bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of Stroke Recurrence According to Subtype of First Stroke Event: The North East Melbourne Stroke Incidence Study (NEMESIS)
Authors: Azarpazhooh Mahmoud Reza , Nicol Marcus B. , Donnan Geoffrey A. , Dewey Helen M. , Sturm Jonathan W. , Macdonell Richard A. L. , Pearce Dora C. , Thrift Amanda G.
Published: August 2008

Background

Specific information about the nature of recurrent events that occur after each subtype of index stroke may be useful for refining preventive therapies. We aimed to determine whether stroke recurrence rates, the pattern of subtype recurrence, and prescription of secondary prevention agents differed according to initial stroke subtype.

Methods

Multiple overlapping sources were used to recruit all first-ever stroke patients from a geographically defined region of Melbourne, Australia over a 3-year period from 1996 to 1999. Potential stroke recurrences (fatal and nonfatal) occurring within 2 years of the initial event were identified following patient interview and follow up of death records. Subjects were classified into the different Oxfordshire groups and the type of first-ever stroke was compared with recurrent stroke events.

Results

One thousand, three hundred and sixteen first-ever strokes were registered during the 3-year period (mean age 74·4 years). A total of 103 first recurrent stroke events (fatal and nonfatal) occurred among those with a first-ever ischemic stroke or intracerebral hemorrhage (ICH) during the 2-year follow-up period. The recurrent stroke subtype was different to the index stroke subtype in most (78%) patients. People with partial anterior circulation infarct had the greatest proportion of recurrences (13%), with a third of these being the more severe total anterior circulation infarct subgroup. The relative risk of ICH after an index lacunar infarct (LACI) compared with an index non-LACI was 4·06 (95% CI 1·10–14·97, P=0·038). Prescription of secondary prevention agents was greater at 2 years after stroke than at hospital discharge, and was similar between ischemic stroke subtypes.

Conclusion

Approximately 9% of people with first-ever stroke suffered a recurrent event, despite many being prescribed secondary prevention agents. This has implications for the uptake of current preventive strategies and the development of new strategies. The possibility that ICH is greater among index LACI cases needs to be confirmed.
Impact of the leaner P/Q‐type Ca2+ channel mutation on excitatory synaptic transmission in cerebellar Purkinje cells
Authors: Liu Shaolin , Friel David D.
Published: August 2008

Loss‐of‐function mutations in the gene encoding P/Q‐type Ca2+ channels cause cerebellar ataxia in mice and humans, but the underlying mechanism(s) are unknown. These Ca2+ channels play important roles in regulating both synaptic transmission and intrinsic membrane properties, and defects in either could contribute to ataxia. Our previous work described changes in intrinsic properties and excitability of cerebellar Purkinje cells (PCs) resulting from the leaner mutation, which is known to reduce whole‐cell Ca2+ currents in PCs and cause severe ataxia. Here we describe the impact of this mutation on excitatory synaptic transmission from parallel and climbing fibres (PFs, CFs) to PCs in acute cerebellar slices. We found that in leaner PCs, PF‐evoked excitatory postsynaptic currents (PF‐EPSCs) are ∼50% smaller, and CF‐evoked EPSCs are ∼80% larger, than in wild‐type (WT) mice. To investigate whether reduced presynaptic Ca2+ entry plays a role in attenuating PF‐EPSCs in leaner mice, we examined paired‐pulse facilitation (PPF). We found that PPF is enhanced in leaner, suggesting that reduced presynaptic Ca2+ entry reduces neurotransmitter release at these synapses. Short‐term plasticity was unchanged at CF–PC synapses, suggesting that CF‐EPSCs are larger in leaner PCs because of increased synapse number or postsynaptic sensitivity, rather than enhanced presynaptic Ca2+ entry. To investigate the functional impact of the observed EPSC changes, we also compared excitatory postsynaptic potentials (EPSPs) elicited by PF and CF stimulation in WT and leaner PCs. Importantly, we found that despite pronounced changes in PF‐ and CF‐EPSCs, evoked EPSPs in leaner mice are very similar to those observed in WT animals. These results suggest that changes in synaptic currents and intrinsic properties of PCs produced by the leaner mutation together maintain PC responsiveness to excitatory synaptic inputs. They also implicate other consequences of the leaner mutation as causes of abnormal cerebellar motor control in mutant mice.
Theta burst stimulation induces after‐effects on contralateral primary motor cortex excitability in humans
Authors: Suppa A. , Ortu E. , Zafar N. , Deriu F. , Paulus W. , Berardelli A. , Rothwell J. C.
Published: August 2008

