bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-Elastic Analysis and Design of Sloshing in Floating-Roof Tanks Subjected to Earthquake Motions
Authors: Sakai Fujikazu , Inoue Ryousuke , Hayashi Shoichiro
Published: July 2008

During the 2003 Tokachi-oki, Japan earthquake, many oil tanks located in Tomakomai were damaged by sloshing due to the long-period strong ground motion. It is especially noted that the single-deck floating-roofs of seven tanks collapsed as they sank with the buckling failure of the pontoons, which resulted in fire accidents of two tanks. To clarify the cause of such damages, it is necessary to investigate in detail the sloshing behaviors in consideration of the existence of a floating-roof. However, so far most of the researches on sloshing have treated only the case of a free surface or the case of a rigid floating-roof, and have not considered the case of an elastic floating-roof, which is used in an actual tank. In this paper, the authors discuss the problem on the basis of fluid-elastic vibration analysis, that is, they investigate the sloshing behaviors of actual floating-roof models with single-deck type and double-deck type and indicate several important viewpoints on the seismic design which has hardly been taken into account hitherto.
Numerical Analysis of Impacts of Pressurized Pipes Onto Surrounding Structures Induced by Pipe Whipping
Authors: Combescure D. , Aubert J. , Galon P. , Rousseau J. , Delaval C.
Published: July 2008

In civil and military nuclear industry, the safety analysis requires to identify the damage induced by a pipe whipping. Due to the complexity of the phenomena and the pipe geometry and characteristics, the analyses are based on simplifying assumptions. For example, the pipe rupture which is assumed to occur at several predetermined positions along the pipe is usually considered as quasi-instantaneous and complete (double-ended guillotine break). The loading induced by the fluid in the pipe is also represented by an axial force at the pipe extremity. The analysis aims at determining the most vulnerable structures and equipment in the vicinity of the pipe. For this purpose, complete dynamic analyses can be performed but the complexity of the phenomena may require a too large modeling effort: important calculation time due to the geometric, material and contact non linearities, number of cases to be studied, large amount of numerical results to be analyzed... Non linear modeling may also be insufficient to verify the state of the impacted structures since empirical formulae are often preferred for perforation analysis because of their validity verified on experimental campaigns. The present paper focuses on a particular point and shows an analysis of numerical modeling of a pipe elbow impacting a metallic plate using the EUROPLEXUS fast transient dynamic software. Local and global results have been extensively analyzed in order to construct simplified models constituted by a limited number of masses and stiffnesses. The identification of the simplified model parameters -specially the masses- is based on the analysis of the local and average velocities, deformation and kinetic energies and impact forces between the impacting tube and the impacted plate. A parametrical study has been performed in order to identify the effect of the initial velocity of the projectile and the dimensions of the impacted plate (thickness and length). It has been confirmed the ratio between the pipe and plate thicknesses may be a good indicator to determine which structure may concentrate the main part of plasticity and so damage. Another dimensionless number proposed in the literature gives also reliable information to determine the pipe limit velocity corresponding to the onset of material plasticity in one of the structures.
Analysis and Assessment of Stress in Two Typical Drawing Tube Headers
Authors: Gao Zengliang , Chen Jie , Cai Gangsi , Ren Xin , Li Qing
Published: July 2008

Finite element analysis and stress measurement are carried out for two typical drawing tube headers, which is a new kind of tube header without fillet weld. The material of the drawing tubes and header is SA335-P91. Two cases, normal operating condition (case 1) and cold start up condition (case 2), are analyzed. The maximum stresses are located in the inner corner of the drawing tube for one row of tube header, while the maximum stresses for both cases are located in the inner corner of the cover plate for two row of tube header. The stresses at the drawing tube for both cases meet ASME requirement for stress for both drawing tube headers. Fatigue life of the two row of drawing tube header is more than 106 cycles.
Design of Hyper Compressor Packing Cup Rings for Optimum Fatigue Life
Authors: Perez E. H. , Diab S. , Dixon R. D.
Published: July 2008

Fatigue analyses of the inner and outer rings of hyper compressor retainers were performed to determine the optimum interference fit and interference fit diameter to maximize the fatigue life of both the inner and outer rings when subjected to cyclic operating internal pressures. The relationships between the optimum interference fit diameter, the amount of interference and cyclic pressures are derived using the fatigue analysis methodology of the ASME Code, Section VIII, Division 3. The effect of axial preload is evaluated, and the results are checked using the finite element method.
Thermal Mixing Points: A Comparison Using CFD
Authors: Seipp Trevor G.
Published: July 2008

In a previous paper, the author presented a procedure for evaluating piping thermal mixing points using finite element analysis. However, several assumptions had to be made with respect to the thermal boundary conditions. While, at the time, those were thought to be conservative assumptions, there was no comparison with alternate methods of determining the thermal boundary conditions. With recent advances in computational fluid dynamics (CFD), particularly the availability of high-quality commercial code, such a comparison can now be made. In this paper, the author reviews the piping thermal mixing point cases evaluated in the previous paper using CFD as the comparative analysis tool. The temperature fields in the piping thermal mixing points are compared. The calculated stress fields are also examined to determine if the original thermal boundary conditions were reasonable.
Robustness of Residual Stress Computation: From SATOH Test to Welding Plate
Authors: El Ahmar Walid , Jullien Jean-Franc¸ois , Gilles Philippe
Published: July 2008

