Luttinger parameter of quasi-one-dimensional para- H2

We have studied the ground-state properties of para-hydrogen in one dimension and in quasi-one-dimensional configurations using the path-integral ground-state Monte Carlo method. This method produces zero-temperature exact results for a given interaction and geometry. The quasi-one-dimensional setup has been implemented in two forms: the inner channel inside a carbon nanotube coated with H2 and a harmonic confinement of variable strength. Our main result is the dependence of the Luttinger parameter on the density within the stable regime. Going from one dimension to quasi-one dimension, keeping the linear density constant, produces a systematic increase of the Luttinger parameter. This increase is, however, not enough to reach the superfluid regime and the system always remain in the quasicrystal regime, according to Luttinger liquid theory.Postprint (author's final draft

Fluid and registered phases in the second layer of 3He on graphite

A quantum Monte Carlo approach, considering all the corrugation effects, was used to calculate the complete phase diagram of the second 3He layer adsorbed on graphite. We found that a first-layer triangular solid was in equilibrium with a gas in the second layer. At a surface density 0.166±0.001Å-2, this fluid changes into two first-layer registered phases: 4/7 and 7/12 solids. The 7/12 arrangement transforms into an incommensurate triangular structure of ¿=0.189±0.001Å-2 upon further helium loading. A recently proposed hexatic phase was found to be unstable with respect to those commensurate solids.Postprint (published version

Análisis en régimen permanente de redes multienergéticas

El presente TFM, titulado “Análisis en régimen permanente de redes multienergéticas”, pretende servir como referencia en el análisis en régimen permanente de redes que integran múltiples portadores de energía, contribuyendo a la evolución de los tradicionales modelos que analizan las distintas redes de forma aislada. En los primeros capítulos, se pondrán en contexto los sistemas de suministro de energía, enfatizando en las características y diferencias entre las redes energéticas tradicionales y las redes multienergéticas. En cuanto a la redes multienergéticas, se explicará el valor añadido que poseen, su funcionamiento y los principios básicos que las caracterizan. Además, se expondrán dos aspectos actuales de gran relevancia: las tecnologías de almacenamiento y los elementos de acople que se utilizan para interconectar unas redes energéticas con otras. También, se tratarán los potenciales beneficios de las redes multienergéticas que, tanto en el presente como en el futuro, se acontecen cruciales debido a la crisis climática y energética que se está padeciendo a nivel global. Posteriormente, se detallarán las ecuaciones características de las distintas redes energéticas necesarias para llevar a cabo el análisis en régimen permanente. La red eléctrica, la red de gas natural y la red térmica de calor y frío serán las consideradas en este estudio. Tras la presentación de las ecuaciones, se estudiará un caso particular del análisis en régimen permanente de una red multienergética concreta. Esta red se representará de forma gráfica, se describirán las interconexiones entre los distintos portadores de energía, se expondrán los sus datos técnicos y se formularán y desarrollarán las ecuaciones que anteriormente se han presentado de forma teórica. A continuación, se presentarán los métodos numéricos iterativos de resolución considerados (FSOLVE y Newton-Raphson con jacobiano numérico), así como el procedimiento de resolución y los resultados obtenidos. Finalmente, se explicarán los pros y contras de la aplicación de ambos métodos y se verificará que los resultados obtenidos para la red eléctrica (voltajes en módulo y ángulos), la red de gas natural (presiones) y la red térmica (caudales másicos y temperaturas) son correctos, ya que cumplen con la distribución, funcionamiento, consumos y las características técnicas de la red multienergética objeto de estudioObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.b - Per a 2030, ampliar la infraestructura i millorar la tecnologia per tal d’oferir serveis d’energia moderns i sos­tenibles per a tots els països en desenvolupament, en particular els països menys avançats, els petits estats insulars en desenvolupament i els països en desenvolupament sense litoral, d’acord amb els programes de suport respectiu

