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Search Results: 1 - 10 of 167774 matches for " E. Gorla "
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The general hyperplane section of a curve
E. Gorla
Mathematics , 2003,
Abstract: In this paper, we discuss some necessary and sufficient condition for a curve to be arithmetically Cohen-Macaulay, in terms of its general hyperplane section. We obtain a characterization of the degree matrices that can occur for points in the plane that are the general hyperplane section of a non arithmetically Cohen-Macaulay curve of P^3. We prove that almost all the degree matrices with positive subdiagonal that occur for the general plane section of a non arithmetically Cohen-Macaulay curve of P^3, arise also as degree matrices of the general plane section of some smooth, integral, non arithmetically Cohen-Macaulay curve, and we characterize the exceptions. We give a necessary condition on the graded Betti numbers of the general hyperplane section of an arithmetically Buchsbaum, (non arithmetically Cohen-Macaulay) curve in P^n. For curves in P^3, we show that any set of Betti numbers that satisfies that condition, can be realised as the Betti numbers of the general plane section of an arithmetically Buchsbaum, non arithmetically Cohen-Macaulay curve. We also show that the matrices that arise as degree matrix of the general plane section of an arithmetically Buchsbaum, integral, (smooth) non arithmetically Cohen-Macaulay space curve are exactly those that arise as degree matrix of the general plane section of an arithmetically Buchsbaum, non arithmetically Cohen-Macaulay space curve and have positive subdiagonal. We also prove some bounds on the dimension of the deficiency module of an arithmetically Buchsbaum space curve, in terms of the degree matrix of the general plane section of the curve.
Variables ambientales registradas por sensores remotos como indicadores de la distribución geográfica de Triatoma infestans (Heteroptera: Reduviidae)
Gorla,David E;
Ecolog?-a austral , 2002,
Abstract: the paper presents an analysis of the geographic distribution of triatoma infestans based on biophysical variables recorded by meteorological satellites. the analysis includes data derived from a temporal fourier analysis of monthly images over a set of 14 derived statistical descriptors of the average, minimum, maximum, variability, amplitude and phase of the air temperature, land surface temperature, medium infrared radiation and a vegetation index remotely sensed by the avhrr. temporal series covered the period 1982-2000, and the area from panamá to tierra del fuego. the analysis of individual variables showed that the annual phase of the normalised difference vegetation index identifies correctly 80% presence and absence sites of triatoma infestans. the analysis confirms the importance of temperature (especially air temperature) for triatoma infestans distribution, as 7 (out of 14) statistical descriptors associated with air temperature identified correctly >70% of presence and absence sites. a stepwise linear discriminant analysis showed that a function with six statistical descriptors (four of them associated with air temperature, one associated with medium infrared radiation, and one with the vegetation index) identified correctly 90% of presence and absence sites of triatoma infestans. the analysis shows the important association between the environmental variables studied at the continental scale and the distribution of a strictly domestic and haematophagous species. the approach could be useful for large scale studies of the distribution of other species with more direct and causal relation with vegetation and climate than triatoma infestans.
Eficiencia de captura de adultos de Lepidoptera plagas de maíz (Zea mays) y de soja (Glicine max) en trampas de luz de vapor de mercurio y de luz negra en la región central de la provincia de Córdoba (Argentina)
Sagadin,Ileana M; Gorla,David E;
Ecolog?-a austral , 2002,
Abstract: the larvae of lepidoptera are very important crop pests in central córdoba province (argentina), because of the yield losses they produce on corn and soybean. we compared the efficiency of two light traps, one with a 125 w mercury vapour lamp hpl type and other with a 15-w blacklight lamp. moth catches were counted 1-3 times/week, from december 1997 to december 2000. the comparison of trap efficiency for each species was carried out with the slope of the relationship between week catches obtained for each trap. the mercury vapour trap was more efficient for most of the species, with some variations depending on the period that was analysed. there were no significant differences between traps for agrotis malefida and agrotis ipsilon, and the blacklight trap was more efficient for helicoverpa zea, spodoptera frugiperda and spilosoma virginica. for 8 out of the 18 collected species the efficiency of the traps depended on the species density.
