bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevention of microvascular complications in diabetic children and adolescents
Authors: Verrotti A , Catino M , Di Ricco L , Casani A , Chiarelli F
Published: April 2008

Diabetes mellitus causes profound alterations in many body tissues. Microvascular diabetic complications include diabetic neuropathy, nephropathy and retinopathy. Nephropathy first becomes manifest with hyperfiltration and microalbuminuria. These functional changes evolve over several years to a stage of marked deterioration of renal function. The possible preventive measures are metabolic control, reduction of dietary protein intake and use of ACE‐inhibitors. Metabolic control is also important for the prevention of diabetic retinopathy. In fact, patients with HbAlc higher than 10% have an increased risk of progression of retinopathy. Moreover, an accelerated progression of retinopathy has been observed in patients with systemic hypertension following the onset of microalbuminuria. It has been demonstrated that diabetic neuropathy can also be present during childhood; therefore, it is possible to detect electrophysiological abnormalities in children and adolescents with IDDM. Glycaemic and blood pressure control are, so far, the main means for possible prevention or modification of the natural history of diabetic microvascular complications. Tight glycaemic control may have beneficial effects for diabetic neuropathy. In addition, other preventive measures, such as aldose reductase inhibitors, ganglio‐sides, neurotrophic vitamins, etc., have been studied in the last years. However, no conclusive results have been obtained so far. □Diabetes, microvascular complications, nephropathy, retinopathy
Present and future perspectives on children with type 1 diabetes
Authors: Kordonouri O , Danne T
Published: April 2008

This review presents current achievements in paediatric diabetology and discusses potential new approaches. Recent multinational investigations have demonstrated that in spite of multidisciplin‐ary diabetes care only one‐third of young patients with diabetes have an HbAlc below 8%, which is associated with a lower risk for development of secondary complications. Since there is no standard protocol for the optimal treatment of diabetes in children and adolescents, the therapy has to be tailored to the individual child's needs, involving not only paediatricians, but also dieticians, diabetes educators, psychologists and social workers. To improve the current situation a major goal for the next few years appears to be the establishment of standards for structure, process and outcome quality in paediatric diabetology. Future perspectives include possibilities for a cure via islet‐ or pancreas transplantation or improved pharmacological therapy following the introduction of new types of insulin or other beta cell‐related peptides as adjunctive therapy not currently used. □Children, diabetes, quality control
Telomere length and obesity
Authors: Zannolli Raffaella , Mohn Angelika , Buoni Sabrina , Pietrobelli Angelo , Messina Mario , Chiarelli Francesco , Miracco Clelia
Published: April 2008

Aim: To assess the telomere length in apparently healthy obese and normal‐weight subjects.

Methods: Seventy‐six Caucasian subjects were chosen including 53 children (age 8.2 ± 3.5 years) and 23 adults (age 40.5 ± 8.4 years). Among these, 22 (12 children and 10 adults) were obese with a body mass index (BMI, kg/m2) > 2 SD above the norm. Bioelectrical impedance analysis (BIA), measured with a multiple frequency analyzer, was used to estimate body composition. DNA extraction from white blood cells was used to estimate the telomere length by detection of terminal restriction fragments (TRF).

Results: No difference was found between the TRF lengths of obese and normal children. Obese adults had shorter TRF lengths than adults who were not obese (mean TRF length difference, −884.5; 95% confidence intervals −1727 to −41.8; t= 2.183; df = 17; p < 0.041).

Conclusions: Obese adults have shorter telomeres than their normal‐weight counterparts, while this phenomenon is not present in childhood.
Farmers and Consumers: Towards Symbiosis?
Authors: Tarditi Secondo
Published: April 2008

Public declarations on the Common Agricultural Policy (CAP) have recently become more consumer‐oriented, aiming at “transparency and defence of consumer interests”. Even demonstrations have changed: fewer occupations of railways, motorways, and airports, and more free distribution of grilled steaks, milk, and fruit to citizens.
Blocking of Bacterial Biofilm Formation by a Fish Protein Coating
Authors: Vejborg Rebecca Munk , Klemm Per
Published: April 2008

Bacterial biofilm formation on inert surfaces is a significant health and economic problem in a wide range of environmental, industrial, and medical areas. Bacterial adhesion is generally a prerequisite for this colonization process and, thus, represents an attractive target for the development of biofilm-preventive measures. We have previously found that the preconditioning of several different inert materials with an aqueous fish muscle extract, composed primarily of fish muscle α-tropomyosin, significantly discourages bacterial attachment and adhesion to these surfaces. Here, this proteinaceous coating is characterized with regards to its biofilm-reducing properties by using a range of urinary tract infectious isolates with various pathogenic and adhesive properties. The antiadhesive coating significantly reduced or delayed biofilm formation by all these isolates under every condition examined. The biofilm-reducing activity did, however, vary depending on the substratum physicochemical characteristics and the environmental conditions studied. These data illustrate the importance of protein conditioning layers with respect to bacterial biofilm formation and suggest that antiadhesive proteins may offer an attractive measure for reducing or delaying biofilm-associated infections.
Longitudinal Study of Antimicrobial Resistance among
Escherichia coli
Isolates from Integrated Multisite Cohorts of Humans and Swine
Authors: Alali W. Q. , Scott H. M. , Harvey R. B. , Norby B. , Lawhorn D. B. , Pillai S. D.
Published: April 2008

