Artificial Sun Research Articles

Seasonality of UV-radiation and vitamin D status at 69 degrees north

The main purpose with this study was to assess the seasonal variation in measured UV-radiation and its impact on vitamin D status throughout one year in subjects living at high latitude. Blood samples drawn from 60 volunteers (44 women, 16 men) living at Andenes (69 degrees N), Norway, were collected throughout one year, at two-month intervals. The blood samples were analysed for 25-hydroxy vitamin D [25(OH)D]. Data on dietary intakes of vitamin D, time spent in daylight, use of sun beds and sun seeking holidays were collected by using questionnaires. The ambient vitamin D effective UV-radiation was measured at a site near by Andenes, and the number of hours spent outdoors with sufficient radiation for cutaneous vitamin D production (UV-hours) was estimated for each day. The mean 25(OH)D values were significantly higher at the end of the summer and in December, 2004 and varied from 42.0 nmol L(-1) in October, 2004 and April, 2005 to around 47 nmol L(-1) in December, 2004 and September, 2005. For the whole group, a positive relationship between UV-hours and 25(OH)D was found at UV-hours>or=3.5. However, for subjects with lower 25(OH)D levels i.e. at least one blood measurement with 25(OH)D<37.5 nmol L(-1), the positive relationship were found at around 1.5 UV-hours and more, whereas for the group of subjects that had all their vitamin D values above 37.5 nmol L(-1), positive relationship was found at UV-hours>or=4.0, when adjusting for vitamin D intake, sun bed use and sun seeking holidays. The generally high dietary intakes of vitamin D, especially in winter, mask largely the effect of seasonal variation in UV-exposure, causing an atypical seasonal variation in vitamin D status. The UV-hour variable significantly predicted 25(OH)D levels in blood when adjusted for intakes and artificial UV-radiation exposure and sun holidays abroad.

Artificial Sun Protection: Sunscreens and Their Carrier Systems

The formulation of sunscreens products requires information about the properties of the substances responsible for the sun protection, their action mechanisms and the vehicles used for their administration. The improvement of the performance of sunscreen substances by a modification of their chemical, physical and technological properties or by the use of conventional and novel carriers is described in this review. The sun protection achieved by the use of sunscreens incorporated into carriers in terms of the sun protection factor (SPF) and other performance indices is also shown. Current manufacturing methods to incorporate sunscreen substances into vehicles are briefly described. Furthermore, basic information related to the dermatological effects of the UV radiation classified according to the different spectral regions of the UV radiation is presented in this manuscript.

Solar Sail Halo Orbits at the Sun–Earth Artificial L1 Point

Halo orbits for solar sails at artificial Sun–Earth L1 points are investigated by a third order approximate solution. Two families of halo orbits are explored as defined by the sail attitude. Case I: the sail normal is directed along the Sun-sail line. Case II: the sail normal is directed along the Sun–Earth line. In both cases the minimum amplitude of a halo orbit increases as the lightness number of the solar sail increases. The effect of the z-direction amplitude on x- or y-direction amplitude is also investigated and the results show that the effect is relatively small. In case I, the orbit period increases as the sail lightness number increases, while in case II, as the lightness number increases, the orbit period increases first and then decreases after the lightness number exceeds ~0.01.

Moon orientation in adult and young sandhoppers under artificial light

Our experiments, carried out at night and during the day on adults and laboratory-born young of the sandhopper Talitrus saltator, deal with the identification and use of the moon as an orientating factor. Sandhoppers were released in an apparatus (a Plexiglas dome) that produced a scenario similar to the natural one (with artificial sky, moon or sun illuminated at different intensities). When tested at night, the adult and young sandhoppers used the artificial moon like the natural one, independently of the intensity of illumination of the artificial sky and moon. In other words, sandhoppers tested at night always identified the artificial moon as the moon and never as the sun. In daytime releases, the seaward orientation failed at low intensities of artificial sky and sun illumination (3.07 and 1.55 microW cm2, respectively), whereas the sun compass was used effectively at higher levels of artificial sun and sky illumination. The innate ability of moon compass orientation in inexpert young sandhoppers was demonstrated even under artificial light.

