bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age and sex differences in muscle sympathetic nerve activity in relation to haemodynamics, blood volume and left ventricular size
Authors: Best Stuart A. , Okada Yoshiyuki , Galbreath M. Melyn , Jarvis Sara S. , Bivens Tiffany B. , Adams‐Huet Beverley , Fu Qi 
Published: January 2014

New Findings
What is the central question of this study?
The study was designed to investigate the age‐ and sex‐related differences in muscle sympathetic nerve activity (MSNA) in relation to age‐ and sex‐related differences in haemodynamics, blood volume and left ventricular size and function.
What is the main finding and its importance?
Age‐related increases in MSNA were associated with decreases in blood volume in men only, and only in men was there a significant relation between MSNA and forearm vascular resistance. These results show that age and sex independently alter the neural control of blood pressure and may provide insights into the pathogenesis of hypertension.
We compared the effect of age‐ and sex‐related differences in haemodynamics, blood volume (BV) and left ventricular (LV) size and mass on resting muscle sympathetic nerve activity (MSNA) in healthy, normotensive adults. Twenty young men (19–47 years old) and 20 young women (21–46 years old) as well as 15 older men (62–80 years old) and 15 older women (60–82 years old) were studied. Cardiac output (acetylene rebreathing), total peripheral resistance, forearm vascular resistance (FVR; venous occlusion plethysmography) and MSNA were measured during supine rest. Blood volume was calculated (CO rebreathing), and LV mass, end‐diastolic (LVEDV) and end‐systolic volumes (LVESV) were measured using magnetic resonance imaging. Cardiac index (P < 0.001 and P = 0.016), BV (both P < 0.001), LV mass (P < 0.001 and P = 0.002), LVEDV (P < 0.001 and P = 0.002) and LVESV (both P < 0.001) were lower in the older and female groups, respectively. Total peripheral resistance was significantly higher in the older (P < 0.001) and female groups (P = 0.014), but FVR was increased in the female groups (P = 0.048) only (age, P = 0.089). The MSNA was greater in the older groups (P < 0.001) only (sex, P = 0.228). Increased MSNA was shown to correlate with a decrease in BV (P = 0.004) in men only when adjusted for age (women, P = 0.133). There was a positive relation between MSNA and FVR (P = 0.020) in men but not women (P = 0.422). There were no significant relations between MSNA and LV mass, LVEDV or LVESV. The findings suggest that the increase in resting MSNA with age may be related to the decline in BV in men only, but it is unknown whether sex differences in sympathetic adrenergic vasoconstriction occur independently of these changes.
Alterations in Notch signalling in skeletal muscles from mdx and dko dystrophic mice and patients with Duchenne muscular dystrophy
Authors: Church Jarrod E. , Trieu Jennifer , Chee Annabel , Naim Timur , Gehrig Stefan M. , Lamon Séverine , Angelini Corrado , Russell Aaron P. , Lynch Gordon S. 
Published: January 2014

