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1.
J Phys Condens Matter ; 36(38)2024 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-38866030

RESUMO

It is widely recognized that Pt nanostructures exhibit favorable catalytic properties for several important technological reactions. Furthermore, selecting an appropriate support has the potential to enhance the catalytic activity of these materials. In this study, we investigate Pt nanoparticles deposited on quantum dots using quantum chemical calculations. We explore the utilization of low-dimensional carbonaceous support by employing graphene quantum dots (GQDs), which offer abundant active sites, such as edges, and diverse conformations. This provides excellent tuning possibilities for both chemical and physical properties. Our goal is to gather information on the alterations in electronic properties, charge redistribution and reactivity of platinum particles on GQD, also analyzing their potential role as catalysts in the water dissociation reaction. Based on thermodynamic and kinetic considerations, our calculations suggest that a Pt3nanoparticle adsorbed on the edge of the GQD exhibits favorable energetics, leading to a promising catalytic material.

2.
Phys Chem Chem Phys ; 25(34): 23242-23248, 2023 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-37608728

RESUMO

Using DFT computational methods, single-walled carbon nanotubes (CNT) are explored in different geometric configurations (armchair, chiral and zigzag) doped with Fe. Geometry, electronic structure and magnetic properties are investigated for all systems, in order to evaluate a potential application of these structures as electrocatalysts in efficient and low-cost fuel cells. In search for a better electrode material, we turn our attention on nature for help. Oxygen molecules are well-known to reveal a remarkable affinity to the heme group. Therefore, we model the adsorption/dissociative behavior of oxygen molecules on carbon nanotubes doped with Fe atoms. We analyze in detail the effect of the chiral nature of carbon nanotubes that governs their electric, magnetic and chemical behavior. Our results indicate that the dissociation phenomenon involving the armchair (5,5) Fe@CNT is more favored than other chiralities and other doped CNT systems, leading to the lowest activation barrier.

3.
Phys Rev E ; 102(4-1): 042139, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33212705

RESUMO

Population survival depends on a large set of factors and on how they are distributed in space. Due to landscape heterogeneity, species can occupy particular regions that provide the ideal scenario for development, working as a refuge from harmful environmental conditions. Survival occurs if population growth overcomes the losses caused by adventurous individuals that cross the patch edge. In this work, we consider a single species dynamics in a patch with a space-dependent diffusion coefficient. We show analytically, within the Stratonovich framework, that heterogeneous diffusion reduces the minimal patch size for population survival when contrasted with the homogeneous case with the same average diffusivity. Furthermore, this result is robust regardless of the particular choice of the diffusion coefficient profile. We also discuss how this picture changes beyond the Stratonovich framework. Particularly, the Itô case, which is nonanticipative, can promote the opposite effect, while Hänggi-Klimontovich interpretation reinforces the reduction effect.

4.
Phys Rev E ; 99(6-1): 062225, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31330753

RESUMO

Internal feedback is commonly present in biological populations and can play a crucial role in the emergence of collective behavior. To describe the temporal evolution of the distribution of a single-species population, we consider a generalization of the Fisher-KPP equation. This equation includes the elementary processes of random motion, reproduction, and, importantly, nonlocal interspecific competition, which introduces a spatial scale of interaction. In addition, we take into account feedback mechanisms in diffusion and growth processes, mimicked by power-law density dependencies. This feedback includes, for instance, anomalous diffusion, reaction to overcrowding or to the rarefaction of the population, as well as Allee-like effects. We show that, depending on the kind of feedback that takes place, the population can self-organize splitting into disconnected subpopulations, in the absence of external constraints. Through extensive numerical simulations, we investigate the temporal evolution and the characteristics of the stationary population distribution in the one-dimensional case. We discuss the crucial role that density-dependence has on pattern formation, particularly on fragmentation, which can bring important consequences to processes such as epidemic spread and speciation.

