bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence ofSalmonellaamong waterfowl along the Texas Gulf coast
Authors: Grigar M. K. , Cummings K. J. , Rankin S. C.
Published: July 2017

Migratory waterfowl may play a role in the ecology and transmission of zoonotic pathogens, given their ability to travel long distances and their use of varied habitats. Our objectives were to estimate the prevalence ofSalmonellaamong waterfowl along the Texas Gulf coast and to characterize the isolates. Faecal samples were collected from hunter‐harvested waterfowl at four wildlife management areas from September through November, 2016. Standard bacteriologic culture methods were used to isolateSalmonellafrom samples, and isolates were characterized by serotyping and anti‐microbial susceptibility testing. The apparent prevalence of faecalSalmonellashedding was 0.5% (2/375). Serotypes identified were Thompson and Braenderup, and both isolates were susceptible to all anti‐microbial agents tested. Although faecal contamination of agricultural fields or surface waters could serve as a potential source of zoonoticSalmonellatransmission, waterfowl along the Gulf coast during the fall hunting season appear to pose minimal risk.
A Survey of Modeling of Lattice Structures Fabricated by Additive Manufacturing
Authors: Dong Guoying , Tang Yunlong , Zhao Yaoyao Fiona
Published: July 2017

The lattice structure is a type of cellular material with trusslike frames which can be optimized for specific loading conditions. The fabrication of its intricate architecture is restricted by traditional manufacturing technologies. However, additive manufacturing (AM) enables the fabrication of complex structures by aggregation of materials in a layer-by-layer fashion, which has unlocked the potential of lattice structures. In the last decade, lattice structures have received considerable research attention focusing on the design, simulation, and fabrication for AM techniques. And different modeling approaches have been proposed to predict the mechanical performance of lattice structures. This review introduces the aspects of modeling of lattice structures and the correlation between them, summarizes the existing modeling approaches for simulation, and discusses the strength and weakness in different simulation methods. This review also summarizes the characteristics of AM in manufacturing cellular materials and discusses their influence on the modeling of lattice structures.
FRA Training Requirements
Authors: Schlesinger Dave
Published: July 2017

Training represents a unique opportunity to engage employees and mold their behavior to that desired by the organization and required by regulation. It is also an opportunity to reduce human factor causes of accidents through the proper application of training best practices. Underscoring the importance of comprehensive training programs, in 49 Code of Federal Regulations (CFR) Part 243, the Federal Railroad Administration (FRA) has established training requirements for safety-sensitive railroad employees. These include the requirement that railroads and railroad contractors submit to the Federal Railroad Administration a training program for review and approval. In addition to meeting regulatory requirements, comprehensive training programs can usher in broad safety improvements, reduce delays, as well as improve operational and organizational efficiency. Related to employee safety and training, this paper also discusses the importance of crew resource and fatigue management plans.
A Framework for Defining a Sustainability Rating System for Railway Track-Beds
Authors: Bressi Sara , Di Mino Gaetano , Lo Presti Davide
Published: July 2017

Railways perform a significant role in the transportation system and they have relevant environmental, economic and social impacts. They are currently engineered optimizing every singular aspect rather than considering a broader system for improving the sustainability of the overall infrastructure. Thus, it is necessary to promote an effort to define a global sustainability framework for conceiving the design, construction and management of railway infrastructure. The Sustainable Rating System (SRS) proposed in this paper is a tool under development that evaluates different alternatives of railway track-bed structure. Inspired by similar efforts in the field of road engineering such as Greenroads and Greenpave, this SRS aims to be the first entirely dedicated to support railway engineers, designers and managers in taking more responsible decisions with regards to the sustainable design and maintenance of railway track-beds. It is based on a library that examines different solutions and treatments for each element of the track-bed and a table of points that assigns different scores to the different alternatives. To achieve the highest score in terms of sustainability it is necessary to maximize the points assigned to every element. In other words, the maximum score requires adopting best practices leading to more sustainable choices such as exploiting the use of recycled materials, reducing the use of non-renewable resources, the energy consumption, air pollutants and greenhouse gas emissions.
Probabilistic Analysis of Flying Ballast on High-Speed Rail Lines
Authors: Deng Jieyi , Jing Guoqing , Liu Xiang
Published: July 2017

Safety is a top priority for the development of worldwide high-speed rail systems. Ballast flying is a particular safety concern when a high-speed train is traveling above a certain speed on the ballasted track. Displaced ballast particles from the track may cause damages to rolling stock, as well as the track infrastructure and wayside structures close to the sides of way. The objective of this research is to develop a probabilistic modeling framework to estimate the probability of ballast flight on specific segments or routes, accounting for several principal risk factors. Based on the probabilistic assessment, we propose a methodology to quantify the probability of flying ballast under certain scenarios. The methodology can be further developed, ultimately enabling a normative risk assessment for flying ballast risk management.
Secure Intelligent Radio for Trains (SIRT)
Authors: Bandara K. R. Damindra S. , Kolli Satish , Wijesekara Duminda
Published: July 2017

