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PubMed2001

Whither acid rain?

Acid rain, the environmental cause célèbre of the 1980s seems to have vanished from popular conscience. By contrast, scientific research, despite funding difficulties, has continued to produce hundreds of research papers each year. Studies of acid rain taught much about precipitation chemistry, the behaviour of snow packs, long-range transport of pollutants and new issues in the biology of fish and forested ecosystems. There is now evidence of a shift away from research in precipitation and sulfur chemistry, but an impressive theoretical base remains as a legacy.

Acid Rain↗
PubMed2006

Controlled irradiative formation of penitentes.

Spike-shaped structures are produced by light-driven ablation in very different contexts. Penitentes 1-4 m high are common on Andean glaciers, where their formation changes glacier dynamics and hydrology. Laser ablation can produce cones 10-100 microm high with a variety of proposed applications in materials science. We report the first laboratory generation of centimeter-scale snow and ice penitentes. Systematically varying conditions allows identification of the parameters controlling the formation of ablation structures. We demonstrate that penitente initiation and coarsening require cold temperatures, so that ablation leads to sublimation. Once penitentes have formed, further growth of height can occur by melting. The penitentes initially appear as small structures (3 mm high) and grow by coarsening to 1-5 cm high. Our results are an important step towards understanding ablation morphologies.

Journal Article↗
PubMed1972

Cyclopropane Fatty acids in relation to earliness in spring and drought tolerance in plants.

Long chain cyclopropane fatty acids were observed in the sulfolipid fraction extracted from leaves of the early spring plants Galanthus nivalis L. and Anthriscus silvestris L. (Hoffm.). The content of cyclopropane fatty acids with 25 carbon atoms appeared to be clearly correlated with earliness in spring, and it ranged from 68% (G. nivalis L., snow drop) to 0.5% (wheat). Several long chain cyclopropane fatty acids were found in the drought-tolerant Corynephorus canescens (L.) P.B., exclusively in the phosphatidyl choline fraction.

Journal Article↗
PubMed1991

Hydrotropism and its interaction with gravitropism in maize roots.

We have partially characterized root hydrotropism and its interaction with gravitropism in maize (Zea mays L.). Roots of Golden Cross Bantam 70, which require light for orthogravitropism, showed positive hydrotropism; bending upward when placed horizontally below a hydrostimulant (moist cheesecloth) in 85% relative humidity (RH) and in total darkness. However, the light-exposed roots of Golden Cross Bantam 70 or roots of a normal maize cultivar, Burpee Snow Cross, showed positive gravitropism under the same conditions; bending downward when placed horizontally below the hydrostimulant in 85% RH. Light-exposed roots of Golden Cross Bantam 70 placed at 70 degrees below the horizontal plane responded positively hydrotropically, but gravitropism overcame the hydrotropism when the roots were placed at 45 degrees below the horizontal. Roots placed vertically with the tip down in 85% RH bent to the side toward the hydrostimulant in both cultivars, and light conditions did not affect the response. Such vertical roots did not respond when the humidity was maintained near saturation. These results suggest that hydrotropic and gravitropic responses interact with one another depending on the intensity of one or both factors. Removal of the approximately 1.5 millimeter root tip blocked both hydrotropic and gravitropic responses in the two cultivars. However, removal of visible root tip mucilage did not affect hydrotropism or gravitropism in either cultivar.

Darkness↗
PubMed2001

Introduction to a general crystallography.

The definition of an extended crystallographic group is given, based on an n-dimensional Euclidean space, carrier of a faithful integral representation of a permutation group of atomic positions. The Euclidean crystallography of normal crystals and the higher-dimensional one applied to incommensurately modulated crystals, intergrowth crystals and quasicrystals are special cases of a general crystallography. The same is true for the multimetrical crystallographic characterization of ice and of snow crystals. This approach can also be applied to single molecules, leading to what may be denoted as molecular crystallography. It possibly allows non-trivial structural relations between atomic positions belonging to the asymmetric unit of the molecular point group to be obtained. Two simple molecules, polycyclic aromatic hydrocarbons, are treated as illustrative examples.

Journal Article↗
PubMed2004

Analysis and synthesis of textured motion: particles and waves.

