bluuebunny/crossref_metadata_2025 huggingface dataset:
Intervention thresholds and cesarean section rates: A time‐trends analysis
Authors: Rose Anna , Raja Edwin Amalraj , Bhattacharya Sohinee , Black Mairead
Published: June 2018

Introduction

To improve understanding of rising cesarean section (CS) rates in the UK, this study assessed the relation between clinician thresholds for performing CS for delayed labor progress or suspected fetal distress and corresponding CS rates in Aberdeen, UK.

Material and methods

Time‐trends analysis of term births from 1988 to 2012 in a population of nulliparous women (N = 53 745) in Aberdeen, UK, using Chi‐square test for trend, and binary logistic regression. Data were obtained from the Aberdeen Maternity and Neonatal Databank.

Results

Unplanned CS rates per quintile increased from 11.0% (1391/12 686) to 21.1% (2383/11 273) between 1988 and 2012, while planned CS rates increased from 2.7% (338/12 686) to 5.2% (591/11 273). The median duration of labor before CS for delayed progress per quintile decreased from 17.2 (IQR 12.5‐22.3) to 13.1 hours (9.6‐16.9) before first stage CS and from 17.1 (12.6‐22.3) to 15.3 (11.5‐19.1) hours before second stage CS (P < .001). The proportion of CS for suspected fetal distress performed with evidence of fetal acidosis declined from 23.4% (98/418) to 17.4% (106/608) per quintile (P < .01). Neonatal unit admission (adjusted OR 1.99, 95% CI 1.85‐2.14) was more likely following unplanned CS than vaginal births. Birth trauma was less likely following both unplanned (adjusted OR 0.48, 95% CI 0.39‐0.60) and planned (adjusted OR 0.33, 95% CI 0.18‐0.63) CS.

Conclusion

Increased CS rates can be partly attributed to lowered clinical thresholds for intrapartum CS. Higher CS rates are associated with less birth trauma for the offspring.
The enigmatic role of the neutrophil in asthma: Friend, foe or indifferent?
Authors: Snelgrove R. J. , Patel D. F. , Patel T. , Lloyd C. M.
Published: June 2018

Whilst severe asthma has classically been categorized as a predominantly Th2‐driven pathology, there has in recent years been a paradigm shift with the realization that it is a heterogeneous disease that may manifest with quite disparate underlying inflammatory and remodelling profiles. A subset of asthmatics, particularly those with a severe, corticosteroid refractory disease, present with a prominent neutrophilic component. Given the potential of neutrophils to impart extensive tissue damage and promote inflammation, it has been anticipated that these cells are closely implicated in the underlying pathophysiology of severe asthma. However, uncertainty persists as to why the neutrophil is present in the asthmatic lung and what precisely it is doing there, with evidence supporting its role as a protagonist of pathology being primarily circumstantial. Furthermore, our view of the neutrophil as a primitive, indiscriminate killer has evolved with the realization that neutrophils can exhibit a marked anti‐inflammatory, pro‐resolving and wound healing capacity. We suggest that the neutrophil likely exhibits pleiotropic and potentially conflicting roles in defining asthma pathophysiology—some almost certainly detrimental and some potentially beneficial—with context, timing and location all critical confounders. Accordingly, indiscriminate blockade of neutrophils with a broad sword approach is unlikely to be the answer, but rather we should first seek to understand their complex and multifaceted roles in the disease state and then target them with the same subtleties and specificity that they themselves exhibit.
Tschimganine and its derivatives extend the chronological life span of yeast via activation of the Sty1 pathway
Authors: Hibi Takahide , Ohtsuka Hokuto , Shimasaki Takafumi , Inui Shougo , Shibuya Masatoshi , Tatsukawa Hideki , Kanie Kei , Yamamoto Yoshihiko , Aiba Hirofumi
Published: June 2018

Most antiaging factors or life span extenders are associated with calorie restriction (CR). Very few of these factors function independently of, or additively with, CR. In this study, we focused on tschimganine, a compound that was reported to extend chronological life span (CLS). Although tschimganine led to the extension of CLS, it also inhibited yeast cell growth. We acquired a Schizosaccharomyces pombe mutant with a tolerance for tschimganine due to the gene crm1. The resulting Crm1 protein appears to export the stress‐activated protein kinase Sty1 from the nucleus to the cytosol even under stressful conditions. Furthermore, we synthesized two derivative compounds of tschimganine, α‐hibitakanine and β‐hibitakanine; these derivatives did not inhibit cell growth, as seen with tschimganine. α‐hibitakanine extended the CLS, not only in S. pombe but also in Saccharomyces cerevisiae, indicating the possibility that life span regulation by tschimganine derivative may be conserved across various yeast species. We found that the longevity induced by tschimganine was dependent on the Sty1 pathway. Based on our results, we propose that tschimganine and its derivatives extend CLS by activating the Sty1 pathway in fission yeast, and CR extends CLS via two distinct pathways, one Sty1‐dependent and the other Sty1‐independent. These findings provide the potential for creating an additive life span extension effect when combined with CR, as well as a better understanding of the mechanism of CLS.
How to make a particular case for person‐centred patient care: A commentary on Alexandra Parvan
Authors: Graham George
Published: June 2018

