bluuebunny/crossref_metadata_2025 huggingface dataset:
Cost‐Benefit Appraisal of Screening for Congenital Dislocation of the Hip
Authors: Kernohan W. George , Trainor Bernadette P. , Mollan Raynold A.B. , Normand Charles E.M.
Published: May 2008

Vibration arthrometry is a new non‐invasive technique which detects, records and analyses vibrations elicited during clinical examination of human joints. In congenital dislocation of the hip, the computer‐based method has been developed to achieve a more objective and earlier diagnosis than is otherwise available. This is a condition of 0.2 per cent incidence with which a child may be born or which can develop shortly after birth. If a diagnosis is achieved soon after birth, the treatment is simple, cheap and effective. However, if the disease is not diagnosed until the child is walking, treatment is complicated and expensive and the child will need lengthy hospitalisation with a poor prognosis. An evaluation was made of three options: existing screening system, higher level screening and use of the Belfast Hip Screener.
AUTOREGRESSIVE PROCESSES WITH NORMAL STATIONARY DISTRIBUTIONS
Authors: Petruccelli Joseph D.
Published: May 2008

Abstract. For the strictly stationary AR(k) process Zt=Λ(Zt‐1) +αt, with Λ:Rk→R, Zt‐1= [Zt‐1, Zt‐2,…,Zt‐k] and {αt} an independent identically distributed white noise process, we partially characterize the Λ for which the stationary distribution of Zt is normal.
Three C‐terminal residues from the sulphonylurea receptor contribute to the functional coupling between the KATP channel subunits SUR2A and Kir6.2
Authors: Dupuis Julien P. , Revilloud Jean , Moreau Christophe J. , Vivaudou Michel
Published: May 2008

Cardiac ATP‐sensitive potassium (KATP) channels are metabolic sensors formed by the association of the inward rectifier potassium channel Kir6.2 and the sulphonylurea receptor SUR2A. SUR2A adjusts channel gating as a function of intracellular ATP and ADP and is the target of pharmaceutical openers and blockers which, respectively, up‐ and down‐regulate Kir6.2. In an effort to understand how effector binding to SUR2A translates into Kir6.2 gating modulation, we examined the role of a 65‐residue SUR2A fragment linking transmembrane domain TMD2 and nucleotide‐binding domain NBD2 that has been shown to interact with Kir6.2. This fragment of SUR2A was replaced by the equivalent residues of its close homologue, the multidrug resistance protein MRP1. The chimeric construct was expressed in Xenopus oocytes and characterized using the patch‐clamp technique. We found that activation by MgADP and synthetic openers was greatly attenuated although apparent affinities were unchanged. Further chimeragenetic and mutagenetic studies showed that mutation of three residues, E1305, I1310 and L1313 (rat numbering), was sufficient to confer this defective phenotype. The same mutations had no effects on channel block by the sulphonylurea glibenclamide or by ATP, suggesting a role for these residues in activatory – but not inhibitory – transduction processes. These results indicate that, within the KATP channel complex, the proximal C‐terminal of SUR2A is a critical link between ligand binding to SUR2A and Kir6.2 up‐regulation.
Molecular, pharmacological and functional properties of GABAA receptors in anterior pituitary cells
Authors: Zemkova Hana W. , Bjelobaba Ivana , Tomic Melanija , Zemkova Hana , Stojilkovic Stanko S.
Published: May 2008

Anterior pituitary cells express γ‐aminobutyric acid (GABA)‐A receptor‐channels, but their structure, distribution within the secretory cell types, and nature of action have not been clarified. Here we addressed these questions using cultured anterior pituitary cells from postpubertal female rats and immortalized αT3‐1 and GH3 cells. Our results show that mRNAs for all GABAA receptor subunits are expressed in pituitary cells and that α1/β1 subunit proteins are present in all secretory cells. In voltage‐clamped gramicidin‐perforated cells, GABA induced dose‐dependent increases in current amplitude that were inhibited by bicuculline and picrotoxin and facilitated by diazepam and zolpidem in a concentration‐dependent manner. In intact cells, GABA and the GABAA receptor agonist muscimol caused a rapid and transient increase in intracellular calcium, whereas the GABAB receptor agonist baclofen was ineffective, suggesting that chloride‐mediated depolarization activates voltage‐gated calcium channels. Consistent with this finding, RT‐PCR analysis indicated high expression of NKCC1, but not KCC2 cation/chloride transporter mRNAs in pituitary cells. Furthermore, the GABAA channel reversal potential for chloride ions was positive to the baseline membrane potential in most cells and the activation of ion channels by GABA resulted in depolarization of cells and modulation of spontaneous electrical activity. These results indicate that secretory pituitary cells express functional GABAA receptor‐channels that are depolarizing.
The Serine Protease TMPRSS6 Is Required to Sense Iron Deficiency
Authors: Du Xin , She Ellen , Gelbart Terri , Truksa Jaroslav , Lee Pauline , Xia Yu , Khovananth Kevin , Mudd Suzanne , Mann Navjiwan , Moresco Eva Marie Y. , Beutler Ernest , Beutler Bruce
Published: May 2008

