bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study and Numerical Modeling of Friction Stir Spot Welding of Pure Copper Lap Joint
Authors: Mahgoub Ahmed Kamal , Bazoune Abdelaziz , Al-Badour Fadi A. A. , Shuaib Abdelrahman , Karrar Gihad Mohamed
Published: March 2015

Friction stir spot welding (FSSW) is an appropriate process to join materials that are difficult to weld using fusion welding, such as copper. In this paper, an experimental study to weld lap joint of pure copper plates having a dimensions of 100 × 30 × 2 mm is performed, successful spot weld is obtained at tool rotational speed of 1200 rpm, feed rate of 20 mm/min for dwell time of 2 seconds. The tool used in the FSSW has a threaded pin of 5 mm diameter, length of 3.7 mm, and a scrolled shoulder of 11.52 mm diameter. Tensile test and microhardness were performed for the joint and it showed reasonable weld strength. In addition, a numerical model was developed, and the estimated temperatures as well as weld macrostructure matched very well with experimental results.
2D Cutting Stock Problem Using Hybrid 3-D Overlapped Grouping Genetic Algorithm
Authors: Rostom Maged R. , Nassef Ashraf O. , Metwalli Sayed M.
Published: March 2015

The cutting stock problem (CSP) is a business problem that arises in many areas, particularly in manufacturing industries where a given stock material must be cut into a smaller set of shapes. It has gained a lot of attention for increasing efficiency in industrial engineering, logistics and manufacturing. This paper presents a hybrid new 3-D overlapped grouping Genetic Algorithm (GA) that solves two-dimensional cutting stock problems for nesting the rectangular shapes. The objective is the minimization of the wastage of the sheet material which leads to maximizing material utilization and the minimization of the setup time. The model and its results are compared with real life case study from a steel workshop in a bus manufacturing factory. The effectiveness of the proposed approach is shown by comparing and shop testing of the optimized cutting schedules. The results reveal its superiority in terms of waste minimization comparing to the current cutting schedules and show that our approach outperforms existing heuristic algorithms. The whole procedure can be completed in a reasonable amount of time by the developed optimization program.
Mechanism of Screw Thread Loosening in Bolted Joints With Dissimilar Clamped Parts Under Repeated Temperature Changes
Authors: Ishimura Mitsutoshi , Sawa Shunichiro , Omiya Yuya , Sawa Toshiyuki
Published: March 2015

It is well known that bolted joints are sometimes loosened under transverse repeated loadings. Recently, some studies have been carried out on the mechanism of the bolt loosening under transverse repeated loadings. In the present research, the mechanism of bolt loosening was examined for a bolted joint using Junker’s type loosening test machine under transverse repeated loadings. Furthermore, a rotational deformation of bolt axis and nut was analyzed using FEM. As a result, it is found that the rotational load is applied and the bolt loosening occurs due to the deformation between the bolt axis and the nut. The measured change in axial bolt force was fairly good agreement with the numerical results. In addition, the bolt loosening in bolted joints with dissimilar clamped parts was examined under temperature changes. Due to the temperature changes, it is assumed that a relative displacement among the bolt bearing surface and the bearing surfaces of the clamped parts and then it is found that a bolt loosening occurs. In FEM calculations, the behavior of the bolt loosening was examined and found to occur a slight loosening. In the experiments, the bolt loosening was measured under temperature changes. The material of dissimilar clamped parts is assumed steel and aluminum. The thickness of the clamped parts is 10mm. The tendency of the bolt loosening is fairly coincided between the numerical and the measured results. It was observed that the bolt loosening occurred easily as the clamped length (gap length) decreased. In the FEM calculations, the slope θ of the bearing surfaces between the bolt head and the clamped part is assumed to be 0.5 degree to 2 degree. The effects of the slope of the bearing surfaces and on the bolt loosening are examined in the FEM calculations. The calculated results are in a fairly good agreement with the measured results. As the conclusions, 1) the bolt loosening of bolted joints under transverse repeated loadings was elucidated using 3-D FEM calculations, 2) Under repeated temperature changes, it was found that the bolt loosening occurred due to the slips between the bearing surfaces and the interfaces of clamped parts. Using FEM calculations, the behavior of the bolt loosening was elucidated.
Generation of Intake Distortion due to Angle of Attack for a High Bypass Turbofan Model
Authors: Krone Jan-Hendrik , Friedrichs Jens
Published: March 2015

This article presents a new fan testing concept which was developed by the University of Braunschweig. The aim of the concept is to provide an experimental setup for integrated jet engine fan investigations. This integrated setup includes a full bypass model with nacelle geometry in order to obtain all aerodynamic interaction effects. Since these interactions have a strong dependency from fan inlet conditions the facility provides wind tunnel capacities. Generating both uniform and angle of attack inlet conditions it is possible to investigate fan performance during the most critical operating points of a civil flight mission. The main innovation of the wind tunnel is the crosswind concept for generating angle of attack conditions in case of a non-pitchable fan unit. Numerical investigations in this paper are intended to validate this new concept by means of typical angle of attack simulations. The results show that the crosswind concept is able to generate equivalent cp-characteristics as obtained for the reference simulations at the nacelle 6 o‘clock and 12 o‘clock positions.
Localized Decision-Making for Materials Transportation Systems Subject to Stochastic Uncertainty
Authors: Chee Matthew , Turner Cameron J.
Published: March 2015

