Showing papers by "University of Costa Rica published in 1989"
TL;DR: The phase-space approach to spin is developed from two basic principles, SU(2)-covariance and traciality, as a theory of Wigner functions on the sphere.
288 citations
TL;DR: A new muscle damaging toxin, myotoxin II, was purified from the venom of Bothrops asper by ion-exchange chromatography on CM-Sephadex C-25, and immunochemical tests indicate a high degree of homology between this toxin and a previously characterizedMyotoxin I.
213 citations
TL;DR: The results demonstrate the high degree of immunological cross reactivity between components affecting coagulation in Costa Rican crotaline snake venoms, since only three venoms are used in the immunization of horses.
192 citations
TL;DR: In this paper, a model for many active stratovolcanoes involves a magma column with a frozen cap, cooled by a meteoric-water hydrothermal system.
Abstract: AWORKING model for many active stratovolcanoes involves a magma column with a frozen cap, cooled by a meteoric-water hydrothermal system. Systems with such high latent and specific heat capacities may easily buffer internal temperatures and apparent surface activity during short-term changes in power output. The surface manifestation of volcanic hydrothermal systems takes the form of boiling mud pools, hot springs, fumaroles, and in about 20–30 cases worldwide, hot crater lakes1–7. The latter are rare because they require special conditions to exist: high water supply, confined fumarole discharge, low permeability substratum and effective sub-surface heat transport. Crater lakes at active volcanoes are in a state of dynamic equilibrium whereby annual water losses through evaporation and infiltration are balanced by additions due to, for example, rainfall and runoff. Any change in volcano power output will directly affect the internal energy and surface heat loss of the lake. Vaporization of water within the hydrothermal system, leading to enhanced steam discharge from fumaroles, can also absorb increased power output. For long-term (months to years) power changes, we propose that crater-lake and fumarole discharge variations may well occur before significant signals on seismic and tilt networks are detected. As an illustration of these ideas, we consider here the recent activity at Poas volcano, Costa Rica.
103 citations
TL;DR: The lack of phospholipase A2 activity in this toxin, together with the observation that it behaved as an amphiphilic protein in charge-shift electrophoresis, suggests that it might penetrate and disorganize muscle plasma membrane by means of a hydrophobic interaction.
85 citations
TL;DR: Although there is no evidence of any predator on Porites lobata at Cano Island, the triggerfish Pseudobalistes naufragium breaks off fragments of the coral while searching for food, and together, this dispersal mechanism, rapid injury recovery, and high resistance to environmental stress seem to enhance the distribution and dominance of the massive coral Porites Lobata at cano Island.
Abstract: . Around the Biological Reserve of Cano Island, Pacific Costa Rica, there are five large coral reef flats (with size ranges of 0.8–4.2 ha) built mainly of dead Pocillopora spp. At present, they are covered mainly by crustose coralline algae and microatolls of Porites lobata. From the upper reef slope to the reef base several corals grow in small patches (e. g., Pavona clavus, Pavona varians, Pavona gigantea, Gardineroseris planulata, Psammocora superficialis, Pocillopora elegans, Pocillopora damicornis); the massive coral Porites Iobata is predominant. Pocilloporid species are predominant on most other eastern Pacific reefs.
The Cano Island reef is typical of a community whose structure has been controlled by both physical (in shallow water) and biological (in deeper water) factors. Shallow reef areas are influenced by strong wave action and extreme low tides. The distribution, abundance, and feeding preferences of corallivorous organisms (e. g., Acanthaster planci, Arothron meleagris, Pseudobalistes naufragium, Quoyula monodonta) on the deeper reef suggest that most pocilloporids are affected and limited by them. Although there is no evidence of any predator on Porites lobata at Cano Island, the triggerfish Pseudobalistes naufragium breaks off fragments of the coral while searching for food. These fragments often survive to form new colonies. Together, this dispersal mechanism, rapid injury recovery, and high resistance to environmental stress seem to enhance the distribution and dominance of the massive coral Porites lobata at Cano Island.
