bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissipation of three organochlorine and four pyrethroid pesticides sprayed in a greenhouse environment during hydroponic cultivation of gerbera
Authors: Hatzilazarou Stefanos P , Charizopoulos Emmanouel T , Papadopoulou‐Mourkidou Euphemia , Economou Athanasios S 
Published: August 2004

AbstractA wide range of pesticides (insecticides, acaricides and fungicides) is used in the hydroponic cultivation of gerbera. The fate and behaviour of some of these commonly used pesticides (organochlorine and pyrethroid insecticides/acaricides) in a greenhouse installation was investigated. The concentrations of endosulfan, dicofol, tetradifon, permethrin, bifenthrin, cypermethrin and deltamethrin in the air of the greenhouse were related to their physicochemical properties and respective application rates. Of these compounds, endosulfan exhibited the highest concentration in the greenhouse air 2 h after application (10 µg m−3), due to its highest volatility; afterwards, up to 12 h post‐application, a rapid decrease was recorded which finally led to a concentration of 0.41 µg m−3 at 6 days post‐application. Dicofol exhibited the same trend of dissipation in the greenhouse air; its concentration decreased from 0.27 µg m−3 immediately after the application to 0.12 µg m−3 at 6 days post‐application. Tetradifon, bifenthrin and permethrin were found at concentrations lower than 0.1 µg m−3 at 2 h post‐application, and cypermethrin and deltamethrin could not be detected. The concentrations of all the above pesticides in the drain water of the open hydroponic system were relatively high immediately after application and decreased rapidly during the following 3 days. In the closed hydroponic system, all the pesticides accumulated in the nutrient solution during the first 24 h after application and slowly decreased in concentration over the following 3 days. The spray operators applying these pesticides were exposed to rather high concentrations and the spray deposits were monitored on the chest and forehead of the operator. Endosulfan exhibited the highest concentrations of the seven pesticides. The organochlorine pesticides (endosulfan, dicofol and tetradifon) were usually detected at higher concentrations on the chest than on the forehead of the operator; pyrethroids were detected at higher concentrations on the forehead than on the chest of the operator. Copyright © 2004 Society of Chemical Industry
Synthesis of chiral α‐amino aldehydes linked by their amine function to solid support
Authors: Cantel Sonia , Heitz Annie , Martinez Jean , Fehrentz Jean‐Alain 
Published: August 2004

AbstractThe anchoring of an α‐amino‐acid derivative by its amine function on to a solid support allows some chemical reactions starting from the carboxylic acid function. This paper describes the preparation of α‐amino aldehydes linked to the support by their amine function. This was performed by reduction with LiAlH4 of the corresponding Weinreb amide linked to the resin. The aldehydes obtained were then involved in Wittig or reductive amination reactions. In addition, the linked Weinreb amide was reacted with methylmagnesium bromide to yield the corresponding ketone. After cleavage from the support, the compounds were obtained in good to excellent yields and characterized. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
The nominal duration of TIPS bonds
Authors: Laatsch Francis E. , Klein Daniel P. 
Published: August 2004

