Membrane evaporator/sublimator investigation

Data are presented on a new evaporator/sublimator concept using a hollow fiber membrane unit with a high permeability to liquid water. The aim of the program was to obtain a more reliable, lightweight and simpler Extra Vehicular Life Support System (EVLSS) cooling concept than is currently being used

Membrane humidity control investigation

The basic performance data on a hollow fiber membrane unit that removes water from a breathing gas loop by diffusion is presented. Using available permeability data for cellulose acetate, a preliminary design was made of a dehumidifier unit that would meet the problem statement

Membrane water deaerator investigation

The purpose of the membrane water deaerator program was to develop data on a breadboard hollow fiber membrane unit that removes both dissolved and evolved gas from a water transfer system in order to: (1) assure a hard fill of the EVLSS expendable water tank; (2) prevent flow blockage by gas bubbles in circulating systems; and (3) prevent pump cavitation

Evaluación de arc flash en una minicentral hidroeléctrica

The arc flash occurs by the sudden passage of current due to the unexpected breakdown of the dielectric barrier of ionized air across the energized poles. During this phenomenon, a large amount of energy is released in the form of heat and personnel directly exposed to this event are subject to third degree burns, blindness, shock, hearing loss and even death. The objective of this paper is to show a practical methodology for calculating incident energy at work distance and the external boundary of an arc flash in a medium voltage room with cells operating at a voltage level of 34.5 kV. IEEE 1584.1-2022, IEEE 1584 -2018, IEC 60947 and IEC62271 standards do not cover arc flash calculations for voltages higher than 15kV, therefore, to achieve the stated objective, we will use Ralph Lee's method and then use software to verify the obtained results. We will also present the calculation by applying the electromagnetic field method.  Analyzing the results, we concluded that for our case study it is required that all personnel who enter to perform works with the switchgear in operation must have category 4 personal protective equipment according to NFPA 70- 2018 for incident energy range between 25 and 40 cal/cm2. In Panama there are many facilities with operating voltages above 15 kV, therefore, it is necessary to conduct further research and calculations in these places to ensure the safety of workers against the arc flash potential risk.El arc flash ocurre por el paso repentino de la corriente, debido a la ruptura súbita de la barrera dieléctrica del aire ionizado a través de los polos energizados. Durante este fenómeno, se libera una gran cantidad de energía en forma de calor y el personal de mantenimiento expuesto directamente a este evento está sujeto a quemaduras de tercer grado, ceguera, golpes, pérdida auditiva e incluso la muerte. El objetivo de este trabajo es mostrar una metodología práctica para el cálculo de la energía incidente a la distancia de trabajo y la frontera externa de un arc flash en un cuarto de media tensión con celdas operando con un nivel de voltaje de 34.5 kV. Las normas IEEE 1584.1-2022, IEEE 1584-2018, IEC 60947 e IEC62271 no cubren los cálculos de arc flash para tensiones mayores a 15kV, por lo tanto, para lograr el objetivo planteado, vamos a utilizar el método de Ralph Lee y luego utilizaremos un software para verificar los resultados obtenidos. También presentaremos el cálculo por medio de la aplicación del método de campos electromagnéticos.  Analizando los resultados obtenidos, concluimos que para nuestro caso de estudio se requiere que todo el personal que ingrese a realizar trabajos con los equipos en funcionamiento debe contar con equipo de protección categoría 4 de acuerdo con la norma NFPA 70- 2018 para rango de energía incidente entre 25 y 40 cal/cm2. En Panamá hay gran cantidad de instalaciones con voltajes de operación por encima de 15 kV, por lo tanto, se hace necesario realizar más investigaciones y cálculos en estos lugares para garantizar la seguridad de los trabajadores ante el riesgo potencial de arc flash. &nbsp

