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PubMed1999

Forced copulation results in few extrapair fertilizations in Ross's and lesser snow geese.

Extrapair paternity varies from 0 to over 70% of young among various populations of birds. Comparative studies have suggested that this variation is related to nesting density, breeding synchrony and the proportion of extrapair copulations. We used minisatellite DNA fingerprinting to examine levels of extrapair paternity in Ross's geese, Chen rossi, and lesser snow geese, C. caerulescens c. (hereafter snow geese) nesting in the largest known goose colony in the world. These geese have one of the highest known percentages of extrapair copulation (46-56% of all attempted copulations), and all of these appeared to be forced. Among all successful copulations, 33 and 38% were extrapair in Ross's and snow geese, respectively. Despite the high percentage of extrapair copulations, extrapair paternity was low in both Ross's and snow geese (2-5% of young). Extrapair paternity was not related to nest density in either species. However, in snow geese, extrapair paternity was more likely to occur in nests of females that nested asynchronously, either early or late in the season. This is one of a few reported examples of a negative relationship between extrapair paternity and breeding synchrony. Extrapair young also tended to come from eggs laid later in the clutch. Although forced extrapair copulations appear to be a relatively inefficient reproductive tactic for males, they may provide a reproductive advantage for some males. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1996

An Attempt to Interpret the Spread of Element Concentration in Antarctic Surface Snow: The Same Element in a Given Test Field, Several Elements in Different Sampling Fields

Sampling surface snow on a large test field always leads to a spread of analyte concentration data which partly follows a Gaussian distribution and partly a rectangular one as can be observed from the analysis of literature data. The spread depends on the nonuniformity of the air-snow interface in the field and on the extent of reproducibility of all the procedures used from sampling to analysis. Consequently a sample relevant to a restricted surface might be poorly representative of the surrounding area. Contamination of the sample during the gathering and storing steps is assumed to be the main source of nonrandom results (outliers). Using various statistical tools we were able to evaluate which part of the spread was due to the snow surface nonuniformity in the case of many samples collected in the same test field. In the case of samples gathered in different geographical areas, the possibility of finding correlations among points is greatly enhanced when three or more analytes are considered for each sample. When the same correlation is found for some analytes and a variable tentatively tested, information can be gained about the source of chemical content of snow samples. The use of UV pretreatment of snow samples has been proven to cut down the interference of organics on the electrochemical process in DPASV, allowing one to obtain accurate and reproducible data.

Journal Article↗
PubMed2006

Determination of a wide range of volatile and semivolatile organic compounds in snow by use of solid-phase micro-extraction (SPME).

Quantification and transformation of organic compounds are pivotal in understanding atmospheric processes, because such compounds contribute to the oxidative capacity of the atmosphere and drive climate change. It has recently been recognized that chemical reactions in snow play a role in the production or destruction of photolabile volatile organic compounds (VOC). We present an environmentally friendly method for determination of VOC and semi-VOC in snow collected at three sites-remote, urban, and (sub-)arctic. A solid-phase micro-extraction (SPME) procedure was developed and (semi-)VOC were identified by gas chromatography with mass spectrometric detection (GC-MS). A broad spectrum of (semi-)VOC was found in snow samples, including aldehydes, and aromatic and halogenated compounds. Quantification was performed for 12 aromatic and/or oxygenated compounds frequently observed in snow by use of neat standard solutions. The concentrations detected were between 0.12 (styrene and ethylbenzene) and 316 microg L(-1) (toluene) and limits of detection varied between 0.11 (styrene) and 1.93 microg L(-1) (benzaldehyde). These results indicate that the SPME technique presented is a broad but selective, versatile, solvent-free, ecological, economical, and facile method of analysis for (semi-)VOC in natural snow samples.

Journal Article↗
PubMed1999

Models to Assess the Risk of Snow and Wind Damage in Pine, Spruce, and Birch Forests in Sweden.

