bluuebunny/crossref_metadata_2025 huggingface dataset:
Crack-Tip Stress Field of Fully Circumferential Cracked Pipe Under Combined Tension and Thermal Loads
Authors: Je Jin-Ho , Kim Dong-Jun , Bae Keun-Hyung , Kim Yun-Jae
Published: November 2014

In the presence of excessive plasticity, the fracture toughness depends on the size and geometry. For material under fully yielded conditions, the stresses near the crack tip are not unique, but depend on geometry. So Single-parameter; J-approach is limited to high-constraint crack geometry. J-Q theory has been proposed in order to decide crack geometry constraint. This approach assumes that the crack-tip fields have two degrees of freedom. In this paper, based on J-Q theory, crack-tip stress field of fully circumferential cracked pipe under combined load is investigated using FE analysis. Combined loads are tensile axial force and thermal gradient of radial direction. Q-stresses of a crack geometry and it’s loading state are used to determine constraint effect, and give a characteristic order for crack-tip constraint.
Development and Application of Risk-Based Inspection in Ethylene Compression Unit
Authors: Si Jun , Yang Yuqing , Yan Zhenrong , Luo Xiaoming
Published: November 2014

Inspections are widely used in the process industries to reduce risk related to failure on static mechanical equipment. Risk-based inspection is one of effective tools to optimize inspection and maintenance planning. Based on principle of the risk-based inspection methodology, the main failure modes and damage mechanisms of pressure vessels and pipelines in ethylene compression unit are identified. The risk assessment of pressure vessels and pipelines is carried out. All pressure vessels and pipelines in this unit are prioritized based on the level of risk. Risk mitigation measures and optimal inspection and maintenance strategy are proposed. The results of risk evaluation have highlighted a clear improvement in the quality of inspection and maintenance of the ethylene compression unit.
On Pipe Elbow Elements in ABAQUS and Benchmark Tests
Authors: Zeng Lingfu , Jansson Lennart G. , Venev Yordan
Published: November 2014

In this paper, elbow elements in commercial finite element software ABAQUS are reviewed and two commonly used elements, ELBOW31 (2-node, linear) and ELBOW32 (3-node, quadratic), are numerically tested for two Benchmark examples: a cantilever pipe and an in-plane bending pipe bend. Two main issues are studied through the numerical tests: (1) The effect of the element size and the number of ovalization modes chosen for computation; (2) The accuracy of computed deformation and stresses. To gain an insight into the behavior of these elements, a comparison against published results by experiment and computations using elbow elements in software ADINA and MARC, as well as computations using ABAQUS shell elements, is conducted. It is shown that: (i) these elements predict a good peak stress solution with a reasonably coarse mesh and 6 ovalization modes; (ii) the ovalization and the distribution of stresses predicted around the pipe section show, though using a relatively dense mesh, a notable difference as compared to solutions computed by ABAQUS shell elements; (iii) the ADINA elbow element seems to provide, though using a very coarse mesh, a solution closest to analytic and experimental results. It is concluded that there are great needs for in-depth studies on elbow elements regarding reliability and accuracy issues.
Further Developments to the Change Gasket
Authors: Bond Stephen , Jamalyaria Ebadollah
Published: November 2014

Currently, there are two well established and common types of gaskets which cover most critical high pressure and high temperature applications in industry. Spiral wound type gaskets have been in use as one of the most versatile types of gaskets since it was invented over 100 years ago by Flexitallic. Grooved metal gaskets with a covering of soft sealing material, also known as Kammprofile gaskets are the other most common type used in critical applications, these have also been in existence over 80 years. Each of these two types have their specific characteristics making them strong in some areas and less strong in other aspects. A novel type called “Change Gasket” is a cross between two types, that combines the beneficial features of each of the above types in one product. The various test results showing its improved performance over traditional gaskets, as well as engineering features built into this product will be discussed in this paper. This paper will discuss the recent developments and updates to Change gasket.
Case Study: Failure Analysis of a BFJ in Cyclic Service
Authors: Seipp Trevor G.
Published: November 2014

A bolted flange joint was in cyclic temperature and pressure service in a natural gas dehydrator (mole sieve) vessel. The flange joint suffered from multiple failures on a frequent (9 month) basis.

This paper details the investigation into the failure and highlights the most probable cause of failure. A finite element analysis of the pressure and temperature transients in the bolted flange joint pointed to the temperature cycle as tending to unload the joint. Then, a parametric study was undertaken to evaluate the effectiveness of potential solutions.

The bolted flange joint was placed back into service and has been operating for more than three times the prior mean time between failures.
Residual Stresses in Alloy 182 PWHT Buttering and Attachment Weld: Validation by Modeling and Measurements of a Full Scale Mockup
Authors: Bremberg Daniel , Gunnars Jens , Bonnaud Etienne , Edling Lars-Olof , Kingston Ed
Published: November 2014

Internal components in nuclear reactor pressure vessels are joined to the ferritic vessel by use of dissimilar metal welds which commonly include nickel base weld material Alloy 182. It has turned out that Alloy 182 sometimes is susceptible to stress corrosion cracking (SCC) for the operating environment in reactors. Tensile residual stress has a large influence on SCC and it is important to carefully characterize the residual stresses generated at manufacturing. The manufacturing of these welds includes welding Alloy 182 to the ferritic steel to form a buttering, post-weld heat treatment (PWHT) of the buttering, and finally attachment welding between the internal component and the buttering.

