在线全文

学校读者我要写书评

暂无评论

Journal of Clinical and Translational Hepatology 2021年第5期9卷 760-768页

作者： Francisco Idalsoaga Gustavo Ayares juan Pablo Arab luis Antonio Díaz Departamento de Gastroenterología Escuela de MedicinaPontificia Universidad Católica de ChileSantiagoChile Centro de Envejecimiento y Regeneración(CARE) Facultad de Ciencias BiológicasPontificia Universidad Católica de ChileSantiagoChile

The liver is frequently affected by severe acute respiratory syndrome-coronavirus 2(SARS-CoV-2)*** most common manifestations are mildly elevated alanine aminotransferase and aspartate aminotransferase,with a prevalence of 16-53%among *** with severe coronavirus disease 2019(COVID-19)seem to have higher rates of acute liver dysfunction,and the presence of abnormal liver tests at admission signifies a higher risk of severe disease during *** with chronic liver diseases also have a higher risk of severe disease and mortality(mainly seen in patients with metabolic-associated fatty liver disease).Several pathways of damage have been proposed in the liver involvement of COVID-19 patients;although,the end-cause is most likely *** liver tests have been attributed to the expression of angiotensin-converting enzyme 2 receptors in SARS-CoV-2 *** enzyme is expressed widely in cholangiocytes and less in *** factors attributed to liver damage include drug-induced liver injury,uncontrolled release of proinflammatory molecules(“cytokine storm”),pneumonia-associated hypoxia,and direct damage by the *** steatosis,vascular thrombosis,fibrosis,and inflammatory features(including Kupffer cell hyperplasia)are the most common liver histopathological findings in deceased COVID-19 patients,suggesting important indirect mechanisms of liver *** this translational medicinebased narrative review,we summarize the current data on the possible indirect mechanisms involved in liver damage due to COVID-19,the histopathological findings,and the impact of these mechanisms in patients with chronic liver disease.

关键词： COVID-19 SARS-CoV-2 Liver hepatitis Liver injury Novel coronavirus