Phase separation versus supersolid behavior in frustrated antiferromagnets

We investigate the competition between spin-supersolidity and phase separation in a frustrated spin-half model of weakly coupled dimers. We start by considering systems of hard-core bosons on the square lattice, onto which the low-energy physics of the herein investigated spin model can be mapped, and devise a criterion for gauging the interplay between supersolid order and domain wall formation based on strong coupling arguments. Effective bosonic models for the spin model are derived via the contractor renormalization (CORE) algorithm and we propose to combine a self-consistent cluster mean-field solution with our criterion for the occurrence of phase separation to derive the phase diagram as a function of frustration and magnetic field. In the limit of strong frustration, the model is shown to be unstable toward phase separation, in contradiction with recently published results. However, a region of stable supersolidity is identified for intermediate frustration, in a parameter range not investigated so far and of possible experimental relevance.Comment: 8 pages, 7 figures. Published versio

Sugestão de palavras chave para campanhas em motores de busca em arranque

As campanhas de publicidade online sobre pesquisas em motores de busca têm um grande peso nas receitas das empresas de marketing digital. Cada campanha é definida por um conjunto de palavras chave que são utilizadas pelo motor de busca para escolher a melhor publicidade candidata a apresentar juntamente com os resultados da pesquisa. Um problema com que se deparam estas campanhas é a da sugestão das melhores palavras chave para uma determinada campanha. Neste artigo é apresentado um modelo para a análise de relações entre variáveis de campanhas de publicidade, bem como um algoritmo para produzir sugestões de palavras chave. Uma vez que este algoritmo se baseia no histórico da campanha, não é aplicável a campanhas em arranque que não têm histórico. Este artigo apresenta também uma abordagem baseada no histórico de campanhas semelhantes e que permite ultrapassar esta dificuldade. Finalmente é apresentada uma caracterização estatística do histórico de campanhas AdWords reais e da relação entre estas campanhas

Daylighting : guidelines for room depth limits in the technical regulation for energy efficiency labelling of residential buildings

iluminação natural, além de ser importante recurso para promover bem-estar e qualidade ambiental, tem impacto relevante na redução do uso de energia. O Regulamento Técnico da Qualidade do Nível de Eficiência Energética de Edifícios Residenciais (RTQ-R) foi publicado no Brasil em agosto de 2010, dando sequência ao Programa Brasileiro de Etiquetagem do Inmetro voltado para edificações. Com relação a aspectos bioclimáticos da arquitetura dos edifícios, tais como iluminação natural, buscou-se desenvolver alguns pré-requisitos e bonificações para os ambientes, de forma que esses aspectos fossem considerados na avaliação de edificações residenciais. Neste artigo, apresentam-se o método e os resultados que geraram as indicações relativas à bonificação de iluminação natural presentes no Regulamento. O método utilizado incluiu 336 simulações computacionais dinâmicas com o software DaySim, com o objetivo de investigar a influência de variáveis arquitetônicas no desempenho da iluminação natural, mais especificamente a profundidade dos ambientes e as proteções solares. As simulações foram realizadas para 11 cidades brasileiras, abarcando 11 diferentes latitudes e 4 zonas bioclimáticas (ZB 1 , ZB 3, ZB 4 e ZB 4). Os resultados geraram indicações sobre a profundidade-limite de ambientes, que foram adotadas como parâmetros para concessão da bonificação de iluminação natural no RTQ-R. ______________________________________________________________________________________ ABSTRACTquality, and has also a significant impact on energy use. The Technical Regulations for Energy Efficiency Labeling of Residential Buildings (RTQ-R) was published in Brazil in August 2010, as a part of INMETRO’s Brazilian Labeling Program. Concerning aspects of bioclimatic architecture such as daylight, some prerequisites and bonus were developed to be considered in the evaluation of residential buildings. This article presents the method and the results that produced the indications related to the daylight bonus that are established in that Regulation. The method included 336 computer simulations using the software DaySim, in order to investigate the variables that influence daylight performance, specifically regarding room depth and solar protection. The simulations were performed for 11 Brazilian cities, covering 11 different geographical latitudes and four bioclimatic zones (ZB 1, ZB 3, ZB 4 and ZB 11). The results generated guidelines on room depth limits, which were adopted as parameters for granting daylight bonus in the RTQ-R regulations