Interhemispheric interactions between the primary motor cortices (M1) have been described with a variety of TMS methods. Here we give a detailed description of the interhemispheric interactions of a period of theta burst simulation (TBS), a rapid method of producing long lasting after‐effects on the excitability of the stimulated M1. A total of 18 right handed healthy subjects participated. In most experiments, continuous and intermittent TBS (cTBS and iTBS) were delivered over the right M1 using a coil orientated to induce antero‐posterior followed by postero‐anterior (AP–PA) currents in the brain. The intensity of stimulation was 80% of active motor threshold (AMT), and a total of 600 pulses were applied. The effects on the amplitude of motor evoked potentials (MEPs), short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were evaluated in the left and right M1 before and at three different times after TBS. We also tested long‐interval intracortical inhibition (LICI) in right M1 and interhemispheric inhibition (IHI) from right to left M1. Finally, to explore the effect of different polarities of cTBS over dominant and non‐dominant hemisphere we delivered AP–PA and postero‐anterior followed by antero‐posterior (PA–AP) cTBS over either right or left M1 and tested MEPs in both hemispheres. In the stimulated hemisphere, cTBS reduced MEPs and SICI whereas iTBS increased MEPs and SICI. In the non‐stimulated hemisphere cTBS increased MEPs and reduced SICI, while iTBS reduced MEPs and increased SICI. There were no effects on ICF, LICI or IHI. Although both AP–PA cTBS and PA–AP cTBS reduced MEPs in the stimulated M1, the former increased MEPs from non‐stimulated M1 whereas the latter did not. There was no difference in the effect of cTBS on the dominant or non‐dominant hemisphere.
AICAR activates AMPK and alters PIP2 association with the epithelial sodium channel ENaC to inhibit Na+ transport in H441 lung epithelial cells
Authors: Mace Oliver J. , Woollhead Alison M. , Baines Deborah L.
Published: August 2008

Changes in amiloride‐sensitive epithelial Na+ channel (ENaC) activity (NPo) in the lung lead to pathologies associated with dysregulation of lung fluid balance. UTP activation of purinergic receptors and hydrolysis of PIP2 via activation of phospholipase C (PLC) or AICAR activation of AMP‐activated protein kinase (AMPK) inhibited amiloride‐sensitive Na+ transport across human H441 epithelial cell monolayers. Neither treatment altered α, β or γ ENaC subunit abundance (N) in the apical membrane indicating that the mechanism of inhibition was via a change in channel open state probability (Po). We found that UTP depleted PIP2 abundance in the apical membrane whilst activation of AMPK prevented the binding of β and γ ENaC subunits to PIP2. The association of PIP2 with the ENaC subunits is required to maintain channel activity via Po. Thus, these data show for the first time that AICAR activation of AMPK inhibits Na+ transport via a mechanism that perturbs the PIP2–ENaC channel interaction to alter Po. In addition, we show that dissociation of PIP2 from ENaC together with activation of AMPK further reduced Na+ transport by a secondary effect that correlated with ENaC subunit internalization. Thus, when PIP2–ENaC subunit interactions were compromised, ENaC protein retrieval was initiated, indicating that AMPK can modulate ENaC Po and N.
Effects of Deposits on Film Cooling of a Vane Endwall Along the Pressure Side
Authors: Sundaram N. , Barringer M. D. , Thole K. A.
Published: August 2008

Film cooling is influenced by surface roughness and depositions that occur from contaminants present in the hot gas path, whether that film cooling occurs on the vane itself or on the endwalls associated with the vanes. Secondary flows in the endwall region also affect the film-cooling performance along the endwall. An experimental investigation was conducted to study the effect of surface deposition on film cooling along the pressure side of a first-stage turbine vane endwall. A large-scale wind tunnel with a turbine vane cascade was used to perform the experiments. The vane endwall was cooled by an array of film-cooling holes along the pressure side of the airfoil. Deposits having a semielliptical shape were placed along the pressure side to simulate individual row and multiple row depositions. Results indicated that the deposits lowered the average adiabatic effectiveness levels downstream of the film-cooling rows by deflecting the coolant jets toward the vane endwall junction on the pressure side. Results also indicated that there was a steady decrease in adiabatic effectiveness levels with a sequential increase in the number of rows with the deposits.
Overview of the New B&PV Code Section XII Transport Tank Rules
Authors: Becht Charles
Published: August 2008

The first edition of Section XII, “Rules for Construction and Continued Service of Transport Tanks,” was issued with the 2004 edition of the ASME Boiler and Pressure Vessel Code. Transport tanks are pressure vessels used for the transportation of dangerous goods via highway, rail, air or water. This paper provides an overview of the requirements of Section XII.
Experimental Tests of Longitudinal Added Damping and Stiffness Device
Authors: Tsai C. S. , Lee Guan-Hsing , Chen Wen-Shin , Hsu Li-Te
Published: August 2008

Structural passive control technology has been developed rapidly over the past decade, and proven as a feasible and promising way in mitigating the seismic response of a structure. In numerous passive control devices, the added damping and stiffness (ADAS) has been verified as an effective and economical energy-absorbing device to dissipate the seismic energy. Successful applications have also been achieved in Taiwan. A new device named as the longitudinal added damping and stiffness (LADAS) has been developed in this study. The component test shows that the LADAS device can sustain an extremely large number of yielding reversals without any sign of stiffness or strength degradation and has stable energy-dissipating capability. The comparison of analytical and experimental results illustrates that the Wen’s model in an incremental form could successfully predict the hysteretic behavior of LADAS device. Moreover, the earthquake proof efficiency of the LADAS was carried out on a scaled-down three steel frame on a shaking table in Feng Chia University, Taichung, Taiwan. The experiment result demonstrates that a structure with LADASs can significantly reduce the seismic response.
Application of Models for Laminar to Turbulent Transition to Flow Around a Circular Cylinder
Authors: Reichel Christoph , Strohmeier Klaus
Published: August 2008

