bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of Stack Vortex Induced Vibrations
Authors: McGuffie Sean M. , Porter Michael A.
Published: January 2014

A stack installation experienced vortex-induced vibrations (VIV) while in-service. The magnitude of the vibrations was severe enough that cracking in the welds at the stack bases was experienced shortly after their installation. Initially, straight strakes were placed on the stacks, based on field serviceability, per API 560. The strakes proved ineffective and it was determined that the stacks would be uninstalled for repair. During the repair process, design steps were required to reduce or eliminate the VIV experienced in-service. Due to a flaw in the initial design and the ineffectiveness of the straight strake solution, the end client required verification of any proposed design changes before their implementation. Additionally, little time was allotted for the investigation of solutions.

Tuned mass dampers were initially explored for the design modification. It was determined that they could not be constructed of materials suitable for the environmental operational characteristics of the stacks. It was then agreed that aerodynamic modifications of the stacks should be explored to reduce VIV. ASME STS I specifies the design and installation of helical strakes on stacks, but does not indicate the magnitude of vibration reduction that can be expected [3]. Therefore, numerical models were used to determine if the strakes would reduce or eliminate the service vibration.

A baseline analysis was first conducted to validate that the tools — a combination of computational fluid dynamics (CFD) and finite element (FE) methods — could capture the in-service behavior. To perform this analysis a CFD model was constructed of the as-built stack. Using DES methods, this model was analyzed at several wind speeds to determine the magnitude and frequency content of the VIV-forcing functions. This information was then used to perform a dynamic analysis using an FE model of the stack. This model accurately predicted the correct wind speed corresponding to VIV and the amplitude of the stack’s vibration. A second model was then constructed of a stack with helical strakes, using a novel modeling methodology. This model was analyzed over a variety of wind speeds using DES methodologies. The forcing functions predicted with the helical strake model were then used to determine the stack’s in-service response. This paper contains the complete methodologies and results associated with these analyses.
Design Considerations: Torque or Tension — Advantages and Disadvantages
Authors: Noble Robert
Published: January 2014

To seal effectively gasketed bolted flanged joints require the application of bolt load in a controlled manner. There are two main methods of achieving this — application of bolt load by controlled torque and application of bolt load by controlled tension.

The paper considers the practical merits and limitations of each technique under criteria including:

Practicality, accuracy, scatter, bolt load or stress, bolt material, bolt length, tool access limitations, cost of tooling, time, safety and ease of understanding.

The paper does not seek to recommend one technique over the other but rather to give the joint designer, specifier or tool selector a set of guidelines to ensure the most effective and practical technique is chosen for each joint being designed.

Following the recommendations in the paper will allow a designer to recommend a technique that will deliver the best results for the joint based on the principle that long term integrity is more important that short term gain.
An Evaluation of the Protection Against Local Failure in ASME Section VIII, Division 2: Finite Element Model Considerations
Authors: Seipp Trevor G.
Published: January 2014

The local failure criteria was a relatively new inclusion in the 2007 Edition of ASME Section VIII, Division 2. The elastic-plastic evaluation criteria for this failure mechanism was brand new to the Code. This failure mechanism introduced to the Code the concept of local strain limits based on the triaxial state of stress.

In implementing the evaluation of this failure mechanism, an interesting phenomenon was discovered. The triaxiality was to be calculated “everywhere” in the model, and used to create a limiting strain to be compared to the plastic strain at the point where said triaxiality was calculated.

As is well known, in the finite element method, stresses and strains are calculated at the Gauss Points, and extrapolated to the nodes. This uses the element shape function. One question that arises is: if the triaxiality is calculated at the Gauss Points, can it be extrapolated to the nodes using the same element shape functions? Another question that arises is: can the extrapolated values of stress and strain be adequately used to calculate the triaxiality at the nodes?

This paper discusses the validity of both approaches, and introduces a third option: a material property called Ductile Damage Initiation Criteria, and provides and example that demonstrate all three methods. Recommendations are provided about the best approach to be implemented.
Round Robin Prediction of Residual Stresses in the Edge-Welded Beam R6 Validation Benchmark Problem
Authors: Aird Chris , Smith Mike , Kapadia Priyesh , Abburi Venkata Kiranmayi , Muransky Ondrej
Published: January 2014

A simple austenitic steel beam specimen with a single autogenous weld bead laid along its top edge is an ideal training problem for novice weld modellers. This geometry may be analysed using either 3D or 2D FE models and employing either block-dumped or moving heat source techniques, with a variety of material constitutive models. This paper describes a residual stress simulation round robin performed on the validation benchmark problem of this type recently added to the R6 defect assessment procedure. A variety of solution strategies of increasing complexity are applied to the problem and the results compared with accuracy targets specified in the validation benchmark. It is found that the greatest solution accuracy is obtained using a 3D moving heat source, and mixed isotropic-kinematic material hardening behaviour.
Experimental Study of Crack Growth in HDPE PE100 Pipes
Authors: Machado Raul , Gonzalez Marco , Gonzalez Jeanette
Published: January 2014

