Emergent quantum phase transition of a Josephson junction coupled to a high-impedance multimode resonator

Understanding phase transitions of quantum systems non-perturbatively coupled to reservoirs is challenging. In particular, the physics of a single Josephson junction coupled to a resistive environment is a long-standing fundamental problem at the center of an intense debate, strongly revived by the advent of superconducting platforms with high-impedance multi-mode resonators. Here we investigate the emergent criticality of a junction coupled to a multimode resonator when the number of modes is increased. We demonstrate analytically how the multi-mode environment renormalizes the Josephson and capacitive energies of the junction: for a homogeneous transmission line, in the thermodynamic limit the ratio between the renormalized Josephson and capacitive energies diverges when the impedance is smaller than the resistance quantum and vanishes otherwise. The critical behavior is shown not to depend on the extended or compact nature of the Josephson junction phase. Via exact diagonalization, we find that the transition surprisingly stems from a level anticrossing involving not the ground state, but the first excited state, whose energy gap vanishes in the thermodynamic limit. We show that at the transition point the spectrum displays universality not only at low frequencies. In agreement with recent experiments, we reveal striking spectral signatures of the phase transition.Comment: 9 pages, 6 figure

Nouveaux développements dans l'encapsulation de molécules hydrophobes via l'auto-assemblage de copolymères à blocs amphiphiles

Ce manuscrit décrit le développement de nouvelles stratégies dans la préparation de nanoparticules ayant une excellente capacité d’encapsuler, retenir, transporter et délivrer des molécules hydrophobes (médicaments, fragrances, agents de contraste, pesticides, etc.). Pour cela, sept systèmes de copolymères à blocs amphiphiles bien définis ont été synthétisés (principalement par polymérisation radicalaires par transfert d’atome (ATRP)) et caractérisés par des méthodes classiques. La faculté de ces macromolécules de s’auto-organiser a été utilisée pour obtenir des nanoparticules sphériques (micelles et vésicules avec une taille < 200 nm), dont les propriétés physico-chimiques ont été étudiées en détails par des techniques de diffusion de lumière et d’imagerie. Dans une seconde étape, le processus d’encapsulation de différentes molécules hydrophobes par ces nanoparticules a été mis à profit et exploré en détails. Les résultats ont montré des différences très intéressantes par rapport à la quantité maximale de molécules hydrophobes encapsulées dans le coeur de la micelle. Ces nanoparticules sont classées en trois groupes principaux, correspondant à des capacités d’encapsulation (LC) A) faibles (LC ≤ 30 % w/wp), B) modérées (30 % < LC < 70 % w/wp) et C) élevées (LC ≥ 70 % w/wp). Dans ce dernier cas, des interactions spécifiques du type acide-base dans le coeur de la particule sont responsables pour l’excellente capacité d’encapsulation systématiquement observée. Cependant, l’incorporation de grandes quantités de matières par des micelles polymériques peut provoquer une augmentation significative de la taille, ainsi que des transitions de morphologies (de micelles sphériques à cylindres à vésicules). Les résultats suggèrent très clairement que la capacité d’encapsulation des systèmes micellaires stimulables que nous avons développés peut être contrôlée avantageusement via les propriétés structurelles des molécules hydrophobes et des blocs formant le coeur de la nanoparticule.This work contemplated the design of original approaches to prepare stimulus-responsive block copolymer nanoparticles having excellent ability to encapsulate, retain, transport and deliver hydrophobic guest molecules (i.e., probes such as drugs, fragrances, contrast agents, pesticides, etc.). To this end, seven well-defined amphiphilic block copolymer systems were synthesized (mainly by atom transfer radical polymerization (ATRP)) and characterized using standard methods. Subsequently, such macromolecules were used as building blocks to obtain self-assembled spherical nanoparticles (micelles and vesicles with size < 200 nm), whose physical chemical parameters were investigated in details by light scattering and imaging techniques. In the last and most important step of this investigation, the loading of hydrophobic probes into the micelles was assessed, as well as the respective release kinetics. The results revealed astonishing differences in terms of loading contents (LC) that could be encapsulated in the particles, which could ultimately be organized in three principal groups: A) low (LC ≤ 30 % w/wp), B) moderate (30 % < LC < 70 % w/wp) and C) high (LC ≥ 70 % w/wp) loading capacity nanoparticles. In the latter case, specific (acid-base) interactions inside the hydrophobic environment of the carrier were responsible for the highly enhanced payload capacity. However, the incorporation of high amounts of hydrophobic guest molecules inside polymeric micelles can provoke not only increases in their hydrodynamic size (2RH), but also substantial changes in the morphology (e.g.: transition from spheres to cylinders to vesicles). The results reported herein suggest that the loading capacity of block copolymer micelles can be tailored through the rational design of core-forming blocks and hydrophobic guest molecules

Estudo por métodos eletroquímicos e microscópicos de filmes de fosfato formados sobre superfícies de ferro