In many technical fields, for example heat exchangers, circular cylinders are involved in Fluid Structure Interaction (FSI) problems. Therefore correct fluid forces or Strouhal number, drag and fluctuating lift coefficient are needed. On one hand Direct Numerical Simulation (DNS) or Large Eddy Simulation (LES) are too time-expensive, on the other hand great errors can occur, if fluid forces are evaluated with mainstream statistical turbulence models. An incorrect prediction of laminar to turbulent transition and correspondingly a miscalculation of the separation point is the main reason. Several turbulence models and models for laminar to turbulent transition are applied to flow around a circular cylinder in the Reynolds number range from 500 up to 106. Mainly 2D simulations demonstrate the large improvements that are possible with transition models. Additionally calculations are presented to evaluate whether the class of statistical turbulence and transition models is influenced by three dimensional modeling. Results will be presented for the Shear Stress Transport (SST) and the Wilcox98 k-ω turbulence model. While the latter can be modified according to a proposal of Wilcox (1998) to take transition into account, the commercial code we use at our institute provides several extensions for transition modeling together with the SST model.
Computational Studies for the Exhausted Flue Gas
Authors: Ferreira V. C. S. , Cordeiro C. S. S. M. , Kaehler J. W.
Published: August 2008

Pulverized coal with low average heating, producing ashes with high percentage of silica, is fired inside the furnaces of a Thermal Power Plant (TPP) of Candiota, State of Rio Grande do Sul, Brazil. The produced hot flue gas heats the water of the ECONOMIZER 01 (ECO 01) placed inside the exhausted duct. Distorted velocity profile at inlet of ECO 01 and high concentration of abrasive particles of flue gas cause drastic erosion. So intensive has been the abrasive action that some well-identified tubes end up collapsing. The unpredictable fail has caused many non-scheduled stops of the TPP. A study focused on the reduction this effect, was set up years ago. The paper shows part of this study end present results, obtained from the numerical simulation analysis of the flue gas flow. Some technical solutions are suggested to reduce the erosion of tubes providing that avoiding it showed be impossible.
Determine Weight of Hot Metal Car Using Strain Gage Method
Authors: Reichard Duane E. , Krompegel Sean P. , Reichard James E. , Shields Elvin B.
Published: August 2008

In certain situations, train car containers that carry hot metal have been overfilled, which necessitated the replacement of very costly car parts. Therefore, it is desirable to predict the amount of fluid needed at all times in order to know when to divert the flow of molten steel from the car. This study showed that the level of fluid in a container can be controlled even when the amount of fluid inside the container is not visible. When strain gages are effectively installed they can be used to continuously calculate the weight of a system as the strain increases, although only the final total weight is of concern. Strain gages can be positioned in safe locations on the spanner bolster of a hot metal car. The gages are installed such that the thermal and axial strains cancel out, ultimately leaving only the value for the weight of the loaded car. Once the gages are installed, they are calibrated when the system is full. For all subsequent loading periods, the strain gages report a linear strain increasing until it is equal to the original full calibration value. This then signals the operator to divert the flow of steel. If the inside of the container deteriorates over time, the strain that governs the shutoff remains the same although the fluid level is slightly lower. In the event of skull (leftover steel in the container), the maximum strain remains the same and the final volume is lower than the initial calibration condition. The objective in all cases is to avoid overflow of fluid from the car. This investigation showed that the amount of fluid in a train car that carries molten steel can be known at all times during the filling process. It is supported with manual calculations, finite element analyses, and laboratory experiments.
Re-Rating of Piping and Pressure Vessels Using API 579 Section 3
Authors: Sreedhar S. L.
Published: August 2008

As data on actual failures of metals, becomes available from various industries, advances are made in understanding behaviour of materials under different conditions. This leads to refinement of published characteristics for materials in general. Further, changes in manufacturing technology, improved measurement techniques and analytical capabilities of software, all contribute in their own way in defining boundaries for a broad category of materials. This manifests itself in a challenge for design engineers to continue to let some chemical processes operate in their normal range using existing equipment that needs to be re-rated based on improved understanding. One such example is the minimum temperature limit, without impact testing, for ordinary carbon steels that has been revised upwards in recent years. This has resulted in rendering piping systems and pressure vessels unsuitable for low temperature conditions that they might have been certified for based on earlier knowledge and Standards. This challenge can be dealt with in a number of different ways by revisiting both process and mechanical design variables. This paper/presentation discusses the approach adopted by Santos for their gas processing plant at Moomba, to review and adjust the process in light of latest knowledge on resistance to brittle failure.
Status of the Development of a New Standard: Repair of Pressure Equipment and Piping
Authors: Becht Charles
Published: August 2008

