bluuebunny/crossref_metadata_2025 huggingface dataset:
Hierarchical model for web multimedia documents retrieval and periodical updates
Authors: Habib Sami , Safar Maytham
Published: April 2008

Purpose

The purpose of this paper is to propose a four‐level hierarchy model for multimedia documents representation to be used during the dynamic scheduling and altering of multimedia contents.

Design/methodology/approach

The four‐level hierarchy model (object, operation, timing, and precedence), offers a fine‐grain representation of multimedia contents and is embedded within a research tool, which is called WEBCAP. WEBCAP utilizes the four‐level hierarchy to synchronize the retrieval of objects in the multimedia document employing Allen's temporal relations, and then applies the Bellman‐Ford's algorithm on the precedence graph to schedule all operations (fetch, transmit, process, and render), while satisfying the in‐time updating and all web workload's resources constraints.

Findings

The experimental results demonstrate the effectiveness of the model in scheduling the periodical updating multimedia documents while considering a variety of workloads on web/TCP.

Research limitations/implications

WEBCAP should be enhanced to automatically measure and/or approximate the available bandwidth of the system using sophisticated measurement of end‐to‐end connectivity. In addition, WEBCAP should be expanded and enhanced to examine system infrastructure for more real‐time applications, such as tele‐medicine and e‐learning.

Practical implications

WEBCAP can be used as an XML markup language for describing multimedia presentations. It can be used to create online presentations similar to PowerPoint on desktop environment, or used as an interactive e‐learning tool. An HTML browser may use a WEBCAP plug‐in to display a WEBCAP document embedded in an HTML/XML page.

Originality/value

This paper proposed a dynamic scheduling of multimedia documents with frequent updates taking into consideration the network's workload to reduce the packet lost ratio in the TCP flow, especially in the early stages. WEBCAP can be used to guide distributed systems designers/managers to schedule or tune their resources for optimal or near optimal performance, subject to minimizing the cost of document retrieval while satisfying the in time constraints.
SensorWebIDS: a web mining intrusion detection system
Authors: Ezeife C.I. , Dong Jingyu , Aggarwal A.K.
Published: April 2008

Purpose

The purpose of this paper is to propose a web intrusion detection system (IDS), SensorWebIDS, which applies data mining, anomaly and misuse intrusion detection on web environment.

Design/methodology/approach

SensorWebIDS has three main components: the network sensor for extracting parameters from real‐time network traffic, the log digger for extracting parameters from web log files and the audit engine for analyzing all web request parameters for intrusion detection. To combat web intrusions like buffer‐over‐flow attack, SensorWebIDS utilizes an algorithm based on standard deviation (δ) theory's empirical rule of 99.7 percent of data lying within 3δof the mean, to calculate the possible maximum value length of input parameters. Association rule mining technique is employed for mining frequent parameter list and their sequential order to identify intrusions.

Findings

Experiments show that proposed system has higher detection rate for web intrusions than SNORT and mod security for such classes of web intrusions like cross‐site scripting, SQL‐Injection, session hijacking, cookie poison, denial of service, buffer overflow, and probes attacks.

Research limitations/implications

Future work may extend the system to detect intrusions implanted with hacking tools and not through straight HTTP requests or intrusions embedded in non‐basic resources like multimedia files and others, track illegal web users with their prior web‐access sequences, implement minimum and maximum values for integer data, and automate the process of pre‐processing training data so that it is clean and free of intrusion for accurate detection results.

Practical implications

Web service security, as a branch of network security, is becoming more important as more business and social activities are moved online to the web.

Originality/value

Existing network IDSs are not directly applicable to web intrusion detection, because these IDSs are mostly sitting on the lower (network/transport) level of network model while web services are running on the higher (application) level. Proposed SensorWebIDS detects XSS and SQL‐Injection attacks through signatures, while other types of attacks are detected using association rule mining and statistics to compute frequent parameter list order and their maximum value lengths.
Attitudes toward material possessions among Chinese children
Authors: Chan Kara , Hu Fan
Published: April 2008

Purpose

This study seeks to quantify how children in urban China perceive someone described as owning many or few expensive toys. It aims to measure the types of possessions and personal characteristics they attributed to such individuals. This is an extension of previous research on perceived links between possessions and personal characteristics.

Design/methodology/approach

A total of 268 Chinese children aged 9 to 14 were surveyed using a self‐administered questionnaire. Participants saw photos of a child described as having few or many expensive toys. They then imagined the possessions and personal characteristics of such a child. They also reported which child they would prefer to be.

Findings

A child with a lot of toys was perceived as more likely to have branded toys and new media toys. Such a child was more likely to be imagined as spending irresponsibly, selfish and envious of others. A child without many toys was considered more likely to have books and sports‐related toys. Participants were more likely to perceive this child as hardworking, with good academic results, smart, and with lots of friends. A total of 40 percent of the participants said they would prefer to be the child without many toys.

Research limitations/implications

The participants mostly came from lower middle class families, and they may be particularly inclined to project good qualities on people without many possessions.

