446 research outputs found
Lightweight Carbon Fiber Mirrors for Solar Concentrator Applications
Lightweight parabolic mirrors for solar concentrators have been fabricated
using carbon fiber reinforced polymer (CFRP) and a nanometer scale optical
surface smoothing technique. The smoothing technique improved the surface
roughness of the CFRP surface from ~3 {\mu}m root mean square (RMS) for as-cast
to ~5 nm RMS after smoothing. The surfaces were then coated with metal, which
retained the sub-wavelength surface roughness, to produce a high-quality
specular reflector. The mirrors were tested in an 11x geometrical concentrator
configuration and achieved an optical efficiency of 78% under an AM0 solar
simulator. With further development, lightweight CFRP mirrors will enable
dramatic improvements in the specific power, power per unit mass, achievable
for concentrated photovoltaics in space.Comment: IEEE Photovoltaic Specialist Conference (PVSC), DC, USA, 201
Extremely broadband ultralight thermally emissive metasurfaces
We report the design, fabrication and characterization of ultralight highly
emissive metaphotonic structures with record-low mass/area that emit thermal
radiation efficiently over a broad spectral (2 to 35 microns) and angular (0-60
degrees) range. The structures comprise one to three pairs of alternating
nanometer-scale metallic and dielectric layers, and have measured effective 300
K hemispherical emissivities of 0.7 to 0.9. To our knowledge, these structures,
which are all subwavelength in thickness are the lightest reported metasurfaces
with comparable infrared emissivity. The superior optical properties, together
with their mechanical flexibility, low outgassing, and low areal mass, suggest
that these metasurfaces are candidates for thermal management in applications
demanding of ultralight flexible structures, including aerospace applications,
ultralight photovoltaics, lightweight flexible electronics, and textiles for
thermal insulation
Brote de gastroenteritis por agua potable de suministro público
Introducción: La potabilidad del agua induce a descartar el
posible origen hídrico de los brotes. El objetivo fue investigar
un brote de gastroenteritis por agua potable de suministro público.
Métodos: Después de la notificación de un brote de gastroenteritis
en el municipio de Baqueira (Valle de Arán) se diseñó
un estudio epidemiológico de cohortes retrospectivo. Mediante
un muestreo sistemático se eligió a 87 personas
hospedadas en los hoteles y a 62 alojadas en diferentes apartamentos.
Se recogió información sobre 4 factores (consumo de agua
de la red, bocadillos, agua y alimentos en las pistas de esquí)
y presencia de síntomas. Se determinó la existencia de cloro,
se analizó el agua de la red y se realizó un coprocultivo a 4
enfermos. La implicación de cada factor se determinó con el
riesgo relativo (RR) y su intervalo de confianza (IC) del 95%.
Resultados: La incidencia de gastroenteritis fue del 51,0%
(76/149). Los porcentajes de los síntomas fueron los siguientes:
fiebre, 27,0%; diarrea, 87,5%; náuseas, 50,7%; vómitos, 30,3%,
y dolor abdominal, 80,0%. El único factor que presentó un riesgo
estadísticamente significativo fue el consumo de agua de
la red (RR = 11,0; IC del 95%, 1,6-74,7). La calificación sanitaria
del agua fue de potabilidad. Se observó un defecto de
situación del clorador en el depósito, que fue corregido. Se
recomendó incrementar aún más las concentraciones de cloro,
lo cual se acompañó de una disminución de los casos. Los
coprocultivos de los 4 enfermos fueron negativos para las enterobacterias
investigadas.
Conclusiones: El estudio demuestra la posibilidad de presentación
de brotes hídricos por agua cualificada como potable
y sugiere la necesidad de mejorar la investigación microbiológica
(determinación de protozoos y virus) en este tipo
de brotes
Extended description of tunnel junctions for distributed modeling of concentrator multi-junction solar cells
One of the key components of highly efficient multi-junction concentrator solar cells is the tunnel junction interconnection. In this paper, an improved 3D distributed model is presented that considers real operation regimes in a tunnel junction. This advanced model is able to accurately simulate the operation of the solar cell at high concentraions at which the photogenerated current surpasses the peak current of the tunnel junctionl Simulations of dual-junction solar cells were carried out with the improved model to illustrate its capabilities and the results have been correlated with experimental data reported in the literature. These simulations show that under certain circumstances, the solar cells short circuit current may be slightly higher than the tunnel junction peak current without showing the characteristic dip in the J-V curve. This behavior is caused by the lateral current spreading toward dark regions, which occurs through the anode/p-barrier of the tunnel junction
Capsule endoscopy interpretation: the role of physician extenders
Background and aims: capsule endoscopy (CE) allows for a
new era in small-bowel examination. Nevertheless, physicians’
time for CE-interpretation remains longer than desirable. Alternative
strategies to physicians have not been widely investigated.
