bluuebunny/crossref_metadata_2025 huggingface dataset:
Magneto-optical Kerr rotation enhancement in Co–ZnO inhomogeneous magnetic semiconductor
Authors: Zhang Y. P. , Yan Shi-Shen , Liu Yi-Hua , Ren Miao-Juan , Fang Y. , Chen Y. X. , Liu G. L. , Mei L. M. , Liu J. P. , Qiu J. H. , Wang S. Y. , Chen L. Y.
Published: July 2006

The polar Kerr rotation and ellipticity spectra of the as-deposited and annealed Zn1−xCoxO inhomogeneous magnetic semiconductors were measured. The Kerr rotation spectra versus the photon energy can be greatly modulated by adjusting the Co concentration or annealing the samples. Moreover, the observed maximal Kerr rotation, 0.72°, in an annealed sample is higher than that of pure Co films, Pt∕Co multilayers, and PtxCo1−x alloys. The enhanced Kerr rotation in the annealed samples can be explained by the fact that the annealed samples became a nanocomposite system consisting of Co clusters and Zn1−xCoxO magnetic semiconductor.
Density fluctuations measured by a mm-wave collective scattering in helicon plasmas
Authors: Kwak Jong-Gu , Wang S. J. , Kim S. K. , Cho Suwon
Published: July 2006

Density fluctuations in helicon plasmas propagating perpendicular to the static axial magnetic field are observed by using a mm-wave collective scattering method. There exist two kinds of density fluctuations, and the high-frequency fluctuation around 500kHz follows the dispersion relation of the acoustic waves.
Molecular bond selective x-ray scattering for nanoscale analysis of soft matter
Authors: Mitchell G. E. , Landes B. G. , Lyons J. , Kern B. J. , Devon M. J. , Koprinarov I. , Gullikson E. M. , Kortright J. B.
Published: July 2006

We demonstrate the utility of resonant soft x-ray scattering in characterizing heterogeneous chemical structure at nanometer length scales in polymer films and nanostructures. Resonant enhancements near the carbon K edge bring bond specific contrast and increased sensitivity to bridge a gap between x-ray absorption contrast in chemical sensitive imaging and higher spatial resolution hard x-ray and neutron small-angle scattering. Chemical bond sensitivity is illustrated in the scattering from latex spheres of differing chemistry and size. Resonant enhancements are then shown to yield sensitivity to heterogeneity in two-phase polymer films for which hard x-ray and nondeuterated neutron scattering lack sensitivity due to low contrast.
Characteristics of sputtered Hf1−xSixO2∕Si∕GaAs gate stacks
Authors: Zhang M. H. , Ok I. J. , Kim H. S. , Zhu F. , Lee T. , Thareja G. , Yu L. , Lee Jack C.
Published: July 2006

Sputtered Hf1−xSixO2∕Si∕n-type GaAs gate stacks with x=0, 30%, and 47% have been characterized using x-ray photoelectron spectroscopy, photoluminescence, and capacitance-voltage (CV) measurements. Incorporating Si into HfO2 improves both frequency dispersion and hysteresis. Compared to HfO2, 30% and 47% Hf1−xSixO2 have a lower interface state density and stronger photoluminescence intensity. At the same capacitance equivalent thickness, HfO2 and 30% Hf1−xSixO2 have a smaller leakage current density than 47% Hf1−xSixO2. It is concluded that Hf1−xSixO2 with the composition near 30% is a good high-k dielectric candidate for metal-oxide-semiconductor device application.
Low-resistance Ohmic contacts for high-power GaN field-effect transistors obtained by selective area growth using plasma-assisted molecular beam epitaxy
Authors: Hong Seung Jae , Kim Kyekyoon (Kevin)
Published: July 2006

Selective area growth (SAG) has been demonstrated using plasma-assisted molecular beam epitaxy (PAMBE) resulting in vastly improved Ohmic contacts for GaN-based high-power field-effect transistors (FETs). A heavily doped n-GaN layer was grown only in the Ohmic contact region and the resulting nonalloyed Ti∕Al∕Ti∕Au metal contacts exhibited linear Ohmic behavior. Through rapid thermal annealing, very low specific contact resistivity (1.8×10−8Ωcm2) was obtained at 850°C. Furthermore, contact resistances below 0.8Ωmm were obtained by annealing at a wide range of temperatures (750–950°C). GaN metal-semiconductor FETs were fabricated to investigate the effect of the PAMBE-SAG on device performance, producing great improvement in the dc characteristics.
An evanescent-coupling approach to making stable fiber-coupled semiconductor lasers
Authors: Khalili Alireza , Bae Hopil , Harris James S.
Published: July 2006

We present a fiber-coupled GaAs laser, which works on the principle of evanescent coupling between a semiconductor antiresonant reflecting optical waveguide and a side-polished single-mode fiber. Compared to conventional fiber-coupled semiconductor lasers, these devices enjoy more relaxed alignment tolerances and simpler packaging, as well as high immunity to catastrophic mirror damage that limits the maximum power output of most edge-emitting lasers. Moreover, the small coupling window here provides an inherent filter that guarantees wavelength stability without any gratings. The initial data show stable single-frequency operation with more than 27dB side-mode suppression ratio and a small thermal coefficient of 0.06nm∕°C.
Decay dynamics of the positively charged exciton in a single charge tunable self-assembled quantum dot
Authors: Dalgarno P. A. , McFarlane J. , Gerardot B. D. , Warburton R. J. , Karrai K. , Badolato A. , Petroff P. M.
Published: July 2006