AbstractThis paper studies the price responsiveness (effective duration) of U.S. government issued inflation‐indexed bonds, known by the acronym TIPS (Treasury Inflation‐Protected Securities), to changes in nominal interest rates, real interest rates, and expected inflation. Using the TIPS pricing formula derived by Laatsch and Klein [Q. Rev. Econ. Finance43 (2002) 405], we first confirm that TIPS bonds have zero sensitivity to changes solely in expected inflation. By changes solely in expected inflation, we mean that the real rate remains unchanged and the nominal rate changes in accordance with the established Fisher [Publ. Am. Econ. Assoc.11 (1896)] effect. We show that the first derivative of the TIPS price is zero whenever the real rate is held constant. Thus, the first partial derivative of the TIPS bond pricing formula with respect to expected inflation is zero and the first partial derivative of the TIPS bond price with respect to nominal rates is also zero, given, in each case, that we hold the real rate constant. We then temporarily shift the analysis to zero‐coupon TIPS bonds and zero‐coupon ordinary Treasury bonds. We prove that the nominal duration of zero‐coupon TIPS bonds equals that of zero‐coupon ordinary Treasury bonds when the real rate changes but expected inflation is held constant.However, if expected inflation changes and the change in the nominal rate does not yield a constant real rate, zero‐coupon TIPS prices will change and they will change by a smaller percentage than will zero‐coupon ordinary Treasury bonds. We analyze TIPS responsiveness to changes in nominal rates under such conditions. We derive an approximation to effective duration that demonstrates that the effective durations of various maturity zero‐coupon TIPS bonds are approximately linear functions in time to maturity of the effective duration of the one‐year zero‐coupon TIPS bond, ceteris paribus.Nominal effective duration of TIPS bonds is certainly of interest to fixed income portfolio managers that might have a desire to include such bonds in their portfolio. After all, the greater portion of a typical fixed income portfolio is in traditional, noninflation protected bonds whose major risk exposure is to changes in nominal rates. To properly assess the role of TIPS bonds in the portfolio, portfolio managers need information as to how TIPS bonds respond to the changes in nominal rates that are driving the price behavior of the bulk of the portfolio's assets. Prior to concluding the paper, we demonstrate how portfolio managers can calculate the nominal durations of coupon TIPS bonds using the zero‐coupon duration formula we derive.
Trophic links’ length and slope in the Tuesday Lake food web with species’ body mass and numerical abundance
Authors: REUMAN DANIEL C. , COHEN JOEL E. 
Published: August 2004

Summary
Previously unnoticed patterns emerged in the lengths and slopes of trophic links of the food web of Tuesday Lake, Michigan, USA, when species were plotted on axes of log body mass (vertical) vs. log numerical abundance (horizontal). Link length was defined as equal to the number of orders of magnitude difference in mean body size between predator and prey plus the number of orders of magnitude difference in numerical abundance between predator and prey.
The average length over all trophic links was 6·2 [SD (standard deviation) = 2·8] orders of magnitude in 1984, and 5·8 (SD = 2·6) in 1986. Thus, for the average link, the ratio of the mean body mass of predator to prey, times the ratio of the numerical abundance of prey to predator, was about one million (106 ±). To a first approximation the typical predator was 10 times as long as its prey but 1000 times less numerically abundant. Link length distributions were approximately normal. Mean link lengths in 1984 and 1986 were not statistically different, but were more than an order of magnitude larger than the mean distance between all possible ordered pairs of species in each year. Ordered pairs of species that were between 9 and 11 orders of magnitude apart were the most likely to be links in both years.
The angle of a (non‐cannibalistic) link was defined so that an angle of 135° indicates that the predator was larger than the prey by exactly as many orders of magnitude as the prey was numerically more abundant than the predator, and so that the biomass (mean body mass times numerical abundance) of predator and prey were equal. For all non‐cannibalistic links, the median angle was 132° in 1984 and 129° in 1986. Both of these angles were significantly less than 135°. Angle deviated much from its median value only for short links. When the link was short or had the median angle, the predator species’ biomass was probably greater than that of the prey species.
Several models of food web structure failed to reproduce the observed normal distribution of link lengths. Observed predation matrices with species ordered by body mass had links arranged in blocks suggesting functional groups. Models that incorporated this block structure reproduced the normal link length distribution, but a model that forced a normal link length distribution did not produce blocks. The cascade model explained the median angle of trophic links.
Understanding demography in an advective environment: modelling Calanus finmarchicus in the Norwegian Sea
Authors: SPEIRS DOUGLAS C. , GURNEY WILLIAM S. C. , HOLMES STEVEN J. , HEATH MICHAEL R. , WOOD SIMON N. , CLARKE ELIZABETH D. , HARMS INGO H. , HIRCHE HANS‐JURGEN , McKENZIE EDDIE 
Published: August 2004