/ Each year damage to forests caused by snow and wind causes high economic losses. In Sweden, approximately 4 million m3 are damaged annually by snow and wind, roughly corresponding to a value of US$150 million, and in Europe, the damage amounts to hundreds of millions of US dollars each year. To help to reduce these losses, tools for risk assessment within forest management have been developed. Predictions were developed of the risk of damage from snow and wind to Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and Birch (Betula spp. L.) plots using tree, stand, and site characteristics. The data were obtained from 6756 permanent sample plots within the Swedish National Forest Inventory, which were inventoried twice at five-year intervals between 1983 and 1992. Input data for model development used measurements from the first inventory of tree characteristics for the largest sample tree, stand, and site data, and records of snow and wind damage from the second inventory. Models were developed for three different regions for pine- and spruce-dominated sites, while models for the whole country were developed for birch sites. In general the estimated proportion of damaged plots was highly overestimated (31.7%-56.2%), compared with the observed proportion of 3.4%-11.9%. The models for Norway spruce comprising tree, stand, and site data show the best predictability of damaged plots, with 60.6%-67.6% of plots correctly classified. It is concluded that the models developed can be used to detect sites with a high probability of damage from snow and wind, and thus be used as tools to reduce future damage and costs in practical forestry.KEY WORDS: Birch; Norway spruce; Risk assessment; Risk management; Scots pine; Silviculturehttp://link.springer-ny.com/link/service/journals/00267/bibs/24n2p209.html

Journal Article↗
PubMed1995

Chemical composition of fresh snow from Gulmarg, North India.

The chemical composition and pH of 30 fresh snow samples collected during December 1986 to May 1987 at Gulmarg (34 degrees 03' N, 74 degrees 24' E, 2655 m above mean sea level), a remote place in north India, were studied. The snow samples were, by and large, alkaline in nature and were largely influenced by non-marine aerosols. The concentrations of cations (Ca(2+), K(+) and Mg(2+)) were more than the anions (SO(2-)(4) and NO(-)(3)). Factor analysis indicated that most of the ionic components were transported into the region during the period of measurements. The transport of ionic components could be attributed to the passage of western disturbances over this region. The comparison of concentrations of anions and cations in the snow samples at Gulmarg with those reported from a few countries in the west revealed that the composition of Gulmarg snow largely differs in the concentrations of cations rather than anions. Among the cations, the concentration of Ca(2+) was high at Gulmarg and this could be responsible for buffering the pH of snow in the alkaline range.

Journal Article↗
PubMed2006

Pioneers in infection control: John Snow, Henry Whitehead, the Broad Street pump, and the beginnings of geographical epidemiology.

John Snow was one of the founders of epidemiology. Already convinced of the value of pure water, he analysed the distribution of cholera cases in the 1848 epidemic in relation to the purity of the water supply in London. His hypothesis that cholera was spread by contaminated water was tested by the 'Broad Street' epidemic of 1854. Snow quickly traced the water used in the houses affected by cholera to the pump in Broad Street, and persuaded the parish council to remove the handle. The epidemic subsided. The council did not really believe Snow, so the curate, Henry Whitehead, set out to repeat Snow's work, albeit at a more leisurely pace as the epidemic had subsided. He located 700 deaths within a 250-yard radius and showed that use of water from the Broad Street pump was strongly correlated with death from cholera. This surprised him as he had drunk water from the pump himself during the outbreak. Thus 'geographical epidemiology' began, although it was some years before Snow's observations were generally accepted.

Cholera↗
PubMed2006

Rethinking John Snow's South London study: a Bayesian evaluation and recalculation.

Famously, John Snow attempted to convince a critical professional audience that public water supplied to South London residents by private companies was a principal vector for the transmission of cholera. The result has been called the sine qua non of the "epidemiological imagination," a landmark study still taught today. In fact, Snow twice attempted to prove public water supplies spread cholera to the South London population. His first, published in 1855, suffered from an incomplete data set that limited its descriptive and predictive import. In 1856, armed with new data, Snow published a more definitive study. This paper describes a previously unacknowledged methodological and conceptual problem in Snow's 1856 argument. We review the context of the South London study, identify the problem and then correct it with an empirical Bayes estimation (EBE) approach. The result hopefully revitalizes Snow's research as a teaching case through the application of a contemporary statistical approach.

Bayes Theorem↗
PubMed2006

Molecular phylogenetic relationship of snow finch complex (genera Montifringilla, Pyrgilauda, and Onychostruthus) from the Tibetan plateau.

