Perturbaciones singulares de problemas de contorno para sistemas acoplados de ecuaciones en diferencias de segundo orden

En este articulo presentamos un método de perturbaciones singulares para problemas de contorno relacionados con sistemas acoplados de ecuaciones en diferencias de segundo orden con coeficientes variables involucrando un parámetro pequeño E. Estudiamos el comportamiento asintótico de la solución cuando E tiende a cero.In this paper singular perturbations for coupled second order boundary value difference systems with a small parameter E are treated. The asymptotic behavior of the solution when E approaches zero is studied.Peer Reviewe

Solución de problemas de contorno para ecuaciones en diferencias matriciales de segundo orden

En este articulo se estudian condiciones de existencia de solución de problemas de contorno para ecuaciones matriciales de segundo orden. Mediante la solución de una ecuación algebraica inatricial asociada al problema de contorno, obtenemos una expresión de la solución general del problema, computable en términos de los datos y sin aumentar la dimensión del problema.In this paper boundary value problems for second order matrix difference equations are considered. Existente conditions for the solutions of the problem as well as an explicit expression of the general solution of the problem, are given in terms of a solution of an algebraic matrix equation related to the problem. Our method provides an expression of the solutions of the problem avoiding the increase of the dimension of the problem.Peer Reviewe

Perturbaciones singulares de problemas de contorno para sistemas acoplados de ecuaciones en diferencias de segundo orden

En este articulo presentamos un método de perturbaciones singulares para problemas de contorno relacionados con sistemas acoplados de ecuaciones en diferencias de segundo orden con coeficientes variables involucrando un parámetro pequeño E. Estudiamos el comportamiento asintótico de la solución cuando E tiende a cero.In this paper singular perturbations for coupled second order boundary value difference systems with a small parameter E are treated. The asymptotic behavior of the solution when E approaches zero is studied.Peer Reviewe

Solución de problemas de contorno para ecuaciones en diferencias matriciales de segundo orden

En este articulo se estudian condiciones de existencia de solución de problemas de contorno para ecuaciones matriciales de segundo orden. Mediante la solución de una ecuación algebraica inatricial asociada al problema de contorno, obtenemos una expresión de la solución general del problema, computable en términos de los datos y sin aumentar la dimensión del problema.In this paper boundary value problems for second order matrix difference equations are considered. Existente conditions for the solutions of the problem as well as an explicit expression of the general solution of the problem, are given in terms of a solution of an algebraic matrix equation related to the problem. Our method provides an expression of the solutions of the problem avoiding the increase of the dimension of the problem.Peer Reviewe

Expression of p53 Protein and Tumor Angiogenesis as Prognostic Factors in Nasopharyngeal Carcinoma Patients.

The objective of this study was to evaluate the possible prognostic significance of p53 protein overexpression and tumor angiogenesis (TA) in nasopharyngeal carcinoma (NPC) patients, together with other clinicopathological variables. Forty-two NPC patients were evaluated in relation to survival. Nuclear p53 overexpression in neoplastic and endothelial cells was detected by immunohistochemistry (IHC) with the monoclonal antibody DO-7 and the polyclonal antibody against factor VIII-related antigen, respectively. Thereafter, we evaluated p53 cases in order to determine their nuclear immunoreactivity from negative (-) to positive (+, ++, +++). In addition, microvessels were counted in the most active areas of tumor neovascularization or hotspots using an image computer analyzer (MicroImage®). A Cox multiple regression survival analysis was used to determine the best prognostic indicators in NPC patients. As a result, tumor microvessel count, considered as a continuous variable, was the most important independent prognostic indicator in relation to survival (p = 0.0273), with a relative risk of death of 2,4399 [95% confidence interval = 1.1051 ; 5.3871] associated with the highest microvessel counts. Moreover, the only clinicopathological variable that demonstrated prognostic value in a Cox multiple regression survival analysis was histological type (p = 0.05). In addition, we did not observe any statistical association between intratumoral microvessel density (IMD), clinicopathological variables and p53 protein expression. Key words: p53 protein - Angiogenesis - Morphometry - Prognosis - Nasopharyngeal carcinom

Handgrip strength and work limitations:A prospective cohort study of 70,820 adults aged 50 and older

The purpose of the study was to investigate the association between handgrip strength and the incidence of work limitations in European adults aged 50 and older. We conducted a prospective cohort study among adults aged 50 and older from 27 European countries and Israel. Data were collected from the Survey of Health, Ageing and Retirement in Europe (SHARE) waves 1, 2, 4, 5, 6, and 7. Handgrip strength was measured using a hand dynamometer (Smedley, S Dynamometer, TTM) and participants replied to questions about work limitations. Cox regression was conducted for statistical analyses. A total of 70,820 older adults (mean age 61 ± 7.7 years; 54.3 % women) were followed during a mean of 3.8 ± 2.9 years. The fully adjusted model showed that participants with low handgrip strength (<16 kg in women and <27 kg in men) had a significantly higher risk of work limitations compared with participants with normal values of handgrip strength (hazard ratio: 1.36; 95 % confidence interval: 1.28–1.44). Kaplan-Meier trajectories revealed that the survival probability to experience work limitations in the normal handgrip category was 20 % lower than in the low handgrip category in most of the follow-up period. We identified low level of handgrip strength as a risk factor for work limitations in adults aged 50 years or older. This could be used as an accessible measure to screen workers at risk of developing work limitations