Programming and installation of Materials Transportation Systems (MTS) in a manufacturing setting represent a significant portion of the investment in these systems. The costs are often so high that this alone presents a barrier to adoption amongst midsize manufacturers. Furthermore, the resulting systems are just as costly to reconfigure, limiting the flexibility of the resulting manufacturing facility to product changes. This research examines a localized decision-making scheme, in which individual manufacturing components are enhanced with an amount of intelligence and autonomy to enable the system to automatically self-program. Through an example, we study this paradigm versus fixed programming alternatives as the stochastic variability of the manufacturing setting increases. Localized Decision-Making enables a plug-n-play autonomy that can readily adapt to changes and deal with uncertainties in manufacturing.
Reversing Design Methodology of Ceramic Core for Hollow Turbine Blade Based on Measured Data
Authors: Dou Yangliu , Yan Fengjun , Bu Kun
Published: March 2015

The precision of complex ceramic core is one of the essential factors for hollow turbine blade manufacturing, which has a significant impact on the development of the modern aircraft engine. In terms of the low precision of ceramic core formation, this paper proposes an approach through measuring the data from a group of ceramic cores, to study the computational methods for displacement field, deformational feature decoupling, and structural shrinkage ratio. Based on modeling and analysis of decoupled deformational features and the uneven structural shrinkage ratio, this paper proposes an inverse design method and optimizes the design of the die profile for ceramic core. The applicability of this method is validated using numerical simulation data and experimental results.
Friction Stir Butt Welding of Commercially Pure Copper Plates
Authors: Karrar Gihad , Shuaib A. N. , Al-Badour F. A. , Merah N. , Mahgoub A. K.
Published: March 2015

This paper presents the results of studying friction stir butt welding of commercial pure copper plates using both experimental and finite element analysis methods. The experimental work consisted of making a butt joint to 4 mm copper plates using friction stir welding process at constant rotational speed of the pin tool to evaluate the effect of welding speed on weld quality. Weld quality was evaluated by the joints tensile strength, micro hardness, as well as evolution of the developed microstructure across the welding zone. A coupled Eulerian Lagrangian (CEL) finite element (FE) model had been developed to simulate the friction stir butt welding process, and predict the temperature distributions across the weld, as well as developed welding stresses. Axial load and temperature measurements results from the experiments have been used to validate the finite element model.
Working Load Analysis and Strength Estimation for Bolted Joints During Actual Machine Operation
Authors: Hareyama Soichi , Manabe Ken-ichi , Shimodaira Takayuki , Hoshi Akio
Published: March 2015

Serious problems caused by bolted joint fatigue breakage still occur. This is because working load evaluation and durability strength evaluation have been insufficient in the product design stage, in the test stage of machine lifetime prediction, in the trial production stage, in the prototype machine test stage, and so forth.

In this paper, we propose a method for measuring and analyzing the load on bolted joints used in a machine under actual operation. Working load measurement under actual machine operation and the results of its analysis are shown as load frequency diagrams. This is very important information for realizing the concept of simultaneous multiple design. An example of the measurement analysis method of the load (three types of the loads; axial force, bending moment, and the torsional torque) added to the bolted joint shank which comes out at the time of the actual machine operation is shown.

The reliability of assessing the strength and durability of bolted joints is considered from the viewpoint of limited-lifetime (finite-lifetime) design using Miner’s rule with cumulative loosening damage models and fatigue limit (infinite-lifetime) design. As an example, we measured the working stress and evaluated the strength of a bolted joint of an actual machine to verify the usefulness of the proposed method. Also, examples of strength evaluation are shown to illustrate finite-lifetime and infinite-lifetime prediction.

Moreover, the practical process and presumed example of fatigue life prediction are shown. It is considered as a contribution at the improvement of strength reliability and the load analysis method of the bolted joint of machine develop-ment stage and failure analysis stage. Our findings are also expected to eradicating accidents involving bolted joints in machines.
Experimental Investigation of Porosity Effects on Machinability and Residual Strength in Brittle Materials
Authors: O’Connor A. , Ramulu M.
Published: March 2015

Three commercially available tooling materials for composite component manufacturing were chosen for evaluation of their machinability and surface integrity as it fulfills the lightweight and coefficient of thermal expansion requirements of polymer matrix composite. All three of these materials (CB1100 ceramic tooling block, AAC-4/500 and Cfoam™ carbon foam) are brittle and porous in nature. End milling machining tests were conducted in order to study the effects of porosity on cutting forces and surface integrity. Measured cutting force profiles were found to be random in magnitude and shape reflecting the variation in pore size and distribution as well as chipping and fracture of the material. It was found that the damage induced during the machining of Cfoam and AAC-4/500 was small in comparison to the size of the pores and had no significant effect on the surface integrity and transverse rupture strength of the materials within the experimental conditions. Therefore, porosity had a positive benefit to the surface integrity and tolerance to machining induced damage. However, damage introduced during the machining of CB1100 was discovered to be significant in comparison to the pore size and was shown to decrease characteristic strength by approximately 16% according to the conducted Weibull analysis.
Design of a Retrofittable Spindle Attachment for High Frequency Vibration-Assisted Drilling
Authors: Panju J. , Meshreki M. , Attia M. H.
Published: March 2015

