Vision in water

Purpose: To determine visual performance in water, including the influence of pupil size. Method: The water environment was simulated by placing a goggle filled with saline in front of eyes, with apertures placed at the front of the goggle. Correction factors were determined for the different magnification under this condition to estimate vision in water. Experiments were conducted on letter visual acuity (7 participants), grating resolution (8 participants), and grating contrast sensitivity (1 participant). Results: For letter acuity, mean loss in vision in water, compared to corrected vision in air, varied between 1.1 log minutes of arc resolution (logMAR) for a 1mm aperture to 2.2 logMAR for a 7mm aperture. The vision in minutes of arc was described well by a linear relationship with pupil size. For grating acuity, mean loss varied between 1.1 logMAR for a 2mm aperture to 1.2 logMAR for a 6mm aperture. Contrast sensitivity for a 2mm aperture deteriorated as spatial frequency increased, with 2 log unit loss by 3 cycles/degree. Superimposed on this deterioration were depressions (notches) in sensitivity, with the first three notches occurring at 0.45, 0.8 and 1.3 cycles/degree and with estimates for water of 0.39, 0.70 and 1.13 cycles/degree. Conclusion: Vision in water is poor. It becomes worse as pupil size increases, but the effects are much more marked for letter targets than for grating targets.

Ruumiillinen esine, materiaalinen suku : Tutkimus Pyhä Anna itse kolmantena -aiheisista keskiajan puuveistoksista Suomessa

Embobied Object, Material Family. Late-Medieval Wood Sculptures Depicting Saint Anne with the Virgin and Child in Finland Saint Anne, the mother of the Virgin Mary, was one of the most popular saints in Western Europe in the late Middle Ages. She was often depicted with two other figures, the Virgin and the Christ Child (Anna Selbdritt). The dissertation examines the polychrome wood sculptures showing this motif, with a special focus on those remaining in Finland. It investigates the meanings these sculptures had to their observers in the fifteenth-century Finland. The study sheds light to important material heritage which is little known and offers new insights into the cult and imagery of the holy grandmother. Methodologically the study is based on iconology and post-formalist art history, and it appropriates concepts such as spatiality, sanctity, corporeality, and gender. Taking a comparative approach it knits together larger tendencies and local people and incidents. By conflating methodological domains it renews the ways how fragmentary wood sculptures, lacking documentary written sources, can be contextually interpreted and comprehended. The sculptures are analyzed from three angles. Firstly, the study explores the sculptures by focusing on their materiality and facture, which is to consider them as records of their own making. The analysis provides new information concerning the quantity, location, and current condition of the sculptures and it also elucidates problems regarding attribution, dating, display, and craftsmanship. The book presents the results of the empirical study of 45 Saint Anne groups; these works are individually described in the large Appendix. Secondly, the works are contextualized to the specific historical conditions in which they were observed. The study discusses closely the circumstances in the Turku Cathedral around the shrine of Saint Anne, the popular belief, and the piety of individual persons. The sculptures, deemed as the embodiments of the holy characters, interacted with the devotees. Thirdly, the works are examined within the wider theological and ideological currents of the era centered on the body and Incarnation. Saint Anne with the Virgin and Child motif demonstrated the Carnal Trinity, the motherly side of the Holy Trinity. The dissertation argues that Saint Anne was interpreted as the female counterpart or, in a mythical sense, wife of God. Furthermore, the Child s implicit, simultaneous presence as a suffering or dead man imbues the sculptures with a sense of the Passion, thus associating them with the pietà and the Mater dolorosa motifs. The naked Christ Child underlines him as the offering and, eventually, the Eucharistic wafer. The study suggests that the sculptures mediate continuity and the bloodline between the generations by the intertwined and repeated gestures, clothing and positions of the portrayed figures. Regardless of the ostensible homeliness of the sculptures, so readily reiterated by earlier scholars, these sculptures represented creation and birth through the carnal yet holy mothers.