Learning and memory with neuropathic pain: impact of old age and progranulin deficiency

Persistent neuropathic pain is a frequent consequence of peripheral nerve injuries, particularly in the elderly. Using the IntelliCage we studied if sciatic nerve injury obstructed learning and memory in young and aged mice, each in wild type and progranulin deficient mice, which develop premature signs of brain aging. Both young and aged mice developed long-term nerve injury-evoked hyperalgesia and allodynia. In both genotypes, aged mice with neuropathic pain showed high error rates in place avoidance acquisition tasks. However, once learnt, these aged mice with neuropathic pain showed a significantly stronger maintenance of the aversive memory. Nerve injury did not affect place preference behavior in neither genotype, neither in young nor aged mice. However, nerve injury in progranulin deficient mice impaired the learning of spatial sequences of awarded places, particularly in the aged mice. This task required a discrimination of clockwise and anti-clockwise sequences. The chaining failure occurred only in progranulin deficient mice after nerve injury, but not in sham operated or wildtype mice, suggesting that progranulin was particularly important for compensatory adaptations after nerve injury. In contrast, all aged mice with neuropathic pain, irrespective of the genotype, had a long maintenance of aversive memory suggesting a negative alliance and possibly mutual aggravation of chronic neuropathic pain and aversive memory at old age

Effects of the construction method on pile performance: Evaluation by instrumentation. part 2: Experimental site at the faculty of engineering of the University of Porto

Three different types of piles (bored, CFA and precast driven) were installed in the experimental site located in the Campus of the Faculty of Engineering of the University of Porto to study the effects of the construction method on pile performance. The subsoil is a residual granitic soil reaching depth levels over 20 m. In this site, several field and laboratory tests were conducted to obtain the local geotechnical parameters. Static pile load tests with load-unload cycles were performed. Bored and CFA piles were instrumented along the depth, with installation of retrievable sensors; a flat-jack load cell was inserted at the bottom of the bored pile. Load tests results demonstrated that bored and CFA piles show similar behavior: i) the applied load reaching the pile tip was about 42%, ii) and the average mobilized lateral resistance was about 60 kPa. After the tests were completed, piles were extracted for further inspection of shaft and load cell conditions. The driven pile although having a smaller cross-section showed a stiffer response and higher resistance than the other two piles, which are a clear indication that the installation effects play an important role in the pile response. The results are compared to those obtained in Part 1 of this article relating to tests performed at the Experimental Field of Unicamp (State University of Campinas)

Fat Fisher Zeroes

We show that it is possible to determine the locus of Fisher zeroes in the thermodynamic limit for the Ising model on planar (``fat'') phi4 random graphs and their dual quadrangulations by matching up the real part of the high and low temperature branches of the expression for the free energy. The form of this expression for the free energy also means that series expansion results for the zeroes may be obtained with rather less effort than might appear necessary at first sight by simply reverting the series expansion of a function g(z) which appears in the solution and taking a logarithm. Unlike regular 2D lattices where numerous unphysical critical points exist with non-standard exponents, the Ising model on planar phi4 graphs displays only the physical transition at c = exp (- 2 beta) = 1/4 and a mirror transition at c=-1/4 both with KPZ/DDK exponents (alpha = -1, beta = 1/2, gamma = 2). The relation between the phi4 locus and that of the dual quadrangulations is akin to that between the (regular) triangular and honeycomb lattices since there is no self-duality.Comment: 12 pages + 6 eps figure