Understanding why women don’t choose engineering degrees

Despite the continuous efforts of governments and universities to avoid the underrepresentation of women entering engineering degrees, the trend has not reverted, and this is a general fact all over the world. This fact goes against the tendency of a growing ratio of women in tertiary education, so causes must be investigated. This research examines two main questions: Is it possible to break the invisible barriers that prevent girls from entering in engineering degrees by means of an engineering project or activity? And are there important misconceptions about the role of women in engineering professions and about engineering itself among high school girls? An extensive survey has been carried out between three groups of students: students of the last years of high school (834), students of the first year of engineering degrees (319), and students of the first year of sciences degrees (209). A set of visits to the high schools was developed and a contest of engineering projects was carried out too. The results show that there are important misconceptions in the knowledge that high school students have about engineering degrees and engineering. The visits and the project contest had a good impact that encouraged girls to take engineering activities in their curricula. The main finding is that even though girls see engineering professions as very well valued, they are convinced that engineering is not a profession for women, which suggests that there are educational barriers acquired during earlier stages of their lives

Importance of frequency and intensity of strength training for work ability among physical therapists

The aim of the study was to evaluate the association between frequency and intensity of strength training participation and work ability among physical therapists (PTs). The Work Ability Index questionnaire (WAI) and a questionnaire about participation in strength training during leisure time were administered to a sample of Spanish PTs. In addition, participants provided information on gender, age, body mass index, education, substance use, working experience and working hours per week. The odds for having excellent WAI (score 44–49) as a function of intensity or frequency of strength training participation were determined using binary logistic regression controlled for various confounders. Data from 981 PTs were analysed. High-intensity strength training (&gt; 80% 1 RM) showed strong associations with excellent WAI (odds ratio = 9.7; 95% confidence interval, 2.9–31.6). In addition, performing strength training more than 3 times per week was associated with excellent WAI (odds ratio = 1.79; 95% confidence interval, 1.24–2.59), however, no significant associations were found with lower levels of frequency and intensities. High-intensity strength training 3 times per week is associated with excellent WAI among PTs. Training programs meeting these features may importantly contribute to maintain or improve WAI

Mortality risk estimation in acute calculous cholecystitis : beyond the Tokyo Guidelines

Acute calculous cholecystitis (ACC) is the second most frequent surgical condition in emergency departments. The recommended treatment is the early laparoscopic cholecystectomy; however, the Tokyo Guidelines (TG) advocate for different initial treatments in some subgroups of patients without a strong evidence that all patients will benefit from them. There is no clear consensus in the literature about who is the unfit patient for surgical treatment. The primary aim of the study is to identify the risk factors for mortality in ACC and compare them with Tokyo Guidelines (TG) classification. Retrospective unicentric cohort study of patients emergently admitted with and ACC during 1 January 2011 to 31 December 2016. The study comprised 963 patients. Primary outcome was the mortality after the diagnosis. A propensity score method was used to avoid confounding factors comparing surgical treatment and non-surgical treatment. The overall mortality was 3.6%. Mortality was associated with older age (68 IQR 27 vs. 83 IQR 5.5; P = 0.001) and higher Charlson Comorbidity Index (3.5 5.3 vs. 02; P = 0.001). A logistic regression model isolated four mortality risk factors (ACME): chronic obstructive pulmonary disease (OR 4.66 95% CI 1.7-12.8 P = 0.001), dementia (OR 4.12; 95% CI 1.34-12.7, P = 0.001), age 80 years (OR 1.12: 95% CI 1.02-1.21, P = 0.001) and the need of preoperative vasoactive amines (OR 9.9: 95% CI 3.5-28.3, P = 0.001) which predicted the mortality in a 92% of the patients. The receiver operating characteristic curve yielded an area of 88% significantly higher that 68% (P = 0.003) from the TG classification. When comparing subgroups selected using propensity score matching with the same morbidity and severity of ACC, mortality was higher in the non-surgical treatment group. (26.2% vs. 10.5%). Mortality was higher in ACC patients treated with non-surgical treatment. ACME identifies high-risk patients. The validation to ACME with a prospective multicenter study population could allow us to create a new alternative guideline to TG for treating ACC. Retrospectively registered and recorded in Clinical Trials