Conventional drilling of modern super alloys and composite material induces high stresses in the vicinity of drilled holes along with high thrust forces which lead to problems in terms of hole quality and accuracy as well as increased tool wear. A recent and promising technique to overcome these challenges is to introduce vibration assistance in the cutting zone by superimposing oscillating vibration in the feed direction of the tool. Two regimes of vibration excitation could be applied for this purpose: low frequency (<500 Hz) high amplitude (>100 μm) and high frequency (>500 Hz) low amplitude (<20 μm). Motivated by the advantages of the HF-VAD and the limited work available in the literature for this regime, a new system is developed by the authors where the rotating tool is excited to high frequency and low amplitude. The new design is based on the use of piezoelectric actuators to generate the motion and a high speed slip ring to ensure the transfer of sufficient power to the actuator. A novel concept was implemented by de-coupling the rotary motion of the spindle from the vibrational motion of the actuator to ensure a higher efficiency of power transmission without damaging either the actuator or the spindle. With this design, a retrofittable HSK 100A toolholder with high frequency excitation spindle attachment was manufactured to incorporate drill sizes up to 1/4 inches. Commissioning tests were performed under no load and spring loaded conditions and it was found that the system has a capability to excite the tool up to 100 μm at 900 Hz (resonance frequency) and up to 5 μm between 500–800 Hz and 1100–2500 Hz. HF-VAD tests were conducted using this new attachment on Aluminum 6061 and it was found that the system was able to successfully obtain the prescribed frequency and amplitude. Up to 50% reduction in thrust forces was obtained in HF-VAD in comparison to conventional drilling under same cutting parameters; this is associated with finer chips with break off serrations.
On the Vortex Breakdown Phenomenon in High Angle of Attack Flows Over Delta Wing Geometries
Authors: Robertson Eric D. , Chitta Varun , Walters D. Keith , Bhushan Shanti
Published: March 2015

Using computational methods, an investigation was performed on the physical mechanisms leading to vortex breakdown in high angle of attack flows over delta wing geometries. For this purpose, the Second International Vortex Flow Experiment (VFE-2) 65° sweep delta wing model was studied at a root chord Reynolds number (Recr) of 6 × 106 at various angles of attack. The open-source computational fluid dynamics (CFD) solver OpenFOAM was used in parallel with the commercial CFD solver ANSYS® FLUENT. For breadth, a variety of classic closure models were applied, including unsteady Reynolds-averaged Navier-Stokes (URANS) and detached eddy simulation (DES). Results for all cases are analyzed and flow features are identified and discussed. The results show the inception of a pair of leading edge vortices originating at the apex for all models used, and a region of steady vortical structures downstream in the URANS results. However, DES results show regions of massively separated helical flow which manifests after vortex breakdown. Analysis of turbulence quantities in the breakdown region gives further insight into the mechanisms leading to such phenomena.
Effect of Tool Kinematics on the Drilling Forces and Temperature in Low Frequency High Amplitude Vibration Assisted Drilling
Authors: Sadek A. , Meshreki M. , Attia M. H.
Published: March 2015

Defects associated with drilling of fiber reinforced polymers (FRPs) are of major economic and safety concerns for aerospace manufacturers. Delamination of layers and thermal damage of the matrix are the most critical defects associated with drilling of FRP laminates, which can be avoided by keeping the drilling forces and temperatures below some threshold levels. Vibration-assisted drilling (VAD) is an emerging drilling process that uses intermittent cutting to reduce the drilling forces and temperatures, and achieve easier chip removal compared to conventional drilling. In this paper an extensive experimental study has been conducted to provide insight into the effect of the tool kinematics corresponding to the VAD parameters (speed, feed, frequency and amplitude) on the geometry of the formed chip determined by the intersection of the trajectories of the cutting edges as well as on the drilling forces and temperature. The combinations of the VAD parameters used in this study were selected from ranges of speeds 6,000 rpm to 12,000 rpm, feeds 0.05 mm/rev to 0.15 mm/rev, frequencies 30 Hz and 60 Hz, and amplitudes 40 μm to 400 μm. The Amplitude and feed were found to have the most dominant effect on the VAD forces, while the feed and speed had the dominant effect on the VAD temperatures. The thermal performance of the VAD process was found to be enhanced by the formation of vortices in the air gap created by the separation between the tool and the machined surface, which is mainly controlled by the feed and the rotational speed of the tool.
Molecular Dynamics Simulation of Shot Peening Process and Residual Stress Generation: Effects of Particle Impact Speed and Impinging Angle
Authors: Wang Yachao , Shi Jing , Wang Xinnan
Published: March 2015

