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At least 937 records · Page 52Linked to original sources
PubMed2003

Reevaluation of headspace solid-phase microextraction and gas chromatography-mass spectrometry for the determination of methyl tert-butyl ether in water samples.

A headspace solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) method has been reevaluated for the determination of methyl tert-butyl ether (MTBE) in water. Factors affecting method performance were examined. The internal standard, deuterated MTBE, is necessary because it allows normalization of the calibration since the deuterated MTBE and MTBE experience the same extraction efficiency. The method detection limit was 6.6 ng/l, with a linear range up to 160 microg/l. SPME extraction efficiency and detection sensitivity for MTBE decreased in the presence of gasoline matrix. However, reliable measurement of MTBE was possible in the background matrix concentration of 0.97 mg/l gasoline using deuterated internal standard. Reproducibility was 4.5% at the spiking level of 47 ng/l. The average recoveries of MTBE in spiked fountain water, tap water, and snow at 60 ng/l and in spiked rainwater at 580 ng/l ranged from 101 to 105%. The method was successfully applied to the analysis of trace levels of MTBE in various water samples, including rain and snow samples collected in Albany, NY, USA.

Calibration↗
PubMed2005

Radiative habitable zones in martian polar environments.

The biologically damaging solar ultraviolet (UV) radiation (quantified by the DNA-weighted dose) reaches the martian surface in extremely high levels. Searching for potentially habitable UV-protected environments on Mars, we considered the polar ice caps that consist of a seasonally varying CO2 ice cover and a permanent H2O ice layer. It was found that, though the CO2 ice is insufficient by itself to screen the UV radiation, at approximately 1 m depth within the perennial H2O ice the DNA-weighted dose is reduced to terrestrial levels. This depth depends strongly on the optical properties of the H2O ice layers (for instance snow-like layers). The Earth-like DNA-weighted dose and Photosynthetically Active Radiation (PAR) requirements were used to define the upper and lower limits of the northern and southern polar Radiative Habitable Zone (RHZ) for which a temporal and spatial mapping was performed. Based on these studies we conclude that photosynthetic life might be possible within the ice layers of the polar regions. The thickness varies along each martian polar spring and summer between approximately 1.5 and 2.4 m for H2O ice-like layers, and a few centimeters for snow-like covers. These martian Earth-like radiative habitable environments may be primary targets for future martian astrobiological missions. Special attention should be paid to planetary protection, since the polar RHZ may also be subject to terrestrial contamination by probes.

Arctic Regions↗
PubMed2005

Precipitation scavenging of 7Be and 137Cs radionuclides in air.

Atmospheric depositional fluxes of the naturally occurring 7Be of cosmogenic origin and 137Cs from fallout of the Chernobyl accident were measured over a 6-year period (January 1987-December 1992) at Thessaloniki, Greece (40 degrees 38'N, 22 degrees 58'E). Total precipitation accumulation during 1987-1992 varied between 33.7 cm and 65.2 cm, reflecting a relatively dry (precipitation-free) climate. The activity concentrations of 7Be and 137Cs in rainwater depended on the precipitation rate, being higher for low precipitation rates and lesser for high precipitation rates. 137Cs was removed by rain and snow more efficiently than 7Be. Snowfall was more efficient than rainfall in removing the radionuclides from the atmosphere. The annual bulk depositional fluxes of 7Be varied between 477 and 1133 Bq m(-2) y(-1) and this variability was attributed to the amount of precipitation and the variations of the atmospheric concentrations of 7Be. The annual bulk depositional fluxes of 137Cs showed a significant decrease over time from 1987 to 1992, resulting in a removal half-life of 1.33 years. The presence of 137Cs in air, and therefore in rainwater and snow, long after the Chernobyl accident (26 April 1986) was mainly due to the resuspension process. The normalized depositional fluxes of both radionuclides showed maximal values during the spring season where the maximum amount of precipitation occurred. The relatively high positive correlation between 7Be and 137Cs normalized depositional fluxes indicates that the scavenging process of local precipitation controlled the fluxes of both radionuclides. The dry depositional flux of 7Be was less than 9.37% of total (wet and dry) depositional flux. The fraction of dry-to-total depositional flux of 137Cs was much higher than that of 7Be, due to the resuspended soil.