An experimental program was designed for measurement and numerical analysis for validation of residual stresses in a nickel base Alloy 182 weld between the core shroud support leg and reactor pressure vessel. Two full-scale mock-ups were manufactured according to the original procedures for the buttering to the ferritic steel and the final attachment weld to the core shroud support. The mock-up was also carefully designed to produce correct boundary conditions for the support leg. Measurements were performed by the deep-hole drilling technique (DHD/iDHD). The residual stress fields from welding and heat treatments were predicted by detailed numerical modelling. Comparison between the numerical results and the measurement results shows very good agreement and validates the predicted residual stresses. It was concluded that the PWHT of the vessel only partly relieve weld residual stresses in the nickel base buttering.
MR Damper That Utilizes Multi Pole Electromagnets
Authors: Matsuoka Taichi , Sugita Tomohiro , Sunakoda Katsuaki
Published: November 2014

The authors propose a Magneto-Rheological (MR) fluid damper that utilizes multi pole electromagnets in order to control variable damping effect such as a semiactive damper. The damper consists of a piston, a cylinder, a by-pass pipe, 8 electromagnets, and MR fluid. The electromagnets are installed octagonal around the pipe. When each electromagnet can control both of the magnetic flux density and direction, resisting force can be switched by several types of magnetic field such as artificial orifice. The test damper is manufactured. Resisting force characteristics are measured by using a shaking actuator. Finally, dynamic performance of the damper is confirmed experimentally.
Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 6 — Scaled Tests to Obtain Basic Characteristics of Lead Rubber Bearing
Authors: Hirotani Tsutomu , Takahama Ryota , Yukawa Masaki , Hibino Hiroshi , Aikawa Yuji , Hirai Hideo , Imaoka Tetsuo , Shimizu Hiroshi , Umeki Yoshito
Published: November 2014

This paper provides a series comprising the “Development of Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Part 6 presents scaled tests for Lead Rubber Bearing (LRB) newly developed for this project.

Following tests are performed to obtain the basic characteristics of LRB,.

(1) Horizontal and Vertical Simultaneous Loading Test:

LRBs with diameter of 250mm are tested dynamically under simultaneous axial and lateral loading. The hysteresis characteristics is not changed under compressive load although it is changed under tensile load.

(2) Basic Break Test:

LRBs with a diameter of 800mm are tested statically under various combinations of axial and lateral forces. The hysteresis characteristics model of LRB is determined by this test. It is confirmed that the breaking strain of LRB under compression load exceeds 450%.

(3) Horizontal Hardening and Vertical Softening Test:

For LRBs with a diameter of 1200 mm, 75% scale of actual LRB are tested statically for horizontal hardening and vertical softening regions. It is confirmed that the hysteresis model which is developed by smaller LRBs is applicable to these large scale models.
Modelling and Measuring Residual Stresses in Pipe Girth Welds: Lessons From the Style Framework 7 Project
Authors: Smith Mike C. , Muransky Ondrej , Smith David , Do Son Cao , Bouchard P. John , Mathew Jino
Published: November 2014

A number of girth-welded pipe mock-ups have been manufactured and investigated during the STYLE project, using a wide range of measurement techniques accompanied by extensive finite element simulation campaigns. This paper gives an overview of the work carried out and presents preliminary conclusions on the performance of finite element weld residual stress simulation techniques in the different mock-up designs.
Overview of Welding Research Under the New Nuclear Manufacturing (NNUMAN) Programme
Authors: Jeyaganesh B. , Callaghan M. D. , Francis J. A. , English P. D. , Vasileiou A. , Roy M. J. , Guo W. , Irvine N. M. , Smith M. C. , Li L. , Sherry A. H.
Published: November 2014

The New Nuclear Manufacturing (NNUMAN) programme was established in the UK in late 2012, to develop new manufacturing technologies for nuclear components. One of the themes of this programme is research to develop candidate advanced joining methods using arc and high-energy welding processes, for components manufactured using nuclear grade reactor pressure vessel steel SA508 Grade 3 Class 1. The key outcomes of this study are the comparison of residual stresses and mechanical properties of welded mock-ups as a function of different welding processes, together with the development and validation of numerical models to predict residual stresses and mechanical properties. This paper gives an overview of the NNUMAN welding programme, coupled with design of experiments to date. The ultimate objective of this research is aimed at determining the effect of the selection of welding process, on the performance of nuclear components with operational lifetimes of 60 years or greater.
Finite Element Analysis Applied to Vortex Finder Modifications
Authors: Hari Yogeshwar , Relangi Ramana
Published: November 2014

