bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clostridium botulinum type E occurs and grows in the alga Cladophora glomerata
Authors: Byappanahalli Muruleedhara N. , Whitman Richard L. 
Published: July 2009

In recent years, massive avian die-offs from Clostridium botulinum type E infection have occurred in the Sleeping Bear Dunes National Lakeshore (SLBE) area of Lake Michigan. These outbreaks have been coincidental with massive blooms of the green algae Cladophora , mostly Cladophora glomerata . We tested the hypothesis that Clostridium botulinum type E can grow under suitable conditions in these algal mats. In a lab mesocosm study, Cladophora from four outbreak-impacted beaches from SLBE were compared with four unimpacted beaches in the Milwaukee–Racine area for bontE gene of Clostridium botulinum. Frequency of the bontE gene was higher after incubation (25 °C for up to 6 weeks) of Cladophora from impacted vs. the unimpacted area. Since no type E gene was detected initially in Cladophora from any of the eight locations, we infer that the increased occurrence of type E gene arose from spore germination or vegetative Clostridium growth within the existing algal mats of SLBE. Moreover, we found that the congener Clostridium perfringens readily grows in mesocosms containing Cladophora.
Bioenrichment of trace elements in a series of ponds near a northern fulmar (Fulmarus glacialis) colony at Cape Vera, Devon Island
Authors: Brimble Samantha K. , Blais Jules M. , Kimpe Linda E. , Mallory Mark L. , Keatley Bronwyn E. , Douglas Marianne S.V. , Smol John P. 
Published: July 2009

Seabirds are an important link between their marine feeding areas and their terrestrial breeding environments, transporting both marine-derived nutrients and contaminants and then depositing them on land in their guano. In this study, the impact of a large northern fulmar ( Fulmarus glacialis ) colony on the water chemistry of 26 nearby ponds spanning a gradient of seabird influence was investigated at Cape Vera, Devon Island, in the Canadian High Arctic. The presence of the fulmar colony has led to nutrient and trace element enrichment in the ponds, as evidenced by the close association among As, Cd, Co, Cu, Li, Mn, Mo, Ni, Sb, and Sr and the ornithogenic gradient. The ponds most affected by the fulmar colony were characterized by increased primary production, high organic carbon concentrations, and elevated pH — conditions favorable for the in situ removal of metals from the water column. Despite this, the highest trace element concentrations were observed in the seabird-influenced ponds, suggesting that these elements have undergone biotransport.
Influence of diel cycles of respiration, chlorophyll, and photosynthetic parameters on the summer metabolic balance of temperate lakes and rivers
Authors: Forget Marie-Hélène , Carignan Richard , Hudon Christiane 
Published: July 2009

Primary production, planktonic respiration, bacterial abundance, and chlorophyll a were measured in the epilimnion of two Canadian Shield lakes and in two large rivers to establish their metabolic balance and to contrast oligotrophic and oligo-mesotrophic systems. Pronounced diel respiration cycles were observed in all systems, with a minimum in the morning and a maximum in the evening. Respiration was positively correlated with water temperature, incident light, and chlorophyll a concentration. Diel cycles of chlorophyll a were discernible in both rivers and in the oligo-mesotrophic lake. Our results show that a single morning sampling underestimates both respiration and chlorophyll a, whereas a single sample taken at noon generally agrees better with the average of four daily measurements. In oligotrophic Lac Croche, the photosynthetic parameter αBremained constant throughout the day, whereas PBmincreased by 12.5% between 0600 h and 1300 h. Ignoring the diel community respiration cycle resulted in a ~25% underestimation of daily respiration, whereas ignoring the PBmcycle induced a ~9% underestimation of the daily primary production. The net balance between production (P) and respiration (R) of the oligotrophic lake epilimnion remained positive during two summers, and the P:R ratio showed net autotrophy for all systems except for the oligotrophic river, which was slightly net heterotrophic.
Lead–radium dating of orange roughy (Hoplostethus atlanticus): validation of a centenarian life span
Authors: Andrews Allen H. , Tracey Dianne M. , Dunn Matthew R. 
Published: July 2009