In a 3-year longitudinal study, we examined the relationship between the seasonal prevalence of antimicrobial-resistant (AR)
Escherichia coli
isolates from human wastewater and swine fecal samples and the following risk factors: the host species, the production type (swine), the vocation (human swine workers, non-swine workers, and slaughter plant workers), and the season, in a multisite, vertically integrated swine and human population representative of a closed agri-food system. Human and swine
E. coli
(
n
= 4,048 and 3,429, respectively) isolates from wastewater and fecal samples were tested for antimicrobial susceptibility, using the Sensititre broth microdilution system. There were significant (
P
< 0.05) differences among AR
E. coli
prevalence levels of (i) the host species, in which swine isolates were at higher risk for resistance to tetracycline, kanamycin, ceftiofur, gentamicin, streptomycin, chloramphenicol, sulfisoxazole, and ampicillin; (ii) the swine production group, in which purchased boars, nursery piglets, and breeding boars isolates had a higher risk of resistance to streptomycin and tetracycline; and iii) the vocation cohorts, in which swine worker cohort isolates exhibited lower sulfisoxazole and cefoxitin prevalence than the non-swine worker cohorts, while the slaughter plant worker cohort isolates exhibited elevated cefoxitin prevalence compared to that of non-swine workers. While a high variability was observed among seasonal samples over the 3-year period, no significant temporal trends were apparent. There were significant differences in the prevalence levels of multidrug-resistant isolates between host species, with swine at a higher risk of carrying multidrug-resistant strains than humans. Considering vocation, slaughter plant workers were at higher risk of exhibiting multidrug-resistant
E. coli
than non-swine workers.
Glucosamine Found as a Substituent of Both Phosphate Groups inBordetellaLipid A Backbones: Role of a BvgAS-Activated ArnT Ortholog
Authors: Marr Nico , Tirsoaga Alina , Blanot Didier , Fernandez Rachel , Caroff Martine
Published: April 2008

Endotoxins are amphipathic lipopolysaccharides (LPSs), major constituents of the outer membrane of gram-negative bacteria. They consist of a lipid region, covalently linked to a core oligosaccharide, to which may be linked a repetitive glycosidic chain carrying antigenic determinants. Most of the biological activities of endotoxins have been associated with the lipid moiety of the molecule: unique to gram-negative bacteria, LPS is a ligand of the mammalian TLR4-MD2-CD14 pathogen recognition receptor complex. Lipid A preparations are often heterogeneous with respect to both the numbers and the lengths of fatty acids and the natures of substituents on the phosphate groups when present. The variants can significantly affect host immune responses. Nine species in theBordetellagenus have been described, and the fine LPS structures of seven of them have been published. In this report, lipids A fromBordetella pertussisTohama I andB. bronchisepticastrain 4650 were further characterized and revealed to have a glucosamine substituting both lipid A phosphate groups of the diglucosamine backbone. These substitutions have not been previously described for bordetellae. Moreover, aB. pertussistransposon mutation that maps within a gene encoding aBordetellaArnT (formerly PmrK) glycosyl transferase ortholog does not carry this substitution, thus providing a genetic basis for the modification. Reverse transcriptase PCR of this locus showed that it is Bvg regulated, suggesting that the ability ofBordetellato modify lipid A via this glucosamine modification is a potential virulence trait.
Patterns of allocation and growth in aquatic Sphagnum species
Authors: Rice Steven K.
Published: April 2008

The hypothesis that aquatic plants have greater allocation to photosynthetic tissues was tested using a common garden experiment with three pairs of ecologically contrasting Sphagnum species (S. portoricense and S. papillosum; S. trinitense and S. recurvum; S. macrophyllum var. floridanum and S. strictum). When submerged, aquatic taxa (the former in each pair) all had greater relative growth rates and greater allocation to photosynthetic tissues, as evidenced by higher whole plant chlorophyll content. The evolution of greater photosynthetic allocation appears to result from changes in two independently evolving systems: allocation to photosynthetic cells rather than nonphotosynthetic hyaline cells, and a shift in biochemical partitioning within photosynthetic cells favoring light-reaction proteins. The former was assessed by comparing photosynthetic cell volume in leaves, and the latter was estimated from chlorophyll to nitrogen ratios. The mechanism whereby greater photosynthetic allocation was achieved differed in each aquatic species. In a second experiment, variation in growth and allocation was assessed for three populations each of S. trinitense and S. recurvum. Nested analysis of variance verified that the differences between S. trinitense and S. recurvum observed in relative growth rate and chlorophyll content in the species-level test were robust given the magnitude of population-level variation. It is concluded that (i) aquatic habitats do select for features that lead to greater relative growth rate in submerged environments, (ii) relative growth rate is functionally correlated with allocation to photosynthetic tissues, (iii) allocations at the cellular and biochemical level evolve independently, and (iv) patterns of allocation represent adaptations to environmental conditions present in the aquatic environment. Key words: Sphagnum, relative growth rate, chlorophyll content, allocation, aquatic plants, adaptation.
Chemical and nutritional status of dwarf mistletoe, Armillaria root rot, and Comandra blister rust infected trees which may influence tree susceptibility to bark beetle attack
Authors: Nebeker T. E. , Tisdale R. A. , Schmitz R. F. , Hobson K. R.
Published: April 2008