Shot peening is a well-known surface finishing process that is often applied to enhance the residual stress distribution in the component surfaces. In this study, we carry out a molecular dynamics (MD) simulation study to investigate the single particle shot peening process on the (100) silicon surface at nano scale. The MD simulation enables in-situ observation and analysis of complex material deformation mechanisms in the presences of ultra-high strain rate, such as stress distribution, dislocation propagation, and particle/workpiece interface interaction. Three levels of shot speed (i.e., 200, 500, and 800 m/s) and three levels of impinging angle (i.e., 30°, 60°, and 90°) are configured in the simulation. It is found that higher shot speeds result in deeper depths of residual indentation, deeper penetration depths of residual stress below surface, and higher magnitude of maximum compressive stress. The residual stress distributions underneath the shot-peened surfaces exhibit strong anisotropic manner. Residual stress only concentrates in the area along the impact direction; and the decrease of impact angle results in shallower penetration of residual stress.
Effect of Solid Lubricant on Surface Quality in Turning of Al 6061 Alloy
Authors: Srivastava Anand Suman , Agarwal Sanjay , Saxena Krishna Kumar
Published: March 2015

The aluminium alloys are widely employed in the aeronautical, aerospace and automotive industries as they provide good heat conductivity, corrosion resistance, high strength to weight ratio even at high temperatures. Cutting fluids are still widely used in the machining of aluminium alloys to cope with problems associated with the heat generation. However, the growing social concern towards environmental conservation has made it necessary to develop cleaner production technologies such as dry machining in which no cutting fluids are employed. Solid lubricant assisted machining is a novel concept to control the machining zone temperature without polluting the environment. The surface quality of the machined parts is one of the most important product quality characteristics and one of the most frequent customer requirements. The present study focuses on investigating the effect of boric acid powder as solid lubricant on surface quality. Experiments have been conducted using Taguchi’s L9 orthogonal array. The influence of machining parameters viz. cutting speed, feed, rake angle and tool nose radius on surface quality has been investigated.
Design and Analysis of a Highly Loaded Tandem Compressor Stage
Authors: Eshraghi Hamzeh , Boroomand Masoud , Tousi Abolghasem M.
Published: March 2015

In this study, a 3D design procedure for axial flow tandem stage is developed, and then a highly loaded stage is designed with this method. Designed stage is numerically investigated with a CFD code and the stage characteristic map is reported. In order to investigate the effect of highly loaded design, a conventionally loaded compressor stage is designed with single blade for rotor and stator rows. For a better comparison, Chord lengths and hub/shroud geometries are selected same between highly and conventionally loaded compressors. Characteristic map of the conventional compressor is reported too and performance of highly loaded and conventionally loaded compressors are compared.

To validate the CFD method, another compressor stage is presented that its geometry and experimental results are available. Performance of the recent compressor stage is numerically investigated and compared with experimental results.
Evaluation of a Parallel Agglomeration Multigrid Finite-Volume Algorithm, Named Galatea-I, for the Simulation of Incompressible Flows on 3D Hybrid Unstructured Grids
Authors: Sarakinos Sotirios S. , Lygidakis Georgios N. , Nikolos Ioannis K.
Published: March 2015

In this study an academic Computational Fluid Dynamics (CFD) code, named Galatea-I, is described, which employs the Reynolds Averaged Navier–Stokes (RANS) equations along with the artificial compressibility method and the SST (Shear Stress Transport) turbulence model for the prediction of incompressible viscous flows. For the representation of the computational domain unstructured hybrid grids are utilized, composed of tetrahedral, prismatic and pyramidical elements, while for its discretization a node-centered finite-volume scheme is implemented. Galatea-I is enhanced with a parallelization method, which employs spatial domain decomposition, while the data exchange between processors/processes is performed with the use of the Message Passing Interface (MPI) protocol. In addition, a parallel agglomeration multigrid methodology has been incorporated to improve further its computational performance. The proposed code is validated against steady-state flow benchmark test cases, concerning laminar flow over a cubic cavity and a cylindrical surface, as well as turbulent flow over a rectangular wing with a NACA0012 airfoil. The obtained results, compared with these of corresponding reference solvers, reveal Galatea-I’s potential for simulation of inviscid, viscous laminar and turbulent incompressible flows.
Investigation of Carbon Nanotubes Mixing Methods and Functionalizations for Electrically Conductive Polymer Composites
Authors: Talwar Brijpal Singh , Chizari Kambiz , Guo Shuangzhuang , Therriault Daniel
Published: March 2015

The growing popularity of Poly lactic acid (PLA) is related to its biocompatibility, good mechanical properties, and its synthesis from renewable resources. PLA can be compounded with electrically conductive fillers (e.g., carbon nanotubes (CNTs)) to form carbon polymer composites (CPC). These fillers provide the conductive functionality by forming percolative paths. Featuring very low weight densities, CPCs have the potential to replace metals in the electronic industry if they exhibit similar electrical conductivities. The current challenges being faced during the mixing of CNTs in a polymer matrix are the formation of aggregates due to the strong van der Waals forces and the breakage of the CNTs during dispersion. In this study, we compare: (1) two fabrication methods to create CPCs (i.e., solution mixing by sonication and extrusion) and (2) effects of various CNT functionalization techniques (i.e., acid and plasma treatments) on the conductivity of the CPCs. First, the composites comprising of 30% PLA by weight in Dichloromethane (DCM) and CNTs in different concentrations (up to 5wt.%) are fabricated by two step sonication method (i.e., dissolving PLA in DCM and then dispersing the CNTs in the polymer solution). Second, CPCs are fabricated using a micro twin screw extruder operating at 180°C. To verify the effects of functionalization of the CNTs on the conductivity of composites, the CNTs are functionalized via three methods: - HNO3 acid functionalization, 3:1 ratio HNO3 + H2SO4 acid (stronger) functionalization and N2 plasma functionalization. CPC fibers are drawn using the solvent-cast printing method. These fibers are then tested for their electrical conductivity using the two probe method. The maximum electrical conductivity is showed by the 5% CNT concentration samples at 3.97 S/m and 25.16 S/m for the CPC fibers obtained via the solution blend and the extrusion methods, respectively. Regarding the functionalized CNTs, conductivity measurements show a negative effect of the CNTs functionalization on the electrical properties of the CPC.
Taxonomic Identification of Ruminal Epithelial Bacterial Diversity during Rumen Development in Goats
Authors: Jiao Jinzhen , Huang Jinyu , Zhou Chuanshe , Tan Zhiliang
Published: March 2015

