bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal and intersexual variations in the use of space with regard to social organization in the woodchuck (Marmota monax)
Authors: Ferron J. , Ouellet J. P.
Published: March 2009

The use of space by adult woodchucks (Marmota monax) in a field habitat has been studied by radiotracking. Results are analysed according to two periods, each lasting 50 days, preceding and following the onset of natal dispersal; within each period a finer analysis is performed on a 10-day basis. Variations in the use of space within a daily period are also analysed. The number of burrows used, the average distance between burrows successively occupied by the same animal, and home-range size are considered. During the period preceding natal dispersal, adult males are more mobile and have a larger home range than do females accompanied by young. During the period of natal dispersal, the pattern of space use is similar for adults of both sexes, females becoming less sedentary and males reducing their movements. The onset of natal dispersal is a major event affecting the pattern of space use by females accompanied by young. As hibernation approaches, there is a decrease in the amplitude of movements between burrows. Results also suggest that woodchucks are territorial. Comparison with other woodchuck populations reveals differences in social organization that may be related to population densities.
Behavioural context and possible function of scent marking by cheek rubbing in the red squirrel (Tamiasciurus hudsonicus)
Authors: Ferron Jean , Ouellet Jean-Pierre
Published: March 2009

A contextual analysis of scent marking by cheek rubbing in wild red squirrels (Tamiasciurus hudsonicus), based on the study of behavioural time budgets and sequences, is presented. Scent-marking rates do not differ significantly between adult males and females. Comparison of the relative frequency of occurrence of each behaviour pattern in a scent-marking context with the relative frequency of these patterns in all other contexts reveals that locomotion, alertness, grooming, food carrying, and gnawing have a higher probability of occurrence when there is cheek rubbing. These results concur with earlier findings in captivity. Contextual analysis in the wild clearly indicates low association of cheek rubbing with social context and greater use of this behaviour at grooming and resting sites and along the path used by the marking animal. This suggests that cheek rubbing is mainly self-oriented to maintain the animal's familiarity with its home range. This scent-marking behaviour may also be used to advertise occupancy of a given territory to conspecifics.
Nematodirus archari (Nematoda: Trichostrongyloidea) from ruminants in North America with a description of the synlophe and the female
Authors: Rickard Lora G. , Lichtenfels J. Ralph
Published: March 2009

The synlophe of specimens of Nematodirus archari from North America is described and used to identify females of this species for which the first description is provided. Differentiation of N. archari from congeners in North America is based on an array of characters, including the pattern of the synlophe and the form and structure of the spicule tip and bursa. These characters also distinguish N. archari from the exotic congeners with the exception of Nematodirus ibicis and Nematodirus bioccai, from which it cannot be reliably differentiated. Discussion of the importance and use of the synlophe in studies of trichostrongyloid nematodes, particularly for the genus Nematodirus, is presented.
Glomerular filtration rate in weaned elephant seal pups during natural, long term fasts
Authors: Pernia S. D. , Costa D. P. , Ortiz C. Leo
Published: March 2009

Low urine output (< 200 mL/day) seen in weaned elephant seal pups is consistent with the physiological necessity of strict water conservation during periods of protracted, natural fasts. However, urine output represents only the difference between glomerular filtration rate (GFR) and tubular reabsorption and thus provides no information about the absolute magnitude of these parameters or their role in homeostatic regulation during the fast. We measured GFR, and extracellular volume (ECV) and estimated tubular reabsorption in seven pups that had been fasting > 6 weeks and in three others that had begun to feed in captivity using standard [3H]inulin and [125I]iothalamate clearance techniques. In fasting pups, GFR and ECV ranged from 78.9 to 135.2 mL/min and from 6.3 to 15.4 L, respectively. The GFR values are 59–91% [Formula: see text] of that predicted by standard body mass allometry. These data suggest that (i) low urine output is a consequence of tubular reabsorption rather than depressed GFR; (ii) a small but significant N and electrolyte load resulting from oxidation and reorganization of body tissue during development requires near "normal" renal function despite the potential loss of water from excess urine formation.
Some ectoparasitic trichodinids from Atlantic cod, Gadus morhua L., with a description of Trichodina cooperi n.sp.
Authors: Poynton S. L. , Lom J.
Published: March 2009

Trichodina murmanica Polyanskiy, 1955 (= Trichodina domerguei subsp. saintjohnsi Lom and Laird, 1969) and Trichodina cooperi n.sp. were commonly encountered on skin and fins of Atlantic cod, Gadus morhua L., near Halifax, Nova Scotia, Canada. A third species of Trichodina, probably new, was recorded from the skin of one fish. This is believed to be the first report of the genus Trichodina from the body surface of gadoid fish from eastern Canada, and the known geographic range of T. murmanica is extended. Trichodina cooperi n.sp. has an adoral ciliary spiral of 370–380° and is relatively large, the mean diameter of the body is 110 μm, of the adhesive disc (with dark center), 95 μm, and of the denticulate ring, 59 μm. The denticulate ring consists of 24–29 denticles (usually 27), with 7–9 radial pins per denticle. Each denticle has a broad blade, a large central part, and a slightly curved thorn of moderate to broad width, with a central rib when mature. The thorn is approximately twice the length of the blade. The horseshoe-shaped macronucleus has a diameter of 80.0 μm and the micronucleus is in the +y position. Trichodina spp. infected 26% of 39 wild fish 20 to < 60 cm long. Most wild fish yielded less than five ciliates per 24 × 50 mm smear.
Thyroid hormone levels in flow-challenged adult salmon (Salmo salar L.)
Authors: Youngson A. F. , McLay H. A.
Published: March 2009