A new ASME standard is in preparation, the title of which is Repair of Pressure Equipment and Piping. It covers methods of repair of equipment such as pressure vessels, heat exchangers, boilers, piping and piping components and tankage. The paper describes the intent of this new standard and its present status.
Anodic Behavior of Specimens Prepared From a Full-Diameter Alloy 22 Fabricated Container for Nuclear Waste
Authors: King Kenneth J. , Estill John C. , Rebak Rau´l B.
Published: August 2008

Alloy 22 (N06022) has been extensively tested for general and localized corrosion behavior both in the wrought and annealed condition and in the as-welded condition. The specimens for testing were mostly prepared from flat plates of material. It was important to determine if the process of fabricating a full diameter Alloy 22 container will affect the corrosion performance of the alloy. Specimens were prepared directly from a fabricated container and tested for corrosion resistance. Results show that both the anodic corrosion behavior and the localized corrosion resistance of specimens prepared from a welded fabricated container was the same as from flat welded plates.
Fatigue Reliability Based Optimal Replacement Decision Based on First Order Reliability Method
Authors: Tang Jun , Hardee Edwin , Park Young H.
Published: August 2008

This paper introduces a maintenance decision-making strategy in the general area of the replacement and reliability of mechanical components. The decision-making strategy involves the optimization of the replacement interval based on fatigue failure of mechanical components. Fatigue reliabilities of a component under random cyclic loading need to be evaluated to determine the optimal replacement intervals under fatigue failure. This task is undertaken by determining a reliability factor using an inverse reliability analysis. A reliability-defined ε-N curve (R-ε-Nf curve) can be generated for an empirical ε-N relationship and a “unique” reliability factor by modifying the nominal ε-Nf curve using reliability factors for an assigned reliability. A family of R-ε-Nf curves, which includes the conventional ε-Nf curve, can then be obtained. Hence, fatigue life under specified reliability or reliability based on mission life can be predicted using these curves. This method can efficiently determine replacement intervals for components whose operating costs increase with use and replacement intervals for components subject to failure induced by random process. An example is presented to demonstrate the application of the present method.
Damage to Floating Roof Tank by Sloshing
Authors: Kikuchi Tsutomu , Miura Masahiro
Published: August 2008

The Tokachi-oki Earthquake, a magnitude 8 big earthquake, occurred on September 26, 2003. At the Hokkaido Refinery of Idemitsu Kosan Co. Ltd. In Tomakomai, a peak acceleration of the seismic ground motion was recorded at 86 gal (resultant value). This ground motion was predominated by slightly long periods lasting 3 to 8 seconds that harmonized with the natural period of the tanks, causing significant sloshing and subsequent damages of floating roof tanks (FRT).
The Energy Approach of EPFM Applied to the Analysis of a WPS Experiment on a Cracked Cylinder
Authors: Wadier Yves , Bonnamy M.
Published: August 2008

This document presents the energy approach of elastic-plastic fracture mechanics applied to the analysis of a “warm pre-stress” test on a cylinder made of a 17MoV84mod. steel, artificially degraded by special heat treatment to simulate an irradiated end of life RPV material and submitted to a mechanical loading close to a thermal shock transient. This test has been conducted at the MPA of Stuttgart in the context of the European project SMILE. The influence of the hardening representation (isotropic, kinematics, etc.) as well as the choice of the toughness values of the material are analysed. The numerical analysis was performed at EDF-R&D with the Code-Aster, the finite element code of EDF. First of all, we have identified the critical value Gpc of the Gp parameter at the temperature of failure (T = 35°C). Then we have applied the energy approach and compared the results obtained to experimental one’s. Concerning the global values, the agreement between the results of calculation and the experimental results is good if we consider the values of temperature or COD as well as the values of KJ. Concerning the local values, we have observed a rapid decreasing of the opening stress at the notch tip and a significant influence of the hardening on the Von Mises stress. The curves giving the fracture probability as function of KJ are quite relevant to estimate the predictive capacity of the approach used, as well as the importance of the choice of hardening. We have pointed out a 15% variation of KJ depending on this choice. Using tests on CT specimens at room temperature in order to identify the critical value Gpc of the Gp parameter, the value of 77.7 MPa.m1/2 is obtained for KJ if we consider the kinematics case, at 95% of fracture probability. This value is the highest and the nearest to the experimental value equal to 90 MPa.m1/2. It is not a proof that the hardening is completely kinematics but it leads to the question of a more complete identification of the material to know what is the isotropic part and the kinematics part in the hardening. Besides, because the difference between the result obtained with the energy approach and the experimental result is equal to 14% we can conclude to a satisfactory predictive capacity of this approach. The “warm pre-stress” effect, associated with a significant increase of the cleavage fracture toughness at low temperature after a pre-loading at a higher temperature, is clearly predicted by using the energy approach. The comparison between the results obtained with the different approaches used (energy approach, Beremin model, etc.) will be made in another paper. This work is performed in the context of the SMILE European Project.
Thermal Fatigue Evaluation Method Based on Power Spectrum Density Functions Against Fluid Temperature Fluctuation
Authors: Kasahara Naoto , Kimura Nobuyuki , Kamide Hideki
Published: August 2008

