ABSTRACT
The Kardar-Parisi-Zhang (KPZ) equation describes a wide range of growth-like phenomena, with applications in physics, chemistry and biology. There are three central questions in the study of KPZ growth: the determination of height probability distributions; the search for ever more precise universal growth exponents; and the apparent absence of a fluctuation-dissipation theorem (FDT) for spatial dimension d>1. Notably, these questions were answered exactly only for 1+1 dimensions. In this work, we propose a new FDT valid for the KPZ problem in d+1 dimensions. This is achieved by rearranging terms and identifying a new correlated noise which we argue to be characterized by a fractal dimension dn. We present relations between the KPZ exponents and two emergent fractal dimensions, namely df, of the rough interface, and dn. Also, we simulate KPZ growth to obtain values for transient versions of the roughness exponent α, the surface fractal dimension df and, through our relations, the noise fractal dimension dn. Our results indicate that KPZ may have at least two fractal dimensions and that, within this proposal, an FDT is restored. Finally, we provide new insights into the old question about the upper critical dimension of the KPZ universality class.
ABSTRACT
Molecular dynamics simulations have been used in different scientific fields to investigate a broad range of physical systems. However, the accuracy of calculation is based on the model considered to describe the atomic interactions. In particular, ab initio molecular dynamics (AIMD) has the accuracy of density functional theory (DFT) and thus is limited to small systems and a relatively short simulation time. In this scenario, Neural Network Force Fields (NNFFs) have an important role, since they provide a way to circumvent these caveats. In this work, we investigate NNFFs designed at the level of DFT to describe liquid water, focusing on the size and quality of the training data set considered. We show that structural properties are less dependent on the size of the training data set compared to dynamical ones (such as the diffusion coefficient), and a good sampling (selecting data reference for the training process) can lead to a small sample with good precision.
ABSTRACT
ABSTRACT Purpose: To compare the quality of retinal images captured with a smartphone-based, handheld fundus camera with that of retinal images captured with a commercial fundus camera and to analyze their agreement in determining the cup-to-disc ratio for a cohort of ophthalmological patients. Methods: A total of 50 patients from a secondary ophthalmic outpatient service center underwent a bilateral fundus examination under mydriasis with a smartphone-based, handheld fundus camera and with a commercial fundus camera (4 images/patient by each). Two experienced ophthalmologists evaluated all the fundus images and graded them on the Likert 1-5 scale for quality. Multivariate regression analyses was then performed to evaluate the factors associated with the image quality. Two masked ophthalmologists determined the vertical cup-to-disc ratio of each fundus image, and both the intraobserver (between devices) and interobserver agreement between them was calculated. Results: Ninety-eight images from 49 patients were processed in this study for their quality analysis. Ten images from five patients (four from commercial fundus camera and one from smartphone-based, handheld fundus camera) were not included in the analyses due to their extremely poor quality. The medians [interquartile interval] of the image quality were not significantly different between those from the smartphone-based, handheld fundus camera and from the commercial fundus camera (4 [4-5] versus 4 [3-4] respectively, p=0.06); however, both the images captured with the commercial fundus camera and the presence of media opacity presented a significant negative correlation with the image quality. Both the intraobserver [intraclass correlation coefficient (ICC)=0.82, p<0.001 and 0.83, p<0.001, for examiners 1 and 2, respectively] and interobserver (ICC=0.70, p=0.001 and 0.81; p<0.001, for smartphone-based handheld fundus camera and commercial fundus camera, respectively) agreements were excellent and statistically significant. Conclusions: Our results thus indicate that the smartphone-based, handheld fundus camera yields an image quality similar to that from a commercial fundus camera, with significant agreement in the cup-to-disc ratios between them. In addition to the good outcomes recorded, the smartphone-based, handheld fundus camera offers the advantages of portability and low-cost to serve as an alternative for fundus documentation for future telemedicine approaches in medical interventions.
