bluuebunny/crossref_metadata_2025 huggingface dataset:
A multi-agent system architecture for coordination of just-in-time production and
distribution
Authors: DAVIDSSON PAUL , WERNSTEDT FREDRIK
Published: August 2003

A multi-agent system architecture for coordination of just-in-time production and distribution is presented. The problem to solve is twofold: first the right amount of resources at the right time should be produced, then these resources should be distributed to the right consumers. In order to solve the first problem, which is hard when the production and/or distribution time is relatively long, each consumer is equipped with an agent that makes predictions of future needs that it sends to a production agent. The second part of the problem is approached by forming clusters of consumers within which it is possible to redistribute resources fast and at a low cost in order to cope with discrepancies between predicted and actual consumption. Redistribution agents are introduced (one for each cluster) to manage the redistribution of resources. The suggested architecture is evaluated in a case study concerning management of district heating systems. Results from a simulation study show that the suggested approach makes it possible to control the trade-off between quality of service and degree of surplus
production. We also compare the suggested approach to a reference control scheme (approximately corresponding to the current approach to district heating management), and conclude that it is possible to reduce the amount of resources produced while maintaining the quality of service. Finally, we describe a simulation experiment where the relation between the size of the clusters and the quality of service was studied.
Coordination knowledge engineering
Authors: OSSOWSKI SASCHA , OMICINI ANDREA
Published: August 2003

By adopting a structured knowledge-level approach, coordination knowledge can be ascribed to groups (societies) of system components (agents) as a whole,
rather than to individuals, in order to effectively rationalise complex patterns of interaction within intelligent (multi-agent) systems. Be it either explicitly represented at the symbol-level or hard-coded within specific coordination algorithms, coordination knowledge is instrumented by a wide and heterogeneous variety of coordination models, abstractions and technologies. Coordination knowledge engineering is then about eliciting, modelling and instrumenting coordination knowledge in a principled and effective manner.

In this introductory article, we briefly review two well-known frameworks to conceptualise coordination, then we discuss different dimensions along which coordination models can be classified, and
analyse their impact on the design of coordination mechanisms and their supporting coordination knowledge. Finally, we sketch our view on coordination knowledge engineering and introduce the different contributions to this special issue along this line.
Becoming a Scientist: Gender and Knowledge in Eighteenth-Century Italy
Authors: Findlen Paula
Published: August 2003

Argument

This essay explores how and why women involved themselves in the sciences in eighteenth-century Italy. Using the case study of Diamante Medaglia Faini, a poet who attempted to become a mathematician, it argues that the image of the woman natural philosopher was shaped by the visible presence of woman in scientific institutions in the mid-eighteenth century and by the tradition of popular scientific writing, best embodied in the works of Bernard le Bovier de Fontenelle and Francesco Algarotti, that made the woman natural philosopher an important literary protagonist. Becoming a scientist, in other words, was both a reality and a fiction. The tensions between these two different images shaped the terrain in which women pursued science.
Harmonious Investigators of Nature: Music and the Persona of the German Naturforscher in the Nineteenth Century
Authors: Jackson Myles
Published: August 2003

Argument

During the early nineteenth century, the German Association of Investigators of Nature and Physicians (Versammlung Deutscher Naturforscher und Ärzte) drew upon the cultural resource of choral-society songs as a way to promote male camaraderie and intellectual collaboration. Investigators of nature and physicians wished to forge a unified, scientific identity in the absence of a national one, and music played a critical role in its establishment. During the 1820s and 30s, Liedertafel and folk songs formed a crucial component of their annual meetings. The lyrics of these tunes, whose melodies were famous folk songs, were rewritten to reflect the lives of investigators of nature and physicians. Indeed, the singing of these Liedertafel songs played an important part in the cultivation of the Naturforschers’ persona well into the twentieth century.
Computational high frequency wave propagation
Authors: Engquist Björn , Runborg Olof
Published: August 2003

Numerical simulation of high frequency acoustic, elastic or electro-magnetic wave propagation is important in many applications. Recently the traditional techniques of ray tracing based on geometrical optics have been augmented by numerical procedures based on partial differential equations. Direct simulations of solutions to the eikonal equation have been used in seismology, and lately approximations of the Liouville or Vlasov equation formulations of geometrical optics have generated impressive results. There are basically two techniques that follow from this latter approach: one is wave front methods and the other moment methods. We shall develop these methods in some detail after a brief review of more traditional algorithms for simulating high frequency wave propagation.
Model reduction methods based on Krylov subspaces
Authors: Freund Roland W.
Published: August 2003

In recent years, reduced-order modelling techniques based on Krylov-subspace iterations, especially the Lanczos algorithm and the Arnoldi process, have become popular tools for tackling the large-scale time-invariant linear dynamical systems that arise in the simulation of electronic circuits. This paper reviews the main ideas of reduced-order modelling techniques based on Krylov subspaces and describes some applications of reduced-order modelling in circuit simulation.
Magnetic impulse events and related Pc1 bursts observed by the Automatic Geophysical Observatories network in Antarctica
Authors: Sato Mitsuteru , Fukunishi Hiroshi , Lanzerotti Louis J. , Maclennan Carol G.
Published: August 2003