Practical implications

Marketers and advertisers should be sensitive to the perceived link between possessions and negative personal characteristics of the owner. Advertisers of premium products and brands for children should stress the functional superiority of the products.

Originality/value

These results quantify and verify the results of a previous qualitative enquiry. They provide guidelines for marketers attempting to reach children in China in a culturally sensitive manner.
Patient satisfaction with healthcare delivery systems
Authors: Baalbaki Imad , Ahmed Zafar U. , Pashtenko Valentin H. , Makarem Suzanne
Published: April 2008

Purpose

The purpose of this paper is to provide insight, exploratory research, and support for the strategic use of hospital secondary support functions as an initial strategy for marketing healthcare, increasing patient volume, and expanding patient satisfaction.

Design/methodology/approach

This research paper is based upon longitudinal patient satisfaction and perception studies following both emergency room and elective‐stay hospitalization visits in Beirut. Exploratory statistical methods are used to examine substantial data comprising over 300 patient stays. Comprehensive information is presented which illustrates patient perceptions, their inflection points, and the importance of this knowledge in the marketing of hospitals and health care systems.

Findings

This research paper presents that patient perceptions are significantly influenced by hospital support functions. Further, these perceptions determine hospital reputation, influence future patient demands, and are integral to the understanding of patients as consumers of health care systems rather than consumers of medical procedures.

Practical implications

This paper provides support for health care system administrators who are often at odds with health care core service administrators and personnel with respect to long‐term hospital growth strategies. It illustrates that focusing on increasing core competencies is a short‐sighted approach to developing health care systems. It provides support for growing secondary support functions as being a more efficient means to increasing long‐term core competencies.

Originality/value

The originality of this paper is that it illustrates the conflict between the immediate medical care that health care systems understand to be their strategy and the strategies that truly grow hospital health care systems. It illustrates the paradox that requires hospitals to focus upon secondary support functions rather than core competencies in order to market themselves using strategies consistent with long‐term growth.
Research in applying the financial appraisal profile model to an information communication technology project within a professional association
Authors: Lefley Frank
Published: April 2008

Purpose

The purpose of this paper is to report on research in applying the financial appraisal profile (FAP) model to an information communication technology project within a professional association and to evaluate the model's effectiveness and acceptability.

Design/methodology/approach

The FAP model incorporates both rationalistic and hermeneutic paradigms. An action research/single case study approach has been use to “evaluate” the model in a real life situation.

Findings

It is shown that the model addresses many of the issues it set out to address and is perceived by both senior and corporate management as an effective tool in the evaluation of capital assets such as information technology (IT) projects. Important issues regarding, what has been termed, “groupthink” and the influence of a “project champion” on the evaluation of capital projects are also highlighted. The inclusion of what has been termed “the IT score” further enhances the models applicability to IT projects.

Research limitations/implications

Although the practical application of the model provides credible evidence for its pragmatic support, this is limited by the fact that it is based on a single case study.

Practical implications

It is hoped that practitioners will find the FAP model more pragmatic than their existing capital investment appraisal methods/procedures and that it will result in improved decision making.

Originality/value

The FAP model is a new concept and this is the first study in applying this model to an actual real life capital project. It also shows how a Delphi approach can be used in a practical setting.
Phenotypic plasticity in seedling defense strategies: compensatory growth and chemical induction
Authors: Barton Kasey E.
Published: April 2008

Phenotypic plasticity in growth (leading to compensation) and secondary chemical production (leading to induction) in response to herbivory are key defense strategies in adult plants, but their role in seedling defense remains unclear. A pair of greenhouse studies was conducted to investigate compensation and induction in seedlings and juvenile plants, using Plantago lanceolata (Plantaginaceae) and the specialist buckeye caterpillar Junonia coenia (Nymphalidae) as a model system. Plants received 50% defoliation at two and four weeks of age, and groups of plants were harvested one week after herbivory and six to eight weeks after herbivory to investigate the duration of the responses. Plants damaged at two weeks showed no chemical induction and fully compensated for the lost leaf tissue by ten weeks of age. Plants damaged at four weeks showed a significant reduction in iridoid glycosides one week after herbivory and achieved full shoot compensation by ten weeks of age at the expense of root biomass. These results indicate that P. lanceolata seedlings use compensation, but not chemical induction, as a defense strategy. This research highlights the importance of considering ontogeny in studies of plant–herbivore interactions and suggests that seedling defense may differ markedly from adult plant defense.
Environmental stability and the distribution of the sexes: insights from life history experiments with the geographic parthenogen Eucypris virens (Crustacea: Ostracoda)
Authors: João Fernandes Martins Maria , Vandekerkhove Jochen , Namiotko Tadeusz
Published: April 2008

