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Dynamic analysis of a predator-prey model of Gause type with Allee effect and non-Lipschitzian hyperbolic-type functional response

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International Journal of Biomathematics 2024年第1期17卷 81-112页

作者： Liliana Puchuri Orestes Bueno Pontificia universidad Catolica del Peri Av.Universitaria 1801 San MiguelLima 15088Peru universidad del pacifico Jr.Gral Luis Sanchez Cerro 2141 Jesus MariaLima 15072Peru

In this work,we study a predator-prey model of Gause type,in which the prey growth rate is subject to an Allee effect and the action of the predator over the prey is determined by a generalized hyperbolic-type functional response,which is neither differentiable nor locally Lipschitz at the predator *** kind of functional response is an extension of the so-called square root functional response,used to model systems in which the prey have a strong herd *** study the behavior of the solutions in the first quadrant and the existence of limit *** prove that,for a wide choice of parameters,the solutions arrive at the predator axis in finite *** also characterize the existence of an equilibrium point and,when it exists,we provide necessary and sufficient conditions for it to be a center-type *** fact,we show that the set of parameters that yield a center-type equilibrium,is the graph of a function with an open *** also prove that any center-type equilibrium is stable and it always possesses a supercritical Hopf *** particular,we guarantee the existence of a unique limit cycle,for small perturbations of the system.

关键词： Predator-prey models Gause models Allee effect non-differentiable functional response

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Evaluation of Early Action Mechanisms in Peru Regarding Preparedness for El Nino

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International Journal of Disaster Risk Science 2019年第4期10卷 493-510页

作者： Julio Aguirre Daniel De La Torre Ugarte Juan Bazo Paulo Quequezana Mauricio Collado Department of Economics Universidad del Pacifico15072 LimaPeru Red Cross Red Crescent Climate Centre 2502 KC The HagueThe Netherlands Centro de Investigacion de Riesgo Resiliencia y Cambio Climatico(CIRCA)Universidad Tecnologica del Peru(UTP)15046 LimaPeru

In this article,we provide an impact evaluation of an intervention in Peru regarding preparedness for El Nino impacts in Picsi District of Chiclayo Province in Peru’s northwestern coastal Lambayeque *** effort involved the provision of special kits that reduce the potential damage to homes as a consequence of rainfall and floods associated with an El Nino-Southern Oscillation *** was collected in 2016 when this Forecast-based Financing early action was activated by an El Nino forecast,and after a coastal El Nino actually struck in *** dual database permits us to estimate the impact of the intervention on the damage level of homes by comparing those homes supported by the program with those homes not receiving pilot-program *** comparison is achieved by using propensity score matching techniques,which identify the most comparable homes to the ones that were supported by the *** main findings of the study suggest a positive impact of the program in terms of its effectiveness in mitigating the damage caused by the 2017 El Ni?*** results suggest a drop in the scale of house damage(less damage)by around 63%for a home that received the modular kit *** considering other specifications of the model,the decrease in the scale of house damage improves up to approximately 66%.

关键词： Early warning Early action El NinoSouthern Oscillation Forecast-based Financing Matching propensity score Perú Red Cross

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Shareholder internationality and importing activities of emerging market firms

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Frontiers of Business Research in China 2020年第3期14卷 383-402页

作者： Pei Wang William Gonzalo Vega Salas Business School Renmin University of ChinaBeijing 100872China universidad del pacifico Av.Salaverry 2020Jesus MariaLimaPeru

In light of the increasing efforts made by emerging market firms to engage in international business through importing activities,identifying the characteristics that motivate importing busi ness and con tribute to its success is practically and theoretically *** upon a knowledge-based view(KBV),we examine how the shareholder internationality affects a firm's importing *** hypothesize that the shareholder internationality can facilitate a firm's import initiati on and con tribute to the diversity of importing countries of ***,the divergence of shareholders'nationality backgrounds may hinder import initiation,but motivate importing from dispersed countries of origin during the import development process.A longitudinal analysis of Colombian firms supports our hypotheses.

关键词： Shareholder internationality Importing Knowledge-based view(KBV) Emerging markets Colombia International business

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Mercury levels in human population from a mining district in Western Colombia

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Journal of Environmental Sciences 2018年第6期30卷 83-90页

作者： Harry Gutiérrez-Mosquera S.B.Sujitha M.P.Jonathan S.K.Sarkar Fairy Medina-Mosquera Helcias Ayala-Mosquera Gladis Morales-Mira Laura Arreola-Mendoza Facultad de Ingenieria Universidad Tecnologica del Choco Carrera 22 No.18B-10 Quibdo Colombia Centro Interdisciplinario de Investigaciones y Estudios sobre Medio Ambiente y Desarrollo (CIIEMAD) Instituto Politecnico Nacional (IPN) Calle 30 de junio de 1520 Barrio la Laguna Ticomdn Del. Gustavo A. Madero C.P.07340 Ciudad de Mexico Mexico Department of Marine Science University of Calcutta 35 Ballygunge Circular Road Calcutta 700 019 India Instituto de Investigaciones Ambientales del pacifico (IIAP) Carrera 6 No. 37-39 quibdo Colombia Facultad de Ingenieria Uniuersidad de Medellin Carrera 87 No. 30-65 Medellin Colombia

