Assessment of cellulose nanocrystals as mechanical reinforcement paper additives

Cellulose nanocrystals (CNC) are nanosized crystals of cellulose chains that can be extracted from several cellulose source and exhibit mechanical properties superior to Kevlar or glass fiber. These CNC were isolated using sulfuric acid hydrolysis from bleached Eucalyptus spp. Kraft pulp with high yield (> 70 %). CNC were successfully neutralized using a sequence of short centrifugation washing steps, drying in a transparent rigid polymer. The CNC were chemically modified at its surface prior to be used as additive to improve the mechanical properties of paper sheets. The addition of CNC obtained from three different conditions (after hydrolysis, after alkalinization and after oxidation with potassium meta periodate) were added in three levels to the paper. The results showed that acid and alkalinized CNC did not provoke a significant nor incremental increase in mechanical properties; but oxidized CNC addition results in large and continuous improvement of the mechanical properties, specially Tensile Index, Burst Index, and Folding Endurance.Los nanocristales de celulosa (CNC) son estructuras en el rango de los nanómetros conformadas por cadenas de celulosa empaquetadas con orden cristalino, y exhiben algunas propiedades mecánicas superiores al Kevlar o a la fibra de vidrio. Estos CNC se aislaron de pulpa Kraft blanqueada de Eucalyptus spp, con alto rendimiento (> 70 %). Los nanocristales fueron neutralizados exitosamente utilizando una secuencia de lavados y centrifugaciones cortas, logrando obtener un sólido que al secarse formo un polímero rígido y transparente. Los nanocristales fueron modificados químicamente en su superficie antes de ser incorporados como aditivos para mejorar las propiedades mecánicas del papel. La adición se efectuó con tres tipos de nanocristales (como se obtuvieron luego de la hidrolisis, luego de ser alcalinizados, y luego de ser oxidados por meta periodato de potasio), en tres niveles de adición. Las pruebas mecánicas sobre el papel demostraron que la adición de cristales ácidos y alcalinizados, no lograron un incremento ni significativo ni sostenido de las propiedades mecánicas. Pero los nanocristales oxidados, provocaron un aumento claro y sostenido del desempeño mecánico, especialmente el índice de tracción, la resistencia al reventamiento, y la resistencia a pliegues

CO2 Concentration and Occupants’ Symptoms in Naturally Ventilated Schools in Mediterranean Climate

A large part of the school building stock in Andalusia lacks ventilation facilities, so that the air renewal of the classrooms is achieved through the building envelope (air infiltration) or the opening of windows. This research analyses the airtightness of the classrooms in Andalusia and the evolution of CO2 concentration during school hours through in situ monitoring. Pressurization and depressurization tests were performed in 42 classrooms and CO2 concentration was measured in two di erent periods, winter and midseason, to study the impact of the di erent levels of aperture of windows. About 917 students (11–17 years of age) were surveyed on symptoms and e ects on their health. The mean n50 values are about 7 h-1, whereas the average CO2 concentration values are about 1878 ppm, with 42% of the case studies displaying concentrations above 2000 ppm with windows closed

La calidad de los retornos de riego en Riegos del Alto Aragón (Huesca, España)

El objeto principal de este trabajo es caracterizar la contaminación inducida por el regadío en el sistema de Riegos del Alto Aragón (Huesca, España) durante el periodo octubre de 2007 a septiembre de 2012. Se eligieron seis puntos de control denominados P4 (Montesusín), P5 (Grañén), P7 (Lalueza), P9 (Orillena), P10 (Sariñena) y P11 (Peralta de Alcofea). En todos los puntos, se tomaron muestras de agua y se midió el caudal durante el periodo considerado. En las muestras de agua recogidas se analizaron la conductividad eléctrica (CE) y los nutrientes (N y P). Los resultados indicaron que la salinidad de las aguas de drenaje de las 6 cuencas estudiadas es baja en general, casi siempre inferior a 2,0 dS/m (excepto en P4). La salinidad es superior en todos los puntos durante la estación de no riego, apuntando a un efecto de dilución por los sobrantes de riego. Por otra parte, las concentraciones medias de nitrato son especialmente altas (superior al límite superior admisible de 50 mg/l para aguas destinadas a consumo humano) en los retornos de riego de las cuencas regadas por aspersión y donde dominan los cultivos de maíz y alfalfa como P11 (103 mg/l) y P10 (101 mg/l). En cuanto al fósforo, P10 es el único punto que no presenta ningún problema medioambiental inducido por el fósforo ya que las concentraciones medias registradas son muy bajas. Para el resto de los puntos, y especialmente para P4 y el P11, sus aguas de drenaje presentan un claro riesgo de eutrofización