New Findings
What is the central question of this study?
The Notch signalling pathway plays an important role in muscle regeneration, and activation of the pathway has been shown to enhance muscle regeneration in aged mice. It is unknown whether Notch activation will have a similarly beneficial effect on muscle regeneration in the context of Duchenne muscular dystrophy (DMD).
What is the main finding and its importance?
Although expression of Notch signalling components is altered in both mouse models of DMD and in human DMD patients, activation of the Notch signalling pathway does not confer any functional benefit on muscles from dystrophic mice, suggesting that other signalling pathways may be more fruitful targets for manipulation in treating DMD.
AbstractIn Duchenne muscular dystrophy (DMD), muscle damage and impaired regeneration lead to progressive muscle wasting, weakness and premature death. The Notch signalling pathway represents a central regulator of gene expression and is critical for cellular proliferation, differentiation and apoptotic signalling during all stages of embryonic muscle development. Notch activation improves muscle regeneration in aged mice, but its potential to restore regeneration and function in muscular dystrophy is unknown. We performed a comprehensive examination of several genes involved in Notch signalling in muscles from dystrophin‐deficient mdx and dko (utrophin‐ and dystrophin‐null) mice and DMD patients. A reduction of Notch1 and Hes1 mRNA in tibialis anterior muscles of dko mice and quadriceps muscles of DMD patients and a reduction of Hes1 mRNA in the diaphragm of the mdx mice were observed, with other targets being inconsistent across species. Activation and inhibition of Notch signalling, followed by measures of muscle regeneration and function, were performed in the mouse models of DMD. Notch activation had no effect on functional regeneration in C57BL/10, mdx or dko mice. Notch inhibition significantly depressed the frequency–force relationship in regenerating muscles of C57BL/10 and mdx mice after injury, indicating reduced force at each stimulation frequency, but enhanced the frequency–force relationship in muscles from dko mice. We conclude that while Notch inhibition produces slight functional defects in dystrophic muscle, Notch activation does not significantly improve muscle regeneration in murine models of muscular dystrophy. Furthermore, the inconsistent expression of Notch targets between murine models and DMD patients suggests caution when making interspecies comparisons.
The role of brain natriuretic peptide in maintaining myometrial quiescence during pregnancy
Authors: Carvajal Jorge A. 
Published: January 2014

New Findings
What is the topic of this review?
Myometrial quiescence is a highly regulated process, in which pregnant myometrium remains completely relaxed, overcoming its inherent tendency to contract. The maintenance of myometrial quiescence is a key step in controlling the duration of pregnancy. Currently, the mechanisms underlying myometrial quiescence of pregnancy are not fully known.
What advances does it highlight?
Brain natriuretic peptide is produced by the fetal membranes (chorion and amnion) and acts in a paracrine fashion. Brain natriuretic peptide plays a key role in maintaining myometrial quiescence. A premature decrease in production of brain natriuretic peptide may lead to preterm labour.
Myometrial quiescence is a physiological stage of the myometrium during pregnancy. It is a period of active relaxation of the myometrial smooth muscle cells; myometrial quiescence is responsible for maintaining pregnancy. The precise mechanisms underlying myometrial quiescence have not been completely elucidated, although many mediators and cellular pathways have been described as playing a role. Fetal membranes (chorion and amnion) produce and release one or more substances that inhibit myometrial contractions, playing a central role in the maintenance of myometrial quiescence. Brain natriuretic peptide (BNP) is more potent than any other natriuretic peptide in inhibiting myometrial contractions in vitro. Brain natriuretic peptide is produced by the chorion and amnion, mainly during myometrial quiescence, and decreasing towards the end of pregnancy. Production of BNP is reduced in fetal membranes obtained from women in preterm labour. It is postulated that BNP, acting in a paracrine fashion, plays a key role in the maintaining myometrial quiescence and, therefore, controlling the duration of pregnancy. Furthermore, it is postulated that a premature decrease of BNP production by the fetal membranes may cause preterm labour and preterm birth.
Effects of Temperature Changes on Creep Crack Growth for a Low Alloy Butt Weld
Authors: Shi Jinhua 
Published: January 2014

R5 is an assessment procedure for the high temperature response of structures and R5 Volume 7 specifies the creep crack growth assessment for low alloy welds.
For high temperature low alloy butt welds, the effects of the welding residual stresses on the creep crack growth for a circumferential defect has been investigated by Shi under a constant temperature of 532.7°C.
In addition to the welding residual stresses, it is well known that temperatures also affect significantly creep deformation, creep rupture and accordingly creep crack growth. Hence, in this paper an investigation for the effects of temperature changes on the creep crack growth and also on component remnant lives has been carried out.
In this paper, for a typical low alloy butt weld in ½Cr½Mo¼V (‘½CMV’) pipework with 2¼Cr weld metal under a given internal pressure and a bending welding residual stress of 60MPa, a series of creep crack growth analyses have been conducted using the R5 Volume 7 assessment procedure, assuming different operating temperatures during different operating periods. A postulated internal circumferential defect (semi-elliptical surface-breaking surface defect) of 2.3 mm deep by 15 mm long has been used.
The investigation results are presented by a series of graphs which show the effects of the temperature changes on the creep crack growth and plant remnant lives for the weld studied. After a detailed discussion, conclusions can be drawn.
Aeroacoustics of Opposing Planar Air Jets
Authors: Hassaballa Moustafa , Ziada Samir , Arthurs David 
Published: January 2014