Hepcidin, a liver-derived protein that restricts enteric iron absorption, is the key regulator of body iron content. Several proteins induce expression of the hepcidin-encoding gene
Hamp
in response to infection or high levels of iron. However, mechanism(s) of
Hamp
suppression during iron depletion are poorly understood. We describe
mask
: a recessive, chemically induced mutant mouse phenotype, characterized by progressive loss of body (but not facial) hair and microcytic anemia. The
mask
phenotype results from reduced absorption of dietary iron caused by high levels of hepcidin and is due to a splicing defect in the transmembrane serine protease 6 gene
Tmprss6
. Overexpression of normal TMPRSS6 protein suppresses activation of the
Hamp
promoter, and the TMPRSS6 cytoplasmic domain mediates
Hamp
suppression via proximal promoter element(s). TMPRSS6 is an essential component of a pathway that detects iron deficiency and blocks
Hamp
transcription, permitting enhanced dietary iron absorption.
Dislocation-Driven Nanowire Growth and Eshelby Twist
Authors: Bierman Matthew J. , Lau Y. K. Albert , Kvit Alexander V. , Schmitt Andrew L. , Jin Song
Published: May 2008

Hierarchical nanostructures of lead sulfide nanowires resembling pine trees were synthesized by chemical vapor deposition. Structural characterization revealed a screwlike dislocation in the nanowire trunks with helically rotating epitaxial branch nanowires. It is suggested that the screw component of an axial dislocation provides the self-perpetuating steps to enable one-dimensional crystal growth, in contrast to mechanisms that require metal catalysts. The rotating trunks and branches are the consequence of the Eshelby twist of screw dislocations with a dislocation Burgers vector along the 〈110〉 directions having an estimated magnitude of 6 ± 2 angstroms for the screw component. The results confirm the Eshelby theory of dislocations, and the proposed nanowire growth mechanism could be general to many materials.
The Extracellular Metalloprotease ofVibrio tubiashiiIs a Major Virulence Factor for Pacific Oyster (Crassostrea gigas) Larvae
Authors: Hasegawa Hiroaki , Lind Erin J. , Boin Markus A. , Häse Claudia C.
Published: May 2008

Vibrio tubiashiiis a recently reemerging pathogen of larval bivalve mollusks, causing both toxigenic and invasive disease. MarineVibriospp. produce an array of extracellular products as potential pathogenicity factors. Culture supernatants ofV. tubiashiihave been shown to be toxic to oyster larvae and were reported to contain a metalloprotease and a cytolysin/hemolysin. However, the structural genes responsible for these proteins have yet to be identified, and it is uncertain which extracellular products play a role in pathogenicity. We investigated the effects of the metalloprotease and hemolysin secreted byV. tubiashiion its ability to kill Pacific oyster (Crassostrea gigas) larvae. WhileV. tubiashiisupernatants treated with metalloprotease inhibitors severely reduced the toxicity to oyster larvae, inhibition of the hemolytic activity did not affect larval toxicity. We identified structural genes ofV. tubiashiiencoding a metalloprotease (vtpA) and a hemolysin (vthA). Sequence analyses revealed that VtpA shared high homology with metalloproteases from a variety ofVibriospecies, while VthA showed high homology only to the cytolysin/hemolysin ofVibrio vulnificus. Compared to the wild-type strain, a VtpA mutant ofV. tubiashiinot only produced reduced amounts of protease but also showed decreased toxicity toC. gigaslarvae.Vibrio choleraestrains carrying thevtpAorvthAgene successfully secreted the heterologous protein. Culture supernatants ofV. choleraecarryingvtpAbut notvthAwere highly toxic to Pacific oyster larvae. Together, these results suggest that theV. tubiashiiextracellular metalloprotease is important in its pathogenicity toC. gigaslarvae.
Insights into the Mode of Action of Chitosan as an Antibacterial Compound
Authors: Raafat Dina , von Bargen Kristine , Haas Albert , Sahl Hans-Georg
Published: May 2008

Chitosan is a polysaccharide biopolymer that combines a unique set of versatile physicochemical and biological characteristics which allow for a wide range of applications. Although its antimicrobial activity is well documented, its mode of action has hitherto remained only vaguely defined. In this work we investigated the antimicrobial mode of action of chitosan using a combination of approaches, including in vitro assays, killing kinetics, cellular leakage measurements, membrane potential estimations, and electron microscopy, in addition to transcriptional response analysis. Chitosan, whose antimicrobial activity was influenced by several factors, exhibited a dose-dependent growth-inhibitory effect. A simultaneous permeabilization of the cell membrane to small cellular components, coupled to a significant membrane depolarization, was detected. A concomitant interference with cell wall biosynthesis was not observed. Chitosan treatment ofStaphylococcus simulans22 cells did not give rise to cell wall lysis; the cell membrane also remained intact. Analysis of transcriptional response data revealed that chitosan treatment leads to multiple changes in the expression profiles ofStaphylococcus aureusSG511 genes involved in the regulation of stress and autolysis, as well as genes associated with energy metabolism. Finally, a possible mechanism for chitosan's activity is postulated. Although we contend that there might not be a single classical target that would explain chitosan's antimicrobial action, we speculate that binding of chitosan to teichoic acids, coupled with a potential extraction of membrane lipids (predominantly lipoteichoic acid) results in a sequence of events, ultimately leading to bacterial death.
Microbial Communities in Contaminated Sediments, Associated with Bioremediation of Uranium to Submicromolar Levels
Authors: Cardenas Erick , Wu Wei-Min , Leigh Mary Beth , Carley Jack , Carroll Sue , Gentry Terry , Luo Jian , Watson David , Gu Baohua , Ginder-Vogel Matthew , Kitanidis Peter K. , Jardine Philip M. , Zhou Jizhong , Criddle Craig S. , Marsh Terence L. , Tiedje James M.
Published: May 2008