Summary
Attempts to understand the demography of natural populations from time‐series can be hampered by the fact that changes due to births and deaths may be confounded with those due to movement in and out of the sampling area.
We illustrate the problem using a stage‐structured time‐series of the marine copepod Calanus finmarchicus sampled in the vicinity of a fixed location but where the demography is shown to be inconsistent with the assumption of a closed population.
By combining a realistic simulation of the hydrodynamic environment with a model of phenology we infer the time and location at which the stages observed in each sample were recruited as eggs. This yields a spatial and temporal map of the recruitment history required to produce the observed densities.
Using an empirical relationship between C. finmarchicus egg production and the abundance of phytoplanktonic food, the spatio‐temporal patterns in chlorophyll a can be inferred. The distributions during the spring bloom are spatially heterogeneous, and we estimate that the phytoplankton patches are of the order of 30 km across. This result is robust to substantial variations in the assumed stage‐dependent mortalities.
We conclude that information on advective transport can be used to make testable predictions about the scale of spatial heterogeneities. These, in turn, imply the appropriate spatial scale over which time‐series might be replicated in order to obtain more information about unknown processes such as mortality.
Individual differences in microhabitat use in a Caribbean cleaning goby: a buffer effect in a marine species?
Authors: WHITEMAN ELIZABETH A. , CÔTÉ ISABELLE M. 
Published: August 2004

Summary
Buffer effects occur when changes in population size result in the disproportionate use of poor‐quality habitats. Thus, at low population sizes high‐quality habitats are used preferentially. As population size increases an increasing proportion of the population uses poorer‐quality habitats. Assessment of the temporal and spatial variation in patterns of habitat occupancy can therefore shed light on the differences in quality between habitats and the individual fitness consequences of habitat choice.
We provide the first evidence of the potential operation of a buffer effect for a site‐attached marine species. Caribbean cleaning gobies Elacatinus prochilos (Böhlke & Robins) occupy coral and sponge on fringing reefs in Barbados. For adult gobies, resource selection indices suggested a preference for sponge. However, as cleaning goby population size increased, the number of adult cleaning gobies occupying sponge increased more rapidly than the number occupying coral. In contrast, adults preferentially re‐colonized coral following experimental removals and at these low population densities the rate of population increase was greater on coral. Our results suggest that coral may be the preferred habitat, but in Barbados this habitat becomes saturated at very low population densities as a consequence of low client densities and ectoparasite loads. Thus, a larger proportion of the population occupies sponge at most observed population densities.
Patterns of habitat occupancy with population size for recruits and juveniles suggest only a small difference in habitat quality between sponge and coral. Indeed, recruits and juveniles do not discriminate between sponge and coral. The population shift towards sponge rather than coral occupancy between recruitment and maturity may arise as a combination of differing survival of recruits and juveniles on coral and sponge and active movement of individuals towards sponge.
Our results demonstrate that interactions among individuals are an integral part of population distribution and dynamics and are therefore important in future studies of habitat choice and its associated fitness consequences.
Determining trophic niche width: a novel approach using stable isotope analysis
Authors: BEARHOP STUART , ADAMS COLIN E. , WALDRON SUSAN , FULLER RICHARD A. , MACLEOD HAZEL 
Published: August 2004