Test-retest of self-reported exposure to artificial tanning devices, self-tanning creams, and sun sensitivity showed consistency

Objective Exposure to ultraviolet radiation has consistently been linked to an increased risk of melanoma. Epidemiologic studies are susceptible to measurement error, which can distort the magnitude of observed effects. Although the reliability of self-report of many sun exposure factors has been previously described in several studies, self-report of use of artificial tanning devices and self-tanning creams has been less well characterized. Study Design and Methods A mailed survey was re-administered 2–4 weeks after completion of the initial survey to 76 randomly selected participants in a case-control study of melanoma. Cases and controls were individuals diagnosed in 1999 and 2000 who were ascertained from the Iowa Cancer Registry in 2002. We assessed the consistency of self-reported use of sunlamps and self-tanning creams, sun sensitivity, and history of sunburns. Results There was substantial reliability in reporting the use of sunlamps or self-tanning creams (cases: Kappa (κ) = 1.0 for both exposures; controls: κ = 0.71 and 0.87, respectively). κ estimates of 0.62–0.78 were found for overall reliability of several sun sensitivity factors. Conclusion Overall, the survey instrument demonstrated substantial reproducibility for factors related to the use of sunlamps or tanning beds, self-tanning creams, and sun sensitivity factors.

Lux et Tenebris: Etienne-Louis Boullée’s Cenotaph for Sir Isaac Newton

In 1784 the visionary French architect Etienne-Louis Boullée (1728– 1799) designed a colossal monument to Isaac Newton (1642–1727) that was both a cenotaph and a planetarium. A tribute to Newton’s contributions to astronomy, the building was conceived as a microcosm in which the night sky would be visible by day and the daytime sky by night. Entering the ‘center of gravity’ of a vast hollow globe set in cylindrical tiers, the viewer would experience the virtual reality of the starry heavens created by natural light sparkling through shafts in the exterior of the masonry sphere. At night, the interior would be transformed into day by a luminous artificial sun suspended from the vault in an armillary sphere. Belonging to the brotherhood of freemasons whose motto was ‘lux ex tenebri’ or ‘light out of darkness’, Boullée believed in the mystical origins of knowledge. His monument was a vindication of Newton whose law of universal gravitation had been attacked as ‘occult’ by Leibniz and others. Boullée’s design can be traced to Archimedes, who was the son of an astronomer and the inventor of the first planetarium c. 250 BCE. Archimedes’ tomb in Syracuse was surmounted with a sphere inside a cylinder representing his discovery of the formulas for finding their volumes and surface areas. The Newton cenotaph was also a development of the Gottorp Globe (1654-1664), a revolving planetarium made of a pierced hollow sphere that held twelve people. Although the enormity of Boullée’s plan was impossible to construct in the eighteenth century, architects treasured his evocative drawings. More than 200 years later, the architect James Stewart Polshek acknowledged the Newton cenotaph as the inspiration for his design for the planetarium of the Rose Center for Earth and Space in New York.

Sun Compass Orientation of Tylos europaeus (Crustacea, Isopoda) Under Artificial Light

AbstractTo provide a first assessment of the parameters used by adult individuals of the supralittoral isopod Tylos europaeus to recognize the sun as a compass orienting reference, we used the apparatus designed and tested with the amphipod T. saltator. The apparatus reproduces a scenario similar to the natural one (with a false sun and sky illuminated artificially). The scenario produced inside the apparatus is sufficient to induce the isopods to exhibit solar orientation similar to that of conspecifics tested under the natural sun and sky. Nevertheless, this ability depends on some threshold values of illumination of the artificial sun and sky: to obtain a good orientation the irradiance of the artificial sun and sky should be more than 0.4 and 1.3 μW/cm2 respectively. When the artificial sky is not illuminated, the individuals show only a photopositive tendency.