In order to evaluate the robustness of numerical welding simulation, sensitivity analyses on mechanical models and parameters have been conducted for given thermal fields. The study is based on two simple TIG welding experiments. The material is a 316L stainless steel where no phase transformation is present. Special attention was paid to the mechanical behavior of the Heat Affected Zone (HAZ). Both experiments are performed on a simple geometry of reduced dimensions. The first one is the uniaxial SATOH test on a beam clamped between two rigid bodies. The specimen is homogeneous heated and cooled under restrained condition in order to reproduce thermo-mechanical phenomena that take place in the HAZ of a structure during welding. The second one is a two-pass TIG weld deposit on a plate. On this mock-up (identified as 24–25, [8]), quite a few experimental measurements were performed in order to compare with numerical results of different models. At the first step, we research a reference solution which gives the best agreement with the thermal and mechanical experimental results. The second step consists in determining through numerical simulations which mechanical parameters have the largest influence on residual stresses induced by the welding process. This paper presents the numerical analysis of the two experiments weld reference. Experimental verifications were made at each stage of the calculation, in order to validate the numerical model. In a further step, sensitivity computations have been conducted to examine the most influential parameters on the computed results.
Closed-Form Plastic Collapse Loads of Pipe Bends Under Combined Pressure and In-Plane Bending
Authors: Oh Chang-Sik , Kim Yun-Jae
Published: July 2008

Based on three-dimensional (3-D) FE limit analyses, this paper provides plastic limit, collapse and instability load solutions for pipe bends under combined pressure and in-plane bending. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly plastic materials using the small geometry change option, and the FE limit analyses using the large geometry change option provide plastic collapse loads (using the twice-elastic-slope method) and instability loads. For the bending mode, both closing bending and opening bending are considered, and a wide range of parameters related to the bend geometry is considered. Based on the FE results, closed-form approximations of plastic limit and collapse load solutions for pipe bends under combined pressure and bending are proposed.
Risk-Based Fracture Evaluation of Reactor Vessels Subjected to Cool-Down Transients Associated With Shutdown: An Examination of the Effects of Different Modeling Approaches on Estimated Failure Probabilities
Authors: Dickson T. L. , EricksonKirk M. T.
Published: July 2008

The current regulations, as set forth by the United States Nuclear Regulatory Commission (USNRC), to insure that light-water nuclear reactor pressure vessels (RPVs) maintain their structural integrity when subjected to planned startup (heat-up) and shutdown (cool-down) transients are specified in Appendix G to 10 CFR Part 50, which incorporates by reference Appendix G to Section XI of the ASME Code. In 1999, the USNRC initiated the interdisciplinary Pressurized Thermal Shock (PTS) Re-evaluation Project to determine if a technical basis could be established to support a relaxation in the current PTS regulations. The PTS re-evaluation project included the development and application of an updated risk-based computational methodology that incorporates several advancements applicable to modeling the physics of vessel fracture due to thermal hydraulic transients imposed on the RPV inner surface. The results of the PTS re-evaluation project demonstrated that there is a sound technical basis to support a relaxation of the current PTS regulations. The results of the PTS re-evaluation are currently under review by the USNRC. Based on the promising results of the PTS re-evaluation, the USNRC has recently applied the updated computational methodology to fracture evaluations of RPVs subjected to planned cool-down transients, associated with reactor shutdown, derived in accordance with ASME Section XI – Appendix G. The objective of these analyses is to determine if a sound technical basis can be established to provide a relaxation to the current regulations for the derivation of bounding cool-down transients as specified in Appendix G to Section XI of the ASME Code. This paper provides a brief overview of these analyses, results, and the implications of the results.
Performance of High-Pressure Fibre-Reinforced Polymer Composite Pipe Structures
Authors: Mertiny Pierre , Ellyin Fernand
Published: July 2008

Advanced fiber-reinforced polymer composite pipes offer high strength and superior corrosion resistance properties compared to conventional metallic pipeline materials. However, damage mechanisms in composite pipes are not fully understood and failure prediction methodologies are currently inadequate. Research is required to resolve these deficiencies which are an encumbrance to the certification of high-pressure composite pipe and its introduction into service. This is underlined by the findings reviewed in the present paper which derive from a comprehensive study on the performance and damage mechanisms in composite pipes and joint modules.
The Concept of Retained Strength as Applied to Thermal Shocks
Authors: Emery A. F.
Published: July 2008

