Análisis paleoambiental sobre la base del estudio malacológico del sitio Paso Otero 1 (región pampeana, Argentina); Paleoenvironmental Analysis of the Malacological Studies Conducted at paso Otero 1 Site (Pampean Region, Argentina) Steffan, Pamela Guillermina Se infieren las condiciones paleoclimáticas y paleoambientales en Paso Otero 1 durante el Holoceno, particularmente desde los ca. 4800 AP a 2900 años AP. Paso Otero 1 está ubicado en el área del curso medio del río Quequén Grande (área Interserrana Bonaerense, región pampeana). El análisis de la composición de la fauna de gasterópodos comprende distintos aspectos: diversidad de especies representadas en el muestreo, medidas de abundancia relativa de individuos por especie y distribución de frecuencias por niveles muestreados. Los resultados indican una mayor humedad hacia los 4800 años AP y un ascenso en la temperatura hacia los 2900 años AP. Estos análisis permitieron evaluar la información paleoambiental de los gasterópodos fósiles y aportar datos acerca de las condiciones ambientales locales.; In this paper, paleoclimatic and paleoenvironmental conditions at Paso Otero 1 are inferred for the Holocene, particularly from ca. 4800 to 2900 BP. Paso Otero 1 is located in the area of the middle basin of the Quequén Grande river (Interserrana Bonaerense area, Pampean region). Analysis of the faunal composition of gastropod fauna included different aspects: diversity of represented species in the sample, measurements of relative abundance of individuals by species, and the distribution of frequencies for sampled levels. The results indicate greater humidity toward ca. 4800 BP and an increase in temperature toward 2900 BP. The analyses enable the environmental information of the fossil gastropods to be evaluated, contributing data on local environmental conditions.

Explosion time in stochastic differential equations with small diffusion Groisman, Pablo Jose; Rossi, Julio Daniel We consider solutions of a one dimensional stochastic differential equations that explode in finite time. We prove that, under suitable hypotheses, the explosion time converges almost surely to the one of the ODE governed by the drift term when the diffusion coefficient approaches zero.

The best Sobolev trace constant in a domain with oscillating boundary Fernandez Bonder, Julian; Orive, Rafael; Rossi, Julio Daniel In this paper we study homogenization problems for the best constant for the Sobolev trace embedding W1, p (Ω) {right arrow, hooked} Lq (∂ Ω) in a bounded smooth domain when the boundary is perturbed by adding an oscillation. We find that there exists a critical size of the amplitude of the oscillations for which the limit problem has a weight on the boundary. For sizes larger than critical the best trace constant goes to zero and for sizes smaller than critical it converges to the best constant in the domain without perturbations.

On the embedding problem for 2+s4 representations Pacetti, Ariel Martín Let 2+S4 denote the double cover of S4 corresponding to the element in H2(S4, Z/2Z) where transpositions lift to elements of order 2 and the product of two disjoint transpositions to elements of order 4. Given an elliptic curve E, let E[2] denote its 2-torsion points. Under some conditions on E elements in H1(GalQ, E[2])\{0} correspond to Galois extensions N of Q with Galois group (isomorphic to) S4. In this work we give an interpretation of the addition law on such fields, and prove that the obstruction for N having a Galois extension N˜ with Gal(N/˜ Q) 2+S4 gives a homomorphism s+ 4 : H1(GalQ, E[2]) → H2(GalQ, Z/2Z). As a corollary we can prove (if E has conductor divisible by few primes and high rank) the existence of 2-dimensional representations of the absolute Galois group of Q attached to E and use them in some examples to construct 3/2 modular forms mapping via the Shimura map to (the modular form of weight 2 attached to) E.

