Dielectric properties of Pb Nb2 O6 ferroelectric ceramics at cryogenic temperatures

Complex dielectric permittivity measurements in Pb Nb2 O6 ceramics were performed in a frequency and temperature range of 1 kHz-1 MHz and from 15 to 900 K, respectively. The results revealed two dielectric anomalies showing typical characteristics of relaxor ferroelectric materials at cryogenic temperatures. Comparison with other tetragonal tungsten bronze (TTB) structure-type materials suggests the existence of successive phase transitions, which until now were not reported. The observed low temperature dielectric behaviors seem to be due to intrinsic physical characteristics related to the TTB structure. © 2007 American Institute of Physics.

Temperature investigation of infrared-to-visible frequency upconversion in erbium-doped tellurite glasses excited at 1540 nm

Temperature investigation of infrared-to-visible frequency upconversion in erbium-doped tellurite glasses excited by CW laser radiation at 1540 nm and under cryogenic temperatures is reported. Intense upconversion emission signals around 530, 550 and 660 nm corresponding to the H-2(11/2), S-4(3/2), and F-4(9/2) transitions to the I-4(15/2) ground state were generated and studied as a function of the laser intensity and temperature. The upconversion excitation mechanism of the Er3+ ions emitting energy levels was accomplished via stepwise multiphoton absorption. The green upconversion luminescence exhibited a fivefold intensity enhancement when the temperature of the sample was varied in the range between 5 and 300 K. A maximum green upconversion intensity was attained around 120 K and a steady decreasing behavior for higher temperatures up to 300 K was observed. A model based upon conventional rate equations was used to model the observed temperature evolution of the upconversion luminescence. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Influence of the bipartite scrotum on the testicular and scrotal temperatures in goats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of different temperatures on the life history of Evania appendigaster L. (Hymenoptera: Evaniidae), a solitary oothecal parasitoid of Periplaneta americana L. (Dictyoptera: Blattidae)

The influence of temperatures on the life parameters of the solitary oothecal parasitoid Evania appendigaster, was investigated in the laboratory. Parasitized oothecae of Periplaneta americana were left to develop under seven constant temperatures: 15, 17, 20, 25, 30, 35, and 40 degrees C. At the end, we found that: (i) E. appendigaster was able to complete development within the temperature range of 17-34 degrees C; (ii) mean adult longevity decreased as temperature increased, with the temperature of 40 degrees C being fatal in a matter of hours; (iii) males lived longer than females between 15 and 30 degrees C; (iv) adult emergence rate was the highest at 25 degrees C, and (v) no wasps emerged at 15 or 40 degrees C. Non-emerged oothecae contained either unhatched eggs or dead larvae. We determined the theoretical lower developmental threshold and thermal constant for the complete development as 12.9 degrees C and 584.8 day-degrees for males, and 13.1 degrees C and 588.2 day-degrees for females, respectively. A good balance between faster development, maximum adult longevity and good egg viability was obtained between 25-30 degrees C, and that would be the best temperature range for rearing E. appendigaster. (C) 2009 Elsevier B.V. All rights reserved.

Multivariate analysis of fresh-cut carambola slices stored under different temperatures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Physical-chemical analysis of the cerebrospinal fluid of healthy dogs submitted to different storage periods and temperatures

Disfunções envolvendo o sistema nervoso são de grande importância na Medicina Veterinária, pois tratam-se de enfermidades de elevada incidência e com poucos subsídios auxiliares no seu diagnóstico, prognóstico e na avaliação de terapias empregadas. Ainda hoje, o diagnóstico baseia-se, em grande parte, no histórico e no exame clínico neurológico. Dessa forma, a análise dos constituintes do fluido cefalorraquidiano torna-se uma das poucas alternativas de acesso clínico ao sistema nervoso central (SNC). Mesmo com a grande utilidade do exame físico-químico e citoscópico do liquor na neurologia veterinária, poucos são os estudos sobre a estabilidade dos seus constituintes sob estocagem. Dessa forma, o presente trabalho teve como finalidade verificar a influência da temperatura e do tempo de conservação nas características físico-químicas do liquor de cães hígidos. Para tanto, foram coletadas amostras de LCR, através da punção da cisterna cerebelo-medular de cães clinicamente sadios, as quais foram submetidas à análise da densidade específica, do pH, da glicorraquia, das proteínas totais e das atividades das enzimas creatina quinase (CK) e aspartato aminotransferase (AST), após conservá-las em diferentes temperaturas (25°C, 4°C e -4°C) e por diferentes períodos de tempo (logo após a colheita, 24 horas, 48 horas, uma semana e um mês). Dentre os resultados obtidos, foi possível verificar, principalmente, que houve estabilidade dos parâmetros estudados por até um mês de estocagem nas amostras mantidas sob a temperaturas de congelamento de -4°C.

