bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of two sonic handpieces during the preparation of simulated root canals
Authors: DUMMER P. M. H. , HUTCHINGS R. , HARTLES F. R. 
Published: September 2010

SummaryThe objective of this study was to assess and compare two sonic handpieces during the preparation of simulated root canals. A total of 60 simulated canals in clear resin blocks of various angles and positions of curvature were prepared using Shaper files activated either by an MM1500 Sonic Air or an MM1400 Mecasonic hand‐piece. Each handpiece was used to prepare 30 canals using an identical preparation procedure which involved a linear filing motion and an anticurvature technique in curved canals. The efficacy of the handpieces was determined for straight and curved canals separately and included an assessment of loss of canal length, weight loss from the blocks, smoothness of canal walls, transportation and overall shape of the prepared canals. Canals were prepared rapidly and effectively by both handpieces. Overall, the MM 1500 handpiece was associated with significantly less distance loss (P< 0.05) and significantly more loss of weight (P<0.01). Only four prepared canals (8%) had hour‐glass shapes displaying zips and elbows, each handpiece created two. Only two canals (4%) had danger zones, both were created by the MM1400 handpiece. There was little difference between the handpieces in terms of the smoothness of canal walls, the direction and amount of transportation or the overall shape of canals. Under the conditions of this study, the new MM1400 Mecasonic handpiece performed as well as the established MM 1500 Sonic Air.
An assessment of the plastic Thermafil obturation technique
Authors: SAUNDERS W. P. , SAUNDERS E. M. , GUTMANN J. L. , GUTMANN M. L 
Published: September 2010

SummaryThe effect of post space preparation on the apical seal of teeth roots treated with the plastic‐cored Thermafil was studied in vitro. Single rooted teeth with mature apices were prepared chemomechanically and obturated with alpha‐phase gutta‐percha, Thermafil, on plastic corecarriers and sealer, Sealapex. The teeth were divided randomly into four groups of 18 teeth each. In two of the groups post space was prepared by hand using a Parapost drill (diam. 1.25 mm) after gutta‐percha removal with Peeso reamers in a slow‐speed handpiece, one group immediately after canal obturation and the other after storage in 100% relative humidity at 37°C for 1 week; 5 mm of root filling was left intact. The time taken to remove the gutta‐percha was recorded. Post space was not prepared in the control groups. Apical leakage was determined using black India ink. The teeth were demineralized, rendered transparent, and linear measurement of dye penetration was recorded. Results showed that there were no significant differences in leakage between any of the groups (P> 0.05). There was no statistically significant difference in the time required to remove the gutta‐percha from the root canals in both groups (P<0.05). It is concluded that under the conditions of this study post space preparation immediately after obturation, or after a delay of 1 week, does not affect the apical seal of Thermafil with plastic corecarriers.
Effects of nutrient enrichment on predator–prey metapopulation dynamics
Authors: Holyoak Marcel 
Published: September 2010

