H-2 and H-infinity - norm control of intelligent structures using LMI techniques

Linear Matrix Inequalities (LMIs) is a powerful too] that has been used in many areas ranging from control engineering to system identification and structural design. There are many factors that make LMI appealing. One is the fact that a lot of design specifications and constrains can be formulated as LMIs [1]. Once formulated in terms of LMIs a problem can be solved efficiently by convex optimization algorithms. The basic idea of the LMI method is to formulate a given problem as an optimization problem with linear objective function and linear matrix inequalities constrains. An intelligent structure involves distributed sensors and actuators and a control law to apply localized actions, in order to minimize or reduce the response at selected conditions. The objective of this work is to implement techniques of control based on LMIs applied to smart structures.

Density and spatial distribution of Atta sexdens rubropilosa and Atta laevigata colonies (Hym., Formicidae) in Eucalyptus spp. forests

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Population dynamics of Leptopharsa heveae (Hemiptera: Tingidae) and Erythmelus tingitiphagus (Hymenoptera: Mymaridae) in rubber tree plants

The tingid Leptopharsa heveae, known as the lace bug, occurs in large populations in rubber tree plantations, limiting the production of latex due to losses of photosynthetic area and weakening of the infested trees. The alternative for the use of insecticides would be the release of biological control agents, but little is known about the natural enemies of L. heveae. The parasitoid Erythmelus tingitiphagus parasitizes eggs of the lace bug in rubber tree plantations. The knowledge of the population dynamics and the peak of occurrence of economically important insect species and their natural enemies are indispensable requirements for the establishment of efficient and rational control strategies. The objective of this work was to study the population dynamics of L. heveae and E. tingitiphagus in rubber tree plantations in the county of Itiquira, MT, Brazil. Mature folioles were collected weekly from the lower stratum of the canopy of the tree clones RRIM 600, PR 255, GT 1, PB 235 and PB 217, from August/2005 to February/2006. The parasitoid was observed during the whole study period. The population peaks of the populations of the L. heveae and E. tingitiphagus in the study area occurred at the end of October and beginning of November. This result demonstrates that measures for the control of L. heveae and population increase of E. tingitiphagus must be adopted before the peak population of this pest in cultivated rubber plantations.

A pest is a pest is a pest? The dilemma of neotropical leaf-cutting ants: Keystone taxa of natural ecosystems

Leaf-cutting ants of the genera Acromyrmex and Atta are considered the principal polyphagous pests of the Neotropics. Although some members of these genera are of economic importance, have a broad geographic distribution, and are extremely good colonizers, others are endemic and closely interact with native ecosystems. Control is generally practiced against any colony, irrespective of its taxonomic status. Indiscriminate control coupled with habitat destruction threatens endemic species with extinction, and, through habitat simplification, favors other pest species. As nests of Atta are large, having several square meters of nest surface, the endemic taxa can be easily used as environmental indicators for natural ecosystems. Likewise, the pest species can be used to detect environmental disturbance. As these ants are keystone species and easily identified by nonspecialists, efforts should be made to integrate these into viable conservation programs.

Potential of Acarophenax lacunatus (Prostigmata: Acarophenacidae) as a biological control agent of Rhyzopertha dominica (Coleoptera: Bostrichidae)

A recent report of the parasitic mite species Acarophenax lacunatus (Cross and Krantz) (Prostigmata: Acarophenacidae) attacking populations of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) led to the present investigation. Maximum female size and average number of progeny per female mite were assessed at eight different temperatures (ranging from 20 to 41°C) and 60% r.h. using R. dominica as the host. The ability of the mite species to suppress eggs, first instar larvae, and adults of R. dominica was assessed at 30°C and 60% r.h. The largest female sizes of the mite and progeny numbers were obtained around 30°C (259 μm and 17 offspring/female respectively) with minimum values obtained at the most extreme temperatures used in this study. Mite densities of at least four individuals per 500 ml jar containing 50 adults of R. dominica, resulted in almost complete suppression of eggs, first instar larvae, and adults of the host species after 45 days. This same range of mite densities led to reductions of wheat weight losses of 15 and 25% after 45 and 60 days after infestation respectively. Acarophenax lacunatus shows good potential as a biological control agent of R. dominica.