Microbial enumeration, 16S rRNA gene clone libraries, and chemical analysis were used to evaluate the in situ biological reduction and immobilization of uranium(VI) in a long-term experiment (more than 2 years) conducted at a highly uranium-contaminated site (up to 60 mg/liter and 800 mg/kg solids) of the U.S. Department of Energy in Oak Ridge, TN. Bioreduction was achieved by conditioning groundwater above ground and then stimulating growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria in situ through weekly injection of ethanol into the subsurface. After nearly 2 years of intermittent injection of ethanol, aqueous U levels fell below the U.S. Environmental Protection Agency maximum contaminant level for drinking water and groundwater (<30 μg/liter or 0.126 μM). Sediment microbial communities from the treatment zone were compared with those from a control well without biostimulation. Most-probable-number estimations indicated that microorganisms implicated in bioremediation accumulated in the sediments of the treatment zone but were either absent or in very low numbers in an untreated control area. Organisms belonging to genera known to include U(VI) reducers were detected, including
Desulfovibrio, Geobacter, Anaeromyxobacter, Desulfosporosinus
, and
Acidovorax
spp. The predominant sulfate-reducing bacterial species were
Desulfovibrio
spp., while the iron reducers were represented by
Ferribacterium
spp. and
Geothrix
spp. Diversity-based clustering revealed differences between treated and untreated zones and also within samples of the treated area. Spatial differences in community structure within the treatment zone were likely related to the hydraulic pathway and to electron donor metabolism during biostimulation.
Assessment of Gut Bacteria for a Paratransgenic Approach To Control
Dermolepida albohirtum
Larvae
Authors: Pittman Geoffrey W. , Brumbley Stevens M. , Allsopp Peter G. , O'Neill Scott L.
Published: May 2008

Bacteria from the hindguts of
Dermolepida albohirtum
larvae were assessed for their potential to be used in paratransgenic strategies that target scarab pests of sugarcane. Bacteria isolated in pure culture from the hindguts of
D. albohirtum
larvae were from the
Proteobacteria
,
Firmicutes
, and
Actinobacteria
phyla and matched closely with taxa from intestinal and rhizosphere environments. However, these isolates were not the most common gut-associated bacteria identified in denaturing gradient gel electrophoresis (DGGE) hindgut profiles. Subsequently, eight species of gut bacteria were fed to larvae, and RNA-based DGGE analysis of 16S rRNA was used to detect the persistence of these isolates in the hindgut environment. One of these isolates (Da-11) remained metabolically active in the hindgut for 19 days postconsumption. Da-11 most likely forms a new genus within the
Burkholderiales
order, along with taxa independently identified from larvae of the European scarab pest,
Melolontha melolontha
. Using the EZ::Tn
5
transposon system, a kanamycin resistance gene was inserted into the chromosome of Da-11, thus establishing a stable transformation technique for this species. A second feeding trial that included inoculating approximately 400 transgenic Da-11 cells onto a food source resulted in a density of 1 × 10
6
transgenic Da-11 cells/ml in the hindguts of larvae at 9 days postconsumption. These populations were maintained in the hindgut for at least another 12 days. The successful isolation, genetic transformation, and establishment of transgenic Da-11 cells in the hindguts of
D. albohirtum
larvae fulfill fundamental requirements for the future development of a paratransgenic approach to control scarab pests of sugarcane.
Functional Characterization of CgCTR2, a Putative Vacuole Copper Transporter That Is Involved in Germination and Pathogenicity inColletotrichum gloeosporioides
Authors: Barhoom Sima , Kupiec Martin , Zhao Xinhua , Xu Jin-Rong , Sharon Amir
Published: May 2008

Copper is a cofactor and transition metal involved in redox reactions that are essential in all eukaryotes. Here, we report that a vacuolar copper transporter that is highly expressed in resting spores is involved in germination and pathogenicity in the plant pathogenColletotrichum gloeosporioides. A screen ofC. gloeosporioidestransformants obtained by means of a promoterless green fluorescent protein (GFP) construct led to the identification of transformant N159 in which GFP signal was observed in spores. The transforming vector was inserted 70 bp upstream of a putative gene with homology to theSaccharomyces cerevisiaevacuolar copper transporter geneCTR2. TheC. gloeosporioides CTR2(CgCTR2) gene fully complemented growth defects of yeastctr2Δ mutants, and a CgCTR2-cyan fluorescent protein (CFP) fusion protein accumulated in vacuole membranes, confirming the function of the protein as a vacuolar copper transporter. Expression analysis indicated that CgCTR2transcript is abundant in resting conidia and during germination in rich medium and downregulated during “pathogenic” germination and the early stages of plant infection. CgCTR2overexpression and silencing mutants were generated and characterized. The Cgctr2mutants had markedly reduced Cu superoxide dismutase (SOD) activity, suggesting that CgCTR2 is important in providing copper to copper-dependent cytosolic activities. The Cgctr2-silenced mutants had increased sensitivity to H2O2and reduced germination rates. The mutants were also less virulent to plants, but they did not display any defects in appressorium formation and penetration efficiency. An external copper supply compensated for the hypersensitivity to H2O2but not for the germination and pathogenicity defects of the mutants. Similarly, overexpression of CgCTR2enhanced resistance to H2O2but had no effect on germination or pathogenicity. Our results show that copper is necessary for optimal germination and pathogenicity and that CgCTR2 is involved in regulating cellular copper balance during these processes.
Mutagenesis of theShigella flexneriAutotransporter IcsA Reveals Novel Functional Regions Involved in IcsA Biogenesis and Recruitment of Host Neural Wiscott-Aldrich Syndrome Protein
Authors: May Kerrie L. , Morona Renato
Published: May 2008