In many species with mixed reproduction, parthenogens cover a wider geographic range than sexuals. In freshwater ostracods this pattern referred to as geographic parthenogenesis is traditionally explained by ascribing a higher potential for dispersal to parthenogens. For example, the postglacial invasion hypothesis states that the lack of males in northern Europe is caused by the relatively slow range expansion of sexual lineages after deglaciation. An alternative explanation for the contemporary distribution of the sexes is based on spatial and temporal variations in ecological habitat stability. To test this hypothesis, we compared life history data of Eucypris virens individuals originating from bisexual and all‐female populations. Populations with males are only found around the Mediterranean, whereas parthenogens cover most of Europe. The animals were hatched and grown in environments mimicking temperature and photoperiod conditions observed in Belgium and Spain. The data confirm the higher potential for population growth in parthenogens. In particular their faster hatching response, possibly higher fecundity (as derived from a difference in body height) and the absence of a cost of males should allow them to out‐compete sexuals under stable conditions. However, the comparison of the hatchling accumulation curves of bisexual and all‐female populations suggests that sexuals have an advantage in highly unpredictable environments. Indeed, under conditions mimicking those in southern Europe, bisexual populations exhibit a bet‐hedging strategy, while parthenogenetic resting eggs hatch on average earlier and more synchronously. Overall, the life history data stress the importance of short term environmental fluctuations for the distribution of the sexes in E. virens, and probably many other inhabitants of ephemeral water bodies.
Host plant quality and defence against parasitoids: no relationship between levels of parasitism and a geometrid defoliator immunoassay
Authors: Klemola Netta , Kapari Lauri , Klemola Tero
Published: April 2008

Host plant quality has a major influence on the performance, and ultimately on the fitness of an herbivorous insect, but may also have indirect effects on the third trophic level by affecting an herbivore's defensive ability against natural enemies. In a three‐year field study, we examined the effects of natural food quality on the ability of autumnal moths, Epirrita autumnata (Lepidoptera, Geometridae), to defend themselves against parasitoids. In each year, we confirmed the variation in quality of host trees (mountain birch, Betulapubescens ssp. czerepanovii) by determining the mass of pupae reared in mesh bags attached to the trees and the water content of leaves. Individuals grown on high quality trees possessed significantly higher encapsulation rate of a foreign antigen as pupae compared to those on low quality trees during the first and third study years; a parallel trend was also found in the second study year, although this difference was not statistically significant. However, in spite of observed differences in encapsulation rates, individuals reared on high and low quality trees did not differ in their levels of parasitisation when exposed to hymenopteran parasioids in the wild and thus were equally vulnerable. Accordingly, the encapsulation response seems not to play a major role on the population ecology scale in the studied system. Our findings also stress the importance of direct resistance tests, which should be conducted along with tests of insect immune function.
Evaluation of a rapid ELISA technique for detection of circulating antigens of Toxoplasma gondii
Authors: Chen Rui , Lu Shaohong , Lou Di , Lin Aifen , Zeng Xiaojun , Ding Zhenyin , Wen Liyong , Ohta Nobuo , Wang Jinfu , Fu Cuie
Published: April 2008

To evaluate a modified rapid ELISA method for detecting CAg during Toxoplasma gondii infection, we analyzed the specificity and sensitivity of the ELISA method by using experimental Toxoplasma infection in rabbits and also tested this method in human samples including 5428 serum, 548 cerebrospinal fluid and two breast milk samples. We prepared PcAb, and used it for rapid one‐step sandwich ELISA testing in which an incubation time in the regular ELISA procedure was omitted. This method detected CAg at the concentration of 31.2 ng/mL, and no cross‐reaction was found with antigens of protozoa (Cryptosporidium parvum, Plasmodium falciparum), trematode (Schistosoma japonicum, Paragonimus sp.) and nematode (Brugia malayi, Ancylostoma duodenale, Ascaris lumbricoides and Trichinella spiralis). CAg was detected in rabbit serum 3 days after infection, and optical density values reached a peak 9 ∼ 13 days after infection, then declined gradually. Among human serum samples, the positive rate of CAg was 2.11% in cerebral paralysis patients, whereas it was 0.22% or 0.71% in patients without neurological symptoms or in uncomplicated pregnant women. The difference among these three groups was statistically significant (P < 0.05). The positive rate of cerebrospinal fluid samples from cerebral paralysis patients was 10.58%. There is a statistically significant difference between the positive rates of meat‐packing workers and blood donors (P < 0.01). In the retrospective analysis, CAg was detected in accordance with the onset of clinical symptoms, suggesting that CAg could reflect the clinical course in humans. Together with these results, CAg detected in the modified rapid sandwich ELISA could be a sensitive marker for acute and active infection of T. gondii.
Enhancement of gene expression by a peptide p(CHWPR) produced by Bifidobacterium lactis BB‐12
Authors: Mitsuma Takashi , Odajima Hiroko , Momiyama Zyunko , Watanabe Kana , Masuguchi Misako , Sekine Takashi , Shidara Satoshi , Hirano Shigeki
Published: April 2008

Recently, probiotics, including Bifidobacterium, Lactobacillus, and Enterococcus, among other organisms, have been clinically applied for their enhancing effects on defense mechanisms. It is reported that gene expression in somatic cells can be activated by autoinducers, which are hormone‐like molecules produced in a microbial QS system. In the present study, based on a hypothesis that a low‐molecular substance related to the QS system is involved in the probiotics effects of Bifidobacterium, we intended to extract the low‐molecular substance. As a result, we successfully isolated the peptide p(CHWPR), which was composed of five amino acids including Cys, His, Trp, Pro, and Arg, and found that the peptide was produced in the stationary phase of bacterial growth and that it could enhance the gene expression of oxalyl‐CoA decarboxylase (Oxc). p(CHWPR) enhanced the gene expression of c‐myc and interleukin (IL)‐6 in an established cell line, HL‐60. We demonstrated that p(CHWPR) penetrates the cell membrane and binds specifically to RORγ, which is a cytosolic nuclear receptor. This suggests that RORγ bound to p(CHWPR) would bind to promoter regions of the c‐myc gene. Furthermore, we found that p(CHWPR) also bound to a transcriptional avtivation subunit, CRSP70; this suggests that p(CHWPR), RORγ, and CRSP70 in combination enhance transcription activity.
Increased susceptibility to tumor necrosis factor‐α in butyric acid‐induced apoptosis is caused by downregulation of cFLIP expression in Jurkat T cells
Authors: Seto Shintaro , Kurita‐Ochiai Tomoko , Ochiai Kuniyasu
Published: April 2008

Butyric acid is one of the major extracellular metabolites of periodontopathic Gram‐negative bacteria. We previously demonstrated that butyric acid induced apoptosis in human T cells. In the present study, we examined the interaction between butyric acid and TNF‐α in Jurkat T‐cell apoptosis. Simultaneous treatment with TNF‐α enhanced butyric acid‐induced apoptosis by promoting caspase activity more than was achieved by either reagent alone. We examined which genes were associated with the increased susceptibility to TNF‐α caused by butyric acid, and revealed that expression of cFLIP decreased with increased concentrations of butyric acid. Furthermore, exogenous expression of cFLIP protein suppressed the enhancing effect by TNF‐α in the apoptosis. These results suggest that butyric acid downregulates cFLIP expression and increases the susceptibility to TNF‐α by activating caspases via the death receptor signal.
Identification of a human monoclonal Fab with neutralizing activity against H3N2 influenza A strain from a newly constructed human Fab library
Authors: Shibuya Tadamasa , Yamashiro Tetsu , Masaike Yuka , Ohuchi Masanobu , Uechi Gen‐ichiro , Nishizono Akira
Published: April 2008

A combinatorial Fab library was constructed in pComb3H phagemid vectors, using RNA from peripheral blood lymphocytes of a healthy volunteer who had recovered from an influenza A virus infection. The library contained approximately 1.3 × 108E. coli transformants. Bio‐panning was carried out against an influenza vaccine containing components of influenza A/New Caledonia/20/99 (H1N1), A/Panama/2007/99 (H3N2), and B/Shandong/7/97 for the enrichment of phages displaying human Fab specific to the viral proteins. E. coli transformed with IF1A11, 1 of 94 randomly selected clones, displayed a human Fab antibody molecule (FabIF1A11) with efficient neutralizing activity against H3N2 influenza A virus strains. The purified FabIF1A11 demonstrated neutralizing activity against A/Okayama/6/01 (H3N2) and A/Kitakyushu/159/93 (H3N2) with 50% plaque reduction neutralization titers of 0.11 μg/ml (2.2 nM) and 1.4 μg/ml (28 nM) respectively. However, FabIF1A11 did not show neutralizing activity against the influenza A virus strain A/USSR/77 (H1N1) or the influenza B virus strain B/Kanagawa/73, even at a concentration of 20 μg/ml (400 nM). The Kd of FabIF1A11 was calculated as 3.6 × 10−9 M. FabIF1A11 was estimated to recognize a conformational epitope on the hemagglutinin of A/Okayama/6/01 (H3N2). The human monoclonal Fab product FabIF1A11 may have potential as a therapeutic or short‐term prophylactic molecule for humans with influenza A H3N2 infection.
Polymeric black tea polyphenols inhibit mouse skin chemical carcinogenesis by decreasing cell proliferation
Authors: Patel R. , Krishnan R. , Ramchandani A. , Maru G.
Published: April 2008

Abstract.  Objectives: The aim of this study was to investigate the antitumour promoting effects and possible mechanisms of action of the most abundant polymeric black tea polyphenols (PBPs 1–5) or thearubigins, in vivo. Materials and methods: Effect of PBP pre‐treatments on 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) promoted skin papillomas was studied in 7,12‐dimethylbenz(a)anthracene initiated mice over 40 weeks. Cell proliferation and apoptosis, in epidermis of the skin, were measured using appropriate immunohistochemical staining. Mitogen‐activated protein kinase signalling studies were conducted with Western blot analysis at 10, 20, 30 and 40 weeks of promotion. Results: Pre‐treatments with PBP fractions differentially altered latency, multiplicity and incidence of skin papillomas as compared to TPA treatments thereby exhibiting antipromoting effects. Most PBP fractions decreased TPA‐induced cell proliferation by decreasing activation of signalling kinases (c‐Jun N‐terminal protein kinase, extracellular signal‐regulated protein kinase, p38 protein kinase and Akt), transcription factors (activator protein‐1 and nuclear factor kappa B) and inflammatory protein (cyclooxygenase 2). TPA‐induced epidermal cell apoptosis was also decreased by pre‐treatment with most PBP fractions. Higher levels of p53 and p21 in skin cells pre‐treated with PBP fractions followed by TPA treatment as compared to only TPA‐treated animals suggested possible activation of a cell cycle checkpoint. Conclusions: PBP‐2 was observed to be the most potent polymeric polyphenol fraction and PBP‐4 and PBP‐5 showed only marginal activity, whereas PBP‐1 and PBP‐3 displayed intermediate efficacies. In conclusion, the protective effects of PBP fractions could be attributed to inhibition of TPA‐induced cellular proliferation.
Resistance to ship‐induced waves of benthic invertebrates in various littoral habitats
Authors: GABEL F. , GARCIA X. ‐F. , BRAUNS M. , SUKHODOLOV A. , LESZINSKI M. , PUSCH M. T.
Published: April 2008

1. Ship‐induced waves disturb benthic invertebrate assemblages colonizing littoral zones of lakes and rivers. However, the impact of ship‐induced waves on invertebrates has rarely been quantified, and the influencing factors have not been addressed.

2. In an experimental wave tank, five benthic invertebrate species, Bithynia tentaculata, Calopteryx splendens, Dikerogammarus villosus, Gammarus roeseli and Laccophilus hyalinus, were exposed to waves of increasing shear stress (0.43–2.19 N m−2). Mean number of detached individuals was recorded for five littoral habitats [coarse woody debris (CWD), reeds, sand, stones and tree roots], representing different levels of structural complexity as quantified by their fractal dimensions (FD).

3. Results showed that detachment of invertebrates was significantly related to shear stress in all habitats except tree roots. Detachments averaged for the five species were significantly lower in habitats with a high degree of structural complexity, decreasing in the habitat sequence: sand, CWD, stones, reeds and tree roots.

4. Consistent with their different morphologies and methods of attachment to substrates, the five species displayed differences in their response to hydraulic stress that were dependent on habitat.

5. The increasing sheltering effect of structural habitat complexity was mirrored by increasing dissipation of the kinetic energy of waves; i.e. the FD of the habitat was positively correlated with shear stress reduction due to the flow resistance of the habitat.

6. Network habitats such as tree roots provided the best sheltering conditions against hydraulic disturbance, because they combined good refuge availability for all studied invertebrate species and maximal dissipation of kinetic wave energy. Consequently, persistent anthropogenic impacts, such as lakeshore modification or long‐term exposure to ship‐induced waves, which cause disappearance of complex littoral habitats such as tree roots or dense reed belts, will drastically increase the adverse effects of boating and ship traffic on littoral invertebrate assemblages.
Taxonomic differences in the essential fatty acid composition of groups of freshwater zooplankton relate to reproductive demands and generation time
Authors: SMYNTEK PETER M. , TEECE MARK A. , SCHULZ KIMBERLY L. , STORCH ADAM J.
Published: April 2008

1. Marked differences were observed in the total fatty acid concentrations and essential fatty acid (EFA) distributions of co‐existing freshwater copepods and cladocerans in four large lake systems (lakes Michigan, Erie, Ontario and Champlain) over two growing seasons. These patterns appeared independent of lake seston EFA composition.

2. Compared to the cladocerans, calanoid and cyclopoid copepods contained significantly higher concentrations of total fatty acids and docosahexaenoic acid (DHA), an EFA abundant in fish. Calanoids and cladocerans contained similar levels of eicosapentaenoic acid (EPA), but cladocerans showed EPA : DHA ratios consistently greater than those of the available seston food source. Alpha‐linolenic acid was most abundant in the herbivorous cladocerans, Daphnia and Holopedium, while the highest concentrations of arachidonic acid were found in the predatory cladocerans, Bythotrephes longimanus and Leptodora kindtii.

3. The distinct EFA accumulation patterns between cladoceran and copepod zooplankton suggest metabolic regulation of certain EFAs to meet the particular physiological demands and ecological strategies of these different zooplankton groups. Cladocerans may accumulate EPA directly from their diet, or through transformation of dietary materials to facilitate rapid somatic growth and enhance reproduction due to their short generation time. In contrast, copepods may retain DHA to increase their cell membrane fluidity in order to remain active over the winter due to their longer generation time and life cycle.

4. Consistent EFA differences between zooplankton groups may have implications regarding the somatic growth and reproductive success of different zooplankton taxa as well as the nutritional value of various zooplankton groups for larval and planktivorous fish.
Long‐term numerical changes and regulation in a river stock of European eelAnguilla anguilla
Authors: LOBÓN‐CERVIÁ JAVIER , IGLESIAS TANIA
Published: April 2008

1. The objective was to explore the regulatory mechanisms underlying the numerical dynamics of a river stock of European eelAnguilla anguillabased on a purely observational study. We used a 21‐year data set on the Rio Esva (Asturias, northwestern Spain) stock of eels, encompassing eel density at an estuary site and at nine sites distributed among three tributaries selected to differ in the distance from the tidal limit and fishery data on glass eels from the nearby Rio Nalón estuary.