The terpenoid and phenyl propanoid content of xylem resin as well as phloem nitrogen and carbohydrate levels of lodgepole pine trees infected with Armillaria root disease, Comandra blister rust, and dwarf mistletoe and check (asymptomatic) trees were determined. Comparisons were made to determine if differences existed that might influence their susceptibility to bark beetle attack. These variables were also contrasted with respect to aspect (north and south). Five volatiles (tricyclene, α-pinene, camphene, γ-terpinene, and bornyl acetate) were significantly higher in trees with one or more diseases than in check trees. Four volatiles (myrcene, camphor, 4-allylanisole, and γ-terpineol) were significantly lower in diseased trees. Camphene was the only resin constituent found to differ with respect to aspect, with a higher concentration on the north aspect of check trees. There were no significant differences in carbohydrate or nitrogen content with respect to aspect. The check trees were found to have significantly higher starch, total nitrogen, and free amino-N contents than diseased trees. Trees infected with Comandra blister rust were found to contain lower levels of reducing and nonreducing sugars than the other diseased trees and the check trees. Changes in terpenoids and phenyl propanoids in trees susceptible to mountain pine beetle attack suggest a biochemical basis for host selection. Key words: mountain pine beetle, lodgepole pine, Comandra blister rust, dwarf mistletoe, Armillaria root disease, resin chemistry, susceptibility.
Trichome density and its protective potential against ultraviolet-B radiation damage during leaf development
Authors: Karabourniotis George , Kotsabassidis Dimitris , Manetas Yiannis
Published: April 2008

Trichome density and the capacity of leaf hairs to protect underlying tissues against ultraviolet-B radiation damage were assessed during leaf development in three tree species. In all cases, trichome density and the relative quantities of ultraviolet radiation absorbing phenolic constituents (expressed on a leaf area basis) declined considerably with leaf age. In addition, the percent leaf dry mass invested in trichome decreased significantly. Reductions were greater on the adaxial leaf surface, leading to an almost glabrous upper epidermis in mature leaves. Internal (i.e., leaf total minus trichome) phenolics showed no significant changes with leaf age in Eriobotrya japonica and Cydonia oblonga. In Olea europaea, however, the concentration of internal phenolics was doubled in mature leaves. Ultraviolet-B radiation resulted in a reduction of photosystem II photochemical efficiency and extensive epidermal browning only in young, dehaired leaves. No such effects were observed in young, dehaired leaves in the absence of ultraviolet-B radiation or in normal young or mature ultraviolet-B-irradiated leaves. It is suggested that the dense trichomes often covering young leaves may, in addition to other functions, protect transiently the underlying cells against ultraviolet-B radiation damage during the time period required for the maturation of internal avoidance and (or) repairing mechanisms. Key words: Cydonia oblonga, Eriobotrya japonica, Olea europaea, leaf development, leaf hairs, phenolics, ultraviolet-B radiation damage.
Endophytic fungi associated with healthy pine needles and needles infested by the pine needle gall midge, Thecodiplosis japonensis
Authors: Hata Kunihiko , Futai Kazuyoshi
Published: April 2008

The endophytic mycobiota of the galls of pine needle gall midge, Thecodiplosis japonensis, and healthy current-year needles of Pinus densiflora and the F2 hybrid pine (Pinus thunbergii × (P. thunbergii × P. densiflora)) was compared. Phialocephala sp. was the dominant endophyte isolated from the galls and from the basal regions of healthy needles. Species richness in endophytes was facilitated in galls compared to the basal region of healthy needles, and the commencement of their colonization was hastened in galls. In the early stages of gall formation, however, no endophyte was isolated, suggesting that gall endophytes are not carried into the galls by the midge. Endophytes of healthy and galled pine needles were divided into two groups: position-specific fungi, which showed intrinsically restricted distributions on needles; and gall-specific fungi. These two groups might represent different ecological groups of endophytes. Possible interactions between endophytes and the pine needle gall midge are also discussed. Key words: endophytic fungi, Pinus densiflora, F2 hybrid pine, pine needle gall midge.
Analysis of surface structures ofCladonia mitispodetia in historic and recent collections from Greenland
Authors: Heide-Jørgensen H. S. , Johnsen I.
Published: April 2008

Field observations in Greenland combined with a scanning electron microscopical survey have revealed a hitherto undescribed correspondence in the distribution of a brownish colour and a crust-like surface structure formed by hyphae at exposed parts of the shoot tips of podetia of Cladonia mitis. A different brownish colour pattern is caused by fungal parasites. A comparable but less prominent colour-crust syndrome was observed on C. mitis from Denmark. The colour-crust syndrome is considered an unhealthy and damaged condition, and the light microscope reveals that areas with this syndrome mainly consist of the uncovered stereome devoid of the hyphal zone containing algal colonies. In a comparative study of podetia collected up to 105 years ago in Greenland, crust-like surface structures occur more frequently since the 1970s. Key words: Arctic lichen heath, Cladonia mitis, Greenland, podetial morphology, UV-B radiation.
Microtopography and vegetation in Atlantic white cedar swamps: the effects of natural disturbances
Authors: Ehrenfeld Joan G.
Published: April 2008