The IcsA (VirG) protein ofShigella flexneriis a polarly localized, outer membrane protein that is essential for virulence. Within host cells, IcsA activates the host actin regulatory protein, neural Wiskott-Aldrich syndrome protein (N-WASP), which in turn recruits the Arp2/3 complex, which nucleates host actin to form F-actin comet tails and initiate bacterial motility. Linker insertion mutagenesis was undertaken to randomly introduce 5-amino-acid in-frame insertions within IcsA. Forty-seven linker insertion mutants were isolated and expressed inS. flexneriΔicsAstrains. Mutants were characterized for IcsA protein production, cell surface expression and localization, intercellular spreading, F-actin comet tail formation, and N-WASP recruitment. Using this approach, we have identified a putative autochaperone region required for IcsA biogenesis, and our data suggest an additional region, not previously identified, is required for N-WASP recruitment.
Cortex Peptidoglycan Lytic Activity in Germinating
Bacillus anthracis
Spores
Authors: Dowd Melissa M. , Orsburn Benjamin , Popham David L.
Published: May 2008

Bacterial endospore dormancy and resistance properties depend on the relative dehydration of the spore core, which is maintained by the spore membrane and its surrounding cortex peptidoglycan wall. During spore germination, the cortex peptidoglycan is rapidly hydrolyzed by lytic enzymes packaged into the dormant spore. The peptidoglycan structures in both dormant and germinating
Bacillus anthracis
Sterne spores were analyzed. The
B. anthracis
dormant spore peptidoglycan was similar to that found in other species. During germination,
B. anthracis
released peptidoglycan fragments into the surrounding medium more quickly than some other species. A major lytic enzymatic activity was a glucosaminidase, probably YaaH, that cleaved between
N
-acetylglucosamine and muramic-δ-lactam. An epimerase activity previously proposed to function on spore peptidoglycan was not detected, and it is proposed that glucosaminidase products were previously misidentified as epimerase products. Spore cortex lytic enzymes and their regulators are attractive targets for development of germination inhibitors to kill spores and for development of activators to cause loss of resistance properties for decontamination of spore release sites.
Omp85
Tt
from
Thermus thermophilus
HB27: an Ancestral Type of the Omp85 Protein Family
Authors: Nesper Jutta , Brosig Alexander , Ringler Philippe , Patel Geetika J. , Müller Shirley A. , Kleinschmidt Jörg H. , Boos Winfried , Diederichs Kay , Welte Wolfram
Published: May 2008

Proteins belonging to the Omp85 family are involved in the assembly of β-barrel outer membrane proteins or in the translocation of proteins across the outer membrane in bacteria, mitochondria, and chloroplasts. The cell envelope of the thermophilic bacterium
Thermus thermophilus
HB27 is multilayered, including an outer membrane that is not well characterized. Neither the precise lipid composition nor much about integral membrane proteins is known. The genome of HB27 encodes one Omp85-like protein, Omp85
Tt
, representing an ancestral type of this family. We overexpressed Omp85
Tt
in
T. thermophilus
and purified it from the native outer membranes. In the presence of detergent, purified Omp85
Tt
existed mainly as a monomer, composed of two stable protease-resistant modules. Circular dichroism spectroscopy indicated predominantly β-sheet secondary structure. Electron microscopy of negatively stained lipid-embedded Omp85
Tt
revealed ring-like structures with a central cavity of ∼1.5 nm in diameter. Single-channel conductance recordings indicated that Omp85
Tt
forms ion channels with two different conducting states, characterized by conductances of ∼0.4 nS and ∼0.65 nS, respectively.
Functional Analysis of the Essential GTP-Binding-Protein-Coding GenecgtAofVibrio cholerae
Authors: Shah Sangita , Das Bhabatosh , Bhadra Rupak K.
Published: May 2008

ThecgtAgene, coding for the conserved G protein CgtA, is essential in bacteria. In contrast to a previous report, here we show by using genetic analysis thatcgtAis essential inVibrio choleraeeven in a ΔrelAbackground. Depletion of CgtA affected the growth ofV. choleraeand rendered the cells highly sensitive to the replication inhibitor hydroxyurea. Overexpression ofV. choleraeCgtA caused distinct elongation ofEscherichia colicells. Deletion analysis indicated that the C-terminal end of CgtA plays a critical role in its proper function.
The Effect of Cross Interactions on Mixing Properties: Non-Lorentz-Berthelot Lennard-Jones Mixtures
Authors: Rouha Michael , Moučka Filip , Nezbeda Ivo
Published: May 2008

Binary mixtures of two identical Lennard-Jones fluids with non-Lorentz-Berthelot combining rules have been simulated at ambient-like conditions in order to examine the effect of cross interactions on mixing properties - excess volumes and enthalpies. Various combinations of deviations of both energy and size cross parameters from the Lorentz-Berthelot rules have been considered. Whereas consequences of the deviations for excess volume are rather straightforward, a variety of behavior types is found for excess enthalpy, including an excess function with three extrema.
Numerous chloroplast DNA polymorphisms are shared among different populations and species in the aureoid Senecio (Packera) complex
Authors: Bain J. F. , Jansen R. K.
Published: May 2008

Species boundaries within the aureoid Senecio complex (Packera) are poorly defined, possibly as a result of hybridization and introgression. The results of restriction site analysis of cpDNA using 16 enzymes and hybridization with lettuce probes representing over 95% of the chloroplast genome reveal a high level of intrapopulational polymorphism combined with a relatively low level of interspecific variation. Forty-nine populations representing 23 different species were examined, and only 20 variable restriction sites were identified. Eleven of the 20 variable sites were polymorphic in at least one population, and 14 of the 23 species were polymorphic for at least one site. The polymorphisms are widespread and are found in species representing all of the previously recognized subgroups of the aureoid complex. Individuals analyzed separately were shown to possess only a single haplorype. Although the polymorphisms may be the result of hybridization and introgression, it is difficult to explain the geographical patterns based on the current distribution of species. It is possible that the aureoid complex represents a single, polymorphic biological species. Keywords: Asteraceae, Senecio, aureoid complex, Packera, cpDNA, molecular systematics.
Quantifying organizational change after fire in lodgepole pine forest understorey
Authors: Brulisauer Alfred R. , Bradfield Gary E. , Maze Jack
Published: May 2008

Temporal changes in community organization were examined in a 300+ year chronosequence of understorey vegetation data from lodgepole pine forests recovering from fire in central British Columbia. Changes between six age-classes of forest were quantified as shifts in the orientation of equal frequency ellipses depicting the main correlation structure of the vegetation in multivariate space. Different developmental trajectories were obtained for sites differing in soil moisture status. Mesic sites displayed sharp changes in community organization within the first 100 years following fire but only gradual changes thereafter. In contrast, xeric sites exhibited sharp organizational changes at the beginning and again toward the end of the chronosequence. The unanticipated behaviour of dry sites is interpreted as reflecting a lower degree of integration of such communities resulting from their particular species composition and susceptibility to biotic disturbance. Analyses of separate life-form strata indicated continuing organizational changes in shrubs, forbs–grasses, and lichens, but relative stability in bryophytes after 100 years. The movement through time of mesic sites towards increasing persistence is predicted from an interpretation of ecological succession as a process of self-organization, directed by principles of nonequilibrium thermodynamics. Keywords: postfire succession, Pinus contorta forest understorey, plant community organization, equal frequency ellipses, principal components analysis, self-organization, nonequilibrium thermodynamics.
Cyclical closed-system freeze–thaw permeability testing of soil liner and cover materials
Authors: Wong Lionel C. , Haug Moir D.
Published: May 2008

The impact of closed-system freeze–thaw cycles on the permeability of clay, till, and sand–bentonite mixtures was examined in a laboratory test program. The bentonite content of the sand–bentonite mixtures varied from 4.5 to 25%. Test samples were prepared by dry mixing, moisture conditioning, and compacting materials according to ASTM D698, method A specifications. The molding water content of these samples was at or slightly wet of optimum. Trimmed test samples were placed in a triaxial permeameter and their unfrozen or initial permeability was established. These permeability tests were conducted for approximately 10 000 min using low hydraulic gradients and confining stress. Changes in specimen volume were also measured during permeability testing. Once the initial permeability of a specimen was established, the test was halted and the specimen was frozen inside the permeameter with no access to water. After freezing, the specimens were allowed to thaw before a second permeability test was conducted. This process of alternating permeability tests with freeze–thaw cycles was continued until the change in permeability between freeze–thaw cycles became insignificant. The results of this test program show that the permeabilities of both the clay and till specimens increase due to freeze–thaw cycles. In contrast, the sand–bentonite specimens showed no increase in permeability due to freeze–thaw cycles. Key words: closed system, freeze–thaw, permeability, volume change, soil liners, soil covers.
Comportement de la membrane d'argile d'un étang aéré en région froide
Authors: Leroueil Serge , Savard Yves , Bouchard Régis
Published: May 2008

To understand the causes and deduce the consequences of longitudinal fissures forming at the crest of slopes of many aeration ponds, a sealed clay liner has been instrumented and monitored over one winter. This paper describes the evolution of freezing and displacements. The latter were important and occasionally induced tension in the membrane below the water level. The practical implications are discussed. Key words: aeration ponds, compacted clay, freezing, deformations. [Journal translation]
The hydraulics problem in slope stability analysis
Authors: Windisch Étienne J.
Published: May 2008

Hydraulic pressures and forces are obtained on a typical slice, as used in current methods of slope stability analysis, under hydrostatic and flowing groundwater conditions. It is shown that current methods do not satisfy some basic hydraulics and soil mechanics principles. The effective normal stress on the lower boundary of a slice is shown to be underestimated, and the resultant hydraulic force is not accounted for adequately. Key words: effective stress, hydraulic pressure, hydraulic gradient, hydraulic force, slope stability.
The interpretation of horizontal and mixed-mode fractures in hydraulic fracturing tests in rocks
Authors: Hefny Ashraf , Lo K. Y.
Published: May 2008