Circulating levels of thyroid and steroid hormones in salmon (Salmo salar) that had spent one winter in seawater have been determined in fish at rest and after a 4-h exposure to increased water velocity. The responses of fish of both sexes to this challenge were examined in April and June, while the fish were in seawater; sexually maturing males only were examined in freshwater in August and November. Mean thyroxine levels in resting controls ranged from 8.8 to 15.2 ng/mL. Mean thyroxine levels in challenged fish were significantly greater on each occasion. In male fish, 11-oxotestosterone levels were reduced after challenge, while androstenedione levels in females remained unchanged. In April, thyroxine levels after challenge were correlated with 11-oxotestosterone levels in males and with androstenedione levels in females.
Dynamics of a grizzly bear population during a period of industrial resource extraction. III. Natality and rate of increase
Authors: McLellan Bruce N.
Published: March 2009

Reproductive parameters and rate of increase were estimated for a grizzly bear (Ursus arctos) population in southeastern British Columbia during a period of timber harvest and gas exploration, 1979–1987.I hypothesized that these activities would be detrimental to the population and predicted a negative rate of increase. There was an average of 2.26 cubs in 31 litters. The average of nine interbirth intervals was 2.67 years, and the average age at which five females produced their first litter was 6 years. The population's annual reproductive rate calculated by three methods averaged 0.86 cubs per adult female. By iteration of the Lotka equation, the best estimate of the exponential rate of increase was 0.081. Industrial activities did not appear to have a significant detrimental effect on the grizzly bear population in the Flathead Valley during the period of study but the roads built provided easy access for hunters and poachers.
High incidence of limb autotomy in a crab population from a coastal lagoon in the province of Buenos Aires, Argentina
Authors: Spivak Eduardo D. , Politis María Angélica
Published: March 2009

A total of 2243 individuals of the shore crab Cyrtograpsus angulatus were obtained from Mar Chiquita lagoon, in the province of Buenos Aires, Argentina, from August 1986 to May 1987. Adult crabs were found at low tide on stones or on the beach, whereas juveniles were found beneath stones. Each crab was measured, sexed, and examined for the incidence of autotomized and regenerated limbs. Crabs exhibited a high, although size dependent, incidence of autotomy that was higher in female than in male adult crabs; the lowest values were found in juveniles. Crabs lost from one to seven limbs; both sexes showed a higher number of multiple, and a reduced number of single, autotomies than expected. The highest incidence occurred in the longest and most exposed limbs: the third and fourth walking legs; the chelae showed a reduced incidence. Crabs with multiple autotomy lost adjacent rather than nonadjacent limbs. The regeneration of a lost limb did not depend on the number of autotomies in small crabs, but it did in the case of large crabs which frequently did not regenerate some of their lost limbs. The five pairs of limbs had similar, size dependent, incidence of regeneration. Adult crabs with multiple autotomies had a lower proportion of synchronous regeneration of adjacent limbs. The high incidence of autotomy in this population of C. angulatus is discussed and alternative explanations of its causes are proposed, namely, inter- and intra-specific predation and agonistic behaviour.
Neustonic feeding by juvenile salmonids in coastal waters of the Northeast Pacific
Authors: Brodeur Richard D.
Published: March 2009

The near-surface macrozooplankton fauna off the Washington and Oregon coasts is described from a series of quantitative neuston hauls collected during June, July, and September 1984. Euphausiids, decapod larvae, hyperiid amphipods, and larval fishes were the dominant marine taxa represented. Insects of terrestrial origin were very common and occurred in high abundances, especially during the July and September cruises off Oregon, and their occurrence was coincident with unusual wind patterns. The neuston catches were quantitatively compared with the diets of juvenile coho (Oncorhynchus kisutch) and chinook (O. tshawytscha) salmon collected at the same stations and within the same cruises. There was an overall resemblance between the taxa in the neuston and stomachs of these salmon juveniles, although the larger organisms appeared to be consumed preferentially. Predominantly neustonic taxa also occurred in the diets of other juvenile salmonids and adult coho salmon collected concurrently, but these other predators did not appear to utilize neustonic prey to the same extent as coho and chinook juveniles.
Head size and the foraging behaviour of animal-eating bats
Authors: Fenton M. Brock
Published: March 2009

Regression analysis and analysis of covariance on linear measurements of body size (forearm length), head length (condylo-canine length), and length of maxillary toothrow showed significant differences among 245 species of bats in 12 families. The linear measurements of the 194 animal-eating species, namely those in the Emballonuridae, Vespertilionidae, Phyllostominae, Rhinolophidae, Nycteridae, and Megadermatidae, showed that species of bats with longer heads had longer maxillary tooth-rows. The data also showed that some animal-eating bats which are presumed to forage from continuous flight have proportionally shorter heads than species that use sally foraging. Molossids, species specialized for rapid, efficient flight, had longer heads than expected, whereas sally-foraging hipposiderids had shorter heads. I use the data to predict that head length in animal-eating bats affects the size of prey selected.
Egg cannibalism and the reproductive strategies of threespine sticklebacks (Gasterosteus aculeatus) in a coastal British Columbia lake
Authors: Hyatt K. D. , Ringler N. H.
Published: March 2009