American Railroads are planning to complete implementing their Positive Train Control (PTC) systems by 2020. Safety objectives of PTC are to avoid inter-train collisions, train derailments and ensuring railroad worker safety. Under published specifications of I-ETMS (the PTC system developed by Class I freight railroads), the on-board PTC controller communicates with two networks; namely, the Signaling network and the Wayside Interface Unit network to gather navigational information such as the positions of other trains, the status of critical infrastructure (such as switches) and any hazardous conditions that may affect the train path. By design, PTC systems are predicated on having a reliable radio network operating in reserved radio spectrum, although the PTC system itself is designed to be a real-time fail safe distributed control systems. Secure Intelligent Radio for Trains (SIRT) is an intelligent radio that is customized to train operations with the aim of improving the reliability and security of the radio communication network.

SIRT has two tiers. The upper tier has the Master Cognitive Engine (MCE) which communicates with other SIRT nodes to obtain signaling and wayside device information. To do so, the MCE communicates with cognitive engines at the lower tier of SIRT; namely the Cryptographic Cognitive Engine (CCE) (that provide cryptographic security and threat detection) and the Spectrum Management Cognitive Engine (SCE) (that uses spectrum monitoring, frequency hopping and adaptive modulation to ensure the reliability of the radio communication medium). We presented the architecture and the prototype development of the CCE in [1]. This paper presents the design of the MCE and the SCE.

We are currently developing a prototype of the SCE and the MCE and testing the performance of our cognitive radio system under varying radio noise conditions. Our experiments show that SIRT dynamically switches modulation schemes in response to radio noise and switches channels in response to channel jamming.
Locomotive Crash Energy Management Coupling Tests
Authors: Llana Patricia , Tyrell David
Published: July 2017

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 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 are planned 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. In the coupling tests of a CEM-equipped locomotive, the coupling speed for which the push-back coupler (PBC) triggers will be measured. A moving, CEM-equipped locomotive will be coupled to a standing cab car. The coupling speed for the first test will be low, approximately 2 mph. The test will then be repeated with the speed increasing incrementally until the PBC triggers.

This paper describes the fabrication, retrofit, test requirements, and analysis predictions for the CEM coupling tests. The equipment to be tested, track conditions, test procedures, and measurements to be made are described. A model for predicting the longitudinal forces acting on the equipment and couplers has been developed, along with preliminary predictions for the CEM coupling tests.
A Study on Subgrade Pressure Differential Over Regions of Known Substructure Transition as it Relates to Track Geometry
Authors: Palese Joseph W. , Zarembski Allan M. , Hartsough Christopher M. , Thompson Hugh , Palese Michael E.
Published: July 2017

The support structure beneath railroad tracks may appear to be a simple layering of various materials, but rather, it is a complex system working together to distribute the load of passing trains. It is paramount that this structure maintain its designed support properties not only to preserve component life expectancy but to maintain the safety of the trains traveling over the rails.

During normal operations, track geometry, as evaluated through the standard deviation of various track geometry channels, tends to degrade over time. This is a byproduct of the cyclical loading applied to the track structure by passing trains causing the slow compacting and settling of the ballast and sub-structure. Assuming all variables are held constant, a regular maintenance schedule should bring track geometry back into acceptable limits, but this is generally not the case in real life. In the event that the subgrade cannot support and distribute the pressure caused from the passing train successfully, accelerated track geometry degradation can take place. This accelerated degradation can be further increased when there exists a transition between support strengths which can lead to increased dynamic loading.

A case study in sub-structure pressure management has been devised and applied to a high speed rail line. During a recent track renewal operation where track was maintained down to the subgrade, pressure transducers were placed within the sub-grade layer under both the left and right rails, inside and outside of track regions where sub-structure management has been applied. This test segment was monitored over a period of one year with both pressure and track geometry data being recorded at regular intervals.

This paper will explore the relationship between sub-structure pressure and local track geometry measurements as it relates to the monitored test segment with a region of known subgrade management transition. Numerous numerical techniques will be applied to understand the change over time of the subgrade pressure distribution capability (measured as pressure beneath the rail) and the degradation of various track geometry channels individually over time. Correlation of the pressure data to track geometry data will also be done using both raw data and data processed using numerical techniques. This will lead to an understanding of how the quality of the track support structure, specifically the track support structure’s ability to distribute pressure, can affect the magnitude and degradation rates of various track geometry channels.
A Human Factors-Based ICrossing System
Authors: Fayerweather Andrew , Smith Ryan , Fillman David , Huang Hai
Published: July 2017