Disturbance may alter patterns of microtopography within wetlands, and may consequently alter the relationship between woody plants and microtopography. I measured microtopographic relief and the relationship of shrubs and tree seedling distributions to microrelief in undisturbed Atlantic white cedar (Chamaecyparis thyoides (L.) Mills.)) swamps in the New Jersey Pinelands, and in stands disturbed by blowdowns and fire. In undisturbed stands, hummock–hollow structures, at a scale of about 1 m, are poorly defined and often obscured by smaller scale and larger scale patterns of elevation. The swamp floor is, on average, 25 cm above the lowest hollows, but sites ≥ 100 cm high occur in undisturbed swamps and within blowdown gaps. Burned sites tend to lack microsites with high elevations, and have less well-developed pattern than undisturbed sites. In blowdowns, there is an increase in the frequency of high-elevation microsites, and more pronounced hummock–hollow patterning. All woody plant species occupy sites of intermediate elevation, are absent from the lowest 20% of the forest floor, and display little evidence of habitat differentiation among species along the microtopographic gradient. In disturbed sites, the species' ranges shift in response to disturbance-induced changes in the availability of microsites. Key words: microtopography, microsites, forested wetlands, swamps, spatial pattern, disturbance, Chamaecyparis thyoides, shrubs.
Use of Pup Counts in Indexing Population Changes in Pinnipeds
Authors: Berkson J. M. , DeMaster D. P.
Published: April 2008

A series of population simulations were used to test the accuracy of estimating the discrete rates of population change (RPC) from annual pup counts. The simulations indicate that pup counts can give a biased estimate of RPC, and that the magnitude and direction of bias depends on which life history parameters are density dependent and on the maximum rate of population change. In general, if pre-census pup survival is density dependent the estimated RPC using pup counts is too low. If post-census pup survival is density dependent, the estimated RPC is too high. If adult survival is density dependent, there is very little bias in the estimate. The results indicate that pup counts can be reliable indicators of population growth, but caution should be used in interpreting the results unless density feedback mechanisms have been identified.
Movements of Adult Female Dungeness Crabs (Cancer magister) In Northern California Based on Tag Recoveries
Authors: Diamond Nancy , Hankin David G.
Published: April 2008

Of 11072 adult female Dungeness crabs (Cancer magister) tagged and released in northern California, 463 were recovered with useful location data that could be used for analyses of crab movement patterns. Although qualitative analyses of movement data suggested possible directed northward movement during winter months, application of two nonparametric tests of movement directionality (the Rayleigh test and Moore's test) failed to support significant directed movement during winter. Large numbers of tagged crabs were recovered inshore of release in shallow sandy areas during spring months, but valid statistical analyses of spring movement data were ruled out by concentration of fishing effort in shallow waters during spring. Nevertheless, recovery of large numbers of tagged females in inshore areas during spring is entirely consistent with an hypothesis of spring inshore movement of females for molting, mating, and later extrusion of egg masses. This hypothesis can be constructed on the basis of information independent of tag recovery data. The most striking finding was that 46% of all recovered crabs were recaptured within 2 km of original release sites; many of these crabs had been at large more than 1 yr. Adult female Dungeness crabs appear to constitute extremely localized stocks in northern California.
Model of Sulphate Concentration in a Small Stream in the Harp Lake Catchment, Ontario
Authors: Seip Hans M. , Seip Ragnhild , Dillon Peter J. , Grosbois Ed de
Published: April 2008

A model previously used for Norwegian catchments was modified to predict discharge and sulphur concentration in a stream draining a small catchment in Ontario. The annual input of sulphur roughly balances the output, the average sulphur flux being about 1.6 g S∙m−2∙yr−1. The average dry deposition was estimated to be about 0.4 g S∙m−2∙yr−1. For good agreement between calculated and observed sulphur concentrations, it was necessary to introduce a reduction (or adsorption) process for sulphate in deeper soil layers during summer and fall. During dry periods, however, sulphate is produced by oxidation in the upper soil layer. The sulphate concentrations in streamwater during snowmelt are remarkably constant. According to model results this could be explained by the existence of a reservoir of easily soluble sulphur in the soil considerably larger than the annual sulphur flux. The basic structure of the models applied to the Ontario stream and to two streams in Norway was the same. It seems likely, therefore, that the model may, with moderate modifications, be applicable to many catchments.
Modeling the Lethal Effects of High Temperature on Fish
Authors: Kilgour D. Marc , McCauley Robert W. , Kwain W.
Published: April 2008

We developed a mathematical model relating mean survival times of samples of fish at lethally high temperatures. It permits the estimation of upper incipient lethal temperature (UILT, degrees Celsius) from the results of short-term experiments. Application of the model to data sets obtained from the literature yields "predicted" UILTs usually within 0.5° and almost always within 1° of observed values. The model was also applied to determine threshold toxicities (LC50, 144 h) of copper ion from tests of shorter duration.
Responses of Sea-Ice Microalgae to Climatic and Fortnightly Tidal Energy Inputs (Manitounuk Sound, Hudson Bay)
Authors: Gosselin M. , Legendre L. , Demers S. , Ingram R. G.
Published: April 2008

