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Avaliação da cinética de crescimento, resistência ácida e resistência térmica de Salmonella enteritidis envolvida em surtos alimentares ocorridos no Rio Grande do Sul e comparação com outros sorovares; Growth kinetics, acid and thermal resistance of Salmonella enteritidis involved in foodborne outbreaks occurred in the Rio Grande do Sul state and comparation with other serovars

Malheiros, Patricia da Silva
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
66.05%
No período de 1999 a 2002, uma linhagem de Salmonella Enteritidis esteve envolvida em mais de 90% das salmoneloses ocorridas no RS. Este trabalho teve por objetivo avaliar a cinética de crescimento, a resistência ácida e a resistência térmica dessa linhagem e compará-la com S. Typhimurium e S. Bredeney não envolvidas em surtos alimentares, porém isoladas na mesma região. Em uma primeira etapa, a cinética de crescimento foi avaliada semeando-se cada sorovar em caldo nutriente (CN) e em salada de batata com maionese caseira (SMC), os quais foram mantidos a 30°C e 9,5°C. Em CN, a cinética de crescimento a 30°C foi semelhante para todos os sorovares, porém, em SMC a S. Enteritidis apresentou maior quantidade de células nas primeiras 6 horas de crescimento, sendo que somente depois de 12 horas todos os sorovares atingiram quantidades semelhantes de células. Em CN e em SMC, na temperatura de 9,5°C, não foi detectado crescimento de nenhum dos sorovares de Salmonella durante as primeiras 24 horas, sugerindo que essa temperatura foi suficiente para controlar a multiplicação desses microrganismos. Em uma segunda etapa, avaliou-se a resistência ácida e térmica dos diferentes sorovares de Salmonella. Para tanto, os três sorovares foram inoculados separadamente em CN e CN enriquecido com 1% de glicose (CNG)...

Cinética de crescimento de Salmonella enteritidis envolvida em surtos alimentares no RS : uma comparação com linhagens de outros sorovares; Growth kinetics of Salmonella Enteritidis involved in outbreaks of foodborne illness in Rio Grande do Sul, southern Brazil: a comparison with other serovar strains

Malheiros, Patricia da Silva; Paula, Cheila Minéia D. de; Tondo, Eduardo Cesar
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
66.01%
No período de 1999 a 2002, uma linhagem geneticamente caracterizada de Salmonella Enteritidis esteve envolvida em mais de 90% das salmoneloses ocorridas no RS. Este trabalho teve por objetivo avaliar a cinética de crescimento dessa linhagem, comparando-a com o crescimento de uma linhagem de S. Typhimurium e de S. Bredeney não envolvida em surtos alimentares. Para tanto, cada linhagem foi semeada separadamente em caldo nutriente (CN) e em salada de batata com maionese caseira (SMC), os quais foram mantidos a 30 °C e 9,5 °C. Os resultados obtidos em laboratório foram comparados com os resultados modelados pelo Pathogen Modelling Program, USDA. Em CN, a cinética de crescimento a 30 °C foi semelhante para todas as linhagens, as quais atingiram aproximadamente 8 log UFC.mL–1. Em SMC, a 30 °C, a linhagem de S. Enteritidis apresentou maior quantidade de células nas primeiras 6 horas de crescimento, sendo que somente depois de 12 horas todos os microrganismos testados atingiram quantidades semelhantes de células, ou seja, aproximadamente 6 log UFC g –1. Em CN e em SMC, na temperatura de 9,5 °C, não foi detectado crescimento de nenhuma das linhagens testadas de Salmonella durante as primeiras 24 horas, sugerindo que essa temperatura foi suficiente para controlar a multiplicação desses microrganismos. A modelagem bacteriana confirmou a maioria dos resultados obtidos.; From 1999 to 2002...