Life-span estimates for orange roughy ( Hoplostethus atlanticus ) range from ~20 years to well over 100 years. In this study, an improved lead–radium dating technique provided independent age estimates from sagittal otoliths. This technique used the known properties of radioactivity for lead-210 and radium-226 to determine the validity of fish age estimates. An improvement to lead–radium dating using mass spectrometry allowed the use of smaller samples than previously possible; therefore, an application was made to otolith cores, the first few years of otolith growth. This approach circumvented the use of whole otoliths and alleviated many of the assumptions that were necessary in previous lead–radium dating applications. Hence, it was possible to critically evaluate lead–radium dating as a tool in fish age validation. The measurement of lead–radium ratios for a series of age groups that consisted of otolith cores, grouped based on growth-zone counts from thin sections, showed a high degree of correlation to the expected lead–radium ingrowth curve. This finding provided support for age estimation procedures using thin otolith sectioning. As independent estimates of age, the results indicated that fish in the oldest age group were at least 93 years old, providing robust support for a centenarian life span.
Reduced swimming performance and increased growth in domesticated rainbow trout, Oncorhynchus mykiss
Authors: Reinbold Drew , Thorgaard Gary H. , Carter Patrick A. 
Published: July 2009

Domesticated populations of rainbow trout ( Oncorhynchus mykiss ) probably have been selected for high growth rates and large body size, which may have resulted in reduced sprint swimming performance. We hypothesized that more domesticated populations of rainbow trout would have higher growth rates and larger body size, but slower swim speed, relative to semiwild populations. We tested this hypothesis by measuring body mass, body length, and sprint swim speed multiple times over 92 days in progeny from crosses between males from three clonal lines and an outbred female. We found significantly higher body masses and significantly slower swim speeds in the highly domesticated Arlee and Hot Creek progeny groups compared with the semiwild Swanson hybrid progeny group, supporting our hypothesis. Growth rates also differed significantly among groups, but at the ages measured, the Swanson hybrid progeny had an intermediate growth rate. However, given the differences in body mass, either growth rates were higher in the more domesticated progeny groups at young unmeasured ages and (or) they hatched at a significantly larger body mass than the semiwild Swanson hybrid.
Experimental measurement of hydrosystem-induced delayed mortality in juvenile Snake River spring Chinook salmon (Oncorhynchus tshawytscha) using a large-scale acoustic array
Authors: Rechisky Erin L. , Welch David W. , Porter Aswea D. , Jacobs Melinda C. , Ladouceur Adrian 
Published: July 2009

Out-migrating Snake River salmon smolts must pass eight major hydro dams before reaching the Pacific Ocean. Direct mortality at the dams is generally low; however, the cumulative stress caused by dam passage is hypothesized to result in delayed mortality, which occurs beyond the impounded section of the river. We tested the delayed mortality hypothesis by comparing in-river and early ocean survival of hatchery-origin spring Chinook salmon ( Oncorhynchus tshawytscha ) from the Snake River to a mid-Columbia River population that passes through only four dams and has higher smolt to adult return rates. Smolts >140 mm fork length were implanted with acoustic transmitters and tracked with the Pacific Ocean Shelf Tracking (POST) array to as far as Alaska. There was no detectable difference in survivorship to the first ocean detection line, 274 km beyond the final dam (SSnake = 29% ± 4%, SYakima = 28% ± 5%), indicating that the survival disparity observed in adult return rates may develop later in the marine life history phase. Our study is the first to estimate survival in the coastal ocean and demonstrates the utility of a large-scale array in testing previously intractable hypotheses.
Regional-scale groundwater flow in a Canadian Shield setting
Authors: Sykes Jonathan F. , Normani Stefano D. , Jensen Mark R. , Sudicky Edward A. 
Published: July 2009

A three-dimensional numerical analysis of a 5734 km2 watershed situated in the Canadian Shield has been conducted to illustrate aspects of regional-scale groundwater flow in a crystalline rock setting. An essential requirement of the analysis is the preservation and accurate description of the complex topography, surface water drainage network, groundwater salinity distribution, and permeability distributions. The postglacial evolution of the groundwater flow system was investigated using the finite difference model SWIFT-III. Robustness was assessed by exploring the sensitivity of groundwater flow to topography, variable matrix permeability distribution models, pore-water salinity, and the dissipation of elevated initial pore pressures that result from ice that overlaid the watershed in the last glacial period. Groundwater flow analyses indicate that freshwater heads in all model layers are highly correlated with the complex surface topography such that the transition from zones of groundwater recharge to zones of discharge occurs over distances that can be relatively short. Shallow flow to a depth of tens of metres dominates the overall water balance, and the length of flow paths is relatively short. The analyses of this study indicate that the flow in deeper rock is not regional but rather is a subdued reflection of the local-scale surface topography.
Measuring shear and compression wave velocities of soil using bender–extender elements
Authors: Leong E. C. , Cahyadi J. , Rahardjo H. 
Published: July 2009

Piezoceramic elements have been used for laboratory measurement of wave velocity in soil and rock specimens. Shear-wave piezoceramic elements (bender elements) are commonly used to measure shear wave velocity for the determination of small-strain shear modulus. Compression-wave piezoceramic elements (extender elements), on the other hand, are less commonly used as compression wave velocity is less frequently measured. In this paper, the performance of a pair of bender–extender elements for the determination of both shear and compression wave velocities is examined with respect to the resolution of the recorder, bender–extender element size. and excitation voltage frequency. The evaluation showed that the performance of the bender–extender elements test can be improved by considering the following conditions: (i) the digital oscilloscope used to record the bender–extender element signals should have a high analog to digital (A/D) conversion resolution; (ii) the size of the bender–extender elements plays an important role in the strength and quality of the receiver signal, especially for compression waves; and (iii) using a wave path length to wavelength ratio of 3.33 enables a more reliable determination of shear wave velocity.
Bond activation by group-11 transition-metal cations
Authors: de Jong G. Theodoor , Bickelhaupt F. Matthias 
Published: July 2009

We have computationally explored C–X bond activation by the group-11 transition-metal cations Cu+, Ag+, and Au+, and, for comparison, Pd, using relativistic density functional theory (DFT) at ZORA-BLYP/TZ2P. Oxidative insertion of the second-row transition-metal species Ag+and Pd leads, for a given bond, to the highest overall reaction barriers. On the other hand, if we compare the different bonds oxidative insertion into the C–F bond is associated with (one of the) highest overall barriers whereas insertion into the C–Cl bond leads to the lowest overall barrier for any transition metal. The main trends in reactivity are rationalized using the activation strain model of chemical reactivity, which is an extension of the fragment approach to reaction profiles. In this model, the shape of the reaction profile ΔE(ζ) and the height of the overall reaction barrier ΔE≠= ΔE(ζ=ζTS) are interpreted in terms of the strain energy ΔEstrain(ζ) associated with deforming the reactants along the reaction coordinate ζ plus the interaction energy ΔEint(ζ) between these deformed reactants: ΔE(ζ) = ΔEstrain(ζ) + ΔEint(ζ).
Relativistic hybrid density functional calculations of indirect nuclear spin–spin coupling tensors — Comparison with experiment for diatomic alkali metal halides,
Authors: Bryce David L. , Autschbach Jochen 
Published: July 2009

The accurate calculation of the isotropic (Jiso) and anisotropic (ΔJ) parts of indirect nuclear spin–spin coupling tensors is a stringent test for quantum chemistry, particularly for couplings involving heavy isotopes where relativistic effects and relativity – electron correlation cross terms are expected to play an important role. Experimental measurements on diatomic molecules in the gas phase offer ideal data for testing the success of computational approaches, since the data are essentially free from intermolecular effects, and precise coupling anisotropies may be reliably extracted in favourable cases. On the basis of available experimental molecular-beam coupling-tensor parameters for diatomic alkali metal halides, we tabulate known values of Jiso and, taking rotational–vibrational corrections to the direct dipolar coupling constant into account, precise values of ΔJ are determined for the ground rovibrational state. First-principles calculations of the coupling tensors were performed using a recently developed program based on hybrid density functional theory using the two-component relativistic zeroth-order regular approximation (ZORA). Experimental trends in Jiso and ΔJ are reproduced with correlation coefficients of 0.993 and 0.977, respectively. Periodic trends in the coupling constants and their dependence on the product of the atomic numbers of the coupled nuclei are discussed. Finally, the hybrid functional method is also successfully tested against experimental data for a series of polyatomic xenon fluorides and group-17 fluorides.
Spin–orbit ab initio investigation of the UV photoinduced bond cleavage in iodotrimethylstannane
Authors: Ben Amor N. , Daniel C. 
Published: July 2009

