bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceived barriers to walking in the neighbourhood environment and change in physical activity levels over 12 months
Authors: Dawson Jill , Hillsdon Melvyn , Boller Irene , Foster Charlie
Published: May 2007

Objectives:

To investigate whether, and to what extent, perceived barriers to neighbourhood walking (BTNW) may be associated with physical activity levels.

Design:

Prospective survey with 12-month follow-up.

Subjects and methods:

750 people attending walking schemes throughout England and Scotland; 551 completed the follow-up. independent variables were demographic characteristics, examples of possible “external” barriers to walking—for example, “worries about personal safety”, and one item concerning ill health. The main outcome measures were “metabolic equivalent” (MET) hours’ walking and overall physical activity in the preceding week.

Results:

Baseline and follow-up demographic characteristics were similar and physical activity levels generally high. Leisure walking changed little over 12 months, while total physical activity levels reduced significantly from a mean (SD) of 71.26 (78.14) MET hours per week at baseline to 59.57 (181.40) at the 12-month follow-up (p<0.001). External BTNW cited between baseline and 12 months increased significantly from a mean (SD) of 1.24 (1.61) at baseline to 1.43 (1.72) at the 12-month follow-up (p<0.001); only “worries about personal safety” reduced. A significant association was found between citing a health-related BTNW and the total number of external BTNW that were reported at baseline. The strength of this association increased over 12 months. Neither changes in reporting external BTNW that occurred over 12 months (increased vs decreased, vs unchanged) nor changes in the presence of a health-related BTNW were significantly related to levels of leisure walking and overall physical activity (MET hours in the preceding week) over the same period.

Conclusion:

Among older people who attended walking schemes, having a health problem that restricted walking had a detrimental influence on people’s perceptions about external BTNW, which increased over time. Actual levels of walking and overall physical activity levels did not appear to be significantly affected by this.
Relating otolith chemistry to surface water chemistry in a coastal plain estuary
Authors: Dorval Emmanis , Jones Cynthia M , Hannigan Robyn , Montfrans Jacques van
Published: May 2007

Although laboratory studies confirm that otoliths incorporate trace elements and stable isotopes from surrounding waters, few studies explore the relationship of otolith chemistry to water chemistry in the field and none include a larger suite of environmental tracers, such as rare earth elements. Using spotted seatrout (Cynoscion nebulosus) as model species, we tested the hypothesis that otoliths record the water chemistry of seagrass habitats in Chesapeake Bay. In summer 2001, we sampled water and juvenile fish in seagrass beds of the bay. Weighted linear regressions showed that [Ba/Ca]otolith and [La/Ca]otolith were best predicted by salinity and were modeled as [Ba/Ca]otolith (µmol·mol–1) = –2.25 ± 0.35 × salinity + 59.47 ± 7.01) and [La/Ca]otolith (pmol·mol–1) = –8.71 ± 0.65 × salinity + 243.87 ± 12.52. [Ba/Ca]otolith increased with [Ba/Ca]water, but the relationship was nonlinear. Salinity did not influence [Mn/Ca]otolith, but this ratio was positively correlated with [Mn/Ca]water. Although the partition coefficient of Sr (DSr = 0.23 ± 0.019) was similar to that in laboratory experiments, [Sr/Ca] in waters and otoliths was decoupled despite equal temperature exposure, suggesting that [Sr/Ca]otolith concentration may not be a simple function of water composition. However, there was a predictive relationship between [δ18O]otolith and [Sr/Ca]water ([δ18O]otolith = 1.18 ± 0.09 × [Sr/Ca]water (mmol·mol–1) – 14.286 ± 0.78) resulting from mixing between fluvial and oceanic waters. Water chemistry showed mixed values as a proxy for otolith chemistry and may not be a surrogate for otolith chemistry in wide estuaries.
Interactions between food quantity and quality (long-chain polyunsaturated fatty acid concentrations) effects on growth and development ofChironomus riparius
Authors: Goedkoop Willem , Demandt Marnie , Ahlgren Gunnel
Published: May 2007

We quantified somatic growth, development, and emergence of the midge Chironomus riparius on experimental diets (oats, Spirulina, and Tetraphyll®) covering gradients in food quality (differing polyunsaturated fatty acids) and quantity (0.1–5.4 mg C·day–1). Additionally, similar incubations without food additions were made using a food-poor sediment containing peat and the green alga Scenedesmus obliquus. Larval and adult size was affected by both food quantity and quality and increased some three to four times across the food concentration gradients. Adult emergence, however, was affected only by food quantity. A type 3 response model showed that a saturation level was reached for the oats treatment at 2.7 mg C·day–1(or 3.9 µg ω3 and 120 µg ω6 polyunsaturated fatty acids·day–1), indicating that the quality of oats constrained further stimulation of larval growth. In the peat treatment, larval growth was very low, no adults emerged, and no larvae even made it to the pupa stage. Fatty acid analyses showed that larvae were capable of synthesizing arachidonic acid via γ-linolenic acid by Δ6- and Δ5-desaturase activity using linoleic acid available in food sources. This strongly suggests that C. riparius is not dependent on dietary sources of eicosapentaenoic acid and arachidonic acid and can sustain viable populations even under a low-quality food regimen.
Bioaccumulation of mercury in pelagic fishes from the northern Gulf of Mexico
Authors: Cai Yan , Rooker Jay R , Gill Gary A , Turner Jason P
Published: May 2007