We report on the decay dynamics of positively charged excitons confined to single InAs quantum dots embedded in an n-type field-effect structure. The positively charged exciton’s dynamics are found to be strongly dependent on device dimensions. With a large (small) dot capping layer the decay is dominated by hole tunneling (radiative recombination). The hole tunneling is successfully modeled with a WKB-like zero-dimensional to three-dimensional tunneling approximation. Hole tunneling is not observed in the dynamics of the neutral exciton negatively charged exciton, or biexciton, an effect we attribute to an increase in barrier height through the interdot Coulomb interactions.
The Properties of Isolated Main Galaxies in Sloan Digital Sky Survey Data Release 3 (SDSS DR3)
Authors: Deng Xinfa , Ma Xinsheng , Luo Chenghong , Zhang Qun , Liao Qing-Hua , He Ji-zhou
Published: July 2006

We have constructed a Main galaxy subsample of 67777 galaxies with redshifts in the range 0.08 ≤ z ≤ 0.12 from the Sloan Digital Sky Survey Data Release 3. Using cluster analysis, two isolated Main galaxy samples were extracted from this subsample. The two isolated Main galaxy samples identified at different radii have the same properties. Additionally, we find fewer early-type galaxies in isolated Main galaxy samples than in a close double galaxy sample.
An Atomic and Molecular Study of the Interstellar Medium Around the Supernova Remnant RCW 103
Authors: Paron Sergio A. , Reynoso Estela M. , Purcell Cormac , Dubner Gloria M. , Green Anne
Published: July 2006

We report on the detection of HCO+ and 12CO emission in the rotational transition J = 1–0 in the vicinity of the shock front at the southern border of the supernova remnant RCW 103, where previous infrared observations suggest an interaction with a molecular cloud. The observations were carried out with the Australian Millimeter Radiotelescope at Mopra. We observed a depletion of HCO+ behind the supernova shock front. In addition, we studied the interstellar medium over an extended region towards RCW 103 based on archival λ 21 cm Hı line observations from the Australia Telescope Compact Array (ATCA) and the Parkes Telescope. No atomic gas was observed in emission in coincidence with the molecular feature. This absence was interpreted in terms of self-absorption processes.
An Advanced, Three-Dimensional Plotting Library for Astronomy
Authors: Barnes David G. , Fluke Christopher J. , Bourke Paul D. , Parry Owen T.
Published: July 2006

We present a new, three-dimensional (3D) plotting library with advanced features, and support for standard and enhanced display devices. The library — s2plot — is written in c and can be used by c, c++, and fortran programs on GNU/Linux and Apple/OSX systems. s2plot draws objects in a 3D (x,y,z) Cartesian space and the user interactively controls how this space is rendered at run time. With a pgplot-inspired interface, s2plot provides astronomers with elegant techniques for displaying and exploring 3D data sets directly from their program code, and the potential to use stereoscopic and dome display devices. The s2plot architecture supports dynamic geometry and can be used to plot time-evolving data sets, such as might be produced by simulation codes. In this paper, we introduce s2plot to the astronomical community, describe its potential applications, and present some example uses of the library.
Forty Years of Progress in Long-Baseline Optical Interferometry: 2005 Robert Ellery Lecture
Authors: Davis John
Published: July 2006

The development of long-baseline optical interferometry in Australia from the Narrabri Stellar Intensity Interferometer (NSII) to the Sydney University Stellar Interferometer (SUSI) and the resulting technical and scientific achievements are described. Three examples of results from the SUSI programme, for a single star, a double-lined spectroscopic binary, and a Cepheid variable, are presented to illustrate the advances made in the past four decades. The leading role that Australia has played in the development of the field worldwide is discussed from a personal viewpoint. Long-baseline optical interferometry has promised much, has been slow to deliver, and has been restricted to black-belt interferometrists, but it has now matured to the point where it is becoming an observational technique for astronomers in general.
Technology enhancing learning: analysing uses of information and communication technologies by primary and secondary school pupils with learning frameworks
Authors: Passey Don
Published: July 2006

Successive national policy in England has striven to develop uses of information and communication technologies (ICT) to support teaching and learning, and has promoted the adoption of ICT in schools over a period of some 25 years (since the ‘Microcomputer in schools initiative’ of 1981). The current level of deployment of ICT in schools is high. Not only are current levels higher than ever before, but the diversity of forms of ICT have also increased. These high levels and wide diversity create challenges for teachers, in terms of understanding how to select appropriate uses of ICT to support learning most effectively in specific situations. A clear need is for teachers to know how each form of ICT supports precise aspects of learning, in each subject area, topic and activity. Teachers need to consider the forms of technological resources that are accessible, how these specifically work within learning environments in classroom (and other) settings, and how uses of resources match social, behavioural, emotional and cognitive needs of pupils. This article offers a perspective of the pedagogical needs of teachers, by considering a particular selection of learning technologies, how these are used within learning environments, and how it is possible to view their impact on pupil cognition. A set of starting frameworks, through which to analyse impact, is considered, and the findings from example sets of case studies indicate how uses of ICT have been focused by teachers, and where potential forms of impact have arisen. The findings indicate a need for more detailed data gathering, both to provide evidence that will offer a greater insight into specific aspects of learning that are supported when certain forms of ICT are used, and to give an indication of gaps in learning focus that might arise. From the results of the analyses presented, implications for policy, practice, evaluation and research are highlighted and discussed.
Consequences of elevated temperatures on life‐history traits of an introduced fish, pumpkinseed Lepomis gibbosus
Authors: Dembski S. , Masson G. , Monnier D. , Wagner P. , Pihan J. C.
Published: July 2006

