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Mamografía contrastada para la detección del cáncer de mama: una revisión sistemática
(2025-08) Hernández Blanco, Aracelly; Fonseca Alvarado, Jose Andrés
La mamografía con contraste ha emergido como una herramienta complementaria y eficaz en la evaluación diagnóstica del cáncer de mama, especialmente en mujeres con tejido mamario denso. Numerosos estudios han demostrado que ofrece una sensibilidad comparable a la resonancia magnética para la detección de cáncer de mama, con ventajas adicionales como menor costo, mayor accesibilidad, menor tiempo de adquisición y menor tasa de falsos positivos. También ha mostrado utilidad en la caracterización de microcalcificaciones, evaluación de lesiones palpables, respuesta al tratamiento neoadyuvante, y como técnica de detección secundaria en casos indeterminados o de alto riesgo. A pesar de implicar una dosis de radiación ligeramente mayor que la mamografía digital convencional y el riesgo inherente al uso de contraste yodado, los eventos adversos graves son poco frecuentes. Su implementación es factible en la mayoría de los centros que ya cuentan con equipos de mamografía actualizados, lo cual la convierte en una opción rentable para el diagnóstico y tamizaje en poblaciones seleccionadas.
Design and performance of frames with intentionally eccentric braces
(2020-09) González Ureña, Andrés; Tremblay, Robert; Rogers, Colin A.
Concentrically Braced Frames (CBFs) with Hollow Structural Sections (HSSs) as the bracing members present significant shortcomings that pose limits to their convenience. Due to their inherently stiff nature, CBFs are usually constrained to low fundamental periods of vibration and, thus, high acceleration and force demands, which, in conjunction with the intrinsic overstrength that derives from the compression resistance controlling the dimensioning of the bracing members, results in high design forces for the capacity-protected components of the structure and its foundations. Furthermore, their ductility and energy dissipation capacity are hindered by the susceptibility of HSSs to low-cycle fatigue induced premature fracturing at the plastic hinge region after the onset of local buckling. To address these shortcomings of Conventional Concentric Braces (CCBs), researchers from Japan recently proposed the use of Braces with Intentional Eccentricity (BIEs). Being subject to both flexural and axial deformations under axial loading, BIEs are inherently less stiff than CCBs. Moreover, their axial stiffness can be adjusted by varying the eccentricity to obtain the desired frame response. Also, initiation of local buckling occurs at larger axial displacements because the strain demand is more evenly distributed over the brace length. However, BIEs are not well suited for standard force-based design procedures given that the force they develop varies continuously with their axial deformation, and that they attain their maximum capacity at large deformation values that depend on the eccentricity. For this reason, the use of BIEs compels the use of an alternative design approach that handles explicitly their particular response to loading. This article presents a Direct Displacement-Based Design (DDBD) procedure for the seismic design of Frames with Intentionally Eccentric Braces (FIEBs). The proposed procedure includes provisions aiming to control the performance of the structure when subjected to design level earthquakes and to minimize its damage under frequent earthquakes. The method is applied to prototype buildings of 4, 8 and 12 storeys, with square HSS bracing members, and considering two levels of target drift ratio. The structures are designed for a region of high seismic hazard and for a region of moderate seismic hazard, both within Canada. The performance of the so designed buildings is then evaluated through Non-Linear Response-History Analysis (NLRHA). The results show that the seismic performance of FIEBs is satisfactory and on par with the performance objectives incorporated in the procedure and those of the National Building Code of Canada. Furthermore, the resulting tonnage of the FIEB buildings is compared to that of traditional Moderately Ductile and Limited Ductility CBFs designed for identical conditions, showing that FIEBs may constitute an economically advantageous alternative to conventional CBFs, specially in the case of moderately tall buildings located in regions of high seismic hazard.
Contribution of columns in the seismic response of frames with intentionally eccentric braces
(2024-07) González Ureña, Andrés; Tremblay, Robert; Rogers, Colin A.