Retained Strength has been used to characterize the damage incurred by brittle materials when exposed to a thermal shock or to a sequence of thermal shocks. While it is a valid measure to qualitatively rank materials in a simplistic way, it cannot be used in any quantitative sense since it depends upon the specific thermal shock conditions and upon the type of test used to measure it. Given the current state of knowledge about fracture of brittle materials, retained strength should be considered as an artifact of a time when little was understood about fracture of brittle materials. When the residual strength of a ceramic is measured by mechanical tests subsequent to the exposure of a ceramic to a thermal shock, the isothermal test condtions must produce a stress field that is consistent with the stresses produced by the thermal shock. This paper describes the theoretical basis for retained strength and presents experimental data to show that retained strength measured from the isothermal tests cannot be used in general as an accurate measure of the thermal damage.
Long Range Ultrasonic Guided Wave Focusing in Pipe for Small Defect Detection, Location and Circumferential Length Analysis
Authors: Mu Jing , Zhang Li , Rose Joseph L. , Spanner Jack
Published: July 2008

Ultrasonic guided wave focusing techniques in steel pipe are used to detect and measure the axial as well as circumferential locations of three differently shaped defects (planar saw cuts, a volumetric through-wall hole, and a volumetric elliptical corrosion). The axial location of a defect was obtained by measuring the arrival time of the defect echo. Defect circumferential location was determined by focusing at 44 circumferential positions around the pipe at a specific distance. The maximum amplitude of the defect echo was recorded with respect to each circumferential focal position in producing an angular profile of the reflected wave. The maximum amplitude of this experimental angular profile occurs at the angle of the defect circumferential location. The energy impingement onto the defect for each focusing position can be calculated from the focused angular profile and the defect cross sectional area. Comparison between the experimental angular profiles and the theoretical ones provides us with a good estimate of the defect circumferential size.
Long Range Guided Wave Natural Focusing Pipe Inspection
Authors: Zhang Li , Rose Joseph L. , Mu Jing , Owens Steven E.
Published: July 2008

Long range ultrasonic guided wave nondestructive evaluation can be used to inspect pipelines over fairly long distances. Partial loading of transducers around the circumference leads to a non-axisymmetric energy distribution. At particular axial distances and frequencies, the ultrasonic energy is naturally focused at some spots around the circumference via constructive wave interference. This so called “natural focusing” phenomenon can be used to improve guided wave sensitivity for a defect since more energy is sent to the defect. However, defects located in other places could possibly be missed, unless we can move the natural focusing points throughout the pipe. We have done this by frequency and circumferential angle tuning for specific circumferential loading lengths. In order to utilize the natural focusing phenomenon to enhance detection sensitivity, a frequency and angle tuning (FAT) technique is employed to extend the area that is scanned by focal energy. It is observed that the natural focal points at a fixed axial distance move with frequency variation and circumferential excitation length change. In this paper, the natural focusing phenomenon with FAT is theoretically calculated and experimentally investigated. The results show that the natural focusing inspection technique can sufficiently inspect an entire pipe with FAT. Some sample inspection data is compared by applying axisymmetric excitations, FAT, and phased array focusing.
Stress Intensity Factor Estimation for Embedded and Surface Cracks in an RPV Subjected to Yielding of Cladding
Authors: Shibata Katsuyuki , Onizawa Kunio , Tanaka Kazuhisa , Suzuki Masahide
Published: July 2008

The cladding of an RPV (Reactor Pressure Vessel) at the inner surface may be subjected to a plastic yielding due to a high thermal stress under some severe overcooling events, while the stress in base metal remains elastic. The stress intensity factor estimation at the deepest crack tip of an embedded crack (EC) or a surface crack (SC) under such loadings is essential in the integrity assessment of an RPV. However, an elasto-plastic FE analysis is required to obtain the stress intensity factor on this problem generally. A solution for an under-clad crack (UCC) was developed by EDF based on numerous 2D FE computations. This paper proposes a simplified estimation scheme which takes the yielding of cladding into account. This scheme estimates the stress intensity factor at the deepest crack tip of an embedded crack or a surface crack. It is assumed that the stress singularity does not exist at the shallowest crack tip in the cladding. To estimate the stress intensity factor of an embedded crack, the crack shape is replaced by a semi-elliptical one to utilize existing solutions of SC. Case studies to examine the proposed estimation scheme were carried out for an UCC and SC subjected to the SBLOCA, SLB and PTS transients, which were defined by a international round robin PROSIR (Probabilistic Structural Integrity of a PWR Reactor Pressure Vessel) project being conducted by OECD/NEA/IAGE-WG. It was found that the proposed scheme gives a reasonable estimation of the stress intensity factor for an UCC and a SC.
Numerical Simulation of Vortex Shedding in Normal Triangular Tube Arrays
Authors: Selent Bjo¨rn , Meskell Craig
Published: July 2008

The unsteady flow through normal triangular tube arrays is simulated applying the Cloud-in-Element method. The scheme realizes time-stepping via a Langrangian vortex method using random-walk to model diffusion in the flow. The vortex particle velocities are computed on a fixed unstructured grid at each time step. Zero normal velocity on solid boundaries is enforced by a source panel method and zero slip is achieved by introducing vorticity into the flow at each time step. Simulations have been carried out for normal triangular tube arryas with pitch ratios of 1.32, 1.61, 2.08, 2.63 at Reynolds numbers of 1000, 3000, 5000 and 10000. Single vortex shedding frequencies have been observed for the smaller pitch ratios while two Strouhal numbers are obtained for the sparse arrays. This is consistent with experimental data in the literature. Also the overall flow structures were captured successfully.
Fluid-Dynamic Loading on a Tilted Rectangular Cylinder Near a Solid Wall
Authors: Malavasi Stefano , Zappa Emanuele
Published: July 2008