The snow finch complex (Montifringilla, Pyrgilauda, and Onychostruthus) has its center of distribution on the Tibetan plateau, with six out of seven species in the genera occurring there. Phylogenetic relationships among these six species of three genera have been studied based on DNA sequence data obtained from the mitochondrial cytochrome b gene and the nuclear myoglobin gene. The results support monophyly of the snow finch complex group and three major evolutionary lineages are recognized. The first clade consists of ruficollis, blanfordi, and davidiana. These three taxa are sometimes placed in their own genus, Pyrgilauda, and the DNA data supports this. The three taxa nivalis, henrici, and adamsi have traditionally been placed in the genus Montifringilla, and they group together strongly in the present analysis. The results further suggest that nivalis and adamsi are more closely related to each other than are nivalis and henrici, despite that the latter two are often regarded as conspecific. The third distinct lineage within the snow finch complex consists of taczanowskii, which has been placed its own genus, Onychostruthus. This taxon has a basal position in the phylogenetic tree and is sister to all other snow finches. We estimated that taczanowskii split from the other taxa between 2 and 2.5 mya, i.e., about the time for the most recent uplift of the Tibetan plateau, "the Tibet movement", 3.6-1.7 mya. Cladogenesis within the Montifringilla and Pyrgilauda clades seems to be contemporary with the second phase of "Tibet movement" at 2.5 mya and the third phase at 1.7 mya and "Kunhuang movement" in 1.5-0.6 mya. The dramatic climatic and ecological changes following from the uplift of the Tibetan plateau, together with the cyclic contraction and expansion of suitable habitats during the Pleistocene, are probably the most important factors for the cladogenesis in snow finch complex.

Animals↗
PubMed1997

Airborne pollutants along a roadside: assessment using snow analyses and moss bags.

Vertical snow sampling and moss bag transplants were used to estimate the local inorganic and organic pollutant load deposited from traffic along a major highway in Finland. The pH and concentrations of Cl(-), NO(3)(-), SO(4)(2-), Ca(2+), Na(+) and polyaromatic hydrocarbons (PAHs) were determined from snow samples collected in winter at different sites along the highway. In summer, moss bags containing 20 g of fresh red-stemmed feather moss (Pleurozium schreberi) were transplanted at the same sites. The moss bag transplants remained exposed to roadside traffic for a period of one month following which the samples were collected and the PAH profiles and concentrations were analysed. The deposition of inorganic and organic pollutants from road traffic was observed up to 60 m from the road. The prevailing winds had a significant effect on the dispersion of pollutants. Snow appears to be a good collector of inorganic pollutants from the atmosphere and can be used to monitor local airborne pollution from road traffic. Snow packs can also be used as passive collectors of organic pollutant loads from road traffic on a local scale. To monitor organic PAH deposition from the road traffic, moss bags appeared to be better indicators compared to snow sampling. The efficiency of moss bags in accumulating PAH compounds indicate that vegetation may be an important sink for traffic pollution.

Journal Article↗
PubMed1995

[John Snow (1813-1858): experimental studies on rebreathing of anesthetic gases in exhaled air].

As early as in 1850 (only 4 years after the first clinical performance of ether anaesthesia by W. T. G. Morton on 16 October 1846) John Snow recognised that ether and chloroform were exhaled unchanged with the expired air. To reuse these unchanged vapours in the following inspiration and thereby prolonging the narcotic effect of a given amount of anaesthetic vapour, he converted his ether inhaler into a To-and-Fro Rebreathing System: The apparatus was equipped with a facemask without an expiratory valve and a large reservoir bag containing pure oxygen; an aqueous solution of caustic potash was used as CO2 absorbent. In several experiments, performed on himself, Snow succeeded to demonstrate that rebreathing of the exhaled vapours was possible following carbon dioxide absorption, and that it resulted in a pronounced prolongation of the narcotic effects of the volatile anaesthetics. Furthermore, Snow performed experiments on animals using a closed system for evaluating the carbon dioxide production during anaesthesia. It is all the more worthwhile to introduce Snow's publications on these topics, as, despite their extraordinary theoretical and practical significance, they remained nearly unnoticed. Even in the fundamental articles by D. Jackson and R. Waters, both being the respected protagonists of the rebreathing technique in anaesthesia, the Snow papers remained uncited.

Anesthesia, Closed-Circuit↗
PubMed2000

John Snow: the first hired gun?

The 1854 English cholera outbreak led to reform of Victorian public health legislation, including the Nuisances Removal and Diseases Prevention Act. The reforms threatened the closure of many factories whose fumes were considered hazardous to the public's health. The second witness to appear before the Parliamentary committee considering the reforms was Dr. John Snow. Snow testified on behalf of the manufacturers threatened by the reforms. He stated that the fumes from such establishments were not hazardous. He contended that the workers in these factories did not become ill as a result of their exposures, and therefore these fumes could not be a hazard to the general public's health. Snow also presented data from the 1854 cholera outbreak as the basis for his belief that epidemic diseases were transmitted by water, not air. Although the data concerned cholera, Snow extended the inference to all epidemic diseases. When the committee's report was published, The Lancet chastised Snow in a stinging editorial. Parliament subsequently revised the bill in favor of the manufacturers and passed it into law. The implications of this particular episode in the history of epidemiology are discussed.