The operation conditions of a piping system such as impact loads, cyclic loadings and discontinuities cause damages, cracking or weakening in the material. The High Density Polyethylene (HDPE) is amply used in the fabrication of pipes due to its versatility, low cost and lightweight. In this study, an experimental study of fracture mechanics of HDPE PE100 specimens obtained directly from extruded pipes is developed. The research is aimed at characterizing the pipe mechanical behaviour under operation loadings, for which elastic-plastic mechanical tests under the ASTM D-5045, E-1820, E-399 and E-813 standards and ESIS protocol are carried out. The influence of the orientation induced by the extrusion process (circumferential or longitudinal direction) on pipes fracture resistance is established. SENB type specimens (three point bending) are used for the fracture characterization and J-R Curves (J vs. Δa) for elastic-plastic analysis are generated according to ESIS protocol. The PE100 fracture characterization throughout the J vs. Δa curves indicates that in both circumferential and longitudinal directions require similar quantities of energy to generate new fracture surfaces on HDPE pipes. Indeed, the orientation of the polymer chains as a result of pipe extrusion process could be not so relevant for predicting the direction of crack growth in HDPE pipes.
Analysis of the Stress Basis to Use for Creep Evaluation of Pipelines in Fitness-for-Service Assessments
Authors: Scano Lorenzo
Published: January 2014

High-energy pipelines are operated at very high pressures and temperatures, with a typical lifetime in the order of decades. Therefore, FFS assessments are periodically performed to evaluate piping safety against creep. Major design codes provide allowable stresses in the creep range; nevertheless, an actual stress basis is needed to calculate creep damage in a FFS procedure. In this paper, three stress bases were considered: the first one includes the primary circumferential and axial stresses, taking also into account the pressure inelastic redistribution. The second basis includes primary hoop and sustained code stresses. Finally, the third one considers EN13480 axial creep stress, including one third of the secondary expansion range. The stress bases were calculated for an example pipeline through a standard stress analysis and the API 579-1 standard was used to evaluate piping safe life. An inelastic, time-dependent analysis of the pipeline, including plasticity and creep, was then carried out via a shell FE model and the lifetime computed using a Level 3 procedure. The comparison between the investigations showed that the primary stress bases were non-conservative for creep evaluation. The combined primary and secondary stress basis led instead to a lifetime consistent with that calculated through the Level 3 procedure.
Severe Accident Condition Modeling in PWR Environment: Creep Rupture Modeling
Authors: Brust Frederick W. , Iyengar R. , Benson M. , Rathbun Howard
Published: January 2014

A problem of interest in the nuclear power industry involves the response of pressurized water reactor (PWR) pressure boundary components under long-term station blackout (SBO) conditions. SBO is a particularly challenging event to nuclear safety, since all alternating current power required for core cooling is lost. If unmitigated, such a scenario will eventually lead to the reactor core being uncovered. Thermal-hydraulic (T-H), computational fluid dynamics, and structural combined creep/plasticity analyses of this scenario have been conducted and are presented here.

In this severe accident scenario, high temperatures can occur, and impart this thermal energy to the surrounding structures, including the reactor vessel, nozzles, reactor coolant system (RCS) hot leg piping and S/G tubes. At such high temperatures and pressures, creep rupture of RCS piping and/or steam generator (S/G) tubes becomes possible. The intent of this paper is to present a finite element based analysis model that can be used to evaluate the time to failure of the nozzle-weld-pipe configuration.
Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (1) Overview
Authors: Asayama Tai , Dozaki Koji , Otani Tomomi , Inatomi Takanari , Ando Masanori
Published: January 2014

This paper presents the main features of 2012 Edition of JSME (Japan Society of Mechanical Engineers) Code for Design and Construction of Fast Reactors (JSME FR Code). The first edition of the JSME FR Code was published in 2005 based on the requirements that had been applied to the Japanese Prototype Fast Breeder Reactor Monju. The latest 2012 Edition incorporated 316FR stainless steel and Mod.9Cr-1Mo steel of which application to the Japanese demonstration fast reactors is expected. 316FR is a low-carbon nitrogen added fast reactor grade 316SS which has been developed in Japan. Allowable stresses up to 300,000 hours along with various material properties equations from which they have been derived have been codified. The applicability of the code rules on elevated temperature design to the new materials has been extensively investigated. Focus was on the creep-fatigue interaction evaluation methods, and predictability in long-term regions was carefully demonstrated based on material tests. Various structural tests were also conducted to verify that sufficient margins are maintained for the newly implemented materials. The JSME FR Code will be further upgraded in the 2016 and codes such as fitness-for-service code and leak-before-break evaluation code and a guideline for reliability evaluation of static components will be developed utilizing the System Based Code concept.
Mechanistic Study of FAC Processes Focused on the Oxide Layer Properties
Authors: Abe Hiroshi , Watanabe Yutaka
Published: January 2014