We investigate the impact of different boundary conditions on the flow field developing around a tilted rectangular cylinder. We are mainly interested in analyzing the changes in force coefficients and in the vortex shedding Strouhal number due to the proximity of the cylinder to a bottom plate (placed at various distances from the cylinder) at different angles of attack. The angle of attack ranges between −30° and +30° and the cylinder elevation above the bottom wall is varied between almost zero and 200 mm. The effects of the different boundary conditions on the vortex shedding phenomenon are investigated by considering the Strouhal number of the vortex shedding as the key controlling parameter. The experimental results mimicking the unbounded conditions (relative large elevation of the cylinder above the solid wall) are in close agreement with those already found in literature. On the contrary, remarkable differences occur when the elevation of the cylinder is decreased. A large body of experimental results is related to the small elevation conditions at different attack angles, where the presence of the wall has a non-negligible effect on the behavior of the force coefficients and Strouhal number of the vortex shedding.
The Effect of Temperature Dependent Yield Strength on Upper Bounds for Creep Ratcheting
Authors: McGreevy Timothy E. , Leckie Frederick A. , Carter Peter , Marriott Douglas L.
Published: July 2008

The Bree model and the elastic core concept have been used as the foundation for the simplified inelastic design analysis methods in the ASME Code for the design of components at elevated temperature for nearly three decades. The methodology provides upper bounds for creep strain accumulation and a physical basis for ascertaining if a structure under primary and secondary loading will behave elastically, plastically, shakedown, or ratchet. Comparisons of the method with inelastic analysis results have demonstrated its conservatism in stainless steel at temperatures representative of those in LMBR applications. The upper bounds on creep accumulation are revisited for very high temperatures representative of VHTR applications, where the yield strength of the material is strongly dependent upon temperature. The effect of the variation in yield strength on the evolution of the core stress is illustrated, and is shown to extend the shakedown regions, and affects the location of the boundaries between shakedown, ratcheting, and plasticity.
Load Factor Based Calculation for Gasketed Flange Connection With Cover Plate Subjected to Internal Pressure
Authors: Nagata Satoshi , Sawa Toshiyuki
Published: July 2008

This paper deals with the behavior of a gasketed flange connection with a cover plate subjected to internal pressure. A calculation method to obtain the bolt force and the gasket reaction changes due to internal pressure using a load factor is introduced and the equations to obtain the load factor for the gasketed flange connection with cover plate using a simplified model are shown. By using 3 inch flange connection with cover plate a spiral gasket inserted, an experimental test is carried out and bolt force changes are measured due to internal pressure. The changes of the bolt force and the gasket reaction due to internal pressure are estimated by the load factor based calculation. Finite element analysis is also performed. The calculation results and the experimental ones are compared one another. It is demonstrated that the calculated bolt force change shows fairly good agreement with the experimental test results. This shows the proposed method may be applicable for the design calculation considering the sealing performance of the connection. When the required gasket stress is given to achieve the target tightness in the operating condition, the appropriate initial bolt preload can be determined by using the proposed method.
Fatigue Strength Analysis of Tube-to-Tubesheet Joint
Authors: Su Wenxian , Sang Zhifu , Ye Li , Huang Weimin , Tong Zhengming
Published: July 2008

The joint of tube-to-tubesheet of heat exchanger is the key of the process of fabricating heat exchanger. The joint mode of the tube-to-tubesheet is composed by expanded joint, welded joint and expanded together with welded. The application range and requirement of welded mode is stipulated in Chinese Standard—GB151-1999 tube-shell heat exchanger, it as follows: the design pressure is not great 35MPa, and design diameter is not great 2600 mm. And it is not applied in the fields where there is great vibration and clearance erosion.
Plastic Limit Pressure of Pressurized Cylinders With Hillside Nozzle
Authors: Wang H. F. , Sang Z. F. , Xue L. P. , Widera G. E. O.
Published: July 2008

Cylinder-nozzle intersections are widely used in pressure vessel and piping industries. In order to get better mixing and energy exchange of the reactants, pipe-nozzle intersection with hillside nozzle is applied more and more widely. The purpose of this work is to investigate the plastic limit load of cylinders with hillside nozzle subjected to internal pressure. Three full-scale test models with different angles of the hillside nozzle were designed and fabricated specially for the test using strain gagues. 3-D finite element numerical simulations on the experimental models were performed. Based on both results, a group of basic data on plastic limit pressure defined by double elastic-slope method for cylinders with hillside nozzle is approximately obtained according to load-strain responses, and the plastic limit pressures determined by test and finite element analysis are in good agreement. The results indicate that the limit pressure increases with the increment of the angle of the hillside nozzle, and compared with radial nozzles in cylinders, the hillside nozzles have higher limit pressure, which can be served as the basis for developing a design guideline for pressurized cylinders with various angles of hillside nozzle.
Characterization of the New Metallo-β-Lactamase VIM-13 and Its Integron-Borne Gene from a
Pseudomonas aeruginosa
Clinical Isolate in Spain
Authors: Juan Carlos , Beceiro Alejandro , Gutiérrez Olivia , Albertí Sebastián , Garau Margalida , Pérez José L. , Bou Germán , Oliver Antonio
Published: July 2008