Los Salesianos y la conquista de la Patagonia: desde Don Bosco hasta sus primeros textos escolares e historias oficiales; The Salesians and the Conquest of the Patagonia: From Don Bosco to their first school texts and official history records Nicoletti, Maria Andrea La Congregación Salesiana de Don Bosco llegó a la Argentina en 1875 con la intención de evangelizar “infieles” en la Patagonia, mediante un plan concreto de adoctrinamiento y educación para los pueblos originarios. Para ello, Don Bosco formuló un proyecto en el que el daba cuenta acerca de la situación violenta entre los indígenas y el Estado argentino en Patagonia. Tras algunos intentos fallidos de ingresar a la Patagonia, los Salesianos acompañan al ejército de Julio Roca en 1879. Este suceso fue narrado por los primeros misioneros como un hecho cruel y violento perpetrado por el ejército, al que criticaron fuertemente, narrando la situación de marginalidad, pobreza y exclusión de los sobrevivientes. Sin embargo, justificaron esta acción en función de la “acción civilizadora” del Estado y la “necesidad” de cristianización de sus habitantes. Estas primeras fuentes se fueron reinterpretando en distintos textos salesianos: desde los informes internos (Anales) hasta sus propios los textos escolares y sus narraciones históricas. Cada fuente seleccionó y justificó esta información de primera mano de acuerdo al lector, el contexto historiográfico y a su propia reelaboración sobre este tema clave: la violencia y la evangelización.; The Salesian Congregation of Don Bosco arrived in Argentina in 1875 with the aim of evangelizing “infidels” in the Patagonia with a specific plan of indoctrination and education for the originary people. For this purpose, Don Bosco formulated a project where he stated the violent situation between the indigens and the Argentinean state in Patagonia. After some unsuccessful attempts of entering the Patagonia, the Salesians went along with the army of Julio Roca in 1879. This event was narrated by the first missioners as a cruel and violent action perpetrated by the army, which they criticized heavily, telling about the situation of marginality, poverty and exclusion of the survivors. However, they justified this action according to the “civilizing action” of the State and the “necessity” of Christianization of its inhabitants. These first sources have been reinterpreted in different Salesian texts: from the internal reports (Annals) to their own school texts and historical narrations. Each source selected and justified this first-hand information according to the reader, the historiographical context and their own re-elaboration of this key subject: violence and evangelization.

Hb Alesha [β67(E11)Val→Met, GTG→ATG] in an Argentinean girl Eberle, Silvia Eandi; Noguera, Nelida Ines; Sciuccati, Gabriela; Bonduel, Mariana; Díaz, Lilian; Staciuk, Raquel; Targovnik, Hector Manuel; Feliu Torres, Aurora Hb Alesha is caused by a GTG>ATG mutation at codon 67 of the b-globin gene, resulting in abnormal beta-globin chains in which the normal beta67(E11) valine is changed to methionine. This hemoglobin (Hb) is also known as Hb Bristol, the first unstable Hb described, since in a fraction of the variant the methionine is modified into an aspartic acid by a posttranslational modification. This replacement disrupts the apolar bonds between the valine and the heme group, producing an unstable Hb and severe hemolysis. We have identified this rare hemoglobinopathy in an Argentinean girl with severe hemolytic anemia, splenomegaly and frequent requirement for red blood cell transfusions.

Rafael Bielsa y la conformación de un nuevo modelo de formación científica universitaria de Marco, Miguel Angel L. El presente artículo se enmarca en el abordaje biográfico del doctor Rafael Bielsa efectuado en el marco del Proyecto "Juristas, Derecho y Sociedad en la Argentina contemporánea. Ideas y mentalidades de los operadores jurídicos (1901-1970)", del Instituto de Investigaciones en Historia del Derecho. Siguiendo un camino abierto por el doctor Víctor Tao Anzoátegui en la década del 70, se profundiza en la obra de Rafael Bielsa en su prédica por la superación del positivismo, el fomento de los estudios jurídicos y sus iniciativas en reformar el sistema jurídico. Analiza la influencia de lo regional en la visión de Bielsa y sus propuestas superadoras de la Reforma Universitaria, poniendo a la luz el valioso contenido de las actas del Consejo Directivo de la Facultad de Ciencias Económicas, Comerciales y Políticas y del Colegio de Abogados de Rosario. La primera parte se refiere a la incidencia de la Facultad de Ciencias Económicas, Comerciales y Política en la formación de recursos para la región; la segunda, al decanato de Rafael Bielsa y la proyección internacional de la Facultad; la tercera, a la situación en tiempos de intervenciones nacionales y el Golpe de Estado de 1930; la cuarta parte: al breve rectorado de Bielsa al frente de la Universidad Nacional del Litoral y su tercer decanato; la quinta parte: a la consolidación de los flamantes institutos de investigación; y la sexta parte, al cuarto decanato de Bielsa, coincidente con el inicio de la década del 40. El relevamiento de actas concluye en 1943, cuando un nuevo golpe de Estado implicó un cambio de rumbo en la política universitaria argentina.