Detailed FAC processes and effects of local H2 partial pressure, oxide film porosity, and Cr content on the enhancement of dissolution through the oxide layer have been discussed focused on the result of FAC experiments and oxide layer characterizations. Porosity of oxide layer is closely related to corrosion resistance of the steels even in Cr content range of 0.003 to 1.01 wt %. Compact inner oxide layer suppress the diffusion of oxidizer (H2O) and Fe ion via pores, on the other hand, liquid-state diffusion through a porous oxide layer is considered to be dominant under high FAC rate conditions. The model of spiral enhancement of dissolution through the oxide layer has been proposed. It has been considered that FAC is enhanced with increase of local H2 partial pressure and film porosity. It has also been suggested that low solubility Fe-Cr spinel-type oxide formed on the high Cr content steels suppresses the spiral enhancement of dissolution through the oxide layer.
Improvements in Adapting mα-Tangent Method for Fitness for Service Evaluation of Local Thin Areas in Storage Tanks
Authors: Sathyanarayanan Sridhar , Adluri Seshu M. R.
Published: January 2014

Damage due to corrosion in the form of local thin area (LTA) is a widespread problem in hydrocarbon storage tanks. Fitness for service (FFS) methods are quantitative engineering evaluations that are performed to demonstrate the structural integrity of an in-service tank containing damage like LTAs and make run, repair or replace decisions. The mα-tangent method is a simplified limit load procedure that can be used for FFS evaluations. The method uses a kinematically active reference volume for evaluating the limit load multiplier. This paper reports preliminary results on the use of a modified reference volume approach by considering the reference volume inside the LTA, formed by the overlapping decay lengths from the LTA boundaries. The results from this approach are compared with the existing method which considers a much broader volume outside the damage as the reference volume and with nonlinear FEA. The Remaining Strength Factor (RSF) calculated from the modified reference volume also compares reasonably well with the results from American Petroleum Institute (API)/American Society of Mechanical Engineers (ASME) FFS procedure widely referred as API 579-1/ASME FFS-1. The study also finds that for large cylinders like tanks with very high R/t ratio, the circumferential decay lengths will be smaller than those previously reported (2.5Rt rather than 6.3Rt).
Modeling of Weld Residual Plastic Strain and Stress in Dissimilar Metal Butt Weld in Nuclear Reactors
Authors: Qiao Dongxiao , Feng Zhili , Zhang Wei , Wang Yanli , Crooker Paul
Published: January 2014

Primary water stress corrosion cracking (PWSCC) constitutes a major safety challenge for dissimilar metal welds (DMW) in pressurized water reactors. The reliability of structure integrity assessment of DMW is strongly dependent on the reliable determination of the weld residual stress (WRS) field, which is one of the primary driving forces for PWSCC. Recent studies have shown that today’s WRS models have varying degrees of success in determining the WRS in DMW that is highly dependent upon the strain-hardening models used in WRS simulation. The commonly used strain hardening model in WRS modeling (isotropic, kinematic, and mixed ones) appear to be inadequate in that they neglect the high-temperature time-dependent (viscous) deformation process during welding.

This work presents a new strain-hardening model derived from specially designed experiment that mimics the thermal-mechanical deformation process of a SS304L stainless steel under rapid heating and cooling conditions relevant to DMW. Compared to the time-independent strain hardening ones, the new strain hardening model, termed as Dynamic Strain Hardening model, takes into account the effect of time and temperature dependent dislocation annihilation and microstructure recrystallization processes at the elevated temperatures during welding. Moreover, a novel experimental approach based on micro-hardness testing is developed to quantify the residual equivalent plastic strain in a mock-up DMW. It is found that the new dynamic strain hardening model produces results that are more consistent with experimentally measured plastic strains and residual stresses. It is concluded that it is necessary to include the dynamic strain hardening recovery phenomenon to improve the accuracy of WRS predictions in DMW. Moreover, the newly developed micro-hardness based plastic strain measurement approach would be an effective means to quantify the plastic strain distributions which is another key factor for PWSCC in DMW in addition to the residual stresses.
Evaluation of Welding Residual Stress in GTAW Tubular Welds
Authors: Jin Hyung-Kook , Kim Ha-Geun , Shin Sang-Beom
Published: January 2014

The purpose of this study is to evaluate the welding residual stress of the tubular welds with welding pass and restraint conditions. For it, a heat input model for GTA (Gas Tungsten Arc) pulse welding was developed by comparing the molten pool shape and the temperature history in way of the weld obtained by FEA and experiment. The validation of evaluation procedure for welding residual stress with 3 dimensional thermo-mechanical analysis was also verified by comparing with measured results in the simple tubular weld. With the heat input model for GTA pulse welding and FEA procedure, the comprehensive 3 dimensional FEA were performed to evaluate the effect of the welding pass and restraint conditions on the distribution of welding residual stress and distortion in the actual tubular welds.
Limit Loads for Circumferentially Cracked Pipes Under Combined Bending and Torsion With Tension
Authors: Ryu Ho-Wan , Han Jae-Jun , Kim Yun-Jae
Published: January 2014

In power plants, piping installations with a circumferential crack can be operated under combined bending and torsion. ASME Boiler and Pressure Vessel code Section XI non-mandatory Appendix C provides the flaw evaluations for fully-plastic fracture using limit load criteria for the structural integrity of the cracked pipes. According to the recent version of Code, combined loading is provided only for membrane and bending. Even though actual operating conditions have torsion loading, the methodology for evaluating torsion load is not established, and assumed torsion is relatively small compared to membrane and bending and can be ignored in the evaluation.