Cholera↗
PubMed2004

Size independence of the strength of snow.

The mechanical reliability of 600 randomly taken snow samples follows Weibull distributions: If sigma(max) is the maximum stress present in a specimen of given density, the fraction of specimens that fail at stresses below sigma(max) is P=1-exp[-(sigma(max)/sigma(0))(m)]. The scale parameter sigma(0) evaluated by the maximum likelihood method increases nearly quadratically with the density rho of snow, but, unlike predicted by the weakest link model, is independent of size and shape of the specimen: there is no size dependence of the strength of snow. The Weibull parameter m is independent of density, size, and shape of the snow sample, m=1.5+/-0.5. This implies, on the one hand, that the results of laboratory scale tests can be used for avalanche prediction, but on the other hand, that these predictions remain contaminated with large statistical errors. Snow is a fragile, weak, and unreliable material.

Journal Article↗
PubMed2002

Air-snow interactions and atmospheric chemistry.

The presence of snow greatly perturbs the composition of near-surface polar air, and the higher concentrations of hydroxyl radicals (OH) observed result in a greater oxidative capacity of the lower atmosphere. Emissions of nitrogen oxides, nitrous acid, light aldehydes, acetone, and molecular halogens have also been detected. Photolysis of nitrate ions contained in the snow appears to play an important role in creating these perturbations. OH formed in the snowpack can oxidize organic matter and halide ions in the snow, producing carbonyl compounds and halogens that are released to the atmosphere or incorporated into snow crystals. These reactions modify the composition of the snow, of the interstitial air, and of the overlying atmosphere. Reconstructing the composition of past atmospheres from ice-core analyses may therefore require complex corrections and modeling for reactive species.

Journal Article↗
PubMed1999

Structure/function/activity relationships in marine snow. Current understanding and suggested research thrusts.

Marine snow and marine snow components contribute to the mucilage phenomenon in the northern Adriatic Sea. Of special relevance is the matrix material, composed of extracellular polymeric substances, which are packaged into fibrils of colloidal dimensions. These 0.005 micron diameter fibrils are physical units of mucilage which can be visualized by transmission electron microscopy (TEM). They form polymer bridges between the various biotic and mineral components of marine snow, creating three-dimensional networks which affect floc porosity, density and settling behaviour. Recent observations of the matrix by TEM reveal complex fibril-delimited channels and capillary systems which partially traverse marine snow flocs and which are postulated to play roles in anomalous settling. Considering the marine snow floc as a microecosystem, the relationships between ultrastructure, chemistry and environmental properties are being explored. On the assumption that colloidal matrix materials, including those released into the bulk water, might provide advance information on anomalous floc behaviour, two new methods are recommended for monitoring the northern Adriatic Sea. One is a technique for chemical quantification of colloidal organic carbon. The other uses TEM, applied to water fractions derived from cascade ultracentrifugation, to estimate fibril quantities as a proportion of colloidal organic carbon.

Chemical Phenomena↗
PubMed1992

[Snow-white in danger. Women, socialization and health. Some messages, by means of allegory].

This is the modern-day allegory of Snow White, the most beautiful woman in the kingdom. Because of her beauty she is banished from the castle. The seven dwarfs who befriend her welcome her into their cottage. Little by little, they begin to impose their demands on her. They try to coerce her into submitting to life's little demands in order to attain beauty, health and happiness. Diet categorizes the foods filled with nasty calories that Snow White must learn to do without. Fitness outlines her spare time exercise regimen to keep her slim and trim. Mr. Clean provides her with specific household cleaning tips. Job tips advise her how to get a job outside the home to maintain her financial autonomy. Pills provide her with a way to assure a smooth transition between work and the household chores. Oh! And we almost forgot Baby. Who will care for Baby? Snow White of course--since she is the only woman in the house. Finally, to assure perfect co-ordination of all these tasks, Excel sends her off to take a time management course. Snow white responds enthusiastically to all the expectations. As anticipated, she loses weight. She then becomes exhausted and collapses and is transformed into Burnt-Out Beauty. She remains in a deep sleep for 100 days and nights. The dwarfs place her in a glass box in a forest clearing where she is discovered by Prince Conscience. He opens the glass box, kisses her lightly on the forehead, and immediately disappears. Snow White awakens and remembers the events preceding her deep sleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed2005

Will loss of snow cover during climatic warming expose New Zealand alpine plants to increased frost damage?