In recent years, a person‐centred approach to patient care in cases of mental illness has been promoted as an alternative to a disease orientated approach. Alexandra Parvan's contribution to the person‐centred approach serves to motivate an exploration of the approach's most apt metaphysical assumptions. I argue that a metaphysical thesis or assumption about both persons and their uniqueness is an essential element of being person‐centred. I apply the assumption to issues such as the disorder/disease distinction and to the continuity of mental health and illness.
A new HPF specimen carrier adapter for the use of high‐pressure freezing with cryoscanning electron microscope: two applications: stearic acid organization in a hydroxypropyl methylcellulose matrix and mice myocardium
Authors: PAYRE B. , GONTIER E. , JARRAY A. , MARTINEZ Y. , LAUGIER J.P. , DELALLEAU A. , GAILLARD B.M. , ANSELME I. , GOUDOUNÈCHE D. , FOURQUAUX I. , HEMATI M. , GERBAUD V. , DELISLE M.B. , GUILBEAU‐FRUGIER C.
Published: June 2018

Cryogenic transmission electron microscopy of high‐pressure freezing (HPF) samples is a well‐established technique for the analysis of liquid containing specimens. This technique enables observation without removing water or other volatile components. The HPF technique is less used in scanning electron microscopy (SEM) due to the lack of a suitable HPF specimen carrier adapter. The traditional SEM cryotransfer system (PP3000T Quorum Laughton, East Sussex, UK; Alto Gatan, Pleasanton, CA, USA) usually uses nitrogen slush. Unfortunately, and unlike HPF, nitrogen slush produces water crystal artefacts.

So, we propose a new HPF specimen carrier adapter for sample transfer from HPF system to cryogenic‐scanning electronic microscope (Cryo‐SEM). The new transfer system is validated using technical two applications, a stearic acid in hydroxypropyl methylcellulose solution and mice myocardium. Preservation of samples is suitable in both cases. Cryo‐SEM examination of HPF samples enables a good correlation between acid stearic liquid concentration and acid stearic occupation surface (only for homogeneous solution). For biological samples as myocardium, cytoplasmic structures of cardiomyocyte are easily recognized with adequate preservation of organelle contacts and inner cell organization. We expect this new HPF specimen carrier adapter would enable more SEM‐studies using HPF.
The effect of supplementing sheep with rapeseed and linseed oils on the activity of pancreatic digestive enzymes
Authors: Kowalik Barbara , Majewska Małgorzata P. , Miltko Renata , Bełżecki Grzegorz
Published: June 2018

The aim of this study was to compare the effect of rapeseed and linseed oils added to the diet on pancreatic enzyme activities in sheep. The experiment was conducted on six adult sheep with a catheter introduced into the common bile–pancreatic duct and a T‐cannula into the duodenum. The animals were divided into three groups, two sheep in each. A twice‐replicated 3 × 3 Latin square was used in the experimental design. The sheep were fed meadow hay and the concentrate alone or the same ration supplemented with rapeseed or linseed oils at a dose of 5% of the basal diet. After adaptation period, a mixture of pancreatic and bile juice was collected for three consecutive days. The secretion of bile–pancreatic juice showed an increasing trend in sheep fed rapeseed and linseed oils (69.5 and 68.5 ml/hr respectively) in comparison with control ones (59.8 ml/hr). Lipase and trypsin activities were significantly increased when sheep were fed diets with rapeseed or linseed oils (175 and 21.6 or 179 and 23.2 U/L respectively) in comparison with those fed control diet (128 and 13.1 U/L respectively). It was concluded that oil as a dietary supplement can mainly modify the secretion of bile–pancreatic juice and enzymatic activity of the pancreas and also might affect animal production.
Mandible strike kinematics of the trap‐jaw ant genus Anochetus Mayr (Hymenoptera: Formicidae)
Authors: Gibson J. C. , Larabee F. J. , Touchard A. , Orivel J. , Suarez A. V.
Published: June 2018