Fertility life table of Trichogramma pretiosum and Trichogramma acacioi (Hymenoptera : Trichogrammatidae) on Sitotroga cerealella (Lepidoptera : Gelechiidae) eggs at different constant temperatures

Fertility life tables were developed for both Trichogramma pretiosum and Trichogramma acacioi reared on Sitotroga cerealella eggs as an alternative host at five different temperatures. The egg parasitoids were first collected from Nipteria panacea eggs, a lepidopterous pest of avocado. Egg parasitoid females were individualized in small glass vials along with 40 eggs of the host during 24 h for parasitization. For evaluation of the parasitism capacity, a similar procedure was adopted, but cardboards with eggs were replaced every day. The net reproductive rate (Ro), intrinsic rate of increase (rm), finite rate of increase (lambda), and mean generation time (T) were estimated. Temperature affected all parameters for both Trichogramma species. The highest fecundity for both species was observed at 25degreesC. Extreme temperatures such as 15degreesC or 35degreesC negatively affect the development rate of both species.

Environmental temperature and cloacal and surface temperatures of broiler chicks in first week post-hatch

Adequate environmental temperature during the brooding period is very important to future broiler performance. Thus, the objective of this study was to investigate the extent to which environmental temperature affects the body weight and cloacal and surface (back, head, wing, and shank) temperatures. The study also investigated the sensible heat loss by radiation of broiler chicks reared at three environmental temperatures (35, 25, and 20 degrees C) up to 7 days of life. The results showed that chicks raised at low environmental temperature (20 degrees C) had lower body weight at 7 days of age. Birds kept at 20 degrees C also had significantly lower cloacal and surface temperatures than did other birds. The most marked difference was seen in the shanks. These findings revealed that body weight declined in chicks reared at 20 degrees C, and radiant heat loss (W) was nine times higher than for the birds kept at 35 degrees C at 7 days of age.

Influence of early quantitative food restriction on long bone growth at different environmental temperatures in broiler chickens

1. This investigation was carried out to study the influence of early quantitative food restriction (40% of ad libitum intake from 7 to 14 d of age) and environmental rearing temperature (thermoneutral, cold and hot) on long bone (tibia, femur and humerus) development in broiler chickens.2. Tibia, femur and humerus were obtained at the ages of 14, 21, 28, 35 and 42 d; and the variables studied were: length and width (mm, expressed as absolute values), bone breaking strength (kgf) and bone weight/bone length index (BW/BL, mg/mm).3. All bone variables increased with bird age. Food restriction reduced bone length and width but did not affect bone weight. High environmental rearing temperature reduced bone length and width at 42 d of age. Bone strength was not affected by environmental temperature but the calculated BW/BL index was reduced by heat exposure.4. The findings suggest that food restriction and high environmental rearing temperature reduce long bone growth; bone breaking strength was affected by bird age but not by food restriction nor rearing ambient temperature.

Yeast extract and prebiotic in pre-initial phase diet for broiler chickens raised under different temperatures

Objetivou-se nesta pesquisa avaliar o desempenho, o rendimento de carcaça e a morfometria intestinal de frangos de corte criados em diferentes temperaturas e que receberam na fase pré-inicial ração contendo ou não extrato de leveduras e prebiótico. Foram utilizados 1.440 pintos machos de 1 dia de idade, criados em diferentes câmaras climáticas. As rações, acrescidas ou não de extrato de leveduras e prebiótico, foram oferecidas somente na fase pré-inicial (1 a 7 dias). A partir do oitavo dia, todas as aves receberam a mesma ração, reajustada de acordo com as recomendações usuais. Adotou-se o delineamento experimental inteiramente casualizado em arranjo fatorial 3 × 2 × 2, composto de três temperaturas de criação (calor, conforto e frio) e dois níveis de extrato de leveduras (com ou sem) e prebiótico (com ou sem). O desempenho das aves foi avaliado considerando o ganho de peso, o consumo de ração, a conversão alimentar e a viabilidade aos 42 dias de idade. Também foram avaliados o rendimento de carcaça e a morfometria intestinal. O calor ambiente prejudicou o desempenho e o rendimento de carcaça. A inclusão de prebiótico na ração pré-inicial aumentou o ganho de peso e melhorou a conversão alimentar das aves criadas no calor. A inclusão dos produtos na ração de frangos de corte criados em ambiente de calor e no frio tem efeito benéfico sobre as vilosidades das aves.