Highway-rail crossing protection has perpetually been a problem for railroads and road owners. Of roughly 422,000 [1] highway-rail grade crossings in the Unites States, nearly half are passive crossings utilizing only signs and other non-active warning devices. ICrossing is a system designed to protect these passive crossings and warn motorists of approaching trains. ICrossing utilizes a system of beacons and detectors connected to a central computer. The detectors located down the track on either side of the crossing detect oncoming trains and alerts that central computer. The central computer then generates a warning message which is sent to the IBeacons that are placed on the approaches to the crossing. The beacons broadcast the generated message to the surrounding area and alert motorists to the oncoming train through a mobile application on their cell phones. This system is expected to be a cheap form of protection that can add another level of protection to many of the passive crossings located throughout the country.
Influence of Fouling and Water Content of Ballast on Railway Substructure Bearing Capacity
Authors: Rohrman A. K. , Kashani H. F. , Ho C. L.
Published: July 2017

The performance of ballasted railway systems is commonly compromised by the infiltration of fine material into the voids of the ballast. This sand and finer grained materials in the ballast is known as fouling. Increased fouling can cause decreases in hydraulic conductivity and shear strength of the ballast, as well as reduce stiffness and resilient modulus of the overall track system. These problems can cause gradual deterioration of the track, which could eventually require maintenance. One of the largest source of fouling comes from ballast breakdown resulting from abrasion caused under repeated loading. This study aims to investigate the effects of fouling from ballast breakdown on the bearing capacity of the substructure that supports the rail superstructure. Previous investigations at the University of Massachusetts Amherst utilized large scale 10-inch (25.4 cm) diameter triaxial tests on granitic ballast with fouling from ballast breakdown. The tests were run with fouling contents of 0% (clean ballast), 15%, and 30% and at water contents varying from dry ballast to field capacity. Confining pressures of 5 psi (34.5 kPa), 10 psi (68.9 kPa) and 15 psi (103.4 kPa) were used in this series of tests. Using the results from these tests, the Mohr-Coulomb strength properties can be determined for each case. This study will make use of the strength properties obtained from the results of these tests and apply them using two commonly used bearing capacity analyses. The first model is the Meyerhof and Hanna Method which considers the track as a continuous footing over a layered system. This model considers two modes of failure; punching of an individual sleeper, and track system bearing. The second model applied is the slope stability method, which uses a two-dimensional limit equilibrium approach and the method of slices to determine a factor of safety against slope stability. This analysis is commonly performed using various software programs. In this study, SLOPE/W from the GeoStudio software package is utilized for analysis. The factors of safety resulting from the bearing capacity analysis using these two methods will be compared for each of the test configurations performed, which will help to confirm the results of the analyses. Since the Mohr-Coulomb strength properties change with the degree of fouling and the water content of the ballast, it is expected that this will have some effect on the bearing capacity of the track substructure. The results of these analyses showing the effects of water content and fouling of ballast on overall track substructure bearing capacity are presented in this paper.
Determining the Remaining Prestress Force in a Prestressed Concrete Crosstie
Authors: Scott James D. , Robertson Aaron A. , Peterman Robert J. , Beck B. Terry , Riding Kyle A. , Wu John
Published: July 2017

The research presented herein focuses on determining the amount of internal prestressing force and bending resistance that is necessary to provide a durable long-term concrete railroad tie. In order to accomplish this, the researchers conducted a systematic evaluation of existing concrete ties that successfully withstood over 25 years of service in track. An experimental method for determining the remaining prestress force in these existing prestressed concrete railroad ties is currently under development.

The ties are first loaded in the upside-down orientation, with supports located at the rail seats, and two point loads applied at the center of the tie. A loading rate of 1,000 lb/min was used to initiate flexural cracking in the center of the tie. Once cracking was observed, the ties underwent 200 cycles of loading to reduce the friction between the prestressing tendons and the concrete. When the cycling was completed, the existing crack was instrumented with an extensometer to measure the Crack Opening Displacement (COD). The ties were loaded once more at 1,000 lb/min to develop a Load vs. COD relation.

A systematic method of determining the load required to reopen the crack from the Load vs. COD relation is being developed using ties cast at a manufacturing plant that were instrumented with internal vibrating-wire strain gages. Using the load required to reopen the crack, along with the known cross-sectional properties at the center of the tie, the remaining prestress force is calculated through equilibrium of forces. This method allows for the determination of the remaining prestress force in a member with known section properties to be obtained through load testing.
Onboard Energy Storage System: Ground Fault Detection and Protection
Authors: Krause Jason , McPhee John
Published: July 2017

Several Authorities are procuring Hybrid Streetcars with OESS. The energy storage system needs to be protected from ground faults, external and internal to the vehicle. A Hybrid Streetcar has an OESS consisting of either Lithium Batteries or super capacitors, with an OESS converter connected to, or integrated with, the Traction Inverter. During a ground fault of the high voltage circuit, the freewheeling diode in an OESS charger creates a fault path between the energy storage elements and ground.

