Soluciones metaestables para un modelo de campos de fase con más de dos fases

Consideramos una generalización del modelo de campos de fase semilineal [11] A. Jiménez-Casas, A. Rodriguez-Bernal, “Linear stabilility analysis and metastable solutions for a phase-field model,” Proceeding of the Royal Society of Edimburgh, 129A, 571-600, (1999), usando una función de densidad más general. Esa función de densidad describe la separación de mezclas con tres o más componentes, en lugar de las mezclas binarias de los modelos anteriores. Probamos la existencia de soluciones metaestables, es decir que evolucionan muy lentamente en el tiempo

Nonlinear theory of ion-induced solid flow

[Abstract of]: 25th Conference on Applications of Accelerators in Research and Industry (CAARI 2018), Grapevine, Texas, USA, August 12-17, 2018.Ion beam sputtering (IBS) is a powerful technique employed to induce surface nanopatterns over relatively large areas for a wide range of materials [1]. This approach has many applications in modern technology like magnetic storage, quantum device design or, for example, producing the selective attachment of specific molecules to substrates, with implications in biology and catalysis

Symmetry of surface nanopatterns induced by ion-beam sputtering: Role of anisotropic surface diffusion

Ion-beam sputtering (IBS) is a cost-effective technique able to produce ordered nanopatterns on the surfaces of different materials. To date, most theoretical studies of this process have focused on systems which become amorphous under irradiation, e.g., semiconductors at room temperature. Thus, in spite of the large amount of experimental work on metals, or more recently on semiconductors at high temperatures, such experimental contexts have received relatively little theoretical attention. These systems are characterized by transport mechanisms, e.g., surface diffusion, which are anisotropic as a reflection of the crystalline structure not being overruled by the irradiation. Here, we generalize a previous continuum theory of IBS at normal incidence, in order to account for anisotropic surface diffusion. We explore systematically our generalized model in order to understand the role of anisotropy in the space-ordering properties of the resulting patterns.We acknowledge discussions with J.-S. Kim and J.-H. Kim. This work has been funded through MINECO (Spain) Grants No. FIS2012-38866-C05-01, No. FIS2012-32349, No. FIS2013-47949-C2-2, and No. FIS2015-66020-C2-1-P

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

Porous nano and micro crystalline tin oxide films were deposited by RF Magnetron Sputtering and doctor blade techniques, respectively. Electrical resistance and impedance spectroscopy measurements, as a function of temperature and atmosphere, were performed in order to determine the influence of the microstructure and working conditions over the electrical response of the sensors. The conductivity of all samples increases with the temperature and decreases in oxygen, as expected for an n-type semiconducting material. The impedance plots indicated the existence of two time constants related to the grains and the grain boundaries. The Nyquist diagrams at low frequencies revealed the changes that took place in the grain boundary region, with the contribution of the grains being indicated by the formation of a second semicircle at high frequencies. The better sensing performance of the doctor bladed samples can be explained by their lower initial resistance values, bigger grain sizes and higher porosity.Fil: Savu, Raluca. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Ponce, Miguel Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Joanni, Ednan. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Bueno, Paulo Roberto. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Castro, Miriam Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Cilense, Mario. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Varela, Jose Arana. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Longo, Elson. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi

Special issue on surfaces patterned by ion sputtering

We thank all the authors within this issue for their efforts and contributions, and the editorial staff of Journal of Physics: Condensed Matter for their efficient work. We also acknowledge funding by the MINECO/FEDER (Spain/ UE) grant Nos. MAT2017-85089-C2-1-R, MAT2016-80394-R, FIS2015-66020-C2-1-P, FIS2015-73337-JIN, FIS2016-78883-C2-2-P, BIO2016-79618-R, and CTQ2017-84309-C2-2-R, and by Comunidad de Madrid grant NANOAVANSENS ref. S2013/MIT-3029. ARC acknowledges the Ramón y Cajal contract number RYC-2015-18047

Concurrent segregation and erosion effects in medium-energy iron beam patterning of silicon surfaces

This paper is part of: Special Issue on Surfaces Patterned by Ion SputteringWe have bombarded crystalline silicon targets with a 40 keV Fe+ ion beam at different incidence angles. The resulting surfaces have been characterized by atomic force, current-sensing and magnetic force microscopies, scanning electron microscopy, and x-ray photoelectron spectroscopy. We have found that there is a threshold angle smaller than 40 degrees for the formation of ripple patterns, which is definitely lower than those frequently reported for noble gas ion beams. We compare our observations with estimates of the value of the critical angle and of additional basic properties of the patterning process, which are based on a continuum model whose parameters are obtained from binary collision simulations. We have further studied experimentally the ripple structures and measured how the surface slopes change with the ion incidence angle. We explore in particular detail the fluence dependence of the pattern for an incidence angle value (40 degrees) close to the threshold. Initially, rimmed holes appear randomly scattered on the surface, which evolve into large, bug-like structures. Further increasing the ion fluence induces a smooth, rippled background morphology. By means of microscopy techniques, a correlation between the morphology of these structures and their metal content can be unambiguously established.This research is supported by the MINECO/FEDER (Spain/UE) grants Nos. MAT2017-85089-C2-1-R, MAT2016-80394-R, FIS2015-66020-C2-1-P, FIS2015-73337-JIN, FIS2016-78883-C2-2-P, and BIO2016-79618-R, and by Comunidad de Madrid grant NANOAVANSENS ref. S2013/MIT-3029. We want to thank C. Ballesteros and B. Galiana for their help in the SEM measurements. ARC acknowledges the Ramón y Cajal contract number RYC-2015-18047 and KL thanks FCT, Portugal, for her grant as Investigador FCT