High‐speed power‐amplification mechanisms are common throughout the animal kingdom. In ants, power‐amplified trap‐jaw mandibles have evolved independently at least four times, including once in the subfamily Ponerinae which contains the sister genera Odontomachus and Anochetus. In Odontomachus, mandible strikes have been relatively well described and can occur in <0.15 ms and reach speeds of over 60 m s−1. In contrast, the kinematics of mandible strikes have not been examined in Anochetus, whose species are smaller and morphologically distinct from Odontomachus. In this study, we describe the mandible strike kinematics of four species of Anochetus representative of the morphological, phylogenetic, and size diversity present within the genus. We also compare their strikes to two representative species of Odontomachus. We found that two species, Anochetus targionii and Anochetus paripungens, have mandible strikes that overall closely resemble those found in Odontomachus, reaching a mean maximum rotational velocity and acceleration of around 3.7 × 104 rad s−1 and 8.5 × 108 rad s−2, respectively. This performance is consistent with predictions based on body size scaling relationships described for Odontomachus. In contrast, Anochetus horridus and Anochetus emarginatus have slower strikes relative to the other species of Anochetus and Odontomachus, reaching mean maximum rotational velocity and acceleration of around 1.3 × 104 rad s−1 and 2 × 108 rad s−2, respectively. This variation in strike performance among species of Anochetus likely reflects differences in evolutionary history, physiology, and natural history among species.
The complexity of body image following bariatric surgery: a systematic review of the literature
Authors: Ivezaj V. , Grilo C. M.
Published: June 2018

Poor body image is common among individuals seeking bariatric surgery and is associated with adverse psychosocial sequelae. Following massive weight loss secondary to bariatric surgery, many individuals experience excess skin and associated concerns, leading to subsequent body contouring procedures. Little is known, however, about body image changes and associated features from pre‐to post‐bariatric surgery and subsequent body contouring. The objective of the present study was to conduct a comprehensive literature review of body image following bariatric surgery to help inform future clinical research and care. The articles for the current review were identified by searching PubMed and SCOPUS and references from relevant articles. A total of 60 articles examining body image post‐bariatric surgery were identified, and 45 did not include body contouring surgery. Overall, there was great variation in standards of reporting sample characteristics and body image terms. When examining broad levels of body image dissatisfaction, the literature suggests general improvements in certain aspects of body image following bariatric surgery; however, few studies have systematically examined various body image domains from pre‐to post‐bariatric surgery and subsequent body contouring surgery. In conclusion, there is a paucity of research that examines the multidimensional elements of body image following bariatric surgery.
Detection of interactions between the pea root rot pathogens Aphanomyces euteiches and Fusarium spp. using a multiplex qPCR assay
Authors: Willsey T. L. , Chatterton S. , Heynen M. , Erickson A.
Published: June 2018

Pea root rot complex (PRRC) describes a group of closely associated soilborne pathogens that cause root rot disease in field pea. Aphanomyces euteiches and several Fusarium spp. are the most prevalent and damaging microorganisms within this complex, although the impact of interspecific interactions on disease progression remains largely unexplored. Furthermore, a fast and reliable method of detecting and quantifying these pathogens is not currently available. The objectives of this experiment were to: (i) investigate the effect of microbial interactions on root rot severity in pea under greenhouse conditions; and (ii) characterize changes in colonization rates when multiple pathogens are present using qPCR. Seeds were exposed to three species of Fusarium and were planted into A. euteiches‐infested soil in varying combinations. For each experimental treatment, an index of disease severity was used to visually rate disease symptoms. Additionally, two triplex quantitative PCR (qPCR) assays were designed to detect and quantify changes in pathogen population dynamics on the roots. Both assays demonstrated a high degree of sensitivity and efficiency. Results from two independent greenhouse trials indicated an increase in disease severity in the presence of multiple pathogen species compared to single inoculations. Specifically, roots infected with A. euteiches were more susceptible to fusarium root rot than those exposed only to Fusarium spp. These observations were confirmed by qPCR results, which revealed significant changes in colonization rates when multiple species were present. These findings suggest an increased risk of yield loss in regions where A. euteiches and Fusarium spp. co‐occur.
AAA: Triple Adaptive Bayesian Designs for the Identification of Optimal Dose Combinations in Dual-Agent Dose Finding Trials
Authors: Lyu Jiaying , Ji Yuan , Zhao Naiqing , Catenacci Daniel V. T.
Published: June 2018

We propose a flexible design for the identification of optimal dose combinations in dual-agent dose finding clinical trials. The design is called AAA, standing for three adaptations: adaptive model selection, adaptive dose insertion and adaptive cohort division. The adaptations highlight the need and opportunity for innovation for dual-agent dose finding and are supported by the numerical results presented in the proposed simulation studies. To our knowledge, this is the first design that allows for all three adaptations at the same time. We find that AAA enhances the chance of finding the optimal dose combinations and shortens the trial duration. A clinical trial is being planned to apply the AAA design and a Web tool is being developed for both statisticians and non-statisticians.
Containment for Occupied Wheeled Mobility Devices on Passenger Rail Trains
Authors: Hunter-Zaworski Katharine , Severson Kristine , Shurland Melissa
Published: June 2018