Variación geográfica de la abundancia poblacional de Delphacodes kuscheli (Fennah) en la región central de Argentina
Grilli,Mariano P; Gorla,David E;
Ecolog?-a austral , 2002,
Abstract: delphacodes kuscheli is the vector of the río cuarto corn disease, which affects maize in central argentina. this disease is endemic of rio cuarto department in córdoba province. preliminary studies indicate that the insect is present in córdoba, la pampa, san luis, santa fe and buenos aires provinces, but there are few studies on the abundance in these places. previous research showed that delphacodes kuscheli arrives to maize plots from distant sources, and that there is a difference in the abundance of delphacodes kuscheli in the endemic area and outside it. in this work we study the geographic variations of the population abundance of delphacodes kuscheli along a transect that crosses the endemic area to verify whether there is a difference between the vector population dynamics within and outside the endemic area. samples of dispersing individual were collected during three years by using sticky traps at two different heights. the samples were taken in eight sampling sites between the localities of manfredi (córdoba) and mercedes (san luis). dispersive individuals of delphacodes kuscheli were more abundant in the endemic area than outside it. the dispersive population captured with low traps had a higher proportion of females, but there were no differences at high traps. the correlation of density changes observed in high traps decreased with distance between sampling sites, but there was no relationship for low traps. it is discussed how these results could indicate that delphacodes kuscheli is a species highly adapted to live in unstable habitats.
Cryptanalysis of the CFVZ cryptosystem
J. J. Climent,E. Gorla,J. Rosenthal
Computer Science , 2006,
Abstract: The paper analyzes a new public key cryptosystem whose security is based on a matrix version of the discrete logarithm problem over an elliptic curve. It is shown that the complexity of solving the underlying problem for the proposed system is dominated by the complexity of solving a fixed number of discrete logarithm problems in the group of an elliptic curve. Using an adapted Pollard rho algorithm it is shown that this problem is essentially as hard as solving one discrete logarithm problem in the group of an elliptic curve.
Experimental evaluation of insecticidal paints against Triatoma infestans (Hemiptera: Reduviidae), under natural climatic conditions
Ivana Amelotti, Silvia S Catalá, David E Gorla
Parasites & Vectors , 2009, DOI: 10.1186/1756-3305-2-30
Abstract: The study was based on an experimental design that included two groups treated with an organophosphate (Inesfly 5A IGR?) and a pyrethroid (Inesfly 5A IGR NG?) formulations of the paint, that were applied on wood, cement blocks and adobe bricks under natural climatic conditions. A third group was an untreated control. Both paint formulations showed very long residual activity, producing mortality of 84% and 98% (pyrethroid and organophosphate formulations, respectively) after 12 months of the paint application. After eight months, nymphs exposed during 6 hours to the painted surfaces with the pyrethroid and organophosphate formulations showed 81.33% and 100% mortality, respectively.The organophosphate- and pyrethroid-based insecticidal paints showed a very long residual activity on the mortality of fourth instar nymphs of T infestans, compared with the traditional spraying technique used for the application of pyrethroid insecticides in peridomestic structures of rural houses in the endemic region for Chagas disease in the Gran Chaco of Argentina. The application of the paints by trained personnel of the vector control programmes could be considered as an alternative control tool in areas where the traditional methods have failed or showed low efficacy.Chagas disease or American trypanosomiasis, is an infectious disease caused by Trypanosoma cruzi, transmitted by hematophagous insects of the subfamily Triatominae (Reduviidae). The disease is a major public health concern in Latin America, with estimates of 50000 people dying each year, 10 million people being infected, and around 100 million people being reportedly at risk of infection [1]. Although the disease is endemic in Latin American countries, human migration has spread the disease to other continents, especially North America and Europe [2,3]. In spite of long-term research efforts, there is no available vaccine [4] and treatment after infection is effective only for recent infections [5-7]. The preventive ap
Response of Triatoma infestans to pour-on cypermethrin applied to chickens under laboratory conditions
Amelotti, Ivana;Catalá, Silvia S;Gorla, David E;
Memórias do Instituto Oswaldo Cruz , 2009, DOI: 10.1590/S0074-02762009000300014
Abstract: this article reports the effects of a pour-on formulation of cypermethrin (6% active ingredient) applied to chickens exposed to triatoma infestans, the main vector of chagas disease in rural houses of the gran chaco region of south america. this study was designed as a completely random experiment with three experimental groups and five replicates. third instar nymphs were fed on chickens treated with 0, 1 and 2 cc of the formulation. nymphs were allowed to feed on the chickens at different time intervals after the insecticide application. third-instar nymphs fed on treated chickens showed a higher mortality, took less blood during feeding and had a lower moulting rate. the mortality rate was highest seven days after the insecticide solution application and blood intake was affected until 30 days after the application of the solution.