The photoinduced homolytic cleavage of the Sn–I bond in iodotrimethylstannane (CH3)3SnI, observed after UV irradiation, is investigated by means of spin–orbit ab initio calculations based on CASSCF (complete active space self-consistent field) and MS-CASPT2 (multi-state complete active space 2nd order perturbation theory) methods. The absorption electronic spectrum is characterized by ten low-lying 1,3A′ and 1,3A″ spin eigenstates corresponding to py(I),px(I) → σ*SnI; σSnI → σ*SnI and py(Sn), px(Sn) → σ*SnI, where σSnI and σ*SnI are the bonding and anti-bonding orbitals of the Sn–I bond along the pz axis. From the 1A′ electronic ground state and these ten spin eigenstates, 21 spin–orbit states are generated leading to various deactivation channels of (CH3)3SnI, corresponding to the formation of radicals (CH3)3Sn• and •I and to the ionic species (CH3)3Sn+ and I–. Irradiation into the upper band at 175 nm should lead to the heterolytic cleavage of the Sn–I bond to form the ionic primary products exclusively, whereas absorption into the shoulder at 250 nm induces the homolytic breaking with formation of the radical products.
Binding of polar monomers in the complexes with organometallic ethylene polymerization catalysts — Natural orbitals for chemical valence and energy decomposition analysis
Authors: Srebro Monika , Mitoraj Mariusz , Michalak Artur 
Published: July 2009

The binding mode of polar monomers in complexes with late-transition-metal catalysts for ethylene polymerization was studied by density functional theory (DFT) calculations. The Ziegler–Rauk energy decomposition scheme was used to characterize the geometry distortion and steric and orbital-interaction terms in the bonding energy, while Natural Orbitals for Chemical Valence (NOCV) were applied to describe the donation and back-bonding components of the bond between the monomer and the catalyst. The NOCV analysis allowed for comparison of the donor–acceptor properties of different monomers in the σ- and π-complexes. The complexes with the model, cationic Ni– or Pd–diimine catalysts, N^N–Ni(H)+ and N^N–Pd(H)+, and the neutral Ni–anilinotropone system, N^O–Ni(H), were investigated. The monomers studied included: simple olefins (Et and Pr); examples of oxygen- and nitrogen-containing polar monomers (methyl acrylate (MA), vinyl acetate (VAc), their fluorinated derivatives (FMA, FVAc), vinyl ether (VE), acrylonitrile (AN), and β-butenoic nitrile (BN); vinyl and allyl amines (VAm, PrAm); and a tertiary dimethyl vinyl amine (MVAm). The results demonstrate that the metal-based fragment has a significant influence on the relative stability of the σ- and π-complexes; the π-binding mode increases in the following order: N^N–Ni(H)+ < N^N–Pd(H)+ < N^O–Ni(H). The results of the Ziegler–Rauk bond-energy decomposition indicate that for some monomers (MA, FMA, VAc, AN, VAm, MVAm) the preference of the coordination mode has a steric (electrostatic and Pauli) origin. For other monomers (VE, FVAc, BN, PrAm) the changes in the orbital-interaction terms are important as well. The results of the NOCV analysis indicate that for both, σ- and π-coordination modes there exist components describing σ-donation and π-back-bonding. The sequences of σ-donor and π-acceptor properties of monomers in the π-complexes as well as σ-complexes are similar for the considered catalysts.
A solid-state 31P NMR study of 1:1 silver–triphenylphosphine complexes — Interpretation of 1J(107,109Ag,31P) values,
Authors: Chen Fu , Oh Se-Woung , Wasylishen Roderick E. 
Published: July 2009

High-resolution solid-state 31P NMR spectroscopy was used to investigate a series of 1:1 silver–triphenylphosphine complexes, [Ph3PAgX]n, where X is a monovalent anion and n = 1, 2, 3, 4, or ∞. The 31P CP MAS NMR spectra reveal the number of distinct phosphorus sites in these complexes as well as the |1J(109Ag,31P)| values, which range from 401 ± 10 Hz (X = N3–) to 869 ± 10 Hz (X = SO3CF3–). The data obtained here and in earlier investigations indicate that |1J(109Ag,31P)| values for silver–tertiary phosphine complexes decrease as Ag–P bond lengths increase. This experimental conclusion is supported by DFT calculations, which also indicate that the Fermi-contact mechanism is the only important spin–spin coupling mechanism for 1J(109Ag,31P) in these complexes. In addition, the crystal structure of a silver–triphenylphosphine trifluoroacetate tetramer was determined using X-ray crystallography, and the structure of a silver–triphenylphosphine chloride tetramer was reinvestigated.
Contrasting total carbon stocks between ecological site series in a subboreal spruce research forest in central British Columbia
Authors: Bois Claudette H. , Janzen Darren T. , Sanborn Paul T. , Fredeen Arthur L. 
Published: July 2009