During a survey conducted to evaluate the incidence of class B carbapenemase (metallo-β-lactamase [MBL])-producing
Pseudomonas aeruginosa
strains from hospitals in Majorca, Spain, five clinical isolates showed a positive Etest MBL screening test result. In one of them, strain PA-SL2, the presence of a new
bla
VIM
derivative (
bla
VIM-13
) was detected by PCR amplification with
bla
VIM-1
-specific primers followed by sequencing. The
bla
VIM-13
-producing isolate showed resistance to all β-lactams (except aztreonam), gentamicin, tobramycin, and ciprofloxacin. VIM-13 exhibited 93% and 88% amino acid sequence identities with VIM-1 and VIM-2, respectively.
bla
VIM-13
was cloned in parallel with
bla
VIM-1
, and the resistance profile conferred was analyzed both in
Escherichia coli
and in
P. aeruginosa
backgrounds. Compared to VIM-1, VIM-13 conferred slightly higher levels of resistance to piperacillin and lower levels of resistance to ceftazidime and cefepime. VIM-13 and VIM-1 were purified in parallel as well, and their kinetic parameters were compared. The
k
cat
/
K

m

ratios for the antibiotics mentioned above were in good agreement with the MIC data. Furthermore, EDTA inhibited the activity of VIM-13 approximately 25 times less than it inhibited the activity of VIM-1. VIM-13 was harbored in a class 1 integron, along with a new variant (Ala108Thr) of the aminoglycoside-modifying enzyme encoding gene
aacA4
, which confers resistance to gentamicin and tobramycin. Finally, the VIM-13 integron was apparently located in the chromosome, since transformation and conjugation experiments consistently yielded negative results and the
bla
VIM-13
probe hybridized only with the genomic DNA.
Impact of the Interaction of R207910 with Rifampin on the Treatment of Tuberculosis Studied in the Mouse Model
Authors: Lounis Nacer , Gevers Tom , Van Den Berg Joke , Andries Koen
Published: July 2008

New drugs are needed to shorten the duration of tuberculosis treatment. R207910, a diarylquinoline, is very active against
Mycobacterium tuberculosis
both in vitro and in mice. In healthy volunteers, the coadministration of R207910 and rifampin induced the increased metabolism of R207910, resulting in a 50% reduction in the level of R207910 exposure. We assessed the impact of reducing the dose of R207910 on its efficacy when R207910 was combined with a background regimen of isoniazid, rifampin, and pyrazinamide. Addition of 25 mg/kg of body weight or 12.5 mg/kg R207910 to the background regimen resulted in faster bacterial clearance and culture negativity. The difference in efficacy between the two doses was not statistically significant. The minimal bactericidal dose of R207910 when it was tested as part of the combination was identical to that when it was tested as monotherapy. Because of the drug-drug interaction in humans, the activity of R207910 in humans could be less than that expected from studies with mice. Our data from the mouse model demonstrate that R207910 has significant activity, even when its exposure is reduced by 50% and when it is added to a strong background regimen of isoniazid, rifampin, and pyrazinamide. In killing kinetic studies, the bactericidal effect of R207910 in mice was modest during the first week of treatment, but it increased in the following 3 weeks, while the bactericidal activity of isoniazid was limited to the first week of treatment.
Detection of Macrolide Resistance inMycoplasma pneumoniaeby Real-Time PCR and High-Resolution Melt Analysis
Authors: Wolff Bernard J. , Thacker W. Lanier , Schwartz Stephanie B. , Winchell Jonas M.
Published: July 2008

Mycoplasma pneumoniaeis a significant cause of community-acquired pneumonia, which is often empirically treated with macrolides or azalides such as erythromycin or azithromycin. Recent studies have discovered the existence of macrolide-resistant strains within the population that have been mapped to mutations within the domain V region of the 23S rRNA gene. Currently, identification of these resistant strains relies on time-consuming and labor-intensive procedures such as restriction fragment length polymorphism, MIC studies, and sequence analysis. The current study reports two distinct real-time PCR assays that can detect the A2063G or A2064G base mutation (A2058G or A2059G byEscherichia colinumbering) conferring macrolide resistance. By subjecting the amplicon of the targeted domain V region of the 23S rRNA gene to a high-resolution melt curve analysis, macrolide-resistant strains can quickly be separated from susceptible strains. Utilizing this method, we screened 100 clinical isolates and found 5 strains to possess mutations conferring resistance. These findings were concordant with both sequencing and MIC data. This procedure was also used successfully to identify both susceptible and resistant genotypes in 23 patient specimens. These patient specimens tested positive for the presence ofM. pneumoniaeby a separate real-time PCR assay, although the bacteria could not be isolated by culture. This is the first report of a real-time PCR assay capable of detecting the dominant mutations that confer macrolide resistance onM. pneumoniae, and these assays may have utility in detecting resistant strains of other infectious agents. These assays may also allow for clinicians to select appropriate treatment options more rapidly and may provide a convenient method to conduct surveillance for genetic mutations conferring antibiotic resistance.
Characterization of an ABCG-Like Transporter from the Protozoan Parasite
Leishmania
with a Role in Drug Resistance and Transbilayer Lipid Movement
Authors: Castanys-Muñoz Esther , Pérez-Victoria José María , Gamarro Francisco , Castanys Santiago
Published: July 2008