Life‐history reactions of a pumpkinseed Lepomis gibbosus population in north‐eastern France exposed to heated waters were studied. The study was conducted from 2001 to 2003 in an artificial reservoir, adjacent to a nuclear power plant, in which water temperatures are cool in winter (8·2–12·4° C) and rise early in spring (April: 14·7° C) nearly 5° C and 3° C over the temperature of its tributary, respectively. Fast growth among young‐of‐the‐year, precocious maturity and short life span were observed, in contrast to related studies. The short life span appeared to be the price paid for early maturity in breeding fish, which suffered high mortality rates just after their first reproduction.
Biochemical composition of the Atlantic bonito Sarda sarda from the Aegean Sea (eastern Mediterranean Sea) in different stages of sexual maturity
Authors: Zaboukas N. , Miliou H. , Megalofonou P. , Moraitou‐Apostolopoulou M.
Published: July 2006

The content (% wet mass) in water, ash, lipid, crude protein, DNA and RNA of different tissues was determined during sexual maturation of bonitos Sarda sarda from the Aegean Sea. A total of 220 specimens were collected in the following stages of sexual maturity: immature, resting, developing, mature, spawning and spent. Highest lipid levels in the white muscle, red muscle and liver were measured in immature specimens, while lowest levels were found in spawning bonitos. The gradual percentage of lipid reduction from immature to spawning bonitos was relatively higher in the liver (females 71·2% and males 64·4%) than in the white (females 59·2% and males 53·5%) and red (females 62·1% and males 51·7%) muscle. Lipid levels in the gonads increased gradually from the immature to spawning stage. The decrease of lipid in the somatic tissues was more intense in females than in males, and gonadal lipid content was higher in females than in males. There was a strong reverse correlation between water and lipid percentage in all tissues. Protein content decreased significantly only in spawning bonitos. The percentage of protein reduction from immature to spawning stage was relatively higher in males than in females in both white (females 3·4% and males 4·6%) and red (females 4·6% and males 5·1%) muscles. Protein content in the liver was significantly lower than in the other tissues, being highest in mature females. Gonadal protein content in females increased with maturation and decreased after spawning. The content in ash exhibited considerable stability. The RNA:DNA ratio exhibited a similar pattern of variation in both muscles. The RNA:DNA ratio increased during gonadal development gradually from the developing to spent stage. It was concluded that in S. sarda during gonadal development, there was an increase in gonadal lipid accompanied by a decrease in somatic tissue lipid reserves. Thus, reproductive inactive bonitos have more lipid in their edible part and a higher nutritional value than active ones.
The ecological significance of the zooplanktivores, snipefish Macroramphosus spp. and boarfish Capros aper, in the food web of the south‐east North Atlantic
Authors: Lopes M. , Murta A. G. , Cabral H. N.
Published: July 2006

The diets of slender snipefish Macroramphosus gracilis, longspine snipefish Macroramphosus scolopax and boarfish Capros aper, three very abundant species on the Portuguese coast, were studied from samples collected between July 2002 and April 2003. Variations in the diet with fish size, season and area, as well as diet overlap and diversity, are explored in this study. The diets of slender snipefish and boarfish were mainly composed of copepods, with the main prey being Temora spp. and Calanus spp., respectively. Mysid shrimps were the most important food item in the diet of longspine snipefish. During the summer season, when the availability of different prey items was highest, the two species of snipefish and the boarfish fed on different prey. Temora spp. were the most important prey in the stomachs of slender snipefish in the summer on the south‐west coast, while Calanus spp. started appearing in the stomachs of boarfish in the spring in the north, increasing their abundance in the summer on the south and south‐west coasts. The abundance of mysids appeared to increase in the autumn on the south‐west coast, being at that time an important food item for both longspine snipefish and boarfish. For slender snipefish and boarfish, the differences in stomach species diversity were explained firstly by the season and then by the area and fish size. For longspine snipefish, the area did not explain the species diversity variability, season being the first variable determining the differences. Of all three species, slender snipefish was the one with highest diversity of stomach contents, particularly in spring and summer on the north and south‐west coasts. Diet overlap between species was very low. No predation on eggs and larval stages of fishes was found for any of these fish species. This work is the first to address the diets of snipefish species and boarfish in the south‐east North Atlantic, in a large spatio‐temporal coverage. These species are important prey for many commercial species on the Portuguese coast and, given their abundance, may have a great impact on zooplankton communities, thus assuming a pivotal position in marine food webs.
Diet of Pacific sleeper shark, a potential Steller sea lion predator, in the north‐east Pacific Ocean
Authors: Sigler M. F. , Hulbert L. B. , Lunsford C. R. , Thompson N. H. , Burek K. , O’Corry‐Crowe G. , Hirons A. C.
Published: July 2006