The objective of this paper is to use finite element analysis in determining stresses in a Vortex Finder. Vortex Finder is tube projecting into central vortex of hydro cyclone or dense medium cyclone through which the classified fines or lighter specific gravity fraction of pulp leaves the system. Two Loading Conditions are considered. The stresses determined for the loading conditions are compared with allowable stresses for the material used for the Vortex Finder. Modifications are made to the Vortex Finder and in that also several design modifications are considered. Case 1 Original Design. Case 2 Modified model add eight Additional support connections and eight guests. Case 3 Same as Case 2 Double Elements to see effect on stresses. Case 4 Vortex Finder Modified Double Elements Air Velocity 100 ft. /sec. Case 5 Vortex Finder Modified Double Elements Change in Air Velocity 100 feet/sec. Add 6 support connections and guests removed. Case 6 Vortex Finder Modified Double Elements Air velocity 100 feet per sec. Add six more support connections and gussets Remove gussets move support points closer. For all the cases the stresses were compared with the allowable stresses. It was determined Case 6 with 24 total supports was the best. No Gussets. Support points moved closure. The maximum stress obtained by FEA Model meets the allowable stresses. This is robust design modification. This was implemented.
Integrity Management of Large Size Atmospheric Storage Tank
Authors: Li Guanghai , Chen Haoyu , Fang Zhou , Liu Deyu , Jia Guodong , Wei Yaodong
Published: November 2014

Recently, the integrity management of large size atmospheric storage tank in China is still in the preliminary stage. The purpose and the concept of integrity management, the core technical system and the management system are discussed. Main system framework of integrity management about large size atmospheric storage tank is developed, combining with the characters including super-large inner volume, corrosive nature of storage media, dangerous of leakage explosion, strict request for non-interruption operating, and related national codes about integrity management. Two elements of the system, an integrity management process of large size atmospheric storage tanks which combines quality control, management of change, performance test, communication consulting, and an integrity management technology system of large size atmospheric storage tank which is composed of data collecting, risk evaluation, integrity evaluation, responses measures, are proposed. At the same time, the procedure of integrity management is applied to an oil depot in a petrochemical company. The risk evaluation and the integrity evaluation were made on 34 storage tanks. To reduce the risk, some measures are put forward to the 9 storage tanks in medium high risk. As a result, all the large size atmospheric storage tanks are controlled at a medium low level.
A Life Management Method on In-Service Equipment in Refining Unit
Authors: Wang Hui , Jia Guodong , Li Xiang , Xie Guoshan , Wang Weihua
Published: November 2014

A life management approach on in-service device in refining unit was presented in this paper. By means of this method, corporate resources can reasonably be allocated. And a long-term operation of the equipment can be ensured. First, according to the type of the equipments, statistical analysis of equipments was carried out to obtain the life stages: early life stage, middle life stage, late life stage, extended life stage. Then, based on damage mechanism residual life of the equipments was calculated out. At the same time, the recommended maintenance cycle was given. If the operational life of the equipments cannot meet the expected life, the cause analysis should be done. The subsequent processing steps, such as maintenance, repair and renewal were proposed. Next, the equipments in the corporation were classified. For different class of the equipments, the different management methods were given. Finally, a re-evaluation of life was conducted.
Prediction of Cladding Temperatures Within a Used Nuclear Fuel Transfer Cask Filled With Rarefied Helium
Authors: Manzo Ernesto T. , Green Rachel , Nacer Mustafa Hadj , Greiner Miles
Published: November 2014

During the used nuclear fuel vacuum drying process, helium is evacuated to pressures as low as 70 Pa, to promote water vaporization and removal. At these low pressures the gas is rarefied to the extent that there is a temperature jump thermal resistance between the surface and gas. This occurs when the mean free path of a molecule becomes a comparable to the characteristic length of a system. In order to correctly apply this jump model to a nuclear transfer cask, a two dimensional model of parallel plates and concentric cylinders were created using ANSYS/Fluent package. Heat generation was plotted against a variety of relevant pressures. The results in these simple geometries are compared to kinetic model calculations, performed by other investigators, to determine the appropriate collision diameters to use in rarefied helium gas simulations within complex geometries. A two dimensional mesh of a transfer cask containing 24 pressurized water reactor used fuel assemblies is then constructed, and the rarefied gas model was implemented in the helium-filled regions between the fuel and basket support structures. Steady state simulations with a fuel heat generation rate of 710 W/m/assemble shows that the cladding is measurably hotter when the helium gas pressure is reduced from atmospheric conditions ∼105 Pa to 500 Pa. The heat generation rate that brings the peak cladding temperature to a hydride dissolution temperature of 400°C is as much as 10% lower when the gas is at 500 Pa than under atmospheric conditions.
Analysis of the Pressure Transient and Burst Pressure for Exposure of the 9975 Primary Containment Vessel to Fire
Authors: Laurinat James E. , Askew Neal M. , Hensel Steve J. , Gupta Narendra K.
Published: November 2014

Bare shipping package containment vessels can be utilized to stage plutonium oxide at the Savannah River Site. Pressurization and subsequent release could occur due to a hypothetical facility fire. Pressurization due to adsorbed moisture on the plutonium oxide and plastic packaging materials could result in rupture of the containment vessel. The containment vessel was evaluated to determine rupture pressure when subjected to the fire conditions. The rupture pressure is compared with pressures developed due to radiolytic gas generation.
Time and Temperature Dependent Property of a Sensor Candidate Material: Polymer Derived Ceramics (PDC)
Authors: Cui T. , Shao G. , An L. , Wang W. , Chao Y. J. , Lam P. S. , Mendez-Torres A.
Published: November 2014