The aim of this study was to evaluate the accuracy of physician
extenders in CE-interpretation.
Material and methods: one CE-experienced gastroenterologist
and two physician extenders reviewed independently 20 CEprocedures.
Each reader was blinded to the findings of their colleagues.
A consensus formed by the readers and a second
CE-experienced gastroenterologist was used as gold standard.
Number, type and location of images selected, character of CEexams
and their relationship with indications were recorded. Gastric
emptying time (GEt), small-bowel transit time (SBTt) and time
spent by readers were also noted.
Results: sensitivity and specificity for “overall” lesions was 79
and 99% for the gastroenterologist; 86 and 43% for the nurse;
and 80 and 57% for the resident. All 34 “major” lesions considered
by consensus were found by the readers. Agreement between
consensus and readers for images classification and procedures
interpretation was good to excellent (κ from 0.55 to 1). No
significant differences were found in the GEt and SBTt obtained
by consensus and readers. The gastroenterologist was faster than
physician extenders (mean time spent was 51.9 ± 13.5 minutes
versus 62.2 ± 19 and 60.9 ± 17.1 for nurse and resident, respectively;
p < 0.05).
Conclusions: physician extenders could be the perfect complement
to gastroenterologists for CE-interpretation but gastroenterologists
should supervise their findings. Future cost-efficacy
analyses are required to assess the benefits of this alternative
Degradation mechanism analysis in temperature stress tests on III-V ultra-high concentrator solar cells using a 3D distributed model
A temperature stress test was carried out on GaAs single-junction solar cells to analyze the degradation suffered when working at ultra-high concentrations. The acceleration of the degradation was realized at two different temperatures: 130 °C and 150 °C. In both cases, the degradation trend was the same, and only gradual failures were observed. A fit of the dark I–V curve at 25 °C with a 3D distributed model before and after the test was done. The fit with the 3D distributed model revealed degradation at the perimeter because the recombination current in the depletion region of the perimeter increased by about fourfold after the temperature stress test. Therefore, this test did not cause any morphological change in the devices, and although the devices were isolated with silicone, the perimeter region was revealed as the most fragile component of the solar cell. Consequently, the current flowing beneath the busbar favors the progression of defects in the device in the perimeter region
Brote de gastroenteritis por agua potable de suministro público
ResumenIntroducciónLa potabilidad del agua induce a descartar el posible origen hídrico de los brotes. El objetivo fue investigar un brote de gastroenteritis por agua potable de suministro público.MétodosDespués de la notificación de un brote de gastroenteritis en el municipio de Baqueira (Valle de Arán) se diseñó un estudio epidemiológico de cohortes retrospectivo. Mediante un muestreo sistemático se eligió a 87 personas hospedadas en los hoteles y a 62 alojadas en diferentes apartamentos. Se recogió información sobre 4 factores (consumo de agua de la red, bocadillos, agua y alimentos en las pistas de esquí) y presencia de síntomas. Se determinó la existencia de cloro, se analizó el agua de la red y se realizó un coprocultivo a 4 enfermos. La implicación de cada factor se determinó con el riesgo relativo (RR) y su intervalo de confianza (IC) del 95%.ResultadosLa incidencia de gastroenteritis fue del 51,0% (76/149). Los porcentajes de los síntomas fueron los siguientes: fiebre, 27,0%; diarrea, 87,5%; náuseas, 50,7%; vómitos, 30,3%, y dolor abdominal, 80,0%. El único factor que presentó un riesgo estadísticamente significativo fue el consumo de agua de la red (RR = 11,0; IC del 95%, 1,6-74,7). La calificación sanitaria del agua fue de potabilidad. Se observó un defecto de situación del clorador en el depósito, que fue corregido. Se recomendó incrementar aún más las concentraciones de cloro, lo cual se acompañó de una disminución de los casos. Los coprocultivos de los 4 enfermos fueron negativos para las enterobacterias investigadas.ConclusionesEl estudio demuestra la posibilidad de presentación de brotes hídricos por agua cualificada como potable y sugiere la necesidad de mejorar la