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At least 1,027 records · Page 57Linked to original sources
PubMed1992

Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540.

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.

Animals↗
PubMed2000

World cup soccer players tend to be born with sun and moon in adjacent zodiacal signs.

The ecliptic elongation of the moon with respect to the sun does not show uniform distribution on the birth dates of the 704 soccer players selected for the 1998 World Cup. However, a uniform distribution is expected on astronomical grounds. The World Cup players show a very pronounced tendency (p = 0.00001) to be born on days when the sun and moon are in adjacent zodiacal signs.

Astrology↗
PubMed1999

Astrobiology: exploring the origins, evolution, and distribution of life in the Universe.

The search for the origins of life and its presence beyond Earth is strengthened by new technology and by evidence that life tolerates extreme conditions and that planets are widespread. Astrobiologists learn how planets develop and maintain habitable conditions. They combine biological and information sciences to decipher the origins of life. They examine how biota, particularly microorganisms, evolve, at scales from the molecular to the biosphere level, including interactions with long-term planetary changes. Astrobiologists learn how to recognize the morphological, chemical, and spectroscopic signatures of life in order to explore both extraterrestrial samples and electromagnetic spectra reflected from extrasolar planets.

Biological Evolution↗
PubMed2005

Season, sun, sex, and cervical cancer.

INTRODUCTION: Sunlight's UV B component, a known cellular immunosupressant, carcinogen, and activator of viral infections, is generally seasonally available. Venereal human papillomavirus (HPV) transmission, at least in part, causes cervical cancer. We have previously inspected the monthly rates of venereal HPV infection and sunlight fluency in Southern Holland over 16 consecutive years. Both peak in August with at least 2-fold seasonality. The amount of available sunlight and the rate of Papanicolaou (Pap) smear screen-detected HPV are positively correlated. We now investigate whether premalignant and malignant cervical epithelial changes are also seasonal and related to seasonal sunlight fluency. METHODS: We have studied >900,000 consecutive, serially independent, interpretable screening Pap smears obtained by a single cervical cancer screening laboratory in Leiden, Holland, during a continuous 16-year span from 1983 through 1998. The average monthly rates of premalignant and malignant epithelial change were inspected and the annual patterns contrasted to the annual pattern of sunlight fluency at this global location and to monthly average HPV infection rate. Because HPV is venereally transmitted, Dutch seasonal sexual behavior was evaluated by assessment of the annual pattern of Dutch conception frequency as a competing cause for cervical cancer seasonality. RESULTS: (a) Twice as many premalignant and malignant epithelial changes were found among Pap smears obtained in the summer months, with an August peak concurrent with histopathologic evidence of HPV infection and sunlight fluency in Southern Holland. (b) Monthly sunlight fluency is correlated positively with both the monthly rates of Pap smear-detected cervical epithelial dysplasia and carcinomatous histopathology, as well as HPV. (c) Conception frequency, in this location, peaks in Spring not summer, and has a 4.8% annual amplitude. CONCLUSIONS: (a) Cervical epithelial HPV infection and HPV-induced cervical epithelial dysplasia and carcinomatous change may each be novel sun exposure risks and thereby behaviorably avoidable. (b) Because screening Pap smears uncover many abnormalities that resolve spontaneously (false positives), these data may argue for screening and follow-up Pap smear examinations in seasons other than summer in the Northern Hemisphere, to diminish the false-positive smear rate. Global data are available to confirm and further test each of these conclusions.

Adult↗
PubMed2006

Structure of high-performance evaporators for space application.