Ultrathin Oxide Films by Atomic Layer Deposition on Graphene

In this paper, a method is presented to create and characterize mechanically robust, free standing, ultrathin, oxide films with controlled, nanometer-scale thickness using Atomic Layer Deposition (ALD) on graphene. Aluminum oxide films were deposited onto suspended graphene membranes using ALD. Subsequent etching of the graphene left pure aluminum oxide films only a few atoms in thickness. A pressurized blister test was used to determine that these ultrathin films have a Young's modulus of 154 \pm 13 GPa. This Young's modulus is comparable to much thicker alumina ALD films. This behavior indicates that these ultrathin two-dimensional films have excellent mechanical integrity. The films are also impermeable to standard gases suggesting they are pinhole-free. These continuous ultrathin films are expected to enable new applications in fields such as thin film coatings, membranes and flexible electronics.Comment: Nano Letters (just accepted

Predicting prescribed magnification

Aim: To determine the best method of estimating the optimum magnification needed by visually impaired patients. Methods: The magnification of low vision aids prescribed to 187 presbyopic visually impaired patients for reading newspapers or books was compared with logMAR distance and near acuity (at 25 cm) and magnification predicted by +4 D step near additions. Results: Distance letter (r = 0.58) and near word visual acuity (r = 0.67) were strongly correlated to the prescribed magnification as were predictive formulae based on these measures. Prediction using the effect of proximal magnification resulted in a similar correlation (r = 0.67) and prediction was poorer in those who did not benefit from proximal magnification. The difference between prescribed and predicted magnification was found to be unrelated to the condition causing visual impairment (F = 2.57, p = 0.08), the central visual field status (F = 0.57, p = 0.57) and patient psychology (F = 0.44, p = 0.51), but was higher in those prescribed stand magnifiers than high near additions (F = 5.99, p < 0.01). Conclusions: The magnification necessary to perform normal visual tasks can be predicted in the majority of cases using visual acuity measures, although measuring the effect of proximal magnification demonstrates the effect of stronger glasses and identifies those in whom prescribed magnification is more difficult to predict

Doing research in peoples’ homes: fieldwork, ethics and safety – on the practical challenges of researching and representing life on the margins

Drawing on the author’s experiences and reflections of researching vulnerable people for a housing research project, this article explores the ethical dilemmas, and the health and safety challenges, of conducting in-depth, qualitative interviews with ‘vulnerable’ research participants in their own homes. Vulnerability, in a housing research context, takes account of: living in poverty; insecure housing/employment situations; poor health and/or mental ill health; alcohol and /or drug dependency, etc. Diary notes are used to illustrate the challenging situations that can unfold when working alone in the field in disadvantaged areas, with vulnerable people, which can present physical and emotional risk. Concern with risk and the potential impact on individuals is two-fold: that on the participant; and that on the researcher. Through reflexivity and revisiting of experiences in the field, this paper explains the difficulties and negotiations, and it provides some suggestions for better research practice

Medical student interest in academic medical careers: a multi-institutional study

Little is known about how medical students view academic medicine. This multi-institutional study explored student perceptions of this career path. During 2009–2010, third- and fourth-year students at three United States medical schools completed a 30-item online survey. In total, 239 students completed the questionnaire (37 % response rate). Significant predictors of students’ desires for academic medical careers included interest in teaching (γ = 0.74), research (γ = 0.53), interprofessional practice (γ = 0.34), administration (γ = 0.27), and community service opportunities (γ = 0.16). A positive correlation existed between accumulated debt and interest in academic medicine (γ = 0.20). Student descriptions of the least and most appealing aspects of academic medicine were classified into five categories: professional, research, personal, teaching and mentoring, and patients/patient care. Students are more likely to be interested in a career in academic medicine if they have participated in research or were influenced by a mentor. Factors that may also influence a medical student’s decision to pursue a career in academic medicine include age and debt accumulated prior to medical school. Professional aspects of academic medicine (cutting edge environment, resources) and the opportunity to teach were the most appealing aspects