Typical vehicle designs use a fuse for catastrophic protection, depending on the vehicle ground fault scheme for detection and protection. The vehicle’s primary ground fault detection device is an HSCB, usually connected between the shop switch and traction inverter; the auxiliary inverter is typically protected using a fuse. An HSCB is able to protect typical fault currents seen within the traction chain, but is not designed for OESS fault currents. If a fault occurs the fuse for the catastrophic protection of the OESS will blow before the HSCB will trip, potentially damaging equipment, making the vehicle inoperable. This paper compares alternative methods which can be deployed to detect and protect the OESS from a ground fault.
Accuracy of High Resolution 3D Optical Scanning of Crosstie Geometry for Assessment of Cross-Sectional Parameters and Long-Term Abrasion and Wear
Authors: Beck B. Terry , Robertson Aaron A. , Peterman Robert J. , Riding Kyle A. , Wu John
Published: July 2017

Current research is attempting to develop a comprehensive understanding of the material and manufacturing characteristics that have caused splitting failures in prestressed concrete railroad ties, in contrast with those characteristics that have resulted in ties that have performed well after many years in track. As part of this effort, a three-dimensional (3D) Optical Scanning System is being used to accurately scan and quantify the surface geometry and volume (abrasion and wear) of a large sample of previously manufactured ties. A commercially-available 3D Laser-Based Optical Scanning System, having a maximum spatial resolution of approximately 0.1mm, is being used to perform the surface scanning operation. The scanning procedure ideally produces an accurate 3D CAD model of the tie geometry, which can then be analyzed to determine the desired geometrical features at any given cross-section. It can likewise yield a measure of the tie volume, the variation of which gives some direct indication of the extent of abrasion and wear.

The feasibility of the scanning system has previously been demonstrated by extracting the detailed longitudinal variation of geometrical cross-section crosstie parameters of a typical CXT tie, including cross-sectional area, centroid, moment of inertia, and the eccentricity of the prestressing wires. These parameters are also known to be of importance to the accurate determination of transfer length from measured surface strain. The CXT tie geometry provides an excellent test case, and a challenge to the optical scanning system, since it has a complex scalloping along its length.

While the basic feasibility of the system operation has been demonstrated, the repeatability of the geometrical information obtained from the overall scanning and subsequent post-processing of surface geometrical data has yet to be assessed.

The main objective of this paper is to first demonstrate the volumetric measurement resolution experimentally by conducting repeated scans of the same tie by the same operator. The experimental scatter in scan results is presented for both cross-section parameter detail and tie volume assessment. The statistical variation in the measured tie volume ideally provides a reasonable measure of the expected volume resolution. In addition to assessing the statistics of these repeated scans, a CXT tie was subjected to induced abrasions of known (measurable) volume for direct comparison with the volume measurements obtained using the optical scanning procedure. This work represents an important next step toward identifying the accuracy of the assessment of abrasion and wear for the large number of ties currently being scanned after having been in long-term service.
A Review of Developing Railcar Design Fires for Smoke Control System Design
Authors: Lattimer Brian Y. , Ferreira Michael
Published: July 2017

Rail tunnel and station smoke control system designs typically consider a fully-developed fire from a railcar as a worst case, credible fire scenario. This paper provides the results of a review and assessment of the methods used to estimate the heat release rate of a fully-developed fire inside of a railcar. The review includes large and scaled railcar testing data as well as a range of modeling techniques. Important factors affecting the railcar heat release rate are discussed along with an assessment of the current methods for estimating the railcar heat release rate.
Recent Experience on Guideway Intrusion Detection System Implementations
Authors: Schütte Jörg , Scholz Sven
Published: July 2017

During the last decade, several Public Transportation Operators have started to test and implement technical equipment that shall detect passengers or objects intruding the clearance profile of trains in the station area. The deployed or tested systems typically supervise the track area of subways or light rails and shall stop incoming trains if an obstacle has been detected on the tracks (Guideway Intrusion Detection System, GIDS).

While some scientific and operational publications can be found in the literature for Onboard Obstacle Detection Systems and on different technical solutions for Guideway Intrusion in general, there are virtually none on planning and operations experience for Wayside GIDS in transit applications.

The paper therefore reports on the basic intention and operation of (wayside) GIDS in Unmanned and Driver Operations and findings about detection efficiency and feasibility. Some critical issues had been observed in most implementations and will be discussed in this overview paper.