Digital monitoring of mycelium growth kinetics and vigor of shiitake (Lentinula edodes (Berk.) Pegler) on agar medium

Montini, Renato Mamede de Castro; Passos, José Raimundo de Souza; Eira, Augusto Ferreira da
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: 90-95
Português
Relevância na Pesquisa
56.08%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Avaliou-se o crescimento e vigor das linhagens LE 96/17, LE 98/51, LE 98/53 e LE 98/56 de Lentinula edodes (Berk) Pegler em diferentes composições de meio de cultura. As linhagens foram provenientes da Micoteca do Módulo de Cogumelos da Faculdade de Ciências Agronômicas, Unesp, Campus de Botucatu. Os isolados foram obtidos por propagação vegetativa, pela transferência asséptica do micélio para o meio de cultura de extrato de serragem-dextrose-ágar. O crescimento e vigor do micélio foi fotografado diariamente com uma câmera digital, durante a incubação, até a colonização total da placa de Petri. As imagens foram analisadas pelo programa UTHSCSA ImageTool (freeware), versão 2.0, desenvolvido pela University of Texas Health Science Center, San Antonio, Texas. O modelo estatístico que melhor explicou a cinética de crescimento miceliano em área (mm²), das linhagens de cogumelos L. edodes, tem como componente determinístico a exponencial de uma função Gompertz. O vigor, avaliado através da cor do micélio (em escala de tons do cinza), revelou um comportamento similar entre as linhagens...

Kinetics of biodegradation of diethylketone by Arthrobacter viscosus

Costa, Filomena; Quintelas, C.; Tavares, M. T.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
Relevância na Pesquisa
46.05%
The performance of an Arthrobacter viscosus culture to remove diethylketone from aqueous solutions was evaluated. The effect of initial concentration of diethylketone on the growth of the bacteria was evaluated for the range of concentration between 0 and 4.8 g/l, aiming to evaluate a possible toxicological effect. The maximum specific growth rate achieved is 0.221 h-1 at 1.6 g/l of initial diethylketone concentration, suggesting that for higher concentrations an inhibitory effect on the growth occurs. The removal percentages obtained were approximately 88%, for all the initial concentrations tested. The kinetic parameters were estimated using four growth kinetic models for biodegradation of organic compounds available in the literature. The experimental data found is well fitted by the Haldane model (R2 = 1) as compared to Monod model (R2 = 0.99), Powell (R2 = 0.82) and Loung model (R2 = 0.95). The biodegradation of diethylketone using concentrated biomass was studied for an initial diethylketone concentration ranging from 0.8–3.9 g/l in a batch with recirculation mode of operation. The biodegradation rate found followed the pseudo-second order kinetics and the resulting kinetic parameters are reported. The removal percentages obtained were approximately 100%...

An approach to the metabolic degradation of diethylketone (DEK) by Streptococcus equisimilis : effect of DEK on the growth, biodegradation kinetics and efficiency

Costa, Filomena; Quintelas, C.; Tavares, M. T.
Fonte: Elsevier BV Publicador: Elsevier BV
Tipo: Artigo de Revista Científica
Publicado em /09/2014 Português
Relevância na Pesquisa
46.05%
Abstract The degradation of diethylketone by Streptococcus equisimilis was evaluated. The toxicity of diethylketone was assessed evaluating the growth of the bacteria for the range of diethylketone concentration between 0 and 6.4 g L−1. The maximum specific growth rate achieved is 0.555 h−1 at 3.2 g L−1 of initial diethylketone concentration, followed by a slight decrease, suggesting that higher concentrations of diethylketone negatively affect the growth. The biodegradation efficiency (%) obtained was approximately 95%, for all the initial concentrations tested. The kinetic parameters were estimated using Monod, Powell, Haldane and Loung models. The experimental data is well fitted by the Loung and Haldane models, R2 = 0.98 for both, as compared to Monod model (R2 = 0.79) and Powell model (R2 = 0.72). Once the previous intrinsic functions were established, a set of assays was also performed to evaluate the biodegradation of diethylketone using concentrated biomass for initial diethylketone concentrations ranging from 0.8 to 3.9 g L−1 in a bioreactor operating in batch mode with recirculation. These concentrated biomass assays aimed the optimization of operational conditions. The removal percentages obtained were approximately 100%...