Summary
Although conceptually robust, it has proven difficult to find practical measures of niche width that are simple to obtain, yet provide an adequate descriptor of the ecological position of the population examined.
Trophic niche has proven more tractable than other niche dimensions. However, indices used as a proxy for trophic niche width often suffer from the following difficulties. Such indices rarely lie along a single scale making comparisons between populations or species difficult; have difficulty in combining dietary prey diversity and evenness in an ecologically meaningful way; and fail to integrate diet over ecological time‐scales thus usually only comprise single snapshots of niche width.
We propose an alternative novel method for the comparison of trophic niche width: the use of variance of tissue stable isotope ratios, especially those of nitrogen and carbon.
This approach is a potentially powerful method of measuring trophic niche width, particularly if combined with conventional approaches, because: it provides a single measure on a continuous axis that is common to all species; it integrates information on only assimilated prey over time; the integration period changes with choice of tissue sampled; and data production is theoretically fast and testing among populations simple.
Empirical studies are now required to test the benefits of using isotopic variance as a measure of niche width, and in doing so help refine this approach.
The importance of habitat heterogeneity, biotic interactions and dispersal in abundance–occupancy relationships
Authors: HOLT ALISON R. , WARREN PHILIP H. , GASTON KEVIN J. 
Published: August 2004

Summary
In simple microcosm systems, the form of interspecific abundance–occupancy relationships has been found to be dependent on biotic interactions. However, in more complex systems such effects may be obscured by those of habitat heterogeneity. Here we test this proposal using laboratory microcosms of protists and bacteria.
The independent effects of species interactions and heterogeneity were tested by comparison of the abundance–occupancy relationship formed in multiple habitat patch systems containing all species together, with that relationship formed by combining data from equivalent systems containing each protist species alone and between homogeneous and heterogeneous environments.
There was more residual variation about positive interspecific abundance–occupancy relationships formed in heterogeneous environments in interacting and non‐interacting communities as the majority of species were more restricted in the number of patches they could occupy compared to homogeneous landscapes.
Abundance–occupancy relationships in interacting communities were better defined than those in non‐interacting communities. The inclusion of interspecific interactions caused a reduction in the abundance and occupancy of the majority of species and changed the position of species within the relationship.
Our results show that biotic interactions influence the abundance–occupancy relationships even with imposed environmental heterogeneity. However, in heterogeneous environments, for some species these processes occurred in fewer patches, causing increased residual variation about positive interspecific abundance–occupancy relationships compared to homogeneous environments.
Adaptations of animals to commensal habitats: population dynamics of house mice Mus musculus domesticus on farms
Authors: POCOCK MICHAEL J. O. , SEARLE JEREMY B. , WHITE PIRAN C. L. 
Published: August 2004

Summary
Commensal mammals live in habitats that appear to provide both benefits and costs compared with natural and semi‐natural (non‐commensal) habitats. These commensal habitats offer potentially rich food resources but are also characterized by instability in time and space. We expected to demonstrate that animals in these habitats have high reproductive rates to counter high mortality rates and show flexibility in spatial organization. House mice (Mus musculus domesticus) are unusual because they are able to persist entirely in both commensal and non‐commensal habitats, and so can provide a test of the distinctiveness of commensal populations.
We studied populations of commensal house mice on two neighbouring farms in North Yorkshire, UK, for 2 years by capture–mark–recapture using the robust design. A total of 568 house mice were captured, with a total of 1053 recaptures. Population size varied from nine to 93 individuals, estimated with closed population models. Apparent survival was surprisingly low (0·54 per month) and was best modelled as constant across age, sex and time.
In situ reproductive recruitment occurred throughout the study and was numerically more important than immigration. Immigration was important during only two intervals and was probably from untrappable areas within the study site. Breeding throughout the year allowed the population to persist despite low survival rates. The results suggested that births and deaths had more influence on the overall population dynamics than movement.
The population was divided into subgroups to represent the territorial, demic structure known to be present in commensal house mouse populations. Dispersal between subgroups within the population was limited, representing only 6·6% of recaptures. The low rates of dispersal suggested that house mice responded to their environment as consisting of aggregated patches of suitable habitat.
In comparison, non‐commensal house mice have lower mortality, seasonal breeding, and individuals move more frequently and further than commensal house mice.
These differences illustrate the responses of house mice to the specific opportunities and demands of commensal habitats and demonstrate the importance of a flexible life‐history strategy for animals exploiting these habitats.
Habitat structure mediates the non‐lethal effects of predation on enclosed populations of house mice
Authors: ARTHUR ANTHONY D. , PECH ROGER P. , DICKMAN CHRIS R. 
Published: August 2004