Understanding of the colonization process of epithelial bacteria attached to the rumen tissue during rumen development is very limited. Ruminal epithelial bacterial colonization is of great significance for the relationship between the microbiota and the host and can influence the early development and health of the host. MiSeq sequencing of 16S rRNA genes and quantitative real-time PCR (qPCR) were applied to characterize ruminal epithelial bacterial diversity during rumen development in this study. Seventeen goat kids were selected to reflect the no-rumination (0 and 7 days), transition (28 and 42 days), and rumination (70 days) phases of animal development. Alpha diversity indices (operational taxonomic unit [OTU] numbers, Chao estimate, and Shannon index) increased (
P
< 0.01) with age, and principal coordinate analysis (PCoA) revealed that the samples clustered together according to age group. Phylogenetic analysis revealed that
Proteobacteria
,
Firmicutes
, and
Bacteroidetes
were detected as the dominant phyla regardless of the age group, and the abundance of
Proteobacteria
declined quadratically with age (
P
< 0.001), while the abundances of
Bacteroidetes
(
P
= 0.088) and
Firmicutes
(
P
= 0.009) increased with age. At the genus level,
Escherichia
(80.79%) dominated at day zero, while
Prevotella
,
Butyrivibrio
, and
Campylobacter
surged (linearly;
P
< 0.01) in abundance at 42 and 70 days. qPCR showed that the total copy number of epithelial bacteria increased linearly (
P
= 0.013) with age. In addition, the abundances of the genera
Butyrivibrio
,
Campylobacter
, and
Desulfobulbus
were positively correlated with rumen weight, rumen papilla length, ruminal ammonia and total volatile fatty acid concentrations, and activities of carboxymethylcellulase (CMCase) and xylanase. Taking the data together, colonization by ruminal epithelial bacteria is age related (achieved at 2 months) and might participate in the anatomic and functional development of the rumen.
Species Richness and Adaptation of Marine Fungi from Deep-Subseafloor Sediments
Authors: Rédou Vanessa , Navarri Marion , Meslet-Cladière Laurence , Barbier Georges , Burgaud Gaëtan
Published: March 2015

The fungal kingdom is replete with unique adaptive capacities that allow fungi to colonize a wide variety of habitats, ranging from marine habitats to freshwater and terrestrial habitats. The diversity, importance, and ecological roles of marine fungi have recently been highlighted in deep-subsurface sediments using molecular methods. Fungi in the deep-marine subsurface may be specifically adapted to life in the deep biosphere, but this can be demonstrated only using culture-based analyses. In this study, we investigated culturable fungal communities from a record-depth sediment core sampled from the Canterbury Basin (New Zealand) with the aim to reveal endemic or ubiquist adapted isolates playing a significant ecological role(s). About 200 filamentous fungi (68%) and yeasts (32%) were isolated. Fungal isolates were affiliated with the phyla Ascomycota and Basidiomycota, including 21 genera. Screening for genes involved in secondary metabolite synthesis also revealed their bioactive compound synthesis potential. Our results provide evidence that deep-subsurface fungal communities are able to survive, adapt, grow, and interact with other microbial communities and highlight that the deep-sediment habitat is another ecological niche for fungi.
Tropical Strains of Ralstonia solanacearum Outcompete Race 3 Biovar 2 Strains at Lowland Tropical Temperatures
Authors: Huerta Alejandra I. , Milling Annett , Allen Caitilyn
Published: March 2015

Bacterial wilt, caused by members of the heterogenous
Ralstonia solanacearum
species complex, is an economically important vascular disease affecting many crops. Human activity has widely disseminated
R. solanacearum
strains, increasing their global agricultural impact. However, tropical highland race 3 biovar 2 (R3bv2) strains do not cause disease in tropical lowlands, even though they are virulent at warm temperatures. We tested the hypothesis that differences in temperature adaptation and competitive fitness explain the uneven geographic distribution of
R. solanacearum
strains. Using three phylogenetically and ecologically distinct strains, we measured competitive fitness at two temperatures following paired-strain inoculations of their shared host, tomato. Lowland tropical strain GMI1000 was only weakly virulent on tomato under temperate conditions (24°C for day and 19°C for night [24/19°C]), but highland tropical R3bv2 strain UW551 and U.S. warm temperate strain K60 were highly virulent at both 24/19°C and 28°C. Strain K60 was significantly more competitive than both GMI1000 and UW551 in tomato rhizospheres and stems at 28°C, and GMI1000 also outcompeted UW551 at 28°C. The results were reversed at cooler temperatures, at which highland strain UW551 generally outcompeted GMI1000 and K60
in planta
. The superior competitive index of UW551 at 24/19°C suggests that adaptation to cool temperatures could explain why only R3bv2 strains threaten highland agriculture. Strains K60 and GMI1000 each produced different bacteriocins that inhibited growth of UW551 in culture. Such interstrain inhibition could explain why R3bv2 strains do not cause disease in tropical lowlands.
In Vivo
Transmission of an IncA/C Plasmid in Escherichia coli Depends on Tetracycline Concentration, and Acquisition of the Plasmid Results in a Variable Cost of Fitness
Authors: Johnson Timothy J. , Singer Randall S. , Isaacson Richard E. , Danzeisen Jessica L. , Lang Kevin , Kobluk Kristi , Rivet Bernadette , Borewicz Klaudyna , Frye Jonathan G. , Englen Mark , Anderson Janet , Davies Peter R.
Published: March 2015

