Strong-disorder renormalization-group study of the one-dimensional tight-binding model

We formulate a strong-disorder renormalization-group (SDRG) approach to study the beta function of the tight-binding model in one dimension with both diagonal and off-diagonal disorder for states at the band center. We show that the SDRG method, when used to compute transport properties, yields exact results since it is identical to the transfer matrix method. The beta function is shown to be universal when only off-diagonal disorder is present even though single-parameter scaling is known to be violated. A different single-parameter scaling theory is formulated for this particular (particle-hole symmetric) case. Upon breaking particle-hole symmetry (by adding diagonal disorder), the beta function is shown to crossover from the universal behavior of the particle-hole symmetric case to the conventional non-universal one in agreement with the two-parameter scaling theory. We finally draw an analogy with the random transverse-field Ising chain in the paramagnetic phase. The particle-hole symmetric case corresponds to the critical point of the quantum Ising model while the generic case corresponds to the Griffiths paramagnetic phase.Comment: includes 12 pages, 4 figure

Comunicação, concorrência e processos

Texto de apoio escrito no âmbito da disciplina de Opção I - Processos, Objectos e Comunicação (1994/95), leccionada à Lic. em Matemática e Ciências de Computação

Navegar é preciso...

Introdução simples à situação actual das redes de computadores em Portugal, assim como à rede Internet e aos protocolos de comunicação mais utilizados nessa rede (telnet, ftp, finger, mail, gofer, http, ...). Os destinatários são todas as pessoas que pretendam iniciar-se ou aprender mais qualquer coisa sobre os "segredos" da comunicação e navegação numa rede de computadores

Cultural adaptation of birthing services in rural Ayacucho, Peru.

PROBLEM: Maternal mortality is particularly high among poor, indigenous women in rural Peru, and the use of facility care is low, partly due to cultural insensitivities of the health care system. APPROACH: A culturally appropriate delivery care model was developed in poor and isolated rural communities, and implemented between 1999 and 2001 in cooperation with the Quechua indigenous communities and health professionals. Data on birth location and attendance in one health centre have been collected up to 2007. LOCAL SETTING: The international nongovernmental organization, Health Unlimited, and its Peruvian partner organization, Salud Sín Límites Perú, conducted the project in Santillana district in Ayacucho. RELEVANT CHANGES: The model involves features such as a rope and bench for vertical delivery position, inclusion of family and traditional birth attendants in the delivery process and use of the Quechua language. The proportion of births delivered in the health facility increased from 6% in 1999 to 83% in 2007 with high satisfaction levels. LESSONS LEARNED: Implementing a model of skilled delivery attendance that integrates modern medical and traditional Andean elements is feasible and sustainable. Indigenous women with little formal education do use delivery services if their needs are met. This contradicts common victim-blaming attitudes that ascribe high levels of home births to 'cultural preferences' or 'ignorance'

Multipartite Entanglement Signature of Quantum Phase Transitions

We derive a general relation between the non-analyticities of the ground state energy and those of a subclass of the multipartite generalized global entanglement (GGE) measure defined by T. R. de Oliveira et al. [Phys. Rev. A 73, 010305(R) (2006)] for many-particle systems. We show that GGE signals both a critical point location and the order of a quantum phase transition (QPT). We also show that GGE allows us to study the relation between multipartite entanglement and QPTs, suggesting that multipartite but not bipartite entanglement is favored at the critical point. Finally, using GGE we were able, at a second order QPT, to define a diverging entanglement length (EL) in terms of the usual correlation length. We exemplify this with the XY spin-1/2 chain and show that the EL is half the correlation length.Comment: Published version. Incorporates correction made in erratu

On Mapping EEG Information into Music

With the rise of ever-more affordable EEG equipment available to musicians, artists and researchers, designing and building a Brain-Computer Music Interface (BCMI) system has recently become a realistic achievement. This chapter discusses previous research in the fields of mapping, sonification and musification in the context of designing a BCMI system and will be of particular interest to those who seek to develop their own. Design of a BCMI requires unique consider-ations due to the characteristics of the EEG as a human interface device (HID). This chapter analyses traditional strategies for mapping control from brain waves alongside previous research in bio-feedback musical systems. Advances in music technology have helped provide more complex approaches with regards to how music can be affected and controlled by brainwaves. This, paralleled with devel-opments in our understanding of brainwave activity has helped push brain-computer music interfacing into innovative realms of real-time musical perfor-mance, composition and applications for music therapy

Propagation of gravity waves and spread F in the low-latitude ionosphere over Tucumán, Argentina, by continuous Doppler sounding: first results