Digital monitoring of mycelium growth kinetics and vigor of shiitake (Lentinula edodes (Berk.) Pegler) on agar medium

Montini,Renato Mamede de Castro; Passos,José Raimundo de Souza; Eira,Augusto Ferreira da
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2006 Português
Relevância na Pesquisa
56.08%
The mycelium growth kinetics and vigor of shiitake (Lentinula edodes (Berk.) Pegler) strains LE 96/17, LE 98/51, LE 98/53, and LE 98/56 were studied under different agar medium compositions. The strains were from the mycological collection of the Módulo de Cogumelos, Faculdade de Ciências Agronômicas, Unesp-Botucatu, Brazil. Mycelium fragments from stock cultures were transferred to Petri dishes with Sawdust extract-Dextrose-Agar medium. The area of growth and vigor (density) of the mycelia were daily recorded with a digital camera, during incubation, until the complete colonization of the Petri dish. The images were analyzed by the freeware UTHSCSA ImageTool, v. 2.0, developed by the University of Texas Health Science Center, San Antonio. The kinetics of mycelium growth, as measured by the mycelium area (mm²), has as a deterministic component an exponential function of Gompertz. The vigor, as evaluated by mycelium color in gray scale, was similar for all strains, reached a maximal value between the 4th and 5th day of incubation and decreased further on. The velocity of growth of L. edodes strains was lower in enriched culture media, while vigor was higher. Digital monitoring permits a objective evaluation of the growth kinetics of L. edodes in vitro.

Growth kinetics of Mycobacterium tuberculosis measured by quantitative resazurin reduction assay: a tool for fitness studies

von Groll,Andrea; Martin,Anandi; Portaels,Françoise; Silva,Pedro Eduardo Almeida da; Palomino,Juan Carlos
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 Português
Relevância na Pesquisa
66.01%
We standardized a method to evaluate the growth kinetics of Mycobacterium tuberculosis by measuring quantitatively the reduction of resazurin by spectrophotometry. Growth curves and the rate of growth of twenty-one M. tuberculosis clinical isolates were determined. The method showed technical simplicity and is inexpensive to assess the fitness of each isolate.

Growth and biopigment accumulation of cyanobacterium Spirulina platensis at different light intensities and temperature

Kumar,Manoj; Kulshreshtha,Jyoti; Singh,Gajendra Pal
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2011 Português
Relevância na Pesquisa
55.96%
In order to find out optimum culture condition for algal growth, the effect of light irradiance and temperature on growth rate, biomass composition and pigment production of Spirulina platensis were studied in axenic batch cultures. Growth kinetics of cultures showed a wide range of temperature tolerance from 20 ºC to 40 ºC. Maximum growth rate, cell production with maximum accumulation of chlorophyll and phycobilliproteins were found at temperature 35 ºC and 2,000 lux light intensity. But with further increase in temperature and light intensity, reduction in growth rate was observed. Carotenoid content was found maximum at 3,500 lux. Improvement in the carotenoid content with increase in light intensity is an adaptive mechanism of cyanobacterium S.platensis for photoprotection, could be a good basis for the exploitation of microalgae as a source of biopigments.

Growth Kinetics of Suspended Microbial Cells: From Single-Substrate-Controlled Growth to Mixed-Substrate Kinetics

Kovárová-Kovar, Karin; Egli, Thomas
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/1998 Português
Relevância na Pesquisa
46.2%
Growth kinetics, i.e., the relationship between specific growth rate and the concentration of a substrate, is one of the basic tools in microbiology. However, despite more than half a century of research, many fundamental questions about the validity and application of growth kinetics as observed in the laboratory to environmental growth conditions are still unanswered. For pure cultures growing with single substrates, enormous inconsistencies exist in the growth kinetic data reported. The low quality of experimental data has so far hampered the comparison and validation of the different growth models proposed, and only recently have data collected from nutrient-controlled chemostat cultures allowed us to compare different kinetic models on a statistical basis. The problems are mainly due to (i) the analytical difficulty in measuring substrates at growth-controlling concentrations and (ii) the fact that during a kinetic experiment, particularly in batch systems, microorganisms alter their kinetic properties because of adaptation to the changing environment. For example, for Escherichia coli growing with glucose, a physiological long-term adaptation results in a change in KS for glucose from some 5 mg liter−1 to ca. 30 μg liter−1. The data suggest that a dilemma exists...