investigación microbiológica (determinación de protozoos y virus) en este tipo de brotes.AbstractIntroductionThe chlorination of public water supplies has led researchers to largely discard drinking water as a potential source of gastroenteritis outbreaks. The aim of this study was to investigate an outbreak of waterborne disease associated with drinking water from public supplies.MethodsA historical cohort study was carried out following notification of a gastroenteritis outbreak in Baqueira (Valle de Arán, Spain). We used systematic sampling to select 87 individuals staying at hotels and 67 staying in apartments in the target area.Information was gathered on four factors (consumption of water from the public water supply, sandwiches, water and food in the ski resorts) as well as on symptoms. We assessed residual chlorine in drinking water, analyzed samples of drinking water, and studied stool cultures from 4 patients. The risk associated with each water source and food type was assessed by means of relative risk (RR) and 95% confidence intervals (CI).ResultsThe overall attack rate was 51.0% (76/149). The main symptoms were diarrhea 87.5%, abdominal pain 80.0%, nausea 50.7%, vomiting 30.3%, and fever 27.0%. The only factor associated with a statistically significant risk of disease was consumption of drinking water (RR = 11.0; 95% CI, 1.6-74.7). No residual chlorine was detected in the drinking water, which was judged acceptable. A problem associated with the location of the chlorinator was observed and corrected. We also recommended an increase in chlorine levels, which was followed by a reduction in the number of cases. The results of stool cultures of the four patients were negative for enterobacteria.ConclusionsThis study highlights the potential importance of waterborne outbreaks of gastroenteritis transmitted through drinking water considered acceptable and suggests the need to improve microbiological research into these outbreaks (viruses and protozoa detection)
High One-Dimensional Charge Mobility in Semiconducting Columnar Mesophases of Isocyano-Triphenylene Metal Complexes
Producción CientíficaThis paper reports the synthesis, liquid crystal behavior, and charge-transport properties in the mesophase of isocyano-triphenylene gold, copper, palladium, and platinum complexes [MX(CNR)] (CNR = 2-(6-(4-isocyanophenoxy)hexyloxy)-3,6,7,10,11-pentakisdodecyloxytriphenylene; M = Au, X = Cl, C6F5, C6F4OC10H21, CN; M = Cu, X = Cl), [(μ-4,4′-C6F4C6F4){Au(CNR)}2], [(μ-Cl2){Cu(CNR)2}2], and [MX2(CNR)2] (M = Pd, Pt; X = Cl, Br, I, and M = Pt, X = CN). The thermal and electronic properties of these materials are modulated by the metal fragment. The complexes that display columnar mesomorphism are those that support more than one triphenylene per molecule or those that produce a similar effect by dipole–dipole interactions between the metal groups. These circumstances improve the balance of favorable enthalpic interactions versus unfavorable entropic contributions into a columnar stacking. Hybrid inorganic/organic dual columnar mesophases with high SCLC hole mobility along the columnar stacking, above 1 cm2 V–1 s–1, have been found. It is worth noting that the dicyanoplatinum complex displays mesophase phosphorescence based on Pt···Pt interactions.Ministerio de Ciencia e Innovación (Proyect CTQ2014-52796-P
Extremely broadband ultralight thermally emissive metasurfaces
We report the design, fabrication and characterization of ultralight highly emissive metaphotonic structures with record-low mass/area that emit thermal radiation efficiently over a broad spectral (2 to 35 microns) and angular (0–60°) range. The structures comprise one to three pairs of alternating nanometer-scale metallic and dielectric layers, and have measured effective 300 K
hemispherical emissivities of 0.7 to 0.9. To our knowledge, these structures, which are all subwavelength in thickness are the lightest reported metasurfaces with comparable infrared emissivity. The superior optical properties, together with their mechanical flexibility, low outgassing, and low areal mass, suggest that these metasurfaces are candidates for thermal management in applications demanding of ultralight flexible structures, including aerospace applications, ultralight photovoltaics, lightweight flexible electronics, and textiles for thermal insulation
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