This paper provides the results of limit load analyses by using finite element models for circumferentially cracked pipes under pure bending, pure torsion and combined bending and torsion with tension. Theoretical limit load solutions based on net-section fully-plastic criteria are compared with the results of finite element analyses. The validation of theoretical limit loads for combined bending and torsion with tension is discussed.
Mismatch Limit Loads of Circumferential Cracked Pipes With V-Groove Welds
Authors: Kim Sang-Hyun , Han Jae-Jun , Kim Yun-Jae
Published: January 2014

The present work reports mis-match limit loads for V-groove welded pipe for a circumferential crack using finite element (FE) analyses. In our previous paper [14], closed-form solutions of mis-match limit loads were proposed for idealized butt weld configuration as a function of the strength mis-match ratio with only one geometry-related slenderness parameter. To integrate the effect of groove angles on mis-match limit loads, the geometry-related slenderness parameter has to be modified by relevant geometric parameters including groove angle, crack depth and root opening based on plastic deformation patterns in theory of plasticity. Circumferential through-wall cracks are located at the centre of the weld considering two different groove angles (45°, 90°). With regards to loading conditions, axial (longitudinal) tension is applied for all cases. For the parent and weld metal, elastic-perfectly plastic materials are used to simulate under-matching and over-matching conditions in plasticity. The overall results from the proposed solutions agree well with FE results.
Comparison of J Resistance Curves From Toughness Testing Specimens With Those From Various Cracked Pipe Tests
Authors: Kim Jong-Hyun , Han Jae-Jun , Kim Yun-Jae , Shim Do-Jun
Published: January 2014

J contour integral still has great importance to predict fracture of both small specimen and full-scaled pipes. However, it is difficult to obtain experimental J resistance curve of full-scaled pipes due to the differences of defect shape and complexity of loads. Due to the recent development of the FE damage analysis to predict fracture of full-scaled pipes, it is also possible to predict J resistance of full-scaled pipes. To use this FE damage model for fracture estimation, it is necessary to verify the validity of this model by compared with toughness testing specimens.

In this paper, J resistance curves of full-scaled pipes using FE damage analysis were compared with various toughness testing specimens from Pipe Fracture Encyclopedia performed by Battelle. And the J contour integral were calculated from FE analysis using the element-size-dependent damage model recently proposed by the authors. Compared results showed that J calculation using FE damage analysis could be used for J-estimation of full-scaled pipes by compared with fracture toughness testing specimens.
Elastic-Plastic J-Estimation for Circumferentially Cracked Pipes Under Combined Mechanical and Thermal Loadings
Authors: Oh Chang-Young , Kim Yun-Jae , Ainsworth R. A.
Published: January 2014

This paper addresses load order effects on elastic-plastic J estimation under combined mechanical and thermal loads for circumferentially cracked pipes. The load order effects, for various thermal gradient types and mechanical loading, are evaluated for a range of magnitudes of the loadings, crack sizes and material hardening. Variations of elastic-plastic J obtained by finite element analysis are compared with existing and proposed methods for use with the R6 defect assessment procedure. The load order effects are presented on the R6 failure assessment diagram (FAD) by calculating the two parameters Kr and Lr from the finite element results. It is shown that there are significant load order effects at large secondary stress cases but these are successfully treated by simplified methods proposed for use with R6.
Finite Element Ductile Crack Growth Simulations of Specimens Under Combined Mechanical and Residual Stresses
Authors: Oh Chang-Young , Kim Jong-Hyun , Kim Yun-Jae , Budden P. J.
Published: January 2014

This paper provides simulations of ductile crack growth in test specimens using an element-size dependent damage model. The present method used in this paper is based on a stress modified fracture strain damage model with a stress reduction technique. The calibrated damage model is used to predict the load versus ductile crack growth response of test specimens. These tests included some samples that contained self-balancing residual stress distributions. The influence of a residual stress on the load versus crack growth relationship is accurately simulated using the element-size dependent damage model.
Identification of the Turbulence Force Field Excitation From a Set of Vibratory Responses of a Multi-Supported Tube
Authors: Antunes Jose , Borsoi Laurent , Delaune Xavier , Piteau Philippe
Published: January 2014

In this paper we address the identification of the spectral and spatial features of random flow excitations, for multi-supported tubular components such as steam generator tubes and nuclear fuel rods. In the proposed work, source identification is performed from a set of measured vibratory responses, in the following manner: (1) The modal response spectra and modeshape amplitudes at the measurement locations are first extracted through a blind decomposition of the physical response matrix, using the SOBI method; (2) The continuous modeshapes are interpolated from the identified values at the measurement locations; (3) The system modal parameters are identified from the modal responses using a simple SDOF fitting technique; (4) Inversion from the modal response spectra is performed for the identification of the modal excitation spectra; (5) Finally, an equivalent physical excitation spectra as well as the flow velocity profiles are estimated. The proposed approach is illustrated with identification results based on realistic numerical simulations of a multi-supported tube under linear support conditions.
Using the Nonlinear Kinematic Hardening Material Model of Chaboche for Elastic-Plastic Ratcheting Analysis
Authors: Kalnins Arturs , Rudolph Jürgen , Willuweit Adrian
Published: January 2014