Pacific sleeper sharks Somniosus pacificus were captured near Steller sea lion Eumetopias jubatus rookeries during the period when Steller sea lion pups are most vulnerable to Pacific sleeper shark predation (first water entrance and weaning). Analysis of stomach contents revealed that teleosts were the dominant prey in August and cephalopods were the dominant prey in May (n = 198). Marine mammals were found in 15% of stomachs regardless of season, but no Steller sea lion tissues were detected. Molecular genetic analysis identified grey whale Eschrichtius robustus and harbour seal Phoca vitulina remains in some Pacific sleeper shark stomachs. Most mammals were cetacean and at least 70% of the cetaceans were probably scavenged. Although Pacific sleeper shark and Steller sea lion ranges overlapped, so predation could potentially occur, the diet study suggested that predation on Steller sea lions is unlikely, at least when pups first enter the water or during weaning. Harbour seals were infrequent prey and may have been consumed alive. Pacific sleeper sharks consume fast‐swimming prey like Pacific salmon Oncorhynchus sp., most likely live animals rather than scavenged animals. Pacific sleeper sharks appeared to be opportunistic consumers of the available prey and carrion, feeding both on the bottom and in the water column, and their diet shifted to teleosts and cetacean carrion as the fish grew larger.
Variable growth rates of the tropical estuarine fish barramundi Lates calcarifer (Bloch) under different freshwater flow conditions
Authors: Robins J. , Mayer D. , Staunton‐Smith J. , Halliday I. , Sawynok B. , Sellin M.
Published: July 2006

Relationships between freshwater flows and growth rates of the opportunistic predatory finfish barramundi Lates calcarifer in a dry tropical estuary were examined using data from a long‐term tag‐recapture programme. Lagged effects were not investigated. After accounting for length at release, time at liberty and seasonal variation (e.g. winter, spring, summer and autumn), growth rates were significantly and positively related to fresh water flowing to the estuary. Effects were present at relatively low levels of freshwater flow (i.e. 2·15 m3 s−1, the 5th percentile of the mean flow rate experienced by fish in the study during time at liberty). The analysis, although correlative, provides quantitative evidence to support the hypothesis that freshwater flows are important in driving the productivity of estuaries and can improve growth of species high in the trophic chain.
Digestive enzymes of Anarhichas minor and the effect of diet composition on their performance
Authors: Papoutsoglou E. S. , Lyndon A. R.
Published: July 2006

The effect of feeding two different diets, containing 38 and 45% protein and 35 and 28% lipid, respectively, on growth as well as performance of the digestive proteases (total protease at pH 1·5, 7·0, 9·0 and 10·0) and carbohydrases (total carbohydrase, α‐amylase and α‐glucosidase) of a new candidate species for aquaculture, the carnivorous spotted wolffish Anarhichas minor (Teleostei, Anarhichadidae), was investigated. No significant growth differences were observed when feeding high protein (HP) or low protein (LP) levels (P > 0·05), although the LP group exhibited slightly higher protease activity and capacity (P > 0·05), mostly at the anterior end of the intestine and at alkaline pH. Carbohydrase levels were generally low, apart from α‐glucosidase, which was significantly increased for the HP group (P < 0·05). Implications concerning the performance of digestive enzymes under varying dietary macronutrient levels and effects of digestive enzyme activity on the formulation of efficient artificial diets for carnivorous fishes are discussed in this study.
Temporal stability in size distributions and growth rates of threeEsox luciusL. populations. A result of cannibalism?
Authors: Persson L. , Bertolo A. , De Roos A. M.
Published: July 2006

The population total length (LT) structures and individual growth trajectories for three stream living pikeEsox luciuspopulations were studied for 7 years. All three populations exhibited small variation in both populationLTstructure and individual growth trajectories over time. These dynamics contrasted to the much more variable populationLTstructure of perchPerca fluviatilisstudied previously. The difference in population dynamics between the two species was related to differences in prey:predator size ratios. The pike populations in the more open and larger streams grew to larger sizes, but this difference in life history did not affect population dynamics of pike. It is concluded that (1) cannibalistic population dynamics may be predicted from individual life‐history characteristics such as minimum and maximum victim:cannibal size ratios and (2) the cannibal‐driven population dynamics observed in pike seems to be robust to variation in environmental conditions (system openness).
Comparison of feed intake behaviour and stress response in isolated and non‐isolated African catfish
Authors: Martins C. I. M. , Trenovski M. , Schrama J. W. , Verreth J. A. J.
Published: July 2006

This study shows that in African catfish Clarias gariepinus feed intake (IF) is stimulated by the presence of conspecifics resulting in higher IF and growth rate. The feeding duration and the frequency of feeding acts were lower in isolated fish as compared with non‐isolated fish, indicating a decreased feeding motivation when fish are held individually. Isolation per se, however, seems not to act as a stressor in the short‐term or to affect the stress response, probably because periods of isolation are part of the African catfish lifestyle.
β‐Oxidation capacity in liver increases during parr‐smolt transformation of Atlantic salmon fed vegetable oil and fish oil
Authors: Stubhaug I. , Lie Ø. , Torstensen B. E.
Published: July 2006