For the design of underground structures in rocks, the states of initial stresses in the rock mass are required. For structures located at great depths, the hydraulic fracturing test for stress measurements is the only practical method. For vertical fractures, existing solutions for calculation of stresses from test results are satisfactory. For horizontal or mixed-mode fractures, appropriate solutions are required. Closed-form solutions for horizontal and mixed-mode fractures including strength anisotrophy are presented. The method enables the determination of which fracture (horizontal or vertical) occurs first at the first breakdown pressure during the test, so appropriate stress calculation may be carried out. Results of hydraulic fracturing tests in three case histories have been reanalyzed using the method developed. It is shown that for horizontal fractures the ranges of stress values computed are considerably reduced compared with existing solutions. The reinterpreted horizontal stresses in a case record are consistent with results of field observations in underground excavations. Experimental requirements for the measurements of rock parameters relevant to the specific stress paths in hydraulic fracturing tests are discussed. Key words : hydraulic fracturing, stress measurements, mixed-mode fractures, underground structures, rock strength.
Analysis of elliptic vanes
Authors: Silvestri Vincent , Tabib Claudette
Published: May 2008

This technical note presents the results of a theoretical analysis of smooth elliptic vanes. Uniform and triangular shear stress distributions are used to obtain geometric vane factors. A preliminary field investigation has been carried out by means of two elliptic vanes. Key words : vanes, elliptic shapes, uniform, triangular, shear stress distribution, field investigation.
A framework for the behaviour of unsaturated expansive clays
Authors: Gens A. , Alonso E. E.
Published: May 2008

The paper presents a framework for describing the mechanical behaviour of unsaturated expansive clays. It is an extension of an existing formulation developed for unsaturated soils of low activity. The extended framework is based on the distinction within the material of a microstructural level where the basic swelling of the active minerals takes place and a macrostructural level responsible for major structural rearrangements. By adopting simple assumptions concerning the coupling between the two levels, it is possible to reproduce major features of the behaviour of unsaturated expansive clays. Some selected qualitative comparisons between model predictions and experimental results reported in the literature are presented. Despite the simplified hypotheses made, a very encouraging agreement is obtained. Key words : capillarity, clay, model, unsaturation, suction, expansive soils.
Stress anisotropy and wave propagation: a micromechanical view
Authors: Santamarina J C , Cascante G
Published: May 2008

Wave propagation is a constant-fabric macrophenomenon, suitable to microinterpretation. Both velocity and attenuation characterize state, including inherent and stress-induced anisotropy. The purpose of this research is to study the effect of isotropic and deviatoric stresses on wave propagation in particulate materials at low strains and to interpret results at the microlevel. A resonant-column device was midified to allow for the application of axial extension and axial compression deviatoric loading. The fixed-free boundary condition of the sample was maintained. Data for round, hard-grained sand show that shear wave velocity and attenuation are primarily dependent on the mean stress on the polarization plane, with minimal effect of the deviatoric component, in agreement with prior observations at stress ratios less than 23. Attenuation is strongly correlated with the mean stress in the polarization plane and the level of shear strain. Damping does not vanish at low strains, contrary to predictions based on hysteretic behaviour; hence, other loss mechanisms must take place at low strains. Low-strain wave parameters are adequately corrected for mid-strain using modified hyperbolic models. Measured velocity and damping trends during isotropic and anisotropic loading qualitatively agree with predictions based on regular arrays.

Key words: mechanical waves, resonant column, damping, shear modulus, stress anisotropy, random vibration.
Three-dimensional stability analysis for slurry-filled trench wall in cohesionless soil
Authors: Tsai Jiin-Song , Chang Jia-Chyi
Published: May 2008

On the basis of the limiting equilibrium and arching theory, a three-dimensional analysis is proposed for slurry-supported trenches in cohesionless soils. This analytical approach is developed by considering the trench stability problem as a vertical soil cut within a fictitious half-silo with a rough wall surronding. Arching effects are considered not only in the vertical direction but also in the horizontal direction. A shell-shaped slip surface of the sliding soil mass is defined by Mohr-Coulomb criterion. The factor of safety is defines as the ratio of the resisting force induced by slurry pressure to the horizontal force required to maintain the stability of the trench wall. Results of the proposed method have been compared with those of two existing analytical methods for a typical trench stability problem.

Key words: stability analysis, slurry trench wall, cohesionless soil.
Effect of stress paths on the behaviour of sandsteel interfaces
Authors: Evgin Erman , Fakharian Kazem
Published: May 2008

An apparatus has been developed to carry out two- and three-dimensional tests on interfaces between soils and structural materials. The soil container facilitates both the sliding displacement at the interface and the shear deformation in the soil mass. The apparatus has the capability of maintaining the normal stiffness constant during shearing. In constant normal stiffness tests, the normal stress is adjusted continuously by a computer-controlled system to keep the normal stiffness at a desired value. In addition to constant normal stiffness tests, conventional types of tests can be performed during which the average normal stress acting on the interface is kept constant. In all types of three-dimensional tests, the interface can be subjected to tangential loading in two orhtogonal directions simultaneously. Experiments were conducted to study the two- and three-dimensional behaviour of an interface between a dense sand and a rough steel surface under both constant normal stress and constant normal stiffness conditions. The influence of various stress paths on the stressdisplacement relations and shear strength characteristics of the interface are investigated. The experimental results indicate that the coefficients of friction corresponding to the resultant peak and residual shear strengths are independent of stress paths. The shear stress  tangential displacement and volume change behaviour of the interface, however, are significantly influenced by stress paths.

