Two repelling random walks on Z\mathbb Z

We consider two interacting random walks on $\mathbb{Z}$ such that the transition probability of one walk in one direction decreases exponentially with the number of transitions of the other walk in that direction. The joint process may thus be seen as two random walks reinforced to repel each other. The strength of the repulsion is further modulated in our model by a parameter $\beta \geq 0$. When $\beta = 0$ both processes are independent symmetric random walks on $\mathbb{Z}$, and hence recurrent. We show that both random walks are further recurrent if $\beta \in (0,1]$. We also show that these processes are transient and diverge in opposite directions if $\beta > 2$. The case $\beta \in (1,2]$ remains widely open. Our results are obtained by considering the dynamical system approach to stochastic approximations.Comment: 17 pages. Added references and corrected typos. Revised the argument for the convergence to equilibria of the vector field. Improved the proof for the recurrence when beta belongs to (0,1); leading to the removal of a previous conjectur

Strategic configurations and performance: a study in micro and small business retailers

Um conjunto expressivo de estudos advogam a interdependência e complementariedade entre variáveis ambientais, estruturais, estratégicas e pessoais do estrategista na formação da estratégia. São raros os levantamentos que associam essas variáveis com desempenho de empresas de pequeno porte. Conjugando variáveis nessas dimensões, a pesquisa aqui apresentada objetivou verificar quais configurações estratégicas compostas pelo processo de desenvolvimento da estratégia, conteúdo da estratégia, atitude empreendedora, modo administrativo e incerteza ambiental percebida associaram-se ao desempenho de empresas de pequeno porte do varejo de vestuário. Dados levantados em survey com 228 empresas e investigados pela técnica de análise de clusters, revelaram dois grupos/clusters de empresas com configurações e níveis de desempenho distintos. Os resultados indicam a relação de interdependência de variáveis na explanação da heterogeneidade do desempenho organizacional.A significant number of studies advocate the interdependence and complementarity between environmental, structural, strategic and personal variables in strategy formation. There are rare surveys that link these variables with small businesses performance. Combining several dimensions of these variables, this study aimed to verify which strategy configurations composed by the strategy development process, strategy content, entrepreneurial attitude, administrative mode and perceived environmental uncertainty were associated with the performance of small-sized clothing retail businesses. Data collected by survey with 228 companies and investigated by cluster analysis technique revealed two groups/clusters of companies with different configurations and performance levels. The results indicate the relationship of interdependence among variables in explaining the heterogeneity of organizational performance

Orthodontic and orthopaedic treatment for anterior open bite in children (Review)

Background: Anterior open bite occurs when there is a lack of vertical overlap of the upper and lower incisors. The aetiology is multifactorial including: oral habits, unfavourable growth patterns, enlarged lymphatic tissue with mouth breathing. Several treatments have been proposed to correct this malocclusion, but interventions are not supported by strong scientific evidence. Objectives: The aim of this systematic review was to evaluate orthodontic and orthopaedic treatments to correct anterior open bite in children. Search methods: The following databases were searched: the Cochrane Oral Health Group's Trials Register (to 14 February 2014); the Cochrane Central Register of Controlled Trials (CENTRAL)(The Cochrane Library 2014, Issue 1); MEDLINE via OVID (1946 to 14 February 2014); EMBASE via OVID (1980 to 14 February 2014); LILACS via BIREME Virtual Health Library (1982 to 14 February 2014); BBO via BIREME Virtual Health Library (1980 to 14 February 2014); and SciELO (1997 to 14 February 2014). We searched for ongoing trials via ClinicalTrials.gov (to 14 February 2014). Chinese journals were handsearched and the bibliographies of papers were retrieved. Selection criteria: All randomised or quasi-randomised controlled trials of orthodontic or orthopaedic treatments or both to correct anterior open bite in children. Data collection and analysis: Two review authors independently assessed the eligibility of all reports identified. Risk ratios (RRs) and corresponding 95% confidence intervals (CIs) were calculated for dichotomous data. The continuous data were expressed as described by the author. Main results: Three randomised controlled trials were included comparing: effects of Frankel's function regulator-4 (FR-4) with lip-seal training versus no treatment; repelling-magnet splints versus bite-blocks; and palatal crib associated with high-pull chincup versus no treatment.The study comparing repelling-magnet splints versus bite-blocks could not be analysed because the authors interrupted the treatment earlier than planned due to side effects in four of ten patients.FR-4 associated with lip-seal training (RR = 0.02 (95% CI 0.00 to 0.38)) and removable palatal crib associated with high-pull chincup (RR = 0.23 (95% CI 0.11 to 0.48)) were able to correct anterior open bite.No study described: randomisation process, sample size calculation, there was not blinding in the cephalometric analysis and the two studies evaluated two interventions at the same time. These results should be therefore viewed with caution. Authors' conclusions: There is weak evidence that the interventions FR-4 with lip-seal training and palatal crib associated with high-pull chincup are able to correct anterior open bite. Given that the trials included have potential bias, these results must be viewed with caution. Recommendations for clinical practice cannot be made based only on the results of these trials. More randomised controlled trials are needed to elucidate the interventions for treating anterior open bite