5.
Animal ; 13(6): 1208-1213, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30355369

RESUMO

Excitable temperament disrupts physiological events required for reproductive development in cattle, but no research has investigated the impacts of temperament on growth and puberty attainment in Bos indicus females. Hence, this experiment evaluated the effects of temperament on growth, plasma cortisol concentrations and puberty attainment in B. indicus heifers. A total of 170 Nelore heifers, weaned 4 months before the beginning of this experiment (days 0 to 91), were managed in two groups of 82 and 88 heifers each (mean ± SE; initial BW=238±2 kg, initial age=369±1 days across groups). Heifer temperament was evaluated via exit velocity on day 0. Individual exit score was calculated within each group by dividing exit velocity into quintiles and assigning heifers with a score from 1 to 5 (1=slowest; 5=fastest heifer). Heifers were classified according to exit score as adequate (ADQ, n=96; exit score⩽3) or excitable temperament (EXC, n=74; exit score>3). Heifer BW, body condition score (BCS) and blood samples were obtained on days 0, 31, 60 and 91. Heifer exit velocity and score were recorded again on days 31, 60 and 91. Ovarian transrectal ultrasonography was performed on days 0 and 10, 31 and 41, 60 and 70, 81 and 91 for puberty evaluation. Heifer was declared pubertal at the first 10-day interval in which a corpus luteum was detected. Exit velocity and exit score obtained on day 0 were correlated (r⩾0.64, P<0.01) with evaluations on days 31, 60 and 91. During the experiment, ADQ had greater (P<0.01) mean BCS and BW gain, and less (P<0.01) mean plasma cortisol concentration compared with EXC heifers. Temperament × time interactions were detected (P<0.01) for exit velocity and exit score, which were always greater (P<0.01) in EXC v. ADQ heifers. A temperament × time interaction was also detected (P=0.03) for puberty attainment, which was delayed in EXC v. ADQ heifers. At the end of the experiment, a greater (P<0.01) proportion of ADQ were pubertal compared with EXC heifers. In summary, B. indicus heifers classified as EXC had reduced growth, increased plasma cortisol concentrations and hindered puberty attainment compared to ADQ heifers. Moreover, exit velocity may serve as temperament selection criteria to optimize development of B. indicus replacement heifers.


Assuntos
Bovinos/psicologia , Hidrocortisona/sangue , Temperamento , Animais , Brasil , Bovinos/sangue , Bovinos/crescimento & desenvolvimento , Feminino
6.
J Dairy Sci ; 101(1): 491-504, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29102132

RESUMO

This experiment compared insulin sensitivity, milk production, and reproductive outcomes in dairy cows consuming excessive energy during mid to late lactation and receiving in a 2 × 2 factorial design (1) concentrate based on ground corn (CRN; n = 20) or including 8% (DM basis) of Ca salts of palm oil (CSPO; n = 20), and (2) supplemented (n = 20) or not (n = 20) with 2.5 g/d of Cr-propionate. During the experiment (d 0-203), 40 multiparous, nonpregnant, lactating 3/4 Holstein × 1/4 Gir cows (initial days in milk = 81 ± 2; mean ± SE) were offered corn silage for ad libitum consumption, and individually received concentrate formulated to allow diets to provide 160% of their daily net energy for lactation requirements. From d -15 to 203, milk production was recorded daily, blood samples collected weekly, and cow body weight (BW) and body condition score (BCS) recorded on d 0 and 203. For dry matter intake evaluation, cows from both treatments were randomly divided in 5 groups of 8 cows each, and allocated to 8 individual feeding stations for 3 d. Intake was evaluated 6 times/group. Glucose tolerance tests (GTT; 0.5 g of glucose/kg of BW) were performed on d -3, 100, and 200. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up on d -1, 98, and 198. Mean DMI, net energy for lactation intake, as well as BW and BCS change were similar across treatments. On average, cows gained 40 kg of BW and 0.49 BCS during the experiment. Within weekly blood samples, CRN cows had lower serum concentrations of glucose, insulin, fatty acids, and insulin-to-glucose ratio compared with CSPO cows, suggesting increased insulin sensitivity in CRN cows. During the GTT, insulin-sensitivity traits were also greater in CRN versus CSPO cows. Supplemental Cr-propionate resulted in lower serum insulin concentrations and insulin-to-glucose ratio within CRN cows only, indicating that Cr-propionate improved basal insulin sensitivity in CRN but not in CSPO cows. During the GTT, however, Cr-propionate supplementation reduced hyperinsulinemia and insulin-to-glucose ratio across CSPO and CRN cows. Milk production, as well as number of viable oocytes collected and embryos produced within each aspiration, were not affected by treatments. Hence, replacing corn by Ca salts of palm oil in the concentrate did not improve insulin sensitivity in Holstein × Gir dairy cows consuming excessive energy during mid to late lactation, whereas Cr-supplementation was effective in improving basal insulin sensitivity in cows not receiving Ca salts of palm oil.