Comparison of microbial numbers in soils by using various culture media and temperatures

The influence of different media and incubation temperatures on the quantification of microbial populations in sorghum, eucalyptus and forest soils was evaluated. Microbial growth was compared by using complex (tryptone soybean agar, TSA, casein-starch, CS, and Martin) and saline (Thorton, M3, Czapeck) media and incubation temperatures of 25 and 30° C. Higher numbers of total bacterial. and fungal colony-forming units (CFU) were observed in sorghum soils, and of spore-forming and Gram-negative bacteria in forest soils than other soils. Actinomycetes counts were highest in forest soil when using CS medium at 30° C and in sorghum soil at 25° C in M3 medium. Microorganism counts were dependent on the media and incubation temperatures. The counts at temperatures of 30° C were significantly higher than at 25° C. Microbial quantification was best when using TSA medium for total. and spore-forming bacteria, Thorton for Gram-negative bacteria, M3 for actinomycetes, and Martin for fungi. © 2005 Elsevier GmbH. All rights reserved.

Electrical conductivity as an indicator of pea seed aging of stored at different temperatures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Germination of Albizia hassleri seeds at different temperatures, under laboratory conditions

The objective of this study was to analyze the germination of seeds of Albizia hassleri under different temperatures. A completely random design arranged as a split plot for temperatures regimes, with 11 seed lots and four replications of 15 seeds was used. The plot was represented by the various lots and the sub plots for different temperatures. The means were compared by Scott-Knott test at 5% probability. The temperatures used were: a) constant: 20, 25 and 30 degrees C, and b) alternating: 20-30 and 25-35 degrees C. For all 11 seed lots the mean germination was 90%, speed germination index (IVG) was 5.059, fresh matter of seedlings (MMF) was 0.0628 g and dry matter (MMS) 0.0499 g. The variation coefficient (CV) between plots ranged from 8.48% for germination to 51.71% for dry matter of seedlings and sub plot of 6.77% to 60.45% for germination and MMS. These high values of CV, tested for MMS and MMF, indicate low repeatability of results within each treatment. In general, the IVG obtained at temperatures of 20 and 25 degrees C was lower than those in temperatures of 30, 20-30 and 25-35 degrees C. The best temperature for IVG was the alternating 25-35 degrees C and constant 30 degrees C. The germination test can be conducted at 30, 20-30 and 25-35 degrees C for 19 days.

Postharvest Conservation of Mature-Green and Ripe 'Paluma' Guava Stored at Two Temperatures

This work aimed to establish the importance of maturation and ripeness stages and the use of refrigeration for the conservation of 'Paluma' guavas. Fruit picked at the mature-green and ripe stages were stored at ambient conditions (21 degrees C and 85% RH) and also at 10 degrees C (85% RH). The fruit were evaluated every 2 or 3 days for weight loss, appearance, decay, color, firmness, soluble solids, titratable acidity, ascorbic acid, total polyphenols extractable content and total antioxidant activity. The fruit stored at 21 degrees C had higher weight loss than those stored at 10 degrees C. Mature-green guavas at 21 degrees C remained in good quality for 6 days, but at 10 degrees C, the preservation period increased to 15 days. Ripe fruit were preserved for 4 days at 21 degrees C, which was extended with refrigeration to 6 days. Mature-green fruit at 21 degrees C had decay in 6 days; while at 10 degrees C decay happened in 18 days. The peel color of mature-green fruits, at 21 degrees C, showed increasing values of luminosity, indicating that its color became lighter (change from green to yellow) and at 10 degrees C it showed constant values until the end of storage. Pulp firmness of mature-green fruit declined during storage as a result of ripening. In ripe fruits such reduction occurred more slowly, since they were softer. The color of the pulp became intense red for mature fruits. Soluble solids were lower in ripe fruit at 21 degrees C, while in mature fruits at 10 degrees C, it increased. The titratable acidity increased in fruits stored at 10 degrees C. The fruits kept at 21 degrees C and the mature guavas kept at 10 degrees C showed no changes in ascorbic acid content. The ripe fruit at 10 degrees C maintained their ascorbic acid levels. Mature guavas, stored at 10 degrees C, had the longest shelf life and higher contents of soluble solids and titratable acidity, with no changes in total polyphenols extractable content and total antioxidant activity.

Performance of layers submitted to different forced-molting methods and different temperatures

This study was carried out to evaluate the performance and egg quality of laying hens, in their second laying cycle submitted to different forced-molting methods and three environmental temperatures. Six hundred layers were distributed in a completely randomized experimental design with 15 treatments with five replicates of eight birds each, according to 5x3 factorial arrangement (molting methods vs. temperatures). The following forced-molting methods were applied: 90%, 70%, 50% dietary alfalfa inclusion, addition of 2,800 ppm zinc, and feed fasting. Temperatures were: 20 ºC, 27 ºC and 35 ºC. At the end of each period of the second laying cycle, bird performance and egg quality were evaluated. Data were submitted to analysis of variance and means were compared by orthogonal and polynomial contrasts. The highest alfalfa inclusion level (90% alfalfa and 10% basal diet) proved to be efficient as compared to the other methods, independently of temperature.