Variations of sea-ice microalgae at the ice–water interface (Manitounuk Sound, Hudson Bay, Canada) were studied in relation to various energy inputs (light, tidal mixing, and heat) in April and May 1982. Seasonal photosynthetic activity does not start before the light intensity reaches 7.6 μEinst∙m−2∙s−1. Above this value, the seasonal increase in cell numbers and chlorophyll and in the photoadaptation index (Ik) is related to the increase in underice light intensity. The sea-ice community changes from shade to light adaptation to optimize the use of ambient light energy. Photosynthetic efficiency (αB) is mainly controlled by the fortnightly tidal vertical mixing, which governs the amount of phosphate (or of another nutrient factor) in the upper brackish layer. The ice microflora, which grows at a stable interface, takes advantage of nutrient replenishment during mixed water column conditions. We conclude that production of microalgae depends upon three forms of energy: (1) the flux of solar light, (2) the inputs of auxiliary mechanical energy (here, the fortnightly tides), and (3) the energy exchanges (here, the heat flux) responsible for the maintenance or destruction of energetic interfaces (ergoclines).
Developments in Stream Ecosystem Theory
Authors: Minshall G. Wayne , Cummins Kenneth W. , Petersen Robert C. , Cushing Colbert E. , Bruns Dale A. , Sedell James R. , Vannote Robin L.
Published: April 2008

Four significant areas of thought, (1) the holistic approach, (2) the linkage between streams and their terrestrial setting, (3) material cycling in open systems, and (4) biotic interactions and integration of community ecology principles, have provided a basis for the further development of stream ecosystem theory. The River Continuum Concept (RCC) represents a synthesis of these ideas. Suggestions are made for clarifying, expanding, and refining the RCC to encompass broader spatial and temporal scales. Factors important in this regard include climate and geology, tributaries, location-specific lithology and geomorphology, and long-term changes imposed by man. It appears that most riverine ecosystems can be accommodated within this expanded conceptual framework and that the RCC continues to represent a useful paradigm for understanding and comparing the ecology of streams and rivers.
Ascaridoid Nematodes from the Stomach of Harp Seals, Phoca groenlandica, from Newfoundland and Labrador
Authors: Brattey John , Ni I-Hsun
Published: April 2008

Stomachs of 488 harp seals, Phoca groenlandica, collected off Newfoundland and Labrador during 1984–88, contained four species of ascaridoid nematodes. Seals had high prevalences and abundances of Contracaecum osculatum B and Phocascaris sp. but were rarely infected with Anisakis simplex B or Pseudoterranova decipiens B (sealworm). Nematode abundance increased with age, and distribution of each species among seals was highly aggregated. Gastric lesions, often associated with clusters of nematodes, occurred in 13.8% of 405 seals. Female seals with large numbers of nematodes had a higher body condition index (sculp weight) than lightly infected females. Overall sex ratios of C. osculatum B and Phocascaris sp. were biased toward females, but sex ratios of adult nematodes among individual seals were heterogeneous. Most nematodes recovered were third- or fourth-stage larvae; adults of C. osculatum B and Phocascaris sp. were also common, but no mature females of A. simplex B or P. decipiens B were found. Harp seals are probably unimportant in the transmission of A. simplex but may be partly responsible for sealworm found in fish stocks off Newfoundland and Labrador. More information on other pinniped species is needed to assess more precisely the relative importance of harp seals in sealworm transmission.
Crustacean Plankton in Lake Winnipeg: Variation in Space and Time as a Function of Lake Morphology, Geology, and Climate
Authors: Patalas K. , Salki A.
Published: April 2008

Rivers draining different geological basins have the most important impact on the formation of the planktonic community in Lake Winnipeg. Very diverse patterns of distribution of individual species reflected the complexity of the water masses structured by lake morphology and the configuration of river inflows. Of the 34 species identified (15 copepods and 19 cladocerans), 12 were found exclusively in the South Basin, 7 exclusively in the North Basin, and 15 were common to both basins. A "core" group of 12 species was distributed over the whole lake, but the remaining 22 species ("unsuccessful invaders") were present only in restricted areas, mostly adjacent to river inflows. Plankton species composition has not exhibited major changes after 40 yr, but abundance has at least doubled, probably due to eutrophication. Several times more planktonic crustaceans were found in the western part of the lake, affected by sedimentary drainage, than in the eastern part, influenced by the Precambrian Shield. The plankton community in a lake as large as Lake Winnipeg can be affected by differences in climate within its shores. Midsummer epilimnion temperature was the single best parameter predicting crustacean abundance in Lake Winnipeg and other North American great lakes and, combined with phosphorus loading, explained 97% of variance.
Hepatic 7-ethoxyresorufin-O-deethylase activity, plasma steroid hormone concentrations, and liver bioassay-derived 2,3,7,8-TCDD toxic equivalent concentrations in wild white sucker (Catostomus commersoni) caged in bleached kraft pulp mill effluent
Authors: Heuvel M. R. van den , Dixon D. G. , Munkittrick K. R. , Servos M. R. , Kraak G. J. Van Der
Published: April 2008