Air Pollutants, Radioactive↗
PubMed2004

Recycling of pathogenic microbes through survival in ice.

Viable microorganisms (e.g. fungi, bacteria, Archaea and viruses) are distributed by wind over great distances, including globally. Microbes may settle out of the atmosphere or may be incorporated into fog, rain, sleet, hail, or snow. These organisms fall into lakes, streams, oceans, or onto the land or glaciers. When they become incorporated into environmental ice (e.g. glaciers, ice sheets, and snow), those that survive freezing and thawing may persist for years, centuries, millennia, or longer. Once they melt from the ice, they may enter contemporary populations. This mixing of ancient and modern genotypes (i.e. temporal gene flow, or what we term "genome recycling") may lead to a change of allele proportions in the population, which may have effects on mutation rates, fitness, survival, pathogenicity and other characteristics of the organisms. Pathogenic microbes that survive freezing and thawing (e.g. influenza viruses, polioviruses, caliciviruses and tobamoviruses) can remain in these icy reservoirs long enough to avoid resistance mechanisms of the hosts, thereby conveying a selective advantage to these pathogens over those that cannot survive in ice. Ice is an abiotic reservoir of microbes that has been ignored in surveillance activities for human diseases.

Bacteria↗
PubMed2004

Application of 252Cf-PDMS to characterize airborne particles deposited in an Antarctic glacier.

The aim of this study is to apply the (252)Cf-PDMS (plasma desorption mass spectrometry) technique to characterize particles deposited in ice samples. This technique allows identification of molecular ions, even large molecules, desorbed from the sample surface, in contrast with PIXE (particle induced X-ray emission) or EDS (energy dispersive spectrometry). Two shallow snow cores obtained from different glacial drainage basins on King George Island ice cap, South Shetland Islands (Antarctica), were analyzed by PDMS. The chemical compounds identified in the ice mass spectra show that the particle contents of both samples were statistically different, indicating a non-homogeneous spatial deposition distribution for the deposited particles. The analysis of the ice mass spectra suggests some possible sources for the airborne particles. The mass spectra of ice samples collected at a site exposed directly to air masses coming from the Drake Passage show a significant contribution of particles from crustal and anthropogenic sources. However, the mass spectra of ice samples taken from a site on a slope towards a local inlet point out a high influence of marine aerosol. Therefore, it was concluded that particles deposited onto the ice cap were attributable to different aerosol sources, besides long-range atmospheric transport. The (252)Cf-PDMS technique can be considered a powerful tool for studies of snow and ice samples, providing important information for understanding the global atmospheric transport and deposition of airborne particles.

Journal Article↗
PubMed2004

A phylogenetically controlled test of hypotheses for behavioral insensitivity to testosterone in birds.

In most male birds that exhibit paternal care, extending the spring testosterone (T) peak throughout the breeding season reduces nestling provisioning. However, in some species, this trade-off between high T and expression of paternal care is absent. For example, during some or all of the nestling period, T did not affect paternal behavior in Male Lapland longspurs (Calcarius lapponicus), chestnut-collared longspurs (Calcarius ornatus), and great tits (Parus major). Two ecological constraints have been hypothesized to drive insensitivity to T after eggs hatch: (1) a short breeding season that limits breeding opportunities, and (2) a need for paternal care to ensure reproductive success. However, because two of the three species that exhibit T insensitivity are closely related, potential phylogenetic confounds limit determination of which, if either, factor constrains some males to T insensitivity. We examined the effects of supplementary T on paternal behavior in the Snow Bunting (Plectrophenax nivalis), a member of the monophyletic Calcarius/Plectrophenax clade. Male Snow Buntings are constrained to a short breeding season, but paternal care is not essential for survival of nestlings. We administered exogenous T during the parental phase to mimic the early spring T peak. T treatment increased song rates and interfered with paternal behavior such that nestlings of T-implanted males grew more slowly than controls. Our data suggest that T insensitivity in this clade is related to relatively recent constraints of the breeding environment (i.e., not simply common ancestry) and that the necessity of paternal care in some species may be a strong selective factor driving behavioral insensitivity to T during the parental phase.