The piezoresistivity and the micro fabrication capability have made the polymer derived ceramics (PDCs) an excellent candidate material for high temperature sensors. In this study, it was found that PDCs also exhibit creep and stress relaxation properties. Its electric resistance may change with time under certain loading conditions. In addition, the creep/stress relaxation rate is sensitive to temperature. It is demonstrated that even PDC materials have been processed at high temperatures and formed ceramic structure, they retain certain polymeric characteristics. Due to the piezoresistivity properties of PDC and its resilience to harsh environment, in particular, the predicted resistance to radiation field, the PDC based sensors are ideal for use as sensing media that can be deployed to important to safety (ITS) structures in nuclear systems, such as cooling water system and coolant pumps in light water reactors (LWRs).
Fracture Failure Research on Feculence Discharge Pipe of LPG Spherical Tanks
Authors: Chen Wang , Jin Chen , XiaoHui Cai , YinPei Wang
Published: November 2014

The rupturing of feculence discharge pipe happened during the gas-tightness test of LPG (Liquefied petroleum gas) spherical tanks. In order to find out the reasons of fracture failure of feculence discharge pipe, the Scanning electron microscopy (SEM) analysis, mechanical property testing, metallographic examination and energy spectrum analysis of corrosion products were used. The examination results show that both chemical composition and metallographic structure are normal, and the cracking is the brittle cleavage fracture. The energy spectrum analysis of corrosion products reveals that there are many sulfides in the corrosion products. Based on the loading conditions of spherical tanks, crack morphology and corrosion products, the primary reason of pipe cracking is stress corrosion cracking induced by H2S existed in liquefied petroleum gas. So it is suggested that the examination should be fulfilled for the feculence discharge pipe of such spherical tanks, the cracked pipes should be replaced, and the welding residual stress in the pipes should be relieved before replacing operation.
Residual Stresses in Butt Welding of Two Circular Pipes: An Experimental and Numerical Investigation
Authors: Brar Gurinder Singh
Published: November 2014

Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Welding is carried out with a very complex thermal cycle which results in irreversible elastic-plastic deformation and residual stresses in and around fusion zone and heat affected zone (HAZ). A residual stress due to welding arises from the differential heating of the plates due to the weld heat source. Residual stresses may be an advantage or disadvantage in structural components depending on their nature and magnitude. The beneficial effect of these compressive stresses have been widely used in industry as these are believed to increase fatigue strength of the component and reduce stress corrosion cracking and brittle fracture. But due to the presence of residual stresses in and around the weld zone the strength and life of the component is also reduced. To understand the behavior of residual stresses, two 10 mm thick Fe410WC mild steel plates are butt welded using the Metal Active Gas (MAG) process. An experimental method (X-ray diffraction) and numerical analysis (finite element analysis) were then carried out to calculate the residual stress values in the welded plates. Three types of V-butt weld joint — two-pass, three-pass and four-pass were considered in this study. In multi-pass welding operation the residual stress pattern developed in the material changes with each weld pass. In X-ray diffraction method, the residual stresses were derived from the elastic strain measurements using a Young’s modulus value of 210 GPa and Poisson’s ratio of 0.3. Finite element method based, SolidWorks software was used to develop coupled thermal-mechanical three dimension finite element model. The finite element model was evaluated for the transient temperatures and residual stresses during welding. Also variations of the physical and mechanical properties of material with the temperature were taken into account. The numerical results for peak transverse residual stresses attained in the welded plates for two-pass, three-pass and four-pass welded joint were 67.7 N/mm2, 58.6 N/mm2, and 48.1 N/mm2 respectively. The peak temperature attained during welding process comes out to be 970°C for two-pass weld, 820.8°C for three-pass weld and 651.9°C for four-pass weld. It can be concluded that due to increase in the number of passes during welding process or deposition weld beads, the residual stresses and temperature distribution decrease. Also, the results obtained by finite element method agree well with those from experimental X-ray diffraction method.
Failure Behavior of Structural Square Hollow Section Corner Welded Joint
Authors: Singh Harpuneet , Brar Gurinder Singh , Singh Harmeet
Published: November 2014

Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Welding is carried out with a very complex thermal cycle which results in irreversible elastic-plastic deformation and residual stresses in and around fusion zone and heat affected zone (HAZ). Due to the presence of residual stresses in and around the weld zone the strength and life of the component is largely reduced. An application of corner joint of square hollow section (IS 4923:1997 YSt 240) of 49.5mm × 49.5mm × 2.0mm in size is welded by the Metal Active Gas (MAG) process. To know the failure behavior of square hollow section corner welded joint various load test including bending test and shear test were performed on universal testing machine (UTM). Finite element based software SolidWorks Simulation was used to model the joint and for calculation of load stresses. Residual stress value was 512MPa and 516MPa, which is in good agreement with experimental, results (X-ray diffraction (XRD) technique). Welding parameters were optimized further using finite element model in order to reduce the residual stress. Failure behavior shows that welding has good strength both in bending and shearing test and small displacements at maximum applied load. By reduction in residual stress, displacement decreases five percentages in bending test and negligible change occurs in shear test.
Optimal Make-Up Torque for Trapezoidal Threaded Connections Subjected to Combined Axial Tension and Internal Pressure Loading
Authors: Galle Timothy , De Waele Wim , Van Wittenberghe Jeroen , De Baets Patrick
Published: November 2014

When assembling tubing strings in the oilfields, threaded connections are used to connect the pipes with each other. The possibility to reuse these connections is often required and a certain degree of leak tightness is required, even without the use of a sealing surface or shoulder. For this reason, the total plasticity within the connection should be limited and relative movement between pin and box ought to be restricted.