Assuntos
Cálcio/farmacologia , Cromo/farmacologia , Suplementos Nutricionais , Óleo de Palmeira/farmacologia , Propionatos/farmacologia , Reprodução/efeitos dos fármacos , Animais , Glicemia/efeitos dos fármacos , Peso Corporal , Bovinos , Dieta/veterinária , Ácidos Graxos/sangue , Feminino , Insulina/sangue , Resistência à Insulina , Lactação/efeitos dos fármacos , Distribuição Aleatória , Silagem , Zea mays
7.
J Dairy Sci ; 100(6): 4829-4838, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28434746

RESUMO

This study compared vaginal temperature, physiologic, and productive parameters in lactating dairy cows supplemented or not with Omnigen-AF (Phibro Animal Health, Teaneck, NJ) during the summer months in a tropical environment. Thirty-two lactating, primiparous (n = 16) and multiparous (n = 16) pregnant Holstein × Gir cows were ranked by parity, days in milk, body weight, and body condition score (BCS), and assigned to receive (SUPP; n = 16) or not (CON; n = 16) Omnigen-AF (Phibro Animal Health, Teaneck, NJ) at 56 g/cow daily (as-fed basis). During the experimental period (d -6 to 56), cows were maintained in a single drylot pen with ad libitum access to water and a total mixed ration, and milked twice daily. Cows received Omnigen-AF mixed with 200 g of corn (as-fed basis) after the daily morning milking through self-locking head gates, whereas CON cows concurrently received 56 g of kaolin mixed with 200 g of corn. For feed intake evaluation, cows from both treatments were randomly divided in 4 groups of 8 cows each, and allocated to 8 individual feeding stations for 3 d. Intake was evaluated 4 times per group from d 1 to 56. From d -6 to 0, d 15 to 28, and d 43 to 56, cow vaginal temperature was recorded hourly. Environmental temperature-humidity index (THI) was also recorded hourly from d 15 to 28 and d 43 to 56. Cows were evaluated for body weight and BCS on d -6 and 56, individual milk production was recorded daily from d -6 to 56, and milk samples were collected on d -6, 0, 7, 14, 21, 28, 35, 42, 49, and 56 for analyses of somatic cell count and milk components. Blood samples were collected on d -6, -3, 0, 9, 15, 18, 21, 24, 27, 36, 45, 48, 51, 54, and 56. Results from samples or observations collected from d -6 to 0 were included as an independent covariate in each respective analysis. Environmental THI was 74.2 ± 0.5 and cows were exposed to THI >68 for 633 h within a total of 672 h of evaluation. Cows assigned to CON had greater vaginal temperature on d 28, 43, 45, and from d 48 to 55 (by 0.38 to 0.52%), as well as greater mean somatic cell count (by 97%) and serum haptoglobin concentrations (by 89%) compared with SUPP cows. Cows assigned to SUPP had greater mean dry matter intake (by 7%), BCS on d 56 (by 11%), and mean serum insulin concentrations (by 35%) compared with CON cows. Hence, SUPP ameliorated hyperthermia, improved nutritional status, and modulated systemic and mammary gland immune parameters in lactating dairy cows exposed to heat stress conditions.