Fluid temperature fluctuates at an incomplete mixing area of high and low temperature fluids in nuclear components. It induces random variations of local temperature gradients in structural walls, which lead to cyclic thermal stresses. When thermal stresses and cycle numbers are large, there are possibilities of fatigue crack initiations and propagations. It is recognized that there are attenuation factors depending on fluctuation frequency in the transfer process from fluid temperature to thermal stresses. If a frequency of fluctuation is very low, whole temperature of the wall can respond to fluid temperature, because thermal diffusivity homogenizes structural temperature. Therefore, low frequency fluctuations do not induce large thermal stress due to temperature gradients in structures. On the other hand, a wall surface cannot respond to very high frequency fluctuation, since a structure has a time constant of thermal response. High frequency fluctuations do not lead to large thermal stress. Paying attention to its attenuation mechanism, Japan Nuclear Cycle Development Institute (JNC) has proposed a fatigue evaluation method related to frequencies. The first step of this method is an evaluation of Power Spectrum Density (PSD) on fluid, from design specifications such as flow rates, diameters of pipes and materials. In the next step, the PSD of fluid is converted to PSD of thermal stress by the frequency transfer function. Finally, the PSD of thermal stress is transformed to time history of stress under an assumption of random phase. Fatigue damage factors can be evaluated from stress ranges and cycles obtained by the rain flow wave count method. Proposed method was applied to evaluate fatigue damage of piping junction model tests conducted at Oarai Engineering Center. Through comparison with direct evaluation from measurements and predictions by conventional methods, the accuracy of the proposed method was validated.
Introduction of the Element Interaction Technique for Welding Analysis and Simulation
Authors: Fanous Ihab F. Z. , Younan Maher Y. A. , Wifi Abdalla S.
Published: August 2008

The residual stresses generated due to welding in pressure components may have several harmful effects such as decrease in the resistance to cycling load and corrosive environments. The analysis of the welding process has been developed extensively in 2D and 3D. The element movement technique has been shown to be very effective in simulating the filler material deposition leading to a reduction in the analysis time. However, when attempted for wider fields of applications, it had some limitations, especially when moving the elements towards the base-plate. In this paper, the element interaction technique is introduced utilizing the concepts of both the element movement and element birth techniques. The new technique is verified versus the currently developed procedures. In this technique, the elements of the weld pool are held in place in contact with the elements of the base-plate and the interaction is made to be a function of time. This gave several flexibilities in modeling the welding process. Hence, the technique is then used to analyze simple fillet welding of a plate and circumferential butt-welding of a pipe.
Comparison of Reference Temperature T0 From Instability KJC and KIC Fracture Toughness
Authors: Siegele Dieter , Keim Elisabeth , Nagel Gerhard
Published: August 2008

The application of the reference temperatures T0 and RTTo according to ASTM E 1921 and ASME Code Cases N-629 or N-631, respectively, shall be established in the current revision of German KTA rules. The Master Curve reference temperature T0 characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at elastic, or elastic-plastic KJC-instabilities, or both. The plane-strain fracture toughness, KIC, defined by ASTM E 399, is assumed to represent a size insensitive initiation based lower bound value. The majority of existing fracture toughness data are based on KIC-values. More recent data are KJC, related to the issuing of ASTM E 1921 in 1997 and to the success of the Master Curve based T0. Therefore, the possible difference between T0 determined from KJC and from KIC was investigated with available data bases for RPV-steels. The comparison of T0(KJC) and T0(KIC) showed a 1:1 correlation proving equivalence of KJC and KIC in the determination of T0.
Numerical Modeling of Metallic Systems Submitted to Dynamic Solicitation
Authors: Daudonnet Benjamin , Mercier Fre´de´ric M. B. , Woznica Krzysztof
Published: August 2008

The rupture phenomenon can be considered through different angles: some researches are solely dedicated to the mechanical aspects (deformations, damage, crack initiation and propagation), while others consider it only through thermodynamics or fluid mechanics (depressurization and fluid behavior). Few studies investigate all the different aspects of the phenomenon, although all of them are involved in the failure of pressurized metallic vessels. This paper presents approaches and models that describe the different part of the rupture. On this base models were developed. Simulations results are then compared with experimental ones.
Numerical Simulation of Sample Scale Intense Shear Bands in Uniaxial Tension Test of Aluminum Alloys
Authors: Metzger Don R. , Duan Xinjian , Jain Mukesh
Published: August 2008

The present work focuses on the study of the development of shear localization through the use of the conventional finite element method which does not involve the non-associative flow rule, yield surface vertex or void growth model. The various aspects, i.e. geometry idealization, element type, solution procedure, convergence, and particularly the representation of true-stress and plastic strain relationship, are emphasized. The predicted profile of the deformed specimen, shear band angle and strain distribution show an excellent agreement with experimental observations.
Effect of Local Wall Thinning on the Dynamic Behavior of Piping Systems
Authors: Nakamura Izumi , Otani Akihito , Shiratori Masaki
Published: August 2008