Daily pattern of flight activity of Aedes albifasciatus in Central Argentina
Ludue?a Almeida, Francisco F.;Gorla, David E.;
Memórias do Instituto Oswaldo Cruz , 1995, DOI: 10.1590/S0074-02761995000500020
Abstract: aedes albifasciatus is an important common mosquito in central argentina. its a confirmed vector of the western equine encephalitis and is responsible for loss of milk production in dairy cattle during peak populations. this paper reports the flight activity pattern of ae. albifasciatus for different seasons, in the southern coast of the mar chiquita lake (central argentina). data were collected by sampling two sites between 1992 and 1993 with cdc traps and human-bait captures. adult mosquito population density, estimated by cdc trapping and human-bait, were highly correlated. however, when compared to other species, the proportion of ae. albifasciatus was higher in human-bait collections. adult female populations were active only when temperature were higher than 6§c. two daily biting peaks were observed (dusk and dawn) during the spring, summer and autumn, and only one peak during winter (around 15:00 pm). adult abundance was significantly correlated (r2= 0.71; p<0.01) with temperature and illumination.
The biology of Aedes (Ochlerotatus) albifasciatus Macquart, 1838 (Diptera: Culicidae) in Central Argentina
Ludue?a Almeida, Francisco F.;Gorla, David E.;
Memórias do Instituto Oswaldo Cruz , 1995, DOI: 10.1590/S0074-02761995000400006
Abstract: aedes albifasciatus is a flood water mosquito ocurring in the southern countries of south america. it is a competent vector of the western equine encephalitis (wee) and causes important losses on milk and beef production in central argentina. field work was carried out from december 1990 to march 1993, on a monthly basis during the dry season and biweekly during the rainy season. larvae were collected using the 'dipping' technique and females with cdc traps baited with co2. field collected larvae were used to build laboratory cohorts, from which basic population parameters were estimated. eggs survived up to six months on dry soil, although there was a linear decrease of viability with time. at 23oc, larval development time was around nine days, and all adults emerged within one week. the estimation of larval development in the laboratory seems to be very near the development on the field, as larvae have been collected on average eight days after a rainfall. egg to adult survival was 83%, with the highest mortality on fourth larval instar (6%). in the laboratory studies, sex proportion among the adults was 1:1, females lived longer than males (median 13 and five days, respectively), and adult survival pattern showed a constant number of individuals dying per unit time. field collected females layed an average of 84 eggs per batch, and completing up to five gonotrophic cycles, suggesting an estimated survival of up to 35-50 days.
Life cycle and reproductive patterns of Triatoma rubrovaria (Blanchard, 1843) (Hemiptera: Reduviidae) under constant and fluctuating conditions of temperature and humidity
Damborsky, Miryam P.;Bar, María E.;Gorla, David;
Revista da Sociedade Brasileira de Medicina Tropical , 2005, DOI: 10.1590/S0037-86822005000500014
Abstract: the aim of this study was to evaluate the temperature and relative humidity influence in the life cycle, mortality and fecundity patterns of triatoma rubrovaria. four cohorts with 60 recently laid eggs each were conformed. the cohorts were divided into two groups. in the controlled conditions group insects were maintained in a dark climatic chamber under constant temperature and humidity, whereas triatomines of the ambiental temperature group were maintained at room temperature. average incubation time was 15.6 days in the controlled conditions group and 19.1 days in the ambiental temperature. in group controlled conditions the time from egg to adult development lasted 10 months while group ambiental temperature took four months longer. egg eclosion rate was 99.1% and 98.3% in controlled conditions and ambiental temperature, respectively. total nymphal mortality in controlled conditions was 52.6% whereas in ambiental temperature was 51.8%. mean number of eggs/female was 817.6 controlled conditions and 837.1 ambiental temperature. fluctuating temperature and humidity promoted changes in the life cycle duration and in the reproductive performance of this species, although not in the species mortality.
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