Two calibration processes are selected for determining the parameters of the Chaboche nonlinear kinematic hardening (NLK) material model for stainless steel. One process is manual that requires no outside software and the other follows a finite element software. The basis of the calibration is the monotonic stress-strain curve obtained from a tension specimen subjected to unidirectional loading. The Chaboche model is meant for elastic-plastic ratcheting analysis that is included in commonly used design codes. It is chosen because it is known that it can represent realistically the materials that are used for power plant components and pressure vessels. To test the calibration results, a pressurized cylindrical shell subjected to thermal cycling is selected as an example. It was found that, for the example, no more than four Chaboche components should be used in the determination of its parameters.
Factors Affecting Steam Generator Tube Bow
Authors: Cao Moli , Nelson Jennifer , Charkas Hasan , Wiger Timothy
Published: January 2014

One of the challenges in straight shell-and-tube Steam Generator design is to avoid the tube to tube wear that can arise during operation due to higher than anticipated compressive tube loads and the resulting tube bow that can occur. Tube bow becomes significant when the compressive load in the tube exceeds its critical buckling capacity. This excessive load does not lead to unstable collapse of the tube as the axial load in the tube is displacement controlled. However, it does lead to significant lateral deformation for a very small increase in axial load/displacement. In this paper, several factors are investigated to determine their influence on the onset of tube bowing.

Based on the studies performed in this paper there are factors that play a significant role in the behavior of steam generator tubes that have not typically been addressed in associated design analyses. Failure to address these factors can lead to unexpected behavior, premature degradation of steam generator performance, and possibly pressure boundary failure. A thorough understanding of these factors is necessary to ensure that a given design will perform as expected.
Alternative Reference Temperature Based on Master Curve Approach in Japanese Reactor Pressure Vessel Steel
Authors: Hirota Takatoshi , Hirano Takashi , Onizawa Kunio
Published: January 2014

Master Curve approach is the effective method to evaluate the fracture toughness of the ferritic steels accurately and statistically. The Japan Electric Association Code JEAC 4216-2011, “Test Method for Determination of Reference Temperature, To, of Ferritic Steels” was published based on the related standard ASTM E 1921-08 and the results of the investigation of the applicability of the Master Curve approach to Japanese reactor pressure vessel (RPV) steels. The reference temperature, To can be determined in accordance with this code in Japan.

In this study, using the existing fracture toughness data of Japanese RPV steels including base metals and weld metals, the method for determination of the alternative reference temperature RTTo based on Master Curve reference temperature To was statistically examined, so that RTTo has an equivalent safety margin to the conventional RTNDT. Through the statistical treatment, the alternative reference temperature RTTo was proposed as the following equation; RTTo = To + CMC + 2σTo. This method is applicable to the Japan Electric Association Code JEAC 4206, “Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components” as an option item.
Hot Isostatic Pressing of Powder Metal as an Alternative to Forging of SA-723
Authors: Fridlund Linda
Published: January 2014

Hot Isostatic Pressing (HIP) of gas atomized powder has its major application for superalloys and high alloyed steels as e.g. tool steels, high speed steels and stainless steel. The HIP route offers not only finer microstructure and thus better mechanical properties in these alloys but also the possibility to make near net shape end products with isotropic properties. The expansion of the PM HIP Technology towards lower alloyed steels has been considered uneconomical compared to conventionally produced parts and sometimes not even feasible from a technical point of view. The major drawback has been the often reported inferior impact energy. This technical report will address how various parameters in the PM HIP process will influence the mechanical properties of end products and particularly causes and possible solutions to the impact problem.
EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters
Authors: Andreyev Andriy , Sitek Arkadiusz , Celler Anna
Published: January 2014

Purpose:

The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy.

Methods:

Recently, the authors have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as18F or 11C) and radiotracer B in which positron decay is accompanied by the emission of a high‐energy (HE) prompt gamma (such as 38K or 60 Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines‐of‐response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM‐based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions.

Results:

The authors’ experiments performed using Monte‐Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron‐gamma DIPET method or staggered injections alone.

Conclusions:

The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers.
Hyperleptinemia is Associated With CRP but Not Apolipoprotein E and is Reduced by Exercise Training
Authors: Lowndes Joshua , Zoeller Robert F. , Kyriazis George A. , Miles Mary P. , Seip Richard L. , Moyna Niall M. , Visich Paul S. , Pescatello Linda S. , Gordon Paul M. , Thompson Paul D. , Angelopoulos Theodore J.
Published: January 2014

The purpose of this study was to examine whether leptin levels affect the response of leptin to exercise training (ET) and whether this is also affected by C-reactive protein (CRP) or the three common Apolipoprotein E genotypes (APOE). Ninety-seven (male = 45, female = 52) sedentary individuals underwent 6 months of supervised ET. Blood was sampled before the initiation of ET, and again 24 and 72 hr after completion of the final training session. ET resulted in a small reduction in body mass (80.47 ± 18.03 vs 79.42 ± 17.34 kg, p < .01). Leptin was reduced 24 hr after the final exercise session (p < .01), but returned to normal after 72 hr (p > .05)—Pre: 13.51 ± 12.27, 24hr: 12.14 ± 12.34, 72hr: 12.98 ± 11.40 ng/ml. The most hyperleptinemic individuals had a greater initial response, which was sustained through to 72 hr after the final session in the pooled study population (p < .01), and in both males (p < .05) and females (p < .05) separately. CRP was related to leptin independently of body weight and positively related to the reductions in leptin. APOE genotype was not related to leptin levels and did not affect the response to ET. Leptin levels may only be reduced by ET in those with hyperleptinemia. In addition, both the initial extent of hyperleptinemia and the subsequent reduction in leptin may be related to low grade chronic systemic inflammation.
A Promiscuous Intermediate Underlies the Evolution of LEAFY DNA Binding Specificity
Authors: Sayou Camille , Monniaux Marie , Nanao Max H. , Moyroud Edwige , Brockington Samuel F. , Thévenon Emmanuel , Chahtane Hicham , Warthmann Norman , Melkonian Michael , Zhang Yong , Wong Gane Ka-Shu , Weigel Detlef , Parcy François , Dumas Renaud
Published: January 2014

LEAFY Evolution

It is generally believed that redundancy across gene copies allows for the evolution of novel function in proteins. However, it is less clear how single-copy genes with crucial function may evolve.

Sayou
et al.

(p.
645
, published online 16 January; see the Perspective by

Kovach and Lamb

) examined the evolution of the essential plant transcription factor LEAFY, which is generally found as a single-copy gene. LEAFY homologs in taxa representing the major evolutionary branches of the land plants and algae exhibited three classes of LEAFY binding sites. Structural analysis identified amino acid changes in the proteins, that were responsible for contacts with specific DNA motifs and allowed the likely effects of specific amino acid changes over the evolution of land plants to be resolved.
Sleep Perchance to Learn
Authors: Singh Manpreet K.
Published: January 2014

Humans have the capacity to learn new information during sleep.
Bacterial Cellulose as a Substrate for Microbial Cell Culture
Authors: Yin Na , Santos Thiago M. A. , Auer George K. , Crooks John A. , Oliver Piercen M. , Weibel Douglas B.
Published: January 2014

Bacterial cellulose (BC) has a range of structural and physicochemical properties that make it a particularly useful material for the culture of bacteria. We studied the growth of 14 genera of bacteria on BC substrates produced by
Acetobacter xylinum
and compared the results to growth on the commercially available biopolymers agar, gellan, and xanthan. We demonstrate that BC produces rates of bacterial cell growth that typically exceed those on the commercial biopolymers and yields cultures with higher titers of cells at stationary phase. The morphology of the cells did not change during growth on BC. The rates of nutrient diffusion in BC being higher than those in other biopolymers is likely a primary factor that leads to higher growth rates. Collectively, our results suggest that the use of BC may open new avenues in microbiology by facilitating bacterial cell culture and isolation.
Molecular Characterization of an NADPH-Dependent Acetoin Reductase/2,3-Butanediol Dehydrogenase from
Clostridium beijerinckii
NCIMB 8052
Authors: Raedts John , Siemerink Marco A. J. , Levisson Mark , van der Oost John , Kengen Servé W. M.
Published: January 2014

Acetoin reductase is an important enzyme for the fermentative production of 2,3-butanediol, a chemical compound with a very broad industrial use. Here, we report on the discovery and characterization of an acetoin reductase from
Clostridium beijerinckii
NCIMB 8052. An
in silico
screen of the
C. beijerinckii
genome revealed eight potential acetoin reductases. One of them (
CBEI_1464
) showed substantial acetoin reductase activity after expression in
Escherichia coli
. The purified enzyme (
C. beijerinckii
acetoin reductase [Cb-ACR]) was found to exist predominantly as a homodimer. In addition to acetoin (or 2,3-butanediol), other secondary alcohols and corresponding ketones were converted as well, provided that another electronegative group was attached to the adjacent C-3 carbon. Optimal activity was at pH 6.5 (reduction) and 9.5 (oxidation) and around 68°C. Cb-ACR accepts both NADH and NADPH as electron donors; however, unlike closely related enzymes, NADPH is preferred (

K
m

, 32 μM). Cb-ACR was compared to characterized close homologs, all belonging to the “threonine dehydrogenase and related Zn-dependent dehydrogenases” (COG1063). Metal analysis confirmed the presence of 2 Zn
2+
atoms. To gain insight into the substrate and cofactor specificity, a structural model was constructed. The catalytic zinc atom is likely coordinated by Cys
37
, His
70
, and Glu
71
, while the structural zinc site is probably composed of Cys
100
, Cys
103
, Cys
106
, and Cys
114
. Residues determining NADP specificity were predicted as well. The physiological role of Cb-ACR in
C. beijerinckii
is discussed.
Duplex PCR Methods for the Molecular Detection of
Escherichia fergusonii
Isolates from Broiler Chickens
Authors: Simmons Karen , Rempel Heidi , Block Glenn , Forgetta Vincenzo , Vaillancourt Rolland , Malouin François , Topp Edward , Delaquis Pascal , Diarra Moussa S.
Published: January 2014