Summary 1. In certain predator–prey models, enrichment of nutrients produces large amplitude population oscillations that can cause extinctions; this effect has been termed the ‘paradox of enrichment’. Metapopulation models also show that despite enrichment reducing the stability of equilibria in local populations, spatially subdivided populations may show bounded fluctuations because of asynchronous local density fluctuations. 2. Effects of enrichment and subdivided habitat structure were tested using two protozoans, predatory Didinium nasutum Müller and its bacterivorous prey, Colpidium striatum Stokes. A replicated experiment compared predator–prey dynamics in low, medium and high nutrient microcosms. Microcosms consisted of subdivided arrays of nine interconnected 30 mL bottles, undivided bottles of the same total volume (270 mL) and isolated 30 mL bottles. 3. Consistent with the paradox of enrichment, isolated populations produced greater mean predator densities at high nutrient concentrations than low or medium concentrations. The proportion of replicates in which predators drove prey extinct was also greater with high than with low or medium nutrient concentrations. 4. Enrichment increased prey density in all microcosm types. This is consistent with published predator–prey models where dynamics are mathematically unstable. 5. Predators and prey persisted longer in all subdivided microcosms than in undivided bottles. However, there were some unexpected changes in spatial dynamics with enrichment. For prey, direct or indirect effects of enrichment raised numbers dispersing, spatial synchrony of density fluctuations and variability in the number of patches occupied. 6. For predators in arrays, enrichment reduced the starvation rate, total numbers dispersing, and spatial synchrony. Time until recolonization of individual patches by predators was also longer in enriched microcosms, suggesting a possible decrease in the likelihood of regional persistence. A published simulation model produced qualitatively similar changes in dynamics with changes in prey and predator dispersal rate. 7. This study shows that spatial dynamics can potentially explain persistence of subdivided populations for long periods despite nutrient enrichment. However, the complex influence of enrichment on spatial dynamics illustrates the need to study more natural populations.
Geographic distance and the role of island area and habitat diversity in the species–area relationships of four Lesser Antillean faunal groups: a complementary note to Ricklefs & Lovette
Authors: Morand Serge 
Published: September 2010

Summary1. Recently,Ricklefs & Lovette (1999)have emphasized the possible confounding effect of habitat diversity on area while studying species–area relationships. They illustrated this problem using four groups of organisms (birds, bats, herptiles, and butterflies) on 19 islands of the Lesser Antilles. Although they referred to the potential for species to migrate between islands, they did not take into account the geographical distances between islands.2. Here, I reanalyse their data using a multivariate method, based on permutation of distance matrices, which incorporates pairwise geographical distances between islands. The analysis includes as independent variables the geographical distances between pairs of islands, size, maximum elevation, and habitat diversity of each island. The last three variables were obtained fromRicklefs & Lovette (1999).3. Results of the analysis were similar to those ofRicklefs & Lovette (1999). In addition, however, geographical distances influenced species richness of bats, birds and butterflies.4. These new results are helpful for investigating the processes that may contribute to the observed pattern of species richness. The level of endemism of the four taxonomic groups is related to the influences of geographical distances among islands, and might be explained by differences in their vagility.5. Finally, I emphasize the need to incorporate geographical distances among islands, using statistical methods that can manipulate distance matrices.
Silver spoons and snake body sizes: prey availability early in life influences long‐term growth rates of free‐ranging pythons
Authors: Madsen Thomas , Shine Richard 
Published: September 2010

Summary 1. A 13‐year study of free‐ranging water pythons (Liasis fuscus) and their main prey (dusky rats, Rattus colletti) in tropical Australia provided extensive data on the relationship between python growth rates and prey availability. 2. Python growth rates exhibited considerable variation among individuals. Growth rates of siblings were not correlated, suggesting that environmental rather than genetic factors cause this wide variation. 3. The availability of prey varied considerably among years, due to annual variation in rainfall patterns. Pythons grew more rapidly in years with high rat abundance than in years when rats were scarce. Also, python cohorts that hatched in years when prey were abundant exhibited faster growth rates than those that hatched when prey were scarce. 4. The snakes showed strong ontogenetic consistency in relative growth rates: that is, an individual with faster‐than‐average growth in its first year of life continued to grow rapidly throughout the study period. Thus, these pythons displayed a strong ‘silver spoon’ effect, whereby favourable conditions (high prey abundance) in the first year of life exerted a long‐term effect on growth trajectories and thus, adult body sizes. This effect was strongest in the faster‐growing sex (females). 5. Hence, the current body size composition of the python population reflects stochastic rainfall‐induced annual variation in prey availability over the preceding decades.
Factors affecting first‐year survival in grey seals and their implications for life history strategy
Authors: Ailsa J. Hall , Bernie J. McConnell , Richard J. Barker 
Published: September 2010