The self-excited response of two opposing planar air jets is experimentally examined as a function of both flow velocity of the jets, as well as the impingement distance, i.e. the distance z between them. This initial study is performed for a single jet thickness of h = 2 mm and a spanwise aspect ratio of 50. Two sets of experiments have been performed, with the first set of measurements having been obtained over a range of impingement ratios from z/h = 7 to z/h = 130 for several moderate Mach numbers (M = 0.44, 0.58 & 0.73), whereas the second set of measurements has been performed by varying the jet Mach number at fixed impingement ratios.
The opposing planar jets are found to produce intense acoustic tones over the entire range of impingement ratio and flow velocity examined in this study, showing robust oscillation behavior even for very large distances between the jets. Acoustic tone frequency has been found to increase linearly with the jet exit velocity at constant impingement ratio and to decrease with the impingement distance at constant jet velocity. The flow field over the oscillation cycle has been investigated by means of phase-averaged PIV measurements technique, which has shown that the high noise levels and acoustic tones are produced by a pronounced flapping oscillation of the opposing jet columns.
Assessment of the Influence of Bulging and the Thermal Gradients in the Stress Level in the Cylindrical Section of a Coke Drum
Authors: Araque Egler D. , Vivas Gabriel A. 
Published: January 2014

Several studies recognized that cracks in delayed coke drums resulted from low cycle fatigue induced by cyclic thermal stress [1], [2], [3]. According to a coke drum survey coordinated by API in 1996 [1], there are two different areas where cracks are produced. The first zone is located at the shell to skirt weld, and the second at the bulging areas found in the cylindrical section. In the second case, from 145 coke drums 57% reported that had shell bulging problems. Of the drums that bulged, 87% also showed cracks.
In order to estimate the level of stress, finite element analysis of a bulged cylinder was performed. The study was carried out running a sequentially-coupled thermo-mechanical analysis. In the first step, a thermal analysis is used to estimate the variation of temperature with time. These temperatures serve as input to a mechanical stress analysis that was made in a second step.
The assessment shows the influence of thermal gradients obtained for a period of 26 months for several bulging patterns that were identified from the analysis of 28 laser mappings of coke drums. The results indicated that the level of stress could reach the plastic deformation considering that the material has yield strength equal to the minimum specified in ASME Section II, part D. The zones where maximum axial stresses were found are consistent with areas where cracking has been reported in many coke drums.
Deep Well Drilling Applications
Authors: McKie Nigel R. , Peters Daniel T. , Tooley Keegan A. 
Published: January 2014

The majority of oilfield Wellhead and Tree equipment has been designed with guidance from codes API 6A and 17D. However, their design methods are not the most appropriate for the new High Pressure High Temperature (HPHT) applications; equipment rated above 15 ksi (103 MPa) Working Pressure and/or above 350 °F (177 °C). This paper discusses the limitations of established design methods and presents more suitable methods for HPHT applications.
FEA is well established as a stress analysis method for use in conventional Pressure Vessel design; however it is not so well established for load bearing interfaces. This leaves a gap in our Design Methods, since load bearing interfaces are intrinsic to Wellhead Equipment Pressure Vessel design. Intrinsic because many of our Pressure Vessels are “capped” by hangers and connectors instead of flanges; if a hanger Load Shoulder fails then the Pressure Vessel above it has failed.
Unique to the oilfield are infrequent but extremely high loads. These loads are much higher than the Working Condition and in most cases they stem from field testing and emergency situations. If the established ASME methods are used for these cases certain projects may not be viable.
A Comparison of Finite Element Cohesive-Zone Modelling With the Process-Zone Approach for the Prediction of Delayed Hydride Cracking
Authors: Martin Michael 
Published: January 2014