Total mercury (Hg) concentration was determined in the tissues of 10 pelagic fishes in the northern Gulf of Mexico, and dietary tracers (stable isotopes and fatty acids) were used to evaluate the relationship between Hg and feeding history. Highest Hg levels were observed in blue marlin (Makaira nigricans), carcharhinid sharks (Carcha rhinus spp.), and little tunny (Euthynnus alletteratus), ranging from 1.08 to 10.52 ppm. Moderate to low concentrations (<1.0 ppm) were observed in blackfin tuna (Thunnus atlanticus), cobia (Rachycentron canadum), dolphinfish (Cory phaena hippurus), greater amberjack (Seriola dumerili), king mackerel (Scomberomorus cavalla), wahoo (Acantho cybium solandri), and yellowfin tuna (Thunnus albacares). For the majority of species examined, Hg concentrations did not vary significantly between location (Texas vs. Louisiana) or collection period (2002 and 2003). Significant positive relationships between Hg concentration and body size and (or) weight were detected for 6 of the 10 taxa examined. Hg concentration was also positively associated with trophic position. Three natural associations were identified using stable isotope and fatty acid signatures. Still, no connection between these natural trophic associations and Hg concentration was observed, suggesting that Hg concentration in pelagic fishes was more closely linked to trophic position and size than feeding history.
Genetic divergence and connectivity among river and reef spawning groups of walleye (Sander vitreus vitreus) in Lake Erie
Authors: Strange Rex Meade , Stepien Carol A
Published: May 2007

Discerning population genetic structure is challenging for highly vagile open water animals, as contemporary gene flow may obscure historic phylogeographic patterns. We examined genetic variation among all 10 major river and reef spawning groups of walleye (Sander vitreus vitreus) in Lake Erie for evidence of isolation by distance, segregation by physiographic partitions, and natal site fidelity using 10 nuclear DNA microsatellite loci. Results revealed that although most spawning groups were distinguishable, relationships did not correspond with physiographic basins or distances among localities. Bayesian analyses showed connectivity among some southern shore spawning groups, which included the largest-sized groups. Significant genetic divergence was discerned among walleye spawning in the river systems of eastern Lake Erie, as well as in two sites in western Lake Erie, along with marked isolation from Lake St. Clair. Population structure of Lake Erie walleye thus appears to reflect the interaction of two different intrinsic factors: isolation due to natal site fidelity that maintains patterns of divergence, and connectivity due to individuals that stray from their natal sites to spawn.
Thermal effects on behavior of juvenile walleye pollock (Theragra chalcogramma): implications for energetics and food web models
Authors: Hurst Thomas P
Published: May 2007

The behavioral responses of fishes to temperature variation have received little attention despite their direct implications to bioenergetics-based models of production and encounter-based models of food web dynamics. Behavioral characteristics of juvenile walleye pollock (Theragra chalcogramma), a pelagic marine zooplanktivore, were examined between 2 and 9 °C in large arenas. Routine swim speed, path sinuosity, and schooling cohesiveness of fish in small groups were described from overhead video observations. In a separate experiment, maximum swimming speeds were measured in a recirculating flume. Routine and maximum swimming speeds had contrasting responses to temperature demonstrating a behavioral rather than physiological regulation of activity level. Routine swim speed was 48% faster at 2 °C than at 9 °C. This result is inconsistent with the assumption of a constant activity multiplier for metabolism incorporated into most bioenergetics models of fish growth. Increased swim speed, along with the reduced path sinuosity observed at low temperatures, may reflect kinetic aspects of habitat selection. Group cohesion increased at low temperatures, with nearest neighbors averaging 32% closer at 2 °C than at 9 °C. These results demonstrate that representative models of energy flow through marine food webs depend on an improved understanding of the behavioral as well as physiological responses of fishes to thermal variation.
Regional ecosystem variability drives the relative importance of bottom-up and top-down factors for zooplankton size spectra
Authors: Finlay Kerri , Beisner Beatrix E , Patoine Alain , Pinel-Alloul Bernadette
Published: May 2007

The relative effects of top-down and bottom-up drivers of zooplankton size structure were examined in three limnologically diverse regions of Quebec, Canada. Lake productivity drove biomass of small-sized zooplankton (300–1000 µm) in the Eastern Townships and Laurentian regions, which have high total phosphorus gradients, but was not significant in the low-productivity region, Gouin. Fish species composition was found to affect biomass of large-sized (>1000 µm) zooplankton and was the primary factor affecting zooplankton size structure in the low productivity region. When size structure of the zooplankton communities were described as normalized biomass size spectra, only bottom-up factors were significant, as increasing productivity resulted in higher curve peaks and increased parabola curvature. No factors were significantly related to any parameter of the Pareto distribution to describe size spectra. Overall, bottom-up forces were stronger drivers of zooplankton size structure, particularly in regions with wide ranges in lake trophy, while fish predation was more important in regions with low productivity variability.
Estimating larval fish growth under size-dependent mortality: a numerical analysis of bias
Authors: Tian Tian , Fiksen Øyvind , Folkvord Arild
Published: May 2007