Exposure to the sun and sunbeds and the risk of cutaneous melanoma in the UK: a case–control study

Migration, latitude and case–control studies have clearly established a link between melanoma and sun exposure. This case–control study of melanoma was set up to examine the role of sun exposure and sunbeds in the pathogenesis of melanoma in the United Kingdom (UK), a country with low levels of ultraviolet radiation. The study included 413 cases and 416 controls. More than 10 severe sunburns compared with less than 10 sunburns was associated with an Odds Ratio (OR) of 1.98 (95% Confidence Interval (CI) 1.02–3.86) (P=0.04) when adjusted for age, gender and skin type. Sunburns before the age of 15 years were not associated with melanoma once adjustments for age, gender and skin were made. 31% of women and 16% of the men had used sunbeds. Sunbed users were younger than non-users (40 years versus 51 years, P<0.0001). Ever use of sunbeds gave an adjusted OR of 1.19 (95% CI 0.84–1.68) (P=0.33). The risk of melanoma did not increase with increasing hours or years of sunbed exposure. The risk associated with sunbed use was only significant for young individuals with fair skin for whom there was a significant OR of 2.66 (95% CI 1.66–6.09) (P=0.02) after adjustment for the sun exposure variables. Outdoor occupation and residence in hot countries were not associated with an increased risk of melanoma. The only significant associations in this study were with 10 or more sunburns and the use of a sunbed in young subjects with fair skin. Sunbed use is now becoming more prevalent in Caucasian populations and the results of this study suggest that sunbed usage may moderately affect individuals with sun-sensitive skin types. However, the magnitude of melanoma risk in association with natural and artificial sun exposure is small compared with phenotypic risk factors such as skin type and naevus counts. However, it is possible that the mean lag time of 7 years between exposure to sunbed and melanoma in this study may have led to an under-estimation of the long-term melanoma risk.

Aqueous Photolysis of 14C-BAS 654 H under Artificial Sunlight

Photolysis of 1 4 C-BAS 654 H (pyridine and phenyl labels) was conducted in aqueous buffers of pH 5, 7 and 9 at 22 ′ 1° C under sterile conditions using artificial sun light source. BAS 654 H degraded photolytically to a number of products as shown in Scheme 3. Identity of the photo degradation products was established employing HPLC co-chromatography with reference standards and/or spectral data (MS and 1 H-NMR).

Experimental study of external occulters for the Large Angle and Spectrometric Coronagraph 2: LASCO-C2

To reduce the level of stray light in a new-generation externally occulted space coronagraph, we consider new concepts for its external occulter and its associated diaphragm and report extended measurements of their light-rejection properties. The experimental setup, which includes an artificial Sun, uses both photometric and CCD imaging techniques and permits the study of the sensitivity to misalignement of the instrument's performance. Conic occulters that have either a multithreaded or a polished surface are found to give performances superior to those of the classical three-disk system and further are highly tolerant to misalignement. Serrated diaphragms outperform circular ones, as the bulk of the diffracted light is diverted from the coronagraphic objective.

Artificial light and sun compass orientation in the sandhopper Talitrus saltator (Crustacea, Amphipoda)

Experiments on compass orientation under artificial light were conducted with adult individuals of Talitrus saltator. The aim was to reproduce in the laboratory an orientation based on the sun compass corresponding to that recorded in conditions of the true sun and sky. This was obtained by the creation within an opaque Plexiglas dome of a scenario that permitted variation of the brightness of the artificial sky and sun. The results show that it is possible to obtain sun compass orientation corresponding to the natural situation even in an artificial environment. It can be concluded that sandhoppers identify an artificial light source as the sun if the artificial sky is also illuminated and if the intensities of the artificial sun and sky exceed certain threshold values (1.13 and 10 μW cm−2, respectively). The results of other experiments under the natural blue sky with an artificial sun and with the real sun attenuated are discussed.

Sun behaviour and perceptions of risk for melanoma among 21-year-old New Zealanders.

This study investigated perceived risk of melanoma, sunscreen use and frequency of sunburn in a large sample of young New Zealanders. A self-report questionnaire was administered to a sample of 909 21-year-olds to survey their perception of how sun behaviours affect their risk of getting melanoma, how often they get sunburn, how often they use sunscreen and what factors would get them to use sunscreen more often. Knowledge of melanoma was high, but myths concerning 'safe tanning' persisted. Many young adults believed that sunbathing regularly using a sunscreen and obtaining a good base tan from gradual sun exposure decreased their risk of getting melanoma. They were unsure about the use of artificial sun beds and if their use would increase or decrease their risk. Males and females differed significantly on many aspects of their sun behaviour. Most used sunscreen only 'sometimes' and its use was linked to knowledge of melanoma and perceptions of risk. The best way to modify the sun behaviour of young adults is to target both their knowledge of melanoma risk factors and their perceptions of risk.