Assuntos
Ração Animal , Regulação da Temperatura Corporal/fisiologia , Doenças dos Bovinos/fisiopatologia , Transtornos de Estresse por Calor/veterinária , Imunomodulação , Lactação/fisiologia , Animais , Peso Corporal , Bovinos , Doenças dos Bovinos/sangue , Doenças dos Bovinos/imunologia , Dieta , Suplementos Nutricionais , Feminino , Transtornos de Estresse por Calor/sangue , Transtornos de Estresse por Calor/imunologia , Transtornos de Estresse por Calor/fisiopatologia , Temperatura Alta/efeitos adversos , Umidade , Lactação/imunologia , Leite/metabolismo , Paridade , Gravidez , Vagina/fisiopatologia
8.
Braz. j. biol ; Braz. j. biol;77(1): 1-11, Jan-Mar. 2017. tab, graf
Artigo em Inglês | LILACS | ID: biblio-839175

RESUMO

Abstract Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.


Resumo Variação de cor intra-específica é muitas vezes subestimada pelos pesquisadores, e entre espécies de mamíferos, as diferenças intra-específicas na coloração são pouco conhecidas para a maioria das espécies. O principal objetivo deste estudo foi aplicar uma metodologia objetiva de medição de cor para o estudo de um problema específico: a detecção de padrões de mudanças na cor da pele de espécimes de Akodon budini em relação a variáveis biológicas (i.e., sexo) e ambientais (i.e., temporada), se houver. Nossa hipótese é que a cor da pelagem do sexo masculino será mais homogênea do que a de fêmeas e que a cor da pelagem do inverno vai ser mais escura do que a de verão, sendo esta última mais laranja. Medimos a cor da pelagem em cinco pontos sobre a superfície dorsal de 26 espécimes de museu de A. budini usando um espectroradiômetro e uma cabine de iluminação difusa. Usamos Análise de Componentes Principais para descrever a associação entre as variáveis de cor, sexo e temporada, e cada uma das observações. Em seguida, usamos modelos lineares gerais da Análise de Variância para verificar as relações entre os dados de cor, temporada, e sexo. Os resultados confirmam claramente a hipótese relacionada à mudança sazonal de cor da pelagem, mas não confirmam diretamente a hipótese relacionada com alterações na cor da pelagem em relação ao sexo, e vamos mostrar a complexidade do modelo estudado. Em conclusão, sem dúvida, as variáveis estudadas devem consequentemente ser tidas em conta quando se estuda a coloração de amostras para caracterização, identificação e discriminação de diferentes unidades taxonômicas com base na cor.


Assuntos
Animais , Masculino , Feminino , Cor de Cabelo/fisiologia , Arvicolinae/fisiologia , Estações do Ano , Caracteres Sexuais , Meio Ambiente , Mamíferos
9.
Braz. j. biol ; Braz. j. biol;77(1): 01-11, Jan-Mar. 2017. map, ilus, tab, graf
Artigo em Inglês | LILACS, VETINDEX | ID: biblio-1468374

RESUMO

Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.


Variação de cor intra-específica é muitas vezes subestimada pelos pesquisadores, e entre espécies de mamíferos, as diferenças intra-específicas na coloração são pouco conhecidas para a maioria das espécies. O principal objetivo deste estudo foi aplicar uma metodologia objetiva de medição de cor para o estudo de um problema específico: a detecção de padrões de mudanças na cor da pele de espécimes de Akodon budini em relação a variáveis biológicas (i.e., sexo) e ambientais (i.e., temporada), se houver. Nossa hipótese é que a cor da pelagem do sexo masculino será mais homogênea do que a de fêmeas e que a cor da pelagem do inverno vai ser mais escura do que a de verão, sendo esta última mais laranja. Medimos a cor da pelagem em cinco pontos sobre a superfície dorsal de 26 espécimes de museu de A. budini usando um espectroradiômetro e uma cabine de iluminação difusa. Usamos Análise de Componentes Principais para descrever a associação entre as variáveis de cor, sexo e temporada, e cada uma das observações. Em seguida, usamos modelos lineares gerais da Análise de Variância para verificar as relações entre os dados de cor, temporada, e sexo. Os resultados confirmam claramente a hipótese relacionada à mudança sazonal de cor da pelagem, mas não confirmam diretamente a hipótese relacionada com alterações na cor da pelagem em relação ao sexo, e vamos mostrar a complexidade do modelo estudado. Em conclusão, sem dúvida, as variáveis estudadas devem consequentemente ser tidas em conta quando se estuda a coloração de amostras para caracterização, identificação e discriminação de diferentes unidades taxonômicas com base na cor.


