bluuebunny/crossref_metadata_2025 huggingface dataset:
Alumina Thin Films as Optical Waveguides
Authors: Stadler Bethanie J. H. , Oliveria Manuel , Bouthillette Lionel O.
Published: April 2005

Amorphous AI2O3, fabricated by reactive rf magnetron sputtering, has been evaluated as a planar waveguide material. The microstructure and optical properties of planar waveguides were examined as a function of deposition (substrate temperature, O2 flow rate) and annealing conditions. X‐ray and electron diffraction verified that as‐deposited films were amorphous for substrate temperatures up to 500°C and for a wide range of O2 flow rates. This amorphous phase was stable through anneals up to 800°C, but crystallized to “y‐Al2O3 at 1000°C and to α‐Al2O3 at 1200°C. The amorphous films had transmission windows that extended from 200 nm to 7 (Am with an average refractive index of 1.65 and reproducible losses as low as ∼1 dB/cm at 632.8 nm. The refractive index increased with substrate temperature, but was independent of O2 flow rate. The losses decreased with substrate temperature and increased as a function of O2 flow rate. As a final check on the amorphous structure, Cr‐doped films were prepared by codeposition. Fluoresence was detected only in annealed crystalline films.
Effect of Fiber Volume Fraction on the Off‐Crack‐Plane Fracture Energy in Strain ‐Hardening Engineered Cementitious Composites
Authors: Maalej Mohamed , Hashida Toshiyuki , Li Victor C.
Published: April 2005

In this paper, the results of an experimental study on the effect of fiber volume fraction on the off‐crack‐plane fracture energy in a strain‐hardening engineered cementitious composite (ECC) are presented. Unlike the well‐known quasi‐brittle behavior of fiber reinforced concrete, ECC exhibits quasi‐ductile response by developing a large damage zone prior to fracture localization. In the damage zone, the material is microcracked but continues to strain‐harden locally. The areal dimension of the damage zone has been observed to be on the order of 1000 cm2 in double cantilever beam specimens. The energy absorption of the off‐crack‐plane inelastic deformation process has been measured to be more than 50% of the total fracture energy of up to 34 kJ/m2. This magnitude of fracture energy is the highest ever reported for a fiber cementitious composite.
Crystallization of Zirconia under Hydrothermal Conditions
Authors: Bućko Mirosław M. , Haberko Krzysztof , Faryna Marek
Published: April 2005

Amorphous zirconia gel was hydrothermally treated at 250°C for 1–326 h in water and in NaOH water solution. Changes of the crystallite sizes and shapes were observed using TEM. The nature of these changes seems to be independent of the crystallization environment, but the rate of the process is much faster in the NaOH solution. The mechanism of the crystal growth is suggested.
Mullite Formation by Endothermic Reaction of α‐Alumina/Silica Microcomposite Particles
Authors: Wang Keyun , Sacks Michael D.
Published: April 2005

The formation of mullite was investigated using microcomposite powders which consist of α‐alumina cores and amorphous silica coatings. Differential thermal analysis and X‐ray diffraction showed that the mullitization reaction was endothermic. In contrast, mullite forms exothermically in samples prepared by sol‐gel processing. The results are shown to be consistent with available thermodynamic data for mullite formation from different alumina and silica phases.
Microstructures and Dielectric Properties of Ferroelectric Glass‐Ceramics
Authors: Reece Michael J. , Worrell Clive A. , Hill Graham J. , Morrell Roger
Published: April 2005

The microstructures of ferroelectric glass‐ceramics derived from (Pb,Sr,Ba)Nb2O6 solid solutions have been investigated systematically using electron microscopy (TEM, SEM) and X‐ray diffraction (XRD). These data, together with the measured dielectric properties of the materials, have been correlated with both the sintering/devitrification conditions and compositional changes to the base glass. The low incidence of ferroelectric domains suggests that an increase in permittivity results from an increase in internal stress during grain growth. These domains were observed only in a few tetragonal structured crystals with grain sizes >1 μm. Their compositions were typically Sr‐rich and Ba‐depleted. For a given devitrification/crystallization temperature, the grain compositions and sizes are affected significantly by relatively minor compositional changes to the base glass network formers. The diffuse temperature dependence of permittivity is attributed to the fine‐grain (submicrometer) microstrucutres and the compositional range of solid solutions which arise during devitrification.
High‐Temperature Fracture Toughness of Duplex Microstructures
Authors: French Jonathan D. , Chan Helen M. , Harmer Martin P. , Miller Gary A.
Published: April 2005

