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The numerous links between allergic rhinitis and asthma have been extensively explored in the last two decades, gaining great concern within the scientific community. These two conditions frequently coexist in the same patient and share numerous pathogenetic and pathophysiological mechanisms.We reviewed major pathophysiological, epidemiological, and clinical links between allergic rhinitis and asthma. We also provided a comprehensive discussion of allergic rhinitis treatment according to current guidelines, with a particular focus on the relevance of allergic rhinitis therapies in patients with comorbid asthma.We believe that there are several unmet needs for our patients, however, there are promising advances forecasted for the future. Although allergic rhinitis is a recognized risk factor for asthma, a proper asthma detection and prevention plan in allergic rhinitis patients is not available. Allergen immunotherapy (AIT) represents a promising preventive strategy and may deserve an earlier positioning in allergic rhinitis management. A multidisciplinary approach should characterize the journey of patients with respiratory allergies, with an adequate referral to specialized Allergy/Asthma centers. Molecular Allergy Diagnosis may provide support for optimal AIT use. Finally, a possible evolution of biological treatment can be envisaged, mainly if biosimilars decrease such therapies' costs.

Background: Dupilumab, an anti-IL-4 receptor alpha monoclonal antibody, has been recently approved for the treatment of chronic rhinosinusitis with nasal polyps (CRSwNP) and moderate to severe asthma, demonstrating a rapid onset of clinical effects. CRSwNP is characterized by an extended type-2 inflammatory involvement that can be assessed by extended nitric oxide analysis. Objective: In this study we investigated whether Dupilumab is associated with a rapid improvement in extended nitric oxide parameters, lung function and clinical outcomes in patients with CRSwNP. Methods: Consecutive patients with CRSwNP and indication to be treated with Dupilumab were evaluated for extended nitric oxide analysis (exhaled, FENO; bronchial, JawNO and alveolar, CalvNO components; nasal, nNO) and lung function 15 and 30 days after treatment initiation, and for clinical outcomes (nasal polyps score, NPS; quality of life questionnaires; visual analogue scales, VAS, for main symptoms, asthma control test, ACT) after 30 days of treatment initiation. Results: 33 patients were enrolled. All extended nitric oxide and lung function parameters significantly improved after 15 days of treatment remaining stable at 30 days. NPS, VAS for main CRSwNP symptoms, quality of life questionnaires and ACT significantly improved after 30 days of treatment initiation. Conclusions: Dupilumab is associated with very rapid improvement in type 2 inflammation in all airway districts and this is associated with improved lung function and clinical parameters in patients with CRSwNP.

Made available in DSpace on 2020-12-12T02:22:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-14 In this work, we studied the dynamics of the kinematic vortices (kV) in a mesoscopic superconductor under the influence of external applied magnetic fields (H) and transport currents (J tr). A J tr(H) phase diagram is determined. We show that the vortex dynamics are profoundly affected by the presence of constrictions and by H. We find that between the Meissner and normal states, the resistive state is comprehended by three distinct states. One of these states is a kinematic vortex-antivortex pair for low values of H. For moderate values of fields, the kV state is unpaired and only a single kinematic vortex exists. In the high field regime, the kinematic vortex becomes an Abrikosov-like state with a lower velocity. It was also shown that for tenths of picoseconds, a surface barrier effect acts over the instantaneous velocity of the kV. Departamento de Física e Química Unesp Faculdade de Engenharia de Ilha Solteira Departamento de Física Unesp Faculdade de Ciências Departamento de Física e Química Unesp Faculdade de Engenharia de Ilha Solteira Departamento de Física Unesp Faculdade de Ciências

The classification of phase transitions is a central and challenging task in condensed matter physics. Typically, it relies on the identification of order parameters and the analysis of singularities in the free energy and its derivatives. Here, we propose an alternative framework to identify quantum phase transitions, employing both unsupervised and supervised machine learning techniques. Using the axial next-nearest neighbor Ising (ANNNI) model as a benchmark, we show how unsupervised learning can detect three phases (ferromagnetic, paramagnetic, and a cluster of the antiphase with the floating phase) as well as two distinct regions within the paramagnetic phase. Employing supervised learning we show that transfer learning becomes possible: a machine trained only with nearest-neighbour interactions can learn to identify a new type of phase occurring when next-nearest-neighbour interactions are introduced. All our results rely on few and low dimensional input data (up to twelve lattice sites), thus providing a computational friendly and general framework for the study of phase transitions in many-body systems., Comment: 15 pages, 8 figures