Patterns of egg eating and their association with differences in sex, size, abundance, and reproductive status of free-ranging sticklebacks from Kennedy Lake, British Columbia, were examined as a means of identifying the relative importance of filial cannibalism or heterocannibalism as the source of eggs in the diet. Egg cannibalism was a common event: 23.0 and 11.2% of the sticklebacks examined in 1982 and 1985, respectively, had engaged in egg eating. Eggs were a substantial part of the overall diet of the stickleback population during two breeding seasons: 27.4% of the diet of all fish by weight in 1982, 32.8% of the diet by volume in 1985. Our results do not support Rohwer's contention that filial cannibalism is the source of most eggs in stickleback diets. Ten out of 11 predictions based on the filial cannibalism hypothesis were rejected, whereas the 11th was compatible with either the filial cannibalism hypothesis or the alternative heterocannibalism hypothesis. We conclude that heterocannibalism, not filial cannibalism, is the major source of eggs in the diet of Kennedy Lake sticklebacks. We suggest that nest raiding and egg cannibalism may minimize time spent foraging and maximize time spent on activities that increase the probability of initiating and successfully completing one or more reproductive cycles. Although the benefits of nest raiding and cannibalism are most obvious for populations breeding under conditions where food supplies clearly limit their potential reproductive output, the benefits may still apply even under conditions where alternative prey sources appear to be abundant.
Formations of foraging sperm whales, Physeter macrocephalus, off the Galápagos Islands
Authors: Whitehead Hal
Published: March 2009

Groups of sperm whales, composed mostly of females and their offspring, which were tracked in the waters off the Galápagos Islands during 1985 and 1987, generally foraged in ranks about 550 m long aligned perpendicular to the direction of travel. While at the surface, they swam in clusters containing a mean of 1.7 whales, and these clusters were spaced out along the rank. When feeding at depth the whales were estimated to be about 40 m apart. The ranks travelled at approximately 2 kn (3.7 km/h) and maintained their headings for periods of several hours. Individuals showed some coordination in the timing of their dives. There were no indications that individual whales, mature males, or first-year calves were more likely to be found in particular positions along the rank. The major benefits for individuals of foraging in a rank are probably gathering information about prey densities, avoiding mutual interference, and possibly catching prey that elude other members of the formation.
Stomach contents of harbour porpoises, Phocoena phocoena (L.), from the Bay of Fundy
Authors: Recchia Cheri A. , Read Andrew J.
Published: March 2009

We examined contents from stomachs of 127 harbour porpoises (Phocoena phocoena) caught in groundfish gill nets in the western Bay of Fundy during June to September, 1985–1987. Relative importance of prey species was assessed using both numerical and caloric measures. Atlantic herring (Clupea harengus) was the most important prey species, contributing 80% of the total caloric intake, with some spatial and temporal variation. Silver hake (Merluccius bilinearis) and Atlantic cod (Gadus morhua) were also important, but together comprised only 17% of the total caloric intake. No differences were found in relative prey importance between adult porpoises of different reproductive conditions, but lactating females ingested more fish and had a significantly higher total caloric intake than nonlactating females or mature males. The diet of porpoises collected from the same area in 1969–1972 consisted of a higher proportion of pelagic prey species and a lower proportion of demersal species. This may be attributed to differences in capture method, as the earlier sample of porpoises was collected at the surface, while the present animals were captured at depths of 45–100 m.
Humpback whales, Megaptera novaeangliae, and other cetaceans on Virgin Bank and in the northern Leeward Islands, 1985 and 1986
Authors: Mattila David K. , Clapham Phillip J.
Published: March 2009

Vessel surveys were conducted during the winters of 1985 and 1986 to investigate the abundance and distribution of humpback whales on Virgin Bank and in the northern Leeward Islands. Nonrandom track surveys conducted on Virgin Bank in 1986 produced observed densities ranging from 0 in late January and mid-March to 0.082 whales/naut. mi.2 (1 naut. mi. = 1.852 km) in mid and late February. The number of whales sighted per hour on Virgin Bank was similar for both 1985 and 1986, with a peak value of more than 1.3 whales/h in mid to late February. On Anguilla Bank, the number of whales sighted per hour ranged from 0 in late March to 0.66 in mid-February. Comparisons with data from Mona Passage, Puerto Rico, suggest a possible shift in abundance from east to west, with the peak abundance occurring in the second half of February on Virgin Bank and at the beginning of March in Puerto Rico. A total of 105 whales were individually identified during the study. Photographic matches demonstrate that Virgin Bank is used by whales from all of the major known western North Atlantic feeding grounds, and suggest that this may also be true of Anguilla Bank. Overall, the data suggest that Virgin Bank may be more important as a mating and calving ground than Mona Passage, Puerto Rico, but considerably less important than Silver Bank. Sightings of other cetacean species in the study area are summarized, and include observations of a minke whale (Balaenoptera acutorostrata) mother–calf pair on Anguilla Bank.
Revision and phylogenetic analysis of the North American species of Telorchis Luehe, 1899 (Cercomeria: Trematoda: Digenea: Telorchiidae)
Authors: Macdonald Cheryl A. , Brooks Daniel R.
Published: March 2009

