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Search Results: 1 - 10 of 461868 matches for " Natanael A.; "
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Mesopic Visual Contrast Sensitivity in Patients with Major Depression  [PDF]
Renata M. T. B. L. Nogueira, Everton L. Espínola, Aline M. Lacerda, Natanael A. Santos
Open Journal of Depression (OJD) , 2013, DOI: 10.4236/ojd.2013.24014
Abstract: The present study evaluated the effects of major depression on visual contrast sensitivity (CS) at low mesopic luminance (.7 cd/m2 mean luminance), a condition that has been little explored in the literature. We measured spatial visual CS in 20 male volunteers aged 20 - 30 years, including 10 healthy individuals and 10 medicated individuals with major depression, to linear sine-wave gratings of .25, 1.0, and 4.0 cycles per degree (cpd) of visual angle using the psychophysical staircase method with forced choice. The average spatial visual CS in the depressed group was approximately 1.7 lower than the average spatial visual CS in the control group. However, the post hoc test showed significant differences only at the spatial frequencies of .25 and 1.0 cpd (p < .05), which are likely processed by the magnocellular visual pathway. These results suggest that spatial visual CS to sine-wave gratings should be used to evaluate the responsiveness of the visual system in patients with major depression under conditions of low luminance.
Early malnutrition decreases contrast sensitivity to circular concentric gratings
Alencar, Caroline C. G.;Santos, Natanael A. dos;
Psychology & Neuroscience , 2012, DOI: 10.3922/j.psns.2012.1.02
Abstract: early malnutrition refers to inadequate nutrition during the critical period of nervous system development followed by nutritional recovery, resulting in a short stature according to age but normal weight according to short stature. we measured the effects of early malnutrition on contrast sensitivity (cs) to concentric circular gratings in 18 children of both sexes, aged 8 to 11 years (mean = 9.2 years, standard deviation = .99 years). nine of the children were eutrophic (e group), and nine experienced early malnutrition (em group) based on state healthcare records and waterlow's anthropometric parameters. contrast sensitivity to four spatial frequencies (.25, 1.0, 2.0, and 8.0 cycles per degree [cpd]) was measured using a temporal two-alternative forced-choice psychophysical method with mean luminance of 40.1 cd/m2. statistical analyses showed significant differences between groups and a group × frequency interaction. em group was significantly less sensitive than the e group to the 8.0 cpd frequency and needed 1.49-times more contrast to detect the gratings. these results suggest that early malnutrition impairs cs to high-spatial-frequency concentric circular gratings in children. therefore, early malnutrition, which is known to affect primary visual cortical areas, may also affect higher visual cortical areas such as v4 and the inferotemporal cortex.
Early malnutrition decreases contrast sensitivity to circular concentric gratings
Caroline C. G. Alencar,Natanael A. dos Santos
Psychology & Neuroscience , 2012,
Abstract: Early malnutrition refers to inadequate nutrition during the critical period of nervous system development followed by nutritional recovery, resulting in a short stature according to age but normal weight according to short stature. We measured the effects of early malnutrition on contrast sensitivity (CS) to concentric circular gratings in 18 children of both sexes, aged 8 to 11 years (mean = 9.2 years, standard deviation = .99 years). Nine of the children were eutrophic (E group), and nine experienced early malnutrition (EM group) based on state healthcare records and Waterlow’s anthropometric parameters. Contrast sensitivity to four spatial frequencies (.25, 1.0, 2.0, and 8.0 cycles per degree [cpd]) was measured using a temporal two-alternative forced-choice psychophysical method with mean luminance of 40.1 cd/m2. Statistical analyses showed significant differences between groups and a group × frequency interaction. EM group was significantly less sensitive than the E group to the 8.0 cpd frequency and needed 1.49-times more contrast to detect the gratings. These results suggest that early malnutrition impairs CS to high-spatialfrequency concentric circular gratings in children. Therefore, early malnutrition, which is known to affect primary visual cortical areas, may also affect higher visual cortical areas such as V4 and the inferotemporal cortex.
New four-dimensional integrals by Mellin-Barnes transform
Pedro Allendes,Natanael Guerrero,Igor Kondrashuk,Eduardo A. Notte Cuello
Mathematics , 2009, DOI: 10.1063/1.3357105
Abstract: This paper is devoted to the calculation by Mellin-Barnes transform of a especial class of integrals. It contains double integrals in the position space in d = 4-2e dimensions, where e is parameter of dimensional regularization. These integrals contribute to the effective action of the N = 4 supersymmetric Yang-Mills theory. The integrand is a fraction in which the numerator is a logarithm of ratio of spacetime intervals, and the denominator is the product of powers of spacetime intervals. According to the method developed in the previous papers, in order to make use of the uniqueness technique for one of two integrations, we shift exponents in powers in the denominator of integrands by some multiples of e. As the next step, the second integration in the position space is done by Mellin-Barnes transform. For normalizing procedure, we reproduce first the known result obtained earlier by Gegenbauer polynomial technique. Then, we make another shift of exponents in powers in the denominator to create the logarithm in the numerator as the derivative with respect to the shift parameter delta. We show that the technique of work with the contour of the integral modified in this way by using Mellin-Barnes transform repeats the technique of work with the contour of the integral without such a modification. In particular, all the operations with a shift of contour of integration over complex variables of two-fold Mellin-Barnes transform are the same as before the delta modification of indices, and even the poles of residues coincide. This confirms the observation made in the previous papers that in the position space all the Green function of N = 4 supersymmetric Yang-Mills theory can be expressed in terms of UD functions.
