Biotic interaction between spionid polychaetes and bouchardiid brachiopods: Paleoecological, taphonomic and evolutionary implications

Shells of Bouchardia rosea (Brachiopoda, Rhynchonelliformea) are abundant in Late Holocene death assemblages of the Ubatuba Bight, Brazil, SW Atlantic. This genus is also known from multiple localities in the Cenozoic fossil record of South America. A total of 1211 valves of B. rosea, 2086 shells of sympatric bivalve mollusks (14 nearshore localities ranging in depth from 0 to 30 m), 80 shells of Bouchardia zitteli, San Julián Formation, Paleogene, Argentina, and 135 shells of Bouchardia transplatina, Camacho Formation, Neogene, Uruguay were examined for bioerosion traces. All examined bouchardiid shells represent shallow-water, subtropical marine settings. Out of 1211 brachiopod shells of B. rosea, 1201 represent dead individuals. A total of 149 dead specimens displayed polychaete traces (Caulostrepsis). Live polychaetes were found inside Caulostrepsis borings in 10 life-collected brachiopods, indicating a syn-vivo interaction (Caulostrepsis traces in dead shells of B. rosea were always empty). The long and coiled peristomial palps, large chaetae on both sides of the 5th segment, and flanged pygidium found in the polychaetes are characteristic of the polychaete genus Polydora (Spionidae). The fact that 100% of the Caulostrepsis found in living brachiopods were still inhabited by the trace-making spionids, whereas none was found in dead hosts, implies active biotic interaction between the two living organisms rather than colonization of dead brachiopod shells. The absence of blisters, the lack of valve/site stereotypy, and the fact that tubes open only externally are all suggestive of a commensal relationship. These data document a new host group (bouchardiid rhynchonelliform brachiopods) with which spionids can interact (interestingly, spionid-infested sympatric bivalves have not been found in the study area despite extensive sampling). The syn-vivo interaction indicates that substantial bioerosion may occur when the host is alive. Thus, the presence of such bioerosion traces on fossil shells need not imply a prolonged post-mortem exposure of shells on the sea floor. Also, none of the Paleogene and Neogene Bouchardia species included any ichnological evidence for spionid infestation. This indicates that the Spionidae/ Bouchardia association may be geologically young, although the lack of older records may also reflect limited sampling and/or taphonomic biases.

Las pequeñas y medianas empresas en Perú

Incluye Bibliografía

Regional integration and the issue of choosing an appropriate exchange-rate regime in Latin America

Includes bibliography

Do men and women use similar adaptive locomotion to clear static and dynamic obstacles?

Purpose. The purpose of this study was to analyze the influence of gender on the adaptive locomotion in the clearance of obstacles. Specifically, it was evaluated if there are differences in the space-temporal parameters between male and female in the clearance of and dynamic obstacles moving at both slow and fast speeds. Basic procedures. Five young male adults and five young female adults took part in this study. The task was performed in three conditions: static obstacle and dynamic obstacle - clearance perpendicular to the participant's trajectory at slow speed (1.07 m/s) and at fast speed (1.71 m/s). The trials were recorded by two digital cameras and spatial-temporal information was obtained. Main findings. The dynamic obstacle conditions required more visual inspection. The results showed different adaptive locomotion between the sexes. The distinct gait patterns were evidenced for the spatial and temporal variables and cadence in the three conditions. Conclusions. The women presented a more conservative behavior, which was evidenced by the increase of the length in the penultimate step and in the toe clearance.

Effects of fatigue induced by prolonged gait when walking on the elderly

Purpose. Fatigue has been pointed as a fall risk in the elderly; however, the effects of prolonged gait on neuromuscular recruitment and on its pattern remain unknown. The aim of this study was to evaluate the effects of prolonged gait on neuromuscular recruitment levels and spatial-temporal gait variables. Methods. Eight healthy older women (age: 72.63 ± 6.55 years) walked at their preferred walking speed for twenty minutes on a treadmill. The Root Mean Square (RMS) from the vastus-lateralis, femoral biceps, tibialis anterior and lateral gastrocnemius muscles were determined at the first and last minute of the test during the moments of Heel Strike (HS), Terminal Stance and Terminal Swing (TS). In addition, coactivation in the knee and ankle as well as the stride cadence and length were measured in the test. The two RMS data (taken at the first and last minute) were compared by means of a Student's t-test. Results. Twenty minutes of walking induced fatigue in the subjects, as observed through an increase in RMS, notably during the HS and TS. Coactivation was also influenced by the prolonged gait test. The only gait phase where a risk of falling was enhanced was the HS. Nonetheless, subjects developed strategies to maintain a safe motor pattern, which was evidenced by an increase in stride length and a decrease in stride cadence. Conclusion. Tests lasting just twenty minutes on a treadmill were enough to induce fatigue in older adults. However, the level of fatigue was not enough to present a danger or fall risk to elderly individuals.

Maximal isokinetic peak torque and EMG activity determined by shorter ranges of motion

Purpose. Isokinetic tests are often applied to assess muscular strength and EMG activity, however the specific ranges of motion used in testing (fully flexed or extended positions) might be constrictive and/or be painful for patients with injuries or under-going rehabilitation. The aim of this study was to examine the effects of different ranges of motion (RoM) when determining maximal EMG during isokinetic knee flexion and extension with different types of contractions and velocities. Methods. Eighteen males had EMG activity recorded on the vastus lateralis, vastus medialis, semitendinosus and biceps femoris muscles during five maximal isokinetic concentric and eccentric contractions for the knee flexors and extensors at 60° • s -1 and 180° • s -1. The root mean square of EMG was calculated at three different ranges of motion: (1) a full range of motion (90°-20° [0° = full knee extension]); (2) a range of motion of 20° (between 60°-80° and 40°-60° for knee extension and flexion, respectively) and (3) at a 10° interval around the angle where peak torque is produced. EMG measurements were statistically analyzed (ANOVA) to test for the range of motion, contraction velocity and contraction speed effects. Coefficients of variation and Pearson's correlation coefficients were also calculated among the ranges of motion. Results. Predominantly similar (p > 0.05) and well-correlated EMG results (r > 0.7, p ≤ 0.001) were found among the ranges of motion. However, a lower coefficient of variation was found for the full range of motion, while the 10° interval around peak torque at 180° • s -1 had the highest coefficient, regardless of the type of contraction. Conclusions. Shorter ranges of motion at around the peak torque angle provides a reliable indicator when recording EMG activity during maximal isokinetic parameters. It may provide a safer alternative when testing patients with injuries or undergoing rehabilitation.