Telorchiids are plagiorchiform digeneans inhabiting the intestines of freshwater turtles, snakes, and salamanders. Previous systematic revisions of the group have been problematical because of a lack of information on intraspecific morphological variation. In the present study, examination of substantial numbers of specimens leads to the conclusion that 11 of the 31 nominal species of Telorchis reported from North America are valid. Numerical phylogenetic systematic analysis based on 18 homologous series and 30 total characters resulted in a single tree with a consistency index of 94%, due to two homoplasious characters. To maintain a classification consistent with the phylogenetic tree that is also most similar to previous nomenclature, only one of four previously proposed genera is recognized. The two relatively most plesiomorphic species are found in salamanders, whereas the rest inhabit amniotes (specifically turtles and snakes). Five of the nine species inhabiting amniotes appear to have co-speciated with their hosts. Two of the remaining four species appear to have evolved sympatrically via host switching from turtles to snakes. The remaining two species appear to have evolved sympatrically and without host switching, facilitated by mechanical premating isolation due to the appearance of an apomorphic genital pore position. Using the number of host species inhabited as an index of host specificity, it appears that the more recently evolved the species of Telorchis, the fewer hosts it inhabits.
Improved technique for fish specimen photography in the field
Authors: Holm Erling
Published: March 2009

The causes of and remedies for annoying background shadows on photographs taken using the technique described by Emery and Winterbottom are outlined. A table is presented indicating exposures, flash positions, aquarium size, and required extension tubes for specimens of 15–420 mm total length. Three recently published fish photography techniques are briefly reviewed. Solutions to problems experienced with power sources, reflection, and depth of field in photographing small subjects are discussed.
Temporal and thermal aspects of hibernation of black rat snakes (Elaphe obsoleta) in Ontario
Authors: Weatherhead Patrick J.
Published: March 2009

Radio telemetry was used to determine the time of emergence from and entry into communal hibernacula by black rat snakes (Elaphe obsoleta obsoleta) and to gain insight into the proximate factors involved in these behaviours. Emergence in mid-April appears not to be triggered by marked reversal of thermal gradients in the hibernaculum as has been proposed, or by changes in day length. By default, endogenous rhythms seem most likely to be responsible. Entry in early October may be triggered in part by outside temperatures. Even with the limited sample size used in this study, considerable individual variation in emergence and entry patterns was observed. Through the winter the snakes steadily got colder, reaching their coldest point just before emergence. The 7-month hibernation period was substantially longer than has been observed for more southerly populations. Given the period of inactivity immediately before and following hibernation, the active period is less than 4 months, which perhaps explains why the population in this study is the northernmost in the species' distribution.
Seasonal biology of Winthemia fumiferanae Toth. (Diptera: Tachinidae), a larval–pupal parasitoid of the spruce budworm (Lepidoptera: Tortricidae)
Authors: Hébert Christian , Cloutier Conrad , Régnière Jacques , Perry David F.
Published: March 2009

The phenology of Winthemia fumiferanae Toth. (Diptera: Tachinidae), a larval–pupal parasitoid of the spruce budworm, was studied in Quebec to evaluate its synchrony with the host. Adult emergence showed protandry and occurred when budworm larvae were in the second to the fifth instar. In Malaise trap catches, males were dominant during the emergence period but as this ended, females became dominant and remained so for the rest of the season. Females emerged with undeveloped ovaries and abundant fat reserves. The maturation of eggs was completed within 2 weeks after emergence and coincided with the appearance of sixth-instar budworm larvae. Potential fecundity was correlated with female body size. Females deposited, on average, 32% of potential eggs, many oocytes remaining undeveloped in the ovarioles. Oviposition on spruce budworm larvae was synchronized with peak abundance of the sixth instar. Winthemia fumiferanae prepupae, among other dipteran parasitoids of the spruce budworm, were the last to drop to the ground. There was evidence of a partial second generation but its incidence was below 1% under field conditions. More than 95% of the W. fumiferanae puparia were found between 0 and 40 mm below the soil surface. The importance of W. fumiferanae in spruce budworm outbreaks and factors that may reduce its efficacy as a mortality agent are discussed.
The habitat templet and life history strategies of pond skaters (Heteroptera: Gerridae): reproductive potential, phenology, and wing dimorphism
Authors: Spence John R.
Published: March 2009