Within this publication, a finite elements analysis is conducted using a 4.5 inch buttress threaded connection as defined in API 5B together with a connection using the enhanced SR23 buttress thread. In addition, an experimental validation of the make-up stage is conducted by comparing the strains generated during make-up using Digital Image Correlation and infrared monitoring.

In order to determine the optimal make-up, values found in literature are compared with a developed method using the magnitude and size of the plastically deformed zones during make-up. In addition, the effect of external axial and pressure loading is examined to identify the effects and critical areas.

As a result, it is observed that pressure loading and make-up tend to have similar effects and in order to determine the optimal make-up torque, the pressure ratings of the assembly should be taken into account to prevent overtorqueing the connection. For the case of axial loading, a critical zone is visible near the last engaged thread and excessive loading of this thread can cause premature failure within this zone. Overall, the SR23 connection shows limited, yet visible, advantages over the standard BTC connection as described in literature.
Transient and Fatigue Monitoring Operational Feedback Application and Evaluation
Authors: Meikle Thomas L. , Wetmore William R. , Gray Mark A.
Published: November 2014

Reviewing online monitoring data led engineers at a U. S. domestic power plant to discover some periodic transient activity occurring in the unisolable sections of the plant’s safety injection (SI) lines. This activity typically occurred when the plant approached hot standby conditions after an outage. After performing an investigation, it was concluded that the activity was caused by periodic SI check valve testing. Effective review and disposition of the monitoring results supported engineering feedback to operations personnel with recommendations for performing check valve testing to mitigate further thermal shocks on the downstream components. Engineering was also able to classify the observed transient activity as one of the transients in the SI line licensing basis, to justify continued operation without significant engineering analysis, using the WESTEMS™ Design Envelopes approach to transient cycle counting. This paper describes the approaches used to identify the unexpected transient activity, evaluate and classify the activity using an efficient automated approach, and to develop recommendations for mitigating actions for plant operation.
Evaluation of a Weld Overlay Design for a Bimetallic Weld Using the Failure Assessment Diagram
Authors: Heldt Jens , Lohse Christopher , Cofie Nathaniel G. , Lashley Michael
Published: November 2014

During routine inspection of an N5 feedwater nozzle dissimilar metal weld (DMW) of a BWR, an axial flaw was detected in the weld. The flaw was mitigated by applying a full structural weld overlay (WOL) repair consisting of Alloy 52M weld metal and using the gas tungsten arc welding process (GTAW). Because of the ductile nature and very high toughness of the Alloy 52M material, the limit load approach of ASME Code, Section XI, Appendix C was used for the sizing of the overlay. The use of limit load for the design of weld overlays for Alloy 52M material is supported by several studies documented in the industry [1].

In order to address other fracture failure modes such as failure by ductile tearing and brittle fracture, a failure assessment diagram (FAD) approach was used to evaluate the acceptability of the weld overlay design. FADs have been used for evaluating flaws in piping components, but not for acceptance of flaws in WOLs. The FAD evaluation was performed in accordance with the ASME Code, Section XI, Appendix H requirements which address brittle fracture, elastic-plastic fracture mechanics (ductile tearing), and limit load failure modes. The applicable stress combinations were used in combination with the materials JR resistance curve to determine flaw acceptability at the end of the evaluation period.

The evaluation considered the presence of both a circumferential flaw (360° around the circumference and 100% through the original pipe wall; the design basis for the full structural weld overlay) and an axial flaw. For both circumferential and axial flaws, several assessment points corresponding to the JR resistance curve were determined and plotted on the FAD curve for austenitic steels in ASME Section XI, Appendix H. The FAD curve in Appendix H was derived based on strength properties of stainless steel and is considered conservative in application to Alloy 52M since Alloy 52M has higher strength. All the assessment points were found to be below the FAD curve thus indicating the acceptability of the weld overlay with consideration to all the three possible fracture regimes.
The Effects of Maintenance Actions on the PFDavg of Spring Operated Pressure Relief Valves
Authors: Bukowski Julia V. , Goble William M. , Gross Robert E. , Harris Stephen P.
Published: November 2014

The safety integrity level (SIL) of equipment used in safety instrumented functions is determined by the average probability of failure on demand (PFDavg) computed at the time of periodic inspection and maintenance, i.e., the time of proof testing. The computation of PFDavg is generally based solely on predictions or estimates of the assumed constant failure rate of the equipment. However, PFDavg is also affected by maintenance actions (or lack thereof) taken by the end user. This paper shows how maintenance actions can affect the PFDavg of spring operated pressure relief valves (SOPRV) and how these maintenance actions may be accounted for in the computation of the PFDavg metric. The method provides a means for quantifying the effects of changes in maintenance practices and shows how these changes impact plant safety.
Quake Aftermath: Christchurch Journalists' Collective Trauma Experience and the Implications for Their Reporting
Authors: Scanlon Sean
Published: November 2014