Escherichia fergusonii
is an emerging pathogen that has been isolated from a wide range of infections in animals and humans. Primers targeting specific genes, including
yliE
(encoding a conserved hypothetical protein of the cellulose synthase and regulator of cellulose synthase island),
EFER
_
1569
(encoding a hypothetical protein, putative transcriptional activator for multiple antibiotic resistance), and
EFER
_
3126
(encoding a putative triphosphoribosyl-dephospho-coenzyme A [CoA]), were designed for the detection of
E. fergusonii
by conventional and real-time PCR methods. Primers were screened by
in silico
PCR against 489 bacterial genomic sequences and by both PCR methods on 55 reference and field strains. Both methods were specific and sensitive for
E. fergusonii
, showing amplification only for this bacterium. Conventional PCR required a minimum bacterial concentration of approximately 10
2
CFU/ml, while real-time PCR required a minimum of 0.3 pg of DNA for consistent detection. Standard curves showed an efficiency of 98.5%, with an
R
2
value of 0.99 for the real-time PCR assay. Cecal and cloacal contents from 580 chickens were sampled from broiler farms located in the Fraser Valley (British Columbia, Canada). Presumptive
E. fergusonii
isolates were recovered by enrichment and plating on differential and selective media. Of 301 total presumptive isolates, 140 (46.5%) were identified as
E. fergusonii
by biochemical profiling with the API 20E system and 268 (89.0%) using PCR methods.
E. fergusonii
detection directly from cecal and cloacal samples without preenrichment was achieved with both PCR methods. Hence, the PCR methods developed in this work significantly improve the detection of
E. fergusonii
.
pH Signaling in Human Fungal Pathogens: a New Target for Antifungal Strategies
Authors: Cornet Muriel , Gaillardin Claude
Published: January 2014

Fungi are exposed to broadly fluctuating environmental conditions, to which adaptation is crucial for their survival. An ability to respond to a wide pH range, in particular, allows them to cope with rapid changes in their extracellular settings. PacC/Rim signaling elicits the primary pH response in both model and pathogenic fungi and has been studied in multiple fungal species. In the predominant human pathogenic fungi, namely,
Candida albicans
,
Aspergillus fumigatus
, and
Cryptococcus neoformans
, this pathway is required for many functions associated with pathogenesis and virulence. Aspects of this pathway are fungus specific and do not exist in mammalian cells. In this review, we highlight recent advances in our understanding of PacC/Rim-mediated functions and discuss the growing interest in this cascade and its factors as potential drug targets for antifungal strategies. We focus on both conserved and distinctive features in model and pathogenic fungi, highlighting the specificities of PacC/Rim signaling in
C. albicans
,
A. fumigatus
, and
C. neoformans
. We consider the role of this pathway in fungal virulence, including modulation of the host immune response. Finally, as now recognized for other signaling cascades, we highlight the role of pH in adaptation to antifungal drug pressure. By acting on the PacC/Rim pathway, it may therefore be possible (i) to ensure fungal specificity and to limit the side effects of drugs, (ii) to ensure broad-spectrum efficacy, (iii) to attenuate fungal virulence, (iv) to obtain additive or synergistic effects with existing antifungal drugs through tolerance inhibition, and (v) to slow the emergence of resistant mutants.
A Genomewide Overexpression Screen Identifies Genes Involved in the Phosphatidylinositol 3-Kinase Pathway in the Human Protozoan Parasite Entamoeba histolytica
Authors: Koushik Amrita B. , Welter Brenda H. , Rock Michelle L. , Temesvari Lesly A.
Published: January 2014

Entamoeba histolytica
is a protozoan parasite that causes amoebic dysentery and liver abscess.
E. histolytica
relies on motility, phagocytosis, host cell adhesion, and proteolysis of extracellular matrix for virulence. In eukaryotic cells, these processes are mediated in part by phosphatidylinositol 3-kinase (PI3K) signaling. Thus, PI3K may be critical for virulence. We utilized a functional genomics approach to identify genes whose products may operate in the PI3K pathway in
E. histolytica
. We treated a population of trophozoites that were overexpressing genes from a cDNA library with a near-lethal dose of the PI3K inhibitor wortmannin. This screen was based on the rationale that survivors would be overexpressing gene products that directly or indirectly function in the PI3K pathway. We sequenced the overexpressed genes in survivors and identified a cDNA encoding a Rap GTPase, a protein previously shown to participate in the PI3K pathway. This supports the validity of our approach. Genes encoding a coactosin-like protein, EhCoactosin, and a serine-rich
E. histolytica
protein (SREHP) were also identified. Cells overexpressing EhCoactosin or SREHP were also less sensitive to a second PI3K inhibitor, LY294002. This corroborates the link between these proteins and PI3K. Finally, a mutant cell line with an increased level of phosphatidylinositol (3,4,5)-triphosphate, the product of PI3K activity, exhibited increased expression of SREHP and EhCoactosin. This further supports the functional connection between these proteins and PI3K in
E. histolytica
. To our knowledge, this is the first forward-genetics screen adapted to reveal genes participating in a signal transduction pathway in this pathogen.
Population of Endogenous Pararetrovirus Genomes in Carrizo Citrange
Authors: Roy Avijit , Shao Jonathan , Schneider William L. , Hartung John S. , Brlansky Ronald H.
Published: January 2014