72 citations
TL;DR: In this article, a technique du doubly-labeled water (DLW) and le metabolisme d'activite et le flux de l'eau chez Thalurania Colombica et Chalybura Urochrysia sont etudies.
Abstract: Grâce a la technique du «doubly-Labeled water» (DLW), le metabolisme d'activite et le flux de l'eau chez Thalurania Colombica et Chalybura Urochrysia sont etudies
57 citations
52 citations
TL;DR: In this paper, the authors discuss and correlate various types of regularizations available in the literature for the singular function H(x) x k, where k is an integer and h is the Heaviside function, and present the corresponding regularization for the function r−k, where r is the radial distance in R n.
49 citations
TL;DR: Antivenom neutralized venom-induced increases in serum enzyme levels following preincubation with venom, indicating that antivenom contains antibodies against tissue-damaging toxins.
35 citations
TL;DR: In a study of 319 fruit samples infested with larvae of fruit flies, collected from 135 localities, 8 parasitoid species were recovered from 11.0% of the fruit samples, suggesting the need for systematic monitoring of populations of released parasitoids.
Abstract: The geographical distribution of the parasitoid species associated with fruit flies in Costa Rica is presented. In a study of 319 fruit samples infested with larvae of fruit flies, collected from 135 localities, 8 parasitoid species were recovered from 11.0% of the fruit samples. Two species are considered to be indigenous, two were introduced for the biological control ofCeratitis capitata (Wiedemann) in this country, at least 3 unidentified species of eucoiline cynipoids and one species of uncertain origin was found for the first time.
TL;DR: It is speculated that patients born through thick, meconium-stained amniotic fluid may be at greater risk of sequelae such as otitis media from this foreign body inflammatory reaction in the middle ear and mastoid cavity.
TL;DR: Singular integral equations with logarithmic kernels arise in analysis and in many two-dimensional problems in mathematical physics, mechanics and engineering such as potential and scattering theories as mentioned in this paper.
Abstract: Singular integral equations with logarithmic kernels arise in analysis and in many two-dimensional problems in mathematical physics, mechanics and engineering such as potential and scattering theories.
TL;DR: The authors found that the unstructured task elicited significantly more transfer strategies from both groups of students, and that there was a significant interaction between time and proficiency level with respect to the use of task-influenced strategies.
Abstract: The study of communication strategies can provide insights into the ways in which interlanguage changes and develops as language learners become increasingly proficient in the target language. This article describes an investigation centered on the communication strategies used by two groups (intermediate and advanced) of Spanish-speaking students of English to express lexical meaning. Two different tasks, one conskting of answering structured questions and the other a simulated communication situation, were used to elicit data from the students. Data were collected at two different times, once at the beginning of the term and again five weeks later. Proficiency level, task, and time were the independent variables and three types of communication stmtegies (transfer, overgeneralization, and task-influenced) were the dependent variables. It was found that the unstructured task elicited significantly more transfer strategies from both groups of students, and that there was a significant interaction between time and proficiency level with respect to the use of task-influenced strategies—the advanced group used a greater mean proportion of task-influenced strategies than the intermediate group at Time1, while the intermediate group used a greater mean proportion of this type of strategy at Time2. A post hoc analysis of these data suggests that students of a language may go through a period of maximum exploitation of task-influenced strategies which peaks and then drops off as they become more proficient in the language.
TL;DR: Investigation of three Mexican species belonging to the subtribe Melampodinae (Compositae, tribe Heliantheae) gave in addition to known compounds, six melampolides and three kaurane derivatives, one being a β- d -glucopyranoside.
01 Jul 1989
TL;DR: Two new species of false spider mite are described and illustrated and a key to species of Brevipalpus found in Costa Rica is presented.
Abstract: New species of false spider mite are described and illustrated: Brevipalpus ortizi sp. n. and Brevipalpus pseudostriatus sp. n. A key to species of Brevipalpus found in Costa Rica is presented.
Journal Article•
TL;DR: A lectin-like protein was isolated from L. muta venom by gel filtration on BIO Gel P-100 followed by column Chromatography on DEAE-sephades A-50 and exhibited agglutinin activity toward 0+ human erythrocytes and double dose of protein caused the death of the animal.