Assuntos
Animais , Equipamentos de Medição de Riscos , Pigmentação da Pele , Sigmodontinae/anatomia & histologia , Variação Genética , Análise Espectral/métodos
10.
Braz. J. Biol. ; 77(1): 01-11, jan.-mar. 2017. mapas, ilus, tab, graf
Artigo em Inglês | VETINDEX | ID: vti-734898

RESUMO

Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.(AU)


Variação de cor intra-específica é muitas vezes subestimada pelos pesquisadores, e entre espécies de mamíferos, as diferenças intra-específicas na coloração são pouco conhecidas para a maioria das espécies. O principal objetivo deste estudo foi aplicar uma metodologia objetiva de medição de cor para o estudo de um problema específico: a detecção de padrões de mudanças na cor da pele de espécimes de Akodon budini em relação a variáveis biológicas (i.e., sexo) e ambientais (i.e., temporada), se houver. Nossa hipótese é que a cor da pelagem do sexo masculino será mais homogênea do que a de fêmeas e que a cor da pelagem do inverno vai ser mais escura do que a de verão, sendo esta última mais laranja. Medimos a cor da pelagem em cinco pontos sobre a superfície dorsal de 26 espécimes de museu de A. budini usando um espectroradiômetro e uma cabine de iluminação difusa. Usamos Análise de Componentes Principais para descrever a associação entre as variáveis de cor, sexo e temporada, e cada uma das observações. Em seguida, usamos modelos lineares gerais da Análise de Variância para verificar as relações entre os dados de cor, temporada, e sexo. Os resultados confirmam claramente a hipótese relacionada à mudança sazonal de cor da pelagem, mas não confirmam diretamente a hipótese relacionada com alterações na cor da pelagem em relação ao sexo, e vamos mostrar a complexidade do modelo estudado. Em conclusão, sem dúvida, as variáveis estudadas devem consequentemente ser tidas em conta quando se estuda a coloração de amostras para caracterização, identificação e discriminação de diferentes unidades taxonômicas com base na cor.(AU)


Assuntos
Animais , Sigmodontinae/anatomia & histologia , Equipamentos de Medição de Riscos , Variação Genética , Pigmentação da Pele , Análise Espectral/métodos
11.
Braz J Biol ; 77(1): 1-11, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27382999

RESUMO

Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.


Assuntos
Arvicolinae/fisiologia , Cor de Cabelo/fisiologia , Animais , Meio Ambiente , Feminino , Masculino , Mamíferos , Estações do Ano , Caracteres Sexuais
12.
Phys Rev E ; 94(4-1): 042413, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27841580

RESUMO

Population dynamics is constrained by the environment, which needs to obey certain conditions to support population growth. We consider a standard model for the evolution of a single species population density, which includes reproduction, competition for resources, and spatial spreading, while subject to an external harmful effect. The habitat is spatially heterogeneous, there existing a refuge where the population can be protected. Temporal variability is introduced by the intermittent character of the refuge. This scenario can apply to a wide range of situations, from a laboratory setting where bacteria can be protected by a blinking mask from ultraviolet radiation, to large-scale ecosystems, like a marine reserve where there can be seasonal fishing prohibitions. Using analytical and numerical tools, we investigate the asymptotic behavior of the total population as a function of the size and characteristic time scales of the refuge. We obtain expressions for the minimal size required for population survival, in the slow and fast time scale limits.


Assuntos
Ecossistema , Modelos Biológicos , Animais , Conservação dos Recursos Naturais , Dinâmica Populacional , Fatores de Tempo
13.
Artigo em Inglês | MEDLINE | ID: mdl-26382439

RESUMO

We propose a general model to study the interplay between spatial dispersal and environment spatiotemporal fluctuations in metapopulation dynamics. An ecological landscape of favorable patches is generated like a Lévy dust, which allows to build a range of patterns, from dispersed to clustered ones. Locally, the dynamics is driven by a canonical model for the time evolution of the population density, consisting of a logistic expression plus multiplicative noises. Spatial coupling is introduced by means of two spreading mechanisms: diffusion and selective dispersal driven by patch suitability. We focus on the long-time population size as a function of habitat configurations, environment fluctuations, and coupling schemes. We obtain the conditions, that the spatial distribution of favorable patches and the coupling mechanisms must fulfill, to grant population survival. The fundamental phenomenon that we observe is the positive feedback between environment fluctuations and spatial spread preventing extinction.