Abstract

In order to estimate the effect of weaning mass and body condition on the post‐weaning survival of grey seal pups from the Isle of May, Scotland in 1998 during their first year of life, a simultaneous analysis of live resighting and dead recovery mark–recapture data was used. A new type of tag was employed which allowed individuals to be identified when resighted alive (Hall, Moss & McConnell 2000) as well as when found dead.
The probability of post‐weaning survival to age 1 increased with body condition at weaning and differed between the sexes. Regardless of pup condition and time of year, the odds of survival for female pups over a 2‐month interval was estimated to be 3·37 (SE = 1·30) times higher than for males. Regardless of sex, a 1 standard deviation increase in pup condition was estimated to increase the odds of survival by a factor of 1·422 (SE = 0·226). For a male pup in average condition (0·41 kg cm−1) the estimated annual survival after adjusting for tag‐loss was 0·193 (SE = 0·084); for a female pup in average condition (0·39 kg cm−1) it was 0·617 (SE = 0·155).
The effect of condition at weaning on survival was significantly greater for male pups than for females. This implies that high quality females should invest more heavily in their male pups because the marginal return, in terms of increased reproductive value, from any additional expenditure is twice that for females. Male pups in our sample were significantly heavier at weaning and in better condition than female pups. However, this does not provide conclusive support for our predictions, because we could not control for the effects of maternal size on weaned mass.
Climate change and breeding success: decline of the capercaillie in Scotland
Authors: Moss Robert , Oswald James , Baines David 
Published: September 2010

Abstract

The number of capercaillie in Scotland has fallen since the 1970s. Previous work showed that low breeding success, exacerbated by deaths of fully grown birds flying into forest fences, was the primary cause of the decline. The hypothesis that climate change caused the lower breeding success was investigated in this study.
Temperature usually rose during April. There was no trend in mean April temperature during the study (1975–99) but there was a progressive cooling in mid‐April relative to the rest of the month, such that the normal April warming was increasingly delayed.
Hens reared more chicks when the temperature rose more in early April. It is suggested that this stimulated timely plant growth, so improving the laying hens’ plane of nutrition and the viability of their chicks.
Hens also reared more chicks when late May was warmer and early June was warmer and had fewer rain days. Young chicks may have foraged more successfully in warm dry conditions. However, neither temperature nor rain days in late May or early June showed any trend during the study.
Increasingly protracted spring warming seems to have been a major cause of the decline of the capercaillie in Scotland.
Ungulate foraging strategies: energy maximizing or time minimizing?
Authors: Bergman Carita M. , Fryxell John M. , Gates C. Cormack , Fortin Daniel 
Published: September 2010

Summary

Many classical models of ungulate foraging are premised on energy maximization, yet limited empirical evidence and untested currency assumptions make the choice of currency a non‐trivial issue. The primary constraints on forage intake of ungulates are forage quality and availability. Using a model that incorporates these two constraints, we predicted the optimal biomass of forage patches for ungulate grazers using an energy maximizing vs. a time minimizing strategy.
We tested these predictions on wood bison (Bison bison athabascae Rhoads) grazing naturally occurring sedge (Carex atherodes Spreng). The digestive constraint was determined by a series of ad libitum feeding trials using sedge at different stages of growth. Sedge digestibility declined with biomass. Ad libitum intake of sedge by bison declined with sedge digestibility and thus decreased with sedge biomass. On the other hand, short‐term sedge intake rates of wood bison increased with biomass.
Incorporation of these constraints resulted in the prediction that daily energy gain of bison should be maximized by grazing patches with a biomass of 10 g m−2, whereas a bison could minimize daily foraging time needed to fulfil its energy requirement by cropping patches with a biomass of 279 g m−2.
To test these quantitative predictions, we used a staggered mowing regime to convert even‐aged stands of sedge to a mosaic of patches varying in quality and quantity. Observations of bison grazing these mosaics indicated that patches of biomass below 120 g m−2 were avoided, while patches of biomass 156 and 219 g m−2 were highly preferred, with the greatest preference for the latter.
These results indicate that bison were behaving as time minimizers rather than energy maximizers. Daily cropping times of free‐ranging bison from the literature corroborate our results.
A high harvest rate induces a tendency to generation cycling in a freshwater fish population
Authors: HUUSKO ARI , HYVÄRINEN PEKKA 
Published: September 2010