Analysis of Circadian Stimulus and Visual Comfort Provided by Window Design in Architecture

Light is the major synchronizer of circadian rhythms to the 24-hour solar day. Compared to the visual system, the circadian system requires more light to be activated and is more sensitive to short-wavelength light. Daylighting is an ideal light source for circadian entrainment. Architectural and design features, such as window size and room reflectances impact the amount of circadian stimulus that the patient will receive. DaySim 3.2 simulations were used to determine the percentage of days that occupants would receive a minimum circadian stimulation of 0.50 for at least an hour during the morning. According to a phototransduction model of the human circadian system, a circadian stimulation of 0.50 is equivalent to suppressing the hormone melatonin by about 50%. This circadian stimulus criterion is examined for different window to wall ratios, for two average room reflectances, and for four latitudes. The present paper provides an example of a tool that could be used to assist designers in fenestration and interior design

Indoor comfort and symptomatology in non-university educational buildings: occupants’ perception

The indoor environment in non-university classrooms is one of the most analyzed problems in the thermal comfort and indoor air quality (IAQ) areas. Traditional schools in southern Europe are usually equipped with heating-only systems and naturally ventilated, but climate change processes areboth progressively increasing average temperatures and lengthening the warm periods. In addition,air renewal is relayed in these buildings to uncontrolled infiltration and windows’ operation, buturban environmental pollution is exacerbating allergies and respiratory conditions among the youthpopulation. In this way, this exposure has a significant effect on both the academic performanceand the general health of the users. Thus, the analysis of the occupants’ noticed symptoms and their perception of the indoor environment is identified as a potential complementary tool to a more comprehensive indoor comfort assessment. The research presents an analysis based on environmentalsensation votes, perception, and indoor-related symptoms described by students during lessons contrasted with physical and measured parameters and operational scenarios. This methodology is applied to 47 case studies in naturally ventilated classrooms in southern Europe. The main conclusionsare related to the direct influence of windows’ operation on symptoms like tiredness, as well asthe low impact of CO2 concentration variance on symptomatology because they usually exceeded recommended levels. In addition, this work found a relationship between symptoms under study with temperature values and the environmental perception votes, and the special impact of the lack of suitable ventilation and air purifier systems together with the inadequacy of current thermal system

Smart controls for lighting design: towards a study of the boundary conditions

This research aims to determine the effect of the lighting smart controls in the energy consumption in buildings, according to the geometry of the room, the window size, the reflectance of the inner surfaces and the location of study. For this purpose, two lighting smart controls are proposed: one based in an On/Off lighting control with separated lines and other with a dimming control. The analysis of both control systems is carried out by using daylight dynamic metrics, such as the daylight autonomy and the continuous daylight autonomy. The results quantify the effect of the architectural variables of the room in the performance of the lighting smart controls

Dynamic analysis of office lighting smart controls management based on user requirements

Daylight dynamic metrics provide an alternative approach for the assessment of the energy savings promoted by lighting control systems. This research aims to quantify the energy savings allowed by lighting smart controls using continuous and overcast daylight autonomy, novel metrics tested monitoring a mesh of illuminance-meters in test cells over a one-year period. Three types of smart controls are proposed, based on switches and dimmers, some of which were managed by illuminance-meters and irradiance detectors. Energy savings are assessed according to weather data, room dimensions, inner reflectances, window size and user requirements—illuminance needs and working hours. The results show a reduction in the average energy consumption of electric lighting of up to 23%, suggesting the suitability of the smart controls proposed. Smart controls without illuminance-meter feedback are only recommended for shallow rooms with low requirements, while dark deep rooms demand a complex dimming system managed by external illuminance-meters

Tracheal self-expandable metallic stents: A comparative study of three different stents in a rabbit model