Effect of temperature on development and population growth of Acarophenax lacunatus (Cross and Krantz) (Prostigmata: Acarophenacidae) on Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The parasitic mite Acarophenax lacunatus kills the eggs upon which it feeds and seems to have potential as a biological control agent of stored grain pests. The lack of biological studies on this mite species led to the present study carried out in laboratory conditions at eight different temperatures (ranging from 20 to 41°C) and 60% relative humidity using Rhyzopertha dominica as host. The higher the temperature, the faster: (1) the attachment of female mites to the host egg (varying from 1 to 5 h); (2) the increase in body size of physogastric females (about twice faster at 40°C than at 20°C); and (3) the generation time (ranging from 40 to 220 h). In addition, the higher the temperature, the shorter the maximum female longevity (ranging from about 75 to 300 h). The two estimated temperature thresholds for development of A. lacunatus on R. dominica were 18 and 40°C. The average number of female and male offspring per gravid mite were 12.8 and 1.0, respectively, with sex ratios (females/total) ranging from 0.91 to 0.94 (maximum at 30°C). The net reproductive rate and intrinsic rate of increase also presented maximum values at 30°C (12.1 and 0.04, respectively).

External and internal structure of Atta bisphaerica Forel (Hymenoptera: Formicidae) nests

This work was carried out to determine the internal and external structures of Atta bisphaerica (Forel) nests. Six nests were excavated and during excavation, all data referring to chambers and tunnels were recorded. Three nests had been internally cement-moulded, which enabled a better view of the chamber and tunnel structures. Atta bisphaerica nests presented a similar structural pattern, varying only in the number of chambers as a function of external mound area. Chambers were spherical with two communication tunnels. Internal tunnels had an elliptical section, sometimes circular, indirectly linked to chambers through ramifications and directly through short tunnels. Entrance holes were linked to the area of highest chamber concentration by tunnels from the elliptical section, which led to the nest in a radial manner. Knowledge of the colony's three-dimensional architecture permits successful application of chemical control processes, reduces the quantity of product applied, and consequently diminishes costs and environmental damage.

Dynamics of handling time and functional response by larvae of Chrysomya albiceps (Dipt., Calliphoridae) on different prey species

One way to understand the behavioural patterns exhibited by a predator in response to prey density is to evaluate its functional response. Such evaluation yields information about basic mechanisms of prey-predator dynamics, and is an essential component of prey-predator models. In this paper we analysed experimentally the functional response and the handling time spent by Chrysomya albiceps on different prey species and larval instars of blowflies. The type II functional response was observed when second instar larvae of Chrysomya megacephala and Chrysomya macellaria were consumed. The handling time spent by the predator was significantly different between instars and species. The implications of the functional response and handling time for the interaction dynamics of Brazilian Chrysomyinae species are discussed.

Effects of hand weeding strip and nitrogen fertilizer on corn plants

The objective of the present research was to evaluate effects of different strip weed control associated with nitrogen fertilizer on corn applied after planting. The experiment was set and conducted in Botucatu, São Paulo State, Brazil, and the hybrid planted was Dekalb 333-B. A completely randomized block design with four replications was used. Experimental plots were disposed as a factorial scheme 2 x 2 x 4, constituted by two types of weeding on row (with or without manual hoeing), two types of weeding on inter-row (with or without manual hoeing), and four nitrogen levels applied after planting (00, 60, 90, and 120 kg ha-1). Plots were composed by six rows with 5 m length. Nitrogen fertilizer was applied at 35 days after emergence (d.a.e). For weed community it was evaluated: weed density, dominancy, frequency, and relative importance. The main weed species were: Brachiaria plantiginea, Amaranthus retroflexus, Bidens pilosa, Cyperus rotunds, Brachiaria decumbens, Euphorbia heterofila, Oxalis latifolia, Acanthospermum hispidum, Commelina benghalensis. It was evaluated corn height at 40 and 100 d.a.e., first ear insertion height at 100 d.a.e., and final grain yield at harvesting. Plants and first ear insertion height were affected when nitrogen fertilizer was not applied. Treatments without weed control showed that weed interfered negatively with plants height. There were no correlation between weeds and nitrogen fertilizer for all parameters evaluated. Parcels without weed showed the highest ear weights and final grain production. Treatments that received nitrogen fertilizer, independently of studied arrangement, provided higher yields.

Absorption and translocation of 2,4-D in plants of Memora peregrina

The objective of this work was to evaluate absorption and translocation of the herbicide 2,4-D in plants of Memora peregrina. The herbicide 2,4-D was used alone with the formulation DMA 806 BR and associated with the herbicide picloram in the commercial product Padron. Levels of radioactivity on the treated leaves were determined in sample obtained after washing them with methanol and chloroform at different times after the application of the radiolabelled formulation (1, 2, 4, 8, 24, and 48 h). Translocation was evaluated by cutting plants between stem and root. The parts obtained were: root, stem, leaf treated, leaves above the leaf treated, leaves below the leaf treated, and leaf opposite of the leaf treated. These parts were weighted, dried, ground, burnt, and radioactivity in the samples was determined. The results suggest that the translocation of the radioactive herbicide 2,4-D was insignificant in plants of M. peregrina in the two treatments evaluated. Absorption of 14C 2,4-D in the treatment with DMA 806 BR and the mixture of DMA 806 BR plus Padron had the same behavior. These observations explain the inefficient control obtained with this herbicide in plant species under study.

