Limit cycles for a class of quintic Z6−\mathbb{Z}_6-equivariant systems without infinite critical points

We analyze the dynamics of a 4-parameter family of planar ordinary differential equations, given by a polynomial of degree 5 that is equivariant under a symmetry of order 6. We obtain the number of limit cycles as a function of the parameters, and provide criteria for proving in some cases uniqueness and hyperbolicity of the limit cycle surrounding either 1, 7 or 13 critical points, the origin being always one of these points. The method used is the reduction of the problem to an Abel equation

Preselection area of arepresentative aerobjological sampling station of a tropical valley

In order to search an uniform criteria for sampling aerobiological particles, three sites were selected along the valley of Caracas. The distribution of vegetation, topographical and meteorological parameters were monitored. Pollen and spores were collected at each site during 24 hr at 6 min-intervals with a Rotorod sampler. Pollen counts were similar in all sites and much less abundant than spores. Cladosporium was the most abundant spore and grass pollen represented more than 50% of the pollen grains. Results showed that the three sites could be selected al luitable sampling area for airborne pollen and spores. Nevertheless, we recommend the selection of the most accesible and central site for a long-term sampling

Common airborne Allergens and their clinical relevance in the Caracas valley

In order lo detennine the sequential prevalence of pollen gratns and fungi spores in the city of Caracas by the volumetric melhod or collection and its effect on the populaton al. risk the first mutidisciplinary team of aerobiologtcal research was structured throegh a prolocol designed for fjve experimental stages namely: a) Determination of the climatological parameters: temperature relative humidity, speed and wind direciotion, precipitation and atmospheric stabllity, through simultaneous records of' meteorological status located in the metropolitan area of Caracas: b) Collection, identification. Classification and determination of the local distribution of the most important pollen grains existing in the zone under study: c) Collection, identification and classification of the most important fungi spores in the area; d) Preparation of the first pollinic calendar of Caracas and e) Evaluation of possible implication of the environment and the response through the IgE antibody in the selected patients in the area under study. Our results show: 1) The climatic conditions existing during the sampling period coincide with the analysis of the last 20 years in the Valley of 'Caracas. 2) The Venezuelan Central University (UCV) station was elected as the most representative point for pemanent sampling. 3) An ideal statistical method is obtained in order lo determine the spatial arrangement in the sampler rod of' a dense type of' fungi spores typical of the area under study. 4) The fistpollinic calendar of Caracas was structured and 5) A seasonal tendency of the IgE response is shown. These results suggest an evident interrelation between the suggested concept of poliseasonality and antigenic polysensitization. and between individual seasonality with a specific reactivity ando, finally, between tropical mixed seasonality with the expressíon of combíned respíratory pathologíes ín our environment

Distribution and ecology of parent taxa of pollen lodged within the Latin American Pollen Database

The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The 'dictionary' describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.Fil: Marchant, Robert. University of Amsterdam; Países BajosFil: Almeida, Lucía. Universidad Nacional Autónoma de México; MéxicoFil: Behling, Hermann. Center for Tropical Maritime Ecology; AlemaniaFil: Berrio, Juan Carlos. University of Amsterdam; Países BajosFil: Bush, Mark. West University Boulevard; Estados UnidosFil: Cleef, Antoine. University of Amsterdam; Países BajosFil: Duivenvoorden, Joost. University of Amsterdam; Países BajosFil: Kappelle, Maarten. Instituto Nacional de Biodiversidad (INBio); Costa RicaFil: De Oliveira, Paulo. Universidade de Sao Paulo; BrasilFil: de Oliveira, Ary Teixeira. Universidade Federal de Lavras; BrasilFil: Lozano García, Socorro. Universidad Nacional Autónoma de México; MéxicoFil: Hooghiemstra, Henry. University of Amsterdam; Países BajosFil: Ledru, Marie Pierre. Instituto de Geociencias; BrasilFil: Ludlow Wiechers, Beatriz. Universidad Nacional Autónoma de México; MéxicoFil: Markgraf, Vera. University of Colorado; Estados UnidosFil: Mancini, Maria Virginia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología y Palinología; ArgentinaFil: Paez, Marta Mercedes. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología y Palinología; ArgentinaFil: Prieto, Aldo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología y Palinología; ArgentinaFil: Rangel, Olando. Universidad Nacional de Colombia; ColombiaFil: Salgado Labouriau, Maria Lea. Universidade do Brasília; Brasi