Infection by Rickettsia bellii and Candidatus "Rickettsia amblyommii" in Amblyomma neumanni ticks from Argentina Labruna, Marcelo B.; Pacheco, Richard C.; Nava, Santiago; Brandão, Paulo E.; Richtzenhain, Leonardo J.; Guglielmone, Alberto Alejandro The tick species, Amblyomma neumanni (Acari: Ixodidae) is the most frequent tick parasitizing humans in northwestern Argentina. The present study evaluated the rickettsial infection among 55 A. neumanni adult free-living ticks collected in Dean Funes, Córdoba Province. Ticks were individually processed by the hemolymph test with Gimenez staining, isolation of rickettsia in Vero cell culture by the shell vial technique, and polymerase chain reaction (PCR) targeting the citrate synthase rickettsial gene. Through the shell vial technique, rickettsiae were successfully isolated and established in Vero cell culture from two ticks (ticks 4 and 13), which previously showed to contain Rickettsia-like organisms by the hemolymph test. These two Rickettsia isolates were designated as An4 and An13. Molecular characterization (partial DNA sequences of two to three rickettsial genes were determined) of these two isolates and phylogenetic analyses identified them as Rickettsia bellii (isolate An4) and Candidatus "Rickettsia amblyommii" (isolate An13). After testing all A. neumanni ticks by PCR, the prevalence of Candidatus R. amblyommii and R. bellii was 23.6% (13/55) and 3.6% (2/55), respectively. These two rickettsiae have been considered of unknown pathogenicity and appropriate studies to test their pathogenicity to humans or animals need to be conducted. This is the first report of Rickettsia in ticks from Argentina, and also in the species A. neumanni. The results reinforce previous findings that R. bellii (and probably Candidatus R. amblyommii) are widespread among some Neotropical Amblyomma species, suggesting that these ticks gained these bacterial agents from a common ancestor and/or by recent horizontal transmission of rickettsiae between ticks.

Phosphorous amount in floating and rooted macrophytes growing in wetlands from the Middle Paraná River floodplain (Argentina) Hadad, Hernán Ricardo; Maine, Maria Alejandra Biomass, P concentration, P amount and chlorophyll in three floating and three rooted macrophytes growing in wetlands of the Middle Paraná River floodplain measured in winter and summer were compared. Macrophytes were sampled three times in summer and twice in winter, in the period 2002/2004. Although Pistia stratiotes was the species with the highest P concentration in leaves and roots, Typha domingensis, Eichhornia crassipes and Pontederia cordata were the most efficient species in P retention in natural wetlands because of their higher biomass. Total P amount in rooted species did not show seasonal variations. However, T. domingensis accumulated a greater P amount in its aerial part in summer, whereas in winter it did so in its below-ground parts, indicating an important P dynamic regarding translocation within the plant. In summer, floating species were able to accumulate great quantities of P in a short period due to their high growth rate. In order to optimize and maintain the efficiency of constructed wetlands for P removal throughout the year, a selection of floating and rooted species should be used.

Effects of enzymatic treatment on cellulosic fibres from recycled paper. Analysis of the experimental design Taleb, María Claudia; Maximino, Mirta Graciela An enzymatic preparation consisting of cellulases and hemicellulases significantly affected the drainability and strength properties of an unbleached softwood Kraft pulp repulped in laboratory. The independent variables, treatment time and enzyme dose, were analysed using a central composite design for both the whole pulp and its fibrous fractions. Statistical analysis showed significant improvements in drainability. The effects of enzymatic treatments on strength properties were: increase in tensile index and apparent density and decrease in tear index and light scattering coefficients. Changes in fibre surfaces (initial and with enzyme treatment) could be observed by Simons´ differential stain.

Influence of residual milk-clotting enzyme and proteolysis on melting properties of soft cheese Candioti, Mario César; Alonso, María Jimena; Hynes, Erica Rut In this work, we assessed the influence of coagulant residual activity and primary proteolysis on Cremoso Argentino cheese melting properties. For that purpose, we made Cremoso soft cheeses using different amounts of coagulant, and also obtained samples in which milk clotting enzyme was inactivated. The residual activity of coagulant correlated with primary proteolysis, especially in early stages of ripening. Caseins’ hydrolysis did not significantly impact on the melting ability of the cheeses, expressed as the area increase after heating samples under standardised conditions. Samples with similar proximate composition showed some changes in meltability; those seemed related to pH evolution during ripening.