Nasal cytology is an easy, cheap, non-invasive and point-of-care method to assess nasal inflammation and disease-specific cellular features. By means of nasal cytology, it is possible to distinguish between different inflammatory patterns that are typically associated with specific diseases (ie, allergic and non-allergic rhinitis). Its use is particularly relevant when other clinical information, such as signs, symptoms, time-course and allergic sensitizations, is not enough to recognize which of the different rhinitis phenotypes is involved; for example, it is only by means of nasal cytology that it is possible to distinguish, among the non-allergic rhinitis, those characterized by eosinophilic (NARES), mast cellular (NARMA), mixed eosinophilic-mast cellular (NARESMA) or neutrophilic (NARNE) inflammation. Despite its clinical usefulness, cheapness, non-invasiveness and easiness, nasal cytology is still underused and this is at least partially due to the fact that, as far as now, there is not a consensus or an official recommendation on its methodological issues. We here review the scientific literature about nasal cytology, giving recommendations on how to perform and interpret nasal cytology.

We investigate the thermodynamics of a spin ladder model which possesses a free parameter besides the rung and leg couplings. The model is exactly solved by the Bethe Ansatz and exhibits a phase transition between a gapped and a gapless spin excitation spectrum. The magnetic susceptibility is obtained numerically and its dependence on the anisotropy parameter is determined. A connection with the compounds KCuCl3, Cu2(C5H12N2)2Cl4 and (C5H12N)2CuBr4 in the strong coupling regime is made and our results for the magnetic susceptibility fit the experimental data remarkably well.

In the present work we study the influence of the surface on the vortex structure as a function of the sample size for different temperatures. It is shown that a crossover between a hexagonal lattice, which is characteristic of the macroscopic samples, and a square lattice occurs in the vicinity of a threshold line which delimits the macro and the mesoscopic superconducting regimes, L c ( T ). Such study was carried out by computational simulations where we used the time dependent Ginzburg–Landau equations in the discretized form.

The aim of the present study was to evaluate the Epi-QoL, a new Italian-specific measure of health-related quality of life (HRQOL) for adults with epilepsy; the clinical variables that affected the HRQOL score were also assessed. The Epi-QoL is a 46-item self-administered questionnaire focusing on six domains: Physical Functioning, Cognitive Functioning, Emotional Well-Being, Social Functioning, Seizure Worry, and Medication Effects. Eight hundred fifteen patients recruited from 24 secondary and tertiary Italian centers for the care of epilepsy were assessed. The results supported the reliability and validity of the Epi-QoL as a measure of HRQOL. The variables that significantly affected HRQOL scores were: geographic area, gender, seizure frequency, prognostic categories, number of medications, comorbidity, presence of cognitive impairment, psychiatric disturbances, and disability. We believe that a new specific questionnaire for the evaluation of HRQOL in Italy can contribute much to the understanding of the influence of epilepsy on patients' lives.

The main properties of realistic models for manganites are studied using analytic mean-field approximations and computational numerical methods, focusing on the two-orbital model with electrons interacting through Jahn-Teller (JT) phonons and/or Coulombic repulsions. Analyzing the model including both interactions by the combination of the mean-field approximation and the exact diagonalization method, it is argued that the spin-charge-orbital structure in the insulating phase of the purely JT-phononic model is not qualitatively changed by the inclusion of the Coulomb interactions. As an important application of the present mean-field approximation, the CE-type AFM state, the charge-stacked structure along the z-axis, and the (3x^2-r^2)/(3y^2-r^2)-type orbital ordering are successfully reproduced based on the JT-phononic model for the half-doped manganite. Topological arguments and the relevance of the Heisenberg exchange among localized t_{\rm 2g} spins explains why the nearest-neighbor Coulomb interaction does not destroy the charge stacking structure. It is also verified that the phase-separation tendency is observed both in purely JT-phononic and purely Coulombic models in the vicinity of the hole undoped region, as long as realistic hopping matrices are used. This highlights the qualitative similarities of both approaches, and the relevance of mixed-phase tendencies in the context of manganites. In addition, the rich and complex phase diagram of the two-orbital Coulombic model in one dimension is presented. Our results provide robust evidence that Coulombic and JT-phononic approaches to manganites are not qualitatively different ways to carry out theoretical calculations, but they share a variety of common features., 23 pages, Revtex, with 15 figures embedded in the text. Submitted to Phys. Rev. B

