Local Web Buckling in Tapered Composite Beams: A Parametric Study

Composite flooring systems supported by tapered (varying web depth) beams are very attractive from an economic point of view. However, the tapered beam sections are fabricated from plate by welding, and are susceptible to imperfection effects. These may interact with the localised compressive stress field that is generated in the web at a slope change in the lower flange to cause local web buckling. A substantial parametric study using a non-linear elasto-plastic finite element program and covering practical ranges of the important parameters including the area of the tension flange, taper slope and web thickness is reported. Moment-rotation relations, peak moments and failure mechanisms have been predicted. The validity of the work is supported by the good correlation obtained between the results of the parametric study and experimental data.

Effect of ecological factors on germination of horse purslane (Trianthema portulacastrum)

Trianthema portulacastrum is a very problematic summer crop weed and a complete crop failure has been observed because of this weed at high density. The effect of different ecological factors on germination of T. portulacastrum seeds collected in two different years (2009 and 2005) was studied in laboratory experiments. An increase in temperature from 25 to 35 ºC increased germination percentage of T. portulacastrum from 65 to 85%, after which germination started to decrease, reducing to 71.25% at 45 ºC. Trianthema portulacastrum had maximum germination with distilled water compared with different salt solutions and drought stress levels. Germination was significantly minimum at salinity and drought stress level of 250 mM and -0.8 MPa, respectively. Emergence of T. portulacastrum was maximum (86.25%) at 100% field capacity level but decreased sharply as field capacity decreased thereafter, and minimum emergence (30%) was recorded at field capacity level of 25%. Germination of T. portulacastrum was lowest at pH 5 and any increase in pH resulted in increased germination. A pH range of 8 to 10 had statistically similar germination. Sowing depth of 6 cm reduced the emergence of T. portulacastrum to zero. Reduction in emergence was recorded with depth increase from zero to 5 cm. Maximum emergence was recorded from soil surface (0 cm). An increase in temperature, salinity, drought, sowing depth (up to 4 cm) and a decrease in field capacity increased time to start germination/emergence, time to 50% germination/emergence and mean germination/emergence time but decreased germination/emergence index. Seeds collected during 2009 gave higher germination than old seeds collected in 2005. This information might contribute to development of effective control of T. portulacastrum.

Evidence for a stress hypothesis: hemiparasitism effect on the colonization of Alchornea castaneaefolia A. Juss.uphorbiaceae) by Galling Insects

Stressed plants are generally more attacked by galling insects. In this study we investigated the relationship between population abundance and species richness of galling insects on the tree Alchornea castaneaefolia A. JUSS. (Euphorbiaceae), submited to stress induced by the hemiparasite Psittacanthus sp. (Loranthaceae) in the Amazon, Brazil. Branches of A. castaneaefolia attacked by the hemiparasite were more heavily infested by galling insects than non-attacked branches. The field observations partially corroborate the hypothesis that there would be an optimal level of host-plant stress for galling insect establishment.

Effects of clove oil on the stress response of matrinxã (Brycon cephalus) subjected to transport

Fish transport is one of the most stressful procedures in aquaculture facilities. The present work evaluated the stress response of matrinxã to transportation procedures, and the use of clove oil as an alternative to reduce the stress response to transport in matrinxã (Brycon cephalus). Clove oil solutions were tested in concentrations of 0, 1, 5 and 10 mg/L during matrinxã transportation in plastic bags, supplied with water and oxygen as the usual field procedures in Brazil. Clove oil reduced some of the physiological stress responses (plasma cortisol, glucose and ions) that we measured. The high energetic cost to matrinxã cope with the transport stress was clear by the decrease of liver glycogen after transport. Our results suggest that clove oil (5 mg/l) can mitigate the stress response in matrinxã subjected to transport.

Photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress

Light and water are important factors that may limit the growth and development of higher plants. The aim of this study was to evaluate photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress. I used six independent pre-acclimation treatments (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) and 720 min (06h00-18h00)) varying the time of exposure to full sunlight (PFS) during 30 days, followed by whole-day outdoor exposure for 120 days. Before PFS, the plants were kept in a greenhouse at low light levels (0.8 mol m-2 day-1). The PFS of 0 min corresponded to plants constantly kept under greenhouse conditions. From the beginning to the end of the experiment, each PFS treatment was submitted to two water regimes: moderate water stress (MWS, pre-dawn leaf water potential (ΨL) of -500 to -700 kPa) and without water stress (WWS, ΨL of -300 kPa, soil kept at field capacity). Plants under MWS received only a fraction of the amount of water applied to the well-watered ones. At the end of the 120-day-period under outdoor conditions, I evaluated light saturated photosynthesis (Amax), stomatal conductance (g s), transpiration (E) and plant growth. Both Amax and g s were higher for all plants under the PFS treatment. Stem diameter growth rate and Amax were higher for C. guianensis subjected to MWS than in well-watered plants. The contrary was true for B. excelsa. The growth of seedlings was enhanced by exposure to full sunlight for 180 minutes in both species. However, plants of B. excelsa were sensitive to moderate water stress. The higher photosynthetic rates and faster growth of C. guianensis under full sun and moderate water stress make this species a promissory candidate to be tested in reforestation programs.