Reproductive traits, diapause, and wing dimorphism of four pond skater species occurring in central Alberta, Canada, are explained as adaptive responses to a complex of habitat features. Species using temporary habitats had greater fecundity, but habitat permanence alone was a poor predictor of reproductive longevity, preoviposition period, or reproductive rate. Fecundity and longevity were significantly lower and more variable in direct than in diapaused breeders. There was no geographical or annual variation in fecundity, suggesting that values observed are good measures of reproductive potential. Overwintered females of species from temporary habitats (Gerris buenoi and Limnoporus dissortis) lived longer than those from more permanent habitats (G. comatus and G. pingreensis), and, concomitantly, are able to spread reproduction over several ponds. Proportion of summer-generation bugs breeding without diapause was inversely related to habitat permanence for the Gerris species, but few nondiapause breeders occurred in L. dissortis. Diapause was not averted consistently by exposure to increasing long-day photoperiods, and sensitive stage for diapause induction varied within all species. In G. pingreensis and L. dissortis many individuals reaching the adult and fifth instar by the solstice diapaused. Diapause and wing morphism were associated only loosely in the dimorphic species. Many apterous G. pingreensis entered diapause despite early emergence. Wing morph in G. pingreensis is determined genetically but is not based in simple Mendelian inheritance. Flightless bugs occur mainly among direct breeders in G. buenoi and G. comatus but many direct breeders were macropterous. Wing morph is influenced by a photoperiod switch in G. buenoi, but there is also genetic variation. There was no significant difference in total fecundity, longevity, or juvenile development time between wing morphs of the same generation in either G. buenoi or G. pingreensis. However, flightless females had shorter preoviposition periods, leading to greater egg production over the first 20 days of reproductive life. Gerrid life histories are adaptions to a complex of factors, including but not confined to habitat stability. Other aspects of the habitat templet such as the impact of natural enemies and food input should be considered.
Responses of captive African elephants to playback of low-frequency calls
Authors: Langbauer Jr. William R. , Payne Katharine B. , Charif Russell A. , Thomas Elizabeth M.
Published: March 2009

We conducted a series of playback trials with captive African elephants to identify behaviors that might indicate perception of calls by conspecifics. Our findings were as follows. (i) The elephants responded clearly to playbacks of prerecorded low-frequency elephant calls. Responses included, in rough sequence, lifting and stiffening of ears, vocalization, walking or running towards the concealed speaker, clustering in a tight group, and remaining motionless ("freezing"), with occasional scanning movements of the head. The occurrence of each of these behaviors increased substantially immediately after the playbacks. (ii) Elephants responded both to full-bandwidth playbacks and to playbacks of calls in which most of the energy above 25 Hz was filtered out, simulating the effect of frequency-dependent attenuation over distance. (iii) Elephants did not respond to a pure-tone control stimulus similar in frequency and intensity to the filtered elephant calls. Thus, the observed responses to elephant calls were not merely responses to an unexpected stimulus, but probably indicate recognition of a biologically meaningful signal.
The structure and probable function of the internal cuticular parts of Johnston's organ in mosquitoes (Aedes aegypti)
Authors: Belton Peter
Published: March 2009

Although the flagellum of the antennae of mosquito-like insects is known to vibrate in response to sounds, descriptions of the cuticular parts that suspend it in the second antennal segment are somewhat contradictory and incomplete. The complex structures that attach the base of the flagellum to the pedicel and its sense cells in Aedes aegypti (L.) (Diptera: Culicidae) are described. They are consistent with the functions of suspending the flagellum firmly in the pedicel and of anchoring the sheathing rods of the acoustically sensitive scolopidia while their dendrites are stretched or bent by the movement of the prongs.
Composition of fluid transported by locust ileum: influence of natural stimulants and luminal ion ratios
Authors: Lechleitner R. A. , Audsley N. , Phillips J. E.
Published: March 2009

Unstimulated fluid transport by everted locust ileal sacs in vitro was supported at 50% of control levels by the presence externally of any one of Na+, K+, or Cl−, whereas removal of all but trace levels of these ions reduced fluid transport to 25% of control transport rates. Stimulation of fluid transport by corpus cardiacum or fifth ventral ganglion extracts did not occur unless Cl− was present. The presence of Na+ or K+ was also required for maximum stimulation of fluid transport by these factors, the greatest stimulation occurring when the Na+:K+ ratio was 1:1. Cyclic AMP, and corpus cardiacum and fifth ventral ganglion extracts all stimulated Na+, Cl−, and K+ absorption across everted ileal sacs. Stimulation of fluid transport by these factors largely eliminated the anion deficit (Na+ + K+−Cl−) observed under unstimulated conditions. Stimulation caused large decreases in absorbate [Formula: see text] concentrations and pH concurrent with the increased absorbate Cl− levels. These results indicate a switch from low-capacity NaHCO3 plus NaCl transport under unstimulated conditions to high-capacity NaCl transport under stimulated conditions. Stimulation of fluid transport also causes a 3-fold increase in transepithelial potential (hemocoel negative), indicating stimulation of electrogenic anion (Cl−) movement to the hemocoel. These results provide the first direct evidence for hormonal control of Na+ reabsorption in insect excretory systems.
Demography of sympatric arctic and snowshoe hare populations: an experimental assessment of interspecific competition
Authors: Barta Robert M. , Keith Lloyd B. , Fitzgerald Shannon M.
Published: March 2009

