Finite-sized Heisenberg chains and magnetism of one-dimensional metal systems

We present a combined experimental and theoretical study of the magnetization of one-dimensional atomic cobalt chains deposited on a platinum surface. We discuss the intrinsic magnetization parameters derived by X-ray magnetic circular dichroism measurements and the observation of ferromagnetic order in one dimension in connection with the presence of strong, dimensionality-dependent anisotropy energy barriers of magnetocrystalline origin. An explicit transfer matrix formalism is developed to treat atomic chains of finite length within the anisotropic Heisenberg model. This model allows us to fit the experimental magnetization curves of cobalt monatomic chains, measured parallel to the easy and hard axes, and provides values of the exchange coupling parameter and the magnetic anisotropy energy consistent with those reported in the literature. The analysis of the spin-spin correlation as a function of temperature provides further insight into the tendency to magnetic order in finite-sized one-dimensional system

Proton NMR study of spin dynamics in the magnetic organic chains M (hfac)3 NITEt (M=Eu3+,Gd3+)

In this work, we present a nuclear magnetic resonance (NMR) study of the spin dynamics in the rare-earth-based low-dimensional molecular magnetic chains Eu(hfac)3NITEt and Gd(hfac)3NITEt (in short, Eu-Et and Gd-Et). Although both samples are based on the same chemical building block, [(hfac)3NITEt], their magnetic properties change dramatically when the Eu3+ ion, which is nonmagnetic at low temperatures, is substituted by the magnetic Gd3+ ion. The present proton NMR investigation shows that, down to the lowest investigated temperature (T=1.5 K for Gd-Et and T=3 K for Eu-Et), the Eu-Et chain behaves as a one-dimensional Heisenberg model with antiferromagnetic exchange coupling (J=-20 K) between s=1/2 organic radicals, and has a T-independent exchange frequency (\u3c9e=2.6 71012 rad/s). In the Gd-Et chain, in contrast, a competition arises between nearest-neighbor ferromagnetic coupling and next-nearest-neighbor antiferromagnetic coupling; moreover, two phase transitions have previously been found, in agreement with Villain's conjecture: a first transition, at T0=2.2 K, from a high temperature paramagnetic phase to a chiral spin liquid phase, and a second transition, at TN=1.9 K, to a three-dimensional helical spin solid phase. Contrary to the Eu-Et chain (whose three-dimensional ordering temperature is estimated to insurge at very low, TN 480.3 K), critical spin dynamics effects have been measured in the Gd-Et chain on approaching TN=1.9 K: namely, a divergence of the proton nuclear spin-lattice relaxation rate 1/T1, which in turn produces a sudden wipe-out of the NMR signal in a very narrow (\u394T 3c0.04 K) temperature range above TN. Below TN, an inhomogeneous broadening of the NMR line indicates a complete spin freezing. At T0=2.2 K, instead, such critical effects are not observed because NMR measurements probe the two-spin correlation function, while the chiral spin liquid phase transition is associated with a divergence of the four-spin correlation function

Nonlinear excitations in CsNiF3 in magnetic fields perpendicular to the easy plane

Experimental and numerical studies of the magnetic field dependence of the specific heat and magnetization of single crystals of CsNiF3 have been performed at 2.4 K, 2.9 K, and 4.2 K in magnetic fields up to 9 T oriented perpendicular to the easy plane. The experimental results confirm the presence of the theoretically predicted double peak structure in the specific heat arising from the formation of nonlinear spin modes. The demagnetizing effects are found to be negligible, and the overall agreement between the data and numerical predictions is better than reported for the case when the magnetic field was oriented in the easy plane. Demagnetizing effects might play a role in generating the difference observed between theory and experiment in previous work analyzing the excess specific heat using the sine-Gordon model.Comment: 6 pages, 5 figures, submitted to Phys. Rev.