The paper addresses the need to examine the trade-offs between passenger safety and independence in travel by people who use wheeled mobility devices on passengers trains. It has been the practice in Asia, North America and Europe to not require passengers in wheeled mobility devices (WhMDs) such as wheelchairs to secure their wheeled devices when traveling by rail. There are several motivations for examining the need for containment of WhMDs on passenger trains. In general the population is aging and getting larger, and this is reflected in the types of WhMDs that passengers are trying to bring on board trains. The US Federal Railroad Administration (FRA) and members of the Rail Vehicle Access Advisory Committee (RVAAC) requested a feasibility study on the economic impacts of accommodating two or more wheeled mobility devices in the accessible seating area [1]. The feasibility study indicated that there is space to accommodate two WhMDs without significant impact on revenue seat loss, however safety issues have emerged, and are the basis of this paper. The three research questions that are addressed include:

I. What is the appropriate interior space that accounts for WhMD maneuvering?

II. What are the appropriate levels of deceleration and jerk to be considered in the vehicle interior for passenger rail vehicles under severe braking?

III. What is the appropriate level of containment for occupied wheeled mobility devices on passenger rail vehicles?

The paper examines research literature and other findings from both North America and Europe that address in part the research questions.
Ball Indentation Technique to Estimate Fracture Toughness of High-Strength Rail Steels
Authors: Yu Feng , Jar P. Y. Ben , Hendry Michael T.
Published: June 2018

In this work, the non-destructive ball indentation technique is applied to estimate fracture toughness for three types of high-strength rail steels based on continuum damage mechanics. Damage parameter, in terms of the deterioration of elastic modulus, is measured for three rail steels using the loading-unloading smooth tensile test, based on which a ductile damage model is calibrated to determine the critical damage parameter at the onset of fracture. Meanwhile, an instrumented ball indentation test is conducted on the three rail steels to generate damage as a function of contact depth under indentation compression. The critical damage parameter from the smooth specimen is then applied to the indentation test to determine the critical contact depth for calculating the indentation fracture toughness based on the concept of indentation energy to fracture. Results show that although the magnitude of the so-determined indentation fracture toughness is greater than that of the corresponding mode I critical stress intensity factor (KIc) measured using the pre-cracked single-edge-notched bend (SENB) specimen, the former can well predict the ranking order of the KIc values among the three rail steels.
Analysis of Restricted Speed Related Train Accidents in the United States, 2000 to 2016
Authors: Zhang Zhipeng , Liu Xiang , Bian Zheyong
Published: June 2018

Railroads contribute to the national economy by carrying over 40% of intercity freight ton-miles in the United States. Train accidents cause damage to infrastructure and rolling stock, disrupt operations, and have the potential to result in casualties and damage the environment. A clear understanding and analysis of accident risk based on historical accidents can support the development and prioritization of effective accident prevention strategies. While extensive previous studies have focused on the safety risks associated with a variety of train operation conditions, much less work has been undertaken to evaluate train risk and safety under restricted speeds. As defined in 49 CFR 236 Subpart G, restricted speed is a speed that permits stopping within one-half the range of vision, but not exceeding 20 miles per hour. Nevertheless, some severe accidents at restricted speeds occurred in the last few years and are also highlighted in both NTSB and FRA reports. In this paper, we develop a quantitative analysis of restricted-speed accidents occurring between 2000 and 2016, based on the data from the U.S. Federal Railroad Administration. While overall accident rates have been proven to decline in prior studies, the preliminary results show that the rate of train accidents under restricted speeds fluctuates in the study period, without a significant increasing or decreasing trend. Furthermore, the distribution of restricted-speed accident severity, accident risk, and other pertinent characteristics are covered in this study.
Lifetime Maximization by Optimizing the Computation/Communication Strategy for Railway Wireless Monitoring System
Authors: Ma Xiaoping , Dong Honghui , Liu Xiang , Jia Limin
Published: June 2018

For the railway wireless monitoring system, energy efficiency is important for prolonging the system lifetime and ensuring the successful transmission of the inspection data. In general, decreasing the size of the data packet is conductive to declining the transmission energy consumption. Hence, the inspection data packets should be processed before being transmitted. However, the energy consumption of data processing may also be considerable, especially for the vision-based monitoring system. Therefore, we propose an optimization methodology to address the trade-off of the energy usage between data processing and transmission in railway wireless monitoring systems. In addition, the various data types and transmission distances of the sensors may cause the unbalanced energy consumption, and it will shorten the system lifetime due to the failure of some sensors. To address this challenge, in our proposed optimization framework, we adopt customized compression ratios for each sensor to balance its energy consumption. On this basis, the system lifetime can be extended by minimizing and balancing the energy consumption simultaneously. Finally, we use several generalized numerical examples to demonstrate the superiority and practicality of the proposed strategy. Compared to previous methods in the literature, our proposed approach can increase service lifetime of wireless monitoring systems using equal and less energy.
Structural Performance of a Railway Tunnel Under Different Fire Scenarios
Authors: Elhami Khorasani Negar , Billittier John , Stavridis Andreas
Published: June 2018

Tunnel fires are low-probability high-consequence events that could lead to loss of lives, property damage, and long service disruptions. The rapid rise of gas temperature in excess of 1000 °C within the confined tunnel space can affect the structural integrity of the tunnel. Although tunnel fires may not necessarily cause collapse, significant structural damage and disruption to rail services can lead to major economic losses. The objective of this paper is to investigate the expected structural damage in a cut-and-cover tunnel if exposed to a fire event. The analyses are completed by numerical simulations.