The temperature dependence of the fracture toughness of ceramics exhibiting duplex microstructures was studied relative to their single‐phase constituents using two test methods: bend testing of chevron‐notched beams, and the indentation‐crack‐length technique. The two materials systems studied were Al2O3:c‐ZrO2(Y) and A12O3:Y3A1SO12 (YAG), and the testing temperature ranged from room temperature to 1200°C. The study showed that in both systems the duplex materials showed higher toughness values than their single‐phase constituents above 800°C. This result was attributed to the contribution of low‐energy interphase boundaries to the overall composite toughness. Indentation crack length measurements gave toughness values and trends comparable to those determined by the chevronnotched beam method. By comparing the results of the two test methods it was possible to demonstrate that the indentation calibration constant (ξ) shows no significant temperature or material dependence. For the zirconia‐containing materials, however, indentation at elevated temperatures is accompanied by significant localized plasticity, which suppressed the radial cracking. Under such conditions, some caution is warranted, since localized plasticity can lead to an overestimation of the fracture toughness.
Toughening of Layered Ceramic Composites with Residual Surface Compression
Authors: Lakshminarayanan R. , Shetty D. K. , Cutler Raymond A.
Published: April 2005

Effects of macroscopic residual stresses on fracture toughness of multilayered ceramic laminates were studied analytically and experimentally. Stress intensities for edge cracks in three‐layer, single‐edge‐notch‐bend (SENB) specimens with stepwise varying residual stresses in the absence of the crack and superimposed bending were calculated as a function of the crack length by the method of weight function. The selected weight function and the method of calculation were validated by calculating stress intensities for edge cracks in SENB specimens without the residual stresses and obtaining agreement with the stress‐intensity equation recommended in ASTM Standard E‐399. The stress‐intensity calculations for the three‐layer laminates with the macroscopic residual stresses were used to define an apparent fracture toughness. The theoretical predictions of the apparent fracture toughness were verified by experiments on three‐layer SENB specimens of polycrystalline alumina with 15 vol% of unstabilized zirconia dispersed in the outer layers and 15 vol% of fully stabilized zirconia dispersed in the inner layer. A residual compression of ∼400 MPa developed in the outer layers by the constrained transformation of the unstabilized zirconia from the tetragonal to the monoclinic phase enhanced the apparent fracture toughness to values of 30 MPa.m1/2 in a system where the intrinsic fracture toughness was only 5 to 7 MPa.m1/2.
Spontaneous Infiltration of Alumina by Copper‐Oxygen Alloys
Authors: Gonzalez Eduardo J. , Trumble Kevin P.
Published: April 2005

Infiltration of alumina powder compacts by molten copper‐oxygen alloys under controlled oxygen partial pressures has been studied. Spontaneous infiltration occurred for copper alloys containing more than approximately 5 at.% oxygen. Despite supersaturation of the copper with oxygen, no Cu2O or interfacial reaction layers of CuAlO2 were resolved by TEM, suggesting the critical wettability for infiltration is not determined by interfacial chemical reaction. CuAlO2 did form, but as discrete inclusions up to 0.5 mm in diameter. Infiltration and microstructure development are discussed in terms of the observed wetting behavior and available data on interfacial oxygen adsorption.
Wear Properties of Alumina/Aluminum Composites with Interpenetrating Networks
Authors: Sternitzke Martin , Knechtel Mathias , Hoffman Mark , Broszeit Erhard , Rödel Jürgen
Published: April 2005

The tribological behavior of an A12O3/AI composite against a steel and an alumina was investigated in pin‐on‐disk wear tests using unlubricated conditions in air. Various composite compositions of aluminum contents ranging from 0 to 28 vol% were investigated over a variety of contact loads and sliding speeds. Wear rate and friction force were continuously monitored during testing. Following completion of the test, pin weight loss and the profile of the wear tracks were determined. Scanning electron microscopy accompanied by EDAX analysis was used to investigate the worn surfaces and the wear debris. The wear behavior of the composites with a low metal content (<15%) during sliding against steel and alumina was found to be comparable to the wear of pure alumina. Wear occurred either on the steel or apparently simultaneously on the pin and alumina disk. With higher Al contents, wear shifts to the composite, the wear rate increases abruptly and is accompanied by fracture of the A12O3 matrix. Wear appears to occur in the composite when the mechanical strain in the composite, near the contact surface, as a result of frictional loads, exceeds the fracture strain of the alumina matrix.
Effects of Silver and Palladium Doping on the Dielectric Properties of 0.9Pb(Mg1/3Nb2/3)O3–0.1 PbTiO3 Ceramic
Authors: Sato Yuichi , Kanai Hideyuki , Yamashita Yohachi
Published: April 2005

The doping of silver and palladium into a 0.9Pb‐(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN–PT) ceramic has been investigated. It was found that Ag could be incorporated into the PMN–PT lattice, though this was almost impossible with Pd. Doping at up to 0.2 mol% of Ag and Pd reduced the maximum dielectric constant (Kmax) from 21000 to 14000 without any conspicuous change in physical properties. Order–disorder transitions in the perovskite structure contributed to the decrease in Kmax, since the diffuseness parameter, δ, which represents the degree of the order‐disorder relationship, increased with Ag doping. However, addition of more than 0.2 mol% increased Kmax. Increases in grain size and in the perovskite ratio contributed to this increase. The dielectric properties of Ag/Pd‐doped samples were intermediate between the Ag‐ and Pd‐doped samples.
Synthesis of Titania Composite Membranes by the Pressurized Sol‐Gel Technique
Authors: Hyun Sang H. , Kang Beoni S.
Published: April 2005