Alternative interpretations of some earliest ediacaran fossils from China

In a letter to Nature (February, 2011), Xunlai Yuan and collaborators recorded carbon compression fossils from black shales of the Lantian Formation (Ediacaran), southern Anhui Province, South China. The new fossils, described under five morphological types (Types A to E), exhibit degrees of morphological differentiation suggesting that they were multicellular eukaryotes. Some of the Lantian macrofossils were interpreted as algae, but others are of unknown affinities. For reasons noted in this discussion, Type A fossils attracted our particular attention, and we suggest an alternative interpretation of their affinities. According to our view, some of them (at least those with three faces and no globose holdfast at their base) may represent conulariid cnidarians or close medusozoan relatives. The undistorted organism probably was a three-sided cone in life. We believe that our suggested alternative interpretations of the anatomy and affinities of the fossils in question can be useful in guiding future research on the oldest currently known fossil assemblage of multicellular organisms. Copyright © 2012.

Effects of elbow flexor muscle resistance training on strength, endurance and perceived exertion

Purpose. To verify the effects of resistance training at the electromyographic fatigue threshold (EMGFT) based on one-repetition maximum strength (1RM), heart rate (HR), rate of perceived exertion (PE) and endurance time (EndT). Methods. Nineteen subjects (training group [TG]: n = 10; control group [CG]: n = 9), performed 1-min bicep curl exercises sets at 25%, 30%, 35% and 40% 1RM. Electromyography (biceps brachii and brachiorradialis), HR and PE were registered. Biceps brachii EMGFT was used to create a load index for an eight-week resistance training programme (three sets until exhaustion/session, two sessions/week) for the TG. The CG only attended one session in the first week and another session in the last week of the eight-week training period for EndT measurement. EndT was determined from the number of repetitions of each of the three sets performed in the first and last training sessions. After training, 1RM, EMGFT, EndT, HR and PE at the different bicep curl load intensities were again measured for both groups. Results. Increases in 1RM (5.9%, p < 0.05) and EndT (> 60%, p < 0.001) after training were found. In addition, PE was reduced at all load intensities (p < 0.05), while no changes were found for HR and EMGFT after training. Conclusions. Strength-endurance training based on the EMGFT improved muscular endurance and also, to a lesser extent, muscular strength. Moreover, the reduced levels of physical exertion after training at the same intensity suggest that endurance training exercises may improve comfort while performing strength exercises.

Canales, cadenas, corredores y competitividad: un enfoque sistémico y su aplicación a seis productos latinoamericanos de exportación

Incluye Bibliografía

Estrategia de apertura comercial: planteo teórico y evidencias empíricas

Incluye Bibliografía

A Gazeta de Notícias do Rio de Janeiro (1896-7) e La Guerra del fin del mundo (1981) de Mario Vargas Llosa: uma análise comparativa entre o discurso republicano e a (re)criação literária

Pós-graduação em Letras - FCLAS

Desempenho de reatores anaeróbios horizontais com manta de lodo e de leito fixo, em série, tratando águas residuárias do beneficiamento do café por via úmida

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identidade e história: Belém do Grão-Pará como narrativa da nacionalidade

A motivação inicial desta pesquisa é a fértil discussão acerca da Identidade e das diferenças culturais entabulada especialmente pelos Estudos Culturais e Literários, especificamente a partir da categoria conceitual da nacionalidade. Norteada pelo conceito de Alegoria proposto por Fredric Jameson, para quem tal conceito se aplica principalmente à análise dos textos literários do capitalismo tardio, tentou-se desnudar as estratégias usadas na composição de Belém do Grão-Pará1 para narrar a complexidade da identidade nacional inscrita no Inconsciente Político. Admitindo que a Alegoria, para Jameson, é o próprio objeto cultural e estético cuja constituição e disposição dos elementos estruturais narra, às vezes em foro íntimo ou privado das personagens, a História das sociedades, segundo a experiência político-ideológica de suas classes. Tomados estes pressupostos, fez-se a análise do romance dalcidiano considerando-se a migração do protagonista como alegoria do cruzamento entre diferentes culturas, fato social gerador de uma hipotética diluição da identidade. Contudo, apoiado num paralelo traçado entre o contato do ribeirinho com o modus vivendi da cidade e a reação antropofágica do modernismo brasileiro frente ao modus vivendi civilizado da Europa, este trabalho nega a idéia de que o cruzamento de fronteiras culturais implique no fim da nacionalidade. Em linhas gerais tratamos de um conceito de Identidade fundado na experiência coletiva de indivíduos que, apesar de grandes diferenças de classe social, gênero ou etnia, construíram-se sob ideologias comuns. Nesta análise de Belém do Grão-Pará, cenas urbanas como ir ao cinema ou ver passar o trem são resignificadas pelo protagonista com base nas referências que trouxe de Cachoeira do Arari, seu lugar de origem, enquanto este também passa por uma revisão segundo o novo paradigma urbano que o protagonista vive em Belém.