The bank lending channel: an empirical assessment of measures to stimulate bank lending in the European Union

This thesis first examines the role of banks in the transmission mechanism of monetary policy by focusing on the eight European new member States of Central and Eastern Europe over the 2004-2013 period. We specifically investigate the influence of monetary policy changes on bank lending activity and if this potential influence is contingent on bank characteristics, such as banks’ size, capital, liquidity, risk factor and market power. Moreover, we focus on the prospective role of banks in the monetary policy transmission mechanism in order to reveal any clear trends in banks’ lending behaviour during the 2008-2011 financial crisis. Secondly, we investigate the impact of a protracted period of low monetary policy rates on loosening of banks’ credit standards regarding enterprises, households and consumer loans through concentrating on the nine Eurozone countries involved since the initiation of the Euro area Bank Lending Survey in the three distinct time frames of pre- (2002Q4-2008Q3), mid- (2008Q4-2010Q4) and post- (2011Q1-2014:Q4) financial crisis. Furthermore, we test the fundamental concept of the risk taking channel by examining excessive risk-taking behaviour by banks in stressed vs. non-stressed countries of the Eurozone. In an additional analysis, the efficacy of the European Central Bank’s 3 year Long-Term Refinancing Operations is evaluated in great depth in order to determine whether banks’ credit standards have been softened and the degree to which demand for loans has increased. Thirdly, we explore the financing structure of bank lending constrained Small and Medium Sized Enterprises in the eleven Eurozone countries by utilising firm-level data over the period of 2009 to 2014. We estimate if bank lending constrained firms demonstrate relatively more usage or requests for alternative financing. Additionally, a comprehensive investigation is presented by unveiling the impact and determinants of various financing constraints including credit lines, bank loans, trade credit and other lending on Eurozone firms. Furthermore, the notion of discouraged borrowers originally formulated by Kon and Storey (2003) is empirically evaluated. Finally, we present the conclusion of our research by further outlining its limitations and prospective scope for future studie

Recovery of dialysis patients with COVID-19 : health outcomes 3 months after diagnosis in ERACODA

Background. Coronavirus disease 2019 (COVID-19)-related short-term mortality is high in dialysis patients, but longer-term outcomes are largely unknown. We therefore assessed patient recovery in a large cohort of dialysis patients 3 months after their COVID-19 diagnosis. Methods. We analyzed data on dialysis patients diagnosed with COVID-19 from 1 February 2020 to 31 March 2021 from the European Renal Association COVID-19 Database (ERACODA). The outcomes studied were patient survival, residence and functional and mental health status (estimated by their treating physician) 3 months after COVID-19 diagnosis. Complete follow-up data were available for 854 surviving patients. Patient characteristics associated with recovery were analyzed using logistic regression. Results. In 2449 hemodialysis patients (mean ± SD age 67.5 ± 14.4 years, 62% male), survival probabilities at 3 months after COVID-19 diagnosis were 90% for nonhospitalized patients (n = 1087), 73% for patients admitted to the hospital but not to an intensive care unit (ICU) (n = 1165) and 40% for those admitted to an ICU (n = 197). Patient survival hardly decreased between 28 days and 3 months after COVID-19 diagnosis. At 3 months, 87% functioned at their pre-existent functional and 94% at their pre-existent mental level. Only few of the surviving patients were still admitted to the hospital (0.8-6.3%) or a nursing home (∼5%). A higher age and frailty score at presentation and ICU admission were associated with worse functional outcome. Conclusions. Mortality between 28 days and 3 months after COVID-19 diagnosis was low and the majority of patients who survived COVID-19 recovered to their pre-existent functional and mental health level at 3 months after diagnosis

Performance appraisal and justice perceptions: A scenario-based experimental study

Purpose An accurate and fair organization\u2019s performance appraisal system can improve motivation and development of employees (Ilgen et al., 1979); on the other hand, employees\u2019 frustration and extreme dissatisfaction can increase when appraisal system is biased and arbitrary (Skarlicki & Folger, 1997). Building on the organizational justice theory, we hypothesized that equity perceptions were influenced by: performance rating formats (Absolute vs relative), participants\u2019 voice (voice vs no voice) and results (positive vs negative). Design/Methodology A scenario-based experimental study was used to test these assumptions. The research involved 244 Italian participants from several organizational contexts recruited on web through an on-line questionnaire. Results The ANOVA analyses revealed that participants\u2019 voice (voice-modality) affected the equity perceptions. Particularly, participants in absolute rating format conditions and with positive results showed a higher level of procedural and interpersonal justice comparing for those dealing with an opposite situation. Furthermore we found significant results between participant\u2019s voice and rating results in relation to perception of distributive justice. Limitations The study relied on self-report data, and the descriptions of the company and the scenarios were hypothetical (though based on existing firms)

Leyendas negras e leggende auree

Ampia carrellata nella storia di pregiudizi e degli stereotipi religiosi, politici, letterari e culturali fra Italia, Spagna e America latina dal Medioevo ai giorni nostr