Androgens↗
PubMed1997

Tractor-trailer crashes in Indiana: a case-control study of the role of truck configuration.

Studies of the crash experience of tractors pulling multiple trailers have reached different conclusions concerning the relationship of truck configuration to crash risk. A previous case-control study found a significant increase in crash risk for double-trailer trucks in the state of Washington. The present case-control study was done of tractor-trailers crashing on Indiana interstates during November 1989-March 1991. Controls were obtained for 25% of the crash sites and were all tractor-trailers passing the crash sites during a traffic observation session one to four weeks following a crash on the same day of the week for 30 minutes at the same time of day. Logistic regression identified day of week, time of day, urban/rural area, and specific highway as significant predictors of controls' truck configuration. This model was applied to the cases to estimate the expected number of double-trailer cases. For all crashes combined, no increased crash risk was observed for doubles (Standardized Crash Ratio (SCR) = 83). Doubles were significantly underinvolved in multiple-vehicle crashes (SCR = 74), crashes on dry roads (SCR = 61), and crashes on wet (other than snow, ice, or slush) roads (SCR = 54). Doubles were significantly overinvolved in crashes on roads with snow, ice, or slush (SCR = 153). Because truck configuration was highly associated with driver age and work operation attributes among trucks in crashes, the absence of control data on these potential confounders precluded definitive assessment of the intrinsic risk of multiple versus single-trailer vehicles.

Accidents, Traffic↗
PubMed2000

Pedestrians on slippery surfaces during winter--methods to describe the problems and practical tests of anti-skid devices.

Every year there are thousands of pedestrians in Sweden who are injured because of slippery pavements and roadways. Using an appropriate anti-skid device may reduce the risk of slips and falls on ice and snow. Methods to describe functional problems in walking on different slippery surfaces during winter have been developed as rating scales for evaluating walking safety and walking balance and an observation method to observe posture and movements during walking. Practical tests of all 25 anti-skid devices on the market in Sweden were carried out on different slippery surfaces; gravel, sand, salt, snow and ice. The anti-skid devices were described according to the subjects' perception of walking safety, walking balance and priority for own use. The postures and movements during walking were analysed by an expert physical therapist. The wholefoot device 'studs' was perceived as the best according to walking safety and walking balance and had the highest priority for own use.

Accidental Falls↗
PubMed2002

Development of capillary electrophoresis for the determination of metal ions using mixed partial and complete complexation techniques.

A new capillary electrophoretic (CE) method was developed for the selective and sensitive determination of common metal ions. The proposed method is based on conventional CE separation of metal cations followed by complete complexation of separated analytes with 1,10-phenanthroline using the zone-passing technique. This approach combines both partial and complete complexation modes and, thus, enables rapid, selective, efficient separation together with sensitive direct UV detection of metal species. The optimal conditions for the separation and derivatization reaction were established by varying type of electrolyte, electrolyte pH, introduction time and concentration of 1,10-phenanthroline. The optimized separations were carried out in 50 mmol l(-1) glycolic acid electrolyte (pH 6.0 with imidazole) using direct UV detection at 254 nm. Five common metal cations (Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) were separated in less than 4 min. The proposed system was applied to the determination of Fe(II) and Zn(II) in snow samples. The recovery tests established for snow samples were within the range 100+/-12%.

Electrophoresis, Capillary↗
PubMed2003

Extreme marginal donor: severe hypothermia as a rare preservation condition for explantable organs--a case report.