Protective action of Lactobacillus kefir carrying S-layer protein against Salmonella enterica serovar Enteritidis Golowczyc, Marina Alejandra; Mobili, Pablo; Garrote, Graciela Liliana; Abraham, Analia Graciela; de Antoni, Graciela Liliana Eight Lactobacillus kefir strains isolated from different kefir grains were tested for their ability to antagonize Salmonella enterica serovar Enteritidis (Salmonella enteritidis) interaction with epithelial cells. L. kefir surface properties such as autoaggregation and coaggregation with Salmonella and adhesion to Caco-2/TC-7 cells were evaluated. L. kefir strains showed significantly different adhesion capacities, six strains were able to autoaggregate and four strains coaggregated with Salmonella. Coincubation of Salmonella with coaggregating L. kefir strains significantly decreased its capacity to adhere to and to invade Caco-2/TC-7 cells. This was not observed with non coaggregating L. kefir strains. Spent culture supernatants of L. kefir contain significant amounts of S-layer proteins. Salmonella pretreated with spent culture supernatants (pH 4.5–4.7) from all tested L. kefir strains showed a significant decrease in association and invasion to Caco-2/TC-7 cells. Artificially acidified MRS containing lactic acid to a final concentration and pH equivalent to lactobacilli spent culture supernatants did not show any protective action. Pretreatment of this pathogen with spent culture supernatants reduced microvilli disorganization produced by Salmonella. In addition, Salmonella pretreated with S-layer proteins extracted from coaggregating and non coaggregating L. kefir strains were unable to invade Caco-2/TC-7 cells. After treatment, L. kefir S-layer protein was detected associated with Salmonella, suggesting a protective role of this protein on association and invasion.

Implementing a post-graduate degree course for diabetes educators in Argentina. Gagliardino, Juan Jose; Malbran, Maria del Carmen; Clark, Charles One reason for poor diabetes outcomes – the development of disabling, potentially life-threatening complications – is the lack of effective participation by people with diabetes in the management of their own condition. This participation is the key to successfully achieving therapeutic goals. To be able to follow a difficult and complex life-long regimen requires high levels of motivation and knowledge. Yet although extensive evidence supports this concept, only a minority of people receive appropriate diabetes education. Thus, many people with diabetes are handicapped in their self-care by limited knowledge and skills. The authors describe an initiative in La Plata, Argentina, which aims to promote and diffuse high-quality diabetes education by training healthcare providers to become expert educators.

The diabetes-related attitudes of health care professionals and persons with diabetes in Argentina; Actitudes relacionadas con la diabetes en los profesionales sanitarios y las personas con diabetes en Argentina Gagliardino, Juan Jose; González, Claudio; Caporale, Joaquín E. To test diabetes-related attitudes of health care team members (HCTMs) and people with diabetes in a developing country, in this case, Argentina. The third version of the Diabetes Attitudes Scale (DAS-3) was randomly administered, in person, to 252 HCTMs (nurses, nutritionists, physicians, podiatrists, and social workers) and 279 people with type 1 or type 2 diabetes mellitus in several provinces of Argentina in 2004. Data from 531 completed questionnaires were included in the study. The data were statistically analyzed using analysis of variance, covariance, chi-square, and t-tests.; Analizar las actitudes relacionadas con la diabetes en los miembros del equipo de salud (MES) y las personas con diabetes en un país en desarrollo, Argentina. Se administró de forma aleatoria la tercera versión de la Escala de Actitudes en la Diabetes (DAS-3) a 252 MES (enfermeros, nutriólogos, médicos, podólogos y trabajadores sociales) y a 279 personas con diabetes mellitus tipos 1 ó 2 en varias provincias de Argentina en 2004. Los datos de 531 cuestionarios respondidos se evaluaron mediante análisis de varianza y covarianza, y las pruebas de la t y de la ji al cuadrado.