On February 22, 2011, Christchurch-based journalists were jolted out of their normal work routine by a large 6.3 magnitude earthquake that killed 185 people, wrecked the city and forced reporters to reappraise their journalism. This study considers how the earthquake affected journalists’ relationship to the community, their use of sources and news selection. A theory of collective trauma is used to explain the changes that journalists made to their reporting practice. Specifically, Christchurch journalists had a greater identification and attachment to their audience post-earthquake. Journalists viewed themselves as part of the earthquake story, which prompted them to view sources differently, use those sources differently and see advocacy as a keystone of their news work after the disaster. This study adds to a growing scholarship about journalists and trauma, but focuses on what the event meant for local reporters’ choice of sources and news selection rather than measuring rates of psychological distress.
Thermal MEMS actuator operation in aqueous media/seawater: Performance enhancement through atomic layer deposition post processing of PolyMUMPs devices
Authors: Warnat Stephan , Forbrigger Cameron , Hubbard Ted , Bertuch Adam , Sundaram Ganesh
Published: November 2014

A method to enhance thermal microelectromechanical systems (MEMS) actuators in aqueous media by using dielectric encapsulation layers is presented. Aqueous media reduces the available mechanical energy of the thermal actuator through an electrical short between actuator structures. Al2O3 and TiO2 laminates with various thicknesses were deposited on packaged PolyMUMPs devices to electrically separate the actuator from the aqueous media. Atomic layer deposition was used to form an encapsulation layer around released MEMS structures and the package. The enhancement was assessed by the increase of the elastic energy, which is proportional to the mechanical stiffness of the actuator and the displacement squared. The mechanical stiffness of the encapsulated actuators compared with the noncoated actuators was increased by factors ranging from 1.45 (for 45 nm Al2O3 + 20 nm TiO2) to 1.87 (for 90 nm Al2O3 + 40 nm TiO2). Displacement measurements were made for all laminate combinations in filtered tap water and seawater by using FFT based displacement measurement technique with a repeatability of ∼10 nm. For all laminate structures, the elastic energy increased and enhanced the actuator performance: In seawater, the mechanical output energy increased by factors ranging from 5 (for 90 nm Al2O3) to 11 (for 90 nm Al2O3 + 40 nm TiO2). The authors also measured the long-term actuator stability/reliability in seawater. Samples were stored for 29 days in seawater and tested for 17 days in seawater. Laminates with TiO2 layers allowed constant operation over the entire measurement period.
Pharmacodynamics of Imipenem in Combination with β-Lactamase Inhibitor MK7655 in a Murine Thigh Model
Authors: Mavridou Eleftheria , Melchers Ria J. B. , van Mil Anita C. H. A. M. , Mangin E. , Motyl Mary R. , Mouton Johan W.
Published: November 2014

MK7655 is a newly developed beta-lactamase inhibitor of class A and class C carbapenemases. Pharmacokinetics (PK) of imipenem-cilastatin (IMP/C) and MK7655 were determined for intraperitoneal doses of 4 mg/kg to 128 mg/kg of body weight. MIC and pharmacodynamics (PD) studies of MK7655 were performed against several beta-lactamase producing
Pseudomonas aeruginosa
and
Klebsiella pneumoniae
strains to determine its effect
in vitro
and
in vivo
. Neutropenic mice were infected in each thigh 2 h before treatment with an inoculum of approximately 5 × 10
6
CFU. They were treated with IMP/C alone (every 2 hours [q2h], various doses) or in combination with MK7655 in either a dose fractionation study or q2h for 24 h and sacrificed for CFU determinations. IMP/MK7655 decreased MICs regarding IMP MIC. The PK profiles of IMP/C and MK7655 were linear over the dosing range studied and comparable with volumes of distribution (
V
) of 0.434 and 0.544 liter/kg and half-lives (
t
1/2
) of 0.24 and 0.25 h, respectively. Protein binding of MK7655 was 20%. A sigmoidal maximum effect (
E
max
) model was fit to the PK/PD index responses. The effect of the inhibitor was not related to the maximum concentration of drug in serum (
C
max
)/MIC, and model fits for
T
>MIC
and area under the concentration-time curve (AUC)/MIC were comparable (
R
2
of 0.7 and 0.75), but there appeared to be no significant relationship of effect with dose frequency. Escalating doses of MK7655 and IMP/C showed that the AUC of MK7655 required for a static effect was dependent on the dose of IMP/C and the MIC of the strain, with a mean area under the concentration-time curve for the free, unbound fraction of the drug (
f
AUC) of 26.0 mg · h/liter. MK7655 shows significant activity
in vivo
and results in efficacy of IMP/C in otherwise resistant strains. The exposure-response relationships found can serve as a basis for establishing dosing regimens in humans.
Prophylaxis with Teicoplanin and Cefuroxime Reduces the Rate of Prosthetic Joint Infection after Primary Arthroplasty
Authors: Tornero Eduard , García-Ramiro Sebastian , Martínez-Pastor Juan C. , Bori Guillem , Bosch Jordi , Morata Laura , Sala Marta , Basora Misericordia , Mensa Josep , Soriano Alex
Published: November 2014