Geographic distributions of arctic (Lepus arcticus) and snowshoe hares (Lepus americanus) do not overlap on insular Newfoundland, where snowshoes were introduced, or in continental North America, where both species are indigenous. We conducted a field experiment to explore the role of interspecific competition in maintaining this allopatry. In September of 1984 and 1985, single- and mixed-species populations of arctic and snowshoe hares were established as "treatments" on six islands off Newfoundland's southwest coast. Island treatments differed between years. Demographic elements of each species population were monitored as potential response variables. Neither snowshoe nor arctic hares were demographically affected by the sympatry imposed in this experiment. Survival, reproduction, recruitment, habitat use, home range size, and over-winter weight change did not differ between single- and mixed-species treatments. There were, however, major demographic responses when each species was forced to occupy only atypical habitat, i.e., habitat normally used by the other species. Thus, most arctic hares confined to forested islands died from starvation in 1–3 months, after weight losses of 20–30% and marrow-fat reductions to <15%. Such responses occurred during winter and early spring, regardless of whether snow-shoe hares were present. In contrast, arctic hares at similar densities in their typical barrens habitat maintained weight and survived well. Snowshoe hares also maintained weight when restricted to barrens, but unlike those in forest habitat, were rapidly decimated by raptor predation. We believe that lack of suitable food over winter, rather than interspecific competition, has been a major constraint on the arctic hare's ability to populate forested regions of Newfoundland, whereas heavy predation has prevented snowshoe hares from colonizing mountain and coastal barrens.
Nest architecture and brood mortality in four species of sweat bee (Hymenoptera; Halictidae) from Cape Breton Island
Authors: Packer Laurence , Sampson Blair , Lockerbie Cathy , Jessome Vincent
Published: March 2009

The nest architecture of four species of the bee family Halictidae from Cape Breton Island, Nova Scotia, was studied. Augochlorella striata and Lasioglossum (Evylaeus) comagenense constructed their brood cells in a cluster surrounded by a cavity. In the case of A. striata, the cavity-forming habit increased the rate at which the soil of the brood cell cluster dried out, relative to the surrounding soil. The year of the study was unusually dry and in midsummer the moisture content of the soil was extremely low. This weather pattern seemed to result in some mortality of A. striata brood due to dehydration, and prevented foundresses from constructing brood cells. The two other species, Lasioglossum (Evylaeus) cinctipes and Lasioglossum (Dialictus) laevissimum, did not construct brood cell clusters. All four species had shallower nests than other species with similar nest architectures for which published data are available. All species except L. laevissimum nested in association with stones at the ground surface. It was shown that brood cells of nests situated close to rocks and stones were likely to experience increased temperature, presumably resulting in a faster developmental rate for immatures. This may be important in the Cape Breton environment, which is clearly marginal for social sweat bees. Both A. striata and L. comagenense exhibited very low mortality rates in developing immatures (1 and 7%, respectively).
Changes in the abundance of small littoral-zone fishes in Lake Mendota, Wisconsin
Authors: Lyons John
Published: March 2009

Since 1900, major changes have occurred in the assemblage of small littoral-zone fishes (maximum total length < 150 mm; usually encountered in the nearshore area) that inhabits Lake Mendota, Wisconsin. A diverse assemblage that included several environmentally sensitive species has been replaced by an assemblage dominated by a single species, the brook silverside (Labidesthes sicculus), whose abundance fluctuates dramatically from year to year. Between 1900 and 1981, eight species, the pugnose shiner (Notropis anogenus), common shiner (Notropis cornutus), blackchin shiner (Notropis heterodon), blacknose shiner (Notropis heterolepis), tadpole madtom (Noturus gyrinus), banded killifish (Fundulus diaphanus), blackstripe topminnow (Fundulus notatus), and fantail darter (Etheostoma flabellare), disappeared from the lake. The blackchin shiner and banded killifish were the most abundant small littoral-zone species in 1914–1916, and remained common until the late 1960's. Their decline was associated with the invasion and explosive increase in abundance of an exotic macrophyte, the Eurasian water milfoil (Myriophyllum spicatum), in the mid-1960's. The decline and disappearance of the blackchin shiner and banded killifish in three other Wisconsin lakes was also associated with the invasion of Eurasian water milfoil. Changes in the assemblage of small littoral-zone fishes in Lake Mendota indicate environmental degradation in the nearshore area, and may have important implications for the entire fish community of the lake.
Factors affecting gas transfer in respiratory organs of vertebrates
Authors: Piiper Johannes
Published: March 2009

The ability of a gas-exchange organ to transfer respiratory gases (O2 and CO2) between the respiratory medium (air or water) and blood is quantitatively characterized by its transfer conductance, usually termed diffusing capacity, D. The problems in defining and determining D are reviewed. In a blood-perfused gas-exchange organ it is useful to consider the ratio [Formula: see text] ([Formula: see text], blood flow; β, effective solubility) which determines the relative role of diffusion limitation. Poor gas transfer may be due to functional inhomogeneities, and not to low D values. Besides the well-known ventilation–perfusion inequality, other types of inhomogeneity involving diffusion resistances in the medium may be operative. Determination of D in functionally inhomogeneous gas-exchange organs is difficult because of both modeling and measurement problems. In blood to medium transfer of CO2, particular features have been noted. First, the equilibration of CO2 between medium and blood appears to be slower than expected on the basis of high physical solubility, owing to the slowness of some steps in the CO2 exchange process (dehydration of carbonic acid, bicarbonate–chloride exchange of red cells). Second, there is controversial evidence for equilibration of pulmonary capillary blood to a CO2 partial pressure lower than that in lung gas.
Relationships among reproductive status, nutritional status, and food characteristics in a natural population of Peromyscus maniculatus
Authors: Millar John S. , Xia Xuhua , Norrie Michael B.
Published: March 2009