Atlantic salmon Salmo salar were fed diets containing 100% fish oil (FO; capelin oil) or 100% vegetable oil (VO) from start of feeding until the fish reached the size of 2·5 kg. Samples were taken during the period of the parr‐smolt transformation (October 2002 to February 2003). The VO diet consisted of a blend of 55% rapeseed oil, 30% palm oil and 15% linseed oil to maintain the sum of saturated, monounsaturated and polyunsaturated fatty acids between the two diets, although with differences in the individual chain length of fatty acids. Na+/K+‐ATPase activity in the gills, total β‐oxidation capacity in muscles and liver and total lipid, glycogen and dry matter content in the muscles were measured during the parr‐smolt transformation and after seawater transfer. Na+/K+‐ATPase activity in gills increased prior to seawater transfer, showing an adaptation for seawater survival. Major changes in the lipid and glycogen content in the fillet and in β‐oxidation capacity were found in the tissues measured. β‐oxidation capacity increased significantly in liver and decreased in red muscle, prior to seawater transfer, giving liver an important role in energy production during this period. Results also indicated that feeding Atlantic salmon a diet where 100% of FO was replaced with VO did not have any negative effects on lipid metabolism during parr‐smolt transformation.
Effect of temperature changes on the reproductive cycle of roach in Lake Geneva from 1983 to 2001
Authors: Gillet C. , QuéTin P.
Published: July 2006

In Lake Geneva, the surface water temperature has increased by 1° C over 20 years probably as a result of climate change. The effects of changes in temperature on the reproductive cycle of the roach Rutilus rutilus were assessed in a 19 year survey. Over time, spawning tended to begin earlier. The consequences of temperature changes were assessed on two different stages of the female reproductive cycle: the development of the ovaries from the beginning of autumn to ovulation, and the onset of the spawning period. The development of the ovaries was studied for 7 consecutive years from October to June. From 1 October to the onset of spawning, it was possible to assess the gonado‐somatic index (IG) of females in terms of time expressed as a sum of degree‐days. The correlation between IG and the sum of degree‐days was +0·97. The onset of the roach spawning period in Lake Geneva was triggered by a thermal threshold (median and range 190 ± 10 degree‐days for the 15 previous days). From October to April, climate warming accelerated the development of gonads, then in May, a thermal threshold that triggered the onset of roach spawning occurred earlier.
Effects of species, culture history, size and residency on relative competitive ability of salmonids
Authors: Blann C. A. , Healey M. C.
Published: July 2006

The relative competitive ability of juvenile farm and wild salmonids was investigated to provide insight into the potential effects of introduction of cultured salmon on wild Pacific salmonid (Oncorhynchus) species. Aquarium experiments involving equal contests (i.e. size matched, simultaneously introduced individuals) indicated that two wild coho salmon Oncorhynchus kisutch populations were competitively equal to a farm coho salmon population. In equal contests between farm Atlantic salmon Salmo salar (Mowi strain) and these wild coho salmon populations or coastal cutthroat trout Oncorhynchus clarki clarki, Atlantic salmon were subordinate in all cases. When Atlantic salmon were given a residence advantage, however, they were competitively equal to both wild coho salmon populations, but remained subordinate to coastal cutthroat trout. When Atlantic salmon were given a 10–30% length advantage, they were competitively equal to one wild coho salmon population but remained subordinate to the other. In equal contests in semi‐natural stream channels, both wild coho and farm Atlantic salmon grew significantly more in the presence of the other species than when alone. It appears that coho salmon obtain additional food ration by out competing Atlantic salmon, whereas Atlantic salmon were stimulated to feed more in the presence of coho salmon competitors. These results suggest that wild coho salmon and cutthroat trout should out compete farm Atlantic salmon of a similar size in nature. As the relative competitive ability of Atlantic salmon improves when they have a size and residence advantage, should feral populations become established, they may exist on a more equal competitive footing owing to the long freshwater residence of Atlantic salmon.
Notes on the natural diet and habitat of eight danionin fishes, including the zebrafishDanio rerio
Authors: McClure M. M. , McIntyre P. B. , McCune A. R.
Published: July 2006

The diet and habitat of eight danionin species (DanioandDevario) from 18 sites in India and Thailand are reported. At every site, habitat characteristics, including pH, light penetration, water temperature, current speed, stream dimensions, canopy cover and substratum type, were recorded. Danionins were found primarily in warm (24–35° C), moving water of moderate clarity and pH (6·6–8·2) and there were significant differences among species in water temperature, pH and current speed. Deep‐bodiedDevariospecies were generally associated with faster water currents than more slender‐bodiedDaniospecies. Gut content analyses of 327 individuals representing 17 populations showed that insects were the primary food resource for the eightDanioandDevariospecies. Crustaceans, fish scales, algae and detritus were also important supplements for particular species. Stable isotope data from syntopic species indicated long‐term differences in consumption of terrestrialv.aquatic insects in one of two population pairs.
Changes to chloride and rodlet cells in gills, kidney and intestine of Dicentrarchus labrax (L.) exposed to reduced salinities
Authors: Giari L. , Manera M. , Simoni E. , Dezfuli B. S.
Published: July 2006

