Fold-Saddle Bifurcation in Non-Smooth Vector Fields on the Plane

This paper presents results concerning bifurcations of 2D piecewise-smooth dynamical systems governed by vector fields. Generic three parameter families of a class of Non-Smooth Vector Fields are studied and its bifurcation diagrams are exhibited. Our main result describes the unfolding of the so called Fold-Saddle singularity

Modelling competing risks in nephrology research: an example in peritoneal dialysis

BACKGROUND: Modelling competing risks is an essential issue in Nephrology Research. In peritoneal dialysis studies, sometimes inappropriate methods (i.e. Kaplan-Meier method) have been used to estimate probabilities for an event of interest in the presence of competing risks. In this situation a competing risk analysis should be preferable. The objectives of this study are to describe the bias resulting from the application of standard survival analysis to estimate peritonitis-free patient survival and to provide alternative statistical approaches taking competing risks into account. METHODS: The sample comprises patients included in a university hospital peritoneal dialysis program between October 1985 and June 2011 (n = 449). Cumulative incidence function and competing risk regression models based on cause-specific and subdistribution hazards were discussed. RESULTS: The probability of occurrence of the first peritonitis is wrongly overestimated using Kaplan-Meier method. The cause-specific hazard model showed that factors associated with shorter time to first peritonitis were age (>=55 years) and previous treatment (haemodialysis). Taking competing risks into account in the subdistribution hazard model, age remained significant while gender (female) but not previous treatment was identified as a factor associated with a higher probability of first peritonitis event. CONCLUSIONS: In the presence of competing risks outcomes, Kaplan-Meier estimates are biased as they overestimated the probability of the occurrence of an event of interest. Methods which take competing risks into account provide unbiased estimates of cumulative incidence for each specific outcome experienced by patients. Multivariable regression models such as those based on cause-specific hazard and on subdistribution hazard should be used in this competing risk setting

Peritoneal dialysis dropouts in different age and era cohorts: focus on the elderly

Introduction and Aims: Peritoneal dialysis (PD) is an efficient renal replacement therapy (RRT), but still remains underutilized at any age. Clinicians fear the rate of dropouts and lower technique survival, particularly in elderly patients. The authors aimed to explore such outcomes over the past 3 decades, in different age and era cohorts. Methods: Consecutive incident patients starting PD were identified from an ongoing registry-base prospective study of quality assessment. In order to control for an era effect, patients were assigned to 6 cohorts (5 years interval) according to the admission year between 1985 and 2014. Regression models taking competing risks into account were performed to identify potential prognostic factors for death and transfer to haemodialysis (HD) (adjusted for age, gender, diabetes, cohort era, automated peritoneal dialysis (APD) use, and first treatment modality – PD first, PD after HD, PD after renal transplant (RT). Then the patients were studied according to age at enrolment in the programme: A (18 44 years; n = 193); B (45 64 years; n = 176) and C (≥ 65 years old; n = 75). The HD transfer rates using Poisson analysis were evaluated. The incidence of dropout rates was compared at different times and between age groups, focusing particular attention on the elderly. Results: A total of 525 patients were evaluated: 211 male (40.2%), aged 48 ± 15.7 years old, on PD for 23 (IQR 9 – 41.5) months. The major cause of dropout technique was transfer to HD (35.4%), followed by renal transplantation (27.6%) and death (21.7%). The probability of technical failure and renal transplantation at 2 and 5 years was 19.2% and 18.1% and 34.2%; 27.4%, respectively. Probability of death at 2 and 5 years was 12.7%, and 21.8%, respectively. The contemporary cohort was associated with a lower risk of mortality and lower risk of transfer to haemodialysis, with greater access to renal transplantation. The regression model Fine & Gray showed that older age was associated with increased mortality, but was not associated with greater technical failure. Transfer to HD occurred in the elderly at a rate of 11epy/100 patient year (in comparison to 15 and 14 epy/100 patient-year in non-elderly groups A and B, respectively P= 0.33). The proportions of specific causes of technique failure did not change significantly according to age cohort. The dropout rates due to access-related-infection and ultrafiltration failure decreased in the elderly group in the more contemporary cohort, despite the differences were not statistically significant. Conclusions: The dropout by technique failure decreased significantly in the recent decade. Age at admission in peritoneal dialysis did not show to be a compromising factor of the technique survivalIntrodução e Objetivos: A diálise peritoneal (DP) é uma técnica substitutiva da função renal (TSFR) com eficácia semelhante à hemodiálise (HD); no entanto, ainda permanece subutilizada em qualquer idade. Os médicos temem o elevado drop-out da técnica e a sua menor sobrevida, particularmente nos doentes idosos. Os autores pretenderam explorar causas de drop-out e sobrevida da técnica ao longo das últimas três décadas, em diferentes faixas etárias, centrando uma atenção particular no idoso. Métodos: Foram usados dados do registo prospetivo do programa hospitalar de doentes adultos incidentes em DP. Tendo em conta as diferentes épocas, os doentes foram divididos em 6 coortes (5 anos de intervalo) de acordo com o ano de admissão no programa (1985-2014). Usaram-se modelos de regressão tendo em conta a análise de riscos competitivos para identificar potenciais fatores de prognóstico para a morte e transferência para HD (ajustados para a idade, género, diabetes, era, tipo de técnica e primeira modalidade de TSFR). Posteriormente, os doentes foram estudados de acordo com a idade à admissão no programa: A (18 44 anos); B (45 64 anos) e C (≥ 65 anos de idade). Foram avaliadas as taxas de transferência para HD usando a análise de Poisson. As taxas de incidência de drop-out foram comparadas em diferentes épocas e entre os grupos etários, focando particular atenção no doente idoso. Resultados: Foram avaliados 525 pacientes: 211 eram do sexo masculino (40,2%), com idade média de 48 ± 15,7 anos, com follow-up mediano de 23 meses (IQR 9-41,5). A maior causa de drop-out da técnica foi a transferência para HD (35,4%), seguida do transplante renal (27,6%) e de morte (21,7%). A probabilidade de falência técnica e transplantação renal aos 2 e aos 5 anos foi 19,2% e 18,1% e 34,2%; 27,4%, respetivamente. A probabilidade de morte aos 2 e aos 5 anos foi 12,7%, e 21,8%, respetivamente. A coorte mais recente associou-se a menor risco de mortalidade e menor transferência para HD. O modelo de regressão Fine & Gray mostrou que a idade avançada se associou a maior mortalidade, contudo não se associou a maior falência técnica. Nos idosos, a taxa de transferência para HD foi 11,2 episódios/100 doentes-ano (em comparação com 15 e 14 episódios/100 doentes-ano nos grupos A e B, respectivamente, p= 0,33). Não houve diferenças significativas nas causas de transferência para HD entre os diferentes grupos etários. As taxas de drop-out por falência de acessos e por falência de ultrafiltração diminuíram no grupo mais velho e na coorte mais recente, contudo as diferenças não foram estatisticamente significativas entre os grupos. Conclusões: O drop-out por falência técnica diminuiu significativamente na década mais recente. A idade de admissão na diálise peritoneal não mostrou ser um fator de comprometimento da sobrevida da técnic