Key words: interface testing, simple shear, peak and residual shear strength, three-dimensional, constant normal stiffness, stress path.
Case histories illustrate the importance of secondary-type consolidation settlements in the Fraser River delta
Authors: Crawford Carl B , Morrison K Ian
Published: May 2008

The technique of preloading the deep, compressible soils in the Fraser River delta has been used for more than 40 years to prevent excessive settlement of major structures. This paper documents 22 years of settlement under preloading and after construction of the facilities for a major waste water treatment plant in the delta. These results are similar to observations for as long as 28 years at five additional sites in the delta. It was found that as much as one half of the measured surface settlement occured during or within a few weeks of the full apllication of the preload and that subsequent settlements have the characteristics of secondary consolidation. This could not have been predicted from laboratory tests, and it raises questions concerning the true nature of consolidation in situ. For practical purposes the observations provide guidance for the prediction of long-term settlements in the region.

Key words: case history, consolidation, field observations, preloading, settlement.
Densification of domestic waste fills by dynamic compaction
Authors: Van Impe William F , Bouazza Abdelmalek
Published: May 2008

Dynamic compaction of solid waste is important in landfill operations because increasing the density of the material increases the storage capacity of the landfill. Differential settlements are also reduced, which is important for the integrity of the cover system. In this paper, a case study concerning a waste disposal site situated at Maldegem, Belgium, is presented. It is shown that young landfills behave differently from old landfills. This phenomenon results from the biodegradation of the wastes. Moreover, it is shown that the depth of influence, the crater depth, the enforced settlement, and the peak particle velocity are affected by this ageing process.

Key words: dynamic compaction, landfills, SASW method, waste.
Bottom-heave control of a deep sensitive clay excavation in Ottawa, Canada
Authors: McRostie G C , Morissette L , St-Louis M W
Published: May 2008

For a new Police Headquarters Complex in Ottawa, an excavation was required to a depth of 10 m in medium to stiff sensitive silty clays and clayey silts. The risk of a bottom-heave failure due to uplift caused by significant groundwater pressures in the silty soil a few metres below the bottom of the excavation was recognized, and contract requirements included a wellpoint installation assisted by electro-osmosis. The successful bidder was able to develop an alternative method based on the observational approach and completed the foundation at a lesser cost. A small test excavation was instrumented, and digging proceeded cautiously to full depth. The observed bottom heave and pore pressure changes were encouraging, so the test area was enlarged in steps until a workable size of excavation was safely made, then the structural raft was able to be placed. A backup system of pore pressure relief wells using wick drains in the bottom of the excavation was also developed. A large pore pressure reduction, due to the release of overburden pressure, was expected by the contractor's consultant, and a slow regain of the groundwater pressure was also expected due to the low horizontal permeabilities involved. The test excavation instrumentation and observations confirmed these expectations.

Key words: bottom heave, excavation, clay, pore pressure.
Reliability of thin-walled cylinder tests for elastic properties of anisotropic rocks
Authors: Talesnick M L
Published: May 2008

Elastic properties of transverse isotropic rocks may be theoretically determined by subjecting a single hollow cylinder specimen to a set of two simple stress conditions. The reliability of the methodology is considered by testing both thin-walled hollow cylinders and thick-walled hollow cylinders. The results indicate that the testing procedure produces consistent material parameters, sample preparation does not seem to induce changes in the specimen behaviour, and that the assumptions implemented in the determination of the material parameters are reasonable.

Key words: hollow cylinder, anisotropy, elasticity, test method.
Sapling growth as a function of resources in a north temperate forest
Authors: Pacala Stephen W. , Canham Charles D. , Silander Jr. John A. , Kobe Richard K.
Published: May 2008

Radial and height growth are characterized for saplings of 10 dominant tree species in a transition oak–northern hardwoods forest in southern New England. Growth of saplings in the field is regressed against measures of whole-season light availability, soil moisture, and sapling size. Statistical tests show strong effects of light availability on growth, but no significant effects of soil moisture. Comparison of the light-dependent growth functions for the 10 species revealed three apparent interspecific trade-offs. (i) Species growing quickly at high light tended to grow slowly at low light and vice versa. The order of species from fast growing at high light to fast growing at low light did not correspond to traditional classifications of shade tolerance, and variation along this axis was approximately continuous. (ii) There was substantial variation off the species continuum defined in i. At any point along the continuum from fast growth at high light to fast growth at low light, some species grew faster than others, and these faster growing species had lower survivorship during periods of suppression than the slower growing species. (iii) Height growth at high light was inversely related to survivorship when suppressed. This variation was again continuous (species did not cluster into discrete categories), but the order of the species did correspond closely to a traditional ordering of shade tolerance. There was little correspondence between our estimated growth functions and the growth functions assumed in the JABOWA–FORET class of forest simulation models. These results raise serious concerns about the current practice of assigning growth functions to species in simulation models using traditional classifications of shade tolerance.
Blue-stain fungi and their transport structures on the Douglas-fir beetle
Authors: Lewinsohn Dalia , Lewinsohn Efraim , Bertagnolli Catherine L. , Patridge Arthur D.
Published: May 2008