TelSys GmbH has been working with researchers from TU Dresden on Video GIDS Technology in multiple installations, accumulated substantial statistics of GIDS behavior in diverse field demonstrators (Prague, Berlin, New York City, Munich) and assessed the operational results of GIDS technologies over the years. The Video GIDS is therefore introduced as an illustration example, while the considered aspects are applicable to all GIDS Technologies.
New ameroid mites (Acari, Oribatida) from the Philippines
Authors: Ermilov Sergey G. , Corpuz-Raros Leonila
Published: July 2017

Two new species of oribatid mites of the superfamily Ameroidea (Acari, Oribatida) are described from the Philippines. Heterobelba quezonica sp. nov. (Heterobelbidae) is most similar to H. stellifera stellifera Okayama, 1980 and H. stellifera formosana Aoki, 1990, but differs by the pointed median tooth of the rostrum and exuvial setae Elp, Elm, Ep2 being clearly longer than the other setae. Oxyamerus isabelaensis sp. nov. (Oxyameridae) is most similar to O. hauserorum Mahunka, 1987, but differs by having bifurcate notogastral setae and adanal setae ad2, short lamellar setae and phylliform aggenital setae. Revised generic diagnoses of Heterobelba and Oxyamerus are presented.
Global loudness of rising- and falling-intensity tones: How temporal profile characteristics shape overall judgments
Authors: Ponsot Emmanuel , Susini Patrick , Meunier Sabine
Published: July 2017

The mechanisms underlying global loudness judgments of rising- or falling-intensity tones were further investigated in two magnitude estimation experiments. By manipulating the temporal characteristics of such stimuli, it was examined whether judgments could be accounted for by an integration of their loudest portion over a certain temporal window associated to a “decay mechanism” downsizing this integration over time for falling ramps. In experiment 1, 1-kHz intensity-ramps were stretched in time between 1 and 16 s keeping their dynamics (difference between maximum and minimum levels) unchanged. While global loudness of rising tones increased up to 6 s, evaluations of falling tones increased at a weaker rate and slightly decayed between 6 and 16 s, resulting in significant differences between the two patterns. In experiment 2, ramps were stretched in time between 2 and 12 s keeping their slopes (rate of change in dB/s) unchanged. In this context, the main effect of duration became non-significant and the interaction between the two profiles remained, although the decay of falling tones was not significant. These results qualitatively support the view that the global loudness computation of intensity-ramps involves an integration of their loudest portions; the presence of a decay mechanism could, however, not be attested.
A hybrid deconvolution approach to separate acoustic sources in multiple motion modes
Authors: Mo Pinxi , Jiang Weikang
Published: July 2017

Motion mode is defined as a characteristic motion that a group of sources follow. If there are multiple groups of sources moving in the corresponding multiple motion modes, the beamforming map for a certain group of sources will be contaminated by the leakages from the other groups of sources. The original beamforming or deconvolution approaches fail to interpret the acoustic maps, as the source leakages may be mistaken for actual sources. A hybrid deconvolution approach is proposed to restrain the source leakages, so as to separate the acoustic sources in multiple motion modes. This approach simultaneously considers all the sources in the potential motion modes, and introduces equivalent sources in the corresponding motion modes to represent the sources. The equivalence between the actual sources and the equivalent sources leads to the construction of an expanded linear matrix equation. The sources in the respective motion modes are simultaneously extracted by solving the equation. The approach is shown effective by two numerical simulations and a practical experiment on two counter-rotating sources and one static source.
Trump's science shop is small and waiting for leadership
Authors: Mervis Jeffrey
Published: July 2017

White House office has so far played little role in policy
Mouse models of acute and chronic hepacivirus infection
Authors: Billerbeck Eva , Wolfisberg Raphael , Fahnøe Ulrik , Xiao Jing W. , Quirk Corrine , Luna Joseph M. , Cullen John M. , Hartlage Alex S. , Chiriboga Luis , Ghoshal Kalpana , Lipkin W. Ian , Bukh Jens , Scheel Troels K. H. , Kapoor Amit , Rice Charles M.
Published: July 2017

New York City rats provide a gift to virologists

Despite the development of curative drugs for hepatitis C virus (HCV) infection, global eradication of HCV will likely require a prophylactic vaccine. Progress toward a vaccine has been impeded by the absence of mouse models suitable for studying the immune response to HCV. Billerbeck
et al.
found that a HCV-related virus isolated from New York City rats produces an infection in laboratory mice that shares several immunological features with human infections (see the Perspective by Klenerman and Barnes). Their initial analyses of the infected mice revealed that acute clearance of the virus was dependent on T cells but not on natural killer cells.

Science
, this issue p.
204
; see also p.
129
Effects of network modularity on the spread of perturbation impact in experimental metapopulations
Authors: Gilarranz Luis J. , Rayfield Bronwyn , Liñán-Cembrano Gustavo , Bascompte Jordi , Gonzalez Andrew
Published: July 2017

Modularity limits disturbance effects

The networks that form natural, social, and technological systems are vulnerable to the spreading impacts of perturbations. Theory predicts that networks with a clustered or modular structure—where nodes within a module interact more frequently than they do with nodes in other modules—might contain a perturbation, preventing it from spreading to the entire network. Gilarranz
et al.
conducted experiments with networked populations of springtail (
Folsomia candida
) microarthropods to show that modularity limits the impact of a local extinction on neighboring nodes (see the Perspective by Sales-Pardo). In networks with high modularity, the perturbation was contained within the targeted module, and its impact did not spread to nodes beyond it. However, simulations revealed that modularity is beneficial to the network only when perturbations are present; otherwise, it hinders population growth.