In order to investigate the influence of degradation on dynamic behavior and the failure mode of piping systems with local wall thinning, shake table tests using 3-D piping system models were conducted. The degradation considered in this study was wall thinning, which would be caused in piping systems due to the effects of aging. The degradation condition induced in the piping system model was 50% full circumferential wall thinning at an elbow. The test model was designed to cause out-of-plane bending moment to the thinned-wall elbow by excitation tests. The model without wall thinning was also used in the excitation test to compare the behavior of the piping system models. These models were excited under same input acceleration until fatigue cracks penetrated or an excessive deformation occurred to the models. Through these tests, the vibration characteristic and the process to failure of degraded piping models were obtained for the out-of-plane bending model. This paper describes the dynamic response and failure behavior of piping systems with wall thinning based on the test results.
Cyclic Performance of Two-Story Ductile RC Frames With Infill Walls
Authors: Yeh Yung-Hsin , Liao Wen-I
Published: August 2008

This paper presents the results of the experimental and analytical investigations conducted on four 0.8 scale 2-story one bay ductile reinforced concrete frames with infill nonstructural walls subjected to cyclically increasing loads. The material properties and the member sizes of beams and columns in the four RC frame specimens are identical, but with different types of infill nonstructural wall. These four frames are the pure frame, frame with short column, frame with short beam and frame with wing walls. The four RC frame specimens were designed and constructed according to the general prototype building structures in Taiwan. Test results indicate that the ductility behavior of the frames with infill wall is similar to those of the pure frame. The ultimate base shear strength of the frames with infill walls is higher than those of the pure frame. Analytical results show that the proposed simplified multi-linear beam-column element implemented in a general purpose structural analysis program can accurately simulate the cyclic responses of the RC frame specimen incorporating the elastic flexural stiffness computations suggested by the model building codes.
Effect of Material Properties on Welding Distortion History
Authors: Mochizuki Masahito , Mikami Yoshiki , Morikage Yasushi , Toyoda Masao
Published: August 2008

Welding distortion of a T-joint is calculated numerically considering the effect of phase transformation. Welding distortion becomes smaller in the case of a T-joint with developed low-transformation temperature welding wire than with conventional wire, which has been produced for high accuracy fabrication. Results of weld distortion history by numerical simulation agree well with those by the measurement during the whole weld process. The effect of material properties such as martensitic transformation temperature on welding distortion is investigated by using numerical simulation.
On the Underlying Fluid Mechanics Responsible for Damping Controlled Fluidelastic Instability in Tube Arrays
Authors: Meskell Craig
Published: August 2008

Granger and Paidoussis hypothesized that damping controlled fluidelastic instability is in fact due to the generation and convection of vorticity. In this paper a simple wake model consisting of a convecting vortex sheet is proposed to represent the transient nature of fluidelastic forces present in a tube array. Using this model, the memory function proposed by Granger and Paidoussis has been obtained by numerical integration without the need to calibrate the model with experimental data. The resulting function is found to compare well with the first and second order approximations which were determined empirically. However, the current model does not exhibit the physically unrealistic features of the approximations. Furthermore, the memory function has been combined with experimental data for the static fluid force to produce a prediction of the critical velocity for a range of mass damping parameter. This stability threshold is in reasonable agreement with experimental data. Therefore it is concluded that vorticity transport is in fact the mechanism responsible for damping controlled fluidelastic instability.
FIV Characteristics of U-Tubes Due to Relocation of the Tube Support Plate
Authors: Ryu Ki-Wahn , Kim Hyung-Jin , Park Chi-Yong
Published: August 2008

Fluid-elastic instability and turbulence excitation for an under developing steam generator are investigated numerically. The stability ratio and the amplitude of turbulence excitation are obtained by using the PIAT (Program for Integrity Assessment of Steam Generator Tube) code from the information on the thermal-hydraulic data of the steam generator. The aspect ratio, the ratio between the height of U-tube from the upper most tube support plate (h) and the width of two vertical portion of U-tube (w), is defined for geometric parameter study. Several aspect ratios with relocation of tube support plates are adopted to study the effects on the mode shapes and characteristics of flow-induced vibration. When the aspect ratio exceeds value of 1, most of the mode shapes at low frequency are generated at the top of U-tube. It makes very high value of the stability ratio and the amplitude of turbulent excitation as well. We can consider that the local mode shape at the upper side of U-tube will develop the wear phenomena between the tube and the anti-vibration bars such as vertical, horizontal, and diagonal strips. It turns out that the aspect ratio reveals very important parameter for the design stage of the steam generator. The appropriate value of the aspect ratio should be specified and applied.
Second Phase Precipitation in As-Welded and Solution Annealed Alloy 22 Welds
Authors: El-Dasher Bassem S. , Torres Sharon G.
Published: August 2008

The precipitation characteristics of tetrahedrally close-packed (TCP) phases during the welding and the subsequent solution annealing process of Alloy 22 1 1/2” thick plate double-U prototypical welds are investigated. Electron backscatter diffraction (EBSD) was used to provide large scale microstructural observation of the weld cross section, and scanning electron microscopy (SEM) was used to map the location of the TCP phases. Analysis shows that TCP precipitation occurs congruent to the weld passes, with the solution annealing reducing the sizes of coarser precipitates.
Techniques for Modeling Thermal and Mechanical Stresses Generated in Catalytic Cracker and Coke Drum Hot Boxes
Authors: Alexander Chris , Boswell Richard
Published: August 2008