Assuntos
Meio Ambiente , Modelos Biológicos , Dinâmica Populacional , Retroalimentação , Processos Estocásticos , Fatores de Tempo
14.
Artigo em Inglês | MEDLINE | ID: mdl-25122348

RESUMO

System-environment interactions are intrinsically nonlinear and dependent on the interplay between many degrees of freedom. The complexity may be even more pronounced when one aims to describe biologically motivated systems. In that case, it is useful to resort to simplified models relying on effective stochastic equations. A natural consideration is to assume that there is a noisy contribution from the environment, such that the parameters that characterize it are not constant but instead fluctuate around their characteristic values. From this perspective, we propose a stochastic generalization of the nonlocal Fisher-KPP equation where, as a first step, environmental fluctuations are Gaussian white noises, both in space and time. We apply analytical and numerical techniques to study how noise affects stability and pattern formation in this context. Particularly, we investigate noise-induced coherence by means of the complementary information provided by the dispersion relation and the structure function.


Assuntos
Meio Ambiente , Modelos Teóricos , Dinâmica não Linear , Dinâmica Populacional , Processos Estocásticos
15.
Vision Res ; 41(9): 1139-44, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11292504

RESUMO

To examine how the time course of rapid events of adaptation affect motion vision, the lower threshold of motion (LTM) was measured for suprathreshold sinusoidal gratings in presence of transient and steady glare. In the case of the transient condition, glare and stimulus were presented separated in time by a variable extent (SOA: 50-450 ms). A two alternative forced choice paradigm using the method of constant stimuli was adopted to measure the LTM. It was found that LTM follows the characteristic Crawford's time course of adaptation. Results are similar for two stimulus duration (300 and 500 ms). It was proposed that the increment of contrast threshold for displacing gratings (C(tq)) due to the loss of sensitivity produced by the sudden onset of the glare source can explain the results.


Assuntos
Adaptação Ocular/fisiologia , Percepção de Movimento/fisiologia , Limiar Sensorial/fisiologia , Ofuscação , Humanos , Psicometria , Fatores de Tempo
16.
Buenos Aires; Comité de Estudios Fetonatales; 1990. [13] p. (79426).
Monografia em Espanhol | BINACIS | ID: bin-79426
17.
Buenos Aires; Comité de Estudios Fetonatales; 1990. [13] p.
Monografia em Espanhol | BINACIS | ID: biblio-1202576
18.
Acta Psiquiatr Psicol Am Lat ; 26(2): 131-8, 1980 Jun.
Artigo em Espanhol | MEDLINE | ID: mdl-7348052