A theoretical and experimental investigation of a novel built-in-storage solar water heater

In this work, a novel built-in-storage type solar water heater of about 87 l capacity has been investigated theoretically and experimentally for the case of no draw-off. The solar water heater which performs the dual function of absorbing and storing hot water is made of 5 pipes, each of length 1.8 m and diameter 12 cm. A baffle plate is placed inside each pipe. The experiments have been performed inside the laboratory using an artificial Sun consisting of 27 lamps. The water temperatures have been measured at various locations in the system. In the theoretical study, transient performance of the system is predicted by solving the mathematical model consisting of energy balance equations written for each control volume comprising one length of pipe. These equations are converted to finite difference form and then solved by a personal computer. The experimental results have been compared with the numerical model and a good agreement has been found between the experimental results and the theoretical predictions.

Energy analysis of porous water ice under space-simulated conditions: results from the KOSI-8 experiment

A sublimation experiment (KOSI-8) was performed on a pure, porous water ice sample under conditions of low pressure and temperature and insolation by an artificial sun. Temperatures within the sample, gas flux from the surface, mass loss of the sample during the experiment and the irradiation input were measured for a detailed analysis of energy flow. A main feature of the analysis was the development of a convex temperature profile along the middle axis of the sample as a consequence of heat transfer by water vapor flow. The amount of the energy transport by the water was about 40% of the total heat flux available for heating the sample. To interpret the unusually high temperatures measured a few millimeters below the surface, it is assumed that the radiative energy input penetrates about 3 mm into the sample (solid-state greenhouse effect). To trace the flow of water vapor during the experiment, the top 10 mm of the ice was enriched with 10% HDO. Ice samples for isotopic analyses were taken from the post-insolation surface and from various depths. Isotopic enrichment was observed only at the surface, corresponding to a 2.3% admixture of recondensed vapor from the initially 10-mm-thick surface layer, to a depth of 19 mm below the original surface. No isotopic enrichment could be detected below a crust that had formed, i.e. 57 mm below the original surface. During the experiment an average of about 16 mm of the ice eroded from the surface. The weight of the sample was continuously monitored and a total mass loss of 1.75 ± 0.05 kg was measured between start and end of insolation. A comparison of the power balance of a pure, porous ice sample and an ice/dust sample shows that in either case the net flux of energy available for sublimation and warming of the sample is less than 20% of the insolation. In the case of a pure ice sample, most of the irradiation is reflected due to the high albedo; in the case of an ice/dust sample, thermal reradiation of the sample is very high because of the high surface temperatures, ≈ 350 K.

Counting Neutrinos from an 'Artificial Sun'

Counting Neutrinos from an 'Artificial Sun'

Measurement of the volatile component in particles emitted from an ice/dust mixture

A set of novel instruments has been developed to measure the volatile component of solid particles emitted from the surface of an insolated ice/dust mixture (“sample”). To detect such particles a pressure gauge is mounted inside a volume which has a narrow tube placed on top for particles to enter. The experiments are positioned about 0.5 m away from and below the sample. Particles, after falling through the tube are collected in a heated cup, ices evaporate and produce a gas pulse inside the volume. The pressure, registered by the gauge, will decrease with a time constant of about 0.4 s. In some instruments the single cup is replaced by a multiple cup collector. In recent comet simulation experiments (KOSI 5 and KOSI 6) with ice/dust mixtures over 1200 gas pulses were observed. They fall into two categories: (a) short pressure pulses with a fast rising amplitude followed by the expected exponential decay, and (b) long pulses with rise times of about one second and several tens of seconds decay times. The former pulses are associated with ice particles, whereas the latter pulses are attributed to skeleton silicate grain agglomerates which have ice imbedded in them. The estimated mass distribution ranges from 2 × 10−10 g to 10−5 g of volatile material. Ice particles are emitted at maximum rate immediately at turn‐on of the artificial sun and drop to much lower frequencies within less than one hour. “Mineral” particles, in contrast, reach their maximum frequency later, with their abundance also decreasing but less pronounced. Since gas emission varies very little while the ice particle frequency drops rapidly, it appears that the particle rate is not controlled by the gas flux's drag force, but by the availability of particles suited for acceleration at the surface of the sample.