Influence of seed size and ecological factors on the germination and emergence of field bindweed (Convolvulus arvensis)

An understanding of seed germination ecology of weeds can assist in predicting their potential distribution and developing effective management strategies. Influence of environmental factors and seed size on germination and seedling emergence of Convolvulus arvensis (field bindweed) was studied in laboratory and greenhouse conditions. Germination occurred over a wide range of constant temperatures, between 15 and 40 ºC, with optimum germination between 20 and 25 ºC. Time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased with an increase in temperature from 20 ºC, salinity and osmotic stress. However, germination was tolerant to low salt (25 mM) or osmotic stress (0.2 MPa), but as salinity and osmotic stress increased, germination percentage and germination index decreased. Seeds of C. arvensis placed at soil surface showed maximum emergence and decreased as seeding depth increased. Seeds of C. arvensis germinated over a wide range of pH (4 to 9) but optimum germination occurred at pH 6 to 8. Under highly alkaline and acidic pH, time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased. Increase in field capacity caused decreased time to start germination, time to 50% germination and mean germination time but increased germination percentage and germination index. Bigger seeds had low time to start germination, time to 50% germination and mean germination time but high germination percentage and germination index. Smaller seeds were more sensitive to environmental factors as compared to larger or medium seeds. It can be concluded that except for pH, all environmental factors and seed sizes adversely affect C. arvensis as regards seed germination or emergence and germination or emergence traits, and larger seeds result in improved stand establishment and faster germination than small seeds, regardless of moisture stress or deeper seeding depth.

Effect of repeated restraint stress on memory in different tasks

The present study investigated the effect of repeated stress applied to female rats on memory evaluated by three behavioral tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Repeated stress had different effects on rat behavior when different tasks were considered. In the two-way active avoidance test the stressed animals presented memory of the task, but their memory scores were impaired when compared to all other groups. In the habituation to the open field, only the control group showed a significant difference in the number of rearings between training and testing sessions, which is interpreted as an adequate memory of the task. In the handled and chronically stressed animals, on the other hand, no memory was observed, suggesting that even a very mild repeated stress would be enough to alter habituation to this task. The performance in the inhibitory avoidance task presented no significant differences between groups. The findings suggest that repeated restraint stress might induce cognitive impairments that are dependent on the task and on stress intensity.

TRP channels, omega-3 fatty acids, and oxidative stress in neurodegeneration: from the cell membrane to intracellular cross-links

The transient receptor potential channels family (TRP channels) is a relatively new group of cation channels that modulate a large range of physiological mechanisms. In the nervous system, the functions of TRP channels have been associated with thermosensation, pain transduction, neurotransmitter release, and redox signaling, among others. However, they have also been extensively correlated with the pathogenesis of several innate and acquired diseases. On the other hand, the omega-3 polyunsaturated fatty acids (n-3 fatty acids) have also been associated with several processes that seem to counterbalance or to contribute to the function of several TRPs. In this short review, we discuss some of the remarkable new findings in this field. We also review the possible roles played by n-3 fatty acids in cell signaling that can both control or be controlled by TRP channels in neurodegenerative processes, as well as both the direct and indirect actions of n-3 fatty acids on TRP channels.

What does the field of International Relations look like in South America?

Abstract This article provides a comprehensive picture of IR in South America by applying content analysis to 7,857 articles published in 35 journals from six South American countries from 2006 to 2014 in order to discover what the predominant theories, methods and research areas in this field are, how scholars tend to combine them in their research designs, and what the profiles of regional journals are, regarding their epistemological, methodological and subject preferences. The findings reveal a predominantly Positivist and largely Qualitative discipline, resembling North American and European IR.