Molecular diagnosis of Eimeria species affecting naturally infected Gallus gallus.

Abstract - We used PCR to test various protocols and define a technique for DNA extraction directly from chicken-shed stool samples for the identification of Eimeria species that parasitize birds. It was possible to extract and amplify DNA of seven Eimeria species from field stool samples, using both protocols tested; extractions made with phenol/chloroform protocols gave the best results. The primers were specific and sensitive, allowing amplification of samples containing as few as 20 oocysts, both in individual and in a multiplex PCR. Individualized PCR with the phenol/chloroform DNA extraction protocol detected a larger number of Eimeria species. Molecular diagnosis was found to be practical and precise, and can be used for monitoring and epidemiological studies of Eimeria

A psicopatologia geral na formagão do psicólogo

No presente artigo, o autor procura reflectir sobre a importância e a natureza do estudo de psicopatologia geral no curso de Psicologia. Após uma introdução breve, refere-se ao estado actual da Psicopatologia para, finalmente, reflectir sobre o que pode ser uma cadeira de Psicopatologia Geral aqui- -e-agora.ABSTRACT: In this paper, the author search a process of reflecting about the interest and nature of general psychopathology in Psychology curriculum. After an introduction, examine the state of the art in Psychopathology. Finally, the author, from his point of view, consider the chair of General Psychopathology where and now

Psicologia da Saúde Crítica: Breve revisão e perspectiva existencialista

A finalidade deste artigo é dupla: em primeiro lugar, fazer uma breve revisão da perspectiva crítica no campo da psicologia da saúde; em segundo lugar, discutir o seu potencial para a promoção da saúde e prevenção das doenças. Adicionalmente, apresenta-se o esboço de uma perspectiva existencialista em psicologia da saúde

A SIDA no feminino do plural : As mulheres e a infecção pelo VIH

Nesta nota didáctica identificam-se as questões específicas que a infecção pelo Vírus da Imunodeficência Humana (VIH) coloca às Mulheres, apontam- -se algumas áreas significativas para a investigação psicológica e introduzem-se aspectos que se consideram importantes para a prevenção.ABSTRACT: In this paper the author review women's issues in HIV infection and AiDS, pointing to the development of psychological research

Introdução à psicoterapia existencial

Neste artigo o autor introduz diferentes modalidades de psicoterapia existencial. Faz uma descrição breve das várias propostas terapêuticas, nomeadamente análise do Dasein, logoterapia, psicoterapia existencial humanista norte-americana, psicoterapia existencial de Laing, psicoterapia existencial britânica, psicoterapia existencial breve e psicoterapia existencial sartreana