Crack‐free titania composite membranes have been synthesized from colloidal titania sols (average particle size of 7–16 nm) by the pressurized sol‐gel coating technique. The Knudsen permeability of N2 through the titania membrane layer heat‐treated at 300°C is about 21 × 10‐7–35 × 10‐7 mol/m2·s·Pa at room temperature. The permselectivity and the separation factor of He to O2 in the temperature range of 25°‐245°C are 2.49–2.74 and 1.66–1.84, respectively. The average pore diameters of these membranes estimated from the molecular weight cutoff data (6000–9000) using poly(ethylene glycol) are 3.0–4.0 nm. By doping zirconia into titania membranes, their thermal stability could be improved up to 800°C.
The effect of vertical migration strategy on retention and dispersion in the Irish Sea during spring–summer
Authors: EMSLEY S. M. , TARLING G. A. , BURROWS M. T.
Published: April 2005

A biophysical model of the Irish Sea was produced to predict net horizontal movement of key taxa including small copepods (Acartia, Pseudocalanus), large copepod species (Calanus finmarchicus and C. helgolandicus), the euphausiid Meganyctiphanes norvegica, and the larval stages of commercially important fish and Nephrops. The model coupled biological information on the vertical distribution and diel vertical migration (DVM) of these taxa with temporally resolved flow fields generated by a baroclinic hydrodynamic model. The DVM of Calanus spp. and Meganyctiphanes was parameterized empirically from data provided by a biophysical campaign carried out in the nearby Clyde Sea. Small copepods and larvae remained within the layers above the thermocline. Model organisms, programmed with particular behavioural patterns, were spaced at regular intervals (1/20° longitude × 1/30° latitude) in the model grid, which extended from 53 to 54.5°N and 4.5 to 6.4°W. The model was run over the months of April, May and June. Model simulations showed that the movement of model organisms followed one of four characteristic patterns: containment along the coast, advection to the north or south, stagnation in the centre of the gyre or circulation around the periphery of the gyre. The latter pattern was apparent even in April, when gyral circulation was not expected because of a lack of stratification in the water column. Thirty‐day model runs in April, May and June showed that the number of organisms retained within the model grid varied between 23 and 49%. Those seeded close to the Irish coast had the highest probability of being retained within the model grid at the end of 90 days. DVM increased the probability of retention through improving the chances of organisms becoming entrained within the gyre circulation. This was especially true for Calanus spp., with those performing midnight sinking being the most likely to be retained out of any model organism. Meganyctiphanes showed comparatively lower levels of retention in deep regions, which suggests that they may have to swim against currents during certain phases of their DVM to avoid displacement. Overall, model results supported a number of hypotheses on the origin and fate of various taxa in the Irish Sea, as well as revealing some less expected distribution patterns.
Key factors influencing transport of white shrimp (Litopenaeus setiferus) post‐larvae into the Ossabaw Sound system, Georgia, USA
Authors: WENNER E. L. , KNOTT D. M. , BARANS C. A. , WILDE S. , BLANTON J. O. , AMFT J.
Published: April 2005

We examined conditions under which white shrimp (Litopenaeus setiferus) post‐larvae enter an estuarine channel receiving high freshwater discharge and one receiving negligible discharge in the Ossabaw Sound system of Georgia, USA, during 1997 and 1998. We used surface nets to collect plankton over several 14‐day periods, during which consecutive tows were made at night against the flooding current at stations in the inlet channels. During these sampling periods, additional intensive periods of around‐the‐clock surface and near‐bottom (using a bottom sled) plankton tows were made. Data on oceanographic conditions were obtained from moored instrument arrays and shipboard sampling. We identified three key factors that influenced the densities of post‐larval white shrimp in time and space within the Ossabaw inlet system. The first factor was a critical minimum temperature of coastal waters of 27–28°C. Once the threshold temperature was reached, lunar tidal stage became a key factor when the full duration of the flood tide coincided with darkness during peak ingress. This peak also coincided with an increase in water level within the system by more than 0.2 m, which induced an additional influx of water that reinforces the flood current over the ingress period. Our results suggest that the direction of subtidal currents (into or out of the system) becomes a significant factor in post‐larval ingress when influx of water coincides with the time of favorable temperature conditions and nighttime flood tides.
Trends in NE Atlantic landings (southern Portugal): identifying the relative importance of fisheries and environmental variables
Authors: ERZINI KARIM
Published: April 2005

Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to identify trends and explore the relationships between the response variables (annual landings of 12 species) and explanatory variables [sea surface temperature, rainfall, an upwelling index, Guadiana river (south‐east Portugal) flow, the North Atlantic oscillation, the number of licensed fishing vessels and the number of commercial fishermen]. Landings were more highly correlated with non‐lagged environmental variables and in particular with Guadiana river flow. Both techniques gave coherent results, with the most important trend being a steady decline over time. A DFA model with two explanatory variables (Guadiana river flow and number of fishermen) and three common trends (smoothing functions over time) gave good fits to 10 of the 12 species. Results of other models indicated that river flow is the more important explanatory variable in this model. Changes in the mean flow and discharge regime of the Guadiana river resulting from the construction of the Alqueva dam, completed in 2002, are therefore likely to have a significant and deleterious impact on Algarve fisheries landings.
Effects of stream restoration on ecosystem functioning: detritus retentiveness and decomposition
Authors: LEPORI F. , PALM D. , MALMQVIST B.
Published: April 2005

Increasing degradation of ecological conditions in streams because of human activities has prompted widespread restoration attempts; however, the ecological consequences of restoration remain poorly understood. We explored the effects of restoration through placement of boulders into the channel in the Ume River catchment in northern Sweden, where tributary streams were extensively channelized to facilitate the transport of timber in the 19th and early 20th centuries. Retentiveness and breakdown of coarse particulate organic matter (CPOM), two key ecological functions in low‐order streams most likely to be affected by channelization, were compared between restored, channelized and unimpacted reference stream sites.

Artificial leaves were used to assess short‐term CPOM retentiveness, while CPOM breakdown was estimated as the mass loss of alder (Alnus spp.) leaf packs placed in coarse mesh litter bags. Also, the taxonomic richness, abundance, biomass and evenness of the leaf‐eating invertebrates (shredders) on the retrieved leaf material were quantified. Detailed field measurements were carried out to identify geomorphological and hydraulic controls of CPOM retentiveness and breakdown at the study sites.

CPOM retentiveness reflected most strongly the density of boulders and submerged woody debris at the study sites. Restored sites were on average twice as retentive as channelized sites and significantly more retentive than reference sites when discharge was controlled.

Current velocity at bank‐full flow was the single most important predictor of CPOM mass loss, implying that mechanical fragmentation was substantial during high flows; other apparent controls of CPOM breakdown included water temperature and shredder abundance. CPOM mass loss was similar between restored and reference sites. However, breakdown was slightly faster at most channelized sites, consistent with higher hydraulic stress during high flow conditions. The shredder assemblages that colonized the litter bags were similar in richness, abundance, biomass and evenness between treatments.

Synthesis and applications. In channelized forest streams, low retentiveness and fast mechanical fragmentation during high flows contribute to the rapid depletion of benthic CPOM following leaf abscission in autumn, thereby weakening the heterotrophic energy pathways that probably support much of the biological production in these systems. Our results illustrate that restoration by replacement of boulders can successfully reverse these impacts of channelization and thus contribute to the efficient ecological functioning of impacted streams.
Succession of aquatic vegetation driven by reduced water‐level fluctuations in floodplain lakes
Authors: VAN GEEST G. J. , COOPS H. , ROIJACKERS R. M. M. , BUIJSE A. D. , SCHEFFER M.
Published: April 2005

In recent years, interest has grown in restoring floodplain function of regulated rivers. Successful rehabilitation of riparian systems requires knowledge of how regulation of river flow affects biodiversity and ecosystem function. The effects of changes in the river's low water‐level regime on aquatic ecosystems in floodplains has received little attention so far.

The aquatic vegetation of 215 floodplain lakes along the Lower Rhine (the Netherlands) was analysed in relation to lake characteristics and lake water‐level fluctuations in 1999–2000.

Vegetation composition was related to lake morphology and age, cattle access to the shoreline, the amount of time the river was in flood, and lake sediment area exposed at low water level (drawdown). Surprisingly, vegetation composition was correlated more strongly with lake age and occurrence of drawdown than the amount of time the river was in flood.

In older lakes, water‐level fluctuations are reduced due to an accumulation of clay and silt that ‘seals’ sediment, preventing drawdown during periods of low river levels. Our results suggest that this clay sealing process is a major driving force for aquatic vegetation succession in floodplain lakes along the Lower Rhine, as succession drives from desiccation‐tolerant species (e.g. Chara spp.) in young lakes to desiccation‐sensitive species (e.g. Nuphar lutea) in old lakes.

Water levels were stable in lakes along a river branch that was impounded below mean flow only. Here, the original low water‐level regime has been replaced by an artificial regime with higher water levels than would be expected naturally. Consequently, in these lakes drawdown was rare or absent, and the aquatic macrophyte vegetation was characterized by low species richness and frequent dominance by the invasive species Elodea nuttallii.

Synthesis and applications. Our results show that stabilization of river water levels during low flow may negatively affect vegetation composition and succession in floodplain lakes adjacent to these rivers. A management scheme including incidental temporary lowering of the river water level, which results in drawdown of floodplain lakes, would enhance the ecological status of those rivers with stabilized water levels during low flow.
Population dynamics of brushtail possums subject to fertility control
Authors: RAMSEY DAVE
Published: April 2005

Reducing the fertility of pest species using immunocontraceptive vaccines holds promise for the humane and effective control of vertebrate pest populations. However, despite much research into the development of contraceptive vaccines, there are few data illustrating the effectiveness of fertility control for managing wild populations of vertebrate pests.