We solve the spectrum of quantum spin chains based on representations of the Temperley-Lieb algebra associated with the quantum groups ${\cal U}% _{q}(X_{n})$ for $X_{n}=A_{1},$ $B_{n},$ $C_{n}$ and $D_{n}$. The tool is a modified version of the coordinate Bethe Ansatz through a suitable choice of the Bethe states which give to all models the same status relative to their diagonalization. All these models have equivalent spectra up to degeneracies and the spectra of the lower dimensional representations are contained in the higher-dimensional ones. Periodic boundary conditions, free boundary conditions and closed non-local boundary conditions are considered. Periodic boundary conditions, unlike free boundary conditions, break quantum group invariance. For closed non-local cases the models are quantum group invariant as well as periodic in a certain sense., Comment: 28 pages, plain LaTex, no figures, to appear in Int. J. Mod. Phys. A

This Conference is the fifth of a series of Workshops on High Energy Gamma- ray Experiments, following the Conferences held in Perugia 2003, Bari 2004, Cividale del Friuli 2005, Elba Island 2006. This year the focus was on the use of gamma-ray to study the Dark Matter component of the Universe, the origin and propagation of Cosmic Rays, Extra Large Spatial Dimensions and Tests of Lorentz Invariance., Comment: 328 pages, 7.8Mb, Proceedings of the 5th SCINEGHE Workshop, June 18-20, 2007 http://www.roma2.infn.it/SciNeGHE07/

The study of superconducting samples in mesoscopic scale presented a remarkable improvement during the last years. Certainly, such interest is based on the fact that when the size of the samples is close to the order of the temperature dependent coherence length ξ(T) and/or the size of the penetration depth λ(T), there are some significant modifications on the physical properties of the superconducting state. This contribution tests the square cross-section size limit for the occurrence (or not) of vortices in mesoscopic samples of area L2, where L varies discretely from 1ξ(0) to 8ξ(0). The time dependent Ginzburg–Landau (TDGL) equations approach is used upon taking the order parameter and the local magnetic field invariant along the z-direction. The vortex configurations at the equilibrium can be obtained from the TDGL equations for superconductivity as the system relaxes to the stationary state. The obtained results show that the limit of vortex penetration is for the square sample of size 3ξ(0)×3ξ(0) in which only a single vortex are allowed into the sample. For smaller specimens, no vortex can be formed and the field entrance into the sample is continuous and the total flux penetration occurs at higher values of H/Hc2(0), where Hc2(T) is the upper critical field. Otherwise, for larger samples different vortices patterns can be observed depending on the sample size.

A method is proposed to improve the accuracy of approximate techniques for strongly correlated electrons that use reduced Hilbert spaces. As a first step, the method involves a change of basis that incorporates exactly part of the short distance interactions. The Hamiltonian is rewritten in new variables that better represent the physics of the problem under study. A Hilbert space expansion performed in the new basis follows. The method is successfully tested using both the Heisenberg model and the $t-J$ model with holes on 2-leg ladders and chains, including estimations for ground state energies, static correlations, and spectra of excited states. An important feature of this technique is its ability to calculate dynamical responses on clusters larger than those that can be studied using Exact Diagonalization. The method is applied to the analysis of the dynamical spin structure factor $S(q,\omega)$ on clusters with $2 \times 16$ sites and 0 and 2 holes. Our results confirm previous studies (M. Troyer, H. Tsunetsugu, and T. M. Rice, Phys. Rev. $ B 53$, 251 (1996)) which suggested that the state of the lowest energy in the spin-1 2-holes subspace corresponds to the bound state of a hole pair and a spin-triplet. Implications of this result for neutron scattering experiments both on ladders and planes are discussed., Comment: 9 pages, 8 figures, Revtex + psfig; changed content