Abstract: A lectin-like protein was isolated from L. muta venom by gel filtration on BIO Gel P-100 followed by column Chromatography on DEAE-Sephadex A-50. The protein eluted at 0.4 M NaO in 0.01 Tris pH 7.3 and exhibited agglutinin activity toward 0 + human erythrocytes. The protein is a dimer with Mr 28 kDa. Amino acid analysis revealed high content of tryptophan and acid residues and low content of cysteine and methionine residues. No neutral carbohydrates and sialic acid were detected. Circular dichroic spectrum shows 78% of B structure and 1% of α structure. In vitro experiments with ery throcytes from rat, rabbit and dog revealed strong agglutination while red blood cells from mice, sheep and goat were not agglutinated. In vivo experiments using non-anesthetized rats, a sharp and prolonged fall in the blood pressure was observed at protein dose of 1.5 mg/kg. Double dose of protein caused the death of the animal.
TL;DR: Plethodontid salamanders in the genus Oedipina are characterized by a strongly heteromorphic sex-determining pair of X/Y chromosomes, and cytological evidence of dosage compensation, such as differential staining of the X chromosomes or Barr bodies, in mitotic or interphase cells from female animals is found.
Abstract: Plethodontid salamanders in the genus Oedipina are characterized by a strongly heteromorphic sex-determining pair of X/Y chromosomes. The telocentric X chromosome and the subtelocentric Y chromosome are clearly distinguished from the autosomes and their behavior during meiosis can be sequentially followed in squash preparations of spermatocytes. In Oedipina the sex chromosomes are not obscured by an opaque “sex vesicle” during early meiotic stages, making it possible to observe details of sex bivalent structure and behavior not directly visible in other vertebrate groups. The sex chromosomes can first be distinguished from autosomal bivalents at the conclusion of zygotene, with X and Y synapsed only along a short segment at their non-centromeric ends, forming a bivalent that contrasts sharply with the completely synapsed autosomes. During pachytene, the XY bivalent becomes progressively shortened and more compact, disappearing as a visible structure when pachytene progresses into the diffuse stage of male meiosis. Diplotene bivalents gradually emerge from the diffuse nuclei, presumably by the return of the loops of chromatin into their respective chromomeres. During early diplotene, the X/Y bivalent is clearly visible with a single chiasma within the synapsed segment. This chiasma is terminalized by first meiotic metaphase with the X and Y appearing either in end-to-end synaptic contact or as univalents separated at opposite poles relative to the equatorially distributed autosomal bivalents. In C-banded preparations, the Y is entirely heterochromatic while the X contains a large centromeric C-band and another block of heterochromatin located at the telomeric end, in the region of synapsis with the Y. We find no cytological evidence of dosage compensation, such as differential staining of the X chromosomes or Barr bodies, in mitotic or interphase cells from female animals.
TL;DR: The deficient hygienic conditions and overcrowding in the Pueblo Nuevo refugee camp are responsible for the high rates of infections and the continued presence of infections many of which probably were acquired in Nicaragua.
Abstract: Articulo cientifico -- Universidad de Costa Rica. Instituto de Investigaciones en Salud, 1989
TL;DR: Two further species, which are also placed in the subgenus Ageratina, gave p -hydroxyacetophenone derivatives which seem to be characteristic for this group, and the structure were elucidated by high field 1 H NMR techniques.
TL;DR: Observations on the population dynamics of Anastrepha obliqua associated with a mango plantation in Orotina, Costa Rica were carried out, finding most emerge just after the first rains; this coincides with the fruiting season, and emergence continues many weeks after the crop is over.