Recent research showcases the novel Frame with Intentionally Eccentric Braces (FIEB) as a promising steel seismic-force-resisting system (SFRS) with the potential of becoming a viable alternative to the Concentrically Braced Frame (CBF), offering an improved seismic performance. The direct control over the structure’s strength at the target displacement level provided by the adjustable brace eccentricity renders FIEBs well suited to performance-oriented design and reduces incidental overstrength, resulting in cost-effective solutions. Additionally, the large post-elastic stiffness and partial self-centring capabilities of Braces with Intentional Eccentricity (BIEs) grant FIEBs an enhanced structural stability and make them suitable for use as the SFRS of high-rise buildings. However, to advance FIEBs to an implementable state, further research is required to properly understand all relevant aspects of their response, such as the contribution of the columns and the influence of employing different bracing configurations. In CBFs, columns contribute to the stability of the structure during earthquakes by distributing drift demands over the height of the building through bending. Aiming to ensure the conditions for this mechanism, the CSA S16 standard requires that columns in moderately ductile (MD) and limited-ductility (LD) CBFs be continuous and of constant cross-section over at least two storeys and be designed to withstand bending moments in the plane of the frame of 20% the flexural capacity of their cross-section, along with the combined gravity and brace-response-induced axial forces. Columns in FIEBs are expected to respond in a similar manner, but the relative weight of their contribution to the overall response has not yet been quantified, and whether the code requirements for columns in CBFs are adequate or need to be adapted must be verified. In this article, the contribution of columns in the seismic response of FIEBs is investigated. To this purpose, Non-Linear Response History Analysis is applied to FIEBs designed for combinations of number of storeys, two alternative bracing configurations (‘X’ and chevron with middle column), and columns arranged to bend about their major or minor axes. The influence of the braces and columns arrangement on the global response and the demands on the columns and their engagement in resisting the storey shears are assessed, and recommendations for design are proposed based on the obtained results.
Elevated systemic levels of inflammatory cytokines in older women with persistent cervical human papillomavirus infection
(Cancer Epidemiology, Biomarkers & Prevention, 2010-07-20) Kemp, Troy J.; Hildesheim, Allan; García Piñeres, Alfonso; Williams, M.C.; Shearer, G.M.; Rodríguez, Ana Cecilia; Schiffman, Mark; Burk, Robert; Freer Bustamante, Enrique; Bonilla Vargas, José; Herrero, Rolando; Pinto, Ligia A.
Background: Defects in lymphoproliferative responses to mitogens/antigens in women >45 years old with a persistent type-specific human papillomavirus (HPV) infection have been reported. Methods: To determine whether these defects were associated with altered cytokine profiles, plasma and peripheral blood mononuclear cell (PBMC) culture supernatants from 50 cases (oversampled for their reduced lymphoproliferative ability) and 50 uninfected controls (oversampled for their robust lymphoproliferative ability) were examined for 24 cytokines using multiplexed bead–based immunoassays and ELISA. Results: The following plasma cytokines were significantly increased in cases relative to controls (cases versus controls; median pg/mL): interleukin (IL)-6, 393.1 versus 14.5; IL-8, 1,128.5 versus 43.9; tumor necrosis factor-α (TNF-α), 164.1 versus 9.2; macrophage inflammatory protein-1α (MIP-1α), 1,368.9 versus 25.5; granulocyte macrophage colony-stimulating factor (GM-CSF), 13.8 versus 7.3; IL-1β, 8.3 versus 1.6 (all P < 0001);and IL-1α, 218.2 versus 169.5 (P = 0.02).We focused our analysis on the cytokines IL-6, IL-8, TNF-α, and MIP-1α due to their high fold change (>10) and highly statistically significant difference between cases and controls. Length of persistence or type of infection (high risk and low risk) did not affect these differences. IL-6, TNF-α,and MIP-1α levels were also increased in unstimulated PBMC culture supernatants from cases compared with controls (P < 0.05), however, the cytokine levels from phytohemagglutinin-stimulated PBMC culture supernatants were significantly lower in the cases (P < 0.0001). Conclusions: Persistent HPV infection in older women with evidence of immune deficit is associated with an increase in systemic inflammatory cytokines. Impact: Future studies are needed to determine whether the inflammatory profile is age dependent and to examine the role that inflammatory cytokines play in HPV-induced progression from infection to cervical cancer.
El derecho a la libertad sindical de las personas adultas sentenciadas que realizan ocupaciones remuneradas y no remuneradas en la Unidad de Atención Integral Reynaldo Villalobos Zúñiga durante el periodo 2018-2020 [PRESENTACIÓN]
(2024-10-09) Rojas Víquez, Mónica
Participación en las V Jornadas de Investigación del Instituto de Investigaciones Jurídicas (IIJ) de la Universidad de Costa Rica. Conferencia que describe los hallazgos del Trabajo Final de Grado "El derecho a la libertad sindical de las personas adultas sentenciadas que realizan ocupaciones remuneradas y no remuneradas en la Unidad de Atención Integral Reynaldo Villalobos Zúñiga durante el periodo 2018-2020", enmarcado en el proyecto de investigación C3-335 Impacto laboral y socioambiental de los monocultivos en comunidades bananeras y piñeras de la Zona Norte y Caribe. La investigación tuvo como principal objetivo establecer los aspectos que determinan el reconocimiento del derecho a la libertad sindical de las personas privadas de libertad que realizan ocupación remunerada o no remunerada en la Unidad de Atención Integral Reynaldo Villalobos Zúñiga.