Effects of nanoscale spatial inhomogeneity in strongly correlated systems

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 PR

Quantum Correlations and Coherence in Spin-1 Heisenberg Chains

We explore quantum and classical correlations along with coherence in the ground states of spin-1 Heisenberg chains, namely the one-dimensional XXZ model and the one-dimensional bilinear biquadratic model, with the techniques of density matrix renormalization group theory. Exploiting the tools of quantum information theory, that is, by studying quantum discord, quantum mutual information and three recently introduced coherence measures in the reduced density matrix of two nearest neighbor spins in the bulk, we investigate the quantum phase transitions and special symmetry points in these models. We point out the relative strengths and weaknesses of correlation and coherence measures as figures of merit to witness the quantum phase transitions and symmetry points in the considered spin-1 Heisenberg chains. In particular, we demonstrate that as none of the studied measures can detect the infinite order Kosterlitz-Thouless transition in the XXZ model, they appear to be able to signal the existence of the same type of transition in the biliear biquadratic model. However, we argue that what is actually detected by the measures here is the SU(3) symmetry point of the model rather than the infinite order quantum phase transition. Moreover, we show in the XXZ model that examining even single site coherence can be sufficient to spotlight the second-order phase transition and the SU(2) symmetry point.Comment: 8 pages. 5 figure

Work and organizational psychology paradigms, thematic streams and tensions in Brazil

O panorama de abordagens da psicologia do trabalho e das organizações (PTO) no Brasil mostra grande diversidade teórica e metodológica que reflete a presença de distintos paradigmas científicos na delimitação e organização desse campo. O objetivo deste artigo é analisar esses paradigmas e relacioná-los com três eixos temáticos da PTO no Brasil: o do comportamento, o da subjetividade e o clínico. Investiga-se os fundamentos epistemológicos e metodológicos, alguns trabalhos e autores de cada um desses eixos, discutindo sua contribuição para o campo da PTO no Brasil. O artigo desenvolve uma discussão sobre as tensões existentes entre esses eixos, derivadas da pressão de corresponderem, ao mesmo tempo, a critérios de rigor acadêmico e relevância organizacional. O artigo, por fim, mostra a diversificação do campo da PTO no Brasil e os desafios disso decorrentes.The great theoretical and methodological diversity of Work and Organizational Psychology (WOP) approaches in Brazil reflects the presence of distinct scientific paradigms in the setting of boundaries and the organization of this field. The purpose of this paper is to analyze these paradigms and relate them with three WOP thematic streams in Brazil: the behavioral stream; the subjectivity stream; and the clinical stream. We investigate epistemological and methodological fundamentals, some studies and authors in each of these streams, discussing their contribution to the field of WOP in Brazil. The paper discusses the stresses that exist among these streams, which arise from the pressure of corresponding at once to academic rigor and organizational relevance criteria. Finally, the article shows the diversification of the field of WOP in Brazil and resulting challenges

Model-Independent Quantum Phases Classifier

Machine learning has revolutionized many fields of science and technology. Through the $k$-Nearest Neighbors algorithm, we develop a model-independent classifier, where the algorithm can classify phases of a model to which it has never had access. For this, we study three distinct spin-$1$ models with some common phases: the XXZ chains with uniaxial single-ion-type anisotropy, the bound alternating XXZ chains, and the bilinear biquadratic chain. We show that, with high probability, algorithms trained with two of these models can determine common phases with the third. It is the first step toward a universal classifier, where an algorithm is able to detect any phase with no knowledge about the Hamiltonian, only knowing partial information about the quantum state

European cancer mortality predictions for the year 2012

Background: Estimating current cancer mortality figures is important for defining priorities for prevention and treatment. Materials and methods: Using logarithmic Poisson count data joinpoint models on mortality and population data from the World Health Organization database, we estimated numbers of deaths and age-standardized rates in 2012 from all cancers and selected cancer sites for the whole European Union (EU) and its six more populated countries. Results: Cancer deaths in the EU in 2012 are estimated to be 1 283 101 (717 398 men and 565 703 women) corresponding to standardized overall cancer death rates of 139/100 000 men and 85/100 000 women. The fall from 2007 was 10% in men and 7% in women. In men, declines are predicted for stomach (−20%), leukemias (−11%), lung and prostate (−10%) and colorectal (−7%) cancers, and for stomach (−23%), leukemias (−12%), uterus and colorectum (−11%) and breast (−9%) in women. Almost stable rates are expected for pancreatic cancer (+2-3%) and increases for female lung cancer (+7%). Younger women show the greatest falls in breast cancer mortality rates in the EU (−17%), and declines are expected in all individual countries, except Poland. Conclusion: Apart for lung cancer in women and pancreatic cancer, continuing falls are expected in mortality from major cancers in the E

