<p>As medições de temperatura em laboratórios didáticos frequentemente não levam em consideração o tempo morto dos sensores e dos sistemas de medição, sejam esses analógicos ou baseados na aquisição eletrônica de dados. Neste artigo são apresentadas medidas e comparações do tempo morto de diferentes tipos de termômetros, bem como algumas possibilidades e estratégias para a adaptação e controle dessa limitação em experimentos que envolvam medidas de temperatura de líquidos.</p>

<p>Temperature measurements in undergraduate laboratories often do not take into account the dead time of the sensors and measurement systems, whether analogic or based on electronic data acquisition. This paper presents measurements and comparisons of different types of dead time thermometers, as well as some possibilities and strategies for adaptation and control of this limitation in experiments involving temperature measurements of liquids.</p>

RESUMO Predadores generalistas são importantes para o controle biológico de pragas por se alimentarem de muitas espécies de insetos, especialmente daquelas em maior abundância, e por se manterem em diferentes agroecossistemas, mesmo em períodos de escassez de presa, tendo sido registrados em surtos de Lepidoptera desfolhadores em plantações de eucalipto. Foram estudados a longevidade e os parâmetros reprodutivos do predador Brontocoris tabidus (Signoret) (Heteroptera: Pentatomidae) a 26 ± 2° C, 65 ± 10% de U.R. e fotofase de 12 horas, alimentado com Tenebrio molitor L. (Coleoptera: Tenebrionidae) (T1) ou com esta presa e mudas de Eucalyptus grandis (T2). A longevidade de machos e fêmeas foi de 27,4 ± 4,4 e 39,6 ± 3,4 dias e de 27,0 ± 4,6 e 34,5 ± 3,1 dias, respectivamente. As fêmeas foram sempre mais pesadas que os machos, com 141,1 e 104,9 mg apenas com T. molitor, e 148,8 e 108,3mg com essa presa e mudas de E. grandis, respectivamente. A viabilidade dos ovos, o número de ovos/fêmea e a longevidade de B. tabidus foram maiores no tratamento com essa presa e mudas de E. grandis.

ABSTRACT Generalist predators are important for the biological control of pests by feeding on many insect pests, especially those occurring in larger abundance. For this reason, they can maintain their populations in different ecosystems, even during periods of prey shortage, and they are found in outbreaks of Lepidoptera defoliators in eucalyptus plantations. The longevity and reproductive parameters of the predatorBrontocoris tabidus (Signoret) (Heteroptera: Pentatomidae) were studied at 26 ± 2° C, 65 ± 10% relative humidity and 12 hours photophase with Tenebrio molitor L. (Coleoptera: Tenebrionidae) (T1) pupae or with this prey and seedlings of Eucalyptus grandis (T2). The longevity of males and females of this predator were 27.4 ± 4.4 and 39.6 ± 3.4 days and 27.0 ± 4.6 and 34.5 ± 3.1 days, respectively. Females were always heavier than males, with 141.1 and 104.9 mg only with T. molitor and 148.8 and 108.3 mg with this prey and E. grandis seedlings, respectively. The viability and number of eggs/female and the longevity of B. tabidus had higher values in the treatment with T. molitor pupae and seedlings of E. grandis.

Methyl mercury (MeHg) is highly neurotoxic, affecting visual function in addition to other central nervous system functions. The effect of mercury intoxication on the amplitude of horizontal cell responses to light was studied in the retina of the fish Hoplias malabaricus. Intracellular responses were recorded from horizontal cells of fish previously intoxicated with MeHg by intraperitoneal injection (IP group) or by trophic exposure (T group). Only one retina per fish was used. The doses of MeHg chloride administered to the IP group were 0.01, 0.05, 0.1, 1.0, 2.0, and 6.0 mg/kg. The amplitudes of the horizontal cell responses were lower than control in individuals exposed to 0.01 (N = 4 retinas), 0.05 (N = 2 retinas) and 0.1 mg/kg (N = 1 retina), whereas no responses were recorded in the 1.0, 2.0, and 6.0 mg/kg groups. T group individuals were fed young specimens of Astyanax sp previously injected with MeHg corresponding to 0.75 (N = 1 retina), 0.075 (N = 8 retinas) or 0.0075 (N = 4 retinas) mg/kg fish body weight. After 14 doses, one every 5 days, the amplitude of the horizontal cell response was higher than control in individuals exposed to 0.075 and 0.0075 mg/kg, and lower in individuals exposed to 0.75 mg/kg. We conclude that intoxication with MeHg affects the electrophysiological response of the horizontal cells in the retina, either reducing or increasing its amplitude compared to control, and that these effects are related to the dose and/or to the mode of administration.

Although healthy preterm infants frequently seem to be more attentive to visual stimuli and to fix on them longer than full-term infants, no difference in visual acuity has been reported compared to term infants. We evaluated the contrast sensitivity (CS) function of term (N = 5) and healthy preterm (N = 11) infants at 3 and 10 months of life using sweep-visual evoked potentials. Two spatial frequencies were studied: low (0.2 cycles per degrees, cpd) and medium (4.0 cpd). The mean contrast sensitivity (expressed in percentage of contrast) of the preterm infants at 3 months was 55.4 for the low spatial frequency (0.2 cpd) and 43.4 for the medium spatial frequency (4.0 cpd). At 10 months the low spatial CS was 52.7 and the medium spatial CS was 9.9. The results for the term infants at 3 months were 55.1 for the low spatial frequency and 34.5 for the medium spatial frequency. At 10 months the equivalent values were 54.3 and 14.4, respectively. No difference was found using the Mann-Whitney rank sum T-test between term and preterm infants for the low frequency at 3 or 10 months or for the medium spatial frequency at 3 or 10 months. The development of CS for the medium spatial frequency was equally fast for term and preterm infants. As also observed for visual acuity, CS was equivalent among term and preterm infants, suggesting that visual experience does not modify the development of the primary visual pathway. An earlier development of synapses in higher cortical visual areas of preterm infants could explain the better use of visual information observed behaviorally in these infants.