Custos hospitalares com crian?as e adolescentes vítimas de traumatismos no Estado de Pernambuco em 1999
Mendon?a, Roberto Natanael da Silva;Alves, Jo?o Guilherme Bezerra;
Acta Ortopédica Brasileira , 2004, DOI: 10.1590/S1413-78522004000300002
Abstract: the brazilian national unified health system (sus) expenditures related to hospitalizations of trauma children and adolescents in the pernambuco state in 1999. were evaluated. data were collected from the databank of the hospital information system of the datasus, based on information recorded on the hospitalization authorization forms (aih). a total of 9,220 hospital admissions by external causes were identified with a cost of r$ 3,659,558.62, with 7,807 hospitalizations due to trauma (84.7%). the mean cost of hospital admissions for children and adolescents in the pernambuco state this year was r$ 306.49 versus a mean cost of hospital admissions for trauma of r$ 370.66. head trauma and limb fractures were associated with higher costs.
Sensibilidade ao contraste a grades senoidais de freqüências espaciais baixas em crian?as
Santos, Natanael Antonio dos;Fran?a, Valtenice de Cássia Rodrigues de Matos;
Estudos de Psicologia (Campinas) , 2008, DOI: 10.1590/S0103-166X2008000200002
Abstract: the aim of this study was to measure contrast sensitivity function for spatial frequencies of 0.25, 0.5, 1.0 and 2.0 cycles per degree in children between the ages of 4 and 13. we measured the contrast thresholds of 60 participants (50 children and 10 young adults) using the psychophysical forced-choice method and low luminance levels. all subjects were free from any identifiable ocular disease and had normal acuity. results showed that contrast sensitivity function, in children in the 4-5, 6-7, 8-9, 10-11 and 12-13 age ranges, improved significantly with age. the results also showed that, by 12-13 years of age, the contrast sensitivity function was similar to that of a young adult (19-22 years). these results suggest that the development of contrast sensitivity function for sine-wave grating at low luminance levels attains adult-like values by about 12-13 years of age.
Gastos hospitalares com crian?as e adolescentes vítimas de violência, no Estado de Pernambuco, Brasil, em 1999
Mendon?a, Roberto Natanael da Silva;Alves, Jo?o Guilherme Bezerra;Cabral Filho, José Eulálio;
Cadernos de Saúde Pública , 2002, DOI: 10.1590/S0102-311X2002000600011
Abstract: this study focused on expenditures under the brazilian national unified health system (sus) due to hospitalization of children and adolescents as the result of violence in pernambuco state in 1999. data were collected from the hospital admittance forms covering the state of pernambuco. some 9,220 hospital admissions due to external causes were identified, with a cost of r$3,659,558.62. mean cost of hospitalization for children and adolescents in pernambuco state in 1999 was r$306.49. mean cost of hospitalization due to external causes was r$396.91. traumatic lesions were the most common reason for hospital admission (84.7%). violence against children and adolescents in greater metropolitan recife accounted for 65.1% of hospital admissions and 77.9% of all hospital costs in pernambuco state.
A sensibilidade ao contraste em crian?as pré-escolares para padr?es distintos
Fran?a, Valtenice de Cássia Rodrigues de Matos;Santos, Natanael Antonio dos;
Paidéia (Ribeir?o Preto) , 2006, DOI: 10.1590/S0103-863X2006000200010
Abstract: in general the fsc is used to characterise the development of the visual perception of material by children. the aim of the present work was to mensure and compare contrast the sensitivity curves to differ then of the radical stimuly (fscr) and sine-wave gratings (fsc) in pré-school children, usind the psychophysical method of choice-forced for radial and sine-wave gratings stimuli of 0.25; 0.5; 1 and 2 cpd in 4-5 yearold preschool children and young adults using the psychophysical forced-choice staircase method. fifteen volunteers with corrected-to-normal visual acuity, five in each age range, participated in the experiments. the results showed that the sensitivity improves with the development and that in for all participants the sensitivity was higher for sine-wave gratings than the radial frequencies. these results suggest that the radial and the sine-wave gratings stimuli are processed by different visual areas.
Sensibilidade ao contraste em crian?as pré-escolares com método psicofísico
Fran?a, Valtenice de Cássia Rodrigues de Matos;Santos, Natanael Antonio dos;Mendes, Liana Chaves;
Psicologia: Teoria e Pesquisa , 2006, DOI: 10.1590/S0102-37722006000300010
Abstract: the aim of this work was to use the psychophysical forced-choice staircase method to measure contrast sensitivity function for spatial frequencies (csf) in the range between 0.25 and 4 cpd in preschool children and adults. we estimated the contrast thresholds of 15 participants (10 children and five adults). the results showed that the sensitivity curves (csf) of 4 and 5 years old chidren and adults were similar in general profiles although they were different between themselves. these results suggest that the psychophysical forced-choice staircase method can be used to measure the csf of children over 4 years old.
Sensibilidade ao contraste de freqüências radiais em crian?as de 4 a 7 anos e adultos
Santos, Natanael Antonio dos;Fran?a, Valtenice;Simas, Maria Lucia de Bustamante;
Psicologia: Reflex?o e Crítica , 2008, DOI: 10.1590/S0102-79722008000100004
Abstract: the aim of this work was to measure contrast sensitivity for radial frequencies (rcsf) in the range between 0.25-2 cpd in children (4 to 7 years of age) and young adults. contrast thresholds were estimated for 25 participants (twenty children and five adults) using the psychophysical forced-choice method at low luminance levels. all the cts participants had normal acuity. the results showed that the curves (rcsf) of the 4, 5, 6 and 7 years old improved significantly with age. the results also showed that the rcsf for 7 year old children was lower than in young adults. these results suggest that the development of contrast sensitivity for radial stimuli increases gradually even after turning 7 years old.
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