The complete genome sequences of three related endogenous pararetroviruses (EPRVs) were obtained by 454 sequencing of nucleic acid extracts from Carrizo citrange, used as a citrus rootstock. Numerous homologous sequences have been found in the sweet orange genome. The new EPRVs are most closely related to petunia vein-clearing virus.
Whole-Genome Sequences of Streptococcus thermophilus Strains TH1435 and TH1436, Isolated from Raw Goat Milk
Authors: Treu Laura , Vendramin Veronica , Bovo Barbara , Campanaro Stefano , Corich Viviana , Giacomini Alessio
Published: January 2014

We report the genome sequences of two
Streptococcus thermophilus
strains, TH1435 and TH1436, isolated from raw goat milk devoted to the production of artisanal cheese in the Friuli-Venezia Giulia region in Italy. The genome sequences of these two quickly acidifying strains are the first available genome sequences of
S. thermophilus
strains isolated in Italy.
Complete Genome Sequence of Cronobacter sakazakii Strain CMCC 45402
Authors: Zhao Zhijing , Wang Lei , Wang Bin , Liang Haoyu , Ye Qiang , Zeng Ming
Published: January 2014

Cronobacter sakazakii
is considered to be an important pathogen involved in life-threatening neonatal infections. Here, we report the annotated complete genome sequence of
C. sakazakii
strain CMCC 45402, obtained from a milk sample in China. The major findings from the genomic analysis provide a better understanding of the isolates from China.
Draft Genome Sequences of 11 Staphylococcus epidermidis Strains Isolated from Wild Mouse Species
Authors: Wang Jun , Kuenzel Sven , Baines John F.
Published: January 2014

We report here the draft genome sequences of 11 strains of
Staphylococcus epidermidis
, a common bacterium inhabiting the skin of humans and other animals. These isolates, obtained from five mouse species, provide valuable information on the native
Staphylococcus
spp. of this important model organism and form a basis for studying host-bacterial interactions in their natural environment.
The Genome of the Predominant Equine
Lactobacillus
Species, Lactobacillus equi, Is Reflective of Its Lifestyle Adaptations to an Herbivorous Host
Authors: O'Donnell Michelle M. , Harris Hugh M. B. , O'Toole Paul W. , Ross R. Paul
Published: January 2014

We report the draft genome sequence of
Lactobacillus equi
strain DPC6820, isolated from equine feces.
L. equi
is a predominant
Lactobacillus
species in the horse hindgut microbiota. An examination of the genome identified genes and enzymes highlighting
L. equi
adaptations to the herbivorous gastrointestinal tract of the horse, including fructan hydrolases. This genome sequence may help us further understand the microbial ecology of the equine hindgut and the influence lactobacilli have on it.
Draft Genome Sequence of Kurthia huakuii LAM0618
T
, an Organic-Pollutant-Degrading Strain Isolated from Biogas Slurry
Authors: Ruan Zhiyong , Wang Yanwei , Song Jinlong , Zhai Yi , Zhang Chi , Chen Chao , Li Yanting , Zhao Bingqiang , Zhao Bin
Published: January 2014

Kurthia huakuii
LAM0618
T
is a facultative anaerobic pollutant-degrading bacterium isolated from biogas slurry. An analysis of the draft genome sequence of LAM0618
T
reveals a genome size of 3,585,165 bp, with a mean G+C content of 39.1%. The genome contains 3,560 coding sequences and 112 tRNA and 33 rRNA genes.
Draft Genome Sequence of Saccharomyces cerevisiae IR-2, a Useful Industrial Strain for Highly Efficient Production of Bioethanol
Authors: Sahara Takehiko , Fujimori Kazuhiro E. , Nezuo Maiko , Tsukahara Masatoshi , Tochigi Yuki , Ohgiya Satoru , Kamagata Yoichi
Published: January 2014

We sequenced the genome of
Saccharomyces cerevisiae
IR-2, which is a diploid industrial strain with flocculation activity and the ability to efficiently produce bioethanol. The approximately 11.4-Mb draft genome information provides useful insights into metabolic engineering for the production of bioethanol from biomass.
Complete Genome Sequence of
Hyphomicrobium nitrativorans
Strain NL23, a Denitrifying Bacterium Isolated from Biofilm of a Methanol-Fed Denitrification System Treating Seawater at the Montreal Biodome
Authors: Martineau Christine , Villeneuve Céline , Mauffrey Florian , Villemur Richard
Published: January 2014

Hyphomicrobium nitrativorans
strain NL23 has been isolated from the biofilm of a denitrification system treating seawater. This strain has the capacity to denitrify using methanol as a carbon source. Here, we report the complete genome sequence of this strain in an effort to increase understanding of the function of this bacterium within the biofilm.