Characterization of heat tolerance in wheat cultivars and effects on production components

Abstract: There is a need for heat tolerant wheat cultivars adapted to the expansion of cultivation areas in warmer regions due to the high demand of this cereal for human consumption. The objective of this study was to evaluate the effect of high temperatures on grain yield and yield components of wheat and characterize heat tolerant wheat genotypes at different development stages. The genotypes were evaluated in the field with and without heat stress. High temperatures reduced the number of spikelets per spike (21%), number of grains per spike (39%), number of grains per spikelet (23%), 1000-grain weight (27%) and grain yield (79%). Cultivars MGS 1 Aliança, Embrapa 42, IAC 24-Tucuruí and IAC 364-Tucuruí III are the most tolerant to heat stress between the stages double ridge and terminal spikelet; MGS 1 Aliança, BRS 264, IAC 24-Tucuruí, IAC 364-Tucuruí III and VI 98053, between meiosis and anthesis; and BRS 254, IAC-24-Tucuruí, IAC-364-Tucuruí III and VI 98053, between anthesis and physiological maturity. High temperatures reduce grain yield and yield components. The number of grains per spike is the most reduced component under heat stress. The genotypes differed in tolerance to heat stress in different developmental stages.

Nitrogen and potassium fertilization on the yield and intensity of the maize white spot

A plant's nutritional balance can influence its resistance to diseases. In order to evaluate the effect of increasing doses of N and K on the yield and severity of the mayze white spot, two experiments were installed in the field, one in the city of Ijaci, Minas Gerais, and the other in the city of Sete Lagoas, Minas Gerais. The experimental delimitation was in randomized blocks with 5 x 5 factorial analysis of variance, and four repetitions. The treatments consisted of five doses of N (20; 40; 80; 150; 190 Kg ha-1of N in the experiments 1 and 2) and five doses of K (15; 30; 60; 120; 180 Kg ha-1of K in experiment 1 and 8.75; 17.5; 35; 50; 100 Kg ha-1of K in experiment 2). The susceptible cultivar 30P70 was planted in both experiments. The plot consisted of four rows 5 meters long, with a useful area consisting of two central rows 3 meters each. Evaluations began 43 days after emergence (DAE) in the first experiment and 56 DAE in the second one. There was no significant interaction between doses of N and K and the disease progress P+. The effect was only observed for N. The K did not influence the yield and the severity of the disease in these experiments. Bigger areas below the severity progress curve of the white spot and better yield were observed with increasing doses of N. Thus, with increasing doses of N, the white spot increased and also did the yield.

Growth of sugar cane varieties under salinity

ABSTRACT Large salty areas in the Brazilian semi-arid region have limited farming in Northeastern Brazil. One example is the sugar cane cultivation, which reinforces the need of selecting varieties that are more tolerant to salinity. The objective of this study was to evaluate the effect of salinity on growth of ten varieties of sugar cane. The experiment was conducted in a greenhouse, set in the experimental field of Embrapa Semiárido, in Petrolina, Pernambuco State. The experimental design was randomized blocks arranged in a 6 X 10 factorial arrangement, comprised of six levels of salinity (0, 1.0, 2.0, 4.0, 6.0 and 8.0 dS m-1) and ten sugar cane varieties (VAT 90212; RB 72454; RB 867515; Q 124; RB 961003; RB 957508; SP791011; RB 835089; RB 92579 and SP 943206). Salt levels of irrigation water were obtained by adding NaCl, CaCl2.2H2O and MgSO4.7H2O to achieve an equivalent ratio among Na:Ca:Mg of 7:2:1. Sixty days later, plant height, stem diameter (base), number of leaves, stalks and sprouts, leaf area and fresh and dry mass of the aerial part and roots were all measured. The varieties of sugar cane showed similar responses for growth reduction as soil salinity increases, being considered moderately sensitive to salinity.

Prevenção de stress ocupacional em linha de montagem: um estudo de caso mexicano

Este estudo de caso apresenta a aplicação de uma metodologia, que inclui a análise ergonômica, a análise institucional, dinâmica de grupo e entrevistas individuais, em uma fábrica no México. O problema que provocou o estudo foi a queda de produtividade, relacionada pela direção da empresa com a existência de stress ocupacional. Utilizando-se da abordagem da pesquisa-ação, o estudo focalizou o pessoal de nível administrativo e de linha de montagem nos quais se podia observar sinais de stress. Foram identificadas as causas do problema e, com a participação dos envolvidos, foi estabelecido um programa de prevenção de stress ocupacional. Resultados positivos foram observados após a implementação do programa.

Student stress and quality of education

Today, managers are increasingly interested in knowing how the work in organizations aftects employees' health. Less common is the interest in stress erupting in the academic community - among students, faculty and administrators. The authors present a reflection paper focused on student stress. In this paper, they first examine McLean 's model of context, vulnerability and stressors. This model provides the framework for the student surveys and for the entire paper. Based on the students surveys, an assessment is made of how asma" group of students are coping with stress. The paper fina"y suggests what can be done by students, faculty, and administrators to insta" and/or improve social support systems that might reduce the harmful eftects of stress on students and thus impact the quality of education.