2. The abundance of glass eels and estuarine and in‐stream densities declined simultaneously over a 15‐year period. However, following a historical minimum in the abundance of glass eels around the year 2000, the density continued to decline in the estuary whereas density in the streams began an increase that has continued to the present.

3. In‐stream cohort mortality rate (Z) varied from 0.0016 day−1to only 0.0003 day−1(on an annual basis from 0.57 to 0.099 year−1). The negative effects of intra‐cohort and inter‐cohort densities on mortality rate emphasized the responses of the riverine stock to compensatory density‐dependence. As a consequence, the number of eels surviving to commence the silvering stage was similar in magnitude in the strongest and weakest cohorts.

4. These results suggest that, even if the low abundance of glass eels persists, in‐stream density may increase towards a stable value regulated by in‐stream density‐dependence.
Partitioning net ecosystem carbon exchange and the carbon isotopic disequilibrium in a subalpine forest
Authors: ZOBITZ JOHN M. , BURNS SEAN P. , REICHSTEIN MARKUS , BOWLING DAVID R.
Published: April 2008

We investigate the utility of an improved isotopic method to partition the net ecosystem exchange of CO2 (F) into net photosynthesis (FA) and nonfoliar respiration (FR). Measurements of F and the carbon isotopic content in air at a high‐elevation coniferous forest (the Niwot Ridge AmeriFlux site) were used to partition F into FA and FR. Isotopically partitioned fluxes were then compared with an independent flux partitioning method that estimated gross photosynthesis (GEE) and total ecosystem respiration (TER) based on statistical regressions of night‐time F and air temperature. We compared the estimates of FA and FR with expected canopy physiological relationships with light (photosynthetically active radiation) and air temperature. Estimates of FA and GEE were dependent on light as expected, and TER, but not FR, exhibited the expected dependence on temperature. Estimates of the isotopic disequilibrium D, or the difference between the isotopic signatures of net photosynthesis (δA, mean value −24.6‰) and ecosystem respiration (δR, mean value −25.1‰) were generally positive (δA>δR). The sign of D observed here is inconsistent with many other studies. The key parameters of the improved isotopic flux partitioning method presented here are ecosystem scale mesophyll conductance (gm) and maximal vegetative stomatal conductance (gcmax). The sensitivity analyses of FA, FR, and D to gcmax indicated a critical value of gcmax (0.15 mol m−2 s−1) above which estimates of FA and FR became larger in magnitude relative to GEE and TER. The value of D decreased with increasing values of gm and gcmax, but was still positive across all values of gm and gcmax. We conclude that the characterization of canopy‐scale mesophyll and stomatal conductances are important for further progress with the isotope partitioning method, and to confirm our anomalous isotopic disequilibrium findings.
Impact of severe dry season on net ecosystem exchange in the Neotropical rainforest of French Guiana
Authors: BONAL DAMIEN , BOSC ALEXANDRE , PONTON STÉPHANE , GORET JEAN‐YVES , BURBAN BENOÎT , GROSS PATRICK , BONNEFOND JEAN‐MARC , ELBERS JAN , LONGDOZ BERNARD , EPRON DANIEL , GUEHL JEAN‐MARC , GRANIER ANDRÉ
Published: April 2008

The lack of information on the ways seasonal drought modifies the CO2 exchange between Neotropical rainforest ecosystems and the atmosphere and the resulting carbon balance hinders our ability to precisely predict how these ecosystems will respond as global environmental changes force them to face increasingly contrasting conditions in the future. To address this issue, seasonal variations in daily net ecosystem productivity (NEPd) and two main components of this productivity, daily total ecosystem respiration (REd) and daily gross ecosystem productivity (GEPd), were estimated over 2 years at a flux tower site in French Guiana, South America (5 °16′54″N, 52 °54′44″W). We compared seasonal variations between wet and dry periods and between dry periods of contrasting levels of intensity (i.e. mild vs. severe) during equivalent 93‐day periods. During the wet periods, the ecosystem was almost in balance with the atmosphere (storage of 9.0 g C m−2). Seasonal dry periods, regardless of their severity, are associated with higher incident radiation and lower REd combined with reduced soil respiration associated with low soil water availability. During the mild dry period, as is normally the case in this region, the amount of carbon stored in the ecosystem was 32.7 g C m−2. Severe drought conditions resulted in even lower REd, whereas the photosynthetic activity was only moderately reduced and no change in canopy structure was observed. Thus, the severe dry period was characterized by greater carbon storage (64.6 g C m−2), emphasizing that environmental conditions, such as during a severe drought, modify the CO2 exchange between Neotropical rainforest ecosystems and the atmosphere and potentially the resulting carbon balance.
Age‐dependent response of boreal forest to temperature and rainfall variability
Authors: McMILLAN ANDREW M. S. , WINSTON GREGORY C. , GOULDEN MICHAEL L.
Published: April 2008