Magnetic field data obtained by fluxgate and search coil magnetometers installed at four Automatic Geophysical Observatories (AGO Pl, P2, P3, and P4) and at South Pole and McMurdo in Antarctica and at Iqaluit on Baffin Island are used to study the relationship between magnetic impulse events (MIEs) and Pc1 bursts at high geomagnetic latitudes. The spatial scale sizes of MIEs are determined in the investigation of the sources of these events in the magnetosphere. Four MIE events with simultaneous Pc1 bursts are studied. Contour plots of MIE amplitudes show the scale sizes of the examined MIEs to be 5° to 7° in the magnetic latitude direction and 40° to 60° in the magnetic longitude direction. Temporal changes of the ionospheric currents calculated from the fluxgate H‐ and D‐component data indicate that the “convection vortices” associated with the MIEs traveled westward and decayed rapidly. An important finding is that MIE‐related Pc1 bursts were observed at higher‐latitude (Pl, P4 near 80°) and lower‐latitude (P2, P3 near 70°) AGO stations and South Pole Station at 74° with different spectral structures, although the Pc1 spectral power was always a maximum at South Pole Station. These results imply that Pc1 bursts are excited not only in the dayside outer magnetosphere but also in the low‐latitude boundary layer region.
Effects of solar activity variations on adiabatic heating and cooling effects in the nighttime equatorial topside ionosphere
Authors: Venkatraman Sarita , Heelis Rod
Published: August 2003

Data from the Defense Meteorological Satellite Program are used to examine solar activity variations in ion temperature measured near 800 km altitude across the nighttime equatorial ionosphere. Evidence for ion cooling and heating by adiabatic expansion and compression are seen during high and moderate solar activity conditions. It is found that these effects are strongly dependent on the location of the O+/H+ transition height. During high solar activity a high transition height moves the region of maximum cooling at the dip equator well above 800 km. The region of maximum heating, however, appears in the winter hemisphere near 800 km, where strong longitude variability is seen, owing to the effects of F region neutral winds. During moderate solar activity conditions the transition height is lowered, bringing the region of maximum cooling closer to 800 km altitude. However, the cooling process is not as strong as that seen during high solar activity periods. The heating effects are also lowered during moderate solar activity periods. At 800 km altitude, only relatively small temperature peaks are seen in the winter hemisphere, closer to the dip equator than those seen during high solar activity periods.
Electron beam formation by small‐scale oblique inertial Alfvén waves
Authors: Clark A. E. , Seyler C. E.
Published: August 2003

Particle‐in‐cell simulations reveal characteristics of small‐scale nearly perpendicular nonlinear inertial Alfvén waves in the electrostatic limit, during wave steepening and electron beam generation. These electrostatic inertial Alfvén waves (ESIAW) propagate with only weak electron Landau damping for Ti/Te ≫ 1. Nonlinear amplitude initial conditions convectively steepen and evolve higher wavenumber structures similar in morphology and magnitude to previous results from a fluid‐kinetic model. Shorter wavelength acoustic waves emergent during steepened ESIAW wave evolution are found to be instrumental in exciting cold electron beams possessing kinetic energies a few hundred times that of the thermal electron population. This mechanism is one possible explanation for suprathermal electron bursts observed in and near auroral inverted‐V events.
Climate‐biosphere interactions on glacial‐interglacial timescales
Authors: Bender Michael
Published: August 2003

Potential positive feedbacks of the biosphere on glacial‐interglacial climate change have been extensively investigated in recent years. In this paper, we summarize these feedbacks and the evidence that they may play a quantitatively significant role. We then attempt to assess the role of biosphere feedbacks in glacial/interglacial climate change by evaluating five lines of empirical evidence: (1) synchroneity of warming during the last glacial termination (expected if the biosphere is important, because of short response times); (2) changes in the δ18O of O2, which may reflect the relative fertility of the land and ocean biospheres, (3) changes in the triple isotope composition of O2, which constrain global rates of photosynthesis in the past; (4) the relationship between atmospheric CO2 and dust accumulation at Vostok, and (5) indications for the occurrence or absence of Pleistocene‐style glacial cycles before the evolution of the land biosphere. The evidence is compatible with a significant role for the biosphere in driving glacial‐interglacial change, but unambiguous empirical support is not yet in hand.
Nature and distribution of dykes and related melt migration structures in the mantle section of the Oman ophiolite
Authors: Python Marie , Ceuleneer Georges
Published: August 2003