Determinants of the Sympatric Host-Pathogen Relationship in Tuberculosis

Major contributions from pathogen genome analysis and host genetics have equated the possibility of Mycobacterium tuberculosis co-evolution with its human host leading to more stable sympatric host-pathogen relationships. However, the attribution to either sympatric or allopatric categories depends on the resolution or grain of genotypic characterization. We explored the influence on the sympatric host-pathogen relationship of clinical (HIV infection and multidrug-resistant tuberculosis [MDRTB]) and demographic (gender and age) factors in regards to the genotypic grain by using spacer oligonucleotide typing (spoligotyping) for classification of M. tuberculosis strains within the Euro-American lineage. We analyzed a total of 547 tuberculosis (TB) cases, from six year consecutive sampling in a setting with high TB-HIV coinfection (32.0%). Of these, 62.0% were caused by major circulating pathogen genotypes. The sympatric relationship was defined according to spoligotype in comparison to the international spoligotype database SpolDB4. While no significant association with Euro-American lineage was observed with any of the factors analyzed, increasing the resolution with spoligotyping evidenced a significant association of MDRTB with sympatric strains, regardless of the HIV status. Furthermore, distribution curves of the prevalence of sympatric and allopatric TB in relation to patients' age showed an accentuation of the relevance of the age of onset in the allopatric relationship, as reflected in the trimodal distribution. On the contrary, sympatric TB was characterized by the tendency towards a typical (standard) distribution curve. Our results suggest that within the Euro-American lineage a greater degree of genotyping fine-tuning is necessary in modeling the biological processes behind the host-pathogen interplay. Furthermore, prevalence distribution of sympatric TB to age was suggestive of host genetic determinisms driven by more common variants.Luso-American Development Foundation: (LACR Award program - 2007), European Community fund: (FEDER)

Beclin 1 mitigates motor and neuropathological deficits in genetic mouse models of Machado-Joseph disease

Machado-Joseph disease or spinocerebellar ataxia type 3, the most common dominantly-inherited spinocerebellar ataxia, results from translation of the polyglutamine-expanded and aggregation prone ataxin 3 protein. Clinical manifestations include cerebellar ataxia and pyramidal signs and there is no therapy to delay disease progression. Beclin 1, an autophagy-related protein and essential gene for cell survival, is decreased in several neurodegenerative disorders. This study aimed at evaluating if lentiviral-mediated beclin 1 overexpression would rescue motor and neuropathological impairments when administered to pre- and post-symptomatic lentiviral-based and transgenic mouse models of Machado-Joseph disease. Beclin 1-mediated significant improvements in motor coordination, balance and gait with beclin 1-treated mice equilibrating longer periods in the Rotarod and presenting longer and narrower footprints. Furthermore, in agreement with the improvements observed in motor function beclin 1 overexpression prevented neuronal dysfunction and neurodegeneration, decreasing formation of polyglutamine-expanded aggregates, preserving Purkinje cell arborization and immunoreactivity for neuronal markers. These data show that overexpression of beclin 1 in the mouse cerebellum is able to rescue and hinder the progression of motor deficits when administered to pre- and post-symptomatic stages of the diseas

Resonant Photonic Quasicrystalline and Aperiodic Structures

We have theoretically studied propagation of exciton-polaritons in deterministic aperiodic multiple-quantum-well structures, particularly, in the Fibonacci and Thue-Morse chains. The attention is concentrated on the structures tuned to the resonant Bragg condition with two-dimensional quantum-well exciton. The superradiant or photonic-quasicrystal regimes are realized in these structures depending on the number of the wells. The developed theory based on the two-wave approximation allows one to describe analytically the exact transfer-matrix computations for transmittance and reflectance spectra in the whole frequency range except for a narrow region near the exciton resonance. In this region the optical spectra and the exciton-polariton dispersion demonstrate scaling invariance and self-similarity which can be interpreted in terms of the ``band-edge'' cycle of the trace map, in the case of Fibonacci structures, and in terms of zero reflection frequencies, in the case of Thue-Morse structures.Comment: 13 pages, 9 figures, submitted to Phys. Rev.

Observation of the Decay KL→μ+μ−γγK_L\to \mu^+\mu^- \gamma \gamma

We have observed the decay $K_L\to \mu^+\mu^- \gamma \gamma$ at the KTeV experiment at Fermilab. This decay presents a formidable background to the search for new physics in $K_L\to\pi^0\mu^+\mu^-$. The 1997 data yielded a sample of 4 signal events, with an expected background of 0.155 $\pm$ 0.081 events. The branching ratio is ${\mathcal B}(K_L\to \mu^+\mu^- \gamma \gamma$) $= (10.4^{+7.5}_{-5.9} {\rm (stat)} \pm 0.7 {\rm (sys)})\times 10^{-9}$ with $m_{\gamma\gamma} \geq 1 {\rm MeV/c}^2$, consistent with a QED calculation which predicts $(9.1\pm 0.8)\times 10^{-9}$.Comment: See also the paper "Search for the Decay $K_L \to \pi^0 \mu^+ \mu^-$", also by the KTeV collaboratio