Zirconium alloys, as used in water-cooled nuclear reactors, are susceptible to a time-dependent damage mechanism known as Delayed Hydride Cracking, or DHC. Corrosion of the zirconium alloy in the presence of water generates hydrogen that subsequently diffuses through the metallic structure towards stress concentrating features such as notches or cracks.
Canadian standard CSA N285.8–10 uses a process-zone modelling approach to define a threshold stress level beyond which DHC is predicted to occur. The process-zone analysis to calculate the threshold stress level generally proceeds by representing the process-zone as a crack, the length of which is determined by the superposition of stress intensity factors obtained from handbook solutions or cracked-body finite element models. Process-zone models are a subset of the more general class of cohesive-zone models and cohesive elements are available in a number of standard finite element codes. Cohesive elements can be used to simulate the process-zone response, or indeed more complex cohesive behaviour.
In this paper, the stress and displacement results from finite element based cohesive-zone modelling of a sharp crack and blunt notches of various root radii are compared with analytical process-zone solutions. The cohesive-zone results are also compared with the process-zone formulation used in CSA N285.8–10. The results show that finite element based cohesive-zone analysis can be used to replicate the process-zone results. The key benefit of finite element based cohesive-zone modelling is that it provides a framework for investigating the DHC characteristics of arbitrary hydride distributions, using readily available techniques.
Derivation of Design Fatigue Curves for Austenitic Stainless Steel Grades 1.4541 and 1.4550 Within the German Nuclear Safety Standard KTA 3201.2
Authors: Schuler Xaver , Herter Karl-Heinz , Rudolph Jürgen 
Published: January 2014

Titanium and niobium stabilized austenitic stainless steels X6CrNiTi18-10S (material number 1.4541, correspondent to Alloy 321) respectively X6CrNiNb18-10S (material number 1.4550, correspondent to Alloy 347) are widely applied materials in German nuclear power plant components. Related requirements are defined in Nuclear Safety Standard KTA 3201.1. Fatigue design analysis is based on Nuclear Safety Standard KTA 3201.2. The fatigue design curve for austenitic stainless steels in the current valid edition of KTA 3201.2 is essentially identical with the design curve included in ASME-BPVC III, App I (ed. 2007, add. July 2008 respectively back editions).
In the current code revision activities of KTA 3201.2 the compatibility of latest in air fatigue data for austenitic stainless steels with the above mentioned grades were examined in detail. The examinations were based on statistical evaluations of 149 strain controlled test data at room temperature and 129 data at elevated temperatures to derive best-fit mean data curves. Results of two additional load controlled test series (at room temperature and 288°C) in the high cycle regime were used to determine a technical endurance limit at 107 cycles. The related strain amplitudes were determined by consideration of the cyclic stress strain curve. The available fatigue data for the two austenitic materials at room temperature and elevated temperatures showed a clear temperature dependence in the high cycle regime demanding for two different best-fit curves. The correlation of the technical endurance limit(s) at room temperature and elevated temperatures with the ultimate strength of the materials is discussed.
Design fatigue curves were derived by application of the well known factors to the best-fit curves. A factor of SN = 12 was applied to load cycles correspondent to the NUREG/CR-6909 approach covering influences of data scatter, surface roughness, size and sequence. In terms of strain respectively stress amplitudes in the high cycle regime, for elevated temperatures (>80°C) a factor of Sσ = 1.79 was applied considering and combining in detail the partial influences of data scatter surface roughness, size and mean stress. For room temperature a factor of Sσ = 1.88 shall be applied.
As a result, new design fatigue curves for austenitic stainless steel grades 1.4541 and 1.4550 will be available within the German Nuclear Safety Standard KTA 3201.2. The fatigue design rules for all other austenitic stainless steel grades will be based on the new ASME-BPVC III, App I (ed. 2010) design curve.
Investigation on In-Flow Fluidelastic Instability of an Array of Tubes
Authors: Hirota Kazuo , Morita Hideyuki , Hirai Jun , Iwasaki Akihisa , Utsumi Seiho , Shimamura Kengo , Kawakami Ryoichi 
Published: January 2014

