bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical and Experimental Investigation of Membrane Wing for Micro Aerial Vehicle Applications
Authors: Petrović Igor , Shea Sean P. , Smith Ian P. , Kosel Franc , Marzocca Pier
Published: March 2015

Micro-Air-Vehicles (MAV) flight regimes differs significantly from larger scales airplanes. They are operating at low Reynolds numbers of approximate 104, cruising at speed about 12m/s, and are capable of agile maneuvers in limited space environment. They are compact and easily stowable to facilitate transportation. However, due to the small size, they are usually more vulnerable to the wind gusts with significant complexities associated to their flight mechanics, stability and control, which also makes difficult to quantify flight qualities and performances. Furthermore, complex aerodynamics can produce loading scenarios leading to the destruction of the vehicle during flight operation. To minimize the size of the MAV when not in use, their wings are stowed within the body of the vehicle, and are deployed during operation. To supplement the bulk of knowledge in MAV aero-mechanics, the study of the aerodynamic characteristics of a deformable membrane MAV wing is carried out in this paper. The analysis of the membrane airfoil is performed using a fluid-structure interaction 2D model, to select a set of optimal airfoil parameters for the intended flight regime. Numerical simulations are supplied and validated with an M AV model tested in the wind tunnel.
Design Method for Lattice-Skin Structure Fabricated by Additive Manufacturing
Authors: Tang Yunlong , Zhao Yaoyao Fiona
Published: March 2015

Parts with complex geometry structure can be produced by AM without significant increase of fabrication time and cost. One application of AM technology is to fabricate customized lattice-skin structure which can enhance performance of products with less material and less weight. However, most of traditional design methods only focus on design at macro-level with solid structure. Thus, a design method which can generate customized lattice-skin structure for performance improvement and functionality integration is urgently needed. In this paper, a novel design method for lattice-skin structure is proposed. In this design method, FSs and FVs are firstly generated according to FRs. Then, initial design space is created by filling FVs and FSs with selected lattice topology and skin, respectively. In parallel to the second step, initial parameters of lattice-skin structure are calculated based on FRs. Finally, TO method is used to optimize parameter distribution of lattice structure with the help of mapping function between TO’s result and lattice parameters. The design method proposed in this paper is proven to be efficient with case study and provides an important foundation for wide adoption of AM technologies in industry.
Numerical Analysis of Tool Performance in Up Milling of Ti-6Al-4V Alloy
Authors: Ma J. , Andrus Patrick , Duong Nick H. , Fischer Marissa , Condoor Sridhar , Lei Shuting
Published: March 2015

Ti-6Al-4V is widely used in industry because of its high strength-to-weight ratio at elevated temperatures, its excellent resistance to fracture and corrosion, and biological properties. However, Ti-6Al-4V is classified as hard-to-cut material because of its high chemical reactivity with most tool materials and its low thermal conductivity that causes high temperature on the tool face. Consequently, prediction of the tool temperature distribution has great significance in predicting tool wear pattern. In this research, Finite Element Method (FEM) is employed to conduct numerical investigation of the effects of cutting conditions (cutting speed, feed/tooth, and axial depth of cut) in corner up milling on temperature of the tool rake face. The tool material used is general carbide and the behavior of the workpiece Ti-6Al-4V is described by using Johnson-Cook plastic model. Because of the computational expense, a separate heat transfer model is built to analyze the heat transfer process after the tooth disengages the workpiece and before it engages the workpiece again to predict change of temperature distribution during this cooling process. This research provides helpful guidance for selecting tool cooling strategies in up milling Ti-6Al-4V alloy.
Multi-Sensor Detection and Estimation of Gaps When Drilling CFRP Composite Stacks
Authors: Eneyew Eshetu D. , Ramulu M.
Published: March 2015

To avoid the uncertainty of the presence of gaps between CFRP stacks and to eliminate the inspection for gaps after every drilled hole, a novel approach for on-line gap detection and estimation when drilling CFRP composite stacks through various signal profiles was proposed. Experimental investigation of the proposed method was conducted using thrust force, vibration, acoustic emission, and audio signals, which were collected using dynamometer, accelerometer, acoustic emission sensors, and an air-coupled audio microphone respectively. A predetermined gap was introduced between the stacks of CFRP plates in the investigation. The results from this experimental study reveal the potentials of the proposed approach for on-line detection and estimation of gap when drilling CFRP composite stacks.
Exit Flow Vector Control on a Coanda Nozzle Using Dielectric Barrier Discharge Actuator
Authors: Páscoa José C. , Rodrigues Frederico F. , Das Shyam S. , Abdollahzadeh M. , Dumas A. , Trancossi Michele , Subhash Maharshi
Published: March 2015

The paper presents a study on a Coanda nozzle with applications in vectorized propulsion. The nozzle is able to change the exist flow angle as a function of a differential two-stream incoming flow rate. Herein we demonstrate that by using Dielectric Barrier Discharge actuators we are able to extend the range of attainable exit flow angles. First the analysis is performed using a numerical approach; afterwards an experimental facility is implemented to study this same effect. We include a comparison between the experimental testing on the Coanda thruster and CFD computations. Following an analysis of the results we demonstrate that it is possible to achieve a higher exit thrust angle, with the DBD plasma actuators active, and this is shown to be important in order to be able to keep the desired angles under several swirl velocities incoming from the feeding turbofans.
Wind Energy Production Using an Optimized Variable Pitch Vertical Axis Rotor
Authors: Xisto Carlos M. , Páscoa José C. , Leger Jakson A. , Trancossi Michele
Published: March 2015

The Cycloidal Vertical Axis Wind Turbine is based on a self-adjustable pitch concept that automatically pitches the blade to improve the azimuthal load distribution and energy conversion. In nominal operating point, theoretical and CFD analysis have demonstrated that a cycloidal turbine can be more efficient than classical VAWTs, being able to produce more energy at low and intermediate Tip-Speed-Ratios. This innovative cycloidal wