bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental fluctuations can stabilize food web dynamics by increasing synchrony
Authors: Vasseur David A. , Fox Jeremy W. 
Published: September 2007

AbstractNatural food webs are species‐rich, but classical theory suggests that they should be unstable and extinction‐prone. Asynchronous fluctuations in the densities of competing consumers can stabilize food web dynamics in constant environments. However, environmental fluctuations often synchronize dynamics in nature. Using the same ‘diamond‐shape’ food web model first used to demonstrate the stabilizing effects of asynchrony in constant environments, we show that weak‐to‐moderate environmentally induced fluctuations in consumer mortality rates stabilize food webs while disrupting asynchrony. Synchrony actually promotes stability because: (i) synchronous declines in consumer density reduce the maximum abundance of top predators and (ii) resource competition quickly converts synchronous increases in consumer density into synchronous declines. These results are robust to details of food web topology and the implementation of environmental fluctuations. The fluctuation strengths that enhance stability are within the range experienced naturally by many species, suggesting that stabilization via environmental fluctuations is a realistic possibility.
Thermophilic microbial mats in a tropical geothermal location display pronounced seasonal changes but appear resilient to stochastic disturbance
Authors: Lacap Donnabella C. , Barraquio Wilfredo , Pointing Stephen B. 
Published: September 2007

SummaryWe demonstrate for the first time a dynamic seasonality within thermophilic mat communities in a tropical geothermal spring. Biomass fluctuated such that it is greatest in the dry season, before falling drastically as the summer rains arrive, and then re‐colonization culminates in a new climax in the following dry season. Species richness estimates based upon 16S rRNA gene environmental phylotypes mirrored this pattern, where those unique to the dry season disappear during the wet season only to reappear the following year, and vice versa. Relative abundance of some phototrophic phylotypes was also shown to vary seasonally. Environmental variables within the thermal environment that were most closely correlated to these variations were temperature and phosphate, with the latter a covariable to heavy seasonal tropical monsoon rainfall. Stochastic disturbance caused by a strong typhoon caused significant although temporary effects and both diversity and standing biomass recovered within a few months. Tropical hot spring communities clearly function under a fundamentally different set of abiotic variables from those in temperate locations which do not display seasonality. This is of particular relevance to bioprospecting efforts where targeting the most biodiverse niche is desired, because future sampling strategies for tropical thermal environments should consider diversity on temporal as well as spatial scales.
Childhood obesity: political developments in Europe and related perspectives for future action on prevention
Authors: Fussenegger D. , Pietrobelli A. , Widhalm K. 
Published: September 2007

SummaryThe dramatically increasing prevalence of obesity, especially among children, has become a major public health problem in Europe. In reaction to this alarming trend, a series of initiatives and actions has been launched in recent years. As the potential impact of these activities is widely unknown so far, we underline the need for adequate evaluation of these measures. The aim of this paper is to report the latest developments in the fight against obesity at different political levels across Europe, with special attention to the major results of the recent World Health Organization European Ministerial Conference on Counteracting Obesity. In accordance with the main principles of the European Charter on Counteracting Obesity adopted at the meeting, immediate action should be taken now by implementing the few available schemes with proven effectiveness. Finally, given the lack of appropriate evaluation, we consider it particularly important to establish national research centres to collect country‐specific data that are to be evaluated together by a central European administration department. Based on the results of such a comprehensive data pool, concrete strategies could be developed for future policy building.
The tortoise and the hare enigma in e‐transformation in Japanese and Korean higher education
Authors: Latchem Colin , Jung Insung , Aoki Kumiko , Ozkul Ali Ekrem 
Published: September 2007

AbstractJapan and Korea have highly developed information and communications technology infrastructures and have recently reformed their higher education systems and encouraged e‐transformation. However, Japanese universities have not embraced e‐learning as wholeheartedly as their Korean counterparts. The paper concludes that this is due to governmental and institutional failure to develop a cogent vision and strategic plan for e‐learning, to recognise the need for fundamental shifts in organisational cultures and structures and pedagogy and to provide training, funding, recognition and reward for such development. It attributes this to differences in the cultural perspectives, values and customs of the two countries' policy makers, managers and faculty members. The findings are seen to hold important lessons for other countries embarking on e‐transformation.
Foreign Money Shocks and the Welfare Performance of Alternative Monetary Policy Regimes*
Authors: Senay Ozge , Sutherland Alan 
Published: September 2007

AbstractThe welfare properties of monetary policy regimes for a country subject to foreign money shocks are examined in a two‐country sticky‐price model. Money targeting is found to be welfare superior to a fixed exchange rate when the expenditure switching effect of exchange rate changes is relatively weak, but a fixed rate is superior when the expenditure switching effect is strong. However, price targeting is superior to both these regimes for all values of the expenditure switching effect. A welfare‐maximising monetary rule yields lower output and exchange rate volatility than price targeting for a wide range of parameter values.
Estimating Risk Attitudes in Denmark: A Field Experiment*
Authors: Harrison Glenn W. , Lau Morten I. , Rutström E. Elisabet 
Published: September 2007

AbstractWe estimate individual risk attitudes using controlled experiments in the field in Denmark. The experiments were carried out across Denmark using a representative sample of 253 people between 19 and 75 years of age. Risk attitudes are estimated for various individuals differentiated by socio‐demographic characteristics. Our results indicate that the average Dane is risk averse, and that risk neutrality is an inappropriate assumption to apply. We also find that risk attitudes vary significantly with respect to several important socio‐demographic variables such as age and education. However, we do not find any effect of sex on risk attitudes.
Too Much of a Good Thing? The Quantitative Economics of R&D‐driven Growth Revisited
Authors: Strulik Holger 
Published: September 2007

AbstractThis article augments an R&D‐based growth model of the third generation with human capital accumulation and impure altruism, calibrates it with U.S. data, and investigates whether the market provides too little or too much R&D. For benchmark parameters, the market share of employment in R&D is close to the socially optimal solution. Sensitivity analysis shows that the order of magnitude of possible deviation between market R&D and optimal R&D is also smaller than suggested by previous studies. Small deviation of total research effort, however, can be compatible with large sectoral misallocations. Furthermore, the model allows for two additional channels through which population growth may affect the resource allocation so that its overall economic impact is no longer predetermined as positive. Numerical calibrations show that economic growth at the average rate in the U.S. over the last century can be consistent with a small and probably negative partial correlation between population growth and economic growth.
A genetic survey of heavily exploited, endangered turtles: caveats on the conservation value of trade animals
Authors: Fong J. J. , Parham J. F. , Shi H. , Stuart B. L. , Carter R. L. 
Published: September 2007

AbstractAsian turtles face an extinction crisis, and so it is imperative that systematists accurately determine species diversity in order to guide conservation strategies effectively. We surveyed mitochondrial and nuclear DNA (mtDNA and nuDNA) variation of the heavily exploited Mauremys mutica complex, a clade of Asian turtles that contains the endangered M. mutica from Japan, Taiwan, China and Vietnam, and the critically endangered Mauremys annamensis from central Vietnam. We discovered extensive mtDNA and nuDNA variation among samples that did not correspond to the currently recognized taxonomy. Both nuDNA and mtDNA data suggest that M. mutica is paraphyletic with respect to M. annamensis. Surprisingly, M. annamensis exhibits a previously unknown mtDNA structure in the form of two clades that are paraphyletic to M. mutica. These data reveal that the currently recognized taxonomy of the mutica complex does not reflect the genetic diversity of our samples. Unfortunately, many conservation‐oriented captive‐breeding efforts for turtles are also based on trade samples such as the ones studied here. These efforts include plans to breed trade‐rescued individuals and release their progeny into the wild. Because our genetic survey reveals that the taxonomic identity of these samples does not reflect genetic diversity, we raise serious questions about the efficacy of these programs. In order to address conservation issues and provide more accurate estimates of evolutionary lineages within Mauremys, we recommend continued surveys for wild populations of the mutica complex to provide new genetic material and additional distributional data, attempts to extract DNA from historic museum specimens and a shift in conservation focus to in situ preservation of wild populations and associated habitat.
What happens if density increases? Conservation implications of population influx into refuges
Authors: Metcalf C. J. E. , Hampson K. , Koons D. N. 
Published: September 2007