We used measurements of CO2 exchange by six Canadian boreal forest stands to determine how sites of contrasting age respond to interannual temperature and precipitation variation. The stands ranged in age (time since last burn) from 4 to 155 years. The study included years that were anomalously cool and moist, warm and dry, cool and dry, and warm and moist. Warmer than average springs accelerated the onset of older stand (> 20 years) photosynthesis by as much as 37 days and younger stand (< 20 years) photosynthesis by as much as 25 days. The warm–dry year resulted in a marked reduction of mid‐summer CO2 uptake by the younger, but not older, stands. The mid‐summer decline in young stand photosynthesis reflected the combination of warmth and drought; similar declines were not observed during the cool–dry or warm–moist years. The annual carbon gain by the oldest stands was greatest during the warm–dry year as a result of the expanded growing season. The annual carbon gain by the youngest stands was consistent from year to year, largely as a result of offsets between increased spring photosynthesis and reduced mid‐summer photosynthesis during the warm–dry year. Night‐time CO2 efflux increased by 2–29% during the warm–moist year relative to the warm–dry year. This increase was not systematically related to age. We conclude that the major source of interannual CO2 exchange variation at the landscape scale is the ability of older, evergreen canopies to respond to warm springs by advancing the onset of photosynthesis. Drought‐related reductions in photosynthesis, moisture‐driven respiratory losses, and the effects of spring warmth on young‐stand photosynthesis are of secondary importance. The advantage conferred on older, evergreen stands during warmer years carries implications for the possible effects of climate change on boreal forest succession. Warmer temperatures may increase the competitive advantage of late successional species relative to early successional species, and also the incidence of fire, thereby accelerating plant succession and shortening the fire‐return interval.
Bird migration times, climate change, and changing population sizes
Authors: MILLER‐RUSHING ABRAHAM J. , LLOYD‐EVANS TREVOR L. , PRIMACK RICHARD B. , SATZINGER PAUL
Published: April 2008

Past studies of bird migration times have shown great variation in migratory responses to climate change. We used 33 years of bird capture data (1970–2002) from Manomet, Massachusetts to examine variation in spring migration times for 32 species of North American passerines. We found that changes in first arrival dates – the unit of observation used in most studies of bird migration times – often differ dramatically from changes in the mean arrival date of the migration cohort as a whole. In our study, the earliest recorded springtime arrival date for each species occurred 0.20 days later each decade. In contrast, the mean arrival dates for birds of each species occurred 0.78 days earlier each decade. The difference in the two trends was largely explained by declining migration cohort sizes, a factor not examined in many previous studies. We found that changes in migration cohort or population sizes may account for a substantial amount of the variation in previously documented changes in migration times. After controlling for changes in migration cohort size, we found that climate variables, migration distance, and date of migration explained portions of the variation in migratory changes over time. In particular, short‐distance migrants appeared to respond to changes in temperature, while mid‐distance migrants responded particularly strongly to changes in the Southern Oscillation Index. The migration times of long‐distance migrants tended not to change over time. Our findings suggest that previously reported changes in migration times may need to be reinterpreted to incorporate changes in migration cohort sizes.
Will climate change be beneficial or detrimental to the invasive swede midge in North America? Contrasting predictions using climate projections from different general circulation models
Authors: MIKA ANNA M. , WEISS ROSS M. , OLFERT OWEN , HALLETT REBECCA H. , NEWMAN JONATHAN A.
Published: April 2008

Climate change may dramatically affect the distribution and abundance of organisms. With the world's population size expected to increase significantly during the next 100 years, we need to know how climate change might impact our food production systems. In particular, we need estimates of how future climate might alter the distribution of agricultural pests. We used the climate projections from two general circulation models (GCMs) of global climate, the Canadian Centre for Climate Modelling and Analysis GCM (CGCM2) and the Hadley Centre model (HadCM3), for the A2 and B2 scenarios from the Special Report on Emissions Scenarios in conjunction with a previously published bioclimatic envelope model (BEM) to predict the potential changes in distribution and abundance of the swede midge, Contarinia nasturtii, in North America. The BEM in conjunction with either GCM predicted that C. nasturtii would spread from its current initial invasion in southern Ontario and northwestern New York State into the Canadian prairies, northern Canada, and midwestern United States, but the magnitude of risk depended strongly on the GCM and the scenario used. When the CGCM2 projections were used, the BEM predicted an extensive shift in the location of the midges' climatic envelope through most of Ontario, Quebec, and the maritime and prairie provinces by the 2080s. In the United States, C. nasturtii was predicted to spread to all the Great Lake states, into midwestern states as far south as Colorado, and west into Washington State. When the HadCM3 was applied, southern Ontario, Saskatchewan, and Washington State were not as favourable for C. nasturtii by the 2080s. Indeed, when used with the HadCM3 climate projections, the BEM predicted the virtual disappearance of ‘very favourable’ regions for C. nasturtii. The CGCM2 projections generally caused the BEM to predict a small increase in the mean number of midge generations throughout the course of the century, whereas, the HadCM3 projections resulted in roughly the same mean number of generations but decreased variance. Predictions of the likely potential of C. nasturtii spatial spread are thus strongly dependent on the source of climate projections. This study illustrates the importance of using multiple GCMs in combination with multiple scenarios when studying the potential for spatial spread of an organism in response to climate change.
Quantitative trait loci affecting stomatal density and growth in a Quercus robur progeny: implications for the adaptation to changing environments
Authors: GAILING OLIVER , LANGENFELD‐HEYSER ROSEMARIE , POLLE ANDREA , FINKELDEY REINER
Published: April 2008