A study was conducted to determine if consideration of ecological site classification in combination with stand age would describe total ecosystem carbon (C) better than consideration of just stand age alone. The research was conducted in the 9250 ha University of Northern British Columbia/The University of British Columbia Aleza Lake Research Forest in central British Columbia. Over three field seasons (2003–2005), 38, 72, and 27 plots were established in mesic, subhygric, and hygric stands, respectively, with stand ages ranging from 5 to 350+ years. Mineral soil C stocks were significantly influenced by moisture regime, where hygric > subhygric > mesic (93, 77, and 65 t C·ha–1, respectively). Mineral soil and forest floor C stocks were not related to stand age, indicating their resilience to partial-cut and clear-cut forest harvesting systems historically implemented throughout the study area. Subhygric stands had the highest total ecosystem C stocks in the Aleza Lake Research Forest, having approximately 18% more C than mesic and hygric stands, principally due to higher mineral soil C stocks (than mesic stands) and improved C sequestration in large trees (over hygric stands). Consideration of ecological site classification in addition to stand age information improved total ecosystem C stock estimates over the use of stand age alone.
Diameter of lodgepole pine and mortality caused by the mountain pine beetle: factors that influence their relationship and applicability for susceptibility rating
Authors: Björklund Niklas , Lindgren B. Staffan 
Published: July 2009

During outbreaks the mountain pine beetle ( Dendroctonus ponderosae Hopkins) kills large lodgepole pine trees ( Pinus contorta Dougl. ex Loud.) more frequently than smaller ones. There is, however, considerable variation in the relation of diameter to incidence of attack. In a meta-analysis of published data we found that the relationship was primarily determined by geographic location (elevation, latitude, and longitude). We propose a new tree mortality measure, the probability of death index, defined as the average percentage of mortality for trees >23 cm. The index may improve the precision in predictive modeling of tree mortality, as it provides a biologically relevant measure of mortality, since it only includes trees that contribute to the growth of an epidemic and is not influenced by the number of trees within a diameter class. To be useful to forest managers, it must be possible to predict the index from stand parameters that are easily measured. The usefulness of the index was supported by a meta-analysis, which showed that 53% of the variation in the mortality index was explained by geographic location. Tree density did not explain any additional variation. Future research is needed to evaluate the performance of the probability of death index compared with that of other mortality measures.
Sequestration of carbon in the humus layer of Swedish forests — direct measurements
Authors: Berg Björn , Johansson Maj-Britt , Nilsson Åke , Gundersen Per , Norell Lennart 
Published: July 2009

To determine sequestration rates of carbon dioxide (CO2) we calculated the carbon (C) storage rate in humus layers of Swedish forests with Podsolic soils, which account for 14.2 × 106ha of the 22.7 × 106ha of forested land in Sweden. Our data set covered 41 years of humus inventories and mean humus layer thickness in 82 513 plots. We analysed three forest types: (i) all combinations of tree species, (ii) forests dominated (>70%) by Norway spruce ( Picea abies (L.) Karst.), and (iii) forests dominated (>70%) by Scots pine ( Pinus sylvestris L.). To relate changes in humus layer thickness to land area we used the intersections in 25 km × 25 km grids and used kriging interpolation, permitting calculations for each forest type. For each intersection mean humus thickness for each year was calculated and regressed against time to obtain the rate of change. This rate, humus bulk density, and humus C concentration were used to calculate sequestration rates. The mean sequestration rate was 251 kg C·ha–1·year–1, which is higher than theoretical values. The sequestration rate was positively related to temperature sum, albeit including effects of forest management. The pine-dominated forest type had a mean rate of 283 kg C·ha–1·year–1, and the spruce-dominated had a mean rate of 239 kg C·ha–1·year–1. Under similar site conditions, pine sequestered more C than spruce (difference of 71 kg C·ha–1·year–1; p < 0.0001), showing the importance of this type of ecosystem for C sequestration.