Leishmaniasis treatment is hampered by the increased appearance of treatment failure. ATP-binding cassette (ABC) transporters are usually involved in drug resistance both in tumor cells and in microorganisms. Here we report the characterization of an ABCG-like transporter, LiABCG6, localized mainly at the plasma membrane in
Leishmania
protozoan parasites. When overexpressed, this half-transporter confers significant resistance to the leishmanicidal agents miltefosine and sitamaquine. This resistance phenotype is mediated by a reduction in intracellular drug accumulation. LiABCG6 also reduces the accumulation of short-chain fluorescent phospholipid analogues of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. As a whole, these results suggest that LiABCG6 could be implicated in phospholipid trafficking and drug resistance.
Effects of Antibiotics on Quorum Sensing in
Pseudomonas aeruginosa
Authors: Skindersoe Mette E. , Alhede Morten , Phipps Richard , Yang Liang , Jensen Peter O. , Rasmussen Thomas B. , Bjarnsholt Thomas , Tolker-Nielsen Tim , Høiby Niels , Givskov Michael
Published: July 2008

During infection,
Pseudomonas aeruginosa
employs bacterial communication (quorum sensing [QS]) to coordinate the expression of tissue-damaging factors. QS-controlled gene expression plays a pivotal role in the virulence of
P. aeruginosa
, and QS-deficient mutants cause less severe infections in animal infection models. Treatment of cystic fibrosis (CF) patients chronically infected with
P. aeruginosa
with the macrolide antibiotic azithromycin (AZM) has been demonstrated to improve the clinical outcome. Several studies indicate that AZM may accomplish its beneficial action in CF patients by impeding QS, thereby reducing the pathogenicity of
P. aeruginosa.
This led us to investigate whether QS inhibition is a common feature of antibiotics. We present the results of a screening of 12 antibiotics for their QS-inhibitory activities using a previously described QS inhibitor selector 1 strain. Three of the antibiotics tested, AZM, ceftazidime (CFT), and ciprofloxacin (CPR), were very active in the assay and were further examined for their effects on QS-regulated virulence factor production in
P. aeruginosa
. The effects of the three antibiotics administered at subinhibitory concentrations were investigated by use of DNA microarrays. Consistent results from the virulence factor assays, reverse transcription-PCR, and the DNA microarrays support the finding that AZM, CFT, and CPR decrease the expression of a range of QS-regulated virulence factors. The data suggest that the underlying mechanism may be mediated by changes in membrane permeability, thereby influencing the flux of
N
-3-oxo-dodecanoyl-
l
-homoserine lactone.
Edelfosine Induces an Apoptotic Process in
Leishmania infantum
That Is Regulated by the Ectopic Expression of Bcl-X
L
and Hrk
Authors: Alzate Juan Fernando , Arias Andrés , Mollinedo Faustino , Rico Eva , de la Iglesia-Vicente Janis , Jiménez-Ruiz Antonio
Published: July 2008

The alkyl-lysophospholipids edelfosine and miltefosine induce apoptosis in
Leishmania infantum
promastigotes. The finding that edelfosine-induced cell death can be regulated by the ectopic expression of the antiapoptotic and proapoptotic members of the Bcl-2 family of proteins Bcl-X
L
and Hrk suggests that this process is similar to apoptosis in eukaryotic cells.
β-1,2 Oligomannose Adhesin Epitopes Are Widely Distributed over the Different Families of
Candida albicans
Cell Wall Mannoproteins and Are Associated through both N- and O-Glycosylation Processes
Authors: Fradin Chantal , Slomianny Marie Christine , Mille Céline , Masset Annick , Robert Raymond , Sendid Boualem , Ernst Joachim F. , Michalski Jean Claude , Poulain Daniel
Published: July 2008

β-1,2-Linked mannosides (β-Mans) are believed to contribute to
Candida albicans
virulence. The presence of β-Mans has been chemically established for two molecules (phosphopeptidomannan [PPM] and phospholipomannan) that are noncovalently linked to the cell wall, where they correspond to specific epitopes. However, a large number of cell wall mannoproteins (CWMPs) also express β-Man epitopes, although their nature and mode of β-mannosylation are unknown. We therefore used Western blotting to map β-Man epitopes for the different families of mannoproteins gradually released from the cell wall according to their mode of anchorage (soluble, released by dithiothreitol, β-1,3 glucan linked, and β-1,6 glucan linked). Reduction of β-Man epitope expression occurred after chemical and enzymatic deglycosylation of the different cell wall fractions, as well as in a secreted form of Hwp1, a representative of the CWMPs linked by glycosylphosphatidylinositol remnants. Enzyme-linked immunosorbent assay inhibition tests were performed to assess the presence of β-Man epitopes in released oligomannosides. A comparison of the results obtained with CWMPs to the results obtained with PPM and the use of mutants with mutations affecting O and N glycosylation demonstrated that both O glycosylation and N glycosylation participate in the association of β-Mans with the protein moieties of CWMPs. This process, which can alter the function of cell wall molecules and their recognition by the host, is therefore more important and more complex than originally thought, since it differs from the model established previously with PPM.
Load Tests Results on Friction Piles in Sand
Authors: Tavenas François A.
Published: July 2008