Jean-Baptiste Debret

FINEPUFRJFUJBIBEPFAPERJME

O Brasil e o colonialismo europeu

FINEPUFRJFUJBIBEPFAPERJME

Impact of perineural invasion on the outcome of patients with synchronous colorectal liver metastases treated with neoadjuvant chemotherapy and surgery

Purpose: To analyze the prognostic value of variables of the primary tumor in patients with synchronous liver metastases in colorectal cancer (CLRMs) treated with neoadjuvant chemotherapy and surgery. Methods/patients: From a prospective database, we retrospectively identified all patients with synchronous CLRMs who were treated with neoadjuvant chemotherapy and liver resection. Using univariate and multivariate analyses, we identified the variables associated with tumor recurrence. Overall survival and disease-free survival were calculated using the Kaplan-Meier method with differences determined by the Cox multiple hazards model. Results were compared using the log-rank test. Results: Ninety-eight patients with synchronous CLRMs were identified. With a median follow-up of 39.8 months, overall survival and disease-free survival at 5 and 10 years were 53%, 41.7%, 29% and 29%, respectively. Univariate analysis identified three variables associated with tumor recurrence: location in the colon (p = 0.025), lymphovascular invasion (p = 0.011) and perineural invasion (p = 0.005). Multivariate analysis identified two variables associated with worse overall survival: perineural invasion (HR 2.36, 95% CI 1.162-4.818, p = 0.018) and performing frontline colectomy (HR 3.286, 95% CI 1.256-8.597, p = 0.015). Perineural invasion remained as the only variable associated with lower disease-free survival (HR 1.867, 95% CI 1.013-3.441, p = 0.045). Overall survival at 5 and 10 years in patients with and without perineural invasion was 68.2%, 54.4% and 29.9% and 21.3%, respectively (HR 5.920, 95% CI 2.241-15.630, p < 0.001). Conclusions: Perineural invasion in the primary tumor is the variable with most impact on survival in patients with synchronous CLRMs treated with neoadjuvant chemotherapy and surgery

Antimicrobial activity of bacterial nanocellulose modified with chestnut extract

Chestnut wood extracts are rich in tannins that exhibit numerous health-promoting properties. The incorporation of 5% (w/v) chestnut extract within the nanofibrous structure of bacterial nanocellulose (BNC) produced by Gluconacetobacter hansenii ATCC 53582 was obtained through exhaustion. This simple processing methodology resulted in a flexible (upon addition of 2% (w/v) glycerol), biodegradable, biocompatible nanocomposite for potential application in medical appliances.Portuguese Foundation for Science and Technology (FCT), FEDER funds through Portugal 2020 Competitive Factors Operational Program (POCI), and thePortuguese Government (PG) for the projects: UID/CTM/00264/2021 of Centre for Textil e Science and Technology (2C2T) and PTDC/CTM-TEX/1213/2020;FCT, the Ministry of Science, Technology and Higher Education (MCTES), the European Social Fund (FSE) and the European Union (UE)for her Ph.D. funding via scholarship 2020.04919.BD;FCT, FEDER, POCI, and PG for her research grant POCI-01-0247-ERDF-047124