Interval between first dose and booster affected antibody production in cattle vaccinated against rabies

In this study, we compared the levels of neutralizing antibodies induced by inactivated rabies vaccine in cattle by using three alternative immunization procedures. Forty-five bovines (breed nelore) were then organized in three groups (A, B and C, with 15 animals/group). Group A received only one vaccine dose at day zero and Group B received the first dose at day zero and then another dose at day 30 (early booster). Group C was also immunized with two doses; however, the booster was postponed until day 180 after the first dose (delayed booster). Blood samples were withdrawn at days zero (before the first dose) and 30, 210, 390, and 540 after the beginning of immunization and the antibody titers were evaluated by mouse neutralization test. The protocol used to immunize Group C (booster at day 180) was clearly more efficient. In this group, antibody levels were higher and also remained higher for longer periods in comparison with the other two groups. These results show that booster timing significantly affected antibody levels. Therefore, programs addressed to control this disease in cattle should consider not only the use of a booster but also its administration time.

Pattern of silver nitrate-staining during meiosis and spermiogenesis in testicular lobes of Antiteuchus tripterus (Heteroptera: Pentatomidae)

The pattern of silver nitrate (Ag)-staining differed among testicular lobes of Antiteuchus tripterus. In general, these differences are in regard to the number, size, shape, coloring intensity, and location of the stained bodies or masses, observed during meiosis and spermiogenesis. These characteristics were similar in lobes 1-3. Lobes 4-6, however, differed from each other and from lobes 1-3 as well. Because the Ag-staining method is specific for nucleolar organizing regions and nucleolar material, the observations in meiosis of lobes 1-3 suggested the presence of a single pair of nucleolar organizing region-bearing chromosomes in A. tripterus, as previously found in other Pentatomidae species. In general, the amount of Ag-stained material seen in meiosis of the testicular lobes 1-3 of A. tripterus is smaller than in the other lobes. The differences among lobes observed during spermiogenesis included a striking variation in morphology of the Ag-stained material found in the head and tail of the spermatids. Given that the key role of the nucleolar material is to participate in protein synthesis, interlobular variations seem to be related to the different functions attributed to each lobe (reproduction to lobes 1-3 and basically nutrition to lobes 4-6). To our knowledge, this is the first time that the nucleolar material was studied in each testicular lobe during spermatogenesis. The present observations encourage further studies since, in addition to being of basic biological interest, several Pentatomidae species are agricultural pests and added knowledge of their biology, mainly in reproduction, may be important for the development of control strategies. ©FUNPEC-RP.

Effects of atrazine on female Wistar rats: Morphological alterations in ovarian follicles and immunocytochemical labeling of 90 kDa heat shock protein

Fertility in female mammals may be affected by a variety of endocrine disrupters present in the environment. Herbicide atrazine is an example of endocrine disrupter employed in agriculture, which disrupts estrous cyclicity in rats. Aiming to characterize morphologically the effect of low and sublethal doses of atrazine on the ovaries of Wistar rats, in an effort to determine the possible intrafollicular target site through which this herbicide acts adult females were submitted to both subacute and subchronic treatments. Additionally, immunocytochemical labeling of 90 kDa heat shock protein (HSP90) was performed in order to evaluate the role played by this protein in the ovary, under stressed conditions induced by herbicide exposure. The results indicated that atrazine induced impaired folliculogenesis, increased follicular atresia and HSP90 depletion in female rats submitted to subacute treatment, while the subchronic treatment with low dose of atrazine could compromise the reproductive capacity reflected by the presence of multioocytic follicle and stress-inducible HSP90. © 2007 Elsevier Ltd. All rights reserved.

Calcium silicate and organic mineral fertilizer applications reduce phytophagy by Thrips palmi Karny (Thysanoptera: Thripidae) on eggplants (Solanum melongena L.)

Thrips palmi Karny (Thysanoptera: Thripidae) is a phytophagous insect associated with the reduction of eggplant productivity. The aim of this study was to evaluate the effect of calcium silicate and/or an organic mineral fertilizer, together or separately, in increasing the resistance of eggplants to T. palmi. The treatments were calcium silicate, organic mineral fertilizer, calcium silicate associated with this fertilizer and the control. Mortality and number of lesions caused by nymphs of this insect on eggplant leaves were evaluated after 3, 6, 9 and 12 leaf applications of these products. The calcium silicate and the organic mineral fertilizer reduced both the population of T. palmi and the damage caused by its nymphs, suggesting a possible increase in eggplant resistance to this pest as a result of the treatments.