Finite-temperature properties of the Hubbard chain with bond-charge interaction

We investigate the one-dimensional Hubbard model with an additional bond-charge interaction, recently considered in the description of compounds that exhibit strong 1D features above the temperature of ordered phases. The partition function of the model is exactly calculated for a value of the bond-charge coupling; the behavior of the specific heat and spin susceptibility as a function of temperature is derived at arbitrary filling, and particularly discussed across the occurring metal-insulator transition. The results show that the bond-charge terms weaken the spin excitations of the system.Comment: 5 pages, 3 eps figure

Adiabatic Magnetization of Superconductors as a High-Performance Cooling Mechanism

The adiabatic magnetization of a superconductor is a cooling principle proposed in the 30s, which has never been exploited up to now. Here we present a detailed dynamic description of the effect, computing the achievable final temperatures as well as the process timescales for different superconductors in various regimes. We show that, although in the experimental conditions explored so far the method is in fact inefficient, a suitable choice of initial temperatures and metals can lead to unexpectedly large cooling effect, even in the presence of dissipative phenomena. Our results suggest that this principle can be re-envisaged today as a performing refrigeration method to access the microK regime in nanodevices.Comment: 4 pages, 3 color figure

Detection of Tiny Mechanical Motion by Means of the Ratchet Effect

We propose a position detection scheme for a nanoelectromechanical resonator based on the ratchet effect. This scheme has an advantage of being a dc measurement. We consider a three-junction SQUID where a part of the superconducting loop can perform mechanical motion. The response of the ratchet to a dc current is sensitive to the position of the resonator and the effect can be further enhanced by biasing the SQUID with an ac current. We discuss the feasibility of the proposed scheme in existing experimental setups.Comment: 8 pages, 9 figure

Band and filling controlled transitions in exactly solved electronic models

We describe a general method to study the ground state phase diagram of electronic models on chains whose extended Hubbard hamiltonian is formed by a generalized permutator plus a band-controlling term. The method, based on the appropriate interpretation of Sutherland's species, yields under described conditions a reduction of the effective Hilbert space. In particular, we derive the phase diagrams of two new models; the first one exhibits a band-controlled insulator-superconductor transition at half-filling for the unusually high value $U_c=6 t$; the second one is characterized by a filling-controlled metal-insulator transition between two finite regions of the diagram.Comment: 5 pages, REVTEX, 2 eps figure

OP0086 GENDER INFLUENCE ON CLINICAL MANIFESTATIONS, DEPRESSIVE SYMPTOMS AND BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) SERUM LEVELS IN PATIENTS AFFECTED BY FIBROMYALGIA

Background:Fibromyalgia (FM) is a common rheumatic disease characterized by chronic widespread pain, sleep and mood disorders. A higher prevalence of FM in women compared with men is well known, although the specific differences in clinical manifestations related to gender are still poorly defined. Brain-Derived Neurotrophic Factor (BDNF) is an endogenous growth factor that gained attention for its potential as biomarker of several diseases, including FM and depression.Objectives:The aims of this study were to investigate gender-related difference among males and females affected by FM in clinical manifestations, depressive features and BDNF serum level, evaluating also the diagnostic potential of the latter.Methods:We consecutively enrolled adult patients affected by FM (ACR 2016) referring to our out-patient clinic. Each subject underwent clinical and answered to questionnaires for the severity of FM symptoms (Revised Fibromyalgia Impact Questionnaire, R-FIQ) and depressive symptoms (Beck Depression Inventory-II, BDI-II). We collected blood samples from a subgroup of patients of both sexes, matched for age, for BDNF serum level dosage through ELISA. BDNF levels were assessed also in a control group, matched for sex and age.Results:The cohort was composed by 201 FM patients (172 F, 29 M), mean age 49.13. Females showed higher values of R-FIQ total score (p=0,0005) as well the specific items of the R-FIQ for pain (p=0,013), fatigue (p=0,014), memory problems (p=0,007), tenderness to touch (p<0,0001), balance problems (p<0,0001) and sensitivity to environmental stimuli (p=0,012) when compared with males (fig. 1). There was no difference in BDI-II between males and females, but notably male patients reported a significantly higher frequency of coexisting depressive disorder (p=0,038) (fig. 2). Serum BDNF levels were evaluated in 40 FM patients and 40 healthy controls (HC) (F:M 1:1). BDNF levels were significantly lower in FM patients compared with HC (p<0,0001). Among FM patients, BDNF levels were lower in males compared with females (p<0,0001) (fig.3). BDNF did not correlate with any clinical and clinimetric parameter. BDNF showed a good diagnostic performance (AUC=0,89, CI95%=0,82-0,9630, p<0,0001) (fig. 4). At a cut-off value <6,47 ng/dl, BDNF showed a specificity of 75% and a sensibility of 92,31%,(CI 95%=79,68-97.35) for FM identification (LR=3,692).Conclusion:FM clinical manifestations are strongly dependant from gender. While females present a more severe disease and a higher burden of symptoms, mood disorders tend to be a major characteristic of males with FM. Reduced BDNF serum levels have been reported as typical of depressive disorders. Our findings of lower BDNF levels in male FM patients compared to females support this hypothesis. BDNF have potential as biomarker of the disease and should be validated in larger cohorts.References:[1]Sarzi-Puttini et al. Nature Reviews 2020[2]Colucci-D'Amato et al. Int J Molecular Sciences 2020[3]Nugraha et al. Rheumatol Int 2012[4]Schmitt et al. Ann Med 2016[5]Melchior et al. Neuroscience 2016[6]Stefani et al. Neuroscience Letters 2012Disclosure of Interests:None declare