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Quimica.Estudou-se o comportamento de eletrodos de ferro imersos em soluções de Na2HPO4 com pH 8,9 - 11,0 por métodos potenciodinâmicos (voltametria cíclica), potenciostáticos e de análise de superfície (Microscopia Eletrônica de Varredura). As conseqüências da variação da concentração hidrogeniônica e de fosfato, da velocidade de variação do potencial, do limite superior do potencial e de outras perturbações potencial/tempo especialmente elaboradas para este estudo foram detalhadamente examinadas com o objetivo de avançar no conhecimento acerca das reações envolvidas no processo de passivação do ferro, fornecendo mais detalhes sobre as mesmas. A partir dos resultados reportados neste trabalho, os quais foram analisados com base na estabilidade termodinâmica das espécies envolvidas, foi possível demonstrar as principais reações que ocorrem na superfície do eletrodo de ferro. Inicialmente há a formação de Fe3(PO4)2 e Fe(OH)2 em ca. -0,87 V/ECS. Na seqüência, estas espécies de Fe(II) são novamente oxidadas para g-FeOOH em ca. -0,36 V/ECS, sendo que esta última é transformada em Fe2O3 na região passiva. Dependendo do pH da solução (11,0) e da velocidade de variação do potencial (lenta), Fe3O4 apresenta-se como uma espécie intermediária notória entre Fe(II) e Fe(III)

Is thyroid nodule location associated with malignancy risk?

PURPOSE: Nodules located in the upper pole of the thyroid may carry a greater risk for malignancy than those in the lower pole. We conducted a study to analyze the risk of malignancy of nodules depending on location. METHODS: The records of patients undergoing thyroid-nodule fine-needle aspiration cytology (FNAC) at an academic thyroid cancer unit were prospectively collected. The nodules were considered benign in cases of a benign histology or cytology report, and malignant in cases of malignant histology. Pathological findings were analyzed based on the anatomical location of the nodules, which were also scored according to five ultrasonographic classification systems. RESULTS: Between November 1, 2015 and May 30, 2018, 832 nodules underwent FNAC, of which 557 had a definitive diagnosis. The prevalence of malignancy was not significantly different in the isthmus, right, or left lobe. Among the 227 nodules that had a precise longitudinal location noted (from 219 patients [155 females], aged 56.2±14.0 years), malignancy was more frequent in the middle lobe (13.2%; odds ratio [OR], 9.74; 95% confidence interval [CI], 1.95 to 48.59). This figure was confirmed in multivariate analyses that took into account nodule composition and the Thyroid Imaging, Reporting, and Data System (TIRADS) classification. Using the American College of Radiologists TIRADS, the upper pole location also demonstrated a slightly significant association with malignancy (OR, 6.92; 95% CI, 1.02 to 46.90; P=0.047). CONCLUSION: The risk of thyroid malignancy was found to be significantly higher for mid-lobar nodules. This observation was confirmed when suspicious ultrasonographic features were included in a multivariate model, suggesting that the longitudinal location in the lobe may be a risk factor independently of ultrasonographic appearance

Genesis and stability of tribolayers in solid lubrication: case of pair DLC-stainless steel

AbstractThe morphology, dimensions and chemical composition of tribolayers strongly depend on the pressures and temperatures acting on the contact. They are formed by reactions between surfaces in contact with each other as well as with the atmosphere, lubricants and possible contaminants. In this paper, the influence of test time (180, 500, 1000 and 2500h) on the formation and characteristics of tribolayers in pairs of DLC-stainless steel that were tested under an atmosphere of refrigerant gas R134a and without lubricating oil was analyzed. The characterization was performed using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) (morphology and chemical composition) and white light interferometry (thickness). The tribolayer thicknesses ranged from 100 to 500nm, and they were composed of elements originating from mutual transfers between the tribological pairs, as well as oxides that were more pronounced on the stainless steel surface. The results show that the tribolayers are chemically stable, maintaining the same composition over time, and their thicknesses remained constant after 1000h of testing

PTP4A1 promotes TGFβ signaling and fibrosis in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of skin and internal organs. Protein tyrosine phosphatases have received little attention in the study of SSc or fibrosis. Here, we show that the tyrosine phosphatase PTP4A1 is highly expressed in fibroblasts from patients with SSc. PTP4A1 and its close homolog PTP4A2 are critical promoters of TGFβ signaling in primary dermal fibroblasts and of bleomycin-induced fibrosis in vivo. PTP4A1 promotes TGFβ signaling in human fibroblasts through enhancement of ERK activity, which stimulates SMAD3 expression and nuclear translocation. Upstream from ERK, we show that PTP4A1 directly interacts with SRC and inhibits SRC basal activation independently of its phosphatase activity. Unexpectedly, PTP4A2 minimally interacts with SRC and does not promote the SRC-ERK-SMAD3 pathway. Thus, in addition to defining PTP4A1 as a molecule of interest for TGFβ-dependent fibrosis, our study provides information regarding the functional specificity of different members of the PTP4A subclass of phosphatases