AbstractSudden catastrophic events like fires, hurricanes, tsunamis, landslides and deforestation increase population densities in habitat fragments, as fleeing animals encroach into these refuges. Such sudden overcrowding will trigger transient fluctuations in population size in the refuges, which may expose refuge populations to an increased risk of extinction. Until recently, detailed information about the operation of density dependence in stage‐structured populations, and tools for quantifying the effects of transient dynamics, have not been available, so that exploring the extinction risk of such transient fluctuations has been intractable. Here, we use such recently developed tools to show that extinction triggered by overcrowding can threaten populations in refuges. Apart from situations where density dependence acts on survival, our results indicate that short‐lived species may be more at risk than longer‐lived species. Because dynamics in local populations may be critical for the preservation of metapopulations and rare species, we argue that this aspect warrants further attention from conservation biologists.
Uniparental (mtDNA, Y‐chromosome) Polymorphisms in French Guiana and Two Related Populations – Implications for the Region's Colonization
Authors: Mazières S. , Guitard E. , Crubézy E. , Dugoujon J.‐M. , Bortolini M. C. , Bonatto S. L. , Hutz M. H. , Bois E. , Tiouka F. , Larrouy G. , Salzano F. M. 
Published: September 2007

SummaryBlood samples collected in four Amerindian French Guiana populations (Palikur, Emerillon, Wayampi and Kali'na) in the early 1980s were screened for selected mtDNA and Y‐chromosome length polymorphisms, and sequenced for the mtDNA hypervariable segment I (HVS‐I). In addition, two other Amerindian populations (Apalaí and Matsiguenga) were examined for the same markers to establish the genetic relationships in the area. Strong dissimilarities were observed in the distribution of the founding Amerindian haplogroups, and significant p‐values were obtained from FSTgenetic distances. Interpopulation similarities occurred mainly due to geography. The Palikur did not show obvious genetic similarity to the Matsiguenga, who speak the same language and live in a region from where they could have migrated to French Guiana. The African‐origin admixture observed in the Kali'na probably derives from historical contacts they had with the Bushinengue (Noir Marron), a group of escaped slaves who now lead independent lives in a nearby region. This analysis has identified significant clues about the Amerindian peopling of the North‐East Amazonian region.
Leisure time physical exercise during pregnancy and the risk of miscarriage: a study within the Danish National Birth Cohort
Authors: Madsen M , Jørgensen T , Jensen ML , Juhl M , Olsen J , Andersen PK , Nybo Andersen A‐M 
Published: September 2007

Objective  To examine the association between leisure time physical exercise during pregnancy and the risk of miscarriage.Design  Prospective study with elements of retrospective data collection.Setting  Denmark 1996–2002.Population  A total of 92 671 pregnant women enrolled in the Danish National Birth Cohort and interviewed subsequently.Methods  Data on exercise during pregnancy and potential confounders were obtained through computer‐assisted telephone interviews either during pregnancy or after an early miscarriage. Outcome of pregnancy was identified by register linkage. Using Cox regression analysis, we estimated the hazard ratio (HR) of miscarriage according to weekly amount of exercise and the type of exercise. The HR was estimated for <11, 11–14, 15–18, and 19–22 weeks of gestation, respectively.Main outcome measures  Miscarriage, defined as fetal loss before 22 completed weeks of gestation.Results  A stepwise increasing relation was found between amount of exercise and risk of miscarriage, where risk of miscarriage increased by amount of exercise up to HR = 3.7 (95% CI 2.9–4.7) for women who exercised more than 7 hours per week compared with nonexercisers. Particularly ‘high‐impact exercise’ was associated with an increased risk of miscarriage. No association was seen between exercise and risk of miscarriage after 18 weeks of gestation.Conclusions  This study suggests that exercise early in pregnancy is associated with an increased risk of miscarriage. The results should, however, be interpreted cautiously as potential bias arising from retrospective data collection may explain part of the association.
Vesicular release of glutamate mediates bidirectional signaling between astrocytes and neurons
Authors: Ni Yingchun , Malarkey Erik B. , Parpura Vladimir 
Published: September 2007

AbstractThe major excitatory neurotransmitter in the CNS, glutamate, can be released exocytotically by neurons and astrocytes. Glutamate released from neurons can affect adjacent astrocytes by changing their intracellular Ca2+ dynamics and, vice versa, glutamate released from astrocytes can cause a variety of responses in neurons such as: an elevation of [Ca2+]i, a slow inward current, an increase of excitability, modulation of synaptic transmission, synchronization of synaptic events, or some combination of these. This astrocyte‐neuron signaling pathway might be a widespread phenomenon throughout the brain with astrocytes possessing the means to be active participants in many functions of the CNS. Thus, it appears that the vesicular release of glutamate can serve as a common denominator for two of the major cellular components of the CNS, astrocytes and neurons, in brain function.
The differential effects of single or repeated restraint stress on kainic acid‐induced neuronal death in the hippocampal CA3 region: the role of glucocorticoid and various signal molecules
Authors: Kwon Min‐Soo , Seo Young‐Jun , Choi Seung‐Min , Choi Hee‐Woo , Jung Jun‐Sub , Park Soo‐Hyun , Suh Hong‐Won 
Published: September 2007

AbstractThe effect of stress mediators following the stress period and addition time is a controversial issue until now. Thus, we aim to clarify the differential effects of single restraint stress (SS) or repeated restraint stress (RS) on kainic acid (KA)‐induced neuronal death especially as addressing not only the role of glucocorticoid (Gc) and its receptor but also the signal pathway leading to cAMP response element binding protein phosphorylation (pCREB) and its functional role during stress. In the present study, we found that although RS did not show any difference on serum Gc level and hippocampal Gc receptor level compared to SS, SS exacerbated KA‐induced neuronal death in hippocampal CA3 region, but RS did not. Moreover, pre‐treatment with RU 38486 (Gc receptor antagonist) abolished the effect of SS on KA‐induced neuronal death without an effect on KA toxicity itself. Furthermore, RS aggravates KA‐induced neuronal death when CREB phosphorylation was deprived by KN‐93 (calcium/calmodulin‐dependent protein kinase II inhibitor). However, other signal molecules inhibitors such as PD98059 (MEK1/2 inhibitor) and SP600125 (p‐p38 inhibitor) have no effect on KA‐induced neuronal death after RS although these signal molecule were increased during SS or RS. These findings suggest that pCREB expression via calcium/calmodulin‐dependent protein kinase II phosphorylation during RS comprise one of the balancers against Gc induced by stress.
Peroxisome proliferator‐activated receptor‐α agonist fenofibrate regulates IL‐12 family cytokine expression in the CNS: relevance to multiple sclerosis
Authors: Xu Jihong , Racke Michael K. , Drew Paul D. 
Published: September 2007

AbstractThe interleukin‐12 (IL‐12) family of cytokines which includes IL‐12, IL‐23, and IL‐27 play critical roles in T cell differentiation and are important modulators of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Previously, we demonstrated that peroxisome proliferator‐activated receptor (PPAR) ‐α agonists suppress the development of EAE. The present studies demonstrated that the PPAR‐α agonist fenofibrate inhibited the secretion of IL‐12p40, IL‐12p70 (p35/p40), IL‐23 (p19/p40), and IL‐27p28 by lipopolysaccharide‐stimulated microglia. The cytokines interferon‐γ and tumor necrosis factor‐α also stimulated IL‐12 p40 and IL‐27 p28 expression by microglia, which was suppressed by fenofibrate. Furthermore, fenofibrate inhibited microglial expression of CD14 which plays a critical role in TLR signaling, suggesting a mechanism by which this PPAR‐α agonist regulates the production of these pro‐inflammatory molecules. In addition, fenofibrate suppressed the secretion of IL‐12p40, IL‐23, and IL‐27p28 by lipopolysaccharide‐stimulated astrocytes. Importantly, fenofibrate suppression of EAE was associated with decreased expression of IL‐12 family cytokine mRNAs as well as mRNAs encoding TLR4, CD14, and MyD88 known to play critical roles in MyD88‐dependent TLR signaling. These novel observations suggest that PPAR‐α agonists including fenofibrate may modulate the development of EAE, at least in part, by suppressing the production of IL‐12 family cytokines and MyD88‐dependent signaling.
PERMANENT GENETIC RESOURCES: Twelve polymorphic microsatellite markers for the bonefish, Albula vulpes and two congeners
Authors: SEYOUM SEIFU , WALLACE ELIZABETH M. , TRINGALI MICHAEL D. 
Published: September 2007