Summary

The dynamics of exploited populations are clearly affected by two major processes, recruitment and harvesting. The large variation in recruitment is caused mainly by the variation of the brood stock size, which links at least partly to harvesting and consequently is under anthropogenic control. Therefore, harvesting has the potential to modulate the dynamics of exploited populations in many ways.
Demonstrated by a pelagic planktivore fish, vendace Coregonus albula L., using population dynamics in Lake Oulujärvi, northern Finland, this study shows that the changes in harvesting induced a tendency to generation cycling in the dynamics of a freshwater fish population.
The relatively long‐term oscillation in recruitment and stock dynamics of the vendace population transformed into clear 2‐year cycling in recruitment and also into the same tendency in the spawning stock, both induced by the increase of the harvest rate to a high and stable level. The high harvest rate evidently simplified the spawning population structure from a multigeneration state to an almost totally single‐generation state, followed by generation cycling in the population dynamics.
The results demonstrated clearly that harvesting can work as forcing agent and actually dictate the population fluctuations. It is very important to be aware of how natural variations in population abundance interplay with harvesting and also with other human actions. All these support a precautionary policy in harvesting and stress the importance of understanding the basic mechanisms of population dynamics in order to gain sustained yields from the population in space and time.
Planning for success: Serengeti lions seek prey accessibility rather than abundance
Authors: HOPCRAFT J. GRANT C. , SINCLAIR A. R. E. , PACKER CRAIG 
Published: September 2010

Summary

We used long‐term radio‐telemetry data to investigate how Serengeti lions (Panthera leo) distribute themselves with respect to hunting opportunities. Specifically, we investigate whether lions hunt in areas where prey are easy to capture or where prey are locally abundant.
We used resource‐selection functions (logistic regressions) to measure the location of kills/carcasses with respect to five different habitats: the view‐sheds from large rocky outcrops, river confluences, woodland vegetation, erosion embankments and water sources.
As expected for a sit‐and‐wait predator, resting lions spent more time in areas with good cover. On a broad‐scale, lions shifted their ranges according to the seasonal movement of prey, but at a finer scale (< 100 m) lions fed in areas with high prey ‘catchability’ rather than high prey density. Plains lions selected erosion embankments, view‐sheds from rocky outcrops, and access to free water. Woodland lions tended to use erosion embankments, and woody vegetation.
The results emphasize the importance of fine‐scale landscape and habitat features when assessing predator–prey theory and conservation.
Does interspecific competition from congeners cause the scarcity of Gerbillus henleyi in productive sandy desert habitats?
Authors: ABRAMSKY Z. , ROSENZWEIG M. L. , ELBAZ M. , ZIV Y. 
Published: September 2010

Summary

We tested the hypothesis that Gerbillus henleyi (de Winton 1903), the smallest species (10 g) of a pssamophilic guild in Israel, is scarce on relatively productive dunes of the Israeli desert, due to negative interactions from the common G. allenbyi (Thomas 1918) and G. pyramidum (Geoffroy 1825).
The alternative hypothesis was that scarcity on sand resulted from the size of its naked hind feet, that do not allow efficient locomotion on sand.
Despite their naked soles the weight‐bearing surface of G. henleyi feet carry less mass/area than those of any other species.
We measured interaction coefficients with the two common species using field‐manipulation experiments in two enclosures.
Habitat usage of G. henleyi changed from significantly preferring the stabilized sand, when alone, to significantly using the semistabilized dune, when G. allenbyi was also present.
We also estimated the interaction coefficients and calculated the G. henleyi's isoclines competing with the two common gerbil species using a technique we developed elsewhere.
The stability analysis of the isoclines of G. henleyi competing with either G. allenbyi or with G. pyramidum suggests that stable coexistence occurs when G. henleyi is relatively scarce while the competitors are common.
Interspecific competition from either G. allenbyi or G. pyramidum accounts for 90·3% reduction in G. henleyi density, relative to when it is alone.
We concluded that the negative interactions from congeners was the major cause for the scarcity of G. henleyi on the relatively rich sand dunes of the Israeli desert.
Rhythmicity of sex pheromone content in female Heliothis virescens: impact of mating
Authors: MBATA GEORGE N. , RAMASWAMY SONNY B. 
Published: September 2010