Consideration of heat transfer loading between surfaces during transient and steady state conditions is required when analyzing vessels that involve secondary stresses and low cycle fatigue. Some of the higher stresses occur in enclosed, non-insulated air space regions, referred to as a hot box, between a supporting skirt (or shell) and a vessel. Hot boxes are critical parts of vessel designs in catalytic crackers and delayed coke drums. In coke drum cycles, the sudden heating of the vessel generates significant bending stresses in the skirt, and radiation heat transfer causes a greater area of skirt to be heated when compared to conduction alone. This heat must be removed during the cooling transient or the hot expanded skirt will be pulled by the contracting vessel, resulting in large bending stresses. It is the experiences of the authors that failures to calculate the transient temperatures in the components often underestimate fatigue stresses. Some of the important elements associated with modeling thermal stresses in hot boxes include using appropriate boundary conditions, radiation and convection conditions, pressure end loads, and conductivities for the insulation materials. This paper emphasizes the importance of performing detailed sensitivity analyses when unknown thermal or mechanical loading conditions exist. Examples include the effects of convection properties within the hotbox and conditions associated with transient loads. Discussions are also provided on the potential geometric issues associated with the use of axisymmetric finite element models. Additionally, this paper discusses the importance of making field measurements to enhance modeling assumptions. Discussions will be provided on the best methods for acquiring field data and the techniques employed.
Selection of Tube Samples for Inservice Inspection of Steam Generator Tubes
Authors: Roussel Guy , Cizelj Leon
Published: August 2008

In Pressurized Water Reactors, a program of periodic inservice inspection of steam generator tubes is set up to monitor the integrity of the tubes. The inservice inspection is performed using nondestructive examination techniques, e.g., eddy current testing. Usually not all the tubes are inspected but the inspection is limited to a sample of tubes. Therefore, the objective of the inservice inspection is to provide reasonable insurance of steam generator tubing integrity. Consequently, the concern is the level of confidence that can be placed in the estimated knowledge about the whole population of the steam generator tubes from the information obtained from the examination of a sample. In replacement steam generators, the number of defective tubes is expected to be very low. The usual sample may then simply be too small to include a defective tube. Hence, the problem is the estimation of the number of defective tubes in the total population given that no defective tubes have been detected in a sample. Using the classical Bayesian method in inverse problem, the analytical estimation of the probability distribution of the number of defective tubes knowing that a random sample of tubes contains no defective tubes is first performed. Then a numerical application is carried out considering a noninformative flat prior distribution and, more specifically, the analytical expression of the estimator of the mean number of defective tubes in the whole population of the steam generator tubes is given. Some approximated analytical Bayesian estimations for other prior distributions are also given. Additionally, the calculations allow also to provide an answer to the question: when performing the inservice inspection of the steam generator tubes, is it sufficient to inspect a random sample from any steam generator or the inspection samples should be taken separately from each steam generator?
Effect of Hydrostatic Stress on Low Cycle Fatigue Life
Authors: Sakane Masao , Itoh Takamoto
Published: August 2008

This paper overviews the effect of hydrostatic stress on the static tensile stress-strain relationship, low cycle fatigue life, creep rupture time and creep-fatigue life at room and elevated temperatures. There was almost no influence of the hydrostatic stress on the tensile stress-strain relationship but the tensile ductility was increased by the hydrostatic stress. Small or little increase of fatigue life was observed by the superposition of the hydrostatic stress under a full reversed loading but a clear increase of fatigue life was found in a zero-to-tension loading. The hydrostatic stress significantly lowered the creep strain rate and elongated the creep rupture time. The hydrostatic stress also increased the creep-fatigue life under a full reversed loading.
Determination of Interfacial Fracture Toughness for Thin Film Coating Materials
Authors: Wang John Jy-An , Wright Ian G. , Lance Michael J. , Liu Ken C.
Published: August 2008

A material configuration of central importance in composite materials or in protective coating technology is a thin film of one material deposited onto a substrate of a different material. Fabrication of such a structure inevitably gives rise to stress in the film due to lattice mismatch, differing coefficient of thermal expansion, chemical reactions, or other physical effects. Therefore, in general, the weakest link in this composite system often resides at the interface between the thin film and substrate. In order to make multi-layered electronic devices and structural composites with long-term reliability, the fracture behavior of the material interfaces must be known. This project is intended to address the problems associated with interface fracture toughness evaluation and offers an innovative testing procedure for the determination of interface fracture toughness applicable to thin coating materials in general.
Evaluating Stress-Corrosion Cracking Susceptibility Using a Torsion Test
Authors: Bayles Robert A. , Singh Raman R. K. , Knight Steven P. , Wang Jy-An
Published: August 2008

A torsion test has been devised that provides for plane strain constraint in small specimens during fracture toughness testing. This method has been extended for stress-corrosion cracking and a simple torsion load frame has been built to provide for step loading of the specimens. This paper describes using the torsion technique to measure KISCC for aluminum alloy 7075 having two thermo-mechanical treatments.
Induced Pluripotent Stem Cells Generated from Patients with ALS Can Be Differentiated into Motor Neurons
Authors: Dimos John T. , Rodolfa Kit T. , Niakan Kathy K. , Weisenthal Laurin M. , Mitsumoto Hiroshi , Chung Wendy , Croft Gist F. , Saphier Genevieve , Leibel Rudy , Goland Robin , Wichterle Hynek , Henderson Christopher E. , Eggan Kevin
Published: August 2008