Spin models that have been proposed to describe dimerized chains, ladders, two dimensional antiferromagnets, and other compounds are here studied when some spins are replaced by spinless vacancies, such as it occurs by $Zn$ doping. A small percentage of vacancies rapidly destroys the spin gap, and their presence induces enhanced antiferromagnetic correlations near those vacancies. The study is performed with computational techniques which includes Lanczos, world-line Monte Carlo, and the Density Matrix Renormalization Group methods. Since the phenomenon of enhanced antiferromagnetism is found to occur in several models and cluster geometries, a common simple explanation for its presence may exist. It is argued that the resonating-valence-bond character of the spin correlations at short distances of a large variety of models is responsible for the presence of robust staggered spin correlations near vacancies and lattice edges. The phenomenon takes place regardless of the long distance properties of the ground state, and it is caused by a ``pruning'' of the available spin singlets in the vicinity of the vacancies. The effect produces a broadening of the low temperature NMR signal for the compounds analyzed here. This broadening should be experimentally observable in the structurally dimerized chain systems $Cu(NO_3)_2\cdot2.5H_2O$, $CuWO_4$, $(VO)_2P_2O_7$, and $Sr_{14}Cu_{24}O_{41}$, in ladder materials such as $Sr Cu_2 O_3$, in the spin-Peierls systems $CuGeO_3$ and $NaV_2 O_5$, and in several others since it is a universal effect common to a wide variety of models and compounds., 18 pages revtex with 26 figures included

The Kondo lattice Hamiltonian with ferromagnetic Hund's coupling as a model for manganites is investigated. The classical limit for the spin of the (localized) $t_{2g}$ electrons is analyzed on lattices of dimension 1,2,3 and $\infty$ using several numerical methods. The phase diagram at low temperature is presented. A regime is identified where phase separation occurs between hole undoped antiferromagnetic and hole-rich ferromagnetic regions. Experimental consequences of this novel regime are discussed. Regions of incommensurate spin correlations have also been found. Estimations of the critical temperature in 3D are compatible with experiments., Accepted in Phys. Rev. Letters

The phase diagram of two coupled anisotropic spin-1/2 Heisenberg chains forming a ladder is studied via the finite-size machinery arising from conformal invariance. Our results show that this system has similar behaviour to the anisotropic spin-1 Heisenberg chain. Both models for low values of anisotropies have a massless phase of Gaussian type, governed by a c = 1 conformal field theory. The operator that destroys the massless phase in these models is the same as in the Gaussian picture. We also verify that the massive phase in the anisotropic Heisenberg ladder has the same type of nonlocal order as that in the spin-1 Heisenberg chain.

The critical behaviour of anisotropic Heisenberg models with two kinds of antiferromagnetically exchange-coupled centers are studied numerically by using finite-size calculations and conformal invariance. These models exhibit the interesting property of ferrimagnetism instead of antiferromagnetism. Most of our results are centered in the mixed Heisenberg chain where we have at even (odd) sites a spin-S (S') SU(2) operator interacting with a XXZ like interaction (anisotropy $\Delta$). Our results indicate universal properties for all these chains. The whole phase, $1>\Delta>-1$, where the models change from ferromagnetic $( \Delta=1 )$ to ferrimagnetic $(\Delta=-1)$ behaviour is critical. Along this phase the critical fluctuations are ruled by a c=1 conformal field theory of Gaussian type. The conformal dimensions and critical exponents, along this phase, are calculated by studying these models with several boundary conditions., Comment: 21 pages, standard LaTex, to appear in J.Phys.A:Math.Gen

The influence of hypothyroidism (HO) induced by treatment with propylthiouracil on lipid composition, receptor responsiveness of M1-muscarinic receptors (M1AChRs) and metabotropic glutamate receptors (mGluRs) as well as on protein kinase C (PKC) activity was investigated in the cerebral cortex of Lewis rats. HO did not influence the lipid composition. There was a significant 2-fold increase of efficacy and 6-fold decrease of potency of carbachol-induced inositol phosphate (IP) accumulation in HO, with respect to control rats. The efficacy of trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD)-induced IP accumulation was also higher in HO (by 50%), without differences in EC50 values. The activities of soluble calcium-dependent and calcium-independent PKC were higher in HO than in control rats (both roughly 30%); membrane-associated PKCs were not modified. The data indicate that HO induces an increased responsiveness of M1AChRs and mGluRs and a rise in the soluble PKC activity that could be available and ready for translocation.

