College Access and Completion among Boys and Young Men of Color: Literature Review of Promising Practices

This literature review examines challenges and promising practices for increasing college access and completion among boys and young men of color. It moves beyond issues of academic preparation to other factors that appear to mediate college access and success for boys and young men of color

Siguiendo las huellas de Jorge Gil

El propósito principal de este texto es reflexionar e ilustrar la red personal del investigador mexicano Jorge Gil, con el fin de mostrar su impacto en el desarrollo del análisis de redes sociales (ARS) en México y en el mundo. Su red personal la reconstruimos a través de narrativas, comunicaciones personales, coautoría y memorias de muchos eventos académicos a los que asistió y organizó. Argumentamos que Jorge fue un actor central en el desarrollo del ARS durante más de 15 años y que aún después de su muerte su obra sobre la red política mexicana sigue teniendo un impacto en los estudios políticos.The main purpose of this text is to reflect and illustrate the personal network of the Mexican researcher Jorge Gil, in order to show his impact in social network analysis (SNA) development in Mexico and at an international level. His personal network is reconstructed by using narratives, personal communication, co-authorship, and memories from the many academic events he attended and organized. We argue that Jorge was a central actor within SNA development during more than 15 years and even after his death his work about the Mexican political network is still a major reference in the field of political studies

Time orientation, task characteristics, and customer performance

The present study illustrates that consumer time use preference moderates the effect of satisfaction with the task solution, but has no impact on level of performance. Results show that more complex tasks produce higher (lower) levels of satisfaction for polychronic (monochronic) consumers than simpler tasks. In contrast, prioritizing complex activities increases (decreases) satisfaction for monochronic (polychronic) consumers. Unlike task solution satisfaction, time orientation does not impact on task performance. These findings suggest that online retailers should emphasize site factors related to consumers\u27 tasks that best suit the time use preference of their primary users in order to maximize customer satisfaction

The role of spleen macrophages in malaria : an ultrastructural study

O presente estudo objetivou investigar através de microscopia eletrônica a natureza das células esplênicas envolvidas no processo de retirada do Plasmodium berghei do sangue de camundongos BALB/c infectados e os possíveis mecanismos utilizados. Os macrófagos, particularmente da polpa vermelha e da zona marginal, constituíram a mais importante população de células fagocitárias do baço. No pico da parasitemia, macrófagos da periferia da polpa branca, principalmente da zona do manto dos folículos secundários também participaram do processo de fagocitose. Células reticulares e interdigitais também apresentaram atividade fago- citária, embora em grau limitado. Nossas observações sugerem que a fagocitose de parasitos livres e de eritrócitos parasitados constitui o principal mecanismo de destruição intra-esplênica do plasmódio. Os parasitos podem ser retirados dos eritrócitos quando estes atravessam as pequenas fendas interendoteliais dos sinusóides e são em seguida fagocitados por macrófagos. São apresentadas evidências de que macrófagos esplênicos podem destruir parasitos através de mecanismos de citotoxicidade.An electronmicroscopy study of the spleen from mice infected with Plasmodium berghei was carried out to investigate the types ofcells in volved in the removal of parasites from the blood, and the mechanisms by which this occurs. Macrophages, particularly from the red pulp and the marginal zone of the spleen, constituted the most important population of phagocytic cells in the spleen. At the height ofparasitaemia, macrophages in the periphery of the white pulp, especially in the mantle zone of secondary follicles, were also found to participate in phagocytosis, although to a limited extent. Our fingings suggest that phagocytosis of free parasites or parasitized erythrocytes in the spleen is an important mechanism of clearance of parasites from the circulation. Parasites removed from the erythrocytes when these cells cross the interendothelial slits are further phagocytosed by neighbouring macrophages. Evidence is presented suggesting that spleen macrophages may act against the parasite through a process of cytotoxicity

Human urinary mutagenicity after wood smoke exposure during traditional temazcal use.

In Central America, the traditional temazcales or wood-fired steam baths, commonly used by many Native American populations, are often heated by wood fires with little ventilation, and this use results in high wood smoke exposure. Urinary mutagenicity has been previously employed as a non-invasive biomarker of human exposure to combustion emissions. This study examined the urinary mutagenicity in 19 indigenous Mayan families from the highlands of Guatemala who regularly use temazcales (N = 32), as well as control (unexposed) individuals from the same population (N = 9). Urine samples collected before and after temazcal exposure were enzymatically deconjugated and extracted using solid-phase extraction. The creatinine-adjusted mutagenic potency of urine extracts was assessed using the plate-incorporation version of the Salmonella mutagenicity assay with strain YG1041 in the presence of exogenous metabolic activation. The post-exposure mutagenic potency of urine extracts were, on average, 1.7-fold higher than pre-exposure samples (P < 0.005) and also significantly more mutagenic than the control samples (P < 0.05). Exhaled carbon monoxide (CO) was ~10 times higher following temazcal use (P < 0.0001), and both CO level and time spent in temazcal were positively associated with urinary mutagenic potency (i.e. P < 0.0001 and P = 0.01, respectively). Thus, the wood smoke exposure associated with temazcal use contributes to increased excretion of conjugated mutagenic metabolites. Moreover, urinary mutagenic potency is correlated with other metrics of exposure (i.e. exhaled CO, duration of exposure). Since urinary mutagenicity is a biomarker associated with genetic damage, temazcal use may therefore be expected to contribute to an increased risk of DNA damage and mutation, effects associated with the initiation of cancer