Caregiver Social Support and Engagement in the Family Check-Up Across Early and Middle Childhood

The present study used a longitudinal design to examine the relationship between caregiver social support and engagement in the Family Check-Up (FCU) parenting intervention between child ages 2 to 5, 7.5 to 10.5, and 2 to 10.5. It also assessed the relationship between participation in the FCU feedback session and changes in caregiver social support satisfaction between child ages 2 to 9.5. This study used family data from the intervention arm (n = 367) of the Early Steps Multisite Study, which is a randomized control trial of the FCU among 731 low-income ethnically- diverse families using Women, Infants, and Children Nutritional Supplement Services (WIC) in urban, suburban, and rural locations. Social support satisfaction did not predict engagement in subsequent FCU feedback sessions or follow-up treatment across all age ranges. Received social support did not predict FCU engagement for child ages 2 to 5 and 7.5 to 10.5, but higher received social support at age 2 was significantly associated with greater number of received feedback sessions and follow-up treatment sessions across ages 2 to 10.5. These findings suggest that greater received support may have promoted long-term investment in the FCU and that identifying ways to engage and support caregivers with low levels of social support may provide a critical opportunity to address treatment barriers and improve engagement. Future directions are also considered, including qualitative and mixed-methods approaches and the use of more functional measures of social support

Role of the equilibrium size of Kadanoff blocks in the loop-expansion technique

A method developed by the present authors in a previous paper [Phys. Rev. E 57, 2594 (1998)] leads to the introduction of the equilibrium size of the Kadanoff blocks as a useful tool to approach the critical properties of the φ4 model. The present paper aims to elucidate the role of the equilibrium size of the Kadanoff blocks in the loop-expansion technique currently used in the field-theoretic renormalization. While the standard results are readily obtained, aspects emerge that help clarify the true nature of the smallness parameter in the loop-expansion technique

Exact thermodynamics of an Extended Hubbard Model of single and paired carriers in competition

By exploiting the technique of Sutherland's species, introduced in \cite{DOMO-RC}, we derive the exact spectrum and partition function of a 1D extended Hubbard model. The model describes a competition between dynamics of single carriers and short-radius pairs, as a function of on-site Coulomb repulsion ($U$) and filling ($\rho$). We provide the temperature dependence of chemical potential, compressibility, local magnetic moment, and specific heat. In particular the latter turns out to exhibit two peaks, both related to `charge' degrees of freedom. Their origin and behavior are analyzed in terms of kinetic and potential energy, both across the metal-insulator transition point and in the strong coupling regime.Comment: 14 pages, 15 eps figure

Blockade and Counterflow Supercurrent in exciton-condensate Josephson junctions

We demonstrate that perfect conversion between charged supercurrents in superconductors and neutral supercurrents in electron-hole pair condensates is possible via a new Andreev-like scattering mechanism. As a result, when two superconducting circuits are coupled through a bilayer exciton condensate, the superflow in both layers is drastically modified. Depending on the phase biases the supercurrents can be completely blocked or exhibit perfect drag.Comment: 4 pages, 2 figure

Negativity of the excess noise in a quantum wire capacitively coupled to a gate

The electrical current noise of a quantum wire is expected to increase with increasing applied voltage. We show that this intuition can be wrong. Specifically, we consider a single channel quantum wire with impurities and with a capacitive coupling to nearby metallic gates and find that its excess noise, defined as the change in the noise caused by the finite voltage, can be negative at zero temperature. This feature is present both for large ($c \gg c_q$) and small ($c \ll c_q$) capacitive coupling, where $c$ is the geometrical and $c_q$ the quantum capacitance of the wire. In particular, for $c \gg c_q$, negativity of the excess noise can occur at finite frequency when the transmission coefficients are energy dependent, i.e. in the presence of Fabry-P\'erot resonances or band curvature. In the opposite regime $c \lesssim c_q$, a non trivial voltage dependence of the noise arises even for energy independent transmission coefficients: at zero frequency the noise decreases with voltage as a power law when $c < c_q/3$, while, at finite frequency, regions of negative excess noise are present due to Andreev-type resonances.Comment: 11 pages, 5 figures. Revised version, references and technical details added, typos correcte