IncA/C plasmids are broad-host-range plasmids enabling multidrug resistance that have emerged worldwide among bacterial pathogens of humans and animals. Although antibiotic usage is suspected to be a driving force in the emergence of such strains, few studies have examined the impact of different types of antibiotic administration on the selection of plasmid-containing multidrug resistant isolates. In this study, chlortetracycline treatment at different concentrations in pig feed was examined for its impact on selection and dissemination of an IncA/C plasmid introduced orally via a commensal
Escherichia coli
host. Continuous low-dose administration of chlortetracycline at 50 g per ton had no observable impact on the proportions of IncA/C plasmid-containing
E. coli
from pig feces over the course of 35 days. In contrast, high-dose administration of chlortetracycline at 350 g per ton significantly increased IncA/C plasmid-containing
E. coli
in pig feces (
P
< 0.001) and increased movement of the IncA/C plasmid to other indigenous
E. coli
hosts. There was no evidence of conjugal transfer of the IncA/C plasmid to bacterial species other than
E. coli
.
In vitro
competition assays demonstrated that bacterial host background substantially impacted the cost of IncA/C plasmid carriage in
E. coli
and
Salmonella
.
In vitro
transfer and selection experiments demonstrated that tetracycline at 32 μg/ml was necessary to enhance IncA/C plasmid conjugative transfer, while subinhibitory concentrations of tetracycline
in vitro
strongly selected for IncA/C plasmid-containing
E. coli
. Together, these experiments improve our knowledge on the impact of differing concentrations of tetracycline on the selection of IncA/C-type plasmids.
Phylogenetic and Functional Alterations in Bacterial Community Compositions in Broiler Ceca as a Result of Mannan Oligosaccharide Supplementation
Authors: Corrigan A. , de Leeuw Marcel , Penaud-Frézet Stéphanie , Dimova Diliana , Murphy R. A.
Published: March 2015

This study focused on identifying reproducible effects of dietary supplementation with a mannan oligosaccharide (MOS) on the broiler cecal bacterial community structure and function in a commercial production setting. Two separate trials, each with a control and a supplemented group, were carried out in the same commercial location and run concurrently. Approximately 10,000 birds from the same commercial hatchery were mirror imaged into each of four commercial broiler sheds and fed either a control or supplemented diet. Cecal contents were obtained on days 7, 21, and 35 posthatch from 12 randomly caught broilers from each group. Bacterial pyrosequencing was performed on all samples, with approximately 250,000 sequences obtained per treatment per time point. The predominant phyla identified at all three time points in both trials were
Firmicutes
,
Bacteroidetes
,
Proteobacteria
,
Actinobacteria
, and
Tenericutes
, representing >99% of all sequences. MOS supplementation altered the bacterial community composition from 7 days supplementation through 35 days supplementation.
Bacteroidetes
appeared to be replacing
Firmicutes
as a result of supplementation, with the most noticeable effects after 35 days. The effects of supplementation were reproducible across both trials. PICRUSt was used to identify differences between the functional potentials of the bacterial communities as a result of MOS supplementation. Using level 3 KEGG ortholog function predictions, differences between control and supplemented groups were observed, with very strong segregation noted on day 35 posthatch in both trials. This indicated that alterations of bacterial communities as a result of MOS are likely to alter the functional capability of the cecum.
Examining the relationship between neighbourhood deprivation and mental health service use of immigrants in Ontario, Canada: a cross-sectional study
Authors: Durbin Anna , Moineddin Rahim , Lin Elizabeth , Steele Leah S , Glazier Richard H
Published: March 2015

Objective

While newcomers are often disproportionately concentrated in disadvantaged areas, little attention is given to the effects of immigrants’ postimmigration context on their mental health and care use. Intersectionality theory suggests that understanding the full impact of disadvantage requires considering the effects of interacting factors. This study assessed the inter-relationship between recent immigration status, living in deprived areas and service use for non-psychotic mental health disorders.

Study design

Matched population-based cross-sectional study.

Setting

Ontario, Canada, where healthcare use data for 1999–2012 were linked to immigration data and area-based material deprivation scores.

Participants

Immigrants in urban Ontario, and their age-matched and sex-matched long-term residents (a group of Canadian-born or long-term immigrants, n=501 417 pairs).