A new structure of cold plates, where an unheated auxiliary channel is installed to supply liquid directly to the bottom of coalesced flattened bubbles in a narrow heated channel, is tested to investigate the increase in critical heat flux. Assuming the application to the laser solar power system, a large heating surface with a length of 150 mm in the flow direction is employed, and a narrow channel structure is adopted to reduce the size of cold plates, where the gap sizes are selected as 5 mm and 2 mm. Experiments are performed for water as a test liquid at inlet subcooling of 15 K under near atmospheric pressure. Inlet liquid velocity is varied from 0.065 m/s to 0.6m/s for the upward flow on ground. A value of critical heat flux of 2.2 x 10(6) W/m2 is obtained for 5-mm gap size at the inlet velocity of 0.2 m/s. At low liquid flow rate, the structure realizes the CHF values larger by 2.5 times than those for the normal heated channel without additional liquid supply. A new method to evaluate the performance of cold plates is proposed to take account of the variation in the size of heating surface, inlet liquid velocity, and subcooling that influence the CHF values. The validity of the proposed structure of the cold plate for the increase in critical heat flux is confirmed.

Journal Article↗
PubMed2005

Effect of vitamin D replacement on musculoskeletal parameters in school children: a randomized controlled trial.

BACKGROUND: Despite the high prevalence of hypovitaminosis D in children and adolescents worldwide, the impact of vitamin D deficiency on skeletal health is unclear. METHODS: One hundred seventy-nine girls, ages 10-17 yr, were randomly assigned to receive weekly oral vitamin D doses of 1,400 IU (equivalent to 200 IU/d) or 14,000 IU (equivalent to 2,000 IU/d) in a double-blind, placebo-controlled, 1-yr protocol. Areal bone mineral density (BMD) and bone mineral content (BMC) at the lumbar spine, hip, forearm, total body, and body composition were measured at baseline and 1 yr. Serum calcium, phosphorus, alkaline phosphatase, and vitamin D metabolites were measured during the study. RESULTS: In the overall group of girls, lean mass increased significantly in both treatment groups (P < or = 0.05); bone area and total hip BMC increased in the high-dose group (P < 0.02). In premenarcheal girls, lean mass increased significantly in both treatment groups, and there were consistent trends for increments in BMD and/or BMC at several skeletal sites, reaching significance at lumbar spine BMD in the low-dose group and at the trochanter BMC in both treatment groups. There was no significant change in lean mass, BMD, or BMC in postmenarcheal girls. CONCLUSIONS: Vitamin D replacement had a positive impact on musculoskeletal parameters in girls, especially during the premenarcheal period.

Adolescent↗
PubMed2000

Sun-compass orientation in homing pigeons: compensation for different rates of change in azimuth?

Birds using their sun compass must compensate for the apparent movement of the sun with the help of their internal clock. The movement of the sun is not uniform, being much faster around noon than near sunrise and sunset. If the sun-compass mechanisms are not adjusted to these variations, considerable errors might arise. To learn whether birds are able to take the different rates of sun azimuth change into account, we subjected homing pigeons to a 4 h fast clock-shift. The experiments were performed near Auckland, New Zealand, at a latitude of 37 degrees S, where the expected deflections for a 4 h shift in summer vary from less than 40 degrees to more than 120 degrees, depending on time of day. One group of birds was released just after sunrise or during the corresponding period in the afternoon when the expected deflections were minimal, the other group during late morning when they were maximal. The different sizes of the observed deflections - between 26 degrees and 51 degrees in the first group, and between 107 degrees and 153 degrees in the second group - clearly show that the birds' compensation mechanisms are closely tuned to the varying rates of change in sun azimuth. The results suggest that pigeons have a rather precise internal representation of the sun curve, which makes the avian sun compass a highly accurate mechanism of direction finding.

Animals↗
PubMed2002

The sun compass of the sandhopper Talitrus saltator: the speed of the chronometric mechanism depends on the hours of light.

Experiments on solar orientation were conducted with adult amphipods (Talitrus saltator) subjected to a reduction and/or phase shift of the hours of light (L) or dark (D) with respect to the natural photoperiod: 15 h:9 h L:D (controls), 15 h:9 h inverted (i.e. phase-shifted by 12 h and tested with the sun during the subjective night), 4 h:20 h, 20 h:4 h inverted. The sandhoppers were released in a confined environment, and individual orientation angles were recorded. The results confirm the continuous operation, through the entire 24-h period, of a chronometric mechanism of compensation for apparent solar motion. They show excellent agreement with a recently proposed model of compensation for the sun at constant (not differential) speed and they demonstrate a dependence of the speed of the chronometric mechanism on the L:D ratio in the 24-h period.