Introduction: The objective of this study was to assess tracheal reactivity after the deployment of different self-expandable metal stents (SEMS). Material and methods: Forty female New Zealand rabbits were divided into four groups. Three groups received three different SEMS: steel (ST), nitinol (NiTi), or nitinol drug-eluting stent (DES); the fourth group was the control group (no stent). Stents were deployed percutaneously under fluoroscopic guidance. Animals were assessed by multislice, computed tomography (CT) scans, and tracheas were collected for anatomical pathology (AP) study. Data from CT and AP were statistically analyzed and correlated. Results: The DES group had the longest stenosis (20.51±14.08 mm vs 5.84±12.43 and 6.57±6.54 mm in NiTi and ST, respectively, day 30; P<.05), and higher granuloma formation on CT (50% of cases). The NiTi group showed the lowest grade of stenosis (2.86±6.91% vs 11.28±13.98 and 15.54±25.95% in DES and ST, respectively; P<.05). The AP study revealed that the ST group developed intense proliferative reactivity compared to the other groups. In the DES group, a destructive response was observed in 70% of the animals, while the NiTi was the least reactive stent. CT was more effective in detecting wall thickening (positive correlation of 68.9%; P<.001) than granuloma (not significant). Conclusions: The ST group developed granulomas and significant stenosis. NiTi was the least reactive stent, while DES caused significant lesions that may be related to drug dosage. This type of DES stent is therefore not recommended for the treatment of tracheobronchial stenosis. Introducción: El objetivo de este estudio es evaluar la reactividad traqueal tras la implantación de distintos stents metálicos autoexpandibles (SMAE). Material y métodos: Se utilizaron 40 conejos hembra de raza neozelandesa, que se dividieron en 4 grupos. En 3 grupos se implantaron SMAE: de acero (SA), de nitinol (NiTi) o stents liberadores de nitinol (SLF). El cuarto grupo fue el grupo de control (sin stent). Los stents se implantaron por vía percutánea bajo control fluoroscópico. Los animales se evaluaron mediante tomografía axial computarizada (TAC) multicorte y las tráqueas se extirparon para su estudio anatomopatológico (EAP). Los datos de la TAC y el EAP se analizaron estadísticamente y se correlacionaron Resultados: El grupo que recibió SLF presentaba la mayor longitud de estenosis (20,51±14,08 mm frente a 5,84±12,43 y 6,57±6,54 mm en los grupos NiTi y SA, día 30; p < 0,05) y el mayor índice de formación de granulomas evidenciados mediante TAC (50% de los casos). El grupo al que se implantaron stents NiTi mostró el menor grado de estenosis (2,86±6,91% frente a 11,28±13,98 y 15,54±25,95% en los grupos SLF y SA; p < 0,05). En el estudio AP, el grupo SA presentó reactividad proliferativa intensa en comparación con los otros 2 grupos. En el grupo SLF se observó una respuesta destructiva en el 70% de animales, mientras que el stent NiTi fue el que menos reacción provocó. La TAC resultó ser superior para detectar el engrosamiento (correlación positiva de un 68,9%; p < 0,001) que para la observación de granulomas (n.s.). Conclusiones: El grupo SA desarrolló granulomas y estenosis significativas. El stent NiTi fue el que menos reacción indujo, mientras que el SLN provocó lesiones importantes que podrían estar relacionadas con la dosis de fármaco. Por consiguiente, este tipo de SLF no se recomienda para el tratamiento de la estenosis traqueobronquial

Analysis of visual comfort and circadian stimulus provided by window design in educational spaces

Light is the main variable which affects to the circadian rhythm, promoting up to 70% of the melatonin suppression. In comparison with the visual system, the circadian system requires more light to be activated and is more sensitive to blue light. As can be deduced, daylighting represents an ideal light source for circadian entrainment. Architectural and design features, such as window size and room reflectance, impact the amount of circadian stimulus that occupants will receive. This study aims to quantify the circadian stimulus promoted in classrooms, according to the window size and reflectance of the surfaces. A first trial is carried out, monitoring the spectral power distribution perceived by the eyes of the students according to different orientations and observer’s positions. Secondly, several simulations are developed, using the daylight simulation program DaySim 3.1 and defining a classroom model with a variable window size and reflectance. The results show the noticeable impact of the reflectance of the inner surfaces in the circadian stimulus calculation, as well as the effect of the window size