Critical Behaviour of Mixed Heisenberg Chains

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.Ge

Trends in cancer mortality in the Americas, 1970-2000

Background: Data and statistics on cancer mortality over the last decades are available for most developed countries, while they are more difficult to obtain, in a standardized and comparable format, for countries of Latin America. Patients and methods: Age standardized (world population) mortality rates around the year 2000, derived from the WHO database, are presented for 14 selected cancers and total cancer in 10 countries of Latin America, plus, for comparative purposes, Canada and the USA. Trends in mortality are also given over the period 1970-2000. Results: In 2000, the highest total cancer mortality for males was observed in Argentina and Chile, with rates comparable to those of Canada and the USA, i.e. about 155/100 000. For women, Chile and Cuba had the highest rates in Latin America (114 and 103/100 000, respectively), again comparable to those of North America (around 105/100 000). These reflect the comparatively high mortality from cancer of the stomach (for Chile), lung and intestines (for Argentina) in men, and of stomach and uterus (for Chile), intestines and lung (for Cuba) in women. Colombia, Ecuador and Mexico had the lowest total cancer mortality for men, due to low mortality from stomach, colorectal and lung cancer. For women, the lowest rates were in Brazil and Puerto Rico, reflecting their low stomach and cervical cancer rates. In Argentina, Chile, Colombia, Costa Rica and Venezuela cancer mortality rates tended to decline, particularly in men. Rates were stable in Ecuador and Puerto Rico, and were increasing in Mexico and Cuba. Conclusions: Mortality from some common cancers (including colorectal and lung) is still low in Latin America compared with Canada and the USA, and decreasing trends have been observed in the last decades for some cancer sites (including stomach, uterus, lung and other tobacco-related cancers) in several countries. However, mortality from female lung and breast cancers has been increasing in most countries of Latin America, and several countries still show an extremely elevated mortality from cancer of the cervix. Selected neoplasms amenable to treatment, including testis and leukemias, also show unsatisfactory trends in Latin Americ

Trends in cancer mortality in Mexico, 1970-1999

Background: Few data on cancer mortality have been published for Mexico over the last few decades. It is therefore of interest to conduct a systematic and updated analysis of cancer mortality in this country. Patients and methods: Age-standardised (world population) mortality rates, at all ages and truncated at age 35-64 years, from major cancers and all cancers combined were computed on the basis of certified deaths derived from the World Health Organization database for the period 1970-99. Results: Mortality rates for all neoplasms showed an upward trend in men of all ages (from 58.2/100 000 in 1970-74 to 87.1/100 000 in 1995-99) and in middle-aged men (from 76.1 to 93.7/100 000, respectively). This reflects the rise until the early 1990s in lung cancer mortality (from 8.1/100 000 in 1970-74 to 15.6/100 000 in 1995-99) and prostate cancer (from 5.5 to 12.2/100 000, respectively). In women, overall mortality rates showed an increase between the early 1970s (75.4/100 000) and the late 1990s (82.3/100 000). Total cancer mortality rates remained low, however, compared with other American countries (e.g. 153.3/100 000 men and 108.6/100 000 women in 1999 in the United States). Truncated rates were stable (126.5/100 000 in 1970-74 and 125.8/100 000 in 1995-99), although they were much higher than overall rates, reflecting exceedingly high rates for uterine (mostly cervical) cancer mortality in middle-aged women (29.5/100 000 in 1995-99). Conclusions: Total cancer mortality in Mexico has remained comparably low on a worldwide scale, and the upward trends in mortality rates for lung and other tobacco-related neoplasms have tended to level off over the last decade. However, steady rises have been observed for other major cancers, including prostate and breast. Cervical cancer remains a major health problem in wome

Epidemiology of biliary tract cancers: an update

Background: Biliary tract cancer (BTC) is a rare cancer in Europe and North America, characterized by wide geographic variation, with high incidence in some areas of Latin America and Asia. Materials and methods: BTC mortality and incidence have been updated according to recent data, using joinpoint regression analysis. Results: Since the 1980s, decreasing trends in BTC mortality rates (age-standardized, world standard population) were observed in the European Union as a whole, in Australia, Canada, Hong Kong, Israel, New Zealand, and the United States, and high-risk countries such as Japan and Venezuela. Joinpoint regression analysis indicates that decreasing trends were more favorable over recent calendar periods. High-mortality rates are, however, still evident in central and eastern Europe (4-5/100 000 women), Japan (4/100 000 women), and Chile (16.6/100 000 women). Incidence rates identified other high-risk areas in India (8.5/100 000 women), Korea (5.6/100 000 women), and Shanghai, China (5.2/100 000 women). Conclusions: The decreasing BTC mortality trends essentially reflect more widespread and earlier adoption of cholecystectomy in several countries, since gallstones are the major risk factor for BTC. There are, however, high-risk areas, mainly from South America and India, where access to gall-bladder surgery remains inadequat