Generality of the growth kinetics of the average individual cell in different bacterial populations.

Trueba, F J; Neijssel, O M; Woldringh, C L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1982 Português
Relevância na Pesquisa
46.08%
The kinetics of growth of all the cells in a population is reflected in the shape of the size distribution of the population. To ascertain whether the kinetics of growth of the average individual cell is similar for different strains or growth conditions, we compared the shape of normalized size distributions obtained from steady-state populations. Significant differences in the size distributions were found, but these could be ascribed either to the precision achieved at division or to a constriction period which is long relative to the total cell cycle time. The remaining difference is quite small. Thus, without establishing the pattern itself, it is concluded that the basic course of growth is very similar for the various Escherichia coli strains examined and probably also for other rod-shaped bacteria. The effects of differences in culture technique (batch or chemostat culture), growth rate, and differences among strains were not found to influence the shape of the size distributions and hence the growth kinetics in a direct manner; small differences were found, but only when the precision at division or the fraction of constricted cells (long constriction period) were different as well.

Growth Kinetics of Thiobacillus ferrooxidans Isolated from Arsenic Mine Drainage

Braddock, Joan Forshaug; Luong, Huan V.; Brown, Edward J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1984 Português
Relevância na Pesquisa
46.11%
Thiobacillus ferrooxidans is found in many Alaskan and Canadian drainages contaminated by metals dissolved from placer and lode gold mines. We have examined the iron-limited growth and iron oxidation kinetics of a T. ferrooxidans isolate, AK1, by using batch and continuous cultures. Strain AK1 is an arsenic-tolerant isolate obtained from placer gold mine drainage containing large amounts of dissolved arsenic. The steady-state growth kinetics are described with equations modified for threshold ferrous iron concentrations. The maximal specific growth rate (μmax) for isolate AK1 at 22.5°C was 0.070 h−1, and the ferrous iron concentration at which the half-maximal growth rate occurred (Kμ) was 0.78 mM. Cell yields varied inversely with growth rate. The iron oxidation kinetics of this organism were dependent on biomass. We found no evidence of ferric inhibition of ferrous iron oxidation for ferrous iron concentrations between 9.0 and 23.3 mM. A supplement to the ferrous medium of 2.67 mM sodium arsenite did not result in an increased steady-state biomass, nor did it appear to affect the steady-state growth kinetics observed in continuous cultures.

Growth Kinetics of Hyphomicrobium and Thiobacillus spp. in Mixed Cultures Degrading Dimethyl Sulfide and Methanol▿

Hayes, Alexander C.; Liss, Steven N.; Allen, D. Grant
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.06%
The growth kinetics of Hyphomicrobium spp. and Thiobacillus spp. on dimethyl sulfide (DMS) and methanol (in the case of Hyphomicrobium spp.) in an enrichment culture created from a biofilter cotreating DMS and methanol were studied. Specific growth rates of 0.099 h−1 and 0.11 h−1 were determined for Hyphomicrobium spp. and Thiobacillus spp., respectively, growing on DMS at pH 7. These specific growth rates are double the highest maximum specific growth rate for bacterial growth on DMS reported to date in the literature. When the pH of the medium was decreased from pH 7 to pH 5, the specific growth rate of Hyphomicrobium spp. decreased by 85%, with a near 100-fold decline in the yield of Hyphomicrobium 16S rRNA gene copies in the mixed culture. Through the same pH shift, the specific growth rate and 16S rRNA gene yield of Thiobacillus spp. remained similar. When methanol was used as a substrate, the specific growth rate of Hyphomicrobium spp. declined much less over the same pH range (up to 30%) while the yield of 16S rRNA gene copies declined by only 50%. Switching from an NH4+-N-based source to a NO3−-N-based source resulted in the same trends for the specific growth rate of these microorganisms with respect to pH. This suggests that pH has far more impact on the growth kinetics of these microorganisms than the nitrogen source. The results of these mixed-culture batch experiments indicate that the increased DMS removal rates observed in previous studies of biofilters cotreating DMS and methanol are due to the proliferation of DMS-degrading Hyphomicrobium spp. on methanol at pH levels not conducive to high growth rates on DMS alone.