In New Zealand, introduced brushtail possums Trichosurus vulpecula have been the focus for the development of contraceptive vaccines to provide a possible alternative to lethal control techniques.

The effect of fertility control on the population dynamics of brushtail possums was investigated experimentally using surgical sterilization to suppress breeding on six 12‐ha study sites between January 1996 and October 2000. Sterilization treatments, consisting of 0%, 50% and 80% of resident females sterilized, were applied at a particular site, with adjustments made annually on recruits to maintain levels of sterility. Mark–recapture trapping was used to estimate age‐specific demographic rates and their relative contribution to age‐specific population growth rates (λ).

Sterility treatments resulted in reductions to per capita rates of local recruitment (surviving young per adult female) of 60% and 74% on average for 50% and 80% levels of sterility, respectively. However, immigration by yearling‐aged possums compensated for reductions in local recruitment because of sterility treatments, leading to the stable (λ = 1) population trajectories on sterility treatment sites.

There was some evidence that sterilized females had higher annual survival rates than fertile females, but otherwise there was no evidence of any other compensatory responses to imposed sterility. However, additional studies are needed to clarify possible density‐dependent responses that could compensate for the effects of fertility control.

Synthesis and applications. Demographic compensation by pest populations can negate the effects of fertility control. Results from this study suggest that immigration can easily compensate for fertility control in pest species where adult survival is high and fecundity is low. This suggests that fertility control will need to be applied at large spatial scales to reduce this effect. Where adult survival makes a relatively high contribution to the population growth rate, the benefits of fertility control would be enhanced if integrated with conventional control to provide rapid initial population reduction.
Habitat selection by yellowhammers Emberiza citrinella on lowland farmland at two spatial scales: implications for conservation management
Authors: WHITTINGHAM MARK J. , SWETNAM RUTH D. , WILSON JEREMY D. , CHAMBERLAIN DAN E. , FRECKLETON ROBERT P.
Published: April 2005

Yellowhammer Emberiza citrinella populations have declined rapidly in the UK over recent decades, and a clear understanding of their habitat requirements is important to help inform conservation schemes. We aimed to disentangle and rank the effects of winter versus breeding season habitat characteristics.

We used information theoretic methods to analyse the factors determining yellowhammer distribution across 26 sites in England and Wales. We did this at two spatial levels: individual field boundaries and individual territories, the latter consisting of spatial clusters of boundaries.

We considered the role of nine predictor variables, all of which have been suggested in the literature as potentially important. These comprised boundary height and width, and the presence of hedges, trees, ditches, boundary strips, tillage crops, winter set‐aside and winter stubbles.

The results of the statistical modelling showed that winter habitats play an important role in determining where birds locate territories in summer. In particular, the presence of rotational set‐aside fields in winter showed the strongest association with summer territories.

There were minor differences between the territory‐ and boundary‐based models. Most notably, the territory data demonstrated a strong preference for territories containing trees, but this was not observed in the boundary data set. We suggest that the differences between the models may reflect different scales of habitat selection. Boundary occupancy reflects broad distributions of habitat suitability; territory occupancy patterns better reveal detailed habitat requirements.

Regional densities were more closely correlated with the predictions of the boundary‐based model than those of the territory‐based model, and we discuss the implications of this for interpreting habitat association models.

Synthesis and applications. Provision of winter set‐aside fields for summer territory selection by yellowhammers is an important consideration for farm management where conservation is a priority. We show that models based on occupancy of individual boundary units (e.g. hedgerows) correlate with the density of territories at the farm scale; thus farm management practices link directly to population sizes through effects on the quality of breeding habitat.
Can we use the young : female ratio to infer ungulate population dynamics? An empirical test using red deerCervus elaphus as a model
Authors: BONENFANT CHRISTOPHE , GAILLARD JEAN‐MICHEL , KLEIN FRANÇOIS , HAMANN JEAN‐LUC
Published: April 2005

Management decisions for exploited species often rely on count ratios, such as the young to adult female ratio as a proxy of birth rate, and the decrease in the ratio between yearling and females in yeart+ 1 and the young : female ratio in yeartto obtain juvenile survival. However, the reliability of such estimates has yet to be demonstrated.

We investigated the consistency of the young to female ratio method by using observations on individually marked female red deer. These females were known to have raised their calves to weaning successfully. We compared temporal variation in the proportion of females with a calf at heel from count ratios with the probability of observing a calf with its mother from marked animals.

The proportion of females observed with a calf at heel decreased over time (from 0·43 early May to 0·15 early March). This measure was influenced by individual variation and by interactive effects of year and habitat type, although there was no direct relationship with the density of vegetation cover.