We conducted a comprehensive field, petrographic, and microprobe study of the dykes and porous flow channels cropping out in the Oman harzburgites. The 36 rock types we recognized among of about 1000 samples can be grouped in two main magma suites contrasted in terms of structural and textural characteristics, modal composition, order of crystallization, and phase chemistry. One suite (troctolites, olivine gabbros, opx‐poor gabbronorites, and rare oxyde gabbros) derives from MORB‐like melts. The other suite (pyroxenites, opx‐rich gabbronorites, diorites, and tonalite‐trondhjemites) derives from melts richer in silica and water than MORBs and ultradepleted in incompatible elements. Dykes and porous flow channels from the MORB suite are restricted to a few areas, covering only 25% of the mantle section. This is an unexpected result as the deep Oman crust is made essentially of cumulates from MORB‐like melts. Their composition, texture, and relations with the host harzburgites point to high mantle temperatures at the time of crystallization (likely above 1100°C, up to 1200°C for part of them), i.e., conditions close to the “asthenosphere/lithosphere” boundary. The largest outcrop of mantle harzburgites enclosing MORB like dykes is a 80 km long and 10 km wide corridor, parallel to the strike of the sheeted dyke complex and centered on an area where a former mantle upwelling has been unambiguously defined (the Maqsad “diapir”). A few other occurrences of mantle cumulates from the MORB suite are smaller than the Maqsad area and have a lesser abundance of troctolites (i.e., of high‐temperature cumulates). We interpret the troctolite zones of Oman as the witnesses of former diapirs frozen at various stages of their development. Dykes belonging to the depleted suite are the most common in Oman harzburgites. Their structural and textural characteristics show that they crystallized in a mantle colder than the melt (likely in the range 600°C to 1100°C). A possible origin for the parent melts of this suite is in situ partial melting of the shallow and partly hydrated lithosphere residual after MORB extraction. Our data support the view that feeding magma chambers with MORBs is a focused (and likely episodic) process involving the rise of hot mantle to the base of the crust through a lithospheric lid accreted during a previous diapiric event. They suggest also that the shallow mantle beneath spreading centers is a place of important petrologic processes, some of them predicted on the basis of MORB composition (e.g., fractionation inside melt conduits) and other ones unexpected (e.g., remelting of the depleted lithosphere).
Long waves induced by short‐wave groups over a sloping bottom
Authors: Janssen T. T. , Battjes J. A. , van Dongeren A. R.
Published: August 2003

The cross‐shore propagation of group‐bound long waves is investigated. A detailed laboratory data set from Boers [1996] is analyzed using primarily the cross‐correlation function for a sequence of closely spaced cross‐shore locations, thus visualizing the propagation of the short‐wave envelope and attendant low‐frequency motion in detail. The results confirm the previously observed lag of the forced subharmonics behind the short‐wave envelope that increases with decreasing water depth. The forced subharmonics are found to be released and reflected at the shoreline and to propagate in offshore direction as free waves. A theoretical, linear model for the forced wave evolution accurate to first order in the relative bottom slope is presented; it predicts a bottom‐slope induced, spatially varying phase shift between the short‐wave envelope and forced waves which is in good agreement with the observations. The phase shift has dynamical consequences since it allows energy transfer between the short‐wave groups and the forced low‐frequency response.
Estimating the distribution of terrestrial CO2 sources and sinks from atmospheric measurements: Sensitivity to configuration of the observation network
Authors: Suntharalingam P. , Spivakovsky C. M. , Logan J. A. , McElroy M. B.
Published: August 2003

We explore the sensitivity of terrestrial CO2 flux estimates from a specific inversion methodology, based on the configuration of Fan et al. [1998], to different configurations of the global observation network. Using diagnostics derived from the inversion equations, we focus on quantifying the relative influence of individual stations on the flux estimates. We also examine the impact of different assumptions for the data uncertainty values by contrasting weighted and unweighted inversions and presenting related sensitivity analyses. For this particular methodology, unweighted estimates of continental scale fluxes prove very sensitive to network configuration. The inclusion or omission of a few important stations in and around the northern continents can result in shifts in continental‐scale flux estimates of up to 1.5 Gt C/year. The weighted estimates are less sensitive to network configuration. Diagnostics of relative station influence indicate that this results from the reduced roles of previously influential continental sites; i.e., those stations characterized by high levels of data uncertainty. In the weighted approach, stations on continental peripheries associated with lower levels of data uncertainty are the most important in determining terrestrial fluxes. Finally, using the diagnostics of relative station influence, we discuss potential sampling strategies for the determination of regional fluxes from surface measurements.
Modeling the radiative impact of mineral dust during the Saharan Dust Experiment (SHADE) campaign
Authors: Myhre Gunnar , Grini Alf , Haywood James M. , Stordal Frode , Chatenet Bernadette , Tanré Didier , Sundet Jostein K. , Isaksen Ivar S. A.
Published: August 2003

The Oslo chemical transport model (Oslo CTM2) is driven by meteorological data to model mineral dust during the Saharan Dust Experiment (SHADE) campaign in September 2000. Model calculations of the optical properties and radiative transfer codes are used to assess the direct radiative impact in the solar and terrestrial regions of the spectrum. The model calculations are compared to a wide range of measurements (satellite, ground‐based, and aircraft) during the campaign. The model reproduces the main features during the SHADE campaign, including a large mineral dust storm. The optical properties and the vertical profiles are in reasonable agreement with the measurements. There is a very good agreement between the modeled radiative impact and observations. The strongest local solar radiative impact we model is around −115 Wm−2. On a global scale the radiative effect of mineral dust from Sahara exerts a significant negative net radiative effect.
Late Holocene productivity and hydrographic variability in the eastern Mediterranean inferred from benthic foraminiferal stable isotopes
Authors: Schilman Bettina , Almogi‐Labin Ahuva , Bar‐Matthews Miryam , Luz Boaz
Published: August 2003