RESUMO

The psychodermogalvanogram is a modern electrographical procedure whose main function depends upon a Wheatstone Bridge set at a constant voltage and with variations of intensity set up in direct relation to the conductivity of the skin. The spontaneous psychodermogalvanogram (SPDG) makes it possible to evaluate patients that could be either of a: a) normal reaction; b) hyporeactional; c) hyperreactional; d) disreactional or unstable. The psycholinguistic psychogalvanogram (PLPG) enables the possibility of distinguishing the different forms of behaviour: A) Normal reactions (+/- 80% of our clinical reports). The comportance of youths not hypnotizable or hypnocomplacent pacients, geriatrics, psychopatic personalities, electroepylepsies (GME), juvenile diabetics, etc. The PLPG presents the typical reactions in the positive answers (a marked increase in the biophasic or monophasic waves lengths) or the negative (a reduction in the volume of both waves lengths). The Time Reaction of Psycholinguistic factor (TRPL) varies from 70 to 110 ms. The comprehension of guestaltic questions arising and a repetition of the same shorten the TRPL. Rapid reaction of physic stress. Common to EEF there is an increased activity in the beta rythm prefontal left of the band 16 to 27 c/s and the paroxisms alpha prior to the right temporal of band 8 c/s and a duration of 3 to 5 seconds, equivalent answers to the PLPG. The cardiorespiratory rythm increase in relation to psychic stress. The Rheoencephalogram (REG) revealed an increase in the flown pulse of anterior cerebral artery of left hemisphere and the middle cerebral artery of right hemisphere. B) Abnormal reactions (+/- 11% of our clinical reports), which includes deep oligophrenics, schizophrenics, delirants and electroepilepsias (PME). The PLPG shows a dominance in the monophasic waves lengths at low variation similar to those found in arteriosclerosis. Paradoxically, the REG shows a marked reduction of the right carotic cerebral artery (genetic modification?). On the other hand the PLPG shows practically no reactional changes. C) Hyper reactives or sofronizables (+/- 9% of our clinical reports) includes those who can be hypnotized or are supersensitive. The PLPG reveals biondic cycles which are grouped in convexed arcs on the rise, reaching levels of 4 to 6 positive reaction, or in concave arcs on the decline reaching negative reactions. The TRPL is very brief, from 30 to 55 ms. The EEG shows in the left hemisphere, on the beta rithm basalis, alpha paroxysm of 8 c/s and 1 to 2 seconds duration wich are recorded in the prefrontal area. The right hemispheric recording, registers paroxysms of a large quantity in the theta rythm with a frequency of 5 to 6 cycles per second and a duration of 5 to 6 seconds which interrupted the beta band in a frequency of 14 to 17 c/s, similar to those registered during the drowsiness. The EOG shows very slow wyw movement. The ECG reduced its frequency and the electrospirogram (ESG) increased its volume. The pupils are parcial miotics...


Assuntos
Comportamento/fisiologia , Resposta Galvânica da Pele/fisiologia , Transtornos Mentais/fisiopatologia , Eletrofisiologia/instrumentação , Humanos , Tempo de Reação/fisiologia , Comportamento Verbal/fisiologia
19.
Acta psiquiátr. psicol. Am. Lat ; 26(2): 131-8, 1980 Jun.
Artigo em Espanhol | LILACS-Express | BINACIS | ID: biblio-1158947

RESUMO

The psychodermogalvanogram is a modern electrographical procedure whose main function depends upon a Wheatstone Bridge set at a constant voltage and with variations of intensity set up in direct relation to the conductivity of the skin. The spontaneous psychodermogalvanogram (SPDG) makes it possible to evaluate patients that could be either of a: a) normal reaction; b) hyporeactional; c) hyperreactional; d) disreactional or unstable. The psycholinguistic psychogalvanogram (PLPG) enables the possibility of distinguishing the different forms of behaviour: A) Normal reactions (+/- 80


of our clinical reports). The comportance of youths not hypnotizable or hypnocomplacent pacients, geriatrics, psychopatic personalities, electroepylepsies (GME), juvenile diabetics, etc. The PLPG presents the typical reactions in the positive answers (a marked increase in the biophasic or monophasic waves lengths) or the negative (a reduction in the volume of both waves lengths). The Time Reaction of Psycholinguistic factor (TRPL) varies from 70 to 110 ms. The comprehension of guestaltic questions arising and a repetition of the same shorten the TRPL. Rapid reaction of physic stress. Common to EEF there is an increased activity in the beta rythm prefontal left of the band 16 to 27 c/s and the paroxisms alpha prior to the right temporal of band 8 c/s and a duration of 3 to 5 seconds, equivalent answers to the PLPG. The cardiorespiratory rythm increase in relation to psychic stress. The Rheoencephalogram (REG) revealed an increase in the flown pulse of anterior cerebral artery of left hemisphere and the middle cerebral artery of right hemisphere. B) Abnormal reactions (+/- 11


of our clinical reports), which includes deep oligophrenics, schizophrenics, delirants and electroepilepsias (PME). The PLPG shows a dominance in the monophasic waves lengths at low variation similar to those found in arteriosclerosis. Paradoxically, the REG shows a marked reduction of the right carotic cerebral artery (genetic modification?). On the other hand the PLPG shows practically no reactional changes. C) Hyper reactives or sofronizables (+/- 9