Caracterización de la proteína microtubular de diferentes helmintos parásitos: Sus implicancias en el modo de acción de los benzimidazoles antihelmínticos Scarcella, Silvana Andrea; Ceriani, Maria Carolina; Rodriguez, Julio Armando; Solana, Hugo Daniel Los antihelmínticos benzimidazoles (BZD) desestabilizan el equilibrio tubulina-microtúbulo originando en el parásito una pérdida de la homeostasis celular, desprendimiento y muerte. Su baja toxicidad  se explica por una mayor afinidad por la tubulina del parásito, especialmente en cestodes y nematodes, comparada con la observada para tubulina de mamífero. Al ser tubulina  una proteína altamente conservada en la escala zoológica se hace necesario investigar las probables causas de esa diferente afinidad. El objetivo del presente trabajo fue comparar ciertas características moleculares de tubulina de trematodes (Fasciola hepatica), cestodes (Moniezia expansa), nematodes (Ascaris suum) y tubulina purificada de cerebro de rata. Se utilizaron técnicas electroforéticas (PAGE) e inmunoquímicas con anticuerpos monoclonales específicos dirigidos contra a y b tubulina. Los resultados demostraron que aunque en diferente cuantía mientras que fue factible la detección de las diferentes tubulinas en  mamíferos, cestodes y nematodes, en ninguno de los casos se detectó la tubulina de F. hepatica. Esto tiene implicancias directas en el entendimiento de las diferentes susceptibilidades de cada especie a estos fármacos, lo cual puede ser un primer paso hacia la comprensión de la actividad farmacológica de estas drogas.; The anthelmintic benzimidazoles cause a destabilization of tubulin-microtubule equilibrium which induces to a lost of the cellular homeostasis, detaching and death of the parasite. They have a low toxicity on the infested animal, explained as a higher affinity for the parasite tubulin, mainly that of cestodes and nematodes. From an evolutionary point of view, tubulin is a highly conserved protein, thus in order to understand the probable causes for that difference in affinity, it is necessary to further investigate the microtubular protein at a molecular level. The aim of this project was to compare certain molecular characteristics of tubulin from trematodes (Fasciola hepatica), cestodes (Moniezia expansa), nematodes (Ascaris suum) and purified rat brain tubulin. For this purpose electrophoretic techniques (PAGE) followed by immunochemistry using specific monoclonal antibodies against α and β tubulin were used. Results showed that it was possible to detect tubulin spots, but not in the same amount, in mammals, cestodes and nematodes. Under our experimental conditions it was not possible to detect F. hepatica tubulin. This could help to understand the differences in the answer to the anthelmintic drugs and also to learn something about to the farmacological activity of these.

Dive depth and plumage air in wettable birds: the extraordinary case of the imperial cormorant Quintana, Flavio Roberto; Wilson, Rory P.; Yorio, Pablo Martin Cormorants are considered to be remarkably efficient divers and hunters. In part, this is due to their wettable plumage with little associated air, which allows them to dive with fewer energetic costs associated with buoyancy from air in the feathers. The literature attributes particularly exceptional diving capabilities to cormorants of the ‘blue-eyed’ taxon. We studied the diving behaviour of 14 male imperial cormorants Phalacrocorax atriceps (included in the blue-eyed taxon) in Patagonia, Argentina, and found that this species did indeed dive deeper, and for longer, than most other non-blue-eyed cormorant species. This species also exhibited longer dive durations for any depth as well as longer recovery periods at the surface for particular dive durations. We propose that this, coupled with atypically long foraging durations at sea in cold water, suggests that cormorants of the blue-eyed complex have a plumage with a substantial layer of insulating air. This is given credence by a simple model. High volumes of plumage air lead to unusually high power requirements during foraging in shallow, warmer waters, which are conditions that tend to favour wettable plumage. However, deep dives and/or cold water should favour the blue-eyed phenotype, which explains their essentially high latitude distribution.

Variability of UVR effects on photosynthesis of summer phytoplankton assemblages from a tropical coastal area of the South China Sea. Kunshan, Gao; Gang Li; Helbling, Eduardo Walter; Villafañe, Virginia Estela From June to September 2005, we carried out experiments todetermine the ultraviolet radiation (UVR) -induced photoinhibitionof summer phytoplankton assemblages from a coastal site ofthe South China Sea. Variability in taxonomic composition wasdetermined throughout the summer, with a peak chlorophyll a(chl a20 lg chl a L)1) dominated by the diatom Skeletonemacostatum that was detected early in the study period; the rest ofthe time samples were characterized by monads and flagellates,with low chl a values (1–5 chl a lg L)1). Surface water sampleswere placed in quartz tubes, inoculated with radiocarbon andexposed to solar radiation for 2–3 h to determine photosyntheticrates under three quality radiation treatments (i.e. PAB, 280–700 nm; PA, 320–700 nm and P, 400–700 nm) using differentfilters and under seven levels of ambient irradiance using neutraldensity screens (P vs E curves). UVR inhibition of samplesexposed to maximum irradiance (i.e. at the surface) varied from)12.2% to 50%, while the daytime-integrated UVR-relatedphotoinhibition in surface seawater varied from )62% to 7%.The effects of UVR on the photosynthetic parameters PBmax andEk were also variable, but UV-B accounted for most of theobserved variability. During sunny days, photosynthesis ofmicroplankton (>20 lm) and piconanoplankton (<20 lm) weresignificantly inhibited by UVR (mostly by UV-B). However,during cloudy days, while piconanoplankton cells were stillinhibited by UVR, microplankton cells used UVR (mostlyUV-A) as the source of energy for photosynthesis, resulting inhigher carbon fixation in samples exposed to UVR than the onesexposed only to photosynthetically active radiation (PAR). Ourresults indicate that size structure and cloudiness clearlycondition the overall impact of UVR on phytoplankton photosynthesisin this tropical site of South China. In addition, modelpredictions for this area considering only PAR for primaryproduction might have underestimated carbon fixation due toUVR contribution.