The generation of pluripotent stem cells from an individual patient would enable the large-scale production of the cell types affected by that patient's disease. These cells could in turn be used for disease modeling, drug discovery, and eventually autologous cell replacement therapies. Although recent studies have demonstrated the reprogramming of human fibroblasts to a pluripotent state, it remains unclear whether these induced pluripotent stem (iPS) cells can be produced directly from elderly patients with chronic disease. We have generated iPS cells from an 82-year-old woman diagnosed with a familial form of amyotrophic lateral sclerosis (ALS). These patient-specific iPS cells possess properties of embryonic stem cells and were successfully directed to differentiate into motor neurons, the cell type destroyed in ALS.
Serial Isolates of Persistent
Haemophilus influenzae
in Patients with Chronic Obstructive Pulmonary Disease Express Diminishing Quantities of the HMW1 and HMW2 Adhesins
Authors: Cholon Deborah M. , Cutter David , Richardson Stephen K. , Sethi Sanjay , Murphy Timothy F. , Look Dwight C. , St. Geme Joseph W.
Published: August 2008

In patients with chronic obstructive pulmonary disease (COPD), the lower respiratory tract is commonly colonized by bacterial pathogens, including nontypeable
Haemophilus influenzae
. The
H. influenzae
HMW1 and HMW2 adhesins are homologous proteins that promote bacterial adherence to respiratory epithelium and are the predominant targets of the host immune response. These adhesins undergo graded phase variation, controlled by the numbers of 7-bp repeats upstream of the HMW1 and HMW2 structural genes (
hmw1A
and
hmw2A
, respectively). In this study, we examined the levels of HMW1 and HMW2 expressed by
H. influenzae
isolates collected serially from patients with COPD. We found that expression of HMW1 and HMW2 in a given strain decreased over time in a majority of patients, reflecting progressive increases in the numbers of 7-bp repeats and associated with high serum titers of HMW1/HMW2-specific antibodies. We speculate that the presence of high titers of antibodies against the HMW1 and HMW2 adhesins and other immune factors in the lower respiratory tracts of patients with COPD may result in gradual selection for bacteria with reduced levels of HMW1 and HMW2.
Helmet use and the risk of neck or cervical spine injury among users of motorized two-wheel vehicles
Authors: Moskal A , Martin J-L , Laumon B
Published: August 2008

Objective:

To quantify the effects of wearing a helmet on head and facial injury among users of motorized two-wheel vehicles and to determine if helmet use increases the risk of neck and cervical spine injury.

Design/method:

A population-based study involving injured riders from the Rhône Road Trauma Registry from 1996 to 2005. Victims were only included if they had an injury to a body region other than (or in addition to) the head, face, neck, or cervical spine. Thus, inclusion was not affected by helmet use by the rider. The risk of head, face, neck, and cervical spine injury was assessed, with helmet use as the exposure of interest using logistic regression analyses. Adjusted odds ratios and corresponding confidence intervals were calculated.

Results:

Helmet use significantly decreased the risk of head and facial injuries. The adjusted odds ratios for non-helmeted riders were 2.43 (95% CI 2.05 to 2.87) and 3.02 (95% CI 2.48 to 3.67), respectively. There was no association between helmet use and the occurrence of neck or cervical spine injuries. The adjusted odds ratios for non-helmeted riders were 0.86 (95% CI 0.60 to 1.23) and 1.04 (95% CI 0.78 to 1.39), respectively.

Conclusion:

Helmets protect users of motorized two-wheel vehicles against head and facial injury without increasing the risk of neck or cervical spine injury.
Comparison between activity estimates obtained using bioenergetic and behavioural analysesContribution of the Groupe de Recherche Interuniversitaire en Limnologie (GRIL).
Authors: Guénard Guillaume , Boisclair Daniel , Ugedal Ola , Forseth Torbjørn , Jonsson Bror
Published: August 2008

Activity rate of Arctic char ( Salvelinus alpinus ) held in 90 m2 littoral enclosures were estimated using bioenergetic (with consumption estimated using stable caesium, 133Cs) and behavioural approaches (with fish movements quantified using video cameras). We found no statistically significant difference between values of activity rate obtained using the two approaches for three of the six experiments we performed. However, there was no relationship between estimates of activity rate obtained using the two approaches. Discrepancies may arise from the difficulty to meet assumptions regarding the temporal stability of the concentration of 133Cs in fish diet and of the assimilation coefficient of this tracer. When fish remain in an area where their behaviour can be well described (e.g., enclosure, habitat patches of littoral zones, coral reefs), the behavioural approach appears more robust to estimate activity rate because it depends most on a variable that is easiest to estimate (the number of movements performed). When these conditions are not met (low fish densities or major fish migrations), a reliable assessment of the concentration and assimilation of 133Cs in stomach contents appears critical to implement the bioenergetic approach based on this tracer.