UNLABELLED: The progressive increase in patients with end stage liver disease has lengthend the waiting- list for liver transplantation. Unfortunately this has not been followed by a suitable increase in the number of donors. The expanding "donor pool" has required use of "marginal" donors (ICU stay > 10 days, sepsi; steatosis > 30-40%, hypernatremia > 155 mmol/L, inotropic drugs). We report the case of a skier who remained for more than 1 hour in cardio-respiratory arrest under the snow; the 49-year-old women was extracted from the snow after 1 hour and 12 minutes and found to be asystolic, fixed pupils and deep hypothermia (27.2 degrees C). After cardiopulmonary resuscitation, partial cardio-respiratory activity was re-established. In the ICU severe hypothermia (26.7 degrees C) was treated with extracorporeal circulation until a re-establishment of satisfactory cardio-circulatory conditions was obtained. Unfortunately cerebral anoxic cerebral death was established and multiorgan procurement performed 3 days later. After liver transplantation into a 59 year-old patient with PNC-C was performed. The course was uneventful and the patient was discharged on the 19th postoperative day. CONCLUSIONS: Organ procurement from donors involved in accidental traumatic events with cardio-respiratory arrest and hypothermia, is similar to the non-heart-beating donor (NHBD) condition. Correct cardiopulmonary resuscitation and the use of extracorporeal circulation for gradual restoration of body temperature are necessary for optimal organ perfusion. In the present case the anoxic insult induced by the cessation of the cardio-respiratory function, was probably mitigated (if not even annulled) by the hypothermia.

Female↗
PubMed2003

Springtime depletion of mercury in the European Arctic as observed at Svalbard.

This study was carried out to see whether the geographical extent of the mercury depletion events (MDEs), first seen at Alert in the Canadian High Arctic, is also covering Svalbard. Another goal was to determine the main reaction products from the MDE and their fate. Gaseous elemental mercury (GEM), total particulate mercury (TPM), reactive gaseous mercury (RGM) and total mercury in surface snow have been measured at the Zeppelin mountain during 2000. GEM has been measured with a high time resolution automatic monitor (Tekran 2537A) based on CV-AFS, TPM was sampled/measured using high volume samplers/CV-AFS and RGM was sampled with annular denuders and measured by CV-AFS (Gardis Hg-monitor). During spring of 2000, in the three-month period following polar sunrise, there were several episodic depletions in GEM concentration correlating well with the depletion of surface ozone. Measurements of RGM and TPM showed higher concentrations of these mercury species during the depletion period than during the rest of the year. Total mercury in surface snow showed a distinct increase from the polar night to the Arctic spring. MDEs are caused by the specific chemical and physical conditions observed in the Arctic during spring. GEM is oxidised and converted to more reactive forms (RGM and/or TPM), which have considerably higher deposition velocities than elemental mercury, leading to an overall enhanced deposition flux of mercury.

Air Movements↗
PubMed2001

Science and humanities: across two cultures and into science studies.

C.P. Snow's articulation of a two-culture divide rested on a particular view of science that has been elaborated and superseded by interdisciplinary science studies. Thus, comparisons of the 'science wars' of recent years to the Snow-Leavis controversy fail to recognize basic structural differences between the two sets of debates. In this article, I present these differences and offer some views of what has changed in the intervening years.

Cross-Cultural Comparison↗
PubMed1989

Mountaineering and rock-climbing injuries in US national parks.

Mountaineering and rock climbing have become increasingly popular in recent years and involve an estimated 100,000 participants; accordingly, the number of climbing-related injuries has also increased. We analyzed 127 climbing-related injuries reported to the US National Park Service in 1981 and 1982, 36 (28%) of which were fatal. Falls accounted for 75% of all climbing-related injuries; median length of fall was 91 m for fatal injuries and 9 m for nonfatal injuries. The majority of injuries (69%) occurred while ascending. Falls on snow or ice were longer than falls on rock, and injuries on snow or ice were more likely to be fatal. We discuss considerations and strategies for the prevention of climbing-related injuries. A new conceptual model suggests that the methods of traditional mountaineering safety programs may be of limited efficacy in further reducing the number of climbing-related injuries.