If snow cover in alpine environments were reduced through climatic warming, plants that are normally protected by snow-lie in winter would become exposed to greater extremes of temperature and solar radiation. We examined the annual course of frost resistance of species of native alpine plants from southern New Zealand that are normally buried in snowbanks over winter (Celmisia haastii and Celmisia prorepens) or in sheltered areas that may accumulate snow (Hebe odora) and other species, typical of more exposed areas, that are relatively snow-free (Celmisia viscosa, Poa colensoi, Dracophyllum muscoides). The frost resistance of these principal species was in accord with habitat: those from snowbanks or sheltered areas showed the least frost resistance, whereas species from exposed areas had greater frost resistance throughout the year. P. colensoi had the greatest frost resistance (-32.5 degrees C). All the principal species showed a rapid increase in frost resistance from summer to early winter (February-June) and maximum frost resistance in winter (July-August). The loss of resistance in late winter to early summer (August-December) was most rapid in P. colensoi and D. muscoides. Seasonal frost resistance of the principal species was more strongly related to daylength than to temperature, although all species except C. viscosa were significantly related to temperature when the influence of daylength was accounted for. Measurements of chlorophyll fluorescence indicated that photosynthetic efficiency of the principal species declined with increasing daylength. Levels of frost resistance of the six principal alpine plant species, and others measured during the growing season, were similar to those measured in tropical alpine areas and somewhat more resistant than those recorded in alpine areas of Europe. The potential for frost damage was greatest in spring. The current relationship of frost resistance with daylength is sufficient to prevent damage at any time of year. While warmer temperatures might lower frost resistance, they would also reduce the incidence of frosts, and the incidence of frost damage is unlikely to be altered. The relationship of frost resistance with daylength and temperature potentially provides a means of predicting the responses of alpine plants in response to global warming.

Adaptation, Physiological↗
PubMed2006

3D documentation of footwear impressions and tyre tracks in snow with high resolution optical surface scanning.

The three-dimensional documentation of footwear and tyre impressions in snow offers an opportunity to capture additional fine detail for the identification as present photographs. For this approach, up to now, different casting methods have been used. Casting of footwear impressions in snow has always been a difficult assignment. This work demonstrates that for the three-dimensional documentation of impressions in snow the non-destructive method of 3D optical surface scanning is suitable. The new method delivers more detailed results of higher accuracy than the conventional casting techniques. The results of this easy to use and mobile 3D optical surface scanner were very satisfactory in different meteorological and snow conditions. The method is also suitable for impressions in soil, sand or other materials. In addition to the side by side comparison, the automatic comparison of the 3D models and the computation of deviations and accuracy of the data simplify the examination and delivers objective and secure results. The results can be visualized efficiently. Data exchange between investigating authorities at a national or an international level can be achieved easily with electronic data carriers.

Automobiles↗
PubMed2003

Regional variation in the chemical composition of winter snow pack and terricolous lichens in relation to sources of acid emissions in the Usa river basin, northeast European Russia.

The chemical composition of snow and terricolous lichens was determined along transects through the Subarctic towns of Vorkuta (130 km west-east), Inta (240 km south-north) and Usinsk (140 km, southwest-northeast) in the Usa river basin, northeast European Russia. Evidence of pollution gradients was found on two spatial scales. First, on the Inta transect, northward decreases in concentrations of N in the lichen Cladonia stellaris (from 0.57 mmol N g(-1) at 90 km south to 0.43 mmol N g(-1) at 130 km north of Inta) and winter deposition of non-sea salt sulphate (from 29.3 to 12.8 mol ha(-1) at 90 km south and 110 km north of Inta, respectively) were attributed to long range transport of N and S from lower latitudes. Second, increased ionic content (SO42-, Ca2+, K+) and pH of snow, and modified N concentration and the concentration ratios K+:Mg2+ and K+: (Mg2++Ca2+) in lichens (Cladonia arbuscula and Flavocetraria cucullata) within ca. 25-40 km of Vorkuta and Inta were largely attributed to local deposition of alkaline coal ash. Total sulphate concentrations in snow varied from ca. 5 micromol l(-1) at remote sites to ca. 19 micromol l(-1) near Vorkuta. Nitrate concentration in snow (typically ca. 9 micromol l(-1)) did not vary with proximity to perceived pollution sources.

Acid Rain↗