The aim of this study was to compare the prosthetic joint infection (PJI) rate after total joint arthroplasty in two consecutive periods of treatment with different antibiotic prophylaxes: cefuroxime versus cefuroxime plus teicoplanin. We retrospectively reviewed 1,896 patients who underwent total hip arthroplasty or total knee arthroplasty between March 2010 and February 2013. From March 2010 to August 2011, patients received 1.5 g of cefuroxime during induction of anesthesia and another 1.5 g 2 h later (the C group). From September 2011, 800 mg of teicoplanin was added to cefuroxime (the CT group). Throughout the period studied, there were no variations in pre- or postoperative protocols. Univariate and multivariate analyses were performed to evaluate independent predictors of PJI. There were 995 (55.7%) patients in the C group and 791 (44.3%) in the CT group. Patients in the CT group had a significantly lower PJI rate than patients in the C group (1.26% versus 3.51%,
P
= 0.002). There were no infections due to
Staphylococcus aureus
in the CT group (0% versus 1.6% in the C group,
P
< 0.001). A stepwise forward Cox regression model identified male sex (hazard ratio [HR], 3.85; 95% confidence interval [CI], 2.09 to 7.18), a body mass index of ≥35 kg/m
2
(HR, 2.93; 95% CI, 1.37 to 6.27), the presence of lung disease (HR, 2.46; 95% CI, 1.17 to 5.15), and red blood cell transfusion (HR, 3.70; 95% CI, 1.89 to 7.23) to be independent variables associated with a higher risk of PJI. The addition of teicoplanin was associated with a lower risk of infection (HR, 0.35; 95% CI, 0.17 to 0.74). In conclusion, the addition of teicoplanin to cefuroxime during primary arthroplasty was associated with a significant reduction in the global PJI rate due to a reduction of infections caused by Gram-positive bacteria.
Novel Strategy for Biofilm Inhibition by Using Small Molecules Targeting Molecular Chaperone DnaK
Authors: Arita-Morioka Ken-ichi , Yamanaka Kunitoshi , Mizunoe Yoshimitsu , Ogura Teru , Sugimoto Shinya
Published: November 2014

Biofilms are complex communities of microorganisms that attach to surfaces and are embedded in a self-produced extracellular matrix. Since these cells acquire increased tolerance against antimicrobial agents and host immune systems, biofilm-associated infectious diseases tend to become chronic. We show here that the molecular chaperone DnaK is important for biofilm formation and that chemical inhibition of DnaK cellular functions is effective in preventing biofilm development. Genetic, microbial, and microscopic analyses revealed that deletion of the
dnaK
gene markedly reduced the production of the extracellular functional amyloid curli, which contributes to the robustness of
Escherichia coli
biofilms. We tested the ability of DnaK inhibitors myricetin (Myr), telmisartan, pancuronium bromide, and zafirlukast to prevent biofilm formation of
E. coli
. Only Myr, a flavonol widely distributed in plants, inhibited biofilm formation in a concentration-dependent manner (50% inhibitory concentration [IC
50
] = 46.2 μM); however, it did not affect growth. Transmission electron microscopy demonstrated that Myr inhibited the production of curli. Phenotypic analyses of thermosensitivity, cell division, intracellular level of RNA polymerase sigma factor RpoH, and vulnerability to vancomycin revealed that Myr altered the phenotype of
E. coli
wild-type cells to make them resemble those of the isogenic
dnaK
deletion mutant, indicating that Myr inhibits cellular functions of DnaK. These findings provide insights into the significance of DnaK in curli-dependent biofilm formation and indicate that DnaK is an ideal target for antibiofilm drugs.
Critical Roles of Clostridium difficile Toxin B Enzymatic Activities in Pathogenesis
Authors: Li Shan , Shi Lianfa , Yang Zhiyong , Zhang Yongrong , Perez-Cordon Gregorio , Huang Tuxiong , Ramsey Jeremy , Oezguen Numan , Savidge Tor C. , Feng Hanping
Published: November 2014

TcdB is one of the key virulence factors of
Clostridium difficile
that is responsible for causing serious and potentially fatal colitis. The toxin contains at least two enzymatic domains: an effector glucosyltransferase domain for inactivating host Rho GTPases and a cysteine protease domain for the delivery of the effector domain into host cytosol. Here, we describe a novel intrabody approach to examine the role of these enzymes of TcdB in cellular intoxication. By screening a single-domain heavy chain (V
H
H) library raised against TcdB, we identified two V
H
H antibodies, 7F and E3, that specifically inhibit TcdB cysteine protease and glucosyltransferase activities, respectively. Cytoplasmic expression of 7F intrabody in Vero cells inhibited TcdB autoprocessing and delayed cellular intoxication, whereas E3 intrabody completely blocked the cytopathic effects of TcdB holotoxin. These data also demonstrate for the first time that toxin autoprocessing occurs after cysteine protease and glucosyltransferase domains translocate into the cytosol of target cells. We further determined the role of the enzymatic activities of TcdB in
in vivo
toxicity using a sensitive systemic challenge model in mice. Consistent with these
in vitro
results, a cysteine protease noncleavable mutant, TcdB-L543A, delayed toxicity in mice, whereas glycosyltransferase-deficient TcdB demonstrated no toxicity up to 500-fold of the 50% lethal dose (LD
50
) when it was injected systemically. Thus, glucosyltransferase but not cysteine protease activity is critical for TcdB-mediated cytopathic effects and TcdB systemic toxicity, highlighting the importance of targeting toxin glucosyltransferase activity for future therapy.
Myeloid-Derived Suppressor Cells Impair Alveolar Macrophages through PD-1 Receptor Ligation during Pneumocystis Pneumonia
Authors: Lei Guang-Sheng , Zhang Chen , Lee Chao-Hung
Published: November 2014