In the first part of this work, the effects of fire scenario and variability in thermal properties of material, on the potential volume of damaged tunnel lining that would require repair are investigated. In case of tunnels, historical events show that limited accessibility to suppress the fire can cause the fire to burn for days. The fire scenarios considered in this work are defined based on (a) the worst-case envelop hydrocarbon fires such as the Rijswaterstaat (RWS) fire curve and the RABT ZTV fire curve, and (b) the potential heat release rates in railway tunnels.

In the second part of this study, the effect of fire scenario on structural performance of a cut-and-cover tunnel is studied. The geometry and cross section of the Howard street tunnel in Baltimore that experienced a major fire in 2001 is used as the case study. The results show that the fire scenario and duration, while contains significant uncertainty, is one of the most influential factors on evaluating response of the tunnel structures.
Relationships Between Wheel/Rail Surface Impact Loadings and Correspondingly Transmitted Tie/Ballast Impact Pressures for Revenue Train Operations
Authors: Watts Travis J. , Rose Jerry G. , Russell Ethan J.
Published: June 2018

A series of specially designed granular material pressure cells were precisely positioned directly below the rail at the tie/ballast interface to measure typical interfacial pressures exerted by revenue freight trains. These vertical pressures were compared to the recorded wheel/rail nominal and peak forces for the same trains traversing nearby mainline wheel impact load detectors (WILDs). The cells were imbedded within the bottom of new wood ties so that the surfaces of the pressure cells were even with the bottoms of the ties and the underlying ballast. The cells were inserted below consecutive rail seats of one rail to record pressures for a complete wheel rotation.

The stability and tightness of the ballast support influenced the magnitudes and consistencies of the recorded ballast pressures. Considerable effort was required to provide consistent ballast conditions for the instrumented ties and adjacent undisturbed transition ties. Norfolk Southern (NS) crews surfaced and tamped through the test section and adjacent approach ties. This effort along with normal accruing train traffic subsequently resulted in reasonably consistent pressure measurements throughout the test section.

The impact ratio (impact factor) and peak force values recorded by the WILDs compared favorably with the resulting magnitudes of the transferred pressures at the tie/ballast interface. High peak force and high impact ratio WILD readings indicate the presence of wheel imperfections that increase nominal forces at the rail/wheel interface. The resulting increased dynamic impact forces can contribute to higher degradation rates for the track component materials and more rapid degradation rates of the track geometry.

The paper contains comparative WILD force measurements and tie/ballast interfacial pressure measurements for loaded and empty trains. Typical tie/ballast pressures for locomotives and loaded freight cars ranges from 20 to 30 psi (140 to 210 kPa) for smooth wheels producing negligible impacts. The effect of increased wheel/rail impacts and peak force values on the correspondingly transmitted pressures at the tie/ballast interface is significant, with increased pressures of several orders of magnitude compared to nominal impact forces from wheels.
Propagation Prediction for Rail Communications in Urbanized Areas
Authors: Ellis Todd , Weiss Stephen
Published: June 2018

Radio propagation prediction for passenger rail operations using sub-UHF frequencies can be a complex matter. While propagation models and data containing terrain and obstruction information can be used to predict radio coverage, unique methodologies are required to accurately plan and implement rail communication systems. Federally-mandated Positive Train Control (PTC) system requirements rely on consistently available wireless communications, thus the imperative need to accurately design and construct radio networks to fulfill critical requirements.
Defect Prognostics Models for Spall Growth in Railroad Bearing Rolling Elements
Authors: De Los Santos Nancy , Tarawneh Constantine M. , Jones Robert E. , Fuentes Arturo
Published: June 2018