Pattern visual evoked potentials in dyslexic versus normal children

Purpose: Presence of neurophysiological abnormalities in dyslexia has been a conflicting issue. This study was performed to evaluate the role of sensory visual deficits in the pathogenesis of dyslexia. Methods: Pattern visual evoked potentials (PVEP) were recorded in 72 children including 36 children with dyslexia and 36 children without dyslexia (controls) who were matched for age, sex and intelligence. Two check sizes of 15 and 60 min of arc were used with temporal frequencies of 1.5 Hz for transient and 6 Hz for steady‑state methods. Results: Mean latency and amplitude values for 15 min arc and 60 min arc check sizes using steady state and transient methods showed no significant difference between the two study groups (P values: 0.139/0.481/0.356/0.062).Furthermore, no significant difference was observed between two methods of PVEPs in dyslexic and normal children using 60min arc with high contrast(Pvalues: 0.116, 0.402, 0.343 and 0.106). Conclusion: The sensitivity of PVEP has high validity to detect visual deficits in children with dyslexic problem. However, no significant difference was found between dyslexia and normal children using high contrast stimuli.

Incremental Cycle Detection, Topological Ordering, and Strong Component Maintenance

We present two online algorithms for maintaining a topological order of a directed n-vertex acyclic graph as arcs are added, and detecting a cycle when one is created. Our first algorithm handles m arc additions in O(m(3/2)) time. For sparse graphs (m/n = O(1)), this bound improves the best previous bound by a logarithmic factor, and is tight to within a constant factor among algorithms satisfying a natural locality property. Our second algorithm handles an arbitrary sequence of arc additions in O(n(5/2)) time. For sufficiently dense graphs, this bound improves the best previous bound by a polynomial factor. Our bound may be far from tight: we show that the algorithm can take Omega(n(2)2 root(2lgn)) time by relating its performance to a generalization of the k-levels problem of combinatorial geometry. A completely different algorithm running in Theta (n(2) log n) time was given recently by Bender, Fineman, and Gilbert. We extend both of our algorithms to the maintenance of strong components, without affecting the asymptotic time bounds.

El lenguaje místico en Santa Catalina de Siena

Resumen: El lenguaje místico posee características propias, una de ellas es la inefabilidad. En este artículo la autora, basándose en los conceptos elaborados por M. De Certeau, analiza en primer lugar los rasgos que posee este lenguaje en la obra de Santa Catalina de Siena. En segundo lugar el artículo explora la matriz epistolar que posee Il Dialogo della Divina Provvidenza, la obra más importante de la santa. Aquí se observa de qué manera una gramática hablada conserva las entonaciones propias de la meditación que le da origen. Teniendo su origen en una carta Il Dialogo no sólo manifiesta el lenguaje oral usado en su época sino su estatuto privado y público a la vez.

Imaginario y realidad de la muerte de Santa María Egipciaca en el contexto castellano de la crisis del siglo XIV

Resumen: El presente trabajo se propone analizar el sentido y la funcionalidad del tema de la muerte del santo en el contexto de la crisis que afecta a Europa en el siglo XIV, a través de la muerte de Santa María Egipciaca –una de las santas medievales más populares– narrada en la Vida de Santa María Egipciaca, un poema castellano compuesto en el temprano siglo XIII pero transmitido a fines del siglo XIV en el manuscrito K-III-4 de la Biblioteca de San Lorenzo de El Escorial.

El Concilio de Constanza y el fin del Cisma : el rol del reino de Castilla en el camino hacia la unidad

Resumen: El Concilio de Constanza (1414-1418) fue la instancia definitiva de solución del Cisma de Occidente. Sus decisiones condujeron

Gioconda Belli, un universo de mujeres

[ES] En este artículo analizaremos el devenir del universo de mujeres de Gioconda Belli, a través de la mirada de tres personajes protagonistas femeninos que se pronuncian de forma contundente sobre la vida y la estética literaria de la autora. Partiremos del análisis de Lavinia, protagonista femenina de La mujer habitada (1988) la primera novela de la autora, a continuación analizaremos el perfil de Sofia protagonista de Sofía de los presagios (1990), su segunda novela. Y por último, escudriñaremos las características de un personaje femenino que propone una nueva lectura de la mítica Juana de Castilla, protagonista de El Pergamino de la seducción (2005). Las tres figuras femeninas literarias nacen de sus propias experiencias simultaneadas por la memoria, compañera inseparable en el afianzamiento del yo y son heroínas de su propia historia

Aportación a las representaciones de úrsidos en el arte mobiliar magdaleniense

[ES] Durante la primera mitad del siglo XX se realizaron amplias excavaciones arqueológicas en la cueva de Isturitz que aportaron abundantes evidencias industriales y artísticas. En este artículo se trata de dar a la luz una obra de arte mueble que permanece inédita, en concreto una pareja de osos fabricados sobre una costilla, y que procede del nivel magdaleniense de la colección Saint-Périer.