Deep divers in shallow seas: Southern elephant seals on the Patagonian shelf Campagna, Claudio; Piola, Alberto Ricardo; Marin, Maria Rosa; Lewis, Mirtha Noemi; Zajaczkovski, Uriel; Fernandez, Teresita Josefa Elephant seals are wide-ranging, pelagic, deep-diving (average of 400–600 m) predators that typically travel to open waters and continental shelf edges thousands of kilometers from their land breeding colonies. We report a less common pattern of foraging in the shallow waters of a continental shelf. Southern elephant seals, Mirounga leonina, that breed at Penı´nsula Valde´s (Argentina), face an extended (1,000,000km2; 400–700 km-wide, depending on track), shallow (o150 m) and seasonally productive plateau, the Patagonian shelf. Adults of both sexes usually cross it in rapid transit to other potential foraging grounds on the shelf edge or in the Argentine Basin, but 2–4 year-old juveniles spread over the plateau and spent months in shallow waters. This behavior was recorded for 9 seals (5 males and 4 females) of 23 satellitetrackedjuveniles (springs of 2004 and 2005) and for 2 subadult males studied in previous seasons. Trips included travel trajectories and time spent in areas where swim speed decreased, suggesting foraging. Preferred locations of juvenile females were in the proximity of the shelf break, where stratified waters had relatively high phytoplankton concentrations, but young and subadult males used the relatively cold (7–8 1C), low-salinity (33.3) mid-shelf waters, with depths of 105–120m and a poorly stratified water column. Three of the latter seals, instrumented with  ime–depth recorders, showed dives compatible with benthic feeding and no diel pattern of depths distribution. Regions of the mid-shelf were used in different seasons and were associated with low chlorophyll-a concentration at the time of the visit, suggesting that surface productivity does not overlap with putative quality habitat for benthic foragers. Benthic diving on the shallow mid-shelf would be a resource partitioning strategy advantageous for young males prior to greater energetic demands of a high growth rate and a large body size. Later in life, the more predictable, bathymetry-forced, shelf-break front may offer the food resources that explain the uninterrupted increase of this population over several decades.

Comparisons of IRI TEC predictions with GPS and digisonde measurements at Ebro Mosert, Marta Estela; Gende, Mauricio Alfredo; Brunini, Claudio Antonio; Ezquer, Rodolfo Gerardo; Altadill, D. Vertical TEC measurements obtained with GPS satellite signals (GPSTEC) and total electron content derived from ionograms (ITEC) are compared with the latest version of the International Reference Ionosphere, IRI-2000 (IRITEC). Digisonde data from the Ebro station (40.8°N, 0.5°E) recorded during two years of high solar activity 2000 (Rz 12 = 117) and 2001 (Rz 12 = 111) are used in the study. The results obtained with the three techniques are similar, and as expected, the GPS TEC values are greater than those obtained with the digisonde measurements. The IRI predictions generally overestimate the ITEC values. The diurnal and seasonal variations of the plasmaspheric electron content are also analyzed.

Ionospheric variability studies in Argentina Ezquer, Rodolfo Gerardo; Mosert, Marta Estela This paper reviews and extends studies on ionospheric variability performed by the Argentine scientific community. Ground based ionosonde measurements for different seasonal and solar conditions and vertical total electron content (VTEC) obtained with GPS satellite signals during a high solar activity year are used. Median, quartiles and deciles are used to specify the variability. In general, the results show that: (a) the variability is higher in low solar activity than in high solar activity, and (b) it is larger by night than by day. Moreover, is shown that could be possible specify the variability of foF2 for high solar activity and hours around noon.