RESUMO Objetivo: Comparar a qualidade das imagens da retina capturadas com um retinógrafo portátil acoplado a um smartphone com aquelas adquiridas com um retinógrafo comercial padrão e analisar a concordância na determinação da relação escavação/ cabeça do nervo óptico em um coorte de pacientes de um serviço oftalmológico. Métodos: Cinquenta pacientes de um serviço oftalmológico secundário foram submetidos a uma avaliação do fundo de olho bilateral, sob midríase, utilizando o retinógrafo portátil acoplado a um smartphone e o retinógrafo comercial padrão (4 imagens por paciente). Dois oftalmologistas experientes avaliaram a qualidade de todas as imagens e atribuíram a elas uma pontuação entre 1 e 5, de acordo com a escala Likert. Os fatores relacionados a qualidade das imagens foram avaliados utilizando uma análise de regressão multivariada. Dois oftalmologistas determinaram de forma mascarada a relação da escavação/ cabeça do nervo óptico de cada imagem e a concordância intra e interobservador foi calculada. Resultados: Noventa e oito imagens de 49 pacientes foram utilizadas neste estudo para análise de qualidade. Dez imagens de cinco pacientes (quatro do retinógrafo comercial padrão e um do retinógrafo portátil acoplado a um smartphone) foram excluídas das análises de concordância devido à baixa qualidade das mesmas, mas foram considerados nas análises de qualidade. Dos cinco pacientes com imagens excluídas, quatro foram capturadas pelo retinógrafo comercial padrão e uma pelo retinógrafo portátil acoplado a um smartphone. As medianas (intervalo interquartil) da qualidade das imagens não apresentaram diferença estatística entre o retinógrafo portátil acoplado a um smartphone e o retinógrafo comercial padrão (4 [4-5] versus 4 [3-4] respectivamente, p=0.06). As imagens obtidas com o retinógrafo comercial padrão e o diagnóstico de opacidade de meios apresentou uma correlação negativa com a qualidade da imagem. As concordâncias intraobservador (ICC=0,82, p<0,001 e 0,83, p<0,001, para o examinador 1 e 2, respectivamente) e interobservador (ICC = 0,70, p=0,001 e 0,81, p<0.001, para o retinógrafo portátil acoplado a um smartphone e retinógrafo comercial padrão, respectivamente) foram excelentes e estatisticamente significativas. Conclusões: Nossos resultados sugerem que o retinógrafo portátil acoplado a um smartphone apresenta uma qualidade de imagem semelhante ao retinógrafo comercial padrão, com concordância significativa na análise da relação escavação-cabeça do nervo óptico. Além dos bons resultados apresentados, o retinógrafo portátil acoplado a um smartphone pode ser considerado uma alternativa portátil de baixo custo para documentação de retina em cenários futuros de telemedicina.
ABSTRACT
PURPOSE: To compare the quality of retinal images captured with a smartphone-based, handheld fundus camera with that of retinal images captured with a commercial fundus camera and to analyze their agreement in determining the cup-to-disc ratio for a cohort of ophthalmological patients. METHODS: A total of 50 patients from a secondary ophthalmic outpatient service center underwent a bilateral fundus examination under mydriasis with a smartphone-based, handheld fundus camera and with a commercial fundus camera (4 images/patient by each). Two experienced ophthalmologists evaluated all the fundus images and graded them on the Likert 1-5 scale for quality. Multivariate regression analyses was then performed to evaluate the factors associated with the image quality. Two masked ophthalmologists determined the vertical cup-to-disc ratio of each fundus image, and both the intraobserver (between devices) and interobserver agreement between them was calculated. RESULTS: Ninety-eight images from 49 patients were processed in this study for their quality analysis. Ten images from five patients (four from commercial fundus camera and one from smartphone-based, handheld fundus camera) were not included in the analyses due to their extremely poor quality. The medians [interquartile interval] of the image quality were not significantly different between those from the smartphone-based, handheld fundus camera and from the commercial fundus camera (4 [4-5] versus 4 [3-4] respectively, p=0.06); however, both the images captured with the commercial fundus camera and the presence of media opacity presented a significant negative correlation with the image quality. Both the intraobserver [intraclass correlation coefficient (ICC)=0.82, p<0.001 and 0.83, p<0.001, for examiners 1 and 2, respectively] and interobserver (ICC=0.70, p=0.001 and 0.81; p<0.001, for smartphone-based handheld fundus camera and commercial fundus camera, respectively) agreements were excellent and statistically significant. CONCLUSIONS: Our results thus indicate that the smartphone-based, handheld fundus camera yields an image quality similar to that from a commercial fundus camera, with significant agreement in the cup-to-disc ratios between them. In addition to the good outcomes recorded, the smartphone-based, handheld fundus camera offers the advantages of portability and low-cost to serve as an alternative for fundus documentation for future telemedicine approaches in medical interventions.