The proportion of females seen with a calf at heel assessed from counts did not correspond with the probability of observing a female with a calf at heel, given that she successfully weaned a calf in autumn (estimated from direct observation). The probability of observing a female with a calf was highest in September (0·4) prior to the rut and lowest just after the birth season (0·08) and during the rut (0·18).

The temporal pattern in the probability of observing a calf with its mother, given that she successfully weaned a calf, reflected changes in the mother–calf bond from birth to weaning, rather than changes in offspring mortality or changes in pregnancy rates. These variations in the probability of observing the mother–calf pair in the field may lead to strong biases in count ratio‐based methodologies.

Synthesis and applications. This study has important implications for the management of ungulate populations when decisions are based on count ratios. Our results indicate that count‐based estimates of vital rates are misleading, especially in closed habitats. Pregnancy rate and juvenile survival rate are both key parameters in detecting density‐dependence responses. Reliable estimates of survival and pregnancy rates obtained from marked animals and foetus sampling are more accurate. Alternatively, yearly monitoring of young body mass or bone length coupled with an index of grazing pressure would improve the assessment of population dynamics.
Predicting plant species’ responses to river regulation: the role of water level fluctuations
Authors: LEYER ILONA
Published: April 2005

One of the main targets of river regulation with dams and dykes is the stabilization of highly fluctuating water tables. While there is information about the overall impact of such regulation measures on plant species composition and richness, far less is known about specific species’ response patterns to reduced water level fluctuations.

The response of 30 common grassland species to soil moisture and water level fluctuations was assessed. Floristic data were collected from the floodplain of the Elbe River, Germany, from 182 plots, 99 within the recent floodplain and 83 in an older floodplain, separated from one another by dykes. Hydrological data were collected weekly over 2 years at 37 water level wells. Using logistic regression, the patterns of species’ responses to hydrological regulation were predicted.

The majority of species responded significantly to water level fluctuations. Species of high elevation habitats occurred at lower elevations where water level fluctuations were reduced, indicating increasing drought at high elevation habitats. However, species that occurred in floodplain depressions tended to shift from lower to higher elevations to avoid permanent inundation.

Almost half of the species showed a significant preference for either highly fluctuating water tables, characteristic of the recent floodplain, or for stable water tables, characteristic of the older floodplain. The probability of their occurrence was either reduced or increased along a gradient of reduced fluctuations. These species’ responses could be partly explained by altered flooding regimes, although other factors, such as disturbance and dispersal processes, were also involved.

Synthesis and applications. This study demonstrates that reduced water level fluctuations caused by the construction of dams and dykes lead to substantial changes in the spatial distribution of floodplain plant species and in species composition. The methodology reported here allows accurate prediction of shifts in floodplain vegetation in response to human‐induced alterations in floodplain landscapes. This can be used as a tool to assess river regulation measures and for floodplain restoration purposes, such as dyke relocations.
Predicting locations of moose–vehicle collisions in Sweden
Authors: SEILER ANDREAS
Published: April 2005

Animal–vehicle collisions are a serious problem for road planners and biologists concerned with traffic safety, species conservation and animal welfare. In Sweden, vehicle collisions with moose (MVC) are an important safety issue. Police records average approximately 4500 incidents year−1, including 10–15 human fatalities. New mitigation policies require improved knowledge of the factors influencing the spatial distribution of MVC.

Three logistic regression models were developed to predict MVC risks on public roads for use in strategic and project‐related impact assessment. The models were based on remotely sensed landscape data, road and traffic statistics and estimations of moose density, quantified at 2000 accident and 2000 non‐accident control sites in south‐central Sweden. Model predictions were validated on 2600 1‐km road sections in the county of Örebro, which were classified as either accident or non‐accident roads. Model performances were compared using Akaike's information criterion.

Traffic volume, vehicle speed and the occurrence of fences were dominant factors determining MVC risks, identifying 72·7% of all accident sites. Within a given road category, however, the amount of and distance to forest cover, density of intersections between forest edges, private roads and the main accident road, and moose abundance indexed by harvest statistics, significantly distinguished between accident and control sites. In combination, road–traffic and landscape parameters produced an overall concordance in 83·6% of the predicted sites and identified 76·1% of all test road sections correctly.

Synthesis and applications. The risk of moose–vehicle collisions in Sweden can be predicted from remotely sensed landscape data in combination with road traffic data. Prediction models suggest that reduced vehicle speed in combination with road fencing and increased roadside clearance may provide effective tools for road planners in counteracting MVC. However, effective mitigation will depend on integrated management of the surrounding landscape and moose population, as well as increased responsibility of individual drivers. Remedying animal–vehicle collisions must involve road authorities as much as landowners and the public.
Ecological fitness of a multiple herbicide‐resistant Lolium rigidum population: dynamics of seed germination and seedling emergence of resistant and susceptible phenotypes
Authors: VILA‐AIUB M. M. , NEVE P. , STEADMAN K. J. , POWLES S. B.
Published: April 2005

Quantification of fitness differences between herbicide‐resistant and herbicide‐susceptible weeds permits better prediction of herbicide resistance, and the design of weed management strategies to exploit those traits that result in reduced ecological performance. Reported here is the first attempt to compare the germination and seedling emergence characteristics of one herbicide‐susceptible and two herbicide‐resistant phenotypes from a single weed population.