Fluidelastic instability (FEI) remains the most important vibration mechanism in steam generators. Fluidelastic instability of an array of tubes thought to be mainly occurred in the cross-flow direction. In the present day, some researchers reported possibility of occurrence of fluidelastic instability in the in-flow direction. However, the phenomenon of the in-plane FEI has not been well recognized compared to the transverse FEI.
In this study, air flow tests using cantilevered straight cylinder array of tubes in triangular configuration were conducted. It is confirmed that the in-flow FEI could be occurred and the critical flow velocity in the in-flow direction is larger than that of in the cross flow direction. Furthermore, the relationship between P/D of an array of tubes and the critical flow velocity in the in-flow direction was also investigated.
Simulating Natural Axial Crack Growth in Dissimilar Metal Welds due to Primary Water Stress Corrosion Cracking
Authors: Rudland D. , Shim D.-J. , Xu S. 
Published: January 2014

For axial subcritical crack growth in dissimilar metal (DM) welds due to Primary Water Stress Corrosion Cracking (PWSCC), the crack growth in the length direction is limited to the weld width since the base materials are not susceptible to this type of cracking mechanism. However, the crack may continue to grow in the depth direction until it penetrates the wall thickness. Since the weld width can be much less than the pipe wall thickness, axial cracks have the potential of growing much deeper than they are long. Published stress intensity factor influence functions for semi-elliptical axial cracks in pipe suggest that as the half crack length (c) becomes smaller than the crack depth (a), the stress intensity factor at the deepest point of the crack begins to decrease. These solutions suggest that in many cases, these types of cracks may arrest before penetrating the wall thickness. However, natural flaw growth using the Advanced Finite Element Method (AFEA) suggests that these cracks will not arrest and the stress intensity factor does not decrease in a manner suggested by idealized flaw growth analyses using semi-elliptical crack influence functions.
In this paper, modifications to idealized flaw growth analyses are proposed to predict the natural PWSCC axial crack growth within DM welds. A series of modified flaw growth predictions are presented and compared to published AFEA results. The simplistic rules developed in the paper allow the use of standard influence functions in predicting the time to leakage for axial cracks in DM welds without having to conduct the more complex AFEA analyses.
French Methodology Proposal for Environmentally Assisted Fatigue Assessment
Authors: Métais Thomas , Courtin Stéphan , Genette Pierre , Lefrançois André , Massoud Jean-Paul , De Baglion Laurent 
Published: January 2014

Environmental assisted fatigue is a phenomenon that has been investigated over the past 30 years through many test campaigns in various laboratories around the world. It is receiving nowadays an increased level of attention as many nuclear plants will see their life-time extended to up to 60 years. To provide a set of rules for this significant life extension, international codes have already proposed code cases to formally integrate these effects.
More particularly, the ASME code has based itself on the NUREG/CR-6909 [1] to elaborate the Code Case N-792 [2] and suggests a modification of the fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which multiplies the typical usage factor.
In France, the EDF and AREVA objective is also to more explicitly integrate these effects in the RCC-M code basing itself on international methodologies but also results from French in-house testing campaigns [3]. The approach in this paper is globally similar to the one in the ASME code: it will indeed consist in an update of the fatigue curve as well as the calculation of an environmental penalty factor. Nevertheless, the methodologies differ in their detailed implementation, as was already hinted in previous papers discussing the French methodology [4–5]. This paper will present the proposal as well as highlight the differences with the ASME methodology.