Elastocaloric-effect-induced adiabatic magnetization in paramagnetic salts due to the mutual interactions.

The temperature change under adiabatic stress, i.e., the elastocaloric effect, is a well-understood phenomenon and of particular interest due to its potential application in alternative ways for refrigeration. Here, we demonstrate that in the regime of low-temperatures (a few mK) real paramagnets can be magnetized when compressed adiabatically without applied magnetic field. Such adiabatic magnetization is a genuine many-body problem, stemming from the inherent dipolar mutual interactions between adjacent magnetic moments. We showcase experimental setups to carry out adiabatic magnetization and thus to access such a subtle effect. Perspectives of further investigations by controlling the mutual interactions in Bose-Einstein condensates in magnetic insulators and dipolar spin-ice systems via the adiabatic increase of temperature are also presented. Yet, we discuss the connection between the elastic Grüneisen parameter and the shift on the critical temperature of second-order phase transitions under adiabatic stress, as well as its connection with the Ehrenfest relation.

Epidemics, the Ising-model and percolation theory: A comprehensive review focused on Covid-19.

We revisit well-established concepts of epidemiology, the Ising-model, and percolation theory. Also, we employ a spin S = 1/2 Ising-like model and a (logistic) Fermi-Dirac-like function to describe the spread of Covid-19. Our analysis show that: (i) in many cases the epidemic curve can be described by a Gaussian-type function; (ii) the temporal evolution of the accumulative number of infections and fatalities follow a logistic function; (iii) the key role played by the quarantine to block the spread of Covid-19 in terms of an interacting parameter between people. In the frame of elementary percolation theory, we show that: (i) the percolation probability can be associated with the probability of a person being infected with Covid-19; (ii) the concepts of blocked and non-blocked connections can be associated, respectively, with a person respecting or not the social distancing. Yet, we make a connection between epidemiological concepts and well-established concepts in condensed matter Physics.

Unveiling the Physics of the Mutual Interactions in Paramagnets.

In real paramagnets, there is always a subtle many-body contribution to the system's energy, which can be regarded as a small effective local magnetic field (Bloc). Usually, it is neglected, since it is very small when compared with thermal fluctuations and/or external magnetic fields (B). Nevertheless, as both the temperature (T) → 0 K and B → 0 T, such many-body contributions become ubiquitous. Here, employing the magnetic Grüneisen parameter (Γmag) and entropy arguments, we report on the pivotal role played by the mutual interactions in the regime of ultra-low-T and vanishing B. Our key results are: i) absence of a genuine zero-field quantum phase transition due to the presence of Bloc; ii) connection between the canonical definition of temperature and Γmag; and iii) possibility of performing adiabatic magnetization by only manipulating the mutual interactions. Our findings unveil unprecedented aspects emerging from the mutual interactions.

Quality of life in patients with peripheral artery disease.

BACKGROUND: Vascular diseases have a direct influence on quality of life (QoL) and directly affect patients' biopsychosocial aspects. Quality of life is therefore an important element for evaluation of vascular interventions. OBJECTIVE: To assess QoL in inpatients with peripheral arterial disease at a vascular surgery service in a charitable tertiary hospital. METHODS: This is an exploratory study, with a cross-sectional design, conducted at a vascular surgery service in a charitable tertiary hospital, assessing patients with peripheral arterial disease using two questionnaires, one on quality of life (the WHOQOL-Bref short form) and the other on sociodemographic conditions. RESULTS: It was observed that the physical domain, environment domain and total QoL scores were the lowest for the whole sample of 127 interviewees. Additionally, an intragroup analysis showed that men scored higher in all domains when compared with women, with the exception of the social relationships domain. CONCLUSIONS: Women with peripheral arterial disease exhibited lower scores than men in all domains of the QoL questionnaire, except for social relationships.

Qualidade de vida em pacientes com doença arterial periférica / Quality of life in patients with peripheral artery disease

As doenças vasculares influenciam a qualidade de vida (QV) e afetam de forma direta o aspecto biopsicossocial dos indivíduos. Sendo assim, a QV é uma importante forma de avaliação das intervenções vasculares. Objetivo: Avaliar a QV em pacientes com doença arterial periférica internados no serviço de cirurgia vascular em um hospital terciário beneficente. Métodos: Trata-se de um estudo exploratório, com desenho transversal, em um serviço de cirurgia vascular em um hospital terciário beneficente, no qual pacientes com doença arterial periférica foram avaliados através de dois questionários, sendo um a respeito de qualidade de vida (versão abreviada WHOQOL-Bref) e outro sobre as condições sociodemográficas. Resultados: Foi observado que os domínios físico, meio ambiente e QV total obtiveram os menores escores entre os 127 entrevistados. Além disso, uma análise intragrupo demonstrou que os homens obtiveram pontuação maior em todos os domínios quando comparados às mulheres, com exceção do domínio de relações sociais. Conclusão: As mulheres com doença arterial periférica apresentaram uma menor pontuação em todos os domínios do questionário de QV, exceto no de relações sociais, quando comparadas aos homens.