Parent and preflight-adult Douglas-fir beetles (Dendroctonuspseudotsugae Hopk., Coleoptera: Scolytidae) were collected from felled Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees. Fungi isolated from the beetles included blue-stain fungi, such as Ophiostomapseudotsugae (Rumbold) von Arx, Leptographiumterebrantis Barras & Perry, and Leptographiumabietinum (Peck) Wingfield; other ascomycetes, such as Graphium spp. and Leptographium spp.; yeasts; and unidentified basidiomycetes. All fungal cultures derived from parent beetles, preflight adults, beetle eggs, larvae, frass, and bark from galleries had yeasts present. Ophiostomapseudotsugae was isolated from 67% of the parent females, 19% of the parent males, and 100% of the preflight adults of both sexes collected from their pupal cells. Rinsing the beetles with 70% ethanol prior to fungus isolations reduced the frequency of all fungi, except yeasts. Parent and preflight adult beetles (of both sexes) were examined with a scanning electron microscope, where spores of O. pseudotsugae were visible in shallow pits on the elytra of both male and female beetles. Spores of other fungi were observed in shallow pits on elytra and in much smaller but deeper pits on the scutellum of both sexes. The results indicate a close association between Douglas-fir beetles and fungi, accompanied by anatomical differentiation on the beetles that allows the dissemination of blue-stain fungi to new Douglas-fir hosts and substrates.
DUAL BOSONIC THERMAL GREEN FUNCTION AND FERMION CORRELATORS OF THE MASSIVE THIRRING MODEL AT FINITE TEMPERATURE
Authors: MONDAINI LEONARDO , MARINO E. C.
Published: May 2008

The Euclidean thermal Green function of the two-dimensional (2D) free massless scalar field in coordinate space is written as the real part of a complex analytic function of a variable that conformally maps the infinite strip -∞ < x < ∞ (0 < τ < β) of the z = x + iτ (τ: imaginary time) plane into the upper-half-plane. Using this fact and the Cauchy–Riemann conditions, we identify the dual thermal Green function as the imaginary part of that function. Using both the thermal Green function and its dual, we obtain an explicit series expression for the fermionic correlation functions of the massive Thirring model (MTM) at a finite temperature.
DYNAMICS OF ENTANGLEMENT FOR TWO-ELECTRON ATOMS
Authors: OSENDA OMAR , SERRA PABLO , KAIS SABRE
Published: May 2008

We studied the dynamics of the entanglement for two electron atoms with initial states created from a superposition of the eigenstates of the two-electron Hamiltonian. We present numerical evidence that the pairwise entanglement for the two electrons evolves in a way that is strongly related with the time evolution of the Coulombic interaction between the two electrons.
A LOGIC FOR QUANTUM COMPUTATION AND CLASSICAL SIMULATION OF QUANTUM ALGORITHMS
Authors: PATRA M. K.
Published: May 2008

The semantics of a language for reasoning about finite-dimensional quantum systems is presented. This language can express most important classes of assertions about quantum systems, including formulas for outputs of all combinational quantum circuits/algorithms. The main result of this paper is an algorithm for efficient translation of a formula of language into an equivalent formula in another decidable language ℝℂ, which is the language of reals and its complex extension. An important consequence is a descriptive characterization of quantum circuits that can be efficiently simulated classically. We illustrate this with examples of two classes of quantum circuits which are known to have efficient classical simulation. The algorithm for deciding the satisfiability of a general formula can be adapted for the simulation.
(p)ppGpp: Still Magical?
Authors: Potrykus Katarzyna , Cashel Michael
Published: May 2008

The fundamental details of how nutritional stress leads to elevating (p)ppGpp are questionable. By common usage, the meaning of the stringent response has evolved from the specific response to (p)ppGpp provoked by amino acid starvation to all responses caused by elevating (p)ppGpp by any means. Different responses have similar as well as dissimilar positive and negative effects on gene expression and metabolism. The different ways that different bacteria seem to exploit their capacities to form and respond to (p)ppGpp are already impressive despite an early stage of discovery. Apparently, (p)ppGpp can contribute to regulation of many aspects of microbial cell biology that are sensitive to changing nutrient availability: growth, adaptation, secondary metabolism, survival, persistence, cell division, motility, biofilms, development, competence, and virulence. Many basic questions still exist. This review tries to focus on some issues that linger even for the most widely characterized bacterial strains.
Sulfonated Polyimide Membranes for Polymer Electrolyte Fuel Cells
Authors: Okamoto Ken-ichi , Matsuda Kousou , Hu Zhaoxia , Chen Kangcheng , Endo Noritaka , Higa Mitsuru
Published: May 2008

Sulfonated polyimides (SPIs) bearing sulfophenoxy side groups and their SO2-crosslinked membranes have been successfully prepared and evaluated as polymer electrolyte membranes for polymer electrolyte fuel cell (PEFC). They maintained high mechanical strength and proton conductivity after aging in water at 130 oC for 500 h. In a single fuel cell system at 90 oC, they showed high performance under a high humidity of 85 %RH and fairly high performance even under a low humidity of 30%RH due to the back diffusion of water formed at the cathode. The durability test was carried out for a PEFC with SO2-crosslinked SPI membrane under operation conditions of 0.5 A/cm2, 90 oC and 85 %RH for 1600 h. There were observed no reduction in OCV and cell voltage and no increase in cell resistance for 1600 h. The SPI membranes have high potential for PEFCs at higher temperatures above 80 oC.