The phase diagram of the XXZ chain is calculated under the influence of homogeneous and staggered magnetic fields. The model has a rich phase structure with three types of phases. A fully ferromagnetic phase, an antiferromagnetic phase and a massless phase with partial ferromagnetic and antiferromagnetic order. This massless phase's critical fluctuations are governed by a conformal field theory with central charge c=1. When the sigma z-anisotropy Delta is zero the model is exactly integrable through a Jordan-Wigner fermionization and our results are analytic. For Delta not=0 our analysis is done numerically using lattice sizes up to M=20. Our results show that for -1

Made available in DSpace on 2022-04-29T02:57:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-11 In the present work we report the existence of a crossover between the macroscopic and mesoscopic regimes of vortex interactions in type-II superconductors. Our findings rely on a systematic procedure to determine this crossover, which is based on the influence of the surface on the vortex structure of small superconductors. An adjacent result that we have found is that near this regime transformation, the vortex lattice develops a progressive change of symmetry, from square to hexagonal, which is intimately related to the meso-to-macro crossover. Our numerical simulations have been done for a long superconducting cylinder of square cross section for a wide range of length scales and temperatures. © 2012 American Physical Society. Faculdade de Engenharia de Ilha Solteira Universidade Estadual Paulista Departamento de Física e Química, Caixa Postal 31, 15385-000, Ilha Solteira, São Paulo Universidade Estadual Paulista Instituto de Pesquisas Meteorológicas, CEP 17048-699 Bauru, São Paulo Universidade Estadual Paulista Departamento de Física Faculdade de Ciências, Caixa Postal 473, 17033-360, Bauru, São Paulo Departamento de Física Universidade Federal de São Carlos, 13565-905, São Carlos, São Paulo Centre for Advanced Study Norwegian Academy of Science and Letters, NO-0271, Oslo Faculdade de Engenharia de Ilha Solteira Universidade Estadual Paulista Departamento de Física e Química, Caixa Postal 31, 15385-000, Ilha Solteira, São Paulo Universidade Estadual Paulista Instituto de Pesquisas Meteorológicas, CEP 17048-699 Bauru, São Paulo Universidade Estadual Paulista Departamento de Física Faculdade de Ciências, Caixa Postal 473, 17033-360, Bauru, São Paulo

Made available in DSpace on 2022-04-29T00:49:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-15 We have used the density-matrix renormalization group method to study the ground-state properties of the symmetric periodic Anderson model in one dimension. We have considered lattices with up to Ns=50 sites, and electron densities ranging from quarter to half filling. Through the calculation of energies, correlation functions, and their structure factors, together with careful extrapolations (toward Ns→ ), we were able to map out a phase diagram Uvsn, where U is the electronic repulsion on f orbitals, and n is the electronic density, for a fixed value of the hybridization. At quarter filling, n=1, our data is consistent with a transition at U c1 2, between a paramagnetic (PM) metal and a spin-density-wave (SDW) insulator; overall, the region U 2 corresponds to a PM metal for all n

The effect of hypothyroidism on the lipid composition of myelin and synaptosomes isolated from adult rat brain was investigated. The animals were made hypothyroid by adding 0.05% propyl-2-thiouracil to their drinking water for four weeks. This pathological state resulted in a significant increase in the relative percentage of choline glycerophospholipids in synaptosomes with a concomitant decrease in ethanolamine glycerophospholipids as compared to controls. In myelin, hypothyroidism significantly influenced only the relative percentage of sulfatides. The effect of the hypothyroid state on mature brain was also reflected in changes in the membrane fatty acid composition. Myelin and synaptosomes showed an increase in arachidonic (20:4) and eicosatrienoic (20:3) acids and an increase in the fatty acid unsaturation index. Furthermore, the 20:4/20:3 and 20:3/18:2 ratios were lower and higher, respectively, in treated animals. The data indicate that hypothyroidism affects the lipid composition of synaptosomes and myelin even though the effects were less pronounced in myelin. The lipid changes observed in hypothyroidism may be of physiological significance, as it is well known that lipid composition modulates various membrane-bound enzymes, transporters and receptors.