Adult↗
PubMed2003

Radionuclides deposition over Antarctica.

A detailed and comprehensive map of the distribution patterns for both natural and artificial radionuclides over Antarctica has been established. This work integrates the results of several decades of international programs focusing on the analysis of natural and artificial radionuclides in snow and ice cores from this polar region. The mean value (37+/-20 Bq m(-2)) of (241)Pu total deposition over 28 stations is determined from the gamma emissions of its daughter (241)Am, presenting a long half-life (432.7 yrs). Detailed profiles and distributions of (241)Pu in ice cores make it possible to clearly distinguish between the atmospheric thermonuclear tests of the fifties and sixties. Strong relationships are also found between radionuclide data ((137)Cs with respect to (241)Pu and (210)Pb with respect to (137)Cs), make it possible to estimate the total deposition or natural fluxes of these radionuclides. Total deposition of (137)Cs over Antarctica is estimated at 760 TBq, based on results from the 90-180 degrees East sector. Given the irregular distribution of sampling sites, more ice cores and snow samples must be analyzed in other sectors of Antarctica to check the validity of this figure.

Air Movements↗
PubMed2003

Modeling coupled interactions of carbon, water, and ozone exchange between terrestrial ecosystems and the atmosphere. I: model description.

A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology. FORFLUX consists of four interconnected modules-a leaf photosynthesis model, a canopy flux model, a soil heat-, water- and CO2- transport model, and a snow pack model. Photosynthesis, water-vapor flux and ozone uptake at the leaf level are computed by the LEAFC3 sub-model. The canopy module scales leaf responses to a stand level by numerical integration of the LEAFC3model over canopy leaf area index (LAI). The integration takes into account (1) radiative transfer inside the canopy, (2) variation of foliage photosynthetic capacity with canopy depth, (3) wind speed attenuation throughout the canopy, and (4) rainfall interception by foliage elements. The soil module uses principles of the diffusion theory to predict temperature and moisture dynamics within the soil column, evaporation, and CO2 efflux from soil. The effect of soil heterogeneity on field-scale fluxes is simulated employing the Bresler-Dagan stochastic concept. The accumulation and melt of snow on the ground is predicted using an explicit energy balance approach. Ozone deposition is modeled as a sum of three fluxes- ozone uptake via plant stomata, deposition to non-transpiring plant surfaces, and ozone flux into the ground. All biophysical interactions are computed hourly while model projections are made at either hourly or daily time step. FORFLUX represents a comprehensive approach to studying ozone deposition and its link to carbon and water cycles in terrestrial ecosystems.

Air Pollution↗
PubMed1995

[Median clefts of the hand. Classification and therapeutic indications apropos of 29 cases].

Based on a series of 29 patients with median clefts of the hand (29 hands), the authors define the place of this malformation, its various clinical features and the therapeutic indications. The series consists of 13 boys and 7 girls, 9 bilateral cases and 11 unilateral cases. Involvement of the feet was observed in 9 cases. Several children also presented other malformations. 16 children were operated (22 hands). Two types of technique were used: simple closure of the cleft (Barsky's operation) and transposition of the index finger according to the Snow-Littler or Miura-Komada techniques. All operated patients were reviewed with a follow-up of more than one year and the results were assessed in terms of three criteria: overall use of the hand, thumb-index finger pinch grip, aesthetic appearance. The authors propose a new classification of median clefts of the hand based on examination of this series of 20 children: simple clefts with more or less complete absence of the middle finger, complex clefts with syndactyly (especially I and II), transverse bone polydactyly, extensive clefts with severe aplasia of the radial segment of the hand. Clinical and radiological examination confirm the experimental studies by Ogino. Barsky's operation gives satisfactory results in simple forms with parallel fingers. Translocation of the index finger to the base of the 3rd metacarpal is necessary in the presence of divergent fingers and syndactyly. Median clefts of the hand are very distinct from median aplasia, which is always unilateral, with no familial nature and no involvement of the feet and which can be classified together with brachysyndactyly. Each case must be studied before deciding treatment, as functional adaptation is always remarkable. The least favourable surgical results are observed in forms with abnormal position of the index finger (malrotation syndactyly). Lastly, the Snow-Littler operation is not devoid of complications.