Natural scenes contain a wide range of textured motion phenomena which are characterized by the movement of a large amount of particle and wave elements, such as falling snow, wavy water, and dancing grass. In this paper, we present a generative model for representing these motion patterns and study a Markov chain Monte Carlo algorithm for inferring the generative representation from observed video sequences. Our generative model consists of three components. The first is a photometric model which represents an image as a linear superposition of image bases selected from a generic and overcomplete dictionary. The dictionary contains Gabor and LoG bases for point/particle elements and Fourier bases for wave elements. These bases compete to explain the input images and transfer them to a token (base) representation with an O(10(2))-fold dimension reduction. The second component is a geometric model which groups spatially adjacent tokens (bases) and their motion trajectories into a number of moving elements--called "motons." A moton is a deformable template in time-space representing a moving element, such as a falling snowflake or a flying bird. The third component is a dynamic model which characterizes the motion of particles, waves, and their interactions. For example, the motion of particle objects floating in a river, such as leaves and balls, should be coupled with the motion of waves. The trajectories of these moving elements are represented by coupled Markov chains. The dynamic model also includes probabilistic representations for the birth/death (source/sink) of the motons. We adopt a stochastic gradient algorithm for learning and inference. Given an input video sequence, the algorithm iterates two steps: 1) computing the motons and their trajectories by a number of reversible Markov chain jumps, and 2) learning the parameters that govern the geometric deformations and motion dynamics. Novel video sequences are synthesized from the learned models and, by editing the model parameters, we demonstrate the controllability of the generative model.

Algorithms↗
PubMed2003

The impact of climate variability on flood risk in Poland.

This article examines the role of climatic and hydrological variability in assessing the cumulative risk of flood events in Poland over a T-year period. In a broad sense flood-risk estimation combines a frequency analysis of extreme hydrological phenomena with an evaluation of flood-induced damages. The damage from floods depends on the critical values of the river discharges. The probabilistic flood analysis usually includes an estimation of the expected annual probability of the critical discharge Qcr being exceeded and the equivalent long-term risk of it being exceeded over the next T years. If, however, the process is nonstationary, the T-year risk of flood damage may depend importantly on the variation of hydrological processes. As a possible explanation for the variations observed in snowmelt-induced floods in Polish rivers, this article investigates the possible impact of the North Atlantic Oscillation (NAO) on surface air temperature T and precipitation P. The spatial distribution of the correlation coefficients between NAO and T, as well as NAO and P, show very significant differences in the NAO impact on meteorological variables in various parts of Europe. To assess the implications of NAO variations on spring flood discharges, a simple model of Snow Cover Water Equivalent (SCWE) was applied to selected Polish river catchments. The conclusion of this analysis is that the yearly maximum of SCWE values significantly decreases with increasing NAO. This leads to a temporal redistribution of winter and spring runoff. The question of spring flood characteristics being stationary or nonstationary may therefore be linked with stochastic properties of the NAO index time series.

Journal Article↗
PubMed2004

A general model for the analysis of mark-resight, mark-recapture, and band-recovery data under tag loss.

Estimates of waterfowl demographic parameters often come from resighting studies where birds fit with individually identifiable neck collars are resighted at a distance. Concerns have been raised about the effects of collar loss on parameter estimates, and the reliability of extrapolating from collared individuals to the population. Models previously proposed to account for collar loss do not allow survival or harvest parameters to depend on neck collar presence or absence. Also, few models have incorporated recent advances in mark-recapture theory that allow for multiple states or auxiliary encounters such as band recoveries. We propose a multistate model for tag loss in which the presence or absence of a collar is considered as a state variable. In this framework, demographic parameters are corrected for tag loss and questions related to collar effects on survival and recovery rates can be addressed. Encounters of individuals between closed sampling periods also can be incorporated in the analysis. We discuss data requirements for answering questions related to tag loss and sampling designs that lend themselves to this purpose. We illustrate the application of our model using a study of lesser snow geese (Chen caerulescens caerulescens).

Animals↗
PubMed2004

Visual stimuli in daily life.