As part of the design of an important pile foundation, an extensive testing program has been carried out in order to determine the type and the necessary characteristics of the pile best suited to the site and the structure to be designed. Three types of piles have been tested, i.e. timber piles, a steel H-pile, and a Herkules precast concrete pile. The Herkules and H-piles were equipped with deformation gauges and driven in 10-ft (3-m) increments to a total length of 70 ft (21 m), a loading test being carried out at the end of each increment. Thus, it was possible to determine the variations of the bearing capacity, the point–resistance, and the skin-friction as functions of the embedded pile length.The aim of this paper is to present the technique used and the results obtained.
Use of Ice Covers for Transportation
Authors: Gold L. W.
Published: July 2008

Observations are reported on the failure and use of freshwater ice covers for vehicular traffic. The study showed that good quality ice covers can support loads of up to P = 250 h2, where P is the total load in pounds and h is the thickness of the ice in inches. Failures were reported, however, for loadings as low as P = 50 h2. Factors contributing to the failure of covers for loading less than P = 250 h2 were: vehicle speed, thermal stress due to drop in temperature, and fatigue and quality of the cover. The results are discussed with reference to Westergaard's equations for the maximum stress due to circular loads on an elastic plate resting on an elastic foundation. Information is presented on the elastic and strength properties of ice covers required for theoretical calculations. Experience in the construction and use of ice roads and parking areas is described.
Construction on Permafrost
Authors: Crawford C. B. , Johnston G. H.
Published: July 2008

Permafrost, or perennially frozen ground, occurs widely throughout the northern half of Canada. Experience has shown that special design and construction techniques are required for building on permafrost in order to avoid disturbing the delicate thermal balance that preserves the frozen ground. The state of knowledge is reviewed with respect to site investigations, foundation designs, water supply and sewage disposal, the construction of transportation facilities, and the influence of surface flooding, drainage and other disturbances on the ground thermal regime. Attention is drawn to an extensive literature and research needs are outlined.
Heave and Heaving Pressures in Frozen Soils
Authors: Yong R. N. , Osler J. C.
Published: July 2008

Most previous studies of frost heave and associated frost heaving pressures have been concerned with the process of ice lensing and ice segregation, and the primary mechanism used to explain the related phenomena of heave and pressure is seen to be consistent with the process of formation of ice lenses. Thus, while certain investigators may disagree on various details, there appears to be general agreement on the mechanisms which form the basis for the so-called capillary model for the prediction of frost heaving and associated pressures. In addition, various criteria used for the assessment of frost susceptibility rely implicitly on the admissibility of this model as their rationale.This study questions the advisability of using a singular capillary model, in view of the wide range of conditions and constraints prevailing at any one time. Since soil freezing involves moisture movement and associated resultant volumetric expansion at both the macroscopic and microscopic scale arising from temperature and osmotic gradients, it is clear that a comprehensive theory to rationally explain heave and (or) heaving pressures is needed to account for all major factors which influence the total response of the frozen soil system. In this respect, the results of a critical examination of recent field and laboratory tests performed at McGill University and elsewhere are used to show that the available theories may be too restricted in scope to explain all facets of the observed behavior of frozen natural soils. To overcome the shortcomings noted above, an extended generative mechanism is developed and procedures for the examination of actual results are presented.
A Regional Study of Landsliding Near Ottawa
Authors: Sangrey D. A. , Paul M. J.
Published: July 2008

The stability of natural slopes near Ottawa has been examined from a regional approach. With the aid of aerial photographs, the density and distribution of past landslides have been ascertained, and the development of more recent slides has been traced. This information, combined with details of the present day topography, groundwater conditions, and soil characteristics, leads to a conclusion that factors influencing slope stability vary markedly throughout the region, and certain areas are much more prone to sliding than others.The strength of soils in the region is discussed, including the development of a logical shear strength relationship which incorporates the effects both of cementation strength and fissuring. The influence of sample size on the extrapolation of laboratory triaxial test results to the field situation is introduced. Details of the method of landslide analysis used are given.Considerable evidence is presented to support the presence of separate marine and freshwater clay layers in the Ottawa area, and to suggest that flow slides are confined to the upper freshwater deposit. These two clay soils are most graphically distinguished by differences in fissure spacing and pore water chemistry.
The Saint-Jean-Vianney Landslide: Observations and Eyewitnesses Accounts
Authors: Tavenas F. , Chagnon J.-Y. , Rochelle P. La
Published: July 2008