Prespawning male white sucker (Catostomus commersoni), captured near Jackfish Bay, Lake Superior (exposed to bleached kraft pulp mill effluent (BKME)), and Mountain Bay (reference) were caged in the BKME receiving area for 2, 4, and 8 d. Initially, the hepatic 7-ethoxyresorufin-O-deethylase activity was similar in fish from both BKME and reference sites and, upon BKME exposure, increased 20-fold at both sites after 2 d. The H4IIE cell culture bioassay was used to measure 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent concentration (TEC) in sucker liver extracts. H4IIE bioassay-derived TECs from Jackfish Bay sucker showed no significant treatment differences; combined TECs for all treatments averaged 51.1 pg∙g−1. Mountain Bay sucker liver TECs were initially significantly less (4.64 pg∙g−1) than the Jackfish Bay TECs but did show a significant, fivefold increase when fish were exposed to effluent. Mountain Bay and Jackfish Bay 8-d BKME-exposed fish showed no uptake of TECs calculated from directly measured polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) during this exposure. The results suggest that PCDDs and PCDFs are not responsible for the mixed function oxidase induction observed. Handling stress caused rapid reduction of the plasma steroids testosterone and 11-ketotestosterone, confounding any possible BKME effect.
Application of the bomb radiocarbon chronometer to the validation of redfish Centroberyx affinis age
Authors: Kalish John M.
Published: April 2008

Validation of methods used to estimate fish age is a critical element of the fish stock assessment process. Despite the importance of validation, few procedures are available that provide unbiased estimates of true fish age and those methods that are available are seldom used. The majority of these methods are unlikely to provide an indication of the true age of individual fish, data that are best suited to the validation process. Accelerator mass spectrometry analyses of radiocarbon in selected regions of Centroberyx affinis otoliths were used to validate the age estimation method for this species. Radiocarbon data from the otoliths of C. affinis with presumed birth dates between 1955 and 1985 described the increase in ocean radiocarbon attributable to the atmospheric detonation of nuclear weapons in the 1950s and 1960s. The results confirm the longevity of C. affinis and demonstrate the effectiveness of the bomb radiocarbon chronometer for the validation of age-estimation methods.
Variations in the contribution of transport to changes in planktonic animal abundance: a study of the flux of fish larvae in Conception Bay, Newfoundland
Authors: Pepin P. , Helbig J. A. , Laprise R. , Colbourne E. , Shears T. H.
Published: April 2008

We investigated the magnitude of short-term variations in the flux of several species of fish larvae in Conception Bay, Newfoundland, determined the contribution of these fluxes to changes in the abundance of these species, and assessed the factors that may be causing the variations in these fluxes. The net effect of transport ranged from a daily influx of 5.8% to a daily efflux of 6.2% from the population. Short-term variations in transport were associated with variations in wind stress. The contribution of transport to variations in population abundance ranged from 12 to more than 75% of the average daily rate of change in numbers for the different species. The contribution of physical processes to estimated mortality rates is variable and can have a significant impact on the investigation and interpretation of potential biological processes (e.g., predation and starvation) influencing the survival of larval fish. We predicted that the average correction to the instantaneous mortality rate due to advection and diffusion should be proportional to A−1/2, where A is the area of system under study. This highlights the susceptibility of small systems to estimation error of mortality rates caused by short-term variations in physical forcing.
Response of Mysis relicta population dynamics and productivity to spatial and seasonal gradients in Lake Ontario
Authors: Johannsson Ora E.
Published: April 2008

Spatial and temporal patterns of production, density, reproductive status, and size composition of Mysis relicta in Lake Ontario were analyzed in relation to predation and physical conditions. Two whole-lake (May, November) surveys and one partial (August) survey were conducted in 1990. Spatial patterns were related to lake depth. Abundance increased with depth of sampling stations, particularly between 20 and 100 m. At station depths >100 m, the percentage of females carrying eggs and mean female size were constant, but the number of eggs per female increased with station depth. During the winter, the density–depth relationship weakened, apparently through the action of storms and currents, but strengthened again during the summer. Mysids >9 mm in length tended to move to deeper water during the summer. The distributions of predatory fish (alewife, smelt, and sculpin) suggest that depth-related patterns in the mysid population may be due to differences in predation rates with depth and season as well as to horizontal movement. Whole-lake production was estimated to be between 412.91 and 506.82 × 108 g dry weight: most production occurred between 100 and 200 m depth. Growth rate was similar in all regions of the lake.
Tunnels in bedded rock with high horizontal stresses
Authors: Lo K. Y. , Morton J. D.
Published: April 2008

Sustained growth in urban development in southern Ontario has led to an increased activity in tunnelling in rocks. These sedimentary rocks are bedded and anisotropic in behaviour, In situ horizontal stresses considerably higher than the vertical overburden pressure exist in these rock formations. The combination of these two factors, together with the difficulties encountered in recent tunnelling projects, necessitates a reappraisal of current design concepts.Theoretical studies show that, because of these two factors, high stress concentration occurs at the crown and invert, causing failure in the weaker layers of the bedded rocks. In addition, the pattern and sense of movement are reversed when compared to 'normal' conditions of in situ stress state.Field observations made in three tunnels are described. The instability at the roof and floor and the observed pattern of radial displacements are consistent with the approach employed.Some requirements for temporary support under these conditions are outlined. Available field data on the timedependent deformation of these openings are presented and the consequent influence on the choice of permanent lining is discussed.
Cartographie géotechnique ville de Bécancour
Authors: Maranda Rémy
Published: April 2008