of our clinical reports) includes those who can be hypnotized or are supersensitive. The PLPG reveals biondic cycles which are grouped in convexed arcs on the rise, reaching levels of 4 to 6 positive reaction, or in concave arcs on the decline reaching negative reactions. The TRPL is very brief, from 30 to 55 ms. The EEG shows in the left hemisphere, on the beta rithm basalis, alpha paroxysm of 8 c/s and 1 to 2 seconds duration wich are recorded in the prefrontal area. The right hemispheric recording, registers paroxysms of a large quantity in the theta rythm with a frequency of 5 to 6 cycles per second and a duration of 5 to 6 seconds which interrupted the beta band in a frequency of 14 to 17 c/s, similar to those registered during the drowsiness. The EOG shows very slow wyw movement. The ECG reduced its frequency and the electrospirogram (ESG) increased its volume. The pupils are parcial miotics...

20.
Acta Psiquiatr. Psicol. Am. Lat ; 26(2): 131-8, 1980 Jun.
Artigo em Espanhol | BINACIS | ID: bin-50689

RESUMO

The psychodermogalvanogram is a modern electrographical procedure whose main function depends upon a Wheatstone Bridge set at a constant voltage and with variations of intensity set up in direct relation to the conductivity of the skin. The spontaneous psychodermogalvanogram (SPDG) makes it possible to evaluate patients that could be either of a: a) normal reaction; b) hyporeactional; c) hyperreactional; d) disreactional or unstable. The psycholinguistic psychogalvanogram (PLPG) enables the possibility of distinguishing the different forms of behaviour: A) Normal reactions (+/- 80


of our clinical reports). The comportance of youths not hypnotizable or hypnocomplacent pacients, geriatrics, psychopatic personalities, electroepylepsies (GME), juvenile diabetics, etc. The PLPG presents the typical reactions in the positive answers (a marked increase in the biophasic or monophasic waves lengths) or the negative (a reduction in the volume of both waves lengths). The Time Reaction of Psycholinguistic factor (TRPL) varies from 70 to 110 ms. The comprehension of guestaltic questions arising and a repetition of the same shorten the TRPL. Rapid reaction of physic stress. Common to EEF there is an increased activity in the beta rythm prefontal left of the band 16 to 27 c/s and the paroxisms alpha prior to the right temporal of band 8 c/s and a duration of 3 to 5 seconds, equivalent answers to the PLPG. The cardiorespiratory rythm increase in relation to psychic stress. The Rheoencephalogram (REG) revealed an increase in the flown pulse of anterior cerebral artery of left hemisphere and the middle cerebral artery of right hemisphere. B) Abnormal reactions (+/- 11


of our clinical reports), which includes deep oligophrenics, schizophrenics, delirants and electroepilepsias (PME). The PLPG shows a dominance in the monophasic waves lengths at low variation similar to those found in arteriosclerosis. Paradoxically, the REG shows a marked reduction of the right carotic cerebral artery (genetic modification?). On the other hand the PLPG shows practically no reactional changes. C) Hyper reactives or sofronizables (+/- 9


of our clinical reports) includes those who can be hypnotized or are supersensitive. The PLPG reveals biondic cycles which are grouped in convexed arcs on the rise, reaching levels of 4 to 6 positive reaction, or in concave arcs on the decline reaching negative reactions. The TRPL is very brief, from 30 to 55 ms. The EEG shows in the left hemisphere, on the beta rithm basalis, alpha paroxysm of 8 c/s and 1 to 2 seconds duration wich are recorded in the prefrontal area. The right hemispheric recording, registers paroxysms of a large quantity in the theta rythm with a frequency of 5 to 6 cycles per second and a duration of 5 to 6 seconds which interrupted the beta band in a frequency of 14 to 17 c/s, similar to those registered during the drowsiness. The EOG shows very slow wyw movement. The ECG reduced its frequency and the electrospirogram (ESG) increased its volume. The pupils are parcial miotics...

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