Reliable concentrated photovoltaic system with compound concentrator

Concentrated photovoltaic systems (CPVSs) draw more and more attention because of high photovoltaic conversion efficiency, low consumption of solar cell, and low cost of power generation. However, the fallibility of the tracker in such systems has hindered their practical application for more than twenty years. The tracker is indispensable for a CPVS since only normal-incident sunlight can be focused on the solar cell chips, even a slight deviation of incident light will result in a significant loss of solar radiation, and hence a distinct decrease in electricity output. Generally, the more accurate the tracker is, the more reliable the system is. However, it is not exactly the case for a CPVS reliability, because the more accurate the tracker is, the better environment it demands. A CPVS is usually has to subjected to harsh environmental conditions, such as strong wind, heavy rain or snow, and huge changes of temperature, which leads to the invalidation of the system's high-accuracy tracker. Hence, the reliability of a CPVS cannot be improved only by enhancing the tracker's accuracy. In this paper, a novel compound concentrator, combination of Fresnel lens and photo-funnel, has been adopted in a prototype CPVS. Test results show that the compound concentrator can relax the angle tolerance from one tenth to five degrees of arc at 400 suns, which can help a CPVS endure serious environment and remain its reliability over long period. The CPVS with compound concentrator is attractive for commercial application.

Plasma and electrode emissions from a 1 kW hydrogen-nitrogen arcjet thruster

Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures.

减压直流非转移电弧及等离子体射流波动特性研究

实时测量了减压直流纯氩等离子体的弧电压和射流高温区的瞬时离子饱和电流. 结合射流高温区的瞬时形貌, 探讨了在真空室压力500~10000 Pa条件下电弧及等离子体射流的波动特性. 结果表明:当气流量较小和真空室压力较低时, 射流流场呈现较好的稳定性. 随着气流量和真空室压力增加, 弧电压出现高频脉动, 射流能量分布的空间和时间稳定性逐渐变差, 离子饱和电流信号变得紊乱;即使由于电源特性引起电弧功率300 Hz的波动幅度高达35%, 依然能够产生流场较稳定的等离子体射流;静电探针检测等离子体射流的瞬时离子饱和电流可作为了解射流波动特性的一种快速响应方法.

Experimental study on energy dissipation in a 1 kW arcjet thruster

As a simple and reliable propulsion system, arcjet thrusters have been used in multiple satellite missions. In order to improve the efficiency of arcjet thrusters, energy dissipation study was carried out in a 1 kW arcjet thruster with pure N2, H2-N2 and H2 as the propellant. Using a 698 nm interference filter, thermal radiation was isolated from arc and plume emissions and the internal nozzle temperature was obtained by converting the thermal radiation signals. Results show that the addition of hydrogen leads to higher nozzle temperature, which is the determining factor for the mode of arc root attachment. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures. Output energy distribution analysis shows that losses from frozen flow and exhaust thermal losses are the main parts in limiting the efficiency of arcjet thrusters.

Experimental study on energy dissipation in a 1 kW arcjet thruster

As a simple and reliable propulsion system, arcjet thrusters have been used in multiple satellite missions. In order to improve the efficiency of arcjet thrusters, energy dissipation study was carried out in a 1 kW arcjet thruster with pure N2, H2-N2 and H2 as the propellant. Using a 698 nm interference filter, thermal radiation was isolated from arc and plume emissions and the internal nozzle temperature was obtained by converting the thermal radiation signals. Results show that the addition of hydrogen leads to higher nozzle temperature, which is the determining factor for the mode of arc root attachment. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures. Output energy distribution analysis shows that losses from frozen flow and exhaust thermal losses are the main parts in limiting the efficiency of arcjet thrusters.

Volt-ampere characteristics, nozzle temperature and thruster performances in a low power argon arcjet

Argon gas with simple atomic structure and favorite arcing stability at low input power was used as the propellant. The thruster with a regeneratively cooled nozzle were tested in a vacuum system capable of keeping the chamber pressure at about 10 Pa at a propellant feeding rate of 5 slm. Arc current, arc voltage, thrust, nozzle temperature and propellant feeding rate were measured in situ simultaneously. Effects of the working parameters such as the propellant feeding rate and arc current on the thruster performances, mainly the produced thrust, specific impulse and thrust efficiency, were examined. The variation of arc volt-ampere characteristics with running time and the effect of nozzle temperature on thruster property are discussed.