Science
, this issue p.
199
; see also p.
128
Ravens parallel great apes in flexible planning for tool-use and bartering
Authors: Kabadayi Can , Osvath Mathias
Published: July 2017

Making a plan

Until recently, planning for the future has generally been considered to be
unique to humans. Studies in the past 10 years have suggested that apes and
scrub jays are also able to make such plans. However, these
studies—especially those in the birds—have been questioned. It has
been argued that planning in foraging and natural tasks is not the same as
planning in a more general way. Kabadayi
et al.
tested ravens
with tasks designed to specifically assess their general planning abilities (see
the Perspective by Boeckle and Clayton). Confirming their forward-planning
abilities, the birds performed at least as well as apes and small children in
this complex cognitive task.

Science
, this issue p.
202
; see also p.
126
Driving improvements in emerging disease surveillance through locally relevant capacity strengthening
Authors: Halliday Jo E. B. , Hampson Katie , Hanley Nick , Lembo Tiziana , Sharp Joanne P. , Haydon Daniel T. , Cleaveland Sarah
Published: July 2017

Emerging infectious diseases (EIDs) threaten the health of people, animals, and crops globally, but our ability to predict their occurrence is limited. Current public health capacity and ability to detect and respond to EIDs is typically weakest in low- and middle-income countries (LMICs). Many known drivers of EID emergence also converge in LMICs. Strengthening capacity for surveillance of diseases of relevance to local populations can provide a mechanism for building the cross-cutting and flexible capacities needed to tackle both the burden of existing diseases and EID threats. A focus on locally relevant diseases in LMICs and the economic, social, and cultural contexts of surveillance can help address existing inequalities in health systems, improve the capacity to detect and contain EIDs, and contribute to broader global goals for development.
Pseudomonas aeruginosa
Alters
Staphylococcus aureus
Sensitivity to Vancomycin in a Biofilm Model of Cystic Fibrosis Infection
Authors: Orazi Giulia , O’Toole George A.
Published: July 2017

The airways of cystic fibrosis (CF) patients have thick mucus, which fosters chronic, polymicrobial infections.
Pseudomonas aeruginosa
and
Staphylococcus aureus
are two of the most prevalent respiratory pathogens in CF patients. In this study, we tested whether
P. aeruginosa
influences the susceptibility of
S. aureus
to frontline antibiotics used to treat CF lung infections. Using our
in vitro
coculture model, we observed that addition of
P. aeruginosa
supernatants to
S. aureus
biofilms grown either on epithelial cells or on plastic significantly decreased the susceptibility of
S. aureus
to vancomycin. Mutant analyses showed that 2-
n
-heptyl-4-hydroxyquinoline
N
-oxide (HQNO), a component of the
P. aeruginosa Pseudomonas
quinolone signal (PQS) system, protects
S. aureus
from the antimicrobial activity of vancomycin. Similarly, the siderophores pyoverdine and pyochelin also contribute to the ability of
P. aeruginosa
to protect
S. aureus
from vancomycin, as did growth under anoxia. Under our experimental conditions, HQNO,
P. aeruginosa
supernatant, and growth under anoxia decreased
S. aureus
growth, likely explaining why this cell wall-targeting antibiotic is less effective.
P. aeruginosa
supernatant did not confer additional protection to slow-growing
S. aureus
small colony variants. Importantly,
P. aeruginosa
supernatant protects
S. aureus
from other inhibitors of cell wall synthesis as well as protein synthesis-targeting antibiotics in an HQNO- and siderophore-dependent manner. We propose a model whereby
P. aeruginosa
causes
S. aureus
to shift to fermentative growth when these organisms are grown in coculture, leading to reduction in
S. aureus
growth and decreased susceptibility to antibiotics targeting cell wall and protein synthesis.

IMPORTANCE
Cystic fibrosis (CF) lung infections are chronic and difficult to eradicate.
Pseudomonas aeruginosa
and
Staphylococcus aureus
are two of the most prevalent respiratory pathogens in CF patients and are associated with poor patient outcomes. Both organisms adopt a biofilm mode of growth, which contributes to high tolerance to antibiotic treatment and the recalcitrant nature of these infections. Here, we show that
P. aeruginosa
exoproducts decrease the sensitivity of
S. aureus
biofilm and planktonic populations to vancomycin, a frontline antibiotic used to treat methicillin-resistant
S. aureus
in CF patients.
P. aeruginosa
also protects
S. aureus
from other cell wall-active antibiotics as well as various classes of protein synthesis inhibitors. Thus, interspecies interactions can have dramatic and unexpected consequences on antibiotic sensitivity. This study underscores the potential impact of interspecies interactions on antibiotic efficacy in the context of complex, polymicrobial infections.
Effect of diet and physical activity based interventions in pregnancy on gestational weight gain and pregnancy outcomes: meta-analysis of individual participant data from randomised trials
Authors:   The International Weight Management in Pregnancy (i-WIP) Collaborative Group
Published: July 2017