We compared digestibility of consumed food, dimensions of the alimentary tract, body fat and body size in relation to sex and reproductive status of overwintered adult Peromyscus maniculatus to assess the applicability of these measures of food intake and nutritional status to natural populations. Nonbreeding females were smaller than other sex and reproductive categories, but they had the largest alimentary tracts and energy reserves for their size. Lactating females were large, but they had low energy reserves and only averaged-sized alimentary tracts. Nonbreeding males ate relatively poor quality foods, had the smallest alimentary tracts for their size, and had low energy reserves. Most of these patterns were interpretable based on the known biology of this population. We conclude that these measures can provide insights into intraspecific variation in food intake and nutritional status in natural populations of Peromyscus.
COMPARATIVE STUDY OF SINGLE CRYSTAL CONSTITUTIVE EQUATIONS FOR CRYSTAL PLASTICITY FINITE ELEMENT ANALYSIS
Authors: LEE MYOUNG GYU , WAGONER ROBERT H. , KIM SUNG-JOON
Published: March 2009

Two sets of single crystal constitutive equations used for the crystal plasticity finite element analysis are comparatively investigated by simulating simple deformation of oriented single crystals. The first of these consists of conventional constitutive equations, which have been adopted for the prediction of deformation texture and their parameters are generally obtained by back-fitting polycrystalline stress-strain response. The other set uses interactions between moving dislocations on the primary slip system and the corresponding forest dislocations. The idealized Orowan hardening mechanism is adopted for the calculation of the critical force, and constitutive parameters are determined by the geometry of dislocations, thus less fitting procedure is involved. The stress-strain curves of copper single crystal are used to demonstrate how the two models work for the orientation dependent stress-strain responses.
A STUDY ON THE IMPROVEMENT OF THE ACCURACY OF A SHAVING PROCESS USING A PROGRESSIVE DIE
Authors: CHUNG WAN-JIN , HWANG KU-BOK , KIM JONG-HO , RYU HO-YEUN
Published: March 2009

Shaving is widely used as a finish process to generate a smooth sheared surface from a sheared surface originally obtained by blanking or piercing. In the sheet metal forming industry, progressive operations are commonly used to increase productivity. However, it is difficult to utilize shaving in a progressive die because a blank is dropped down after blanking. In this study, a method that addresses this issue is introduced, and the two-stage progressive operation of half-blanking and blank-shaving is suggested. For this study, a square part made by blanking and piercing is considered, and a progressive die that includes piercing, pierce-shaving, half-blanking and blank-shaving is prepared for a specimen of cold rolled steel sheet. Experiments are carried out involving the process parameters of the shaving allowance, shaving clearance and the half-blanking penetration depth. It was found that the proposed method using a progressive die offers a completely smooth sheared surface along with feasible working conditions for a cold rolled steel sheet with a thickness of 1.56 mm.
EFFECT OF HELICITY ON THE BUCKLING BEHAVIOR OF SINGLE-WALL CARBON NANOTUBES
Authors: HUH JEEHYANG , HUH HOON
Published: March 2009

Simulations of single-wall carbon nanotube(SWCNT)s having a different chiral vector under axial compression were carried out based on molecular dynamics to investigate the effect of the helicity on the buckling behavior. Calculation was performed at room temperature for (8,8) armchair, (14,0) zigzag and (6,10) chiral single-wall carbon nanotubes. The Tersoff potential was used as the interatomic potential since it describes the C - C bonds in carbon nanotubes reliably. A conjugate gradient (CG) method was used to obtain the equilibrium configuration. Compressive force was applied at the top of a nanotube by moving the top-most atoms downward with the constant velocity of 10m/s. The buckling load, the critical strain, and the Young's modulus were calculated from the result of MD simulation. A zigzag carbon nanotube has the largest Young's modulus and buckling load, while a chiral carbon nonotube has the lowest values.
FABRICATION OF POLYMER MASTER FOR ANTIREFLECTIVE SURFACE USING HOT EMBOSSING AND AAO PROCESS
Authors: SHIN HONG GUE , KWON JONG TAE , SEO YOUNG HO , KIM BYEONG HEE
Published: March 2009

A simple method for the fabrication of polymer master for antireflective surface is presented. In conventional fabrication methods for antireflective surface, coating method with low refractive index have usually been used. However, it is required to have a high cost and a long processing time for mass production. In this paper, antireflective surface was fabricated by using hot embossing process with porous anodized aluminum oxide. Through multi-AAO and etching processes, nano patterned master with high aspect ratio was fabricated at the large area. Size and aspect ratio of nano patterned master are about 175 ± 25 nm and 2 ~ 3, respectively. In order to replicate nano patterned master, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master. Optical and rheological characteristics of antireflective surface were analyzed by using SEM, EDX and spectrometer inspection. Antireflective structure by replicating hot embossing process can be applied to various displays and automobile components.
TEXTURE AND FORMABILITY DEVELOPMENT OF ASYMMETRY ROLLED AA 3003 AL ALLOY SHEET
Authors: KIM INSOO , AKRAMOV SAIDMUROD , JEONG HAE BONG
Published: March 2009