A series of experiments was carried out in controlled conditions to study seed germination and emergence in Lolium rigidum phenotypes possessing target‐site and non‐target‐site mechanisms of herbicide resistance. Lines composed of herbicide‐susceptible (S), metabolism‐based (P450) and target site‐based (ACCase) resistant individuals, isolated from a single multiple‐resistant population (SLR31), were used in the comparative experiments.

No major differences in seedling emergence were found among the phenotypes when exposed to an alternating 25/15 °C cycle with a 12‐hourly photoperiod. However, the absence of light associated with soil burial (1–8 cm) markedly inhibited total germination and seedling emergence in the ACCase phenotype compared with the S and P450 phenotypes.

Germination at constant temperatures was also inhibited in seeds of the ACCase phenotype, which showed the highest base temperature (Tb) for germination and required more time to reach 50% emergence (tE50) than the S and P450 phenotypes.

Seedling emergence from deep burial (8 cm) in soil promoted significantly higher fatal germination in the S and P450 phenotypes compared with the ACCase phenotype. Despite fatal germination, the S phenotype produced greater emergence from deep burial than both herbicide‐resistant phenotypes.

Synthesis and applications. This study demonstrates differential germination and emergence responses to light and thermal environments between herbicide‐susceptible phenotypes and phenotypes possessing target‐site (ACCase) and non‐target site (P450) herbicide resistance within a single L. rigidum population. Shallow seed burial (1 cm) by any cultivation tool will potentially inhibit seedling recruitment of the ACCase phenotype in contrast with the S and P450 phenotypes, which require less restricted conditions to germinate and emerge.
Moose harvesting strategies in the presence of wolves
Authors: NILSEN ERLEND B. , PETTERSEN TERJE , GUNDERSEN HEGE , MILNER JOS M. , MYSTERUD ATLE , SOLBERG ERLING J. , ANDREASSEN HARRY P. , STENSETH NILS CHR.
Published: April 2005

Large carnivores are currently recolonizing areas where they have been extinct for decades. This poses considerable challenges for wildlife managers, partly because the optimal harvesting strategies of prey populations may be affected. If the carnivores in such areas are under strict management control (as in Scandinavia), the predator will not show a numerical response to changes in prey density. Consequently, the density of prey is mainly determined by the vital rates of the prey population and the predation pressure. In this study we modelled the optimal harvesting strategy for a prey population in which there was no numerical response by the predator.

Our model is an age‐structured deterministic matrix model system. Optimal harvesting strategies are determined, measuring yield either as number of animals harvested or as mass of meat.

First, using a moose population in Hedmark in south‐eastern Norway as a case study, we demonstrate that continuing to harvest at the rates used prior to wolf recolonization will lead to a decline in the moose population.

Secondly, harvesting quotas are specified by age and sex, usually with a high proportion of calves. Although wolves mainly kill juvenile moose (calves and yearlings), the relationship between harvest composition and yield is not affected by predation. Both in the presence and absence of predation, a high proportion of calves in the harvest gives the highest yield measured as the number of animals harvested, whereas a high proportion of adults maximizes the yield measured in terms of meat. Furthermore, a female‐biased sex structure in the population gives a higher yield in both the presence and absence of the predator.

Synthesis and applications. We have shown that managers facing the new challenges presented by recolonizing populations of large predators such as wolves should reduce the size of harvest quotas in order to avoid decreases in prey populations. However, the general relationship between the harvesting strategy and yield maximization is not affected by wolf predation. The harvest yield from cervid populations is often important to local economies, and moose is the single most important game species in Scandinavia. It is therefore important to implement optimal harvesting strategies under these new conditions in order to prevent an unnecessary loss of yield, and success in this task may in turn affect local attitudes towards large carnivores.
An assessment of grassland restoration success using species diversity components
Authors: MARTIN LEANNE M. , MOLONEY KIRK A. , WILSEY BRIAN J.
Published: April 2005

We do not know which aspects of community structure and ecosystem processes are restorable for most ecosystems, yet this information is crucial for achieving successful restoration.

We quantified three success criteria for 8–10‐year‐old grassland plantings in large‐scale tallgrass prairie restoration (reconstruction) sites relative to three nearby prairie remnant sites. The restoration sites included management of native ungulates and fire, important regulators of diversity and patchiness in intact grasslands. These have not been incorporated simultaneously into previous studies of restoration success.

We used the additive partitioning model of diversity, where α is neighbourhood (quadrat) scale diversity, β is accumulation of species diversity across neighbourhoods, and γ is total diversity. We decomposed α into richness and evenness to determine if both were equally restored.

The proportion of exotic biomass was similar between the restoration and remnant sites, but the proportion of exotic species and above‐ground net primary productivity remained between two and four times higher in the restoration sites.