Stomatal traits are important to cope with changes in levels of atmospheric carbon dioxide (CO2) and with changing availability of water. Thus, they are expected to be involved in the reactions of plants to climate change. They are known to show a plastic physiological response to environmental factors such as elevated CO2 concentrations, but they are also under genetic control and should undergo evolutionary change if selection differs among environments. Stomatal development is regulated by several environmental and genetic signals suggesting a polygenic inheritance. In the present study, F1 progeny derived from a cross between Quercus robur and Q. robur subsp. slavonica were used to map QTLs (quantitative trait loci) for stomatal densities and growth parameters under nonwater stress conditions in 2 and 3 consecutive years, respectively. The positions of QTLs for stomatal density and growth coincided on six linkage groups. The QTL allele associated with the higher stomatal density was generally associated with taller plants and size increment indicating pleiotropic gene effects or close linkage. The phenotypic effects of the individual QTLs were mostly moderate in terms of phenotypic variance explained. However, a considerable amount of the genetically determined variation was explained by QTLs for stomatal density (from 63.6% to 94.4%). Especially, the QTL on linkage group 11 had a strong and highly significant effect on stomatal densities and growth parameters in all years suggesting a major QTL on this linkage group. The importance to analyse the genetic variation controlling complex adaptive traits in keystone species as oaks is discussed with regard to a better understanding of the reactions of ecosystems to global change.
Climatic effects on the breeding phenology and reproductive success of an arctic‐nesting goose species
Authors: DICKEY MARIE‐HÉLÈNE , GAUTHIER GILLES , CADIEUX MARIE‐CHRISTINE
Published: April 2008

Climate warming is pronounced in the Arctic and migratory birds are expected to be among the most affected species. We examined the effects of local and regional climatic variations on the breeding phenology and reproductive success of greater snow geese (Chen caerulescens atlantica), a migratory species nesting in the Canadian Arctic. We used a long‐term dataset based on the monitoring of 5447 nests and the measurements of 19 234 goslings over 16 years (1989–2004) on Bylot Island. About 50% of variation in the reproductive phenology of individuals was explained by spring climatic factors. High mean temperatures and, to a lesser extent, low snow cover in spring were associated with an increase in nest density and early egg‐laying and hatching dates. High temperature in spring and high early summer rainfall were positively related to nesting success. These effects may result from a reduction in egg predation rate when the density of nesting geese is high and when increased water availability allows females to stay close to their nest during incubation recesses. Summer brood loss and production of young at the end of the summer increased when values of the summer Arctic Oscillation (AO) index were either very positive (low temperatures) or very negative (high temperatures), indicating that these components of the breeding success were most influenced by the regional summer climate. Gosling mass and size near fledging were reduced in years with high spring temperatures. This effect is likely due to a reduced availability of high quality food in years with early spring, either due to food depletion resulting from high brood density or a mismatch between hatching date of goslings and the timing of the peak of plant quality. Our analysis suggests that climate warming should advance the reproductive phenology of geese, but that high spring temperatures and extreme values of the summer AO index may decrease their reproductive success up to fledging.
Capacitation‐associated changes in membrane fluidity in asthenozoospermic human spermatozoa
Authors: Buffone Mariano G. , Doncel Gustavo F. , Calamera Juan C. , Verstraeten Sandra V.
Published: April 2008

The fertilizing potential of human spermatozoa relies on their ability to capacitate as they travel through the female reproductive tract. During this process, cholesterol is released from the plasma membrane, altering its architecture and dynamics. Using ISolate® gradients, we obtained high (L90)‐ and low (L45)‐quality spermatozoa from asthenozoospermic human semen samples. We tested the hypothesis that the lower fertilizing ability of asthenozoospermic L90 cells could be related to a lower ability to increase their membrane fluidity during capacitation. We assessed two sets of fluorescent probes: (i) DPH, TMA‐DPH and PA‐DPH which senses the hydrophobic core, cytosolic and exofacial leaflets of the bilayer, respectively and (ii) Laurdan, sensitive to the amount of water molecules intercalated between lipid moieties of the membrane (membrane hydration). Before capacitation, membrane fluidity of asthenozoospermic sperm populations was similar to the corresponding fractions of normozoospermic cells when evaluated with DPH, TMA‐DPH or PA‐DPH. Asthenozoospermic whole samples displayed lower plasma membrane hydration than normozoospermic cells as evidenced with Laurdan. After capacitation, asthenozoospermic L45 and L90 cells failed to increase their membrane fluidity in opposition to normozoospermic cells. Interestingly, membrane hydration significantly correlated with the main sperm motion parameters analysed, being a low membrane hydration associated with poor sperm movement. These results show that low‐motility spermatozoa are unable to respond to capacitation with the necessary changes in membrane fluidity. This defect in sperm plasma membrane rheology may be responsible for their poor functional quality and low fertilizing ability.