People of all ages, but especially children and adolescents, are increasingly exposed to visual stimuli. Typical environmental stimuli that can trigger epileptic seizures in susceptible persons are televisions (TVs), computers, videogames (VGs), discothèque lights, venetian blinds, striped walls, rolling stairs (escalators), striped clothing, and sunlight reflected from snow or the sea or interrupted by trees during a ride in a car or train. Less common stimuli are rotating helicopter blades, disfunctioning fluorescent lighting, welding lights, etc. New potentially provocative devices turn up now and then unexpectedly. During the last decades especially, displays have become increasingly dominant in many of our daily-life activities. We therefore focus mainly on the characteristics of artificial light and on current and future developments in video displays and videogames. Because VG playing has been shown also to have positive effects, a rating system might be developed for provocativeness to inform consumers about the content. It is important that patients with epilepsy be informed adequately about their possible visual sensitivity.

Adolescent↗
PubMed2002

A tadpole-induced polyphenism in the salamander Hynobius retardatus.

Larvae of the salamander Hynobius retardatus have two distinct morphs: normal and broad-headed, cannibal morphs. We performed three experiments to differentiate among the following hypotheses: The broad-headed morph is induced to allow: (1) feeding on nutritious conspecifics; (2) exclusion of strong competitors for food or space; or (3) feeding on large, tough prey when smaller prey items are unavailable. When newly hatched larvae were reared with a heterospecific, Rana pirica (an anuran amphibian) tadpoles, the broad-headed morph was induced more frequently compared with those reared with conspecifics. The phenotype expressed depended on the size of the tadpoles: The broad-headed morph occurred more frequently with small and the normal morph with large tadpoles. Metamorphosis occurred sooner in larvae fed conspecifics compared with those fed heterospecific tadpoles, and the mean growth rate of larvae fed conspecifics was significantly faster than that of those fed tadpoles, suggesting that the heterospecific tadpoles were less nutritive than the conspecifics. These results do not support the hypotheses that the broad-headed morph evolved for consuming conspecifics because of their better balance of nutrients or for excluding strong competitors for food or space. We tentatively conclude that the morph evolved to eat large, tough prey, including both conspecifics and heterospecific tadpoles. Because H. retardatus usually spawns very early in the spring in small ponds partially covered with ice and snow, newly hatched larvae may starve from the lack of proper food owing to extremely low water temperatures. Thus, the broad-headed morph of H. retardatus may represent a cold-habitat adaptation to overcome the severe circumstance when the only food items available are relatively large conspecifics or heterospecific tadpoles.

Analysis of Variance↗
PubMed1981

Beta blockade and the secondary prevention of myocardial infarction.

In 1965 Snow reported a clinical trial in which treatment with propranolol significantly reduced mortality following myocardial infarction. Unfortunately the design of this trial was inadequate by modern standards, and the results must be discounted. None of the studies published since then have provided convincing evidence that beta blockers are useful following myocardial infarction. Survival after a myocardial infarction depends principally upon the amount of heart muscle that has been destroyed, and it is probably unreasonable to expect any treatment to reduce mortality by more than 20 or 30%. In patients who survive an infarction for more than 48 hours, the expected fatality rate in the next year is approximately 15%. To detect a reduction of this mortality to 10%, 2300 patients would be needed in the trial. The analysis of several of the published trials has been made difficult by a lack of data, the failure on the part of authors and journal editors to agree on a common method of presenting results, and disagreement as to whether results should be analysed on an "all patients--intention to treat" basis or by considering only "clinical effectiveness" among patients who remained on treatment. Examples of these problems will be given, together with a suggested scheme for data presentation. The 95% confidence intervals of all the randomised and double blind studies of beta blockers after myocardial infarction show that by "intention to treat" analysis, none demonstrate a statistically significant reduction in mortality among treated patients. Only the practolol trial was of a reasonable size, but even here total mortality was not significantly reduced; the result is in any case of only theoretical interest. The trials showing a reduction of mortality in association with alprenolol treatment are not convincing, and the stratified trial design of one of these may have given misleading results because of the relatively small number of patients involved.

Adrenergic beta-Antagonists↗
PubMed1999

Detection and nucleotide sequence analysis of human caliciviruses (HuCVs) from samples in non-bacterial gastroenteritis outbreaks in Hokkaido, Japan.