Primary and secondary outcome measures

For immigrants and matched long-term residents, contact with primary care, psychiatric care and hospital care (emergency department visits or inpatient admissions) for non-psychotic mental health disorders was followed for 5 years and examined using conditional logistic regression models. Intersectionality was investigated by including a material deprivation quintile by immigrant status (immigrant vs long-term resident) interaction.

Results

Recent immigrants in urban Ontario were more likely than long-term residents to live in most deprived quintiles (immigrants—males: 22.8%, females: 22.3%; long-term residents—both sexes: 13.1%, p<0.001). Living in more deprived circumstances was associated with greater use of mental health services, but increases were smaller for immigrants than for long-term residents. Immigrants used less mental health services than long-term residents.

Conclusions

This study adds to existing research by suggesting that immigrant status and deprivation have a combined effect on recent immigrants’ care use for non-psychotic mental health disorders. In settings where immigrants are over-represented in deprived areas, policymakers focused on increasing immigrants’ access of mental health services should broadly address the influence of structural and cultural factors beyond the disadvantage.
Predictors of intentions to quit smoking in Aboriginal tobacco smokers of reproductive age in regional New South Wales (NSW), Australia: quantitative and qualitative findings of a cross-sectional survey
Authors: Gould Gillian Sandra , Watt Kerrianne , McEwen Andy , Cadet-James Yvonne , Clough Alan R
Published: March 2015

Objectives

To assess the predictors of intentions to quit smoking in a community sample of Aboriginal smokers of reproductive age, in whom smoking prevalence is slow to decline.

Design, setting and participants

A cross-sectional survey involved 121 Aboriginal smokers, aged 18–45 years from January to May 2014, interviewed at community events on the Mid-North Coast NSW. Qualitative and quantitative data were collected on smoking and quitting attitudes, behaviours and home smoking rules. Perceived efficacy for quitting, and perceived threat from smoking, were uniquely assessed with a validated Risk Behaviour Diagnosis (RBD) Scale.

Main outcome measures

Logistic regression explored the impact of perceived efficacy, perceived threat and consulting previously with a doctor or health professional (HP) on self-reported intentions to quit smoking, controlling for potential confounders, that is, protection responses and fear control responses, home smoking rules, gender and age. Participants’ comments regarding smoking and quitting were investigated via inductive analysis, with the assistance of Aboriginal researchers.

Results

Two-thirds of smokers intended to quit within 3 months. Perceived efficacy (OR=4.8; 95% CI 1.78 to 12.93) and consulting previously with a doctor/HP about quitting (OR=3.82; 95% CI 1.43 to 10.2) were significant predictors of intentions to quit. ‘Smoking is not doing harm right now’ was inversely associated with quit intentions (OR=0.25; 95% CI 0.08 to 0.8). Among those who reported making a quit attempt, after consulting with a doctor/HP, 40% (22/60) rated the professional support received as low (0–2/10). Qualitative themes were: the negatives of smoking (ie, disgust, regret, dependence and stigma), health effects and awareness, quitting, denial, ‘smoking helps me cope’ and social aspects of smoking.

Conclusions

Perceived efficacy and consulting with a doctor/HP about quitting may be important predictors of intentions to quit smoking in Aboriginal smokers of reproductive age. Professional support was generally perceived to be low; thus, it could be improved for these Aboriginal smokers. Aboriginal participants expressed strong sentiments about smoking and quitting.
Monetary costs of agitation in older adults with Alzheimer's disease in the UK: prospective cohort study
Authors: Morris Stephen , Patel Nishma , Baio Gianluca , Kelly Lynsey , Lewis-Holmes Elanor , Omar Rumana Z , Katona Cornelius , Cooper Claudia , Livingston Gill
Published: March 2015

Objective

While nearly half of all people with Alzheimer's disease (AD) have agitation symptoms every month, little is known about the costs of agitation in AD. We calculated the monetary costs associated with agitation in older adults with AD in the UK from a National Health Service and personal social services perspective.

Design

Prospective cohort study.

Setting

London and the South East Region of the UK (LASER-AD study).

Participants

224 people with AD recruited between July 2002 and January 2003 and followed up for 54 months.

Primary and secondary outcome measures

The primary outcome was health and social care costs, including accommodation costs and costs of contacts with health and social care services. Agitation was assessed using the Neuropsychiatric Inventory (NPI) agitation score.

Results

After adjustment, health and social care costs varied significantly by agitation, from £29 000 over a 1 year period with no agitation symptoms (NPI agitation score=0) to £57 000 at the most severe levels of agitation (NPI agitation score=12; p=0.01). The mean excess cost associated with agitation per person with AD was £4091 a year, accounting for 12% of the health and social care costs of AD in our data, and equating to £2 billion a year across all people with AD in the UK.

Conclusions

Agitation in people with AD represents a substantial monetary burden over and above the costs associated with cognitive impairment.
Incidence of metachronous visible lesions in patients referred for radiofrequency ablation (RFA) therapy for early Barrett's neoplasia: a single-centre experience
Authors: Ortiz-Fernández-Sordo J , Sami S , Mansilla-Vivar R , De Caestecker J , Cole A , Ragunath K
Published: March 2015

Objective

Evaluate the incidence of metachronous visible lesions (VLs) in patients referred for radiofrequency ablation (RFA) for early Barrett's neoplasia.