Amphipoda↗
PubMed2005

Living in low-latitude regions in the United States does not prevent poor vitamin D status.

Vitamin D deficiency may occur throughout the life cycle, and is described as an unrecognized epidemic. The risk of deficiency may be increased by darker skin color, overweight and obesity, and low vitamin D intakes, while living in low latitudes and not using protective measures against the sun may decrease risk. However, a recent study reported that Hispanic adults living in the high-sun-exposure area of Miami have a high prevalence of poor vitamin D status in the winter, suggesting that living at low latitudes alone does not protect against vitamin D deficiency. The vitamin D status of Hispanics needs further investigation, given the large number of Hispanics living in southern regions of the United States and the emerging role of vitamin D in numerous health disorders.

Florida↗
PubMed1994

Space proton transport in one dimension.

An approximate evaluation procedure is derived for a second-order theory of coupled nucleon transport in one dimension. An analytical solution with a simplified interaction model is used to determine quadrature parameters to minimize truncation error. Effects of the improved method on transport solutions with the BRYNTRN data base are evaluated. Comparisons with Monte Carlo benchmarks are given. Using different shield materials, the computational procedure is used to study the physics of space protons. A transition effect occurs in tissue near the shield interface and is most important in shields of high atomic number.

Computer Simulation↗
PubMed2005

Psychophysical study of the visual sun location in pictures of cloudy and twilight skies inspired by Viking navigation.

In the late 1960s it was hypothesized that Vikings had been able to navigate the open seas, even when the sun was occluded by clouds or below the sea horizon, by using the angle of polarization of skylight. To detect the direction of skylight polarization, they were thought to have made use of birefringent crystals, called "sun-stones," and a large part of the scientific community still firmly believe that Vikings were capable of polarimetric navigation. However, there are some critics who treat the usefulness of skylight polarization for orientation under partly cloudy or twilight conditions with extreme skepticism. One of their counterarguments has been the assumption that solar positions or solar azimuth directions could be estimated quite accurately by the naked eye, even if the sun was behind clouds or below the sea horizon. Thus under partly cloudy or twilight conditions there might have been no serious need for a polarimetric method to determine the position of the sun. The aim of our study was to test quantitatively the validity of this qualitative counterargument. In our psychophysical laboratory experiments, test subjects were confronted with numerous 180 degrees field-of-view color photographs of partly cloudy skies with the sun occluded by clouds or of twilight skies with the sun below the horizon. The task of the subjects was to guess the position or the azimuth direction of the invisible sun with the naked eye. We calculated means and standard deviations of the estimated solar positions and azimuth angles to characterize the accuracy of the visual sun location. Our data do not support the common belief that the invisible sun can be located quite accurately from the celestial brightness and/or color patterns under cloudy or twilight conditions. Although our results underestimate the accuracy of visual sun location by experienced Viking navigators, the mentioned counterargument cannot be taken seriously as a valid criticism of the theory of the alleged polarimetric Viking navigation. Our results, however, do not bear on the polarimetric theory itself.

Computer Graphics↗
PubMed2005

Radiant heat and thermal comfort in vehicles.

Infrared-reflective (IRR) treatment of automotive glass has been shown to reduce air temperature in vehicle cabins, thereby increasing fuel economy and occupant comfort. Its effect on radiant heat, however, may augment these benefits. In this study, the hypothesis that radiant heat affects subjective comfort ratings in a vehicle was tested. IRR films were systematically applied to the driver-side window of an outdoor stationary vehicle. In Phase 1, cabin air temperature was controlled while participants rated their thermal comfort. In Phase 2, air temperature was adjusted according to participants' responses. Results in Phase 1 showed that the IRR treatment improved thermal comfort on the left forearm, which was exposed to direct solar irradiance, but not whole-body thermal comfort. In Phase 2, participants indicated that they were comfortable at a higher air temperature (mean of 2.5 degrees F [1.4 degrees C]) with the IRR treatment than in the untreated condition. The results indicate that reducing radiant heat via IRR treatment affects subjective assessments of thermal comfort and allows occupants to maintain the same level of comfort in a warmer vehicle cabin. Applications of this research include future implementations of IRR treatment on automotive glass that may lead to greater fuel economy savings and occupant comfort than have previously been estimated.