Samples of feces and vomit collected from patients during 13 non-bacterial gastroenteritis outbreaks which occurred in Hokkaido between 1995 and 1998 were examined by electron microscopy (EM) and reverse-transcription polymerase chain reaction (RT-PCR) for evidence of infection with human caliciviruses (HuCVs). In 6 food-borne outbreaks, oysters were the probable source of infection, while the origin of HuCVs was not found out for the other 7 outbreaks. One-hundred-eleven of 214 stool, vomit and oyster specimens examined gave positive results by RT-PCR, while HuCVs were detected by EM in 36 of 121 stool specimens examined. We determined the nucleotide sequences of 470-bp or 373-bp PCR products amplified from the RNA polymerase region of the HuCV genomes with primer sets MR3/4 and Yuri22F/R, respectively. The sequences of different strains revealed great heterogenicity, with a range of 60 to 100% homology among strains. In a few cases, a mixed genotype was found in the same patient or same outbreak by means of nested PCR and cloning of PCR products into an appropriate vector. Of the 19 different strains found, 4 strains could be classified as Norwalk virus (genogroup 1) and the other 15 strains as Snow Mountain agent (genogroup 2) based on genotyping with homology analysis. Furthermore, the strains belonging to genogroup 2 could be classified into 4 subgroups with more than 93% homology in amino acids among strains in the subgroup.

Animals↗
PubMed2006

Climate impacts at multiple scales: evidence for differential population responses in juvenile Chinook salmon.

1. We explored differential population responses to climate in 18 populations of threatened spring-summer Chinook salmon Onchorynchus tshawytscha in the Salmon River basin, Idaho. 2. Using data from a long-term mark-release-recapture study of juvenile survival, we found that fall stream flow is the best predictor of average survival across all populations. 3. To determine whether all populations responded similarly to climate, we used a cluster analysis to group populations that had similar annual fluctuations in survival. The populations grouped into four clusters, and different environmental factors were important for different clusters. 4. Survival in two of the clusters was negatively correlated with summer temperature, and survival in the other two clusters was positively correlated with minimum fall stream flow, which in turn depends on snow pack from the previous winter. 5. Using classification and regression tree analysis, we identified stream width and stream temperature as key habitat factors that shape the responses of individual populations to climate. 6. Climate change will likely have different impacts on different populations within this metapopulation, and recognizing this diversity is important for accurately assessing risks.

Animals↗
PubMed1993

Sleep in the harp seal (Pagophilus groenlandica). Peculiarities of sleep in pups during the first month of their lives.

Two white-coated (ten day-old) and two grey-spotted (one month-old) pups of the harp seal were implanted with electrodes for recording the electrocorticograms of the two hemispheres, electrocardiogram, electrooculogram and electromyogram of the neck muscles. In all individuals ECoG slow waves always developed synchronously in both hemispheres. When white and grey pups were recorded on the snow, the amount of active wakefulness was, respectively, 21.1% (s.e. 11.8%) and 29.9% (s.e. 0.2%) of total recording time, quiet wakefulness = 27.1% (s.e. 4.4%) and 38.2% (s.e. 6.6%), drowsiness = 7.7% (s.e. 0.5%) and 2.07% (s.e. 0.9%), light slow-wave sleep (SWS) = 15.1% (s.e. 3.2%) and 13.0% (s.e. 2.4%), deep SWS = 21.2% (s.e. 2.4%) and 13.8% (s.e. 3.8%), paradoxical sleep (PS) = 8.0% (s.e. 1.4%) and 7.4% (s.e. 1.1%). PS always followed SWS and was fragmented. Respiration was very rare and irregular in PS and a considerable part of PS episodes occurred within a single respiratory pause. During SWS all pups displayed respiratory pauses of up to three minutes, alternating with hyperventilation periods. Heart rate was lowest in PS. Peculiarities of sleep and the pace of sleep pattern development during the first month in seals may be adaptive to the cold environment and ice field drifting in their habitat.

Journal Article↗
PubMed1996

Trapping oestrid parasites of reindeer: the response of Cephenemyia trompe and Hypoderma tarandi to baited traps.