Although it has been demonstrated that nitric oxide (NO) released from sodium nitrite induces tetanic fade in the cat neuromuscular preparations, the effect of L-arginine on tetanic fade and its origin induced by NO have not been studied in these preparations. Furthermore, atropine reduces tetanic fade induced by several cholinergic and anticholinergic drugs in these preparations, whose mechanism is suggested to be mediated by the interaction of acetylcholine with inhibitory presynaptic muscarinic receptors. The present study was conducted in cats to determine the effects of L-arginine alone or after pretreatment with atropine or 1H-[1,2,4]oxadiazole [4,3-a]quinoxalin-1-one (ODQ) on neuromuscular preparations indirectly stimulated at high frequency. Drugs were injected into the middle genicular artery. L-arginine (2 mg/kg) and S-nitroso-N-acetylpenicillamine (SNAP; 16 µg/kg) induced tetanic fade. The N<FONT FACE="Symbol">w</font>-nitro-L-arginine (L-NOARG; 2 mg/kg) alone did not produce any effect, but reduced the tetanic fade induced by L-arginine. D-arginine (2 mg/kg) did not induce changes in tetanic fade. The tetanic fade induced by L-arginine or SNAP was reduced by previous injection of atropine (1.0 µg/kg) or ODQ (15 µg/kg). ODQ alone did not change tetanic fade. The data suggest that the NO-synthase-GC pathway participates in the L-arginine-induced tetanic fade in cat neuromuscular preparations. The tetanic fade induced by L-arginine probably depends on the action of NO at the presynaptic level. NO may stimulate guanylate cyclase increasing acetylcholine release and thereby stimulating presynaptic muscarinic receptors.

Spectral sensitivities of visual systems are specified as the reciprocals of the intensities of light (quantum fluxes) needed at each wavelength to elicit the same criterion amplitude of responses. This review primarily considers the methods that have been developed for electrophysiological determinations of criterion amplitudes of slow-wave responses from single retinal cells. Traditional flash methods can require tedious dark adaptations and may yield erroneous spectral sensitivity curves which are not seen in such modifications as ramp methods. Linear response methods involve interferometry, while constant response methods involve manual or automatic adjustments of continuous illumination to keep response amplitudes constant during spectral scans. In DC or AC computerized constant response methods, feedback to determine intensities at each wavelength is derived from the response amplitudes themselves. Although all but traditional flash methods have greater or lesser abilities to provide on-line determinations of spectral sensitivities, computerized constant response methods are the most satisfactory due to flexibility, speed and maintenance of a constant adaptation level

Este estudo avalia a evolução da sensibilidade in vitro do Plasmodium falciparum em uma área de prospecção de ouro no Estado do Amapá no período de 1983 a 1990. Foram efetuados 75 testes para cloroquina e quinino, 74 para amodiaquina e 76 para mefloquina. Os resultados revelaram 81% de resistência à cloroquina e 27% para a amodiaquina, enquanto que para quinino e mefloquina não foram evidenciadas cepas resistentes. Contudo, para estas duas últimas drogas identificou-se uma crescente perda da sensibilidade ao longo do tempo. Aparentemente observa-se uma associação entre resistência à cloroquina e a diminuição da sensibilidade ao quinino.

This study evaluates the sensitivity of P. falciparum in vitro to antimalarial drugs in an area ofgold mining exploration in Amapa State during theperiod ofl983 to 1990. The following tests were done, 75 in vitro studies with chloroquine and quinine, 74 with amodiaquine and 76 with mefloquine. The results showed 81 % ofresistance to chloroquine and 27% to amodiaquine while resistant strains to quinine and mefloquine were found. Also for these two quinolinomethanols a loss of sensitivity was noticed in the period of study. An association between resistance to chloroquine and decrease of sensitivity to quinine was also evident with the same strains.

O presente estudo avalia a resposta de cepas de Plasmodium falciparum às drogas antimaláricas, através de testes in vitro, isoladas em 7 municípios do sul do Estado do Pará. Foram efetuados 69 testes para cloroquina e mefloquina, 62 para amodiaquina e 61 para quinino. Os resultados mostram elevada resistência para cloroquina (71%), relativamente baixa resistência para amodiaquina com (25,8%) e para o quinino apenas 8,2%. Mefloquina revela ampla sensibilidade (100%), mas, demonstrando perda da mesma quando comparada em dois períodos distintos. Evidenciou-se também cepas multirresistentes em dois dos municípios estudados.

The responses of Plasmodium falciparum to antimalarial drugs were evaluated through the in vitro test using blood sample collected from patients of 7 municipalities of the south of Pará State. Sixty nine microtests for chloroquine and mefloquine, 62 for amodiaquine and 61 for quinine were pet formed. The results showed a high resistance for chloroquine (71%), a relatively low resistance level for amodiaquine (25.8%) and little resistance to quinine (8.2%). For mefloquine 100% of sensitivity was found.