The paleoproductivity, paleo‐oxygenation, and paleohydrographic configuration of the southeastern Mediterranean during the late Holocene was reconstructed on the basis of the isotopic composition of the epibenthic Heterolepa floridana, shallow‐endobenthic Uvigerina mediterranea, and the deeper endobenthic Bulimina inflata from two high‐resolution cores GA‐112 (470 m) and GA‐110 (670 m). The Δδ13C between H. floridana and U. mediterranea reveals four intervals of enhanced productivity, from 3.3–2.6, 2.3–1.9, 1.5–1.1, and 0.8–0.4 kyr BP, coinciding with increased nutrient supply by the Nile River. The entire basin was well aerated, with oxygen consumption varying between 1.0 and 3.5 mL O2/L. Oxygen consumption increases toward present day, probably because of higher accumulation of total organic carbon at 1.7 kyr BP, coinciding with the appearance of the mesotropic benthic species. The hydrographic configuration of the basin has changed during the course of the last 3.75 kyr. The Levantine Intermediate Water (LIW) deepens below 470 m between 3.3 and 2.0 kyr, and especially between 2.5 and 2.0 kyr. During the last 1.5 kyr, the LIW becomes shallower than 470 m, similar to the present day. The change in the hydrographic configuration reflects changes in evaporation/precipitation ratio and in temperature.
Geochemical and transport properties of dissolved organic carbon in a clay‐rich aquitard
Authors: Hendry M. Jim , Ranville J. R. , Boldt‐Leppin B. E. J. , Wassenaar L. I.
Published: August 2003

The properties and controls on the diffusive transport of dissolved organic carbon (DOC) in a thick clay‐rich till aquitard were investigated. DOC was measured in 14 piezometers ranging in depth from 1.2 to 43 m below ground (BG). The DOC data showed a decrease in concentration with depth from 168 mg/L in the surficial, fractured, and oxidized zone (1.2 m BG) through the thick underlying unoxidized and nonfractured aquitard, reaching minimum values of between 12 and 16 mg/L below 15 m. Flow field‐field flow fractionation analyses showed that the DOC was uniform with respect to hydrodynamic size (2.5 nm), molecular weight (approximately 900 Da), and aqueous diffusion coefficient (1.9 × 10−10 m2/s). Specific UV aborbance (UV/TOC) varied with depth but was significantly lower than surface water DOC. Results of batch experiments showed that DOC exhibited negligible sorption (i.e., kd = 1.1 × 10−3 mL/g) to the aquitard matrix. Double‐reservoir diffusion tests showed that DOC diffuses through this clay‐rich media. Results of best fit numerical modeling of the diffusion cell data yielded an effective diffusion coefficient of 9 × 10−11 m2/s for the DOC and suggested that the effective porosity for the DOC may be approximated by the total porosity. Pore aperture measurements on core samples and the results of the diffusion cell experiments revealed that straining of DOC by the aquitard matrix does not occur. Overall, our results suggested that DOC can diffuse through clay‐rich aquitards in a similar manner to conservative inorganic solutes.
Eddies advected by time‐dependent Sverdrup circulation in the western boundary of the subarctic North Pacific
Authors: Isoguchi Osamu , Kawamura Hiroshi
Published: August 2003

It has been reported that several eddies frequently exist along the Kuril‐Kamchatka Trench (K‐K Trench, hereafter), the western boundary of the subarctic North Pacific. Lagged correlation maps of the altimeter‐derived sea level anomalies (SLAs) along the trench indicate that the southern eddies on the whole move northeastward along the K‐K Trench and the northern eddies, on the other hand, move southwestward. By tracking each anticyclonic eddy, its propagating velocity along the trench is calculated. The time series of the tracked 7 eddies shows similar seasonal variation to those of the first empirical orthogonal function (EOF) of the SLA maps and to those of the Sverdrup transport at 40°N. In addition, when more than two eddies remotely exist in the studied area, they show coherent moving patterns. These results suggest that the eddies in the western boundary region of the subarctic North Pacific are advected by the time‐dependent wind‐driven current.
Mother‐to‐infant transmission of SIV via breast‐feeding in rhesus macaques
Authors: Amedee A.M. , Lacour N. , Ratterree M.
Published: August 2003

Abstract: To decipher the mechanisms involved in oral transmission of human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) through breast‐feeding, we have developed an animal model using SIV‐infected lactating rhesus macaques (Macaca mulatta) and their infants. Five of eight macaque infants became infected during a 10‐month study course after SIV inoculation of lactating dams. In a second study, three of four chronically infected female macaques transmitted virus to their infants through breast‐feeding within 4 months of birth. Transmission of virus to infants did not correlate with viral loads in either milk or plasma. Infants were infected with homogeneous virus populations, while milk samples near the time of transmission were more diverse. These studies suggest that specific viral phenotypes are selectively transmitted through breast‐feeding.
Transient early post‐inoculation anti‐retroviral treatment facilitates controlled infection with sparing of CD4+ T cells in gut‐associated lymphoid tissues in SIVmac239‐infected rhesus macaques, but not resistance to rechallenge
Authors: Lifson J.D. , Piatak M. , Cline A.N. , Rossio J.L. , Purcell J. , Pandrea I. , Bischofberger N. , Blanchard J. , Veazey R.S.
Published: August 2003