At 340-360 km North of the Arctic Circle in Norway, Hypoderma tarandi (L.) and Cephenemyia trompe (Modeer) females were caught in baited traps from 10 July to 21 August. During three summers, adverse climatic conditions inhibited flight activity of these oestrids on 56-68% of the days. Flies were not caught prior to or after these dates, nor at winds above 8 m/s, temperatures below 10 degrees C, light intensities below 20,000 lux, or during periods of rain or snow. CO2-baited insect flight traps caught significantly more H.tarandi females than non-baited traps. However, neither a white reindeer hide or reindeer interdigital pheromone glands enhanced the attraction of CO2 to H.tarandi or C.trompe. Hypoderma tarandi females also were attracted to mobile people, but not to stationary individuals. There were no significant differences in the number of C.trompe or H.tarandi caught in CO2-baited traps in a birch/willow woods, on the treeless vidda (= tundra-like biome), or at woods:vida ecotone sites. Flies were caught in traps on days when the nearest reindeer herds were 25-100 km away. Significantly more H.tarandi and C.trompe were caught from 09.30 to 14.30 hours than from 14.30 to 19.30 hours; no flies were caught from 20.00 to 07.00 hours (Norwegian Standard Time = NST). Because of CO2-baited traps caught from hundreds to thousands of mosquitoes, blackflies and Culicoides midges, when climatic conditions inhibited oestrid activity, reindeer aggregations and movements attributed to insect attacks during warm sunny days may be largely in response to attacks by H.tarandi and C.trompe.

Animals↗
PubMed1991

Primary structure of a 15-kDa protein from rat intestinal epithelium. Sequence similarity to fatty-acid-binding proteins.

An abundant and novel cytosolic protein was purified from the rat intestinal epithelium by gel filtration, ion-exchange and hydroxylapatite chromatography. The protein was eluted into two different positions (fractions 1 and 2) on DEAE-cellulose chromatography. We have completed the primary structure of the protein of fraction 1 by Edman degradation. The protein (144565 Da) contains 127 amino acid residues and has an acetylated alanine at its NH2-terminus. Comparison of the primary structure of the protein with porcine gastrotropin [Walz, A. D., Wider, M. D., Snow, J. W., Dass, C. & Desiderio, D. M. (1988) J. Biol. Chem. 263, 14189-14195] and rat hepatic fatty-acid-binding protein revealed that identical residues within these proteins are found in 90 and 54 out of a total of 127 positions, respectively. Bioactivity studies demonstrated that neither the protein nor liver and intestinal fatty-acid-binding proteins influence gastric acid secretory activity in rats with gastric fistulas compared to pentagastrin. The protein showed very low affinity for palmitic-acid-binding in vitro assay system and only trace amounts of endogenous fatty acids were detected from the protein. The protein, rat intestinal 15-kDa protein is considered to be a new member of the fatty-acid-binding protein family based on its structural features.

Amino Acid Sequence↗
PubMed1990

Sunglasses: are they necessary in Christchurch?

Concern over potential eye injury from sunlight prompted this study to see if the levels of sunlight in Christchurch posed a particular risk to our population's eyes, whether the populace was aware of any risk and whether effective sunglasses were freely available to the public. While there has been a 4% to 9% increase in UV radiation since 1969 due to global ozone depletion, no firm evidence was found that focal ozone depletion was a particular problem in New Zealand. Christchurch residents were poorly informed about the ocular hazards of sunlight. A questionnaire completed by 200 adults disclosed 32% were unaware of the particular danger of UV light and only 3% knew that snow blindness, eclipse burns and cataracts could all be caused by sunlight. Fifty-four sunglasses were analysed for labelling and for transmission characteristics of their lenses. The standard of labelling of the sunglasses was poor with only 53% making reference to UV transmission characteristics and only three pairs stating that they adhered to the New Zealand Sunglass Standard. Attention is drawn to the need to improve public awareness of the potential for eye injury from sunlight and to improve the standard of labelling of sunglasses.

Adult↗
PubMed1989

Meconium peritonitis due to meconium ileus presenting as fetal ascites: a case report.

A case of meconium peritonitis due to meconium ileus is described. The condition was detected antenatally as fetal ascites on ultrasonography. Plain X-ray of abdomen post-natally showed specks of calcification mainly at the flanks, while on ultrasonography specks of high echogenic areas were seen throughout the abdomen which has been described as "snow-storm sign". The aetiology of meconium ileus is briefly discussed.

Adult↗