Looking ahead in Pulmonary Rehabilitation

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Transport Coefficients of the Anderson Model via the Numerical Renormalization Group

The transport coefficients of the Anderson model are calculated by extending Wilson's NRG method to finite temperature Green's functions. Accurate results for the frequency and temperature dependence of the single--particle spectral densities and transport time $\tau(\omega,T)$ are obtained and used to extract the temperature dependence of the transport coefficients in the strong correlation limit. The low temperature anomalies in the resistivity, $\rho(T)$, thermopower, $S(T)$, thermal conductivity $\kappa(T)$ and Hall coefficient, $R_{H}(T)$, are discussed. All quantities exhibit the expected Fermi liquid behaviour at low temperature with power law dependecies on $T/T_{K}$ in very good agreement with analytic results based on Fermi liquid theory. Scattering of conduction electrons in higher, $l>0$, angular momentum channels is also considered and an expression is derived for the corresponding transport time and used to discuss the influence of non--resonant scattering on the transport properties.Comment: 45 pages, RevTeX, 28 figures, available on reques

The numerical renormalization group method for quantum impurity systems

In the beginning of the 1970's, Wilson developed the concept of a fully non-perturbative renormalization group transformation. Applied to the Kondo problem, this numerical renormalization group method (NRG) gave for the first time the full crossover from the high-temperature phase of a free spin to the low-temperature phase of a completely screened spin. The NRG has been later generalized to a variety of quantum impurity problems. The purpose of this review is to give a brief introduction to the NRG method including some guidelines of how to calculate physical quantities, and to survey the development of the NRG method and its various applications over the last 30 years. These applications include variants of the original Kondo problem such as the non-Fermi liquid behavior in the two-channel Kondo model, dissipative quantum systems such as the spin-boson model, and lattice systems in the framework of the dynamical mean field theory.Comment: 55 pages, 27 figures, submitted to Rev. Mod. Phy

Unified description of Fermi and non-Fermi liquid behavior in a conserving slave boson approximation for strongly correlated impurity models

We show that the presence of Fermi or non-Fermi liquid behavior in the SU(N) x SU(M) Anderson impurity models may be read off the infrared threshold exponents governing the spinon and holon dynamics in a slave boson representation of these models. We construct a conserving T-matrix approximation which recovers the exact exponents with good numerical accuracy. Our approximation includes both coherent spin flip scattering and charge fluctuation processes. For the single-channel case the tendency to form bound states drastically modifies the low energy behavior. For the multi-channel case in the Kondo limit the bound state contributions are unimportant.Comment: 4 pages, Latex, 3 postscript figures included Final version with minor changes in wording, to appear in Phys.Rev.Let

Anderson impurity model at finite Coulomb interaction U: generalized Non-crossing Approximation

We present an extension of the non-crossing approximation (NCA), which is widely used to calculate properties of Anderson impurity models in the limit of infinite Coulomb repulsion $U\to\infty$, to the case of finite $U$. A self-consistent conserving pseudo-particle representation is derived by symmetrizing the usual NCA diagrams with respect to empty and doubly occupied local states. This requires an infinite summation of skeleton diagrams in the generating functional thus defining the ``Symmetrized finite-U NCA'' (SUNCA). We show that within SUNCA the low energy scale $T_K$ (Kondo temperature) is correctly obtained, in contrast to other simpler approximations discussed in the literature.Comment: 7 pages, 6 figure

Out of equilibrium transport through an Anderson impurity: Probing scaling laws within the equation of motion approach