Child↗
PubMed1994

A prospective study on changes in the sensibility of the oral mucosa and the mucosa of the upper lip after Le Fort I osteotomy.

A prospective study on 21 patients was performed in order to investigate the changes in the sensibility of the oral mucosa and the mucosa of the upper lip after a Le Fort I osteotomy. Patients were followed-up 1 month, 3 months and 6 months postoperatively. The sensibility of the mucosa was tested using electrical sensimetry (Laitinen, 1987). The teeth were tested with carbon dioxide snow (Obwegeser and Steinhäuser, 1963). A picture of the marked hypoaesthetic area was performed and magnified 1:1 if a hypoaesthesia of the cutaneous distribution of the infraorbital nerve was found. The area was measured using a Macintosh II CX computer. It was demonstrated, that after 3 months the infraorbital nerve regained its function completely. The greater palatine nerve and the posterior superior alveolar nerve demonstrated an incomplete recovery of sensory function after 6 months. After 6 months 92.8% of the teeth reacted to carbon dioxide snow. Within the first 6 months postoperatively, no pulpe necrosis was observed. No correlation could be found between the amount of anterior maxillary movement and the degree of hypoaesthesia of the infraorbital nerve. Dentate Le Fort I osteotomies showed a better sensory regeneration of the greater palatine nerve than edentulous Le Fort I osteotomies. After Le Fort I osteotomies in 2 parts, more hypoaesthesia of the greater palatine nerve was observed than after Le Fort I osteotomies in 1 part. After miniplate osteosynthesis, more hypoaesthesia of the posterior superior alveolar nerve was observed than after wire osteosynthesis. The results are discussed and compared with the results found in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

Organic contaminants in mountains.

The study of organic contaminants at high altitudes is motivated by the potential risk that they pose to humans living in, or depending on resources derived from, mountains and to terrestrial and aquatic ecosystems in alpine areas. Mountains are also ideal settings to study contaminant transport and behavior along gradients of climate and surface cover. Information on organic contaminants in mountains is compiled from the literature and synthesized, with a focus on atmospheric transport and deposition, contaminant dynamics in alpine lakes and aquatic organisms, and concentration differences with altitude. Diurnal mountain winds, in connection with enhanced deposition at higher elevations caused by low temperatures and high precipitation rates, conspire to make mid-latitude mountains become convergence zones for selected persistent organic chemicals. In particular, the more volatile constituents of contaminant mixtures seem to become enriched, relative to the less volatile constituents at higher altitudes. For selected contaminants, concentration inversions (i.e., concentrations that increase with elevation) have been observed. A notable difference between cold trapping in high latitudes and high altitudes is the likely importance of precipitation. High rates of snow deposition in mid- and high-latitude mountains may lead to a large contaminant release during snowmelt. Regions above the tree line often have little capacity to retain the released contaminants, suggesting the potential for a highly dynamic contaminant fate situation during the snow-free season with significant revolatilization and runoff. The chemical and environmental factors that control the orographic cold trapping of organic contaminants should be examined further by measuring and comparatively interpreting concentration gradients along several mountain slopes with widely different characteristics. Future efforts should further focus on the bioaccumulation and potential effects of contaminants in the upper trophic levels of alpine food chains, on measuring more water-soluble, persistent organic contaminants, and on studying how climate change may affect contaminant dynamics in mountain settings.

Air Movements↗