Objective

To synthesise the evidence on the overall and differential effects of interventions based on diet and physical activity during pregnancy, primarily on gestational weight gain and maternal and offspring composite outcomes, according to women’s body mass index, age, parity, ethnicity, and pre-existing medical condition; and secondarily on individual complications.

Design

Systematic review and meta-analysis of individual participant data (IPD).

Data sources

Major electronic databases from inception to February 2017 without language restrictions.

Eligibility criteria for selecting studies

Randomised trials on diet and physical activity based interventions in pregnancy.

Data synthesis

Statistical models accounted for clustering of participants within trials and heterogeneity across trials leading to summary mean differences or odds ratios with 95% confidence intervals for the effects overall, and in subgroups (interactions).

Results

IPD were obtained from 36 randomised trials (12 526 women). Less weight gain occurred in the intervention group than control group (mean difference −0.70 kg, 95% confidence interval −0.92 to −0.48 kg, I2=14.1%; 33 studies, 9320 women). Although summary effect estimates favoured the intervention, the reductions in maternal (odds ratio 0.90, 95% confidence interval 0.79 to 1.03, I2=26.7%; 24 studies, 8852 women) and offspring (0.94, 0.83 to 1.08, I2=0%; 18 studies, 7981 women) composite outcomes were not statistically significant. No evidence was found of differential intervention effects across subgroups, for either gestational weight gain or composite outcomes. There was strong evidence that interventions reduced the odds of caesarean section (0.91, 0.83 to 0.99, I2=0%; 32 studies, 11 410 women), but not for other individual complications in IPD meta-analysis. When IPD were supplemented with study level data from studies that did not provide IPD, the overall effect was similar, with stronger evidence of benefit for gestational diabetes (0.76, 0.65 to 0.89, I2=36.8%; 59 studies, 16 885 women).

Conclusion

Diet and physical activity based interventions during pregnancy reduce gestational weight gain and lower the odds of caesarean section. There is no evidence that effects differ across subgroups of women.
Effect of occupational safety and health education received during schooling on the incidence of workplace injuries in the first 2 years of occupational life: a prospective study
Authors: Boini Stephanie , Colin Regis , Grzebyk Michel
Published: July 2017

Objectives

This study aimed to determine the effect of occupational safety and health (OSH) education during formal schooling on the incidence of workplace injuries (WIs) in young people starting their careers. We hypothesised that young people who had received OSH education during their schooling would have fewer WIs than those who received no OSH education. Secondary objectives focused on the effect of ‘first aid at work’ training during schooling and the conditions encountered on arrival in the company (occupational hazard information, safety training and job task training) on WI occurrence.

Design

Prospective cohort study.

Participants

From 2009 to 2012, French apprentices and students at the end of their schooling and starting their careers were included.

Outcomes

Occurrence of WIs.

Methods

At the time of inclusion, information about school courses and personal characteristics were collected, and subsequent half-yearly contacts gathered information relating to work and personal data. During the 2-year follow-up, WIs were directly reported by participants and were identified by searching the French National Health Insurance Funds’ databases listing compulsory WI declarations.

Results

755 participants reported holding 1290 jobs. During follow-up, 158 WIs were identified, corresponding to an incident rate of 0.12 (0.10 to 0.14) WIs per full-time worker. Subjects who reported having received OSH education at school had two times less WIs than those declaring not having received OSH education (incidence rate ratio (IRR) 0.51, 0.00 to 0.98). A lower WI risk was observed for participants who received the ‘first aid at work’ training (IRR=0.68, 0.00 to 0.98). The conditions on arrival in company were not associated with WIs occurrence.

Conclusion

In France, the OSH education provided to apprentices and students is mostly broader than the specific risks related to future jobs. Our results highlight the advantages of reinforcing this approach.
Dark matter candidate with well-defined mass and couplings
Authors: Allen Roland E. , Saha Aritra
Published: July 2017

We propose a Higgs-related but spin-[Formula: see text] dark matter candidate with a mass that is comparable to that of the Higgs. This particle is a weakly interacting massive particle (WIMP) with an R-parity of [Formula: see text], but it can be distinguished from a neutralino by its unconventional couplings to W and Z bosons. Other neutral and charged spin-[Formula: see text] particles of a new kind are also predicted at higher energy.
Linking invariants of even virtual links
Authors: Miyazawa Haruko A. , Wada Kodai , Yasuhara Akira
Published: July 2017