The geotechnical map of a region comprises several documents including the map of surficial deposits, depth of overburden, natural slopes and hazards, bedrock contours and geology, synthesis and land use. The land use map reproduces the other documents and shows the areas appropriate for development as a function of the soil bearing capacity, ground and slope stability, ease of excavation, etc.The maps are prepared from available information such as reports, maps, and field data obtained from borings, penetration and vane tests, and geophysical surveys. [Journal translation]
Friction and end bearing tests on bedrock for high capacity socket design
Authors: Rosenberg Peter , Journeaux Noel L.
Published: April 2008

Rock sockets are used to transfer axial loads to bedrock by a combination of periferal contact bond and end bearing. The load distribution with embedded depth in relation to rock properties actually measured is discussed. Case histories are presented.The results of full scale and bearing and friction tests carried out on various rock types are given. A relation between the unconfined compression strength of rock and the developed concrete to rock bond value is reported.
Resilient modulus of cohesive soils and the effect of freeze–thaw
Authors: Lee Woojin , Bohra N.C. , Altschaeffl A.G. , White T.D.
Published: April 2008

Resilient modulus tests were performed on five cohesive soils sampled from the subgrades of in-service pavements. The stress at 1% strain in the unconfined compression test (Su1.0%) was found to be a good indicator of the resilient modulus (MR), and an empirical relationship between MRand Su1.0%was obtained. The proposed relationship itself is not affected by the changes in subgrade after construction and, therefore, is applicable to as-compacted and in-service subgrade conditions. Closed-system freeze–thaw tests were also performed and the effect of freeze–thaw on the resilient modulus was studied. There is a negligible effect of freeze–thaw, without ice lens formation, for soils having values of Su1.0%less than 8 psi (55 kPa), while the effect of freeze–thaw increases as the value of Su1.0%increases. For example, a soil with a value of Su1.0%greater than 15 psi (103 kPa) would exhibit more than 50% reduction in resilient modulus due to the effect of freeze–thaw. The resilient modulus of frozen cohesive soil is independent of the repeated deviator stress. Key words : resilient modulus, subgrade, pavement, freeze–thaw.
Fundamental formulation of electrokinetic extraction of contaminants from soil
Authors: Yeung Albert T. , Datla Subbaraju
Published: April 2008

Electro-osmosis and ionic migration are the basic cleanup mechanisms in the electrokinetic extraction of contaminants from fine-grained soils. These are coupled flows as the flows of fluid and contaminants are driven by an externally applied electrical gradient. Moreover, other electrochemical reactions will occur simultaneously during the process. The most pronounced effect is the generation of pH gradient in the soil. The change of pH in the pore fluid can have a significant impact on the degree of sorption and desorption of chemicals on soil particle surfaces, complexes formation and precipitation of chemical species, and dissociation of organic acids; thus affecting the feasibility and efficiency of the cleanup technique tremendously. An attempt is made to formulate the coupled flows of ionic contaminants and the resulting change of pH in the pore fluid during the electrokinetic extraction process. The coupled flows of contaminants are formulated by the formalism of nonequilibrium thermodynamics. The pH is determined as a function of time and space by maintaining electrical neutrality throughout the system all the times. A numerical model NEUTRAL is developed to simulate the processes. The good agreement between computed and experimental results published in the literature indicates that the approach is a valid step toward a better understanding of the physics and chemistry involved during electrokinetic treatment of contaminated soils. Key words : electrokinetics, in situ remediation, contaminated soil, coupled flows, electrochemistry, nonequilibrium thermodynamics.
Cyclic direct simple shear testing of a Beaufort Sea clay
Authors: McCarron W.O. , Lawrence J.C. , Werner R.J. , Germaine J.T. , Cauble D.F.
Published: April 2008

Results are presented for undrained direct simple shear tests on a Beaufort Sea cohesive soil. Monotonic and one-way cyclic loading response characteristics are identified for a number of loading scenarios. The critical level of repeated loadings (CLRL) is determined for two overconsolidation ratios from tests having 30 000 cycles of loading. Postcyclic strength tests indicate that one-way cyclic loadings not causing failure have a strain-hardening effect on the material. High strain-rate testing is found to increase soil strength by as much as 40% compared with typical testing strain rates. Key words : strength, cyclic testing, clay, simple shear, strain rate.
Modelling and field measurements of water percolation through an experimental soil cover on mine tailings
Authors: Woyshner Mark R. , Yanful Ernest K.
Published: April 2008

A composite soil cover constructed on acid-producing tailings was evaluated for its ability to retain a high degree of water saturation and low hydraulic conductivity. The cover consisted of a 60 cm thick, compacted, nearly saturated, varved clay placed between two sand layers, each 30 cm thick. A final 10 cm thick gravel layer was placed on the upper sand layer to minimize erosion. The Hydrologic Evaluation of Landfill Performance (HELP) model and a finite-element flow model (SEEP/W) were applied, and the results corroborated with field measurements of percolation and soil-water content. Modelling predictions indicate that 4% of precipitation will percolate through the cover and that the intermediate clay layer will retain a high degree of saturation after a 20 year simulation. Four years of field monitoring also indicate that 4% of precipitation percolates through the cover and that the clay retains its high saturation. These results suggest that a properly designed and constructed soil cover can be effective in reducing acid production in reactive mine tailings. Key words : acid-producing tailings, soil cover, water saturation; capillary barrier, hydrologic processes.
Hydraulic conductivity of natural soils permeated with acid mine drainage
Authors: Yanful Ernest K. , Shikatani Keith S. , Quirt David H.
Published: April 2008