We study non-equilibrium electron transport through a quantum impurity coupled to metallic leads using the equation of motion technique at finite temperature T. Assuming that the interactions are taking place solely in the impurity and focusing in the infinite Hubbard limit, we compute the out of equilibrium density of states and the differential conductance G_2(T,V) to test several scaling laws. We find that G_2(T,V)/G_2(T,0) is a universal function of both eV/T_K and T/T_K, being T_K the Kondo temperature. The effect of an in plane magnetic field on the splitting of the zero bias anomaly in the differential conductance is also analyzed. For a Zeeman splitting \Delta, the computed differential conductance peak splitting depends only on \Delta/T_K, and for large fields approaches the value of 2\Delta . Besides the traditional two leads setup, we also consider other configurations that mimics recent experiments, namely, an impurity embedded in a mesoscopic wire and the presence of a third weakly coupled lead. In these cases, a double peak structure of the Kondo resonance is clearly obtained in the differential conductance while the amplitude of the highest peak is shown to decrease as \ln(eV/T_K). Several features of these results are in qualitative agreement with recent experimental observations reported on quantum dots.Comment: 9 pages, 7 figure

RETURN TO WORK IN ITALIAN CANCER SURVIVORS: THE INNOVATIVE SOCIAL-HEALTH CARE NETWORK

The Local Health Authority of Reggio Emilia, supported by the Manodori Foundation, decided to implement this innovative social-health care pathway that was created together with other 14 organizations in the Province of Reggio Emilia: they are Associations, labor union, training institutions, social cooperatives, and so on… Together, we created a network to address the need to go back to work of cancer patients. What happens to the working age patients with cancer in Reggio Emilia? First of all first of all the HCPs who meet the patients for diagnostic or curative reasons ask for information about the work situation. On the basis of this very first information collected, if the patient is judged at risk to lose the job he is referred to the network hub of UNA MANO: the Informa-salute service. Here, a Nurse, together with other trained personnel, make the first true assessment of the risk to lose the job. If the patients is judged at low risk, he still receive information regarding… If the patient is judged at risk to lose the job, he is sent to the OT that make a deep, second level of assessment. After this, if the risk is confirmed as moderate, the patients will received a personalized intervention targeted to… If the risk is judged very high, or the patient as already lost the job, the social part of the network is activated to implement a personalized intervention targeted to

A social-healthcare pathway to facilitate return to work of cancer survivors in Italy: The UNAMANO project

Return to work (RTW) is a major goal to promote cancer survivors' social participation. OBJECTIVE: This study describes the multidisciplinary social-healthcare pathway called UNAMANO, conceived to support RTW in this population. METHODS: UNAMANO was developed by the Azienda USL-IRCCS di Reggio Emilia, in partnership with the local branch of the Italian Medical Association, nonprofit associations, vocational training institutions, social cooperatives, a labour union, and a chartered accounting firm. RESULTS: UNAMANO is directed towards employed individuals diagnosed with cancer living in the province of RE. It was developed through four actions: A) training healthcare professionals on work-related occupational rehabilitation; B) dissemination among community and stakeholders; C) recruitment and training of volunteers; D) cancer survivor engagement and provision of a personalized comprehensive intervention. This consists in providing information and either occupational therapy to overcome barriers and facilitate RTW or social support through re-training and tailored job search strategies based on individual risk of job loss. CONCLUSIONS: UNAMANO is the first Italian multidisciplinary social-healthcare pathway supporting RTW of cancer survivors. Addressing a wide area of cancer survivors' needs, it provides personalized intervention to resolve work-related issues. We propose this patient-centred RTW model to promote an easier transition from hospital to community

Quantum Magnetic Impurities in Magnetically Ordered Systems

We discuss the problem of a spin 1/2 impurity immersed in a spin S magnetically ordered background. We show that the problem maps onto a generalization of the dissipative two level system (DTLS) with two independent heat baths, associated with the Goldstone modes of the magnet, that couple to different components of the impurity spin operator. Using analytical perturbative renormalization group (RG) methods and accurate numerical renormalization group (NRG) we show that contrary to other dissipative models there is quantum frustration of decoherence and quasi-scaling even in the strong coupling regime. We make predictions for the behavior of the impurity magnetic susceptibility that can be measured in nuclear magnetic resonance (NMR) experiments. Our results may also have relevance to quantum computation.Comment: 4 pages, 3 figure