SummaryPrey behavioural changes in response to predation risk can result in significant effects on prey body growth rates and reduced reproductive output, with resultant impacts on prey population dynamics. This paper examines the influence of habitat structure on these non‐lethal impacts of predation using a model, field‐based experimental system, with house mice as prey.Three treatments were employed in eight 50 × 50 m pens that contained mice, but allowed access to a suite of free‐living vertebrate predators, which included feral foxes, feral cats and native raptors: a treatment where the natural grassland vegetation in the pens was maintained at a height < 10 cm; a treatment where small, felled cypress pine trees covered with wire netting were added to low grassland vegetation to create refuge areas covering 10–15% of the area in a pen; and a treatment where predators were excluded from a 25 × 25 m section of some pens with an underlying grassland structure. A 5 × 5 grid of felled trees was added to grassland and predator‐exclusion pens to allow assessment of mouse behaviour.Mice in grassland pens avoided open areas, had lower body growth rates, and began breeding later in spring than mice in both predator‐exclusion areas, where they foraged more readily in the open, and in refuge pens, where mice avoided open areas but had safe access to supplementary food located within the refuge. These results occurred despite mouse population densities being much lower in grassland pens, and presumably competition for food being much less, compared with under the other treatments.The results indicate predators can have significant non‐lethal impacts on prey, and these effects can be mediated by habitat structure.
Individual diet specialization, niche width and population dynamics: implications for trophic polymorphisms
Authors: SVANBÄCK RICHARD , PERSSON LENNART 
Published: August 2004

SummaryWe studied a perchPerca fluviatilisL. population that during a 9‐year period switched between a phase of dominance of adult perch and a phase dominated by juvenile perch driven by cannibalism and intercohort competition. We investigated the effects of these population fluctuations on individual diet specialization and the mechanisms behind this specialization.Due to cannibalism, the survival of young‐of‐the‐year (YOY) perch was much lower when adult perch density was high than when adult perch density was low.Both the individual niche breadth (if weighed for resource encounter) and the population niche breadth were highest when adult population density was high and, consequently, individual specialization was highest at high adult perch densities.When adult perch density was low, the abundances of benthic invertebrate and YOY perch were high and dominated the diet of adult perch, whereas the density of zooplankton was low due to predation from YOY perch. At high perch densities, benthic invertebrate abundance was lower and zooplankton level was higher and some perch switched to feed on zooplankton.Our results show that individual specialization may fluctuate with population density through feedback mechanisms via resource levels. Such fluctuations may have profound implications on the evolution of resource polymorphisms.
Time to extinction in relation to mating system and type of density regulation in populations with two sexes
Authors: SÆTHER BERNT‐ERIK , ENGEN STEINAR , LANDE RUSSELL , MØLLER ANDERS PAPE , BENSCH STAFFAN , HASSELQUIST DENNIS , BEIER JOSEF , LEISLER BERND 
Published: August 2004

Summary
Population viability models usually consider only the female segment of the population. However, random variation in sex ratio as well as the mating system may also affect variation in fitness among females. Here we develop population models incorporating demographic stochasticity in both sexes. Furthermore, we consider the effects on the estimated time to extinction and whether density regulation acts only on females or on total population size.
We applied these models to two populations of polygynous great reed warblers Acrocephalus arundinaceus L. with differences in population trends to investigate the importance of considering sex in population viability models.
Demographic stochasticity was larger in a polygynous than in a monogamous mating system.
The estimated time to extinction was considerably shorter for a monogamous than for a polygynous mating system, particularly if density regulation acted only on females than rather on the total population.
This study demonstrates that structure of mating system must be included when making population viability analysis based on counts of total population sizes. It is especially important to model the specific effects of density regulation on the two sexes.