Hydrocarbon Exploration through Remote Sensing and Field Work in the Onshore Eastern Papuan Fold Belt, Gulf Province, Papua New Guinea: ABSTRACT

Over the years several types of remote sensing surveys have been acquired of the Eastern Papuan Fold Belt, in the Gulf Province of Papua New Guinea. These include aerial photographs, Landsat Multispectral Scanner (MSS), and Synthetic Aperture Radar (SAR). Each has been used by Petro-Canada Inc. for interpreting the geologic structure and stratigraphy of onshore hydrocarbon prospects. Analysis of available remotely sensed imagery reveals greater structural complexity than is shown on published geologic maps. Foremost among the images is SAR because of its low, artificial sun angle. Hence, a comprehensive view of the area has been acquired revealing many structural elements previously not appreciated. A distinct difference in structural style is found between the northern and southern segment of the Eastern Papuan fold belt in the study area. The northern segment shows discontinuous, open folds with widely separated anticlines set in featureless valleys. The southern segment is tightly folded, possessing few anticlines and synclines clearly recognizable on the imagery. However, structural components can be traced easily for tens of miles. Recent field work supports an SAR structural interpretation suggesting most, if not all, anticlines in the northern segment are overturned. The combination of remote sensing and field work proved invaluablemore » in understanding the fold belt tectonics and has aided considerably in the selection of drilling locations.« less

‘Kosi’ comet simulation experiment at DFVLR: Sample preparation and the evolution of the 18O/ 16O and the D/H ratio in the icy component

Based on the results of the observation campaign of comet Halley, ice-mineral mixtures were produced with a mean density of 300 to 500 kg/m 3 and an albedo between about 0.05 and 0.2. The samples were prepared by spraying different water-mineral mixtures into liquid nitrogen. As a propellant we used nitrogen or carbon dioxide. with carbon dioxide we obtained ices with two components (H 2O and CO 2). Sample preparation methods from the gas phase are under development. During the freezing a slight enrichment in 18O and deuterium was produced. After the iradiation with an artificial sun, the uppermost layers of the sample showed an important enrichment of heavy isotopes. This was also observed in the lowest layers whereas the intermediate layer showed no isotope fractionation.

Dynamic modelling and verification of a flat-plate solar collector

In the modelling of flat-plate solar collectors the dynamic effects have often been neglected. But because the solar collector is inherently exposed to variable weather conditions, its dynamics may be important to the design and control. It is demonstrated that it is not necessary to ignore the dependence of the various temperatures on the location in the direction of flow (which is often done to avoid complications) provided the model is developed in the frequency domain. The linearised model has been verified in the frequency domain by means of a least squares estimator. The verification was performed with a part of a full-size collector, as has been applied in some solar houses, and an artificial sun. It is concluded from the results of the verification that the developed model describes the collector dynamics quite satisfactorily. The differences between the theoretical and estimated heat resistances was about 10 per cent. The verification and estimation procedure proved to be a useful tool for comparing various collectors because the collector has to be fitted with only two temperature sensors. It is shown that the simple models have been discussed in the literature give responses which are not representative of the collector's dynamics. For well-designed collectors a simplified model is derived. Finally, some desirable sampling rates are given.

Operant studies of pigeon orientation and navigation

Pigeons were trained to make conditioned responses from which could be judged their ability to make discriminations relevant to sun-navigation and their use of alternative navigational information derived from the sun. Using an artificial sun, discrimination thresholds determined for absolute altitude and azimuth, rate-of-change of altitude and azimuth and time of day were compatible with certain hypotheses of sun-navigation. Experiments in which pigeons were trained to respond in the homeward direction, either under an artificial sun in the laboratory or under the real sun in field conditions, provided support for some components of sun-navigation only. These results are discussed in relation to recent evidence that pigeon navigation utilizes other types of cue.