The effect of osmotic shock was investigated mainly in the chloride cells (CCs) and rodlet cells (RCs) of gills, and RCs of intestine and kidney of the European sea bass Dicentrarchus labrax obtained from a farm in the northern Adriatic Sea. During the experiment, fish were abruptly transferred from sea water to a salinity of 15 (15 SW) or to fresh water (FW). Numeric variation and ultrastructural changes of both cell types were evaluated at 24, 48 and 96 h after the transfer to lower salinity levels, using light and transmission electron microscopy (TEM). Exposure to FW produced a significant increase (P < 0·05) in the number of branchial CCs and RCs within 96 and 24 h, respectively. Following osmotic challenge (either transfer to 15 SW or FW), kidney and intestine showed an evident increase in RC numbers. The cellular damage detected by TEM was the same for each sampling time (24, 48 and 96 h), but appeared more severe in fish exposed to FW (higher osmotic shock) than in those exposed to 15 SW. In RCs cytoplasmic vacuolizations, autophagosomes and autophagolysosomes with myelinoid bodies, dissolution and shrinkage of the typical inclusions were documented. Nevertheless, CCs showed vacuolization of endoplasmic reticulum and cytoplasmic dissolution and maintained the apical crypt typical of seawater acclimated fish. Renal tubular cells and intestinal epithelial cells showed similar changes to those reported for CCs and RCs.
The diet of Horabagrus brachysoma (Gunther), an endangered bagrid catfish from Lake Vembanad (South India)
Authors: Sreeraj N. , Raghavan R. , Prasad G.
Published: July 2006

A stomach content analysis of Horabagrus brachysoma from Lake Vembanad, South India, showed that this species was omnivorous and euryphagous, with few qualititative differences in the diet among size classes. Feeding rates changed over the course of a year in response to environmental change associated with the monsoon.
An experimental and numerical study on flow and transport in a field soil using zero‐tension lysimeters and suction plates
Authors: Kasteel R. , Pütz T. , Vereecken H.
Published: July 2006

Zero‐tension lysimeters are widely applied to study the fate of chemicals in the subsurface environment. However, conditions in lysimeters differ from the field situation, because local saturation is required at the lower boundary to collect leachate. The objective was to characterize the influence of the lower boundary on the flow and transport behaviour of bromide observed in six 1.2‐m‐long lysimeters and in the field by 30 suction plates installed at 1.2‐m depth, which were operated with a time‐variable suction equal to the ambient soil water potential. A bromide pulse was applied at the bare surface of a silty soil in autumn 1997 and monitored for 2.5 years. The mean leachate flux was 0.98 mm day−1 for the lysimeters versus 0.66 mm day−1 for the suction plates. The lysimeters had a slightly slower effective mean pore‐water velocity, expressed as transport distance per unit of leaching depth, and exhibited more solute spreading than the suction plates. Numerical simulations revealed that the amount of water collected with the suction plates was sensitive to the hydraulic conductivity of the plates. The spatial variability in hydraulic properties in the model explained the observed variability in cumulative leachate, at least qualitatively. The arrival time and spreading of the breakthrough curves (BTCs) were well described by the simulations in the lysimeters, but were underestimated in the suction plates. Preferential flow through macropores, which is not an effective carrier for bromide, might be the reason for this discrepancy. Molecular diffusion contributed significantly to solute spreading and enhanced lateral mixing. Both the experiments and the simulations revealed that the dispersivity derived from BTCs is significantly influenced by the observation method and experimental conditions.
Seasonal variation in the temperature response of leaf respiration in Quercus rubra: foliage respiration and leaf properties
Authors: XU C.‐Y. , GRIFFIN K. L.
Published: July 2006

Leaf respiratory temperature responses and general leaf properties of Quercus rubra were measured throughout the 2003 growing season in a deciduous forest in the north‐eastern USA. Measurements were made in the upper and lower portions of the canopy at two sites with different soil water availability. Correlations among respiration and various leaf properties were examined.

At a set temperature (10 and 20 °C), area‐based leaf respiration rates were higher in both the early and late growing season than in the mid‐growing season (0·50 vs 0·33 µmol CO2 m−2 s−1 at 10 °C, on average). Upper‐canopy leaves generally had higher respiration rates than lower‐canopy leaves (0·53 vs 0·30 µmol CO2 m−2 s−1 at 10 °C, on average). At the drier site a more significant seasonal pattern in respiration was observed, while at the more mesic site a stronger canopy‐position effect was detected. E0, a model variable related to the overall energy of activation of respiration, varied only slightly (52 ± 5 kJ mol−1 K−1), and was not influenced by season, site or canopy position.

Leaf properties (specific leaf area, nitrogen, soluble sugars) also varied with season, site and canopy position. Leaf N and reducing monose were positively correlated with leaf respiration rates. After isolating single factors (season, site, canopy position), reducing monose could partially explain the seasonality in respiration (32−79%), and leaf N (Narea) was well correlated with the canopy‐position effect.