Abstract: Like human immunodeficiency virus infection of humans, infection of rhesus macaques with pathogenic simian immunodeficiency virus (SIV) strains typically results in persistent progressive infection, leading to clinically significant immunosuppression. In previous studies, we administered short term anti‐retroviral treatment, shortly after intravenous inoculation with SIVsmE660, in an effort to allow immunologic sensitization under conditions not characterized by overwhelming cytopathic infection compromising the developing immune response. We showed that such treatment allowed control of off treatment viremia and was associated with resistance to rechallenge. Control of off treatment viremia was associated, at least in part, with CD8+ lymphocytes, based on in vivo CD8 depletion studies. In the present study, six rhesus macaques were infected intravenously with 100 MID(50) of SIVmac239; four then received 30 days of treatment with tenofovir 9‐[2‐(R)‐(phosphonomethoxy)propyl]adenine (PMPA); 20–30 mg/kg, subcutaneously) starting 24 hours post‐inoculation. Tenofovir‐treated animals showed low (<500 copy Eq/ml) or undetectable (<100 copy Eq/ml) plasma SIV RNA levels during treatment, with undetectable plasma viremia following discontinuation of treatment. Plasma SIV RNA remained <100 copy Eq/ml, even after depletion of CD8+ lymphocytes, 6 weeks after discontinuation of tenofovir treatment. In contrast to untreated infected control animals that showed substantial depletion of CD4+ T cells from gut‐associated lymphoid tissues (GALT), tenofovir‐treated animals showed sparing of GALT CD4+ T cells both during the treatment period and in the off treatment follow‐up period. However, in contrast to earlier results with animals infected with SIVsmE660, in the present study, the animals did not develop readily measurable cellular anti‐SIV immune responses, and did not resist homologous rechallenge with SIVmac239, administered 44 weeks after the initial infection. Differences in the animals and virus strains employed may in part account for the differences in results observed. Comparative analysis of virologic and immunologic parameters in this model system may provide important insights for understanding the basis of effective immunologic control of SIV infection.
Comparison of virology and immunology in SHIV 89.6 proviral DNA and virus‐inoculated rhesus macaques
Authors: Busch Marc , Lu Ding , Fritts Linda , Lifson Jeff D , Miller Christopher J
Published: August 2003

Abstract: Inoculation of cats, goats and monkeys with plasmids encoding full‐length proviral genomes results in persistent lentiviral infections. This system could be used as a method for administration of an attenuated human immunodeficiency virus (HIV) vaccine. Here, we compare the virology and immunology in rhesus macaques inoculated with either simian/human immunodeficiency virus 89.6 (SHIV 89.6) virus or a plasmid containing the SHIV 89.6 proviral genome. There was a delay in appearance of systemic infection in DNA‐inoculated animals compared with virus‐inoculated animals, but otherwise the pattern of infection was similar. The serum immunoglobulin G anti‐simian immunodeficiency virus (SIV) binding antibody response in DNA‐inoculated animals was also delayed compared with virus‐inoculated animals, but ultimately there was no difference between live virus and DNA‐inoculation in the ability to induce the anti‐SIV immune responses that were measured. Thus, the data support the concept that plasmid DNA encoding an attenuated virus could be used instead live virus for vaccination.
Nest predation in forest birds: influence of predator type and predator's habitat quality
Authors: Martin Jean‐Louis , Joron Mathieu
Published: August 2003

We used the introduction of a generalist nest predator, the red squirrelTamiasciurus hudsonicus,and of a large herbivore, the Sitka black‐tailed deerOdocoileus hemionus sitkensis,to the islands of Haida Gwaii (Queen Charlotte Islands, British Columbia, Canada) to study how predator assemblage and habitat quality and structure influenced nest predation in forest birds. We compared losses of natural nests to predators on islands with and without squirrels. We selected nine islands with or without squirrel or deer and used 506 artificial nests put on the ground or in shrubs to further analyse variation of nest predation with predator assemblage and habitat quality for the predators. For both natural and artificial nests predation risk was higher in presence of squirrels. But predation risk varied within island categories. In presence of squirrels it was highest in stands with mature conifers where it fluctuated from year to year, in response to fluctuations in squirrel abundance. Vegetation cover around the nest had little effect on nest predation by squirrels. Where squirrels were absent, nest predation concentrated near predictable food sources for corvids, the main native predators, and increased with decreasing vegetation cover, suggesting that removal of the vegetation by deer increased the risk of predation by native avian nest predators that use visual cues. Predation risk in these forests therefore varies in space and time with predator composition and with quality of the habitat from the predators’ perspective. This temporal and spatial variation in predation risk should promote trade‐offs in the response of birds to nest predation, rather than fine‐tuned adaptations to a given predation pattern.
Ecological dynamics of extinct species in empty habitat networks. 2. The role of host plant dynamics
Authors: León‐Cortés Jorge L. , Lennon Jack J. , Thomas Chris D.
Published: August 2003