Highly Sensitive Quantitative Imaging for Monitoring Single Cancer Cell Growth Kinetics and Drug Response

Mir, Mustafa; Bergamaschi, Anna; Katzenellenbogen, Benita S.; Popescu, Gabriel
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/02/2014 Português
Relevância na Pesquisa
46.07%
The detection and treatment of cancer has advanced significantly in the past several decades, with important improvements in our understanding of the fundamental molecular and genetic basis of the disease. Despite these advancements, drug-screening methodologies have remained essentially unchanged since the introduction of the in vitro human cell line screen in 1990. Although the existing methods provide information on the overall effects of compounds on cell viability, they are restricted by bulk measurements, large sample sizes, and lack capability to measure proliferation kinetics at the individual cell level. To truly understand the nature of cancer cell proliferation and to develop personalized adjuvant therapies, there is a need for new methodologies that provide quantitative information to monitor the effect of drugs on cell growth as well as morphological and phenotypic changes at the single cell level. Here we show that a quantitative phase imaging modality known as spatial light interference microscopy (SLIM) addresses these needs and provides additional advantages over existing proliferation assays. We demonstrate these capabilities through measurements on the effects of the hormone estradiol and the antiestrogen ICI182...

New Observations and Insights into the Morphology and Growth Kinetics of Hydrate Films

Li, Sheng-Li; Sun, Chang-Yu; Liu, Bei; Li, Zhi-Yun; Chen, Guang-Jin; Sum, Amadeu K.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 19/02/2014 Português
Relevância na Pesquisa
46.12%
The kinetics of film growth of hydrates of methane, ethane, and methane-ethane mixtures were studied by exposing a single gas bubble to water. The morphologies, lateral growth rates, and thicknesses of the hydrate films were measured for various gas compositions and degrees of subcooling. A variety of hydrate film textures was revealed. The kinetics of two-dimensional film growth was inferred from the lateral growth rate and initial thickness of the hydrate film. A clear relationship between the morphology and film growth kinetics was observed. The shape of the hydrate crystals was found to favour heat or mass transfer and favour further growth of the hydrate film. The quantitative results on the kinetics of film growth showed that for a given degree of subcooling, the initial film thicknesses of the double hydrates were larger than that of pure methane or ethane hydrate, whereas the thickest hydrate film and the lowest lateral growth rate occurred when the methane mole fraction was approximately 0.6.

Growth kinetics of plasma-polymerized films

Hwang, Sukyoung; Seo, Hosung; Jeong, Dong-Cheol; Wen, Long; Han, Jeon Geon; Song, Changsik; Kim, Yunseok
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 18/06/2015 Português
Relevância na Pesquisa
46.05%
The growth kinetics of polymer thin films prepared by plasma-based deposition method were explored using atomic force microscopy. The growth behavior of the first layer of the polythiophene somewhat differs from that of the other layers because the first layer is directly deposited on the substrate, whereas the other layers are deposited on the polymer itself. After the deposition of the first layer, each layer is formed with a cycle of 15 s. The present work represents the growth kinetics of the plasma-polymerized films and could be helpful for further studies on growth kinetics in other material systems as well as for applications of plasma-polymerized thin films.

Growth kinetics of mycobacterium tuberculosis measured by quantitative resazurin reduction assay: a tool for fitness studies

Groll, Andrea Von; Martin, Anandi; Portaels, Fran??oise; Silva, Pedro Eduardo Almeida da; Palomino, Juan Carlos
Fonte: Universidade Federal do Rio Grande Publicador: Universidade Federal do Rio Grande
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.01%
We standardized a method to evaluate the growth kinetics of Mycobacterium tuberculosis by measuring quantitatively the reduction of resazurin by spectrophotometry. Growth curves and the rate of growth of twenty-one M. tuberculosis clinical isolates were determined. The method showed technical simplicity and is inexpensive to assess the fitness of each isolate.