Alpha diversity (Simpson's 1/D) and richness (S) values were exceptionally high in remnant sites, and approximately twice those of the restoration sites. Alpha evenness was similar between the restoration and remnant sites.

Distance per se between quadrats was not related to diversity after accumulated quadrat area was taken into account. Therefore, we may be able to use the additive partitioning model of diversity in areas that differ in size, at least at the scale of this study.

Contrary to our original predictions, the proportion of β diversity (1 − D) was approximately twice as high in the restoration sites than in remnant sites, possibly because patches of individual species were larger in the restoration.

Synthesis and applications. We have shown that current restoration methods are unable to restore plant diversity in tallgrass prairie. Grassland restoration will be improved if the number of species that co‐exist can be increased. New, local‐scale restoration techniques are needed to replicate the high levels of diversity observed in tallgrass prairie remnant sites.
Beyond the Mediterranean peninsulas: evidence of central European glacial refugia for a temperate forest mammal species, the bank vole (Clethrionomys glareolus)
Authors: DEFFONTAINE V. , LIBOIS R. , KOTLÍK P. , SOMMER R. , NIEBERDING C. , PARADIS E. , SEARLE J. B. , MICHAUX J. R.
Published: April 2005

This study details the phylogeographic pattern of the bank vole, Clethrionomys glareolus, a European rodent species strongly associated with forest habitat. We used sequences of 1011 base pairs of the mitochondrial DNA cytochrome b gene from 207 bank voles collected in 62 localities spread throughout its distribution area. Our results reveal the presence of three Mediterranean (Spanish, Italian and Balkan) and three continental (western, eastern and ‘Ural’) phylogroups. The endemic Mediterranean phylogroups did not contribute to the postglacial recolonization of much of the Palaearctic range of species. Instead, the major part of this region was apparently recolonized by bank voles that survived in glacial refugia in central Europe. Moreover, our phylogeographic analyses also reveal differentiated populations of bank voles in the Ural mountains and elsewhere, which carry the mitochondrial DNA of another related vole species, the ruddy vole (Clethrionomys rutilus). In conclusion, this study demonstrates a complex phylogeographic history for a forest species in Europe which is sufficiently adaptable that, facing climate change, survives in relict southern and northern habitats. The high level of genetic diversity characterizing vole populations from parts of central Europe also highlights the importance of such regions as a source of intraspecific genetic biodiversity.
An interspecific comparison of foraging range and nest density of four bumblebee (Bombus) species
Authors: KNIGHT M. E. , MARTIN A. P. , BISHOP S. , OSBORNE J. L. , HALE R. J. , SANDERSON R. A. , GOULSON D.
Published: April 2005

Bumblebees are major pollinators of crops and wildflowers in northern temperate regions. Knowledge of their ecology is vital for the design of effective management and conservation strategies but key aspects remain poorly understood. Here we employed microsatellite markers to estimate and compare foraging range and nest density among four UK species: Bombus terrestris, Bombus pascuorum, Bombus lapidarius, and Bombus pratorum. Workers were sampled along a 1.5‐km linear transect across arable farmland. Eight or nine polymorphic microsatellite markers were then used to identify putative sisters. In accordance with previous studies, minimum estimated maximum foraging range was greatest for B. terrestris (758 m) and least for B. pascuorum (449 m). The estimate for B. lapidarius was similar to B. pascuorum (450 m), while that of B. pratorum was intermediate (674 m). Since the area of forage available to bees increases as the square of foraging range, these differences correspond to a threefold variation in the area used by bumblebee nests of different species. Possible explanations for these differences are discussed. Estimates for nest density at the times of sampling were 29, 68, 117, and 26/km2 for B. terrestris, B. pascuorum, B. lapidarius and B. pratorum, respectively. These data suggest that even among the most common British bumblebee species, significant differences in fundamental aspects of their ecology exist, a finding that should be reflected in management and conservation strategies.
The sphincter of Oddi: understanding its control and function
Authors: Woods C. M. , Mawe G. M. , Toouli J. , Saccone G. T. P.
Published: April 2005

Abstract  The most common functional disorders of the biliary tract and pancreas are associated with disordered motility of the sphincter of Oddi (SO). The SO is a neuromuscular structure located at the junction of the bile and pancreatic ducts with the duodenum. The primary functions of the SO are to regulate the delivery of bile and pancreatic juice into the duodenum, and to prevent the reflux of duodenal contents into the biliary and pancreatic systems. Disordered motility of the SO leads to the common and painful clinical conditions of SO dysfunction and acute pancreatitis. In order to understand normal SO motility, studies have been performed addressing SO function, control of spontaneous SO activity, responses to bioactive agents, SO innervation, and reflexes with other gastrointestinal organs. These studies have led to the current understanding of how the SO functions and may permit the development of targeted therapy for SO dysfunction and acute pancreatitis. This review summarizes the current knowledge regarding the control and regulation of SO motility, highlighting laboratory based and clinical research performed over the last 5 years.