Prevention of railroad bearing failures, which may lead to catastrophic derailments, is a central safety concern. Early detection of railway component defects, specifically bearing spalls, will improve overall system reliability by allowing proactive maintenance cycles rather than costly reactive replacement of failing components. A bearing health monitoring system will provide timely detection of flaws. However, absent a well verified model for defect propagation, detection can only be used to trigger an immediate component replacement. The development of such a model requires that the spall growth process be mapped out by accumulating associated signals generated by various size spalls. The addition of this information to an integrated health monitoring system will minimize operation disruption and maintain maximum accident prevention standards enabling timely and economical replacements of failing components. An earlier study done by the authors focused on bearing outer ring (cup) raceway defects. The developed model predicts that any cup raceway surface defect (i.e. spall) once reaching a critical size (spall area) will grow according to a linear correlation with mileage. The work presented here investigates spall growth within the inner rings (cones) of railroad bearings as a function of mileage. The data for this study were acquired from defective bearings that were run under various load and speed conditions utilizing specialized railroad bearing dynamic test rigs owned by the University Transportation Center for Railway Safety (UTCRS) at the University of Texas Rio Grande Valley (UTRGV). The experimental process is based on a testing cycle that allows continuous growth of railroad bearing defects until one of two conditions are met; either the defect is allowed to grow to a size that does not jeopardize the safe operation of the test rig, or the change in area of the spall is less than 10% of its previous size prior to the start of testing. The initial spall size is randomly distributed as it depends on the originating defect depth, size, and location on the rolling raceway. Periodic removal and disassembly of the railroad bearings was carried out for inspection and defect size measurement along with detailed documentation. Spalls were measured using optical techniques coupled with digital image analysis, as well as, with a manual coordinate measuring instrument with the resulting field of points manipulated in MatLab™. Castings were made of spalls using low-melting, zero-shrinkage bismuth-based alloys, so that a permanent record of the spall geometry and its growth history can be retained. The main result of this study is a preliminary model for spall growth, which can be coupled with bearing condition monitoring tools that will allow economical and effective scheduling of proactive maintenance cycles that aim to mitigate derailments, and reduce unnecessary train stoppages and associated costly delays on busy railways.
Benefits of Prestressed HSRM Concrete Ties for Center Binding Conditions
Authors: Zeitouni Adam I. , Rizos Dimitris , Qian Yu
Published: June 2018

Concrete ties have become a promising alternative to timber ties for freight lines with increased curvature, high annual traffic, and large axle loads. They are also widely adopted in passenger lines. High strength (HS) concrete is the material of choice in the fabrication of prestressed concrete railroad ties. The higher strength of the concrete is directly related to higher values of the Elastic Modulus, thus increasing the rigidity of the material. The combination of increased strength, rigidity, and the material brittleness may lead to the development of high amplitude stresses with high gradients, which appears to be a common underlying cause of premature cracking and deterioration observed in some concrete ties. Realizing the current issues associated with the performance of concrete ties and recalling the findings of an almost fifteen-year-old research conducted at the University of South Carolina (USC), a hypothesis was formulated that there is a potential benefit in introducing weathered granite aggregates into mix designs for railroad concrete ties. A high strength, yet lower rigidity, concrete will reduce the amplitude of the stress field and equally important, will regularize the stress field providing for a smoother load distribution that will diffuse stress concentrations. Consequently, the High Strength Reduced Modulus (HSRM) concrete improves the cracking resistance and fatigue performance, thus extending the life of the tie. A comprehensive research program has been conducted at USC to identify the benefits of using HSRM in concrete ties. The research is based on experimental investigations and computer simulations at the material, component and structural member levels. This work presents the details of the computer simulation studies that pertain to center binding conditions. Three-dimensional nonlinear Finite Element (FE) models have been developed for the HSRM and the “Standard” concrete ties. Nonlinear material models based on damaged plasticity are implemented. The concrete-steel bond interface is also modeled and discussed. Validation of these models is conducted through comparisons with laboratory testing of prestressed concrete prisms, and it has shown excellent accuracy. Subsequently, a study related to center binding conditions in a tangent track have been conducted. These studies showed that the HSRM concrete tie outperformed the Standard concrete tie in these benchmark tests by (i) showing smoother stress distribution, (ii) delaying the initiation of cracks and (iii) failing at higher ultimate loads. The analysis results are discussed and future recommendations presented.
Improved Truck Castings
Authors: Jones Kerry , DeGeorge Matt , Stewart Monique
Published: June 2018

This paper examines alternative, improved materials for truck castings. The first part looks at steels that would not require post-weld heat treatment after repair welding. The second part investigates specific applications for temperatures below −50 °F.

The rapid, dramatic temperature changes that occur during welding can form brittle phases or cracking in some steels. The weld has three areas of differing structure: the weld, the heat affected zone (HAZ), and the parent metal. The maximum hardness occurs in the HAZ and is the limiting factor in determining weldability. An ultraweldable steel is a steel that does not require post-weld heat treatment. Many steels were evaluated for their chemical composition and susceptibility to cracking; those that were likely to form brittle phases were eliminated from consideration. Four low alloy steels and one carbon steel were selected as being potentially ultraweldable.

To evaluate the ultraweldability of these steels, groove welds and two types of spot welds were made on the five candidate alloys. The welds were then sectioned and prepared for microstructural and microhardness evaluation. Microhardness readings were taken across the weld, spanning the weld, HAZ, and base material.

Three of the steels formed hard, brittle phases during most of the tests. This indicates these materials are not ultraweldable. Two of the low alloy steels did meet the requirements for ultraweldability. Future work in this area would include producing truck castings from these materials.