A study is made of the anisotropic biquadratic spin-1 Hamiltonian introduced by Batchelor et al. (1990). This model can be represented as a sum of operators satisfying a Temperley-Lieb algebra. Its critical behaviour is explored by using the relations between mass-gap amplitudes and critical exponents predicted by conformal invariance. The model, like in the XXZ chain, is found to exhibit a line of continuously varying exponents. By comparing its eigenspectrum with that of the XXZ Hamiltonian, several exact values are predicted.

We consider local magnetic moments coupled to conduction electrons with on-site attraction, in order to discuss the interplay between pairing and magnetic order. We probe the ground state properties of this model on a one-dimensional lattice through pair binding energies and several correlation functions, calculated by means of density-matrix renormalization group. A phase diagram is obtained (for fixed electron density 1/3), from which we infer that coexistence between magnetic order and superconductivity is robust, at the expense of a continuous distortion of the magnetic arrangement of the local moments, as evidenced by a strong dependence of the characteristic wave vector k* with the coupling constants. This allows us to understand some trends of the coexistence, such as the influence of the rare earth on k*, as observed experimentally in the borocarbides., Comment: 4 two-column pages, 7 figures, RevTeX, to appear in Phys Rev B (RC)

In the present paper we develop an algorithm to solve the time dependent Ginzburg-Landau (TDGL) equations, by using the link variables technique, for circular geometries. In addition, we evaluate the Helmholtz and Gibbs free energy, the magnetization, and the number of vortices. This algorithm is applied to a circular sector. We evaluate the superconduting-normal magnetic field transition, the magnetization, and the superconducting density. Furthermore, we study the nucleation of giant and multi-vortex states for that geometry., Comment: One REVTeX file and 8 figures

Made available in DSpace on 2022-04-28T20:08:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-07-27 In this work we investigate the dynamics of vortices in a square mesoscopic superconductor. As time evolves we show how the vortices are nucleated into the sample to form a multivortex, single vortex, and giant vortex states. We illustrate how the vortices move around at the transition fields before they accommodate into an equilibrium configuration. We also calculate the magnetization and the free energy as functions of the applied magnetic field for several values of temperature. In addition, we evaluate the upper critical field. © 2006 The American Physical Society. Departamento de Física Faculdade de Ciências Universidade Estadual Paulista-UNESP, Caixa Postal 473, 17033-360, Bauru-SP Departamento de Física Universidade Federal de São Carlos-UFSCar, Caixa Postal 676, 13566-905, São Carlos-SP Departamento de Física Faculdade de Ciências Universidade Estadual Paulista-UNESP, Caixa Postal 473, 17033-360, Bauru-SP

We discuss the interplay between electronic correlations and an underlying superlattice structure in determining the period of charge density waves (CDW's), by considering a one-dimensional Hubbard model with a repeated (non-random) pattern of repulsive (U>0) and free (U=0) sites. Density matrix renormalization group diagonalization of finite systems (up to 120 sites) is used to calculate the charge-density correlation function and structure factor in the ground state. The modulation period can still be predicted through effective Fermi wavevectors, k_F*, and densities, and we have found that it is much more sensitive to electron (or hole) doping, both because of the narrow range of densities needed to go from q*=0 to ��, but also due to sharp 2k_F*-4k_F* transitions; these features render CDW's more versatile for actual applications in heterostructures than in homogeneous systems., 4 pages, 5 figures, to appear in Phys Rev B

Recent calculations in the context of ladder systems, but with implications also for high-Tc two-dimensional (2D) systems, are described here. In particular, efforts are concentrated on the influence of a hole-hole electrostatic repulsion on holepair binding in the t−J model on ladders. It is concluded that the pairs are very robust because a nearest-neighbor hole-hole repulsion of strength ~5J is needed to break the pairs. In the second part of the paper, the spectral function of holes is provided on up to 2×20 clusters using a new numerical technique. A gap in the spectrum caused by hole binding is observed, as well as flat regions near (π, 0). Implications for studies of high-Tc materials are discussed.