AbstractTwelve polymorphic microsatellite loci were isolated for the bonefish, Albula vulpes using a polymerase chain reaction‐based procedure. The number of alleles ranged from two to 23 (mean = 8.8) in 37 specimens from south Florida. Observed and expected heterozygosities ranged from 0.07 to 0.77 (mean = 0.42) and from 0.07 to 0.84 (mean = 0.48), respectively. There were no significant departures from Hardy–Weinberg equilibrium and no evidence of genotypic disequilibrium between any pair of loci. In a cross‐amplification test, all markers yielded appropriately sized alleles for specimens of the provisional Albula sp. B and 11 of the 12 loci amplified for those of Albula glossodonta.
Phosphorus losses at the catchment scale within Europe: an overview
Authors: Kronvang B. , Vagstad N. , Behrendt H. , Bøgestrand J. , Larsen S. E. 
Published: September 2007

AbstractQuantifying P losses to surface waters at different scales and partitioning of the loads into P losses from point sources and diffuse sources are significant future challenges for river basin managers. The agricultural share of P losses to surface waters is, in many river basins, increasing and therefore becoming more important to quantify and analyse. The importance of phosphorus losses from agricultural land was analysed using monitoring data and two different models for 35 micro‐catchments (<30 km2) in the Nordic–Baltic region of Europe, 17 European macro‐catchments (250–11 000 km2) and 10 large European river basins (>50 000 km2). Average annual phosphorus loss from agricultural land in the micro‐catchments varied from 0.1 to 4.7 kg P ha−1 and showed no relationship with the short‐term P surplus on agricultural land. The average annual total P loss from agricultural land showed equally large variation in the 17 macro‐catchments (0.1–6.0 kg P ha−1), but the range was less for the 10 larger river basins (0.09–2.0 kg P ha−1). The annual P loss from the 35 micro‐catchments was greatest in the micro‐catchments characterized by soil erosion and a high proportion of surface run‐off as in the Norwegian catchments. The same pattern was true for the 17 macro‐catchments where the model‐simulated total P loss from agricultural land was greatest in the catchments in northern and southern parts of Europe. The main diffuse pathways for total P loads in the 17 macro‐catchments were simulated with the MONERIS model. On average, soil erosion and surface run‐off was estimated to have contributed 53% (4.1–81%), groundwater 14% (0.2–41.7%) and tile drainage water 3% (0–14.0%).
Reducing phosphorus losses from over‐fertilized grassland soils proves difficult in the short term
Authors: Schärer M. , Stamm C. , Vollmer T. , Frossard E. , Oberson A. , Flühler H. , Sinaj S. 
Published: September 2007

AbstractPhosphorus (P) losses from many agricultural soils are driven by fast transport processes, such as surface runoff, shallow interflow and macropore flow. Close interaction of rain with topsoil layers (0–5 cm), rich in available P, results in high P concentrations in these rapid runoff pathways. This is particularly pronounced in permanent grassland soils typically characterized by a P enrichment of the topsoil. One option to mitigate P losses from grassland is therefore to reduce soil P content, particularly available P, in this critical surface layer. Omitting application of P fertilizer will reduce soil P in the long term but more drastic methods may be necessary to achieve P loss reductions in shorter timescales. In this study, three management options to reduce P in runoff from grassland soils were evaluated in a field experiment lasting 2 years on two grassland sites: (i) no P inputs, (ii) no P inputs plus soil tillage and (iii) no P inputs plus tillage combined with application of a P sorbing soil amendment (iron oxide). Withholding P inputs did not decrease either the available P in the soil or the P concentrations in runoff from sprinkler experiments over a 2‐year period. Both the treatments which included tillage caused immediate reductions in both soil available P and runoff P, with Fe/OH amendment being more effective. However, in the second year the effects of both tillage treatments were less apparent and only the Fe/OH treatment significantly decreased runoff P. The results indicate that the long‐term enrichment of soils due to P application in excess of plant needs is unlikely to be remedied by short‐term treatments. However, further work is required to assess the applicability of our conclusion to other sites.