Myeloid-derived suppressor cells (MDSCs) were recently found to accumulate in the lungs during
Pneumocystis
pneumonia (PcP). Adoptive transfer of these cells caused lung damage in recipient mice, suggesting that MDSC accumulation is a mechanism of pathogenesis in PcP. In this study, the phagocytic activity of alveolar macrophages (AMs) was found to decrease by 40% when they were incubated with MDSCs from
Pneumocystis
-infected mice compared to those incubated with Gr-1
+
cells from the bone marrow of uninfected mice. The expression of the PU.1 gene in AMs incubated with MDSCs also was decreased. This PU.1 downregulation was due mainly to decreased histone 3 acetylation and increased DNA methylation caused by MDSCs. MDSCs were found to express high levels of PD-L1, and alveolar macrophages (AMs) were found to express high levels of PD-1 during PcP. Furthermore, PD-1 expression in AMs from uninfected mice was increased by 18-fold when they were incubated with MDSCs compared to those incubated with Gr-1
+
cells from the bone marrow of uninfected mice. The adverse effects of MDSCs on AMs were diminished when the MDSCs were pretreated with anti-PD-L1 antibody, suggesting that MDSCs disable AMs through PD-1/PD-L1 ligation during PcP.
bis
-Molybdopterin Guanine Dinucleotide Is Required for Persistence of Mycobacterium tuberculosis in Guinea Pigs
Authors: Williams Monique J. , Shanley Crystal A. , Zilavy Andrew , Peixoto Blas , Manca Claudia , Kaplan Gilla , Orme Ian M. , Mizrahi Valerie , Kana Bavesh D.
Published: November 2014

Mycobacterium tuberculosis
is able to synthesize molybdopterin cofactor (MoCo), which is utilized by numerous enzymes that catalyze redox reactions in carbon, nitrogen, and sulfur metabolism. In bacteria, MoCo is further modified through the activity of a guanylyltransferase, MobA, which converts MoCo to
bis
-molybdopterin guanine dinucleotide (
bis
-MGD), a form of the cofactor that is required by the dimethylsulfoxide (DMSO) reductase family of enzymes, which includes the nitrate reductase NarGHI. In this study, the functionality of the
mobA
homolog in
M. tuberculosis
was confirmed by demonstrating the loss of assimilatory and respiratory nitrate reductase activity in a
mobA
deletion mutant. This mutant displayed no survival defects in human monocytes or mouse lungs but failed to persist in the lungs of guinea pigs. These results implicate one or more
bis
-MGD-dependent enzymes in the persistence of
M. tuberculosis
in guinea pig lungs and underscore the applicability of this animal model for assessing the role of molybdoenzymes in this pathogen.
Escherichia coli SecG Is Required for Residual Export Mediated by Mutant Signal Sequences and for SecY-SecE Complex Stability
Authors: Belin Dominique , Plaia Giuseppe , Boulfekhar Yasmine , Silva Filo
Published: November 2014

Protein export to the bacterial periplasm is achieved by SecYEG, an inner membrane heterotrimer. SecY and SecE are encoded by essential genes, while SecG is not essential for growth under standard laboratory conditions. Using a quantitative and sensitive export assay, we show that SecG plays a critical role for the residual export mediated by mutant signal sequences; the magnitude of this effect is not proportional to the strength of the export defect. In contrast, export mediated by wild-type signal sequences is only barely retarded in the absence of SecG. When probed with mutant signal sequences,secGloss of function mutations display a phenotype opposite to that ofprlAmutations insecY. The analysis ofsecGandprlAsingle and double mutant strains shows that the increased export conferred by severalprlAalleles is enhanced in the absence of SecG. Several combinations ofprlAalleles with asecGdeletion cannot be easily constructed. This synthetic phenotype is conditional, indicating that cells can adapt to the presence of both alleles. The biochemical basis of this phenomenon is linked to the stability of the SecYE dimer in solubilized membranes. WithprlAalleles that can be normally introduced in asecGdeletion strain, SecG has only a limited effect on the stability of the SecYE dimer. With the otherprlAalleles, the SecYE dimer can often be detected only in the presence of SecG. A possible role for the maintenance of SecG during evolution is proposed.
Impact of Spontaneous Prophage Induction on the Fitness of Bacterial Populations and Host-Microbe Interactions
Authors: Nanda Arun M. , Thormann Kai , Frunzke Julia
Published: November 2014

Bacteriophages and genetic elements, such as prophage-like elements, pathogenicity islands, and phage morons, make up a considerable amount of bacterial genomes. Their transfer and subsequent activity within the host's genetic circuitry have had a significant impact on bacterial evolution. In this review, we consider what underlying mechanisms might cause the spontaneous activity of lysogenic phages in single bacterial cells and how the spontaneous induction of prophages can lead to competitive advantages for and influence the lifestyle of bacterial populations or the virulence of pathogenic strains.