Metabolically Obese Normal-Weight Phenotype as a Risk Factor for High Blood Pressure: A Five-Year Cohort

"Background: The metabolically obese normal-weight (MONW) phenotype has been considered a risk factor for different chronic diseases, but its role in high blood pressure (HBP) is still unclear. The aim of the study is to determine if the MONW phenotype constitutes a risk factor for hypertension in Peruvian adults belonging to a 5-year cohort. Methods: This is a retrospective cohort study. A secondary analysis from the database of the PERU MIGRANT study was carried out from the MONW and non-MONW cohorts; after a 5-year follow-up, the appearance of HBP was evaluated in the subjects of both cohorts. To assess the strength and magnitude of the association, a Poisson regression model (crude and adjusted) with robust variance was used. The measure of association was the relative risk (RR). Results: The incidence of HBP was 11.30%. In the multivariable analysis, subjects with the MONW phenotype had a 2.879-fold risk of presenting HBP in 5 years compared with those who were not MONW at the beginning of the study; this was adjusted for categorized age, sex, group, and state of smoker and alcohol drinker (RR: 2.055; 95% confidence interval (CI): 1.118 - 3.777; P = 0.020). Conclusions: The presence of the MONW phenotype doubled the incidence of HBP, even after adjusting for other covariates. However, studies in this field should continue. If these findings are confirmed, it should be considered that presenting an adequate weight for height should not be interpreted as a condition free of metabolic alterations, so screening for hypertension should be carried out regardless of w

The Fruit Intake–Adiposity Paradox: Findings from a Peruvian Cross-Sectional Study

"Due to the increase in obesity worldwide, international organizations have promoted the adoption of a healthy lifestyle, as part of which fruit consumption stands out. However, there are controversies regarding the role of fruit consumption in mitigating this disease. The objective of the present study was to analyze the association between fruit intake and body mass index (BMI) and waist circumference (WC) in a representative sample of Peruvians. This is an analytical cross-sectional study. Secondary data analysis was conducted using information from the Demographic and Health Survey of Peru (2019–2021). The outcome variables were BMI and WC. The exploratory variable was fruit intake, which was expressed in three different presentations: portion, salad, and juice. A generalized linear model of the Gaussian family and identity link function were performed to obtain the crude and adjusted beta coefficients. A total of 98,741 subjects were included in the study. Females comprised 54.4% of the sample. In the multivariate analysis, for each serving of fruit intake, the BMI decreased by 0.15 kg/m2 (β = −0.15; 95% CI −0.24 to −0.07), while the WC was reduced by 0.40 cm (β = −0.40; 95% CI −0.52 to −0.27). A negative association between fruit salad intake and WC was found (β = −0.28; 95% CI −0.56 to −0.01). No statistically significant association between fruit salad intake and BMI was found. In the case of fruit juice, for each glass of juice consumed, the BMI increased by 0.27 kg/m2 (β = 0.27; 95% CI 0.14 to 0.40), while the WC increased by 0.40 cm (β = 0.40; 95% CI 0.20 to 0.60). Fruit intake per serving is negatively related to general body adiposity and central fat distribution, while fruit salad intake is negatively related to central distribution adiposity. However, the consumption of fruit in the form of juices is positively associated with a significant increase in BMI and WC.

The Fruit Intake–Adiposity Paradox: Findings from a Peruvian Cross-Sectional Study

"Due to the increase in obesity worldwide, international organizations have promoted the adoption of a healthy lifestyle, as part of which fruit consumption stands out. However, there are controversies regarding the role of fruit consumption in mitigating this disease. The objective of the present study was to analyze the association between fruit intake and body mass index (BMI) and waist circumference (WC) in a representative sample of Peruvians. This is an analytical cross-sectional study. Secondary data analysis was conducted using information from the Demographic and Health Survey of Peru (2019–2021). The outcome variables were BMI and WC. The exploratory variable was fruit intake, which was expressed in three different presentations: portion, salad, and juice. A generalized linear model of the Gaussian family and identity link function were performed to obtain the crude and adjusted beta coefficients. A total of 98,741 subjects were included in the study. Females comprised 54.4% of the sample. In the multivariate analysis, for each serving of fruit intake, the BMI decreased by 0.15 kg/m2 (β = −0.15; 95% CI −0.24 to −0.07), while the WC was reduced by 0.40 cm (β = −0.40; 95% CI −0.52 to −0.27). A negative association between fruit salad intake and WC was found (β = −0.28; 95% CI −0.56 to −0.01). No statistically significant association between fruit salad intake and BMI was found. In the case of fruit juice, for each glass of juice consumed, the BMI increased by 0.27 kg/m2 (β = 0.27; 95% CI 0.14 to 0.40), while the WC increased by 0.40 cm (β = 0.40; 95% CI 0.20 to 0.60). Fruit intake per serving is negatively related to general body adiposity and central fat distribution, while fruit salad intake is negatively related to central distribution adiposity. However, the consumption of fruit in the form of juices is positively associated with a significant increase in BMI and WC.