Abstract Pheromone production in virgin females of Heliothis virescens (F.) (Lepidoptera: Noctuidae) peaked between the fourth and seventh hours of scotophase on the second, third, fourth and fifth days following eclosion. The highest peak (186 ng) occurred on day 3 after eclosion. Z‐11‐Hexadecenal comprised the highest proportion of seven components in the pheromone glands. Disproportionately higher amounts of hexadecanal and Z‐11‐hexadecenol occurred during photo‐phase and other periods when low quantities of total pheromone were recorded.Mating suppressed pheromone production which remained low until 48 h after mating. Coupling females with males mated three times previously or with 6‐day‐old males was less effective in causing a drop in pheromone content which peaked again 24 h after mating. This suggests the transfer of a male factor, a pheromonostatic factor, that suppresses pheromone production in mated females and that the factor from older and previously mated males is less effective.
Effects of sublethal dose of chlorfluazuron on testicular development and spermatogenesis in the common cutworm, Spodoptera litura
Authors: Perveen Farzana 
Published: September 2010

SummaryThis paper describes the physiological mechanism of action of chlorfluazuron on testicular development and spermatogenesis when sublethal doses (LD10: 1.00 ng/larva or LD30: 3.75 ng/larva) are applied topically to the cuticle of newly moulted fifth instars of the common cutworm Spodoptera litura (F.) (Lepidoptera, Noctuidae). These doses disrupt the growth and development of testes by decreasing the volume and weight of testes and thickness of testes sheath as compared with that of the controls. Sublethal doses of chlorfluazuron also significantly reduce the protein content of the testis, but do not affect the carbohydrate and lipid contents in newly emerged treated males when measured in μg/mg of testis as compared with that of the controls. Additionally, such doses disrupt spermatogenesis by reducing the number and size of eupyrene and apyrene sperm bundles in the testis. Very few or no eupyrene sperm bundles are observed in vas deferens of pre‐ and newly moulted adults compared with controls. This result shows that the transfer of sperm bundles from testes to vas deferens is delayed in treated males. The effects of chlorfluazuron on testicular development and spermatogenesis is thought to be one of the factors responsible for the reduction in fecundity, fertility and hatchability caused by sublethal doses of chlorfluazuron.
Locust flight initiation: a comparison of normal and artificial release
Authors: Kutsch W. , Fuchs U. 
Published: September 2010

SummaryFlight initiation was analysed in the migratory locust,Locusta migratoriaL. using conventional and high‐speed video systems. Flight was initiated by three methods: normal jump, free fall and controlled catapult.Parameters evaluated were time from release to wing‐opening, body angle, speed, height gain, wing‐opening, initial wing‐beat frequency. Fastest wing‐opening occurred following a normal jump. A catapult device allowed manipulation of the launching parameters: speed and angles at launching. It appeared that in an artificially catapulted start there was a minimum speed (v > 0.75 m/s) required to initiate flight. However, under free‐fall conditions a mean speed of v = 0.6 m/s at wing‐opening was observed. When the different parameters of the controlled catapult start were equal to those for normal jump then the time to wing‐opening was found to be extended for the catapult launch. However, other parameters were not affected, occasionally even a ‘kick in air’ was observed. The catapult launches indicated that within about three wing‐beat cycles the animals showed active flight, with positive lift and constant or increasing speed, compared to a ballistic trajectory. Our results indicate that a controlled catapult device will prove useful to the study of sensory and central processes underlying free flight initiation.