bluuebunny/crossref_metadata_2025 huggingface dataset:
Radial growth and climate responses of white oak (Quercus alba) and northern red oak (Quercus rubra) at the northern distribution limit of white oak in Quebec, Canada
Authors: Tardif J. C. , Conciatori F. , Nantel P. , Gagnon D.
Published: June 2006

Aim The objectives of this study were: (1) to compare radial growth patterns between white oak (Quercus albaL.) and northern red oak (Quercus rubraL.) growing at the northern distribution limit of white oak; and (2) to assess if the radial growth of white oak at its northern distribution limit is controlled by cold temperature.

Location The study was conducted in three regions of the Ottawa valley in southern Québec. All stands selected were located at the northern limit of distribution ofQ. alba.

Methods Twelve mixed red and white oak stands were sampled and increment cores were extracted for radial growth analyses. For each oak species, 12 chronologies were derived from tree‐ring measurement (residual chronologies). Principal components analysis and redundancy analysis were used to highlight the difference between radial growth in both species and to determine their radial growth–climate association.

Results There was little difference between the radial growth of each species;Q. alba, however, exhibits more year‐to‐year variation in growth thanQ. rubra. More than 65% of the variance in radial growth was shared among sites and species. Both species showed a similar response to climate, which suggested that the limit of distribution ofQ. albamight not be determined by effects on growth. Both species had a classic response to climate and drought in the early growing season.

Main conclusions The northern distribution limit ofQ. albadoes not appear to be directly controlled by effects on growth processes as indicated by the similarities in radial growth and response to climate between the two species. The location of the stands on southern aspects suggested that cold temperature could have been a major factor controlling the distribution limit ofQ. alba. However, it is speculated that stands growing on southern aspects may be more prone to forest fires or to drought, which would favour the maintenance and establishment of oaks, and ofQ. albain particular. Models relating the northern distribution limits of species to broad climate parameters like annual mean temperature will need to be reviewed to incorporate more biologically relevant information. Such assessments will in turn provide better estimates of the effect of climate changes on species distribution.
Evaluation of a nurse consultant's clinical activities and the search for patient outcomes in critical care
Authors: Fairley Debra , Closs S. Jose
Published: June 2006

Aim.  To describe the actual clinical activities undertaken by a critical care nurse consultant in an eight‐bedded adult surgical high dependency unit within a large NHS Teaching Hospitals NHS Trust.

Background.  In the United Kingdom, the first critical care nurse consultants were approved in 2000 following the Department of Health's (1999) revised career structure for nurses. Expert practice is a core function of the role although the nature of expert practice in the context of critical care is unclear. Expert practice is often deemed to be a feature of advanced practice and although a number of studies have investigated this in context of critical care, there is little insight into the nature of advanced practitioners’ clinical practice and how it might influence patient outcome.

Design methods.  A diary was used by a critical care nurse consultant to record activity during scheduled clinical sessions. Data were collected for four months: 39 sessions were evaluated. Qualitative data were content analysed and coded into categories. Clinical activities were coded, categorized and analysed using SPSS 11.0 for windows (SPSS Inc., Chicago, IL, USA).

Findings.  Clinical activities included direct care activities, clinical leadership, education and training. Two main themes emerged from the qualitative data and were categorized as clinical reasoning and clinical instruction. Clinical activities arising from clinical reasoning and clinical instruction were aimed at minimizing risk and the provision of quality care. In doing this, one of the outcomes was the detection and resolution of untoward clinical occurrences.

Conclusion.  The level of achievement – or end point – of clinical activities was that the patient was established in ‘a state free from risk or harm that optimises rehabilitation’. ‘A state free from risk or harm that optimizes rehabilitation’ might be one outcome reflecting the needs of individual critically ill patients that is sensitive to individual nursing contribution.

Relevance to clinical practice.  There is increasing pressure on health‐care professionals to identify and measure their individual impact on the outcome of patients. This study adds further insight into the complexities associated with evaluating the influence of individual contribution on patient outcome, especially when it is characterized by complex processes involving clinical judgement and decision‐making.
Change on the horizon: issues and concerns of neophyte advanced healthcare practitioners
Authors: Williamson Graham R , Webb Christine , Abelson‐Mitchell Nadine , Cooper Simon
Published: June 2006

Aims and objectives.  The aim was to interview new entrants to a Master's level programme of educational preparation for advanced healthcare practice roles. The objectives were to gain an understanding of their issues and concerns as they looked ahead to their future development and to illuminate issues concerning their experiences as students and as employees.

Background.  As advanced practice roles become more widespread in the United Kingdom and abroad, nurses and other healthcare professionals are becoming more involved in innovation and service development and experiencing greater autonomy in many areas, particularly in regard to clinical examination and diagnosis.

Design.  A qualitative design was employed to illuminate issues and concerns of new students on a Master's degree programme of educational preparation for advanced healthcare practitioners.

Methods.  Two focus group interviews were conducted in 2004. Sixteen students from two programme cohorts participated in the two groups.

Findings.  Two main themes were outlined. These were: ‘opportunities for development’ and ‘time pressures’. Subcategories within these two themes are also discussed.