Vascular diseases have a direct influence on quality of life (QoL) and directly affect patients' biopsychosocial aspects. Quality of life is therefore an important element for evaluation of vascular interventions. Objective: To assess QoL in inpatients with peripheral arterial disease at a vascular surgery service in a charitable tertiary hospital. Methods: This is an exploratory study, with a cross-sectional design, conducted at a vascular surgery service in a charitable tertiary hospital, assessing patients with peripheral arterial disease using two questionnaires, one on quality of life (the WHOQOL-Bref short form) and the other on sociodemographic conditions. Results: It was observed that the physical domain, environment domain and total QoL scores were the lowest for the whole sample of 127 interviewees. Additionally, an intragroup analysis showed that men scored higher in all domains when compared with women, with the exception of the social relationships domain. Conclusions: Women with peripheral arterial disease exhibited lower scores than men in all domains of the QoL questionnaire, except for social relationships.

Probing the Mott physics in κ-(BEDT-TTF)2X salts via thermal expansion.

In the field of interacting electron systems the Mott metal-to-insulator (MI) transition represents one of the pivotal issues. The role played by lattice degrees of freedom for the Mott MI transition and the Mott criticality in a variety of materials are current topics under debate. In this context, molecular conductors of the κ-(BEDT-TTF)2X type constitute a class of materials for unraveling several aspects of the Mott physics. In this review, we present a synopsis of literature results with focus on recent expansivity measurements probing the Mott MI transition in this class of materials. Progress in the description of the Mott critical behavior is also addressed.

Lattice strain accompanying the colossal magnetoresistance effect in EuB6.

The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB(6), which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB(6) may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region, and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of colossal magnetoresistance materials.

Charge-ordering transition in (TMTTF)2X explored via dilatometry.

Charge-ordering phenomena have been highly topical over the past few years. A phase transition towards a charge-ordered state has been observed experimentally in several classes of materials. Among them, many studies have been devoted to the family of quasi-one-dimensional organic charge-transfer salts (TMTTF)2X, where (TMTTF) stands for tetramethyltetrathiafulvalene and X for a monovalent anion (X = PF6, AsF6 and SbF6). However, the relationship between the electron localization phenomena and the role of the lattice distortion in stabilizing the charge-ordering pattern is poorly documented in the literature. Here we present a brief overview of selected literature results, with emphasis placed on recent thermal expansion experiments probing the charge-ordering transition of these salts.

High-resolution thermal expansion measurements under helium-gas pressure.

We report on the realization of a capacitive dilatometer, designed for high-resolution measurements of length changes of a material for temperatures 1.4 K ≤ T ≤ 300 K and hydrostatic pressure P ≤ 250 MPa. Helium ((4)He) is used as a pressure-transmitting medium, ensuring hydrostatic-pressure conditions. Special emphasis has been given to guarantee, to a good approximation, constant-pressure conditions during temperature sweeps. The performance of the dilatometer is demonstrated by measurements of the coefficient of thermal expansion at pressures P ~/= 0.1 MPa (ambient pressure) and 104 MPa on a single crystal of azurite, Cu(3)(CO(3))(2)(OH)(2), a quasi-one-dimensional spin S = 1/2 Heisenberg antiferromagnet. The results indicate a strong effect of pressure on the magnetic interactions in this system.

Multiferroicity in an organic charge-transfer salt that is suggestive of electric-dipole-driven magnetism.

Multiferroics, showing simultaneous ordering of electrical and magnetic degrees of freedom, are remarkable materials as seen from both the academic and technological points of view. A prominent mechanism of multiferroicity is the spin-driven ferroelectricity, often found in frustrated antiferromagnets with helical spin order. There, as for conventional ferroelectrics, the electrical dipoles arise from an off-centre displacement of ions. However, recently a different mechanism, namely purely electronic ferroelectricity, where charge order breaks inversion symmetry, has attracted considerable interest. Here we provide evidence for ferroelectricity, accompanied by antiferromagnetic spin order, in a two-dimensional organic charge-transfer salt, thus representing a new class of multiferroics. We propose a charge-order-driven mechanism leading to electronic ferroelectricity in this material. Quite unexpectedly for electronic ferroelectrics, dipolar and spin order arise nearly simultaneously. This can be ascribed to the loss of spin frustration induced by the ferroelectric ordering. Hence, here the spin order is driven by the ferroelectricity, in marked contrast to the spin-driven ferroelectricity in helical magnets.

Enhanced critical temperature in a dual-layered molecular superconductor.

Single-crystal X-ray diffraction has shown that the high-critical-temperature (T(c)) phase of the filamentary molecular superconductor (BEDT-TTF)(2)Ag(CF(3))(4)(1,1,2-trichloroethane) [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] contains layers of BEDT-TTF radical cations with alternating κ- and α'-type packing motifs. This molecule-based superconductor with dual BEDT-TTF packing motifs has a T(c) five times higher than that of its polymorph that contains only κ-type packing.

Scaling theory of the mott transition and breakdown of the Grüneisen scaling near a finite-temperature critical end point.

We discuss a scaling theory of the lattice response in the vicinity of a finite-temperature critical end point. The thermal expansivity is shown to be more singular than the specific heat such that the Grüneisen ratio diverges as the critical point is approached, except for its immediate vicinity. More generally, we express the thermal expansivity in terms of a scaling function which we explicitly evaluate for the two-dimensional Ising universality class. Recent thermal expansivity measurements on the layered organic conductor κ-(BEDT-TTF)2X close to the Mott transition are well described by our theory.