Design

This study was conducted as part of the service evaluation audit.

Setting

Tertiary referral centre.

Patients

All patients with dysplastic Barrett's oesophagus referred for RFA were included for analysis. White light high-resolution endoscopy (HRE), autofluorescence imaging and narrow band imaging were sequentially performed. Endoscopic mucosal resection (EMR) was performed for all VL. Three to six months after EMR, all patients underwent initial RFA and then repeat RFA procedures at three monthly intervals.

Interventions

All endoscopy reports and final staging by EMR/surgery were evaluated and included for analysis.

Results

Fifty patients were analysed; median age 73 years, 84% men. 38/50 patients (76%) had a previous EMR due to the presence of VL before referred for ablation; twelve patients had no previous treatment. In total, 151 ablation procedures were performed, median per patient 2.68. Twenty metachronous VL were identified in 14 patients before the first ablation or during the RFA protocol; incidence was 28%. All metachronous lesions were successfully resected by EMR. Upstaging after rescue EMR compared with the initial histology was observed in four patients (28%).

Conclusions

In total, 28% of patients enrolled in the RFA programme were diagnosed to have metachronous lesions. This high-incidence rate highlights the importance of a meticulous examination to identify and resect any VL before every ablation session. RFA treatment for early Barrett's neoplasia should be performed in tertiary referral centres with HRE and EMR facilities and expertise.
Endovascular treatment of intracranial aneurysms using the Pipeline Flex embolization device: a case series of 30 consecutive patients
Authors: Martínez-Galdámez M , Pérez S , Vega A , Ruiz P , Caniego J L , Bárcena E , Saura P , Méndez J C , Delgado F , Ortega-Gutierrez S , Romance A , Diaz T , Gonzalez E , Gil A , Murias E , Vega P
Published: March 2015

Background

The Pipeline Flex embolization device has some peculiarities in comparison with the previous generation device. Despite recent reports of the modified delivery system, its safety is still unknown.

Objective

To illustrate the intraprocedural and periprocedural complication rate with this new device in 30 consecutive patients.

Material and methods

Clinical, procedural, and angiographic data, including aneurysm size and location, device or devices used, angiographic and clinical data were analyzed.

Results

30 patients harboring 30 aneurysms were analyzed. 39 devices were placed properly. Multiple Pipeline embolization devices (PEDs) were used in 7 cases. In 28 devices the distal end opened fully from the beginning with a complete wall apposition. In the remaining 11 devices, distal-end opening of the devices was instant but partial, but fully opened easily after recapture. Among the 30 procedures, recapture and reposition of the Pipeline Flex was performed four times owing to proximal migration/malposition of the device during delivery. Four intraprocedural/periprocedural complications occurred, of which 2 resulted in major complications, with neurologic deficits persisting for longer than 7 days. The 30-day morbidity rate was 6.6%, with no deaths. No aneurysm rupture or parenchymal hemorrhage was seen.

Conclusions

The Pipeline Flex embolization device allows more precise and controlled deployment than the first-generation device. The number of devices and the complication rate during the learning curve are lower than reported with the first-generation PED. The new delivery system and the resheathing maneuvers do not seem to increase the intraprocedural complication rate in comparison with the first-generation PED.
Pressure dependency of aortic pulse wave velocity in vivo is not affected by vasoactive substances that alter aortic wall tension ex vivo
Authors: Butlin Mark , Lindesay George , Viegas Kayla D. , Avolio Alberto P.
Published: March 2015

Aortic stiffness, a predictive parameter in cardiovascular medicine, is blood pressure dependent and experimentally requires isobaric measurement for meaningful comparison. Vasoactive drug administration to change peripheral resistance and blood pressure allows such isobaric comparison but may alter large conduit artery wall tension, directly changing aortic stiffness. This study quantifies effects of sodium nitroprusside (SNP, vasodilator) and phenylephrine (PE, vasoconstrictor) on aortic stiffness measured by aortic pulse wave velocity (aPWV) assessed by invasive pressure catheterization in anaesthetized Sprague-Dawley rats ( n = 7). This was compared with nondrug-dependent alteration of blood pressure through reduced venous return induced by partial vena cava occlusion. In vivo drug concentration was estimated by modeling clearance rates. Ex vivo responses of excised thoracic and abdominal aortic rings to drugs was measured using myography. SNP administration did not alter aPWV compared with venous occlusion ( P = 0.21–0.87). There was a 5% difference in aPWV with PE administration compared with venous occlusion ( P < 0.05). The estimated in vivo maximum concentration of PE (7.0 ± 1.8 ×10−7M) and SNP (4.2 ± 0.6 ×10−7M) caused ex vivo equivalent contraction of 52 mmHg (thoracic) and 112 mmHg (abdominal) and relaxation of 96% (both abdominal and thoracic), respectively, despite having a negligible effect on aPWV in vivo. This study demonstrates that vasoactive drugs administered to alter systemic blood pressure have a negligible effect on aPWV and provide a useful tool to study pressure-normalized and pressure-dependent aPWV in large conduit arteries in vivo. However, similar drug concentrations affect aortic ring wall tension ex vivo. Future studies investigating in vivo and ex vivo kinetics will need to elucidate mechanisms for this marked difference.