Phases of 4He and H2 adsorbed on a single carbon nanotube

We acknowledge financial support from Ministerio de Ciencia e Innovación MCIN/AEI/10.13039/501100011033 (Spain) under Grants No. PID2020-113565GB-C22 and No. PID2020-113565GB-C21 and from Junta de Andalucía group PAIDI-205. M.C.G. acknowledges funding from European regional development fund (FEDER) and Junta de Andalucía Economy, Knowledge, Bussiness and University Consejería under ther especific goal 1.2.3 of the FEDER program Andalucía 2014-2020 “Promotion and generation of frontier knowledge and knowledge aimed at the challenges of society, development of emerging technologies.” under Grant No. UPO-1380159, FEDER-financed percentage 80%, and from AGAUR-Generalitat de Catalunya Grant No. 2021-SGR-01411. We also acknowledge the use of the C3UPO computer facilities at the Universidad Pablo de Olavide.Using a diffusion Monte Carlo technique, we calculated the phase diagrams of 4He and H2 adsorbed on a single (5,5) carbon nanotube, one of the narrowest that can be obtained experimentally. For a single monolayer, when the adsorbate density increases, both species undergo a series of first-order solid-solid phase transitions between incommensurate arrangements. Remarkably, the 4He lowest-density solid phase shows supersolid behavior, in contrast to the normal solid that we found for H2. The nature of the second layer is also different for both adsorbates. Contrary to what happens on graphite, the second layer of 4He on the tube is a liquid, at least up to the density corresponding to a third-layer promotion on a flat substrate. However, the second layer of H2 is a solid that, at its lowest stable density, has a small, but observable, superfluid fraction.AGAUR-Generalitat de Catalunya 2021-SGR-01411Junta de Andalucía Economy UPO-1380159FEDERMinisterio de Ciencia e Innovación PID2020-113565GB-C21, PID2020-113565GB-C22 MICINNEuropean Regional Development Fund ERDFJunta de Andalucía PAIDI-20

One-dimensional harmonically confined SU(N) fermions

We study the momentum distributions and spatial correlations of few harmonically confined SU(N) fermions using quantum Monte Carlo methods. In our study, we vary the spin degeneracy N from 2 to 6 and the total number of particles from 6 to 18. Only balanced mixtures, with the same number of atoms per spin type, and repulsive unlike-spin contact interactions are considered. Going from N=2 to N=6, with the same occupancy of each spin state, we observe an increase of atom-atom correlations. This effect is particularly significant in the momentum distributions, which show fatter tails at large k (ks>5, s being the oscillator length) when N grows, in agreement with experimental findings. Those tails also show the expected k-4 decay related to the Tan contact for different values of the spin degeneracy. According to our results, the local spin ordering and the spin-spin correlations are mainly determined by N via the Pauli exclusion principle, with minor influences from the particle-particle interactions, irrespective of the total number of confined atoms.Postprint (published version

Zero-temperature equation of state of quasi-one-dimensional H2

We have studied molecular hydrogen in a pure 1D geometry and inside a narrow carbon nanotube by means of the diffusion Monte Carlo method. The one dimensionality of H2 in the nanotube is well maintained in a large density range, this system being closer to an ideal 1D fluid than liquid 4He in the same setup. H2 shares with 4He the existence of a stable liquid phase and a quasicontinuous liquid-solid transition at very high linear densities. $1 ^{1}B^{+}_{u} \leftarrow 1 ^{1}A^{-}_{g}$Universidad Pablo de Olavide. Departamento de Sistemas Físicos, Químicos y NaturalesVersión del edito

Immigrant IBD Patients in Spain Are Younger, Have More Extraintestinal Manifestations and Use More Biologics Than Native Patients

Crohn's disease; Immigrant; Inflammatory bowel diseaseEnfermedad de Crohn; Inmigrante; Enfermedad inflamatoria del intestinoMalaltia de Crohn; Immigrant; Malaltia inflamatòria intestinalBackground: Previous studies comparing immigrant ethnic groups and native patients with IBD have yielded clinical and phenotypic differences. To date, no study has focused on the immigrant IBD population in Spain. Methods: Prospective, observational, multicenter study comparing cohorts of IBD patients from ENEIDA-registry who were born outside Spain with a cohort of native patients. Results: We included 13,524 patients (1,864 immigrant and 11,660 native). The immigrants were younger (45 ± 12 vs. 54 ± 16 years, p < 0.001), had been diagnosed younger (31 ± 12 vs. 36 ± 15 years, p < 0.001), and had a shorter disease duration (14 ± 7 vs. 18 ± 8 years, p < 0.001) than native patients. Family history of IBD (9 vs. 14%, p < 0.001) and smoking (30 vs. 40%, p < 0.001) were more frequent among native patients. The most prevalent ethnic groups among immigrants were Caucasian (41.5%), followed by Latin American (30.8%), Arab (18.3%), and Asian (6.7%). Extraintestinal manifestations, mainly musculoskeletal affections, were more frequent in immigrants (19 vs. 11%, p < 0.001). Use of biologics, mainly anti-TNF, was greater in immigrants (36 vs. 29%, p < 0.001). The risk of having extraintestinal manifestations [OR: 2.23 (1.92-2.58, p < 0.001)] and using biologics [OR: 1.13 (1.0-1.26, p = 0.042)] was independently associated with immigrant status in the multivariate analyses. Conclusions: Compared with native-born patients, first-generation-immigrant IBD patients in Spain were younger at disease onset and showed an increased risk of having extraintestinal manifestations and using biologics. Our study suggests a featured phenotype of immigrant IBD patients in Spain, and constitutes a new landmark in the epidemiological characterization of immigrant IBD populations in Southern Europe