The early larval phase is characterized by high growth and mortality rates. Estimates of growth from both population (cross-sectional) and individual (longitudinal) data may be biased when mortality is size-dependent. Here, we use a simple individual-based model to assess the range of bias in estimates of growth under various size-dependent patterns of growth and mortality rates. A series of simulations indicate that size distribution of individuals in the population may contribute significantly to bias in growth estimates, but that typical size-dependent growth patterns have minor effects. Growth rate estimates from longitudinal data (otolith readings) are closer to true values than estimates from cross-sectional data (population growth rates). The latter may produce bias in growth estimation of about 0.03 day–1 (in instantaneous, specific growth rate) or >40% difference in some situations. Four potential patterns of size-dependent mortality are tested and analyzed for their impact on growth estimates. The bias is shown to yield large differences in estimated cohort survival rates. High autocorrelation and variance in growth rates tend to increase growth estimates and bias, as well as recruitment success. We also found that autocorrelated growth patterns, reflecting environmental variance structure, had strong impact on recruitment success of a cohort.
Relationship of upstream migrating adult Atlantic salmon (Salmo salar) and stream discharge within Catamaran Brook, New Brunswick
Authors: Mitchell Sean C , Cunjak Richard A
Published: May 2007

Stream discharge has long been associated with abundance of returning adult spawning salmonids to streams and may also affect body size distribution of adult salmon as low flows interfere with returns of larger-bodied fish. We examined these relationships of abundance and body size within Catamaran Brook, a third-order tributary to the Miramichi River system of New Brunswick, Canada, to investigate the causes of a declining trend in annual returns of Atlantic salmon (Salmo salar) to this stream. Regression models of adult abundance, proportion of the run as grilse, and body size of returning adults as functions of maximum daily stream discharge during the period of upstream spawner migration were constructed. Adult abundance shows a logarithmic relationship with stream discharge and provides good predictive ability, while appearing to not be significantly related to adult abundance in the larger Miramichi system. The proportion as grilse in the run and female body size are also logarithmically related to stream discharge, with low flow years being very influential in the regressions. These relationships of Atlantic salmon population abundance and body size characteristics have implications with respect to stock integrity and production of the following generation.
OSIRIS observations of OH A2Σ+-X2Π 308 nm solar resonance fluorescence at sunrise in the upper mesosphere
Authors: Gattinger R L , Boone C D , Walker K A , Degenstein D A , Lloyd N D , Bernath P F , Llewellyn E J
Published: May 2007

Since the OH molecule plays a critical role as a catalyst in atmospheric photochemistry, an accurate measurement of the OH density profile covering a broad range of latitudes and solar local times is required to quantify the major reactions involved. The optical spectrograph and infra-red imager system (OSIRIS) instrument on the Odin satellite observes scattered solar radiation at the terrestrial limb from the upper troposphere, the stratosphere, and the mesosphere. The wavelength range, 275 nm to 810 nm includes the OH A2Σ+–X2Π 0–0 band at 308 nm, which is seen in solar resonance emission superimposed upon the underlying atmospheric Rayleigh-scattering background. OSIRIS routinely detects the OH 308 nm emission in the mesosphere from sunrise through to sunset. One feature of the OH diurnal variation is a nocturnal layer in the 80–85 km region that is frequently, but not always, detectable in solar resonance for a short period following sunrise — the feature we label here as the "sunrise flash". This paper describes the observational analysis procedures involved in the quantitative measurement of the OSIRIS OH profiles together with a broad overview of the variability of the feature at sunrise. Also included is a photochemical model simulation of the OH sunrise layer using background atmospheric parameters, especially the water vapour mixing ratio, provided by the ACE/FTS instrument on the Canadian SCISAT satellite. For a number of nearly coincident measurements between OSIRIS OH and ACE/FTS water vapour, the model simulations show general agreement between the two. Agreement is improved by modifying the eddy mixing rates in the 80–85 km region, commensurate with the expected range of mixing rates.PACS Nos.: 42.68.Ay, 82.20.Pm, 82.30.Cf, 82.33.Tb, 92.60.H–, 92.60.Ta
OH spectroscopy and chemistry investigated with astronomical sky spectra
Authors: Cosby P C , Slanger T G
Published: May 2007

This study summarizes the use of a large catalog of astronomical sky spectra to study different aspects of OH spectroscopy and chemistry in the terrestrial night sky. The sky spectra are unique in that they have high spectral resolution, cover the entire visible wavelength region in one exposure, and are intensity-calibrated with respect to standard stars. The intensity calibration, in particular, allows a significant revision to the OH Meinel band intensity distribution that has been in use for 43~years and permits critical evaluation of the many available sets of OH emission coefficients. The spectra further allow the OH rovibrational population distributions to be monitored throughout many nights. The OH vibrational population distribution is found to change during the night, with the population ratio between the extreme high-v and low-v levels that we can detect, v = 9 and v = 3, varying by as much as a factor of two; the low-v levels being predominant earlier in the night. It has been common to determine the kinetic temperature of the OH emission region by assuming that it is equal to the low-J rotational temperature associated with particular OH bands, typically bands originating in the v = 6 and v = 8 levels. The present calibrated data set reveals that the rotational temperatures are significantly greater for high-v than for low-v levels, the typical difference between v = 3 and v = 8 being 15 K. Previous attempts to establish that a difference existed are consistent with our current observations, although conclusions from those earlier results were limited by relatively wide error limits. The present rovibrational population measurements, which extend to high rotational levels (J′ ≤ 25.5), also reveal that the high-J populations are largely independent of vibrational level — the high-J population in v = 3 is similar to that in v = 7.PACS Nos.: 92.60.H, 92.60.hw, 33.20.–t, 33.20.Kf, 33.70.–w
Using colour in auroral imaging
Authors: Partamies N , Syrjäsuo M , Donovan E
Published: May 2007

The prototype of an auroral colour camera named Rainbow was run at the Auroral Station in Adventdalen, Svalbard, Norway, during a Finnish optical campaign in February, 2004. Instead of narrow band-pass filters and grey-scale images, this imager records colour images of the aurora using four wide-band channels (a colour CCD) with the field-of-view of about 150°. In this study, we show the results of fitting the four Rainbow channels (cyan-magenta, cyan-green, yellow-magenta, yellow-green) to reconstruct the traditionally filtered auroral wavelengths: green (557.7 nm), red (630.0 nm), and blue (427.8 nm), which were simultaneously recorded by the meridian scanning photometer (MSP) at the same station. This fit is qualitatively extremely good and almost linear throughout the data. In studying the auroral evolution during substorms, there is no significant difference whether MSP or Rainbow data are used. However, due to wide-band colour channels, the background illumination has a strong effect on the Rainbow data. During low signal levels (only background or faint aurora) the reconstruction errors are larger. The data for this study were captured on 21 February 2004. The time period of interest includes a substorm sequence, which is examined using colour auroral images and data from the MSP. PACS No.: 94.20.Ac
Calibration of the Purple Crow Lidar vibrational Raman water-vapour mixing ratio and temperature measurements
Authors: Argall P S , Sica R J , Bryant C R , Algara-Siller M , Schijns H
Published: May 2007

Purple Crow Lidar (PCL) measurements of the vibrational Raman-shifted backscatter from water vapour and nitrogen molecules allows height profiles of the water-vapour mixing ratio to be measured from 500 m up into the lower stratosphere. In addition, the Raman nitrogen measurements allow the determination of temperature profiles from about 10 to 40 km altitude. However, external calibration of these measurements is necessary to compensate for instrumental effects, uncertainties in our knowledge of the relevant molecular cross sections, and atmospheric transmission. A comparison of the PCL-derived water-vapour concentration and temperature profiles with routine radiosonde measurements from Detroit and Buffalo on 37 and 141 nights, respectively, was undertaken to provide this calibration. The calibration is then applied to the measurements and monthly mean-temperature and water-vapour profiles are determined.PACS Nos.: 42.68.Wt, 42.79.Qx
An update on the hydroxyl airglow temperature record from the Auroral Station in Adventdalen, Svalbard (1980–2005)
Authors: Dyrland M E , Sigernes F
Published: May 2007

This paper reports on the daily mesospheric winter temperature series derived from ground-based spectral measurements of the hydroxyl airglow layer from the Auroral Station in Adventdalen near Longyearbyen, Svalbard (78°N, 15°E). Temperature estimates from the four latest seasons (2001–2002 to 2004–2005) have been added to the series reported by Sigernes et al. J. Geophys. Res. 108(A9), 1342 (2003). Lomb–Scargle periodogram analyses were performed on both hourly and daily average temperatures to look for significant periods. From the daily means, ∼24 and ∼26 d oscillations that are consistent with a solar rotation modulation of the atmosphere were identified. Analyses of the hourly averaged data did not reveal any considerable diurnal and semidiurnal periods in the temperatures. The 2003–2004 mesopause winter was one of the warmest reported over Svalbard during the last 25 years. It is common to observe within a few days temperature fluctuations in the range 20–40 K. Some years show far less variation than others. The overall daily average winter temperature is 209 K. The annual mean winter temperatures show a slightly positive temperature trend (+0.2 ± 0.1 K/year), on the verge of being a statistically significant change in the winter mesospheric temperatures over Svalbard.PACS Nos.: 92.60.hc, 07.20.Dt, 93.30.Sq, 92.60.hw
Experimental air-broadened line parameters in the\bm{ u}\textsubscript band of CH\textsubscriptD
Authors: Predoi-Cross A , Brawley-Tremblay S , Povey C , Smith M A
Published: May 2007

In this study, we report the first experimental measurements of air-broadening and air-induced pressure-shift coefficients for approximately 378 transitions in the ν2 fundamental band of CH3D. These results were obtained from analysis of 17 room-temperature laboratory absorption spectra recorded at 0.0056 cm–1 resolution using the McMath–Pierce Fourier transform spectrometer located on Kitt Peak, Ariz. Three absorption cells with path lengths of 10.2, 25, and 150 cm were used to record the spectra. The total sample pressures ranged from 0.129 × 10–2 to 52.855 × 10–2 atm with CH3D volume mixing ratios of approximately 0.0109 in air. The spectra were analyzed using a multispectrum nonlinear least-squares fitting technique. We report measurements for air pressure-broadening coefficients for transitions with quantum numbers as high as J′′ = 20 and K = 15, where K′′ = K′ ≡ K (for a parallel band). The measured air-broadening coefficients range from 0.0205 to 0.0835 cm–1atm–1 at 296 K. All the measured pressure-shift coefficients are negative and are found to vary from about –0.0005 to –0.0080 cm–1 atm–1 at the temperature of the spectra. We have examined the dependence of the measured broadening and shift parameters on the J′′, and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m = –J′′, J′′, and J′′ + 1 in the QP-, QQ-, and QR-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 4.4%.PACS Nos.: 33.20.Ea, 39.30+w
Diversity and relationships of bradyrhizobia from legumes native to eastern North America
Authors: Parker Matthew A , Kennedy David A
Published: May 2007

DNA sequencing and polymerase chain reaction (PCR) assays with lineage-specific primers were used to analyze the diversity of 276 isolates of Bradyrhizobium sp. nodule bacteria associated with 13 native legumes species in the northeastern United States, representing eight genera in six legume tribes. A PCR screen with two primer pairs in the rRNA region indicated that seven of the legume species were exclusively associated with strains having markers resembling Bradyrhizobium elkanii, while the remaining six host species harbored strains related to both B. elkanii and Bradyrhizobium japonicum. Sequence analysis of 22 isolates for portions of 16S rRNA and 23S rRNA yielded congruent phylogenetic trees and showed that isolates from different legume genera often shared similar or identical sequences. However, trees inferred from portions of two other genes (α-ketoglutarate dioxygenase gene (tfdA), the α-subunit of nitrogenase (nifD)) differed significantly from the rRNA phylogeny. Thus, for Bradyrhizobium populations in this region, lateral gene transfer events appear to have altered genealogical relationships of different portions of the genome. These results extend the number of likely cases of gene transfer between divergent taxa of Bradyrhizobium (from members of the B. elkanii lineage to the B. japonicum group) and suggest that transfers have also occurred among separate subgroups of the B. elkanii lineage.Key words: Bradyrhizobiaceae, lateral gene transfer, phylogenetic congruence, ribosomal RNA.
Identification of siderophores ofPseudomonas stutzeri
Authors: Zawadzka Anna M , Vandecasteele Frederik P.J , Crawford Ronald L , Paszczynski Andrzej J
Published: May 2007

We have identified two types of siderophores produced by Pseudomonas, one of which has never before been found in the genus. Twelve strains of Pseudomonas stutzeri belonging to genomovars 1, 2, 3, 4, 5, and 9 produced proferrioxamines, the hydroxamate-type siderophores. Pseudomonas stutzeri JM 300 (genomovar 7) and DSM 50238 (genomovar 8) and Pseudomonas balearica DSM 6082 produced amonabactins, catecholate-type siderophores. The major proferrioxamines detected were the cyclic proferrioxamines E and D2. Pseudomonas stutzeri KC also produced cyclic (X1and X2) and linear (G1and G2a-c) proferrioxamines. Our data indicate that the catecholate-type siderophores belong to amonabactins P 750, P 693, T 789, and T 732. A mutant of P. stutzeri KC (strain CTN1) that no longer produced the secondary siderophore pyridine-2,6-dithiocarboxylic acid continued to produce all other siderophores in its normal spectrum. Siderophore profiles suggest that strain KC (genomovar 9) belongs to the proferrioxamine-producing P. stuzeri. Moreover, a putative ferrioxamine outer membrane receptor gene foxA was identified in strain KC, and colony hybridization showed the presence of homologous receptor genes in all P. stutzeri and P. balearica strains tested.Key words: siderophore, Pseudomonas stutzeri, ferrioxamine, amonabactin.
Escherichia coli inactivation mechanism by pressurized CO2
Authors: Oulé Mathias K , Tano Kablan , Bernier Anne-Marie , Arul Joseph
Published: May 2007

The effects of pressurized CO2 on the survival of Escherichia coli and the mechanism of cell inactivation were studied. Bacterial cultures were inoculated in nutrient broth and incubated at 30 °C for 18 h. Exposure of the cells to CO2 under pressures ranging from 2.5 to 25 MPa and at temperatures between 8 and 40 °C was performed in a double-walled reactor with a 1 L capacity. The effect of the treatment on the cells was evaluated by plating and by transmission and scanning electron microscopy observation. Vapour CO2 generated a bacteriostatic effect. In liquid or supercritical state, CO2 provided a bactericidal effect. The bactericidal effect increased with pressure and temperature. The mechanism of cell inactivation by liquid CO2 involved two stages. First, cell stress caused by the CO2 penetration provoked cell wall collapse and cellular content precipitation. Second, the cell death caused by supercritical extraction of intracellular substances and cell envelope perforation resulted in leaking of intracellular constituents. In supercritical conditions, the cell inactivation process had one single phase: cellular death.Key words: Escherichia coli, CO2 under pressure, inactivation mechanism, bactericidal effect.
A GacS deficiency does not affectPseudomonas chlororaphisPA23 fitness when growing on canola, in aged batch culture or as a biofilm
Authors: Poritsanos N , Selin C , Fernando W G.D , Nakkeeran S , Kievit T.R. de
Published: May 2007

Pseudomonas chlororaphis PA23 is a biocontrol agent that protects against the fungal pathogen Sclerotinia sclerotiorum. Employing transposon mutagenesis, we isolated a gacS mutant that no longer exhibited antifungal activity. Pseudomonas chlororaphis PA23 was previously reported to produce the nonvolatile antibiotics phenazine 1-carboxylic acid and 2-hydroxyphenazine. We report here that PA23 produces additional compounds, including protease, lipase, hydrogen cyanide, and siderophores, that may contribute to its biocontrol ability. In the gacS mutant background, generation of these products was markedly reduced or delayed with the exception of siderophores, which were elevated. Not surprisingly, this mutant was unable to protect canola from disease incited by S. sclerotiorum. The gacS mutant was able to sustain itself in the canola phyllosphere, therefore, the loss of biocontrol activity can be attributed to a reduced production of antifungal compounds and not a declining population size. Competition assays between the mutant and wild type revealed equivalent fitness in aged batch culture; consequently, the gacS mutation did not impart a growth advantage in the stationary phase phenotype. Under minimal nutrient conditions, the gacS-deficient strain produced a tenfold less biofilm than the wild type. However, no difference was observed in the ability of the mutant biofilm to protect cells from lethal antibiotic challenge.Key words: Pseudomonas, biocontrol, gacS, fitness, biofilms.
Cloning and characterization of theddsAgene encoding decaprenyl diphosphate synthase fromRhodobacter capsulatusB10
Authors: Liu Xinyi , Wu Haizhen , Ye Jiang , Yuan Qinsheng , Zhang Huizhan
Published: May 2007

A decaprenyl diphosphate synthase gene (ddsA, GenBank accession No. DQ191802) was cloned from Rhodobacter capsulatus B10 by constructing and screening the genome library. An open reading frame of 1002 bp was revealed from sequence analysis. The deduced polypeptide consisted of 333 amino acids residues with an molecular mass of about 37 kDa. The DdsA protein contained the conserved amino acid sequence (DDXXD) of E-type polyprenyl diphosphate synthase and showed high similarity to others. In contrast, DdsA showed only 39% identity to a solanesyl diphosphate synthase cloned from R. capsulatus SB1003. DdsA was expressed successfully in Escherichia coli. Assaying the enzyme in vivo found it made E.coli synthesize UQ-10 in addition to the endogenous production UQ-8.Key words: ubiquinone, polyprenyl diphosphate synthase, gene expression, Rhodobacter capsulatus.
The expression ofnifBgene fromHerbaspirillum seropedicaeis dependent upon the NifA and RpoN proteins
Authors: Rego Fabiane G.M , Pedrosa Fábio O , Chubatsu Leda S , Yates M Geoffrey , Wassem Roseli , Steffens Maria B.R , Rigo Liu U , Souza Emanuel M
Published: May 2007

The putative nifB promoter region of Herbaspirillum seropedicae contained two sequences homologous to NifA-binding site and a –24/–12 type promoter. A nifB::lacZ fusion was assayed in the backgrounds of both Escherichia coli and H. seropedicae. In E. coli, the expression of nifB::lacZ occurred only in the presence of functional rpoN and Klebsiella pneumoniae nifA genes. In addition, the integration host factor (IHF) stimulated the expression of the nifB::lacZ fusion in this background. In H. seropedicae, nifB expression occurred only in the absence of ammonium and under low levels of oxygen, and it was shown to be strictly dependent on NifA. DNA band shift experiments showed that purified K. pneumoniae RpoN and E. coli IHF proteins were capable of binding to the nifB promoter region, and in vivo dimethylsulfate footprinting showed that NifA binds to both NifA-binding sites. These results strongly suggest that the expression of the nifB promoter of H. seropedicae is dependent on the NifA and RpoN proteins and that the IHF protein stimulates NifA activation of nifB promoter.Key words: Herbaspirillum seropedicae, nif, nitrogen fixation, NifA, RpoN.
Studies on antimicrobial activity of cobalt(III) ethylenediamine complexes
Authors: Nagababu Penumaka , Latha J Naveena Lavanya , Pallavi P , Harish S , Satyanarayana S
Published: May 2007

A series of cobalt(III) mixed ligand complexes of type [Co(en)2L]+3, where L is bipyridine, 1,10-phenanthroline, imidazole, methylimidazole, ethyleimidazole, dimethylimidazole, urea, thiourea, acetamide, thioacetamide, semicarbazide, thiosemicarbazide, or pyrazole, have been isolated and characterized. The structural elucidation of these complexes has been explored by using absorption, infrared, and 1H NMR nuclear magnetic resonance spectral methods. The infrared spectral data of all these complexes exhibit a band at 1450/cm and 1560–1590/cm, which correspond to C = C and C = N, a band at 575/cm for Co-N (en), and a band at 480/cm for Co-L (ligand). All these complexes were found to be potent antimicrobial agents. The antibacterial activity was studied in detail in terms of zone inhibition, minimum bactericidal, and time period of lethal action. Among all, complexes bipyridine, 1,10-phenanthroline, dimethylimidazole, and pyrazole, possess the highest antibacterial activity. Antifungal activity was done by disc-diffusion assay and 50% inhibitory concentrations that possess high antifungal activity.Key words: cobalt(III) complexes, ethylenediamine, antimicrobial, antifungal.
Relationships between microsite type and the growth and nutrition of young black spruce on post-disturbed lowland black spruce sites in eastern Canada
Authors: Lavoie Martin , Paré David , Bergeron Yves
Published: May 2007

The surface of the soil in recently harvested or burned lowland black spruce (Picea mariana (Mill.) BSP) sites is composed of a fine mosaic of different bryophytes (mostly Sphagnum spp. and feathermosses), disturbed organic material originating mostly from mosses at different stages of decay, and exposed mineral soil. Growth substrates were compared in lowland black spruce stands regenerating after either careful logging or wildfire. The 3-year annual increment for black spruce seedlings was greatest with substrates of feathermosses, mainly Pleurozium schreberi (Brid.) Mitt., fibric material of P. schreberi origin, and a mixture of fibric P. schreberi and humic materials; it was least with fibric Sphagnum spp., mineral soil, and decaying wood substrates. The most favourable substrates for growth were characterized by better black spruce N and P foliar status. Our results also suggest that categories of growth substrates in the rooting zone reflect nutritional quality better than categories of growth substrates on the soil surface. To maintain or increase black spruce growth following careful logging of sites prone to paludification, we recommend fill-planting of seedlings in substrates originating from P. schreberi; management techniques that favour P. schreberi over Sphagnum mosses should also be developed.
Flower stimulation in young miniaturized seed orchards of Douglas-fir (Pseudotsuga menziesii)
Authors: Cherry Marilyn L , Anekonda Thimmappa S , Albrecht Michael J , Howe Glenn T
Published: May 2007

We studied flower stimulation in two young miniaturized seed orchards of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) in Oregon. In experiment 1, female and male flowering were substantially enhanced when the trees were treated 2–4 years after grafting with stem girdling plus stem-injected gibberellin A4/7 (GA 0.25× rate = ProCone(tm) at 0.084 µL·mm–2 scion cross-sectional area). Comparable results were obtained the following year when the same trees were retreated with 1× GA. In experiment 2, female and male flowering were significantly enhanced when 3-year-old trees were treated with girdling plus either 1× GA, 1.5× GA, or 2× GA. Some treatments had higher mortality and less height growth than the control in the year of cone development. We recommend using a combination of girdling and 1× GA biennially once trees are large enough to produce large per-hectare seed yields and withstand the stress of flower stimulation. At the study orchards, this seems to be about 5 years postgrafting, just before the sixth growing season. Yields were estimated to be 272 963 seeds·ha–1 at age 4 years, or 143 095 seeds·ha–1 annually with stimulation occurring every 2 years. Yields should increase as orchards age, with full stocking, and with higher planting densities.
Trees dying standing in the northeastern boreal old-growth forests of Quebec: spatial patterns, rates, and temporal variation
Authors: Aakala Tuomas , Kuuluvainen Timo , Grandpré Louis De , Gauthier Sylvie
Published: May 2007

Spatial patterns, rates, and temporal variation of standing-tree mortality were studied in unmanaged boreal old-growth forests of northeastern Quebec. The study was carried out by sampling living and dead trees within 15 transects (400 m long, 40 m wide). The transects lay in stands that were classified according to their species composition in three types: dominated by black spruce, Picea mariana (Mill.) BSP; mixed P. mariana and balsam fir, Abies balsamea (L.) Mill.; and dominated by A. balsamea. Spatial patterns were analysed using Ripley's K function. The year of death was cross-dated using 190 sample discs extracted from dead standing A. balsamea and P. mariana to assess the rates and temporal variation of mortality. The spatial patterns of standing dead trees in P. mariana stands were predominantly clustered. The spatial patterns of large dead trees (>19 cm diameter at breast height (1.3 m height; DBH)) in mixed and A. balsamea-dominated stands were mainly random, with few stands showing clustered patterns. Small dead trees (9–19 cm DBH) in these stands were generally more clustered than larger trees. Tree mortality varied from year to year, though some mortality was observed in all the studied stand types for almost every year. Standing trees that had recently died accounted for 62%, 48%, and 51% of overall mortality in P. mariana-dominated, mixed, and A. balsamea-dominated stands, respectively. The results of this study indicate that mortality of standing trees outside of episodic mortality events (such as insect outbreaks) is an important process in the creation of structural complexity and habitat diversity in these stands.
Genetic analysis of early field growth of loblolly pine clones and seedlings from the same full-sib families
Authors: Baltunis Brian S , Huber Dudley A , White Timothy L , Goldfarb Barry , Stelzer Henry E
Published: May 2007

Field trials established with clones and seedlings from the same families provide an opportunity for comparing full-sib family performance across propagule types. More than 1200 different clones together with over 14 000 zygotic seedlings from the same 61 full-sib families of loblolly pine (Pinus taeda L.) were tested on multiple sites across Florida and Georgia. The genetic variance associated with several early growth traits partitioned differently depending on propagule type. Most of the genetic variance associated with growth in the clonal population was additive, while the estimate of dominance in the seedling population was greater than estimates of dominance in the clonal population, based on single-site analyses. Apparently, a lack of randomization of the seedlings prior to field establishment caused full-sib families to appear more different, inflating estimates of dominance genetic variance. Parental and full-sib family ranks were stable regardless of propagule type as indicated by type B genetic correlations. In the clonal population, little genotype × environment interaction was observed across sites at the parental, family, and clonal levels for all traits. The high genetic correlations between propagule types provide further assurance that selections made through traditional tree-improvement activities for recurrent selection for general combining ability in seedling trials can also be used successfully for breeding families to test in a clonal forestry program.
Nutrient cycling in a poplar plantation (Populus trichocarpa × Populus deltoides'Beaupré') on former agricultural land in northern Belgium
Authors: Meiresonne Linda , Schrijver An De , Vos Bruno De
Published: May 2007

Hydrological fluxes, atmospheric deposition, litterfall, and soil percolation of the most important nutrients were measured in an 18-year-old poplar plantation on a well-drained silt loam soil during 2 consecutive years. Downward soil water flux and transpiration are the most important factors in the water balance. Around 80% of total nitrogen input (6.6 and 6.5 kmol·ha–1in years 1 and 2, respectively) originates from litterfall. After nitrification only a negligible amount of nitrate leaches during the growing season. Yearly uptake of nitrogen by the poplar ecosystem (woody biomass, leaves, and ground vegetation) approximately equals the input, of which more than 50% is accounted for by the leaves. This indicates very efficient nitrogen cycling. Total deposition of base cations originates from two processes, dry deposition (Mg2+and Ca2+) and canopy leaching (K+and Ca2+). Litter input of Ca2+represents about 83% of the total input (stand deposition + litterfall), Mg2+about 61%, and K+less then 50%. Percolation of base cations at 1 m depth is very limited. Rather high Ca2+and K+contents of the woody biomass can lead to high exports at harvest. Nutrient cycling in the poplar stand proved to be very efficient, with no significant nutrient losses.
Modeling sprout-origin oak regeneration in the central Appalachians
Authors: Gould P J , Fei S , Steiner K C
Published: May 2007

We describe the development of individual-tree models to estimate, before overstory removal, the contribution of common central Appalachian oak species (northern red oak (Quercus rubra L.), black oak (Quercus velutina Lam.), chestnut oak (Quercus montana Willd.), and white oak (Quercus alba L.)) to stand stocking in the third decade (20–30 years) after harvest. The models incorporate three aspects of sprout-group development: (1) the initial sprouting of overstory oaks (≥5 cm DBH) following cutting, (2) sprout-group survival, and (3) sprout-group size at the end of the regeneration period. Logistic regression was used to model initial sprouting as a function of parent tree species and diameter using measurements on 1173 stumps. Sprout-group survival was extrapolated from 4 year remeasurements on 321 stumps. Sprout-group size, expressed as a percentage of stocking, was estimated from measurements on 429 third-decade sprout groups. Predicted sprout-origin stocking values calculated for mature oak stands compared favorably with stocking values observed in third-decade stands. The models provide forest managers with essential information on stand development following planned regeneration treatments. A similar modeling approach may be useful in other plant communities where sprouting plays an important role in post-disturbance stand development.
Testing a process-based fine fuel moisture model in two forest types
Authors: Matthews S , McCaw W L , Neal J E , Smith R H
Published: May 2007

We test the ability of a recently developed process-based fine fuel moisture model to predict the surface and profile moisture content of litter fuels in two types of eucalytpus forest in Western Australia. The model predicts fuel moisture by modelling the energy and water budgets of the litter, intercepted precipitation, and the air spaces in the litter. The model equations are solved using an initial observation of fuel moisture and boundary conditions derived from basic weather observations. Model predictions are compared with twice-daily field observations made from October 1983 to March 1984. A novel two-stage method is used to assess model performance; the ability of the model to predict whether fuel is flammable is first assessed using contingency table analysis, and then the accuracy of predictions when the fuel is flammable is assessed. The model is capable of predicting the flammability of litter in both forest types with 80%–90% accuracy. Predictions of moisture content in flammable fuels are, on average, accurate to within 3% once the model has been calibrated against field observations. The model can be adapted to other forest types by specifying suitable parameters or by calibration against field observations.
Projection of a diameter distribution through time
Authors: Qin Jianhua , Cao Quang V , Blouin David C
Published: May 2007

Three approaches to characterizing the diameter distribution of a future stand are presented. The first approach is the "parameter-recovery" method, which links a whole-stand model to a diameter-distribution model. The next two approaches provide linkages between an individual-tree model and a diameter-distribution model. Tree-survival and diameter-growth equations were applied to the tree list (the "tree-projection" method) or to the diameter distribution (the "distribution-projection" method) at the beginning of the growth period. A numerical example of Weibull distributions that characterized diameter data from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) is presented. All three methods produced similar results in terms of Reynolds et al.'s (1988) error indices, whereas the distribution-projection method outperformed the other two methods in predicting total and merchantable volumes per hectare. This study demonstrated that the diameter-distribution model could be linked to either a whole-stand model or an individual-tree model with comparable success.
Apical dominance and apical control in multiple flushing of temperate woody species
Authors: Cline Morris G , Harrington Constance A
Published: May 2007

In young plants of many woody species, the first flush of growth in the spring may be followed by one or more flushes of the terminal shoot if growing conditions are favorable. The occurrence of these additional flushes may significantly affect crown form and structure. Apical dominance (AD) and apical control (AC) are thought to be important control mechanisms in this developmental response. A two-phase AD – AC hypothesis for the factors controlling a subsequent flush is presented and evaluated on the basis of currently known studies. The first, very early phase of this additional flush consists of budbreak and the very beginning of outgrowth of the newly formed current buds on the first flushing shoot. There is evidence that this response often involves the release of AD, which is significantly influenced by the auxin:cytokinin ratio as well as by other signals including nutrients and water. This first phase is immediately followed by a second phase, which consists of subsequent bud outgrowth under the influence of apical control. Although definitive data for hormone involvement in this latter process is sparse, there is some evidence suggesting nutritional mechanisms linked to possible hormone activity. Stem-form defects, a common occurrence in multiple-flushing shoots, are analyzed via the AD – AC hypothesis with suggestions of possible means of abatement.