This paper explores the relative effects of host plant dynamics and butterfly‐related parameters on butterfly persistence. It considers an empty habitat network where a rare butterfly (Cupido minimus) became extinct in 1939 in part of its historical range in north Wales, UK. Surviving populations of the butterfly in southern Britain were visited to assess use of its host plant (Anthyllis vulneraria) in order to calibrate habitat suitability and carrying capacity in the empty network in north Wales. These data were used to deduce that only a portion (∼19%) of the host plant network from north Wales was likely to be highly suitable for oviposition. Nonetheless, roughly 65,460 eggs (3273 adult equivalents) could be expected to be laid in north Wales, were the empty network to be populated at the same levels as observed on comparable plants in surviving populations elsewhere. Simulated metapopulations of C. minimus in the empty network revealed that time to extinction and patch occupancy were significantly influenced by carrying capacity, butterfly mean dispersal distance and environmental stochasticity, although for most reasonable parameter values, the model system persisted. Simulation outputs differed greatly when host plant dynamics was incorporated into the modelled butterfly dynamics. Cupido minimus usually went extinct when host plant were at low densities. In these simulations host plant dynamics appeared to be the most important determinant of the butterfly's regional extirpation. Modelling the outcome of a reintroduction programme to C. minimus variation at high quality locations, revealed that 65% of systems survived at least 100 years. Given the current amount of resources of the north Wales landscape, the persistence of C. minimus under a realistic reintroduction programme has a good chance of being successful, if carried out in conjunction with a host plant management programme.
What kind of spatial and temporal details are required in models of heterogeneous systems?
Authors: Strayer David L. , Ewing Holly A. , Bigelow Seth
Published: August 2003

Spatial and temporal heterogeneity can make ecological systems hard to understand and model. We propose a simple classification of the types of spatial and temporal complexity contained in ecological systems, and describe the kinds of data and models needed to account for each. We classify ecological systems by the presence of heterogeneity at the scale of study, the nature of their dynamics (linear vs non‐linear), attributes of the patches that constitute the heterogeneous system, and the presence and directionality of interactions among patches. Heterogeneity in space and time are nearly equivalent in our framework. Advanced modeling skills are necessary to create appropriate mathematical representations of highly complex systems (with non‐linear dynamics, patches with more than one kind of important attribute, or interactive patches). Simple models can work well when the scale of heterogeneity is much finer than the scale of observation, when low precision is sufficient, when patches interact only weakly, or when empirical approaches are used to fit functions and constants. Having a way to classify complexity in space and time in ecological systems should help ecologists to select modeling approaches consistent with their abilities and goals.
Constrained by available raptor hosts and islands: density‐dependent reproductive success in red‐breasted geese
Authors: Prop Jouke , Quinn John L.
Published: August 2003

In this paper we aim to explain the distribution of red‐breasted geeseBranta ruficollisover different nesting habitats. To be safe from land predators red‐breasted goose colonies were restricted to i) islands on rivers, ii) cliffs with peregrine falconsFalco peregrinus, and iii) the close proximity of snowy owlNyctea scandiacaand rough‐legged buzzardButeo lagopusnests. Among years nest site availability varied by fluctuations in numbers of owls and buzzards in association with cycles in lemming abundance, but the total number of goose nests found in the study area did not vary. The distribution of geese, in combination with data on reproductive success, suggested a despotic mechanism: at cliffs, goose numbers were constant among years with an invariably high reproductive success, whereas large fluctuations in numbers on islands coincided with opposite trends in success. Apparently, geese nesting with owls or buzzards moved to the few islands present in the study area during years when these birds of prey were absent. Consequently, in such years the average density of geese on islands was more than twice as high as at cliff colonies (5.4 and 2.3 pairs per ha of foraging habitat, respectively). Colony size at cliffs may have been restricted by territorial behaviour of the geese, though there is evidence that, additionally, the host falcons also limited the number of nesting geese. Apparently rare in closely related species, we observed a negative density‐dependent effect on reproductive success during the nest phase, and attribute this to limited food resources, reinforced by the high frequency of territorial interactions. This leads to the conclusion that, in addition to predation pressure, nesting density is an important agent in the link between lemming cycles and goose breeding success.
Finding habitat patches and directional connectivity
Authors: Schooley Robert L. , Wiens John A.
Published: August 2003

For animal species inhabiting patchy environments, the search behavior of individuals and the distance from which they can detect suitable habitat (perceptual range) are key determinants of the functional connectivity of landscapes. We examined the movement behavior and perceptual range of adult cactus bugs (Chelinidea vittiger), which are habitat specialists that feed and reproduce onOpuntiacactus. Movement pathways of walking individuals released into unsuitable matrix habitat (30–3000 m fromOpuntia) were highly directional. These results supported predictions of optimal search behavior from published simulation models. A release experiment within natural patch networks indicated that the perceptual range ofC. vittigerdepended on size of the target patch, matrix structure, and direction of the target patch relative to prevailing winds. A strong effect of wind direction on orientation behavior (and presumed perceptual range) was evident in a release experiment using ‘artificial’ patches of pottedOpuntia. In these two experiments, individuals released 50–100 cm fromOpuntiapatches were more likely to orientate toward patches located upwind than to those located crosswind or downwind. A reexamination of the pathways of individuals walking in the matrix also revealed a strong bias for movement upwind. Such upwind movement by individuals, both within and outside of patch networks, suggests thatC. vittigeruses olfaction to navigate and it complicates our ability to interpret search behavior and to estimate perceptual range. Current techniques for assessing perceptual range have limitations for olfactory‐based species. Furthermore, we need to broaden our view of perceptual range and of patch and landscape connectivity. Perceptual range may be anisotropic and connectivity may be directional. An organism‐based approach to spatial ecology requires that we consider the dominant senses used by species when navigating around patchy landscapes.
The influence of larval density, food availability and habitat longevity on the life history and population growth rate of the midge Chironomus riparius
Authors: Hooper Helen L. , Sibly Richard M. , Hutchinson Thomas H. , Maund Steve J.
Published: August 2003