A biomonitoring study was carried out to examine the adverse impacts of total mercury in the blood（HgB）, urine（Hg U） and human scalp hair（HgH） on the residents of a mining district in Colombia. Representative biological samples（scalp hair, urine and blood） were collected from volunteered participants（n = 63） to estimate the exposure levels of THg using a Direct mercury analyzer. The geometric mean of THg concentrations in the hair,urine and blood of males were 15.98 μg/g, 23.89 μg/L and 11.29 μg/L respectively, whereas the females presented values of 8.55 μg/g, 5.37 μg/L and 8.80 μg/L. Chronic urinary Hg（HgU）levels observed in male workers（32.53 μg/L） are attributed to their long termed exposures to inorganic and metallic mercury from gold panning activities. On an average, the levels of THg are increasing from blood（10.05 μg/L） to hair（12.27 μg/g） to urine（14.63 μg/L）.Significant positive correlation was found between hair and blood urinary levels in both male and female individuals. Thus the present biomonitoring investigation to evaluate the Hg levels and associated health issues would positively form a framework for further developmental plans and policies in building an ecofriendly ecosystem.

关键词： Humans Mercury Gold panning Biomarkers Toxicity Colombia

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Spatio-temporal co-occurrence of hotspots of tuberculosis, poverty and air pollution in Lima, Peru

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Infectious Diseases of Poverty 2020年第2期9卷 84-89页

作者： Gabriel Carrasco-Escobar Alvaro Schwalb Kelly Tello-Lizarraga Percy Vega-Guerovich Cesar Ugarte-Gil Health Innovation Lab Instituto de Medicina Tropical Alexander von HumboldtUniversidad Peruana Cayetano HerediaLimaPeru Division of Infectious Diseases Department of MedicineUniversity of California San DiegoLa JollaCAUSA Instituto de Medicina Tropical Alexander von Humboldt Universidad Peruana Cayetano HerediaLimaPeru School of Public Health and Administration Universidad Peruana Cayetano HerediaLimaPeru School of Economics and Finance Universidad del PacificoLimaPeru School of Medicine Universidad Peruana Cayetano HerediaLimaPeru TB Centre London School of Hygiene and Tropical MedicineLondonUK

Growing evidence suggests pollution and other environmental factors have a role in the development of tuberculosis(TB),however,such studies have never been conducted in *** the association between air pollution and specific geographic areas,our objective was to determine the spatial distribution and clustering of TB incident cases in Lima and their co-occurrence with clusters of fine particulate matter(PM2.5)and *** found co-occurrences of clusters of elevated concentrations of air pollutants such as PM2.5,high poverty indexes,and high TB incidence in *** findings suggest an interplay of socio-economic and environmental in driving TB incidence.

关键词： Tuberculosis Hotspots Air pollution

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Water as the Pore Former in the Synthesis of Hydrophobic PVDF Flat Sheet Membranes for Use in Membrane Distillation

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Hydro Science & Marine Engineering 2019年第2期1卷 1-9页

作者： Lebea NNthunya Leonardo Gutierrez Edward NNxumalo Sabelo DMhlanga Department of Chemical Metallurgical and Material EngineeringTshwane University of TechnologyPrivate Bag x680Pretoria0001South Africa Particle and Interfacial Technology Group Department of Applied Analytical and Physical ChemistryGhent UniversityCoupure Links 6539000 GhentBelgium Facultad del Mar y Medio Ambiente Universidad del PacificoGuayaquilEcuador Nanotechnology and Water Sustainability Research Unit College of ScienceEngineering and TechnologyUniversity of South AfricaFlorida1709JohannesburgSouth Africa DST/MINTEK Nanotechnology Innovation Centre Strijdom ParkRandburg2125JohannesburgSouth Africa

Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive *** this study,flat sheet PVDF membranes were synthesized using phase inversion and water as the pore ***,the water added in the casting solution improved the membrane pore sizes;where the maximum pore size was 0.58μ***,the incorporation of f-SiO2NPs in the membrane matrix considerably enhanced the membrane ***,the membrane contact angles increased from 96°to 153°.Additionally,other parameters investigated were mechanical strength and liquid entry pressure(LEP).The maximum recorded values were 2.26 MPa and 239 kPa,*** modified membranes(i.e.,using water as the pore former and f-SiO2NPs)were the most efficient,showing maximum salt rejection of 99.9%and water flux of 11.6 LMH;thus,indicating their capability to be used as efficient materials for the recovery of high purity water in MD.

关键词： Direct contact membrane distillation PVDF flat sheet membranes Superhydrophobic silica nanoparticles Water as the pore former

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