Un grafo bipartito balanceado tiene la propiedad Pk si contiene un subgrafo bipartito balanceado completo de orden 2k, y una sucesión П= (Пx, Пy) es potencialmente Pk - bipartita gráfica si tiene una realización con la propiedad Pk· Sea σ(k, 2n) la menor suma de grados tal que toda sucesión bipartita gráfica П de 2n términos sin ceros y con suma de grados σ(П) ≥ σ(k, 2n) es potencialmente Pk - bipartita gráfica. En este artículo se conjetura que σ(k, 2n) = 2(k- 1)(2n- k)+ 2k, y se prueba que esto es cierto para k = 2 y 3.

The health crisis caused by the Coronavirus Disease 2019 o COVID-19 pandemic, increases its contagiousness, and leaves millions of deaths, as well as significant consequences in the psychic sphere of affected people. Lockdown, mandatory quarantine, and the actions taken to reduce the number of infections lead to negative consequences for the mental health of university students. Objective: To identify the relationship between academic stress and generalized anxiety disorder caused by the COVID-2019 pandemic. Material and Methods: Descriptive-correlational study, using the Cognitive Systemic Inventory of Academic Stress (CSIAS) and the Scale for Generalized Anxiety Disorder (GAD-7), applied to 359 university students of Ecuador during the period May-June 2020. Results: From the total sample, 64.9% were women and 35.1%, men, with 43.7% in the 21-23 years-old group. In the CSIAS, the mean s...