A major landslide occurred in Champlain Clay at Saint-Jean-Vianney, Quebec, on May 4, 1971. Preliminary investigations reveal that the slide commenced about 10.15 p.m., hit the east section of the town about 10.55 p.m., and within 5 min carried 40 homes to destruction and 31 persons to their deaths. An estimated 9 × 106 cubic yards (6.9 × 108 m3) of material moved during the slide, from an area of approximately 350 000 square yards (~268 000 m2). The slide commenced within the crater of a much larger landslide that occurred about 500 years ago, and after complete liquefaction travelled down the Rivière aux Vases at a speed of approximately 16 miles/h (~26 km/h), carrying debris out into the middle of the Saguenay River.A detailed geotechnical study of the landslide region is currently under way.
Damping in Dynamic Structure–Foundation Interaction
Authors: Rainer J. H.
Published: July 2008

Two methods of calculating the damping ratio for structures on compliant foundations are presented. One method employs the calculation of the system damping ratio from the dynamic amplification factor, the other the modal damping ratio from energy considerations. The numerical results for both methods are compared and interpreted. Three sources of damping are considered: inter-storey damping, radiation damping, and foundation material damping. The numerical results demonstrate that with the introduction of compliant foundations the damping ratio of the system can be larger or smaller than that of the corresponding fixed-base structure. Material damping in the foundation soil has been shown to contribute significantly to the over-all damping ratio.
The Presence and Influence of Fissures in the Boulder Clays of West Central Scotland
Authors: McGown Alan , Radwan Amr M.
Published: July 2008

The recent urban and rural developments in west central Scotland have involved the execution of much more widespread, and often deeper, excavations than previously undertaken in the boulder clays of the area. A number of failures in deep trenches and slope excavations have occurred, whose character appeared to be influenced by the presence of macrofabric features. A detailed field study has confirmed the presence of fissures and showed that they exhibit definite preferred orientation patterns. The influence of these fissure patterns on undrained shear strength and consolidation properties have been assessed using test specimens ranging from 76 to 254 mm diameter and correlations between observed laboratory anisotropic behavior and behavior in excavations have been suggested.
Some Aspects of a Simple Secondary Creep Model for Deformations in Permafrost Slopes
Authors: McRoberts Edward C.
Published: July 2008

This study presents the solution to a simple model for deformations due to secondary creep in permafrost slopes. By introducing a constitutive relationship, or flow law, for ice into the model it is shown that significant creep deformations can occur in frozen slopes. Evidence is reviewed that suggests that secondary creep in ice-rich soils may be faster than that of ice alone.
Urban Fringe Development and Slope Instability in Southern Saskatchewan
Authors: Sauer E. Karl
Published: July 2008

The development of the areas surrounding urban centers in Saskatchewan has become of increasing concern because of slope instability problems. Proglacial meltwater channels and spillways provide seemingly attractive sites for rural estates. An investigation revealed that most of the slopes along these channels are unstable where Regina lacustrine clay or Bearpaw shale are exposed. A large building constructed near Lumsden is experiencing severe damage because it was constructed on landslide debris. South of Saskatoon, a similar problem exists along the east bank of the Saskatchewan River where a high water table is present in a deltaic sand overlying a soft lacustrine clay. An old barn at the Riverside Golf Course is spectacular evidence of the history of the movement of a large slide block in this terrain.Certain problems exist in convincing the public that a stability problem exists in these areas. Some form of landuse zoning based on risk of failure is needed. However, local municipal governments do not have the resources to conduct the necessary research to establish effective controls.
Field Observations of Thawing in Soils
Authors: McRoberts Edward C
Published: July 2008

Case histories are considered which indicate that under some field conditions a thaw interface proceeds as predicted by a simple model. Some reasons for possible deviations are investigated and comparisons are made between calculated and measured rates of thaw.
Stability of Slopes in Anisotropic, Nonhomogeneous Soils
Authors: Chen W. F. , Snitbhan N. , Fang H. Y.
Published: July 2008

The upper bound technique of limit analysis has been found to be very successful in analyzing the stability of cuttings in normally consolidated clays. However, most soils in their natural states exhibit some anisotropy with respect to shear strength, and some nonhomogeneity with respect to depth. It is difficult to obtain the solution based on the classical limit equilibrium analysis with the assumed noncircular failure plane with such soil properties included. This paper establishes an expression for the stability factor Ns, based on the upper bound technique of limit analysis which yields a close-formed solution for sections in which the following conditions are considered: (a) log-spiral failure-plane, through and below toe; (b) non-homogeneity; (c) anisotropy; and (d) general slope.
Parameters for the Design of Tailings Dams
Authors: Mittal Hari K. , Morgenstern Norbert R.
Published: July 2008

Tailings dams differ from conventional earthfill structures in that much more time is available to optimize design since their construction is extended over a longer period. Laboratory data are presented on a variety of tailings sands which indicate that they are relatively strong and incompressible. Poor performance is likely to result from inadequate seepage control and instability due to liquefaction. In order to take advantage of opportunities for ongoing design, in situ permeability and density monitoring is needed together with pore pressure measurements. An infiltration test for the determination of permeability above the water table is proposed. In situ density determinations are made by driving a nuclear probe into the sands. The latter technique offers considerable promise for evaluating liquefaction potential of natural and fill deposits. Field experience is used to illustrate the application of the techniques.