Our results suggest that the temporal and spatial heterogeneities of respiration need to be considered in ecosystem models, but significant simplifications may be made in Q. rubra by assuming a constant temperature coefficient (E0, 52·5 kJ mol−1 in this study) or predicting the base respiration rate (R0) from well understood leaf properties.
The dependence of respiration on photosynthetic substrate supply and temperature: integrating leaf, soil and ecosystem measurements
Authors: HARTLEY IAIN P. , ARMSTRONG ANNA F. , MURTHY RAMESH , BARRON‐GAFFORD GREG , INESON PHIL , ATKIN OWEN K.
Published: July 2006

Interactions between photosynthetic substrate supply and temperature in determining the rate of three respiration components (leaf, belowground and ecosystem respiration) were investigated within three environmentally controlled, Populus deltoides forest bays at Biosphere 2, Arizona. Over 2 months, the atmospheric CO2 concentration and air temperature were manipulated to test the following hypotheses: (1) the responses of the three respiration components to changes in the rate of photosynthesis would differ both in speed and magnitude; (2) the temperature sensitivity of leaf and belowground respiration would increase in response to a rise in substrate availability; and, (3) at the ecosystem level, the ratio of respiration to photosynthesis would be conserved despite week‐to‐week changes in temperature. All three respiration rates responded to the CO2 concentration‐induced changes in photosynthesis. However, the proportional change in the rate of leaf respiration was more than twice that of belowground respiration and, when photosynthesis was reduced, was also more rapid. The results suggest that aboveground respiration plays a key role in the overall response of ecosystem respiration to short‐term changes in canopy photosynthesis. The short‐term temperature sensitivity of leaf respiration, measured within a single night, was found to be affected more by developmental conditions than photosynthetic substrate availability, as the Q10 was lower in leaves that developed at high CO2, irrespective of substrate availability. However, the temperature sensitivity of belowground respiration, calculated between periods of differing air temperature, appeared to be positively correlated with photosynthetic substrate availability. At the ecosystem level, respiration and photosynthesis were positively correlated but the relationship was affected by temperature; for a given rate of daytime photosynthesis, the rate of respiration the following night was greater at 25 than 20°C. This result suggests that net ecosystem exchange did not acclimate to temperature changes lasting up to 3 weeks. Overall, the results of this study demonstrate that the three respiration terms differ in their dependence on photosynthesis and that, short‐ and medium‐term changes in temperature may affect net carbon storage in terrestrial ecosystems.
Testosterone replacement therapy in male hypogonadism is not associated with increase of endothelin‐1 levels
Authors: Kumanov Philip , Tomova Analia , Kirilov Georgi
Published: July 2006

Differences in endothelin‐1 (ET‐1) blood plasma levels were established between healthy men and women. Little is known about vascular effects of testosterone and the interactions between sex hormones and endothelin. In order to study the relationship between ET‐1 and testosterone in more detail, we have investigated 33 male patients with various forms of hypogonadism (13 with hypergonadotropic hypogonadism and 20 with hypogonadotropic hypogonadism). Fourteen age‐matched healthy males served as controls. The basal ET‐1 levels in patients with hypogonadism (0.96 ± 0.12 fmol/mL) (mean ± SEM) were significantly higher in comparison with the controls (0.44 ± 0.04 fmol/mL), p < 0.01. Fifteen individuals of these patients were studied during the therapy with testosterone depot 250 mg i.m. The ET‐1 levels decreased in this group from 0.99 ± 0.22 to 0.78 ± 0.14 fmol/mL at the third and to 0.76 ± 0.25 fmol/mL at the sixth month of the medication, respectively. The differences were not significant compared with the initial levels, but the concentrations at the sixth month of the treatment were not statistically different in comparison with the ET‐1 levels of the controls. There was no significant difference in lipid data between patients before and during testosterone medication, except for the high‐density lipoprotein cholesterol, which decreased at the third month of the treatment. Our results show that plasma ET‐1 levels in males with hypogonadism are elevated with a tendency to decrease after testosterone administration. The optimum testosterone is not associated with enhanced cardiovascular risk as far as ET‐1 plasma levels and lipids are concerned.
Behavioural trade‐offs between growth and mortality explain evolution of submaximal growth rates
Authors: BIRO PETER A. , ABRAHAMS MARK V. , POST JOHN R. , PARKINSON ERIC A.
Published: July 2006

The importance of body size and growth rate in ecological interactions is widely recognized, and both are frequently used as surrogates for fitness. However, if there are significant costs associated with rapid growth rates then its fitness benefits may be questioned.

In replicated whole‐lake experiments, we show that a domestic strain of rainbow trout (artificially selected for maximum intrinsic growth rate) use productive but risky habitats more than wild trout. Consequently, domestic trout grow faster in all situations, experience greater survival in the absence of predators, but have lower survival in the presence of predators. Therefore, rapid growth rates are selected against due to increased foraging effort (or conversely, lower antipredator behaviour) that increases vulnerability to predators. In other words, there is a behaviourally mediated trade‐off between growth and mortality rates.

Whereas rapid growth is beneficial in many ecological interactions, our results show the mortality costs of achieving it are large in the presence of predators, which can help explain the absence of an average phenotype with maximized growth rates in nature.
The potential impact of tourism development on habitat availability and productivity of Malaysian plovers Charadrius peronii
Authors: YASUÉ M. , DEARDEN P.
Published: July 2006

Increased human pressure on coastal habitats has contributed to the global population decline in waders. Although coastal development can be particularly rapid and poorly regulated in tropical countries, very little research has been conducted to assess the extent of these impacts in the tropics.