Conclusions.  Students undertaking Master's level preparation for advanced healthcare practitioner roles perceive personal and professional benefits and opportunities to develop innovative services to improve patient care as accruing from the programme. These opportunities and benefits were related to the United Kingdom national health policy agenda. Some role difficulties were experienced. The additional burdens that the programme of study provided were an issue for some, but these were perceived as a temporary problem, worth undergoing for the likely long‐term benefits.

Relevance to clinical practice.  Students undertaking educational preparation for advanced practice roles see themselves as innovators, specifically aiming to develop and improve aspects of service provision. Education for advanced practice roles should not be undertaken lightly, but can equip students with various skills, particularly regarding clinical assessment, and these skills should underpin practitioners’ autonomy.
The Legionella pneumophila IcmS–LvgA protein complex is important for Dot/Icm‐dependent intracellular growth
Authors: Vincent Carr D. , Vogel Joseph P.
Published: June 2006

Many bacterial pathogens require a functional type IV secretion system (T4SS) for virulence. Legionella pneumophila, the causative agent of Legionnaires' disease, employs the Dot/Icm T4SS to inject a large number of protein substrates into its host, thereby altering phagosome trafficking. The L. pneumophila T4SS substrate SdeA has been shown to require the accessory factor IcmS for its export. IcmS, defined as a type IV adaptor, exists as a heterodimer with IcmW and this complex functions in a manner similar to a type III secretion chaperone. Here we report an interaction between IcmS and the previously identified virulence factor LvgA. Similar to the icmS mutant, the lvgA mutant appears to assemble a fully functional Dot/Icm complex. Both LvgA and IcmS are small, acidic proteins localized to the cytoplasm and are not exported by the Dot/Icm system, suggesting they form a novel type IV adaptor complex. Inactivation of lvgA causes a minimal defect in growth in the human monocytic cell line U937 and the environmental host Acanthamoeba castellanii. However, the lvgA mutant was severely attenuated for intracellular growth of L. pneumophila in mouse macrophages, suggesting LvgA may be a critical factor that confers host specificity.
An rplKΔ29‐PALG‐32 mutation leads to reduced expression of the regulatory genes ccaR and claR and very low transcription of the ceaS2 gene for clavulanic acid biosynthesis in Streptomyces clavuligerus
Authors: Gomez‐Escribano Juan Pablo , Liras Paloma , Pisabarro Agustín , Martín Juan F.
Published: June 2006

The transcriptional and translational control of the biosynthesis of the β‐lactamase inhibitor clavulanic acid is a subject of great scientific and industrial interest. To study the role of the ribosomal protein L11 on control of clavulanic acid gene transcription, the DNA region aspC‐tRNAtrp‐secE‐rplK‐rplA‐rplJ‐rplL of Streptomyces clavuligerus was cloned and characterized. An S. clavuligerus rplKΔPALG mutant, with an internal 12 nucleotides in‐frame deletion in the rplK gene, encoding the L11 (RplK) ribosomal protein lacking amino acids 29PALG32, was constructed by gene replacement. This deletion alters the L11 N‐terminal domain that interacts with the RelA and class I releasing factors‐mediated translational termination. The mutant grew well, showed threefold higher resistance to thiostrepton, did not form spores and lacked diffusible brown pigments, as compared with the wild‐type strain. The wild‐type phenotype was recovered by complementation with the native rplK gene. S. clavuligerus rplKΔPALG produced reduced levels of clavulanic acid (15–26% as compared with the wild type) and cephamycin C (40–50%) in cultures grown in defined SA and complex TSB media. The decreased yields resulted from an impaired transcription of the regulatory genes ccaR and claR and the cefD and ceaS2 genes for cephamycin and clavulanic acid biosynthesis respectively. Expression of ceaS2 encoding carboxyethylarginine synthase (CEAS), the precursor‐committing enzyme for clavulanic acid biosynthesis, was particularly affected in this mutant. In the wild‐type strain polyphosphorylated nucleotides peaked at 36–48 h of growth in SA cultures whereas expression of the cephamycin and clavulanic acid genes occurred 12–24 h earlier than the increase in ppGpp indicating that there is no strict correlation between the peak of ppGpp and the onset of transcription of the clavulanic acid and cephamycin C biosynthesis. The drastic effect of the rplKΔPALG mutation on the onset of expression of the ceaS2 and the regulatory ccaR and claR genes and the lack of correlation with ppGpp levels suggest that the onset of transcription of these genes is modulated by the conformational alteration of the N‐terminal region of L11 probably by interaction with the nascent peptide releasing factors and with RelA.
Effects of Rubisco kinetics and Rubisco activation state on the temperature dependence of the photosynthetic rate in spinach leaves from contrasting growth temperatures
Authors: YAMORI WATARU , SUZUKI KENSAKU , NOGUCHI KO , NAKAI MASATO , TERASHIMA ICHIRO
Published: June 2006