Three different soils from Canadian mine sites were evaluated in the laboratory for their compatibility with acid mine drainage (AMD). The key parameter evaluated was the hydraulic conductivity, k, measured with a flexible wall triaxial permeameter at low hydraulic gradients ranging from 15 to 60. An undisturbed varved clay gave a k value of 1–1.5 × 10−7 cm/s when permeated with both simulated pore water and two pore volumes of AMD. The k values for compacted tills were of the order of 2 × 10−8 cm/s and 3 × 10−7 cm/s with both reference permeant (0.01N CaSO4) and AMD. The data indicated that, while AMD did not change k, it may have dissolved primary minerals such as chlorite, smectite, plagioclase feldspars, illite, and K-feldspar, in a decreasing order of susceptibility. The dissolution and concomitant precipitation of secondary minerals appeared to have maintained or preserved the soil void ratio, resulting in no net measurable volume change during k testing. The degree of AMD attack was found to be related to its contact time with the soil; one of the tills produced acidic effluents after 5.5 pore volumes or 243 days of permeation, the longest testing time used. The AMD permeation also reduced the till's cation exchange capacity by more than 50%. There was clear evidence that AMD permeation could eventually deplete soil buffering capacity to the extent that heavy metals such as Zn would no longer be attenuated. Soils intended to be used in the design and construction of barriers (for example, slurry walls and dam cores) against AMD seepage should, therefore, be tested for compatibility with the intended AMD. Such compatibility testing should be conducted over a long period to establish chemical equilibrium of key mobile contaminants such as Zn. This will improve design confidence and also avert or minimize detrimental, postconstruction changes requiring costly remedial actions. Key words : hydraulic barriers, hydraulic conductivity, acid mine drainage, mineral alteration, buffering capacity depletion.
Changes in dielectric permittivity and shear wave velocity during concentration diffusion
Authors: Santamarina J.C. , Fam M.
Published: April 2008

This paper documents a study of concentration diffusion with complementary mechanical and electromagnetic wave measurements. The paper starts with a review of the fundamentals of interparticle forces and wave–geomedia interaction. Experimental data were collected during the diffusion of a high-concentration solution of potassium chloride through different soils with different boundary conditions. Bentonite and kaolinite contracted during diffusion. The interaction between the concentration gradient, true interparticle forces, and fabric changes produced a pore-water pressure front that advanced ahead of the concentration front. The complex permittivity changed with the advance of the concentration front, reflecting the decrease in moisture content and the increase in conductivity. Concentration diffusion affected shear wave propagation through changes in true interparticle forces. Bentonite showed a significant increase in shear wave velocity, whereas the velocity of propagation in kaolinite decreased. Published differences in the behavior of bentonite and kaolinite were compiled and hypotheses are proposed to explain observed phenomena. Key words : mechanical waves, electromagnetic waves, clays, diffusion, double layer.
In situ evaluation ofK0in eastern Canada clays
Authors: Hamouche K.K. , Leroueil S. , Roy M. , Lutenegger A.J.
Published: April 2008

An approximate value of the horizontal effective stress in an overconsolidated clay deposit is often determined from an estimate of the effective stress ratio, K0, using the equation [Formula: see text]. It is also generally considered that the α parameter is approximately equal to sin [Formula: see text]. For evaluating K0in sensitive clays of eastern Canada, a testing program has been initiated on three different sites representing a large range of overconsolidation ratios. Three different in situ devices were used: the Cambridge self-boring pressuremeter, the flat dilatometer, and hydraulic fracturing. The results show that the different techniques give essentially the same K0values. They also give K0values larger than those expected, with an α parameter typically between 0.75 and 1.15. Key words : clay, dilatometer, horizontal stress, hydraulic fracturing, in situ tests, self-boring pressuremeter.
Effets de cycles de gel–dégel sur les propriétés d'une argile sensible
Authors: Roy M. , Rochelle P. La , Leroueil S. , Konrad J.M. , Bergeron G.
Published: April 2008

A laboratory study of the evolution of the behaviour of a sensitive clay under many freeze–thaw cycles is presented; it follows the laboratory study of Leroueil et al. (1991) and the field study of Roy et al. (1992). The physical properties of the clay have been followed by means of consistency and permeability tests after each freeze–thaw cycle, and the mechanical behaviour has been assessed by means of falling cone, oedometer, and consolidated isotropically undrained triaxial tests. The changes in internal structure have been observed by means of the scanning electron microscope and the mercury porosimeter. The results show that the changes in properties are significant during the first three freeze–thaw cycles and hardly significant during the following cycles. The structure change can be explained by the high suction that develops during the generation of ice lenses behind the frost front. Key words : clay, freeze–thaw, shear strength, permeability, heaving, settlements. [Journal translation]