At low temperatures, plain carbon steels, such as the types used in truck castings, can fracture in a brittle manner, with no visible deformation. The material property of deforming without fracture is toughness or ductility. Using materials that retain their toughness in low temperatures could prevent brittle failures of truck castings. Six grades of steel currently used in low temperature applications were selected for this research.

Specimens from each of the six materials were evaluated for tensile properties at multiple temperatures. Charpy impact specimens were tested at temperatures ranging from −20 °F to −120 °F. The measured room temperature tensile properties of each of the six steels met or exceeded the requirements for Grade B+, the steel currently used for truck castings. Four of the steels showed impact energies far above that of the current Grade B+, but two of them gave consistently higher impact energies than all others. These would be the best candidates for future work in this area. Future work would involve producing full size truck castings from one or more of these alloys, then testing them for fatigue performance, preferably at low temperatures.
Locomotive Crash Energy Management Coupling Tests
Authors: Llana Patricia , Jacobsen Karina
Published: June 2018

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. These components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment.

Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. Push-back couplers (PBCs) are designed with trigger loads meant to exceed the expected maximum service loads experienced by conventional couplers. Analytical models are typically used to determine these required trigger loads. Two sets of coupling tests have been conducted to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive retrofit with a push-back coupler. These tests will allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests.

The coupling tests of a conventional locomotive have been conducted, the results of which compared favorably with pre-test predictions. This paper describes the results of the CEM-equipped locomotive coupling tests. In this set of tests, a moving CEM locomotive was coupled to a standing cab car. The primary objective was to demonstrate the robustness of the PBC design and determine the impact speed at which PBC triggering occurs. The coupling speed was increased for each subsequent test until the PBC triggered. The coupling speeds targeted for the test were 2 mph, 4 mph, 6 mph, 7 mph, 8 mph, and 9 mph. The coupling speed at which the PBC triggered was 9 mph. The damage observed resulting from the coupling tests is described. Prior to the tests, a lumped-mass model was developed for predicting the longitudinal forces acting on the equipment and couplers. The test results are compared to the model predictions. Next steps in the research program, including future full-scale dynamic tests, are discussed.
Investigation of the Exposure From a Realistic Undercar Fire on a Railcar Floor
Authors: DiDomizio M. J. , Luo C. , Yazdani S. , Lattimer B.
Published: June 2018

The objective of this research is to use testing and modeling to quantify realistic exposure fires under a railcar and compare these exposures to those in a fire resistance test. A series of tests were conducted on a railcar floor mockup, scaled to 40% of a full railcar width, exposed to fire from below. Two fires were considered, one representing a 1.9 MW diesel fire (e.g. resulting from a ruptured fuel tank) and another representing a 0.3 MW trash fire (e.g. resulting from a collection of trash and debris under the railcar). Two geometric configurations were tested including a floor with equipment box obstructions and a flat floor without undercar obstructions. For the diesel fire, the heat flux directly above the fire reached 75 kW/m2 for the flat configuration and 95 kW/m2 for the obstructed configuration, while gas temperatures directly above the fire reached 750°C and 950°C, respectively. Temperatures and heat flux varied greatly over the floor geometry for the realistic fires, resulting in thermal gradients that are not characteristic of a fire resistance test.

Computational fluid dynamics simulations were used to model these different fire exposures under the railcar floor mockup as tested. The fire dynamics predicted were consistent with those measured. In the region of the mockup where the fire plume impinges, heat flux was predicted to within 11–22% of that measured. In the surrounding regions of the mockup, heat flux was predicted to within 22–40% of measured values. This level of agreement is appropriate for large-scale fire experiments, and the results demonstrate that the model is validated for use in the configurations considered in this study.
Ballast Support Condition Affecting Crosstie Performance Investigated Through Discrete Element Method
Authors: Hou Wenting , Feng Bin , Li Wei , Tutumluer Erol
Published: June 2018

This paper reports on the ballast layer mesoscale behavior, tie-ballast interaction, and ballast-subgrade interaction under five crosstie support conditions, namely full support, lack of rail seat support, lack of center support, high center binding, and severe center binding condition. Discrete Element Method, an effective technique to study particulate natured unbound aggregate materials, i.e., ballast, was adopted in this study. The DEM simulations included one-tie spacing geometry, approximately 11,000 polyhedral particles. The ballast gradation used in DEM models was according to the AREMA No. 3 and No. 4A specifications. The shape properties of ballast particles in DEM models was consistent with field collected samples. The pressure distributions along tie-ballast interface under rail seat load of 10-kips predicted by DEM simulations were in good agreement with the results backcalculated from laboratory tests, which validated the DEM models. Next, DEM simulations considered rail seat loads of 20-kips and 25-kips. The predicted results indicated that support condition is a key factor for predicting normal stress distribution and force transmission within ballast layer. Ballast particles in shoulders and areas with poor support indicated low or negligible contact stresses. Extremely high normal stresses observed in some support conditions often exceeded single particle crushing load limit and thus would cause ballast particle breakage and layer degradation under repeated loading. Further, the tie-ballast pressure captured in some scenarios could be higher than allowable maximum pressure of 85-psi under concrete tie in AREMA standard. Finally, the pressure at bottom of the ballast layer obtained from the DEM simulations were compared with top of subgrade pressure calculated from analytical/empirical equations such as Talbot equation and AREMA manual.
Steady-state anti-plane shear wave scattering by a crack with friction
Authors: Maruyama Taizo , Touhei Terumi
Published: June 2018