Recently, several studies reported that the optimum temperature for the initial slope [IS(Ci)] of the light‐saturated photosynthetic rate (A) versus intercellular CO2 concentration (Ci) curve changed, depending on the growth temperature. However, few studies compare IS(Ci) with ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) properties. Here, we assessed Rubisco activation state and in vitro Rubisco kinetics, the main determinants of IS(Ci), in spinach leaves grown at 30/25 [high temperature (HT)] and 15/10 °C [low temperature (LT)]. We measured Rubisco activation state and A at a CO2 concentration of 360 µL L−1 (A360) at various temperatures. In both HT and LT leaves, the Rubisco activation state decreased with increasing temperatures above the optimum temperatures for A360, while the activation state remained high at lower temperatures. To compare Rubisco characteristics, temperature dependences of the maximum rate of ribulose 1,5‐bisphosphate (RuBP) carboxylation (Vcmax), specificity factor (Sc/o) and thermal stability were examined. We also examined Vcmax and thermal stability in the leaves that were transferred from HT to LT conditions and were subsequently kept under LT conditions for 2 weeks (HL). Rubisco purified from HT, LT and HL leaves are called HT, LT and HL Rubisco, respectively. Thermal stabilities of LT and HL Rubisco were similar and lower than that of HT Rubisco. Both Vcmax and Sc/o in LT Rubisco were higher than those of HT Rubisco at low temperatures, while these were lower at high temperatures. Vcmax in HL Rubisco were similar to those of LT Rubisco at low temperatures, and to those of HT Rubisco at high temperatures. The predicted photosynthetic rates, taking account of the Rubisco kinetics and the Rubisco activation state, agreed well with A360 in both HT and LT leaves. This study suggests that photosynthetic performance is largely determined by the Rubisco kinetics at low temperature and by Rubisco Kinetics and the Rubisco activation state at high temperature.
Mathematical review of literature to assess alternative electron transports and interphotosystem excitation partitioning of steady‐state C3photosynthesis under limiting light
Authors: YIN XINYOU , HARBINSON JEREMY , STRUIK PAUL C.
Published: June 2006

Linear whole‐chain electron (e–) transport plays a dominant role in generating NADPH and ATP required for carbon fixation in chloroplasts. However, other e–pathways may be present to contribute to the flexibility of e–transport in meeting demands by various downstream metabolic processes. The estimation of the fluxes of these alternative pathwaysin vivois difficult, as they are not amenable to direct experimental measurement. A recently developed model based on the generalized stoichiometry for the chloroplast e–transport pathways makes it possible to indirectly but quantitatively assess the fractions of e–that follow the alternative pathways. This model approach is used to review data from the literature on concurrent measurements of gas exchange and chlorophyll (Chl) fluorescence under steady‐state, limiting light, non‐photorespiratory conditions. The review suggests possiblein vivooccurrence of cyclic e–transport (CET) under such conditions. About 10% of e–from the reduced ferredoxin follow the pseudocyclic mode, notably in support of nitrate reduction. The estimated fraction of e–from the reduced plastoquinone that follows the Q‐cycle (fQ) depends on the number of protons required per ATP synthesis. Our model approach also allows the excitation partitioning to photosystem II (PSII) to be assessed quantitatively. Most important, the model helps assess the limit value to uncertain physiological parameters and answer the ‘what‐if’ question with regard to the effect of non‐measured processes or measurement uncertainties on the estimations of alternative e–transports.
On the induction of volatile organic compound emissions by plants as consequence of wounding or fluctuations of light and temperature
Authors: LORETO FRANCESCO , BARTA CSENGELE , BRILLI FEDERICO , NOGUES ISABEL
Published: June 2006

Among the volatile organic compounds (VOCs) emitted by plants, some are characteristic of stress conditions, but their biosynthesis and the metabolic and environmental control over the emission are still unclear. We performed experiments to clarify whether (1) the emission following wounding can occur at distance from the wounding site, from VOC pools subjected to metabolic signals; and (2) the emission of biogenic VOCs generated by membrane damage (e.g. consequent to wounding or ozone exposure) can also be induced by exposure to high light and high temperature, recurrent in nature. In Phragmites australis, leaf cutting caused large and rapid bursts of acetaldehyde both at the cutting site and on parts of the cut leaf distant from the cutting site. This emission was preceded by a transient stomatal opening and did not occur in conditions preventing stomatal opening. This suggests the presence of a large pool of leaf acetaldehyde whose release is under stomatal control. VOCs other than isoprene, particularly acetaldehyde and (E)‐2‐hexenal, one of the C‐6 compounds formed by the denaturation of membrane lipids, were released by leaves exposed to high temperature and high light. The high‐temperature treatment (45 °C) also caused a rapid stimulation and then a decay of isoprene emission in Phragmites leaves. Isoprene recovered to the original emission level after suspending the high‐temperature treatment, suggesting a temporary deficit of photosynthetically formed substrate under high temperature. Emission of C‐6 compounds was slowly induced by high temperature, and remained high, indicating that membrane denaturation occurs also after suspending the high‐temperature treatment. Conversely, the emission of C‐6 compounds was limited to the high‐light episode in Phragmites. This suggests that a membrane denaturation may also occur in conditions that do not damage other important plant processes such as the photochemistry of photosynthesis of photoinhibition‐insensitive plants. In the photoinhibition‐sensitive Arabidopsis thaliana mutant NPQ1, a large but transient emission of (E)‐2‐hexenal was also observed a few minutes after the high‐light treatment, indicating extensive damage to the membranes. However, (E)‐2‐hexenal emission was not observed in Arabidopsis plants fumigated with isoprene during the high‐light treatment. This confirms that isoprene can effectively protect cellular membranes from denaturation. Our study indicates that large, though often transient, VOC emissions by plants occur in nature. In particular, we demonstrate that VOCs can be released by much larger tissues than those wounded and that even fluctuations of light and temperature regularly observed in nature can induce their emissions. This knowledge adds information that is useful for the parameterization of the emissions and for the estimate of biogenic VOC load in the atmosphere.
Variation in feeding rate of the intertidal mudsnail Hydrobia ulvae in relation to the tidal cycle
Authors: Barnes Richard S. K.
Published: June 2006

Deposit feeding in the coastal epibenthic mudsnail Hydrobia ulvae, as estimated by egestion rate, varies in relation to the tidal cycle. In nature, feeding is maximal when the snails are covered by tidal water; after exposure, feeding reduces slightly but significantly whilst the sediment surface remains damp; and it is minor or ceases whilst the snails are buried in pits in the drying sediment. Within each of these three phases, however, egestion rate remains unchanged both in relation to phase duration, and with temperature over an ambient range of 18–30 °C (mean 24 °C). These findings form another example of disagreement between field and laboratory results on feeding in Hydrobia.
Variability in the nutritional value of the major copepods in Cape Cod Bay (Massachusetts, USA) with implications for right whales
Authors: DeLorenzo Costa Amy , Durbin Edward G. , Mayo Charles A.
Published: June 2006

The North Atlantic right whale, a seriously endangered species, is found in Cape Cod Bay (Massachusetts, USA) during the winter and early spring. During their residency in these waters, these whales are frequently observed feeding. This study evaluated spatial and temporal changes in the chemical composition (carbon weight and C/N ratio) of the food resource targeted by the right whales in Cape Cod Bay. The three taxa measured (Centropages typicus, Pseudocalanus spp., and Calanus finmarchicus) had highly variable chemical compositions resulting from the different life strategies and from fluctuations in their surrounding environment. The impact of seasonal variability in the energy densities of the food resource of right whales was calculated and compared to the energetic requirements of these whales. Calculations indicated that differences in the nutritional content of the zooplankton prey in Cape Cod Bay could have a considerable effect on the nutrition available to the right whales. Therefore, it is likely that using more precise estimates of the energetic densities of the prey of right whales would lead to a re‐evaluation of the adequacy of the food resource available to these whales in the North Atlantic.
A case study of mollusc and polychaete soft‐bottom assemblages submitted to sedimentary instability in the Mediterranean Sea
Authors: Cosentino Andrea , Giacobbe Salvatore
Published: June 2006

In the Strait of Messina (Sicily, Central Mediterranean Sea) strong tidal currents, very irregular hydrological regime and related solid load, and local seismic activity cause sediment instability; this area represents therefore a case‐study of a naturally disturbed soft‐bottom environment. In this paper, mollusc and polychaete assemblages of the northern part of the Strait were described. Composition, community structure, eco‐ethological features, trophic guilds and sediment‐type relationships were studied in 64 stations sampled located between 3.5 and 50 m depth in October 1992 by means of a Van Veen grab. A total of 131 species (65 molluscs and 66 polychaetes) were identified. A dense population of the tubicolous polychaete Ditrupa arietina was recognized, together with the occurrence of other species tied to a high sedimentation rate, such as Corbula gibba and Tellina distorta, as well as widespread, mud‐tolerant species (e.g.Chone spp., Hyalinoecia tubicola). Diversity (H′) showed a peak at intermediate depths (10/20 m) and a clear decrease beyond this depth, corresponding to the Ditrupa core population. Multivariate comparison between sediment features and community composition throughout the bathymetric gradient showed a narrow ecocline between two environments subjected to opposite hydrodynamic constraints. In the shallower zone, a wide typology of trophic‐ethological guilds was related to community patchiness, in contrast to a greater functional uniformity of the deeper assemblage, dominated by sessile, semi‐infaunal suspension feeders. A possible role played by a phase of increased rainfall to increase bottom instability, locally emphasized by a previous human activity, is also discussed.
Temporal dynamics of subtidal Zostera marina and intertidal Zostera japonica on the southern coast of Korea
Authors: Lee Sang Yong , Kim Jeong Bae , Lee Sung Mi
Published: June 2006

The temporal dynamics of two seagrass species, Zostera marina and Z. japonica, were monitored monthly in Dadae Bay, Geoje Island, on the southern coast of Korea. Plant morphological characteristics, shoot density, biomass, leaf production, reproductive effort, and environmental characteristics were monitored from July 2001 to July 2002. Zostera japonica occurred in the intertidal zone and Z. marina occurred in the subtidal zone from 0.5 to 2.5 m below the mean low water level. Shoots and rhizomes were significantly larger in Z. marina than in Z. japonica, whereas the shoot density was greater in Z. japonica than in Z. marina. Despite differences in morphology and shoot density, biomass did not differ significantly between the species. Reproduction occurred from April to June in Z. marina and from May to July in Z. japonica. The proportion of reproductive shoots was approximately three times higher in Z. marina than in Z. japonica. Seasonal variation in the biomass of Z. japonica was caused by changes in both shoot size and density, whereas that of Z. marina was mainly caused by changes in shoot length. Leaf production in Z. marina and Z. japonica showed clear seasonal variation, and leaf production in Z. marina (2.6 ± 0.2 g DW·m−2·day−1) was higher than that in Z. japonica (1.7 ± 0.2 g DW·m−2·day−1). The mean plastochrone interval was not significantly different between the two species, whereas the leaf lifetime of Z. marina was longer (69 ± 7.8 days) than that of Z. japonica (59 ± 8.3 days). Our results indicated that seasonal leaf growth patterns in Z. japonica are correlated with irradiance and temperature, whereas those in Z. marina respond most to irradiance. Seasonal changes in irradiance appeared to control the temporal variation in above‐ground biomass in both species.
Annual variability of planktonic ostracods (Crustacea) in the South Adriatic Sea
Authors: Brautović Igor , Bojanić Natalia , Batistić Mirna , Carić Marina
Published: June 2006

Temporal variability and population structure of planktonic ostracods were investigated for the first time in the South Adriatic Sea during 1996. The maximal total ostracod abundance (1167 ind·100 m−3; 69% juveniles, 18% females and 13% males) was recorded in February. Thirteen species of marine planktonic ostracods were identified. Porroecia spinirostris and Archiconchoecia striata dominated the ostracod assemblage, accounting respectively for 62% and 18% of the total abundance. Their annual peaks were recorded during the cold season, which was the period of their intense reproduction, with favourable temperature conditions and lack of predators. The females surpassed the males in abundance in most species. The presence of the mesopelagic species indicated a strong influence of intermediate layer water masses from the Eastern Mediterranean Sea.
Effects of temporal dynamics and vertical structure of the seagrassZostera caulescenson distribution and recruitment of the epifaunal encrusting bryozoaMicroporella trigonellata
Authors: Kouchi Naoko , Nakaoka Masahiro , Mukai Hiroshi
Published: June 2006

Seagrass is an ephemeral habitat for epifaunal sessile invertebrates attaching on seagrass leaves, and spatial and temporal dynamics of seagrasses strongly affect the distribution of epifauna.Zostera caulescensMiki, a seagrass species endemic to Japan, provides a complex habitat for epifauna with two types of shoots: vegetative, less than 1 m tall, and flowering, 5–7 m tall. We conducted monthly field observations and a manipulative field experiment to investigate the effects of the seagrass vertical structure and its temporal variation on the distribution and recruitment of the encrusting bryozoanMicroporella trigonellata. The density ofM. trigonellataon the leaves of flowering shoots, located at the seagrass canopy, varied temporally, reaching maximum in summer and minimum in winter. In contrast,M. trigonellatadensity on the leaves of vegetative shoots near the sea floor was consistently low throughout the study period. Early recruit bryozoans also showed this temporal and vertical variation in density; thus spatial and temporal variation in recruitment determined the distribution of the whole colonies. The field experiment revealed that the recruitment rate ofM. trigonellatawas significantly higher at the higher position of the water column (3 m above the sea floor) than at the lower position (0.5 m) in June. However, the recruitment rate was higher at the lower position in October when most of the flowering shoots started falling down. The temporal change in bryozoan habitat selection is considered to be adaptive to maintain their population on the seagrass leaves that show complex temporal dynamics.
Community structure of macrobenthos in two tropical sandy beaches with different morphodynamic features, Rio de Janeiro, Brazil
Authors: Fernandes Renata Soares Ramalho , Soares‐Gomes Abilio
Published: June 2006

The macrobenthos of two exposed tropical sandy beaches in Rio de Janeiro (Brazil) were compared in relation to density, species richness, and vertical zonation. Biological and sediment samplings were carried out in the austral winter of 2002 and the austral summer of 2003. The sampling design consisted of 10 transects perpendicular to the water line, evenly divided into strata. A sampling unit was taken in each stratum with a 0.04 m2 quadrat sampler. Beaches were also compared according to physical features, such as slope, wave period, wave height, and grain size. According to Dean's Ω morphodynamic index the Pontal is a dissipative beach while the Costa Azul is a reflective one. The mean grain size ranged from median to coarse sand in Costa Azul, whereas in Pontal it ranged from median to very fine sand. Eleven species were collected in the two beaches. Crustaceans were the dominant in the Costa Azul Beach, while the polychaete Scolelepis squamata dominated the Pontal beach. A negative correlation was found between the density of the macrobenthos and mean grain size, and beach slope. On the other hand, the Dean's parameter correlated positively with faunal density. Based on the results of ANOSIM, in both beaches, two groups of stations were identified, defining an upper and a lower beach zone along the vertical distribution of the macrobenthos.
Biofilm formation and cellulose expression among diverse environmental Pseudomonas isolates
Authors: Ude Susanne , Arnold Dawn L. , Moon Christina D. , Timms‐Wilson Tracey , Spiers Andrew J.
Published: June 2006

The ability to form biofilms is seen as an increasingly important colonization strategy among both pathogenic and environmental bacteria. A survey of 185 plant‐associated, phytopathogenic, soil and river Pseudomonas isolates resulted in 76% producing biofilms at the air–liquid (A–L) interface after selection in static microcosms. Considerable variation in biofilm phenotype was observed, including waxy aggregations, viscous and floccular masses, and physically cohesive biofilms with continuously varying strengths over 1500‐fold. Calcofluor epifluorescent microscopy identified cellulose as the matrix component in biofilms produced by Pseudomonas asplenii, Pseudomonas corrugata, Pseudomonas fluorescens, Pseudomonas marginalis, Pseudomonas putida, Pseudomonas savastanoi and Pseudomonas syringae isolates. Cellulose expression and biofilm formation could be induced by the constitutively active WspR19 mutant of the cyclic‐di‐GMP‐associated, GGDEF domain‐containing response regulator involved in the P. fluorescens SBW25 wrinkly spreader phenotype and cellular aggregation in Pseudomonas aeruginosa PA01. WspR19 could also induce P. putida KT2440, which otherwise did not produce a biofilm or express cellulose, as well as Escherichia coli K12 and Salmonella typhimurium LT2, both of which express cellulose yet lack WspR homologues. Statistical analysis of biofilm parameters suggest that biofilm development is a more complex process than that simply described by the production of attachment and matrix components and bacterial growth. This complexity was also seen in multivariate analysis as a species‐ecological habitat effect, underscoring the fact that in vitro biofilms are abstractions of those surface and volume colonization processes used by bacteria in their natural environments.
The incidence of nirS and nirK and their genetic heterogeneity in cultivated denitrifiers
Authors: Heylen Kim , Gevers Dirk , Vanparys Bram , Wittebolle Lieven , Geets Joke , Boon Nico , De Vos Paul
Published: June 2006

Gene sequence analysis of nirS and nirK, both encoding nitrite reductases, was performed on cultivated denitrifiers to assess their incidence in different bacterial taxa and their taxonomical value. Almost half of the 227 investigated denitrifying strains did not render an nir amplicon with any of five previously described primers. NirK and nirS were found to be prevalent in Alphaproteobacteria and Betaproteobacteria, respectively, nirK was detected in the Firmicutes and Bacteroidetes and nirS and nirK with equal frequency in the Gammaproteobacteria. These observations deviated from the hitherto reported incidence of nir genes in bacterial taxa. NirS gene phylogeny was congruent with the 16S rRNA gene phylogeny on family or genus level, although some strains did group within clusters of other bacterial classes. Phylogenetic nirK gene sequence analysis was incongruent with the 16S rRNA gene phylogeny. NirK sequences were also found to be significantly more similar to nirK sequences from the same habitat than to nirK sequences retrieved from highly related taxa. This study supports the hypothesis that horizontal gene transfer events of denitrification genes have occurred and underlines that denitrification genes should not be linked with organism diversity of denitrifiers in cultivation‐independent studies.
Towards European climate risk surfaces: the extent and distribution of analogous and non‐analogous climates 1931–2100
Authors: Ohlemüller Ralf , Gritti Emmanuel S. , Sykes Martin T. , Thomas Chris D.
Published: June 2006

Aim  Climate is an important determinant of species distributions. We assess different aspects of risk arising from future climate change by quantifying changes in the spatial distribution of future climatic conditions compared with the recent past.

Location  Europe.

Methods  A 10′ × 10′ resolution gridded data set of five climate variables was used to calculate expected changes to the area, distance and direction of 1931–60 climatic conditions under the HadCM3 climate model for four future climate scenarios based on different rates of greenhouse gas emissions (SRES scenarios). Three levels of tolerance ranges determined the thresholds for which future conditions are considered analogous to 1931–60 (pre‐warming) conditions.

Results  For many parts of Europe, areas with pre‐warming analogous climate conditions will be smaller and further away in the future than they are now. For any location in Europe, areas with pre‐warming analogous mean annual temperature conditions will, on average, be reduced between 23.7% (B1 scenario) and 49.7% (A1FI scenario) by 2100 when assuming a medium tolerance range. The mean distance to these areas will, on average, increase between 272 km (B1) and 645 km (A1FI). These changes are more pronounced for temperature than for water availability variables and also for narrow tolerance ranges compared to wide tolerance ranges. Using a combined measure of both temperature and precipitation variables, areas with prewarming analogous conditions are predicted to be in a more northeasterly direction in the future, but there are considerable regional differences within Europe.

Main conclusions  The results suggest that, for some parts of Europe, the loss of area with any suitable climatic conditions represents the greatest risk to biodiversity, but in other regions the distances that species may have to move to reach suitable climatic conditions may be a greater problem. Quantifying the distance and direction in analyses of change of climatically suitable areas can add additional information for climate change risk assessments.
Innovation Speed in Small and Medium‐Sized Enterprises
Authors: Allocca Michael A. , Kessler Eric H.
Published: June 2006

In this era of fast‐paced technological change companies are frequently forced to quickly bring innovative products to a competitive marketplace. Small and medium‐sized enterprises (SMEs) play a key role in innovative contribution and growth of the global economy, yet face unique challenges with regard to new product development. To date scholars disagree on the effect of firm size on the antecedents and outcomes for innovation speed. We review the relevant literature, develop a conceptual model of innovation speed for SMEs and test it with 158 projects across several technology‐related industries. Results revealed that SMEs had different speed antecedents from large firms, had their antecedents vary by radicalness and found speed to be synergistic with efficiency, quality and project success. Implications for managers and scholars are discussed.
Misleading Inferences from Panel Unit Root Tests: a Reply*
Authors: Breuer Janice Boucher , McNown Robert , Wallace Myles
Published: June 2006

Ford et al. (this issue) point out that the SURADF panel unit root test may be sensitive to panel composition. This reply shows that they overstate the case since they focus on a short time series of 44 observations. Type II errors are much more likely in this environment so that inconsistent conclusions may arise for individual panel members across differently composed panels. We demonstrate that this problem becomes much less likely when the number of time‐series observations increases.
On the Equivalence of Ad Valorem Tariffs and Specific Tariffs under Duopoly*
Authors: Shea Koon Lam , Shea Esther Y. P.
Published: June 2006

Using a quantity conjectural variation model, this paper examines whether an ad valorem tariff and a specific tariff are equivalent under duopoly. We show that if the average per‐unit import tax is the same for the two tariffs, domestic output will be smaller while foreign output will be larger under an ad valorem tariff. We further show that for any value of a specific tariff, there is a Pareto‐superior ad valorem tariff for all values of conjectural variation except in the case of perfect competition where the two tariffs are equivalent.
The Division and Size of Gains from Liberalization in Service Networks*
Authors: Bhattarai Keshab , Whalley John
Published: June 2006

If two disjoint country service networks involving a small and large country are connected as part of international liberalization in the presence of network externalities, the per capita gain for the small country from access to a large network will be large, and the per capita gain for the large country will be small. In contrast to goods, the benefits of liberalization in network‐related services are more likely to be approximately equally divided between large and small countries than is true of trade in goods, where benefits accrue disproportionately to the small country. We also argue that non‐cooperation in network‐related services trade may involve more extreme retaliation than suggested for trade in goods by the optimal tariff literature, so that relative to a non‐cooperative outcome, gains from liberalization in network‐related services become larger than from liberalization in goods. We develop simple models which we use for numerical examples showing these points, along with an empirical implementation for global telecoms liberalization for the US, Europe, Canada, and the rest of the world using the framework developed in the paper. This shows similar proportional gains to regions, consistent with the theme of the paper that goods and services liberalization differ.
Oligopsony Distortions and Welfare Implications of Trade*
Authors: Devadoss Stephen , Song Wongun
Published: June 2006

While imperfect competition in the output market has garnered extensive focus in the new trade theory literature, input market imperfection has received considerably less attention. Since market power in input purchase has been growing in recent years, it is worth examining the welfare implications of trade arising from oligopsony power. We develop a model consisting of two final goods, one intermediate good, and two primary factors (capital and labor). One final good and the intermediate good employ primary factors, whereas the other final good uses labor and the intermediate input. All markets operate under perfect competition except for the intermediate input, which is oligopsonistic. Using this model, we show that oligopsony can lead to some anomalies such as an increase in the oligopsony output, reward to the intensive‐factor in the oligopsony sector, national welfare, and deterioration of terms of trade, but it always decreases the reward to the intermediate input.
The Torrens–Ricardo Principle of Comparative Advantage: an Extension*
Authors: Kemp Murray C. , Okawa Masayuki
Published: June 2006

The Torrens–Ricardo Principle of Comparative Advantage rests on the special assumptions that, both in autarky and under free trade, all countries can produce all commodities and that, in autarkic equilibrium, each country consumes all producible commodities, at least incipiently. We reformulate the Principle to accommodate alternative assumptions. In our reformulation the emphasis is on marginal rates of substitution, not on the traditional marginal rates of transformation in production. It is shown in effect that, in existing formulations, the supply side is assigned a role that it can rarely sustain.
Modeling Cultural Barriers in International Trade
Authors: Kónya István
Published: June 2006

The paper presents a model that analyzes the role of cultural differences in international trade. The decision to study foreign cultures and languages is incorporated into a simple trade model, which captures basic properties of cultural and language barriers. First, cultural costs differ from physical ones in that they can be eliminated by learning. Secondly, learning a language has economies of scale, thus smaller countries tend to invest more into learning. Thirdly, learning decisions within one country impose an externality on trading partners, since learning by one party makes communication easier also for the other one. This implies that learning decisions are in general inefficient, and the paper derives the connection between the equilibrium and optimal outcomes. Finally, because of the substitutability of learning among countries, a policy where a country subsidizes learning in the other nation—“cultural protectionism”—can be rationalized. Under certain conditions, such a policy can improve the welfare of both countries, in contrast to the case of regular export subsidies.
Is the Border Really That Wide?
Authors: Ceglowski Janet
Published: June 2006