Despite long‐standing interest in the forms and mechanisms of density dependence, these are still imperfectly understood. However, in a constant environment an increase in density must reduce per capita resource availability, which in turn leads to reduced survival, fecundity and somatic growth rate. Here we report two population experiments examining the density dependent responses under controlled conditions of an important indicator species, Chironomus riparius.

The first experiment was run for 35 weeks and was started at low density with replicate populations being fed three different rations. Increased ration reduced generation time and increased population growth rate (pgr) but had no effect on survival, fecundity and female body weight in the first generation. In the second generation there was a six‐fold increase in generation time, presumably due to the greatly reduced per capita resource availability as the estimated initial densities of the second generation were 300 times greater than the first. Juvenile survival to emergence, fecundity, adult body weight and pgr declined by 90%, 75%, 35% and 99%, respectively. These large between‐generation effects may have obscured the effects of the threefold variation in ration, as only survival to emergence significantly increased with ration in the second generation.

These results suggest that some chironomid larvae survive a reduction in resource availability by growing more slowly. In the ephemeral habitats sometimes occupied by C. riparius, the effects of population density may depend crucially on the longevity of the environment. A second experiment was therefore performed to measure pgr from six different starting densities over an eight‐week period. The relationship between pgr and density was concave, viewed from above. At densities above 16 larvae per cm2, less than 1% of the population emerged and no offspring were produced. Under the conditions of experiment 2 – an 8‐week habitat lifespan – carrying capacity was estimated as 8 larvae per cm2.
Quadruple therapy containing amoxicillin and tetracycline is an effective regimen to rescue failed triple therapy by overcoming the antimicrobial resistance of Helicobacter pylori
Authors: Chi C.‐H. , Lin C.‐Y. , Sheu B.‐S. , Yang H.‐B. , Huang A.‐H. , Wu J.‐J.
Published: August 2003

Aim : To identify optimal antibiotics for second‐line quadruple therapy of Helicobacter pylori after failed 1‐week triple therapy.

Methods : One hundred patients were enrolled in this study after the failure of 1‐week triple therapy. They were randomized to receive 1‐week quadruple therapy consisting of amoxicillin, omeprazole and bismuth salts, plus either metronidazole or tetracycline. Before quadruple therapy, the H. pylori culture of each patient was tested for metronidazole resistance or clarithromycin resistance by E‐test. Six weeks later, an endoscopy or 13C‐urea breath test was used to define the success of H. pylori eradication.

Results : The H. pylori eradication rates by intention‐to‐treat and per protocol analysis were higher in the tetracycline group than in the metronidazole group (intention‐to‐treat: 78% vs. 58%, P < 0.05; per protocol: 89% vs. 67%, P < 0.05). In the metronidazole group, but not in the tetracycline group, the per protocol eradication rate of quadruple therapy was lower for the infected isolates with metronidazole resistance than for those without metronidazole resistance (77% vs. 33%, P < 0.05).

Conclusion : Quadruple therapy, including tetracycline and amoxicillin, improves the H. pylori eradication rate after failed triple therapy.
Contemporary understanding and management of reflux and constipation in the general population and pregnancy: a consensus meeting
Authors: Tytgat G. N. , Heading R. C. , Müller‐Lissner S. , Kamm M. A. , Schölmerich J. , Berstad A. , Fried M. , Chaussade S. , Jewell D. , Briggs A.
Published: August 2003

Background : Gastro‐oesophageal reflux disease (GERD) and constipation have a major impact on public health; however, the wide variety of treatment options presents difficulties for recommending therapy. Lack of definitive guidelines in pharmacy and general practice medicine further exacerbates the decision dilemma.

Aims : To address these issues, a panel of experts discussed the principles and practice of treating GERD and constipation in the general population and in pregnancy, with the aim of developing respective treatment guidelines.

Results : The panel recommended antacids ‘on‐demand’ as the first‐line over‐the‐counter treatment in reflux, and as rescue medication for immediate relief when reflux breaks through with proton pump inhibitors. Calcium/magnesium‐based antacids were recommended as the treatment of choice for pregnant women because of their good safety profile. In constipation, current data do not distinguish a hierarchy between polyethylene glycol (PEG)‐based laxatives and other first‐line treatments, although limitations are associated with stimulant‐ and bulk‐forming laxatives. Where data are available, PEG is superior to lactulose in terms of efficacy. In pregnancy, PEG‐based laxatives meet the criteria for the ideal treatment.