The present article describes the steady-state numerical modeling of anti-plane shear wave scattering by a crack with frictional boundary conditions. The system is composed of an unbounded elastic solid that includes a closed crack under static compressive stress. A time-harmonic anti-plane shear wave is incident, and dynamic friction between the crack faces is induced as a nonlinear phenomenon. The anti-plane wave scattering can be described in a retarded potential integral equation by taking the nonlinearity into account. The present article introduces the steady-state expression as an asymptotic vibration of crack faces after a sufficient elapsed time. In order to solve the equations describing nonlinear steady-state vibration, a harmonic balance method is integrated into a boundary element method. Fourier coefficients of crack opening displacement distributed on the crack face are treated as unknown variables. The system of nonlinear equations is solved by means of a numerical continuation method. The present numerical results show almost complete agreement with those obtained by the conventional time-domain analysis after a sufficient elapsed time. Furthermore, the robustness and effectiveness of the proposed method are demonstrated numerically.
Status symbol
Authors: Cohen Jon
Published: June 2018

Pavel Lobkov's decision to announce his HIV status on TV.
Synapse-specific representation of the identity of overlapping memory engrams
Authors: Abdou Kareem , Shehata Mohammad , Choko Kiriko , Nishizono Hirofumi , Matsuo Mina , Muramatsu Shin-ichi , Inokuchi Kaoru
Published: June 2018

Disentangling specific memories

Each memory is stored in a distinct memory trace in the brain, in a specific population of neurons called engram cells. How does the brain store and define the identity of a specific memory when two memories interact and are encoded in a shared engram? Abdou
et al.
used optogenetic reactivation coupled with manipulations of long-term potentiation to analyze engrams that share neurons in the lateral amygdala (see the Perspective by Ramirez). Synapse-specific plasticity guaranteed the storage and the identity of individual memories in a shared engram. Moreover, synaptic plasticity between specific engram assemblies was necessary and sufficient for memory engram formation.

Science
, this issue p.
1227
; see also p.
1182
Long Noncoding RNA ITPRIP-1 Positively Regulates the Innate Immune Response through Promotion of Oligomerization and Activation of MDA5
Authors: Xie Qinya , Chen Shengwen , Tian Renyun , Huang Xiang , Deng Rilin , Xue Binbin , Qin Yuwen , Xu Yan , Wang Jingjing , Guo Mengmeng , Chen Jinwen , Tang Songqing , Li Guangdi , Zhu Haizhen
Published: June 2018

Hepatitis C virus infection is a global health issue, and there is still no available vaccine, which makes it urgent to reveal the underlying mechanisms of HCV and host factors. Although RIG-I has been recognized as the leading cytoplasmic sensor against HCV for a long time, recent findings that MDA5 regulates the IFN response to HCV have emerged. Our work validates the significant role of MDA5 in IFN signaling and HCV infection and proposes the first lncRNA inhibiting HCV replication by promoting the activation of MDA5 and mediating the association between MDA5 and HCV RNA, the study of which may shed light on the MDA5 function and treatment for hepatitis C patients. Our suggested model of how lncITPRIP-1 orchestrates signal transduction for IFN production illustrates the essential role of lncRNAs in virus elimination.
Regulation of Herpes Simplex Virus 2 Protein Kinase UL13 by Phosphorylation and Its Role in Viral Pathogenesis
Authors: Koyanagi Naoto , Kato Akihisa , Takeshima Kosuke , Maruzuru Yuhei , Kozuka-Hata Hiroko , Oyama Masaaki , Arii Jun , Kawaguchi Yasushi
Published: June 2018

Based on studies on cellular protein kinases, it is obvious that the regulatory mechanisms of protein kinases are as crucial as their functional consequences. Herpesviruses each encode at least one protein kinase, but the mechanism by which these kinases are regulated in infected cells remains to be elucidated, with a few exceptions, although information on their functional effects has been accumulating. In this study, we have shown that phosphorylation of the HSV-2 UL13 protein kinase at Ser-18 regulated its function in infected cells, and this regulation was critical for HSV-2 replication and pathogenesis
in vivo
. UL13 is conserved in all members of the family
Herpesviridae
, and this is the first report clarifying the regulatory mechanism of a conserved herpesvirus protein kinase that is involved in viral replication and pathogenesis
in vivo
. Our study may provide insight into the regulatory mechanisms of the other conserved herpesvirus protein kinases.