Naturally occuring or man-made systems displaying periodic spatial modulations of their properties on a nanoscale constitute superlattices. Such modulated structures are important both as prototypes of simple nanotechnological devices and as particular examples of emerging spatial inhomogeneity in interacting many-electron systems. Here we investigate the effect different types of modulation of the system parameters have on the ground-state energy and the charge-density distribution of the system. The superlattices are described by the inhomogeneous attractive Hubbard model, and the calculations are performed by density-functional and density-matrix renormalization group techniques. We find that modulations in local electric potentials are much more effective in shaping the system's properties than modulations in the attractive on-site interaction. This is the same conclusions we previously (Phys. Rev. B 71, 125130) obtained for repulsive interactions, suggesting that it is not an artifact of a specific state, but a general property of modulated structures., Comment: 8 pages, 2 figures

We calculate ground-state energies and density distributions of Hubbard superlattices characterized by periodic modulations of the on-site interaction and the on-site potential. Both density-matrix renormalization group and density-functional methods are employed and compared. We find that small variations in the on-site potential $v_i$ can simulate, cancel, or even overcompensate effects due to much larger variations in the on-site interaction $U_i$. Our findings highlight the importance of nanoscale spatial inhomogeneity in strongly correlated systems, and call for reexamination of model calculations assuming spatial homogeneity., Comment: 5 pages, 1 table, 4 figures, to appear in PRB

This is an introductory course to the Lanczos Method and Density Matrix Renormalization Group Algorithms(DMRG), two among the leading numerical techniques applied in studies of low-dimensional quantum models. The idea of studying the models on clusters of a finite size in order to extract their physical properties is briefly discussed. The important role played by the model symmetries is also examined. Special emphasis is given to the DMRG., Comment: 36 pages, 4 figures, standard LaTex, Brazilian School on Statistical Mechanics (2002), PDF and PS files available at http://www.sbf.if.usp.br/bjp

We consider fermions in one-dimensional superlattices (SL's), modeled by site-dependent Hubbard-U couplings arranged in a repeated pattern of repulsive (i.e., U>0) and free (U=0) sites. Density Matrix Renormalization Group (DMRG) diagonalization of finite systems is used to calculate the local moment and the magnetic structure factor in the ground state. We have found four regimes for magnetic behavior: uniform local moments forming a spin-density wave (SDW), `floppy' local moments with short-ranged correlations, local moments on repulsive sites forming long-period SDW's superimposed with short-ranged correlations, and local moments on repulsive sites solely with long-period SDW's; the boundaries between these regimes depend on the range of electronic densities, rho, and on the SL aspect ratio. Above a critical electronic density, rho_{uparrow downarrow}, the SDW period oscillates both with rho and with the spacer thickness. The former oscillation allows one to reproduce all SDW wave vectors within a small range of electronic densities, unlike the homogeneous system. The latter oscillation is related to the exchange oscillation observed in magnetic multilayers. A crossover between regimes of `thin' to `thick' layers has also been observed., 9 two-column pages, 10 figures

Spin incommensurability (IC) has been recently experimentally discovered in the hole-doped Ni-oxide chain compound ${\mathrm{Y}}_{2\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{BaNiO}}_{5}$ [G. Xu et al., Science 289, 419 (2000)]. Here a two orbital model for this material is studied using computational techniques. Spin IC is observed in a wide range of densities and couplings. The phenomenon originates in antiferromagnetic correlations ``across holes'' dynamically generated to improve hole movement, as it occurs in the one-dimensional Hubbard model and in recent studies of the two-dimensional extended $t\ensuremath{-}J$ model. The close proximity of ferromagnetic and phase-separated states in parameter space is also discussed.