We examined the potential effects of human disturbance and tourism‐related habitat changes on Malaysian plovers breeding on sandy tropical beaches.

In 2004 and 2005, we monitored 54 and 79 pairs of Malaysian plovers in the Gulf of Thailand, and used logistic habitat models to identify factors influencing habitat selection and breeding success. These models included variables affected by anthropogenic changes such as human disturbance and vegetation structure, as well as other natural factors such as prey availability and predator densities. We also assessed causes of nest failure and conducted 372 h of behavioural observations to identify mechanisms that relate important habitat variables to plover productivity.

Plovers selected wide beaches with low levels of human disturbance that had a low percentage cover of tall trees backing the beach. The likelihood of hatching clutches and fledging chicks was greater in territories with low levels of human disturbance, low conspecific density and high percentage cover of 0·5–5 m tall vegetation backing the beach.

Nest monitoring and behavioural observations suggested that heightened vulnerability to tidal inundation, trampling, heat stress, predators and territorial conflicts may have contributed to the results from the habitat models.

We conclude that tourism development on Thai beaches affects both habitat availability and productivity of Malaysian plovers by enhancing beach erosion rates, converting medium vegetation into tall monocultures and intensifying human disturbance. These direct effects of habitat loss may be exacerbated by density‐dependent reductions in productivity.

Synthesis and application. This study demonstrates the value of combining three approaches: habitat modelling, nest monitoring and behavioural observations, for identifying impacts of anthropogenic changes on breeding birds and assigning ultimate causes. In understudied regions where there are pressing threats to wildlife, this approach may focus research efforts so that the necessary data can be obtained rapidly in order to assess and predict human impacts.
Impacts of restoration treatments on alien plant invasion in Pinus ponderosa forests, Montana, USA
Authors: DODSON ERICH K. , FIEDLER CARL E.
Published: July 2006

Invasion by alien plant species represents a challenge to land managers throughout the world as they attempt to restore frequent fire‐adapted ecosystems following decades of fire exclusion. In ponderosa pine Pinus ponderosa forests of western North America, the response of alien species to restoration treatments has not been well documented, particularly for alien species capable of altering environmental conditions (transformers). Understanding alien species dynamics is critical for developing treatments that accomplish restoration goals while minimizing alien invasion.

We used a replicated, randomized block experiment to compare the effects of an untreated control and thin‐only, burn‐only and thin‐burn treatments on alien and transformer understorey species at multiple spatial scales (1 m2, 100 m2 and 1000 m2). Data were collected pre‐treatment and for multiple post‐treatment years. We compared richness and cover of alien species and transformer species among treatments, and identified environmental variables correlated with transformer species cover. Indicator species analysis was used to identify transformer species associated with specific treatments.

Alien and transformer species richness and cover were significantly higher in the thin‐burn than in all other treatments at all spatial scales. Thin‐only and burn‐only treatments showed greater alien and transformer species responses than the control at the larger 100‐m2 and 1000‐m2 scales.

Increased transformer cover was strongly correlated with increased tree crown scorch height and removal of overstorey trees.

The thin‐burn treatment had four transformer species as indicators, the thin‐only had one, while the burn‐only and control had none.

Synthesis and applications. The results show that alien species, including transformers, respond to restoration treatments, especially the combined thin‐burn treatment. Therefore monitoring for alien species invasion is an essential component of a restoration programme. Abundance of transformer species increased with increasing disturbance intensity, suggesting that less intense single‐disturbance treatments (burn‐only, thin‐only) or incremental treatments may be preferred in some applications. Where more intense treatments are required to meet management objectives, specific strategies, such as seeding of native species, limiting grazing before and after treatment and harvesting over a protective winter snowpack, may be necessary to limit alien invasion.
Using daily ration models and stable isotope analysis to predict biomass depletion by herbivores
Authors: INGER RICHARD , RUXTON GRAEME D. , NEWTON JASON , COLHOUN KENDREW , MACKIE KERRY , ROBINSON JAMES A. , BEARHOP STUART
Published: July 2006

Food availability is one of the major factors governing the distribution of animals. Because animal numbers can in turn regulate the availability of food, the relationship between the two can be described in terms of resource depletion, which can be difficult to quantify.

We present a novel method utilizing multisource stable isotope mixing models and a daily ration approach to predict the depletion of seagrass (Zostera spp.) by grazing light‐bellied Brent geese Branta bernicla hrota at Strangford Lough, Northern Ireland.

The model successfully predicted the depletion of Zostera spp. over the whole Lough compared with empirically derived estimates of biomass. Further, the model was able to predict biomass depletion over 2 years with different population sizes.

The predicted quantities of Zostera consumed were not in agreement with previous studies, being considerably higher, but this may be explained in terms of the lower energetic value of Zostera at Strangford Lough compared with other sites.

When reparameterized with energetic values from previous studies, the model predictions for Zostera consumption were comparable with estimates derived by standard techniques.

Synthesis and applications. This approach offers a novel, efficient and widely applicable method to investigate the relationship between consumers and their food sources. It may have application in deriving site carrying capacities and in quantifying agricultural damage by consumers.