Abstract: A number of observations on the population dynamics of Anastrepha obliqua associated with a mango plantation in Orotina, Costa Rica were carried out (a) After eleven months sampling with McPhail traps, 5463% of adults captured were A serpentina 4173% A obliqua 356% A striata and 008% A balloui The period of maximum abundance of these species coincides with the fruiting season of the respective host plants, A serpentina coincided with the fruiting of several Sapotaceae, A obliqua with some Anacardiaceae and A striata with some Myrtaceae However all adults from infested mangoes were A obliqua (b) The phenology of adult emergence of A obliqua from the ground was observed in 1986 Most emerge just after the first rains; this coincides with the fruiting season, and emergence continues many weeks after the crop is over (c) To determine the dispersal of A obliqua 633 young adults were marked and released in the mango plot Only one marked adult was recaptured five weeks later Adults
TL;DR: O presente estudo sugere que o Cryptosporidium e um agente causal de diarreia auto-limitada em criancas imunocompetentes em Belem, Para.
Abstract: Num periodo de 12 meses, 201 especimes fecais de 61 criancas foram examiandos com vista a deteccao de Cryptosporidium. Cento e quinze especimes foram obtidos durante os episodios diarreicos e 86 de criancas sem diarreia (grupo controle). Todos os especimes fecais foram examinados pelo metodo de coloracao de Ziehl-Neelsen modificado. Cryptosporidum foi identificado em seis (5,2%) das 115 amostras das criancas com diarreia. Em nenhum dos controles foi obtida a presenca desse parasito. O presente estudo sugere que o Cryptosporidium e um agente causal de diarreia auto-limitada em criancas imunocompetentes em Belem, Para.
TL;DR: In this article, a novel alkaloid, maxonine, with an indole-pyrido-naphthyridine skeleton was isolated from Simira maxonii.
TL;DR: An earthquake catalogue of Costa Rica covering the period 1638-1919, using compilations based on diverse bibliographical sources and direct consultations of the National Archives, is presented in this article.
Abstract: An historical earthquake catalogue of Costa Rica covering the period 1638-1919, was donde using compilations based on diverse bibliographical sources and direct consultations of the National Archives. The earthquake historical documentation is incomplete going back to the colonial time. During the first century of the Spanish colonization (XVI century) there is no reference to earthquake in Costa Rica. In the historical seismicity there are examples of earthquake activity from two principal seismic sources; subduction earthquakes and shallow intraplate earthquakes originating in the mountainous terrains of the country. During the period 1638-1910, the earthquake of May 7, 1822 (M = 7.5) was the most destructive event related to the former seismic source. The earthquake of September 2, 1841 (6.0 ≤ M ≤ 6.9) was the most damaging event related to the letter seismic source. Intermediate depth earthquakes associated with the Benioff zone (between 70-200 km depth) and from the Panama fracture zone, the two other important seismic source that affect the century, could not be identified in the searse macroseismic recopilations summarized in the historical catalogue.
TL;DR: Articulo cientifico ( reporte corto) -- Universidad de Costa Rica.
Abstract: Articulo cientifico (reporte corto) -- Universidad de Costa Rica. Instituto de Investigaciones en Salud, 1989
TL;DR: A case of dermatitis in a 31-year-old Costa Rican woman and a pentastomid nymph belonging to the genus Sebekia was obtained from the lesion.
Abstract: A case of dermatitis in a 31-year-old Costa Rican woman is described. From the lesion, a pentastomid nymph belonging to the genus Sebekia was obtained.
TL;DR: The present study suggests that Cryptosporidium is an agent of self-limited diarrhoea among immunocompetent children from Belém, Pará.
Abstract: Two hundred and one samples obtained from 61 children were examined for Cryptosporidium infection during a period of 12 months. One hundred fifteen specimens were collected during diarrhoea episodes and the remaining 86 obtained out of diarrhoea period, as controls. All samples were examined by a modified Ziehl-Neelsen staining method. Cryptosporidium was detected in 6 (5.2%) of 115 samples from diarrhoeic children. All non-diarrhoeic control patients were negative for Cryptosporidum. The present study suggests that Cryptosporidium is an agent of self-limited diarrhoea among immunocompetent children from Belem, Para.
TL;DR: The investigation of the aerial parts of Mikania holwayana afforded in addition to known compounds six new germacranolides while a reinvestigation of M. cordifolia gave several known melampolides and two new ones as mentioned in this paper.