This paper analyzes cross‐border price behavior in a three‐dimensional sample of US and Canadian retail prices. Unit‐root tests reveal that a majority of the cross‐border relative price series are stationary and that short‐run cross‐border price differences are eliminated at average speeds comparable to those for intranational prices. Cross‐border convergence is not absolute; the long‐run international price differences average two to three times their intranational counterparts. Moreover, gravity‐type equations reveal a border effect that is sizable but considerably smaller than earlier estimates. These results suggest that, while significant, the Canada–US border may not be the formidable barrier portrayed in previous studies.
Multinational Corporations, Stackelberg Leadership, and Tariff‐jumping
Authors: Dixon Stuart
Published: June 2006

In this paper we consider the traditional entry mode choice of an incumbent monopolist facing entry by a single foreign firm. By allowing entry to be either via exporting or foreign direct investment and for the possibility of Stackelberg equilibria where firms can set quantities in one of two time periods, namely “early” or “late,” we find conditions where both Cournot and Stackelberg equilibria emerge endogenously. Furthermore, by introducing a simple linear tariff, we see that it not only affects the choice of exporting and FDI in a nonlinear way, but that it can also affect the type of equilibrium that emerges.
“GATT‐think” with Asymmetric Countries*
Authors: Epifani Paolo , Vitaloni Juliette
Published: June 2006

We argue that a trade agreement which conforms to GATT’s reciprocity rule benefits the (stronger) less trade‐dependent country at the expense of the (weaker) more trade‐dependent country. Reciprocity is so unfavorable to the weaker country that it may be worse off under reciprocity than under the Nash‐ bargaining solution, a “power‐based” approach to trade negotiations that reflects power asymmetries among trading partners. Our results question Bagwell and Staiger’s (1999, 2000) view of reciprocity as a rule that “serves to mitigate the influence of power asymmetries on negotiated outcomes.”
The Determinants of Employee Crime in the UK
Authors: RICKMAN NEIL , WITT ROBERT
Published: June 2006

We present evidence on employee theft in the UK using data on actual recorded crime, in a model where employees are ‘rational cheaters’ whose theft decisions may also be influenced by individual characteristics. We produce hypotheses about the role of labour market deterrence and individual influences on employee theft. We then examine the role of these influences using regional crime data supplemented by data from the UK Labour Force Survey and the Home Office. Our results provide information on employee theft as a particular type of crime, on policy that may help to combat it, and on alternative views of the motivation for crime.
The neuronal excitatory amino acid transporter EAAC1/EAAT3: does it represent a major actor at the brain excitatory synapse?
Authors: Nieoullon André , Canolle Benoit , Masmejean Frédérique , Guillet Benjamin , Pisano Pascale , Lortet Sylviane
Published: June 2006

EAAC1/EAAT3 is a transporter of glutamate (Glu) present at the post‐synaptic neuronal element, in opposition to the two other main transporters, GLAST/EAAT1 and GLT1/EAAT2, expressed at the excitatory amino acid (EAA) synapse by surrounding astrocytes. Although, in the adult, EAAC1/EAAT3 exhibits a rather low expression level and is considered to make a minor contribution to Glu removal from the synapse, its early expression during brain development, before the astrocytes are functional, suggests that such a neuronal transporter is involved in the developmental effects of EAA and, possibly, in the biosynthesis and trophic role of GABA, which is excitatory in nature in different brain regions during the earlier stages of brain development. This neuronal Glu transporter is considered to have a dual action as it is apparently involved in the neuronal uptake of cysteine, which acts as a key substrate for the synthesis of glutathione, a major anti‐oxidant, because the neurones do not express the Xc– transport system in the mature brain. Interestingly, EAAC1/EAAT3 activity/expression was shown to be highly regulated by neuronal activity as well as by intracellular signalling pathways involving primarily α protein kinase C (αPKC) and phosphatidylinositol‐3‐kinase (PI3K). Such regulatory processes could act either at the post‐traductional level or at the transcriptional level. It is worth noting that EAAC1/EAAT3 exhibits specificity, compared with other EAA transporters, because it is present mainly in the intracellular compartment and only for about 20% at the plasma membrane. Variations in neuronal Glu uptake were shown to be associated with rapid changes in the trafficking of the transporter protein altering the membranar location of the transporter. More recent data show that astrocyte‐secreted factors such as cholesterol could also influence rapid changes in the location of EAAC1/EAAT3 between the plasma membrane and the cytoplasmic compartment. Such a highly regulated process of EAAC1/EAAT3 activity/expression may have implications in the physiopathology of major diseases affecting EAA brain signalling, which is further supported by data obtained in animal models of hypoxia–anoxia, for example.