A virtual link diagram is even if the virtual crossings divide each component into an even number of arcs. The set of even virtual link diagrams is closed under classical and virtual Reidemeister moves, and it contains the set of classical link diagrams. For an even virtual link diagram, we define a certain linking invariant which is similar to the linking number. In contrast to the usual linking number, our linking invariant is not preserved under the forbidden moves. In particular, for two fused isotopic even virtual link diagrams, the difference between the linking invariants of them gives a lower bound of the minimal number of forbidden moves needed to deform one into the other. Moreover, we give an example which shows that the lower bound is best possible.
Centralizers in a group whose central factor is simple
Authors: Jafarian Amiri Seyyed Majid , Rostami Hojjat
Published: July 2017

In this paper, we find the number of the element centralizers of a finite group [Formula: see text] such that the central factor of [Formula: see text] is the projective special linear group of degree 2 or the Suzuki group. Our results generalize some main results of [Ashrafi and Taeri, On finite groups with a certain number of centralizers, J. Appl. Math. Comput. 17 (2005) 217–227; Schmidt, Zentralisatorverbände endlicher Gruppen, Rend. Sem. Mat. Univ. Padova 44 (1970) 97–131; Zarrin, On element centralizers in finite groups, Arch. Math. 93 (2009) 497–503]. Also, we give an application of these results.
Assessing accuracy of exchange-correlation functionals for electron affinities
Authors: Pustuła Katarzyna , Makowski Marcin
Published: July 2017

The performance of exchange-correlation (xc) functionals for the description of electron affinities of atomic and molecular systems is investigated. A benchmark set is constructed and experimental adiabatic electron affinities are compared to Density Functional Theory (DFT) predictions. The results show that although good overall accuracy may be achieved from DFT-based approaches, there still exist outliers for any of the approximations applied. Apart from employing the standard DFT models, the possibility of the optimization of range-separated xc functionals has also been tested, however, no large improvement in accuracy is observed.
Mechanistic investigation of the atmospheric reaction of NH2 with NO2 and study of the catalytic effects of water molecule on kinetic path
Authors: Dadi Samira , Vahedpour Morteza
Published: July 2017

The gas-phase reaction mechanism of NO2 with NH2 on the singlet potential energy surface is investigated at the B3LYP, MP2, CCSD(T) and G3B3 levels of calculation in connection with the 6-311[Formula: see text]G(3df, 3pd) basis sets. Seven different kinds of products have been obtained. The results reveal that P7 [N2[Formula: see text]2O] is the main product in thermodynamic viewpoint with the Gibbs free energy of [Formula: see text][Formula: see text]kcal/mol. The product P2 due to less number of transition states and low level barrier height of transition states is introduced as the kinetic product. The calculation of rate constants in different temperatures confirms our predication for P7 adduct in comparison with other products. In the first step, the reactions without catalytic effects are considered. All of these reactions begin with pre-reactive collision complex CR [NO2–NH2]. This complex has been produced from barrier-less process via collision of reactants. From variation of bond lengths and angles or dissociation of this complex, other species are produced. In the second step, the catalytic effect of water and water dimer molecules on the reaction rate of kinetic path, P2, have been attended. Calculation of the rate constant was done in the temperature range from 500[Formula: see text]K to 3000[Formula: see text]K. Our results showed that the rate constant of path P2 increases with temperature and the number of water molecules. So, we can conclude that the number of water molecules corresponding to relative humidity of atmosphere has catalytic effect on the mentioned reaction rate.
Theoretical studies on lindqvist polyoxometalates [M6O19]n−(M = Mo, W, n=2; M = V, Nb, Ta, n=8) and derivatives: Electronic structures, stability and bonding
Authors: Su Xiao-Fang , Zhu Bo , Wu Cai-Xia , Yan Li-Kai , Su Zhong-Min
Published: July 2017

The geometrical and electronic structures of [M6O[Formula: see text]][Formula: see text] (M [Formula: see text] Mo, W, [Formula: see text]; M [Formula: see text] V, Nb, Ta, [Formula: see text]) and their derivatives were investigated by using density functional theory methods. The results indicate that the geometrical structure of [V6O[Formula: see text]][Formula: see text] is not different from other Lindqvist-type anions. The energy gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) (HOMO[Formula: see text]LUMO energy gap) of [V6O[Formula: see text]][Formula: see text] is smaller than those of same charge anions, [Nb6O[Formula: see text]][Formula: see text] and [Ta6O[Formula: see text]][Formula: see text]. In addition, the charge density [Formula: see text] of [V6O[Formula: see text]][Formula: see text] is larger when compared with those of other studied clusters. The investigation on the derivatives shows that the valence of V atom (V[Formula: see text] or V[Formula: see text]) and the methoxy ligand influence the HOMO[Formula: see text]LUMO energy gap and the charge density [Formula: see text] of the studied clusters.