Results of systematic analysis of propagation directions and horizontal velocities of gravity waves (GWs) and spread F structures in low-latitude ionosphere (magnetic inclination ~27°) in Tucumán region, Argentina, are presented. Measurements were carried out by multipoint continuous Doppler system during 1 year from December 2012 to November 2013. It was found that meridian propagation of GWs dominated and that southward propagation prevailed in the local summer. Oblique spread structures observed in Doppler shift spectrograms and associated with spread F propagated roughly eastward at velocities from ~70 to ~180 m/s and were observed at night from ~ September to ~ March. The velocities were computed for 182 events and the azimuths for 64 events. Continuous Doppler sounding makes it possible to analyze more events compared to optical observations often used for propagation studies since the measurements do not depend on weather.Fil: Chum, J.. Institute of Atmospheric Physics; República ChecaFil: Miranda Bonomi, Fernando Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fišer, J.. Institute of Atmospheric Physics; República ChecaFil: Cabrera, M. A.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; Argentina. Universidad Tecnológica Nacional. Facultad Regional Tucuman; ArgentinaFil: Ezquer, Rodolfo Gerardo. Universidad Tecnológica Nacional. Facultad Regional Tucuman; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Burešová, D.. Institute of Atmospheric Physics; República ChecaFil: Laštovička, J.. Institute of Atmospheric Physics; República ChecaFil: Baše, J.. Institute of Atmospheric Physics; República ChecaFil: Hruška, F.. Institute of Atmospheric Physics; República ChecaFil: Molina, Maria Graciela. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Ciencias de la Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ise, Juan Eduardo. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cangemi, José Ignacio. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Šindelářová, T.. Institute of Atmospheric Physics; República Chec

Arthroscopic Scapholunate Capsuloligamentous Repair: Suture With Dorsal Capsular Reinforcement for Scapholunate Ligament Lesion

Scapholunate ligament (SLL) injury is the most frequent injury of the intrinsic carpal ligaments. The dorsal part of the SLL is the most important part for the stability of the scapholunate joint, and tears of this part and at least one of its secondary capsular attachments cause scapholunate dissociation. The arthroscopic technique most frequently used for acute injuries is reduction and fixation with Kirschner wires, and techniques that involve a primary repair of the injured ligament are performed by open surgery with efficient results. However, they lead to significant stiffness of the wrist due to injury to the soft tissue caused by damage to the secondary dorsal stabilizers; the dorsal blood supply; and in many cases, the proprioceptive innervation of the posterior interosseous nerve. We present an all-arthroscopic technique for the direct repair of acute injuries of the dorsal part of the SLL using bone anchors, complemented by a dorsal arthroscopic plication that reconstructs the dorsal capsulo-scapholunate septum of the scapholunate complex.Medicin

Architectural design of classroom to stimulate learning in higher education: an approach connected with neuroeducation and neuroarchitecture

The architectural design of learning spaces in higher education has undergone profound changes with the new educational perspectives that break with traditional pedagogical practice supported by control, hierarchy, and information dissemination. Educational institutions are gradually seeking disruptive models that enhance new learning experiences. This article presents references of innovative projects of learning and interaction spaces, that have been added to the principles of Neuroeducation and Neuroarchitecture for the development of architectural strategies for a new classroom proposal for the Bahia State University. As a result, the project brings preliminary studies to the Learning Environment Model for Higher Education (LEMHE). A flexible model, divided into three learning areas: flexible zone (active); introspection zone, and relaxing zone. This zoning aims to provide diverse experiences of pedagogical practices, added to respect the physiological needs of its users to enhance well-being and learning in higher education.info:eu-repo/semantics/publishedVersio

Alumina-Based Composites Reinforced with Ductile Particles

Al2O3/Metal composite ceramics were fabricated by the use of mechanical milling and pressureless sintering. Al2O3 + 10 vol.% of La, Mn, Si or Y were mixed and milled during 12 h at 300 rpm in a horizontal mill, then with the powder mixture it was conformed cylindrical samples by uniaxial pressing using 300 MPa. Pressed samples were sintered during 2 h in an electrical furnace at 1500°C. During sintered it was used an argon atmosphere inside the furnace in order to inhibit metal oxidation. XRD results indicate that alumina and metals retain its crystalline structure. Reached density by samples is small and less than 90%. Scanning electron microscopy observations show alumina’s microstructure with very fine and homogeneous distributions of metal particles. Both the Mn and Si are not suitable metals to improve the mechanical properties of alumina, in particular the fracture toughness. Considered rare earth metals such as yttrium and lanthanum, have yielded favorable results in improving the fracture toughness of the alumina. However, it should be made more dense materials with them to better explore this potential