Conclusions : The experts developed algorithms that present healthcare professionals with clear treatment options and management strategies for GERD and constipation in pharmacy and general practice medicine.
Use of the bougie in simulated difficult intubation. 1. Comparison of the single‐use bougie with the fibrescope*
Authors: Hames K. C. , Pandit J. J. , Marfin A. G. , Popat M. T. , Yentis S. M.
Published: August 2003

We studied the success rates for tracheal intubation in 64 healthy patients during simulated grade III laryngoscopy after induction of anaesthesia, using either the single‐use bougie or oral flexible intubating fibrescope, both in conjunction with conventional Macintosh laryngoscopy. Patients were randomly allocated to either simulated grade IIIa or grade IIIb laryngoscopy, and also to one of the two study devices. Success rates for tracheal intubation (primary outcome measure) and times taken to achieve intubation (secondary outcome measure) were recorded. For the simulated grade IIIa laryngoscopy group, the fibreoptic scope was more successful than the bougie (16/16 successful intubations vs. 8/16; p = 0.02). For the simulated grade IIIb laryngoscopy group, the fibreoptic scope was also more successful than the bougie (8/16 successful intubations vs. 1/16; p = 0.02), but clearly use of the fibreoptic scope was not as successful as it had been in simulated grade IIIa laryngoscopy (p = 0.04). With either device, median (range) total tracheal intubation times for successful attempts with either grade of laryngoscopy were less than 60 s (19–109) and there were no clinically important differences. We conclude that the fibrescope used in conjunction with Macintosh laryngoscopy is a more reliable method of tracheal intubation than the single‐use bougie in both types of grade III laryngoscopy. This finding has implications for the management of patients in whom grade III laryngoscopy is encountered unexpectedly after induction of anaesthesia, and also for the management of patients previously known to have grade III view at laryngoscopy.
Effects of hypertonic saline (7.5%) on extracellular fluid volumes in healthy volunteers
Authors: Järvelä K. , Koskinen M. , Kööbi T.
Published: August 2003

This study evaluated the effects of 7.5% saline on plasma and other extracellular fluid volumes. After baseline measurements, eight healthy postmenopausal female volunteers received 4 ml.kg−1 of hypertonic saline over 30 min. After the fluid infusion, the volunteers were studied for 60 min. Plasma volume was measured using a dilution of 125‐iodine‐labelled human albumin. Extracellular water and cardiac output were measured by whole body impedence cardiography. The infused volume was 4 ml.kg−1 (average 260 ml). Plasma volume increased rapidly during the infusion (mean ± standard deviation, 442 ± 167 ml). At the end of the 1‐h follow‐up period, plasma volume had increased by on average 465 ml (SD 83). The increase of extracellular water at the end of infusion and at the end of study was 650 ml (SD 93) and 637 ml (SD 192), respectively. The highest serum sodium recorded in the volunteers was 158 mmol.l−1. The effect of 7.5% saline on plasma volume was rapid and lasted for at least 1 h. Plasma volume remained elevated by more than the infused volume at the end of the study. The increase in plasma and extracellular fluid volumes was partly achieved by mobilizing intracellular water to extracellular compartment.
1000 anaesthetic incidents: experience to date
Authors: James R. Hugh
Published: August 2003

The anaesthetic incident reporting scheme in Leicester has been running for 11 years and 1000 incidents have now been reported. The scheme has successfully highlighted weaknesses where a procedural change has been able to prevent repetition. It has provided advance notification of problems which could be overcome by publicity and has been a source of educational cases. The experience of this scheme supports the use of a definition which does not include blame and allows the possibility of anonymous reporting. The scheme has evolved, driven by hospital decisions on reporting risk management cases, by inclusion of the Royal College of Anaesthetists' incident categories and by progressive refinements. Summary figures are given for the different categories of incident. These show marked similarities with previous studies.
The effect of variable‐dose diazepam on dreaming and emergence phenomena in 400 cases of ketamine‐fentanyl anaesthesia
Authors: Grace R. F.
Published: August 2003

Summary This randomised double‐blind field study compared 400 anaesthetics using diazepam (0, 0.025, 0.5, 0.1, 0.175 mg.kg−1) with ketamine (1 mg.kg−1) and fentanyl (1 µg.kg−1) in Melanesian patients. Dreams were very common and generally positive in nature. A minimum of 0.1 mg.kg−1 of diazepam was needed to significantly reduce dreaming when compared with water (67.5% vs. 94.6%; p < 0.0001), and to significantly lower median (95% CI) emergence delirium scores (4 (3–4) vs. 6 (5–7)). Gender and age did not affect the rate of dreaming. Increasing the dose of diazepam did not improve the dream experience. Patient satisfaction scores were similar between groups. Increases in blood pressure and heart rate were greater in dreamers than in non‐dreamers. All groups had high rate–pressure products but this was highest when diazepam was not used. Higher diazepam doses significantly reduced the increase in blood pressure and heart rate at 3 and 6 min postketamine. When used with ketamine and fentanyl, 0.1 mg.kg−1 of diazepam has favourable psychic and cardiovascular effects. Lower diazepam doses generally had little effect whereas larger doses did not enhance the benefits further.