The influence of a nearest-neighbor Coulomb repulsion of strength V on the properties of the Ferromagnetic Kondo model is analyzed using computational techniques. The Hamiltonian studied here is defined on a chain using localized S=1/2 spins, and one orbital per site. Special emphasis is given to the influence of the Coulomb repulsion on the regions of phase separation recently discovered in this family of models, as well as on the double-exchange-induced ferromagnetic ground state. When phase separation dominates at V=0, the Coulomb interaction breaks the large domains of the two competing phases into small ``islands'' of one phase embedded into the other. This is in agreement with several experimental results, as discussed in the text. Vestiges of the original phase separation regime are found in the spin structure-factor as incommensurate peaks, even at large values of V. In the ferromagnetic regime close to density $n=0.5$, the Coulomb interaction induces tendencies to charge ordering without altering the fully polarized character of the state. This regime of ``charge- ordered ferromagnetism'' may be related with experimental observations of a similar phase by C. H. Chen and S-W. Cheong (Phys. Rev. Lett. 76, 4042 (1996)). Our results reinforce the recently introduction notion (see e.g., S. Yunoki et al., Phys. Rev. Lett. 80, 845 (1998)) that in realistic models for manganites analyzed with unbiased many-body techniques, the ground state properties arise from a competition between ferromagnetism and phase-separation/charge-ordering tendencies., Comment: 11 pages with 14 ps figures embedded in the text

Visual attention in dementia of Alzheimer's disease (AD) has not been investigated as extensively as memory or language. The aim of this research was to study the orienting of attention in patients with AD (which temporo-parietal areas are primarily affected) compared with patients with Parkinson-Dementia, Parkinson's disease, and normal controls, using the Posner paradigm. Subjects were instructed to respond by pressing a response key after the appearance of a target at the same location (valid trial) or at the opposite location (invalid trial) indicated by a central cue (arrow). According to the experimental procedure developed by Posner, it has been hypothesized that parietal lobes are involved in "disengagement operation" (when attention has to move from one location to another in the controlateral field). Results showed no differences between AD and the other groups and between left and right hemifield. In conclusion, the authors did not find any sign of difficulty with disengagement, and results are discussed in terms of Kinsbourne's interpretation of a balance between hemispheres.

We applied the Density Matrix Renormalization Group to the XXZ spin-1 quantum chain. In studing this model we aim to clarify controversials about the point where the massive Haldane phase appears., Comment: 2 pages (standart LaTex), 1 figure (PostScript) uuencoded

The administration to rats of tryptophan (CAS 73-22-3) in high dosage causes a significant increase in pain threshold values. The analgesic effects of tryptophan are potentiated by allopurinol (CAS 315-30-0). The analgesic effects shown by tryptophan injection are associated with increased levels of serotonin and 5-hydroxyindoleacetic acid in some areas of the brain. The combined allopurinol and tryptophan treatment elevates the serotonin levels furtherly when they are compared with the values observed in animals receiving tryptophan only. The analgesia caused by tryptophan administration has been attributed to an increased activity of the serotoninergic system involved in the control of pain transmission.

The Fuld formula and the linear discriminant function applied to WAIS subtest scores were tested for their ability to identify Alzheimer's disease and senile dementia of the Alzheimer type in a group of 101 demented subjects. The sensitivity and specificity of Fuld's formula for Alzheimer dementia against other dementias were 44.2% and 73.8% respectively; when compared with an age-matched normal control group specificity was 91.4%. When the linear discriminant function was applied only WAIS subtest scores in "similarities and digit span" and "object assembly" significantly differentiated Alzheimer from other dementias (sensitivity 61.5% and specificity 63.3%). Specificity increased to 97.1% when the function was applied to discriminate Alzheimer from normal controls. Discriminant analysis applied to other WAIS subtests for the two demented groups revealed "picture completion" as significantly differentiating the groups but it did not contribute to diagnostic accuracy. WAIS scores are of limited value in the differential diagnosis of dementias.

We discuss the comments presented by Okamoto and Nomura about the phase diagram of the XXZ chain under the influence of an external staggered magnetic field, reported by Alcaraz and Malvezzi.