Catechol biodegradation kinetics using Candida parapsilopsis

Rigo,Maurício; Alegre,Ranulfo Monte; Bezerra,José Raniere Mazile Vidal; Coelho,Narjara; Bastos,Reinaldo Gaspar
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2010 Português
Relevância na Pesquisa
55.91%
This study evaluated the biodegradation of catechol by a yeast strain of Candida parapsilopsis in standard medium in Erlenmeyer flasks. Results shown that the highest concentration of catechol caused the longer lag period, demonstrating that acclimatized cultures could completely degrade an initial catechol concentration of 910 mg/L within 48 h. Haldane's model validated the experimental data adequately for growth kinetics over the studied catechol concentration ranges of 36 to 910 mg/L. The constants obtained for this model were µmax = 0.246 h-1, Ks = 16.95 mg/L and Ki = 604.85 mg/L.

Large-scale Epitaxial Growth Kinetics of Graphene: A Kinetic Monte Carlo Study

Jiang, Huijun; Hou, Zhonghuai
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.05%
Epitaxial growth via chemical vapor deposition is considered to be the most promising way towards synthesizing large area graphene with high quality. However, it remains a big theoretical challenge to reveal growth kinetics with atomically energetic and large-scale spatial information included. Here, we propose a minimal kinetic Monte Carlo model to address such an issue on an active catalyst surface with graphene/substrate lattice mismatch, which facilitates us to perform large scale simulations of the growth kinetics over two dimensional surface with growth fronts of complex shapes. A geometry-determined large-scale growth mechanism is revealed, where the rate-dominating event is found to be $C_{1}$-attachment for concave growth front segments and $C_{5}$-attachment for others. This growth mechanism leads to an interesting time-resolved growth behavior which is well consistent with that observed in a recent scanning tunneling microscopy experiment.; Comment: 5 pages, 3 figures

Feeding and growth kinetics of the planktotrophic larvae of the spionid polychaete Polydora ciliata (Johnston)

Almeda, Rodrigo; Pedersen, Troels Moller; Jakobsen, Hans Henrik; Alcaraz, Miquel; Calbet, Albert; Hansen, Benni Winding
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 5875 bytes; application/pdf
Português
Relevância na Pesquisa
55.99%
8 pages, 5 figures, 5 tables; We studied the effect of food concentration on the feeding and growth rates of different larval developmental stages of the spionid polychaete Polydora ciliata. We estimated larval feeding rates as a function of food abundance by incubation experiments with two different preys, presented separately, the cryptophyte Rhodomonas salina (ESD = 9.7 µm) and the diatom T. weissflogii (ESD = 12.9 µm). Additionally, we determined larval growth rates and gross growth efficiencies (GGE) as a function of R. salina concentration. P. ciliata larvae exhibited a type II functional response. Clearance rates decreased continuously with increasing food concentration, and ingestion rates increased up to a food saturation concentration above which ingestion remained fairly constant. The food concentration at which feeding became saturated varied depending on the food type, from ca. 2 µg C mL− 1 when feeding on T. weissflogii to ca. 5 µg C mL− 1 when feeding on R. salina. The maximum carbon specific ingestion rates were very similar for both prey types and decreased with increasing larval size/age, from 0.67 d− 1 for early larvae to 0.45 d− 1 for late stage larvae. Growth rates as a function of food concentration (R. salina) followed a saturation curve; the maximum specific growth rate decreased slightly during larval development from 0.22 to 0.17 d− 1. Maximum growth rates were reached at food concentrations ranging from 2.5 to 1.4 µg C mL− 1 depending on larval size. The GGE...

Modeling surface processes and kinetics of compound layer formation during plasma nitriding of pure iron

León Cázares,F.; Jiménez Ceniceros,A.; Oseguera Peña,J.; Castillo Aranguren,F.
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 Português
Relevância na Pesquisa
55.96%
Different approaches have been developed concerning growth description of the compact nitride layers, especially those produced by ammonia. Nitriding by plasma uses a glow discharge technology to introduce nitrogen to the surface which in turn diffuses itself into the material. During this process, the ion bombardment causes sputtering of the specimen surface. This paper presents a mathematical model of compound layer formation during plasma nitriding of pure iron. The model takes into account the erosion effect at the plasma-solid interface due to sputtering. This erosion effect is computer simulated and adjusted in order to consider its contribution to the study of layer growth kinetics. The model is presented as a moving boundary diffusion problem, which considers the observed qualitative behavior of the process.