The physical, mechanical properties and formability of sheet metal depend on preferred crystallographic orientations (texture). In this research work, we investigated texture development and formability of AA 3003 aluminum alloy sheets after asymmetry rolling and subsequent heat treatment. After asymmetry rolling, the specimens showed fine grain size. We also investigated the change of the plastic strain ratios after asymmetry rolling and subsequent heat-treating condition. The plastic strain ratios of asymmetrically rolled and subsequent heat treated samples are 1.5 times higher than the initial AA 3003 Al alloy sheets. These could be attributed to the formation of ND//<111> texture component through asymmetry rolling in Al sheet.
FINITE ELEMENT MODELLING OF MICRO-CUTTING PROCESSES FROM CRYSTAL PLASTICITY
Authors: CHEN Y. P. , LEE W. B. , TO S. , WANG H.
Published: March 2009

In ultra-precision machining (UPM), the depth of cut is within an extremely small fraction of the average grain size of the substrate materials to be cut. Polycrystalline materials commonly treated as homogeneous in conventional machining have to be considered as heterogeneous. The cutting force, one of the dominant factors influencing the integrity of the machined surface in UPM, is observed to strongly depend on the grain orientations. To accurately capture the intrinsic features and gain insight into the mechanisms of UPM of single crystals, the crystal plasticity constitutive model has been incorporated into the commercial FE software Marc by coding the user material subroutine Hypela2 available within it. The enhanced capability of the FE software will be adopted to simulate factors influencing the micro-cutting processes, such as grain orientation variation, the tool edge radius and the rake angle. The simulation results will provide useful information for the optimization of critical processing parameters and enhancement of quality of machined products.
ENERGY ABSORPTION OF EXPANSION TUBE CONSIDERING LOCAL BUCKLING CHARACTERISTICS
Authors: AHN KWANG-HYUN , KIM JIN-SUNG , HUH HOON
Published: March 2009

This paper deals with the crash energy absorption and the local buckling characteristics of the expansion tube during the tube expanding processes. In order to improve energy absorption capacity of expansion tubes, local buckling characteristics of an expansion tube must be considered. The local buckling load and the absorbed energy during the expanding process were calculated for various types of tubes and punch shapes with finite element analysis. The energy absorption capacity of the expansion tube is influenced by the tube and the punch shape. The material properties of tubes are also important parameter for energy absorption. During the expanding process, local buckling occurs in some cases, which causes significant decreasing the absorbed energy of the expansion tube. Therefore, it is important to predict the local buckling load accurately to improve the energy absorption capacity of the expansion tube. Local buckling takes place relatively easily at the large punch angle and expansion ratio. Local buckling load is also influenced by both the tube radius and the thickness. In prediction of the local buckling load, modified Plantema equation was used for strain hardening and strain rate hardening. The modified Plantema equation shows a good agreement with the numerical result.
CHARACTERIZATION OF ELECTRO-RHEOLOGCIAL FLUIDS UNDER HIGH SHEAR RATE IN PARALLEL DUCTS
Authors: ZHANG X. W. , ZHANG C. B. , YU T. X. , WEN W. J.
Published: March 2009

Electro-rheological (ER) fluid is a smart suspension which can be changed promptly from Newtonian to Bingham plastic material when subjected to a high-intensity electric field. This property of ER fluid makes it possible to be applied in adaptive energy absorbers. As the impact velocity encountered in applications could be very large, it is necessary to characterize the ERF under high shear rate. In this study, a capillary rheo-meter with parallel duct was designed and manufactured which is capable of producing a shear rate as high as 5000(1/s). Two giant ER fluids with mass concentration C = 51% and 44.5% and a commercial density-matched ER fluid with C = 37.5% were characterized. The experimental results show that when the ER fluids are free of electric field (E = 0 kV / mm ), they are Newtonian. However, for the former two ER fluids, the deposition effect is very remarkable and stirring has to be made continuously to keep the suspension stable. With the increase of the electric field intensity, the yield shear stresses of ER fluids increase exponentially but their viscosities do not change much. It is also found that within the parallel duct, the flow of ER fluids exhibits notable fluctuations, whose period increases with the increase of electric field intensity and is independent of the shear rate.
MECHANICAL PROPERTIES OF TITANIUM FOAM FOR BIOMEDICAL APPLICATIONS
Authors: KASHEF SADAF , LIN JIANGUO , HODGSON PETER D. , YAN WENYI
Published: March 2009

Understanding the mechanical behaviour of pure titanium ( Ti ) foam is crucial for the design and development of Ti foam-based load-bearing implants. In this work, pure titanium foam is fabricated by a powder metallurgical process using the space-holder technique with a spacer size of 500 to 800 µm. Experimental data from static compression testing on the Ti foam are presented. The application of theoretical formulae to predict Young's modulus and yield strength of titanium foams is also discussed. A foam with 63% porosity, 87 ± 5 MPa yield strength, and 6.5 ± 1.3 GPa Young's modulus is found to be appropriate for a number of dental and orthopaedic applications.