Adolescent↗
PubMedDate not supplied

Biological monitoring of solar UV radiation at 17 sites in Asia, Europe and South America from 1999 to 2004.

A small and robust dosimeter for determining the biologically effective dose of ambient UV radiation has been developed using UV-sensitive mutant spores of Bacillus subtilis strain TKJ6312. A membrane filter with four spots of the spores was snapped to a slide mount. The slide was wrapped and covered with two or more layers of polyethylene sheet to protect the sample from rain and snow and to reduce monthly-cumulative doses within the measurable range. From 1999, monthly data were collected at 17 sites for more than 1 year, and data for 4 to 6 consecutive years were obtained from 12 sites. Yearly total values of the spore inactivation dose (SID) ranged from 3200 at subarctic Oulu to 96 000 at tropical Denpasar, and the mean yearly values of SID exhibited an exponential dependence on latitude in both hemispheres with a doubling for about every 14 degrees of change. During the observation period, increasing trends of UV doses have been observed at all sites with more than 5 years of data available. Year-to-year variations at high and middle latitude sites are considered due mostly to climatic variation. At three tropical sites, negative correlations between the yearly doses and the column ozone amounts were observed. The results verified the applicability of spore dosimetry for global and long-time monitoring of solar UV radiation, in particular at tropical sites where no monitoring is taking place.

Asia↗
PubMedDate not supplied

Measurements of the UVR protection provided by hats used at school.

The importance of protection against solar ultraviolet radiation (UVR) in childhood has lead to SunSmart policies at Australian schools, in particular primary schools, where children are encouraged and in many cases required to wear hats at school. Hat styles change regularly and the UVR protection provided by some of the hat types currently used and recommended for sun protection by the various Australian state cancer councils had not been previously evaluated. The UVR protection of the hats was measured using UVR sensitive polysulphone film badges attached to different facial sites on rotating headforms. The sun protection type hats included in this study were broad-brimmed hats, "bucket hats" and legionnaires hats. Baseball caps, which are very popular, were also included. The broad-brimmed hats and bucket hats provided the most UVR protection for the six different sites about the face and head. Legionnaires hats also provided satisfactory UVR protection, but the caps did not provide UVR protection to many of the facial sites. The highest measured UVR protection factors for facial sites other than the forehead were 8 to 10, indicating that, while some hats can be effective, they need to be used in combination with other forms of UVR protection.

Australia↗
PubMedDate not supplied

Radiation exposure predictions for short-duration stay Mars missions.

The human radiation environment for several short-duration stay manned Mars missions is predicted using the Mission Radiation Calculation (MIRACAL) program, which was developed at NASA Langley Research Center. This program provides dose estimates for galactic cosmic rays (GCR) and large and ordinary solar proton flare events for various amounts of effective spacecraft shielding (both operational and storm shelter thicknesses) and a given time history of the spacecraft's heliocentric position. The results of this study show that most of the missions can survive the most recent large flares (if they were to occur at the missions' perihelion) if a 25 g/cm2 storm shelter is assumed. The dose predictions show that missions during solar minima (when solar flare activity is the lowest) are not necessarily the minimum dose cases, due to increased GCR contribution during this time period. The direct transfer mission studied has slightly lower doses than the outbound Venus swingby mission [on the order of 10-20 centi-Sieverts (cSv) lower], with the greatest dose differences for the assumed worst case scenario (when the large flares occur at perihelion). The GCR dose for a mission can be reduced by having the crew spend some fraction of its day nominally in the storm shelter (other than during flare events).

Bone Marrow↗