Immigrant IBD Patients in Spain Are Younger, Have More Extraintestinal Manifestations and Use More Biologics Than Native Patients

Crohn's disease; Immigrant; Inflammatory bowel diseaseEnfermedad de Crohn; Inmigrante; Enfermedad inflamatoria intestinalMalaltia de Crohn; Immigrant; Malaltia inflamatòria de l'intestíBackground: Previous studies comparing immigrant ethnic groups and native patients with IBD have yielded clinical and phenotypic differences. To date, no study has focused on the immigrant IBD population in Spain. Methods: Prospective, observational, multicenter study comparing cohorts of IBD patients from ENEIDA-registry who were born outside Spain with a cohort of native patients. Results: We included 13,524 patients (1,864 immigrant and 11,660 native). The immigrants were younger (45 ± 12 vs. 54 ± 16 years, p < 0.001), had been diagnosed younger (31 ± 12 vs. 36 ± 15 years, p < 0.001), and had a shorter disease duration (14 ± 7 vs. 18 ± 8 years, p < 0.001) than native patients. Family history of IBD (9 vs. 14%, p < 0.001) and smoking (30 vs. 40%, p < 0.001) were more frequent among native patients. The most prevalent ethnic groups among immigrants were Caucasian (41.5%), followed by Latin American (30.8%), Arab (18.3%), and Asian (6.7%). Extraintestinal manifestations, mainly musculoskeletal affections, were more frequent in immigrants (19 vs. 11%, p < 0.001). Use of biologics, mainly anti-TNF, was greater in immigrants (36 vs. 29%, p < 0.001). The risk of having extraintestinal manifestations [OR: 2.23 (1.92-2.58, p < 0.001)] and using biologics [OR: 1.13 (1.0-1.26, p = 0.042)] was independently associated with immigrant status in the multivariate analyses. Conclusions: Compared with native-born patients, first-generation-immigrant IBD patients in Spain were younger at disease onset and showed an increased risk of having extraintestinal manifestations and using biologics. Our study suggests a featured phenotype of immigrant IBD patients in Spain, and constitutes a new landmark in the epidemiological characterization of immigrant IBD populations in Southern Europe

Layering transitions in superfluid helium adsorbed on a carbon nanotube mechanical resonator

Helium is recognized as a model system for the study of phase transitions. Of particular interest is the superfluid phase in two dimensions. We report measurements on superfluid helium films adsorbed on the surface of a suspended carbon nanotube. We measure the mechanical vibrations of the nanotube to probe the adsorbed helium film. We demonstrate the formation of helium layers up to five atoms thickness. Upon increasing the vapour pressure, we observe layer-by-layer growth with discontinuities in both the number of adsorbed atoms and the speed of sound in the adsorbed film. These hitherto unobserved discontinuities point to a series of first-order layering transitions. Our results show that helium multilayers adsorbed on a nanotube are of unprecedented quality compared to previous works. They pave the way to new studies of quantized superfluid vortex dynamics on cylindrical surfaces, of the Berezinskii-Kosterlitz-Thouless phase transition in this new geometry, perhaps also to supersolidity in crystalline single layers as predicted in quantum Monte Carlo calculations.Comment: 10 pages, 3 figure

H-2 physisorbed on graphane

We study the zero-temperature phase diagrams of H2 adsorbed on the three structures predicted for graphane (chair, boat and washboard graphane), using a diffusion Monte Carlo technique. Graphane is the hydrogenated version of graphene, in which each carbon atom changes its hybridization to sp3 and forms a covalent bond with a hydrogen atom. Our results show that the ground state of H2 adsorbed on all three types of graphane is a 3 √ ×3 √ solid, similar to the structures found both for H2 and D2 on graphene. When the H2 density increases, the system undergoes a first order phase transition to a triangular incommensurate solid. This change is direct in the case of washboard graphane, but indirect via different commensurate structures in the other cases. The total hydrogen weight percentage on the three graphane types in their ground states is in the range 10 % to 12 %, depending on if one or both graphane surfaces are covered with H2.Postprint (published version