The O-antigen flippase Wzk can substitute for MurJ in peptidoglycan synthesis in Helicobacter pylori and Escherichia coli

The peptidoglycan (PG) cell wall is an essential component of the cell envelope of most bacteria. Biogenesis of PG involves a lipid-linked disaccharide-pentapeptide intermediate called lipid II, which must be translocated across the cytoplasmic membrane after it is synthesized in the inner leaflet of this bilayer. Accordingly, it has been demonstrated that MurJ, the proposed lipid II flippase in Escherichia coli, is required for PG biogenesis, and thereby viability. In contrast, MurJ is not essential in Bacillus subtilis because this bacterium produces AmJ, an unrelated protein that is functionally redundant with MurJ. In this study, we investigated why MurJ is not essential in the prominent gastric pathogen, Helicobacter pylori. We found that in this bacterium, Wzk, the ABC (ATP-binding cassette) transporter that flips the lipid-linked O- or Lewis- antigen precursors across the inner membrane, is redundant with MurJ for cell viability. Heterologous expression of wzk in E. coli also suppresses the lethality caused by the loss of murJ. Furthermore, we show that this cross-species complementation is abolished when Wzk is inactivated by mutations that target a domain predicted to be required for ATPase activity. Our results suggest that Wzk can flip lipid II, implying that Wzk is the flippase with the most relaxed specificity for lipid-linked saccharides ever identified

Lo local y lo global de la colaboración científica: ¿qué significa, y cómo visualizarlo y medirlo?

In a context in which there is great interest in intensifying international collaboration within scientific practice, this paper presents an approach on how to measure and visualize international collaborative work at the institutional level. As a case study, the three areas in scientific research of the National Autonomous University of Mexico were considered. The information was obtained from the Web of Science database, Core Collection, and all production made with participation of foreign institutions (co-authorship) from 1981 until 2013 was also considered. In order of measuring the international collaboration, we built an index based on the number of collaborations per institution, weighting these links on the base of their consistency during the considered period. A second index was calculated taking into account foreign institutions and countries of origin. Visualizations were made with Pajek.En un contexto en que hay gran interés en intensificar la colaboración internacional dentro de la práctica científica, este trabajo plantea un acercamiento sobre cómo medir y visualizar el trabajo colaborativo internacional a nivel institucional. Como caso de estudio consideramos las tres áreas del Subsistema de Investigación Científica de la Universidad Nacional Autónoma de México. La información se obtuvo de la base de datos Web of Science, Core Collection y consideramos la producción con participación de instituciones extranjeras (coautoría), en el periodo 1981 a 2013. Para medir la colaboración internacional construimos un índice con base en el número de colaboraciones por institución, en que dichos vínculos se ponderaron a partir de su consistencia durante el periodo considerado. Otro índice toma en cuenta las instituciones extranjeras y países de origen. Visualizamos las redes con Pajek

Correlación clínica – histopatológica en apendicitis aguda

Tipo de estudio: descriptivo, transversal y observacional, realizado entre marzo a septiembre de 2002; los datos fueron tomados en el departamento de Estadística del Servicio de Anatomía Patológica del hospital Luis Vernaza, de Guayaquil.Objetivos: Comprobar que el grado lesional de la Apendicitis es dependiente del tiempo de evolución de los síntomas; y,Establecer la etapa evolutiva diagnosticada con mayor frecuencia en el área de Emergencia.Materiales y métodos: Se estudiaron 342 pacientes con diagnóstico clínico preoperatorio de apendicitis. Variables: edad, sexo, procedencia, síntomas y signos, fórmula leucocitaria, horas entre el inicio del dolor y la intervención quirúrgica y diagnóstico histopatológico.Resultados: 133 pacientes fueron mujeres (38.88%) y 209 hombres (61.11%). El margen de edad fue entre los 11 y 85 años. La enfermedad se mostró con mayor frecuencia en el grupo de 21 a 25 años. Se observó dolor abdominal en 52.33%. El 46.78% presentó cuadro clínico típico. 340 tuvieron leucocitosis mayor a 10.000. Los diagnósticos histopatológicos se correspondieron con las horas de evolución del proceso. Apendicitis Gangrenosa: 122 casos (35.67%), Apendicitis Supurada: 109 pacientes (31.87%), Apendicitis incipiente: 49 pacientes (14.32%) y Apendicitis Perforada: 42 pacientes (12.28%).Conclusiones: La apendicitis aguda es una enfermedad que evoluciona en forma dependiente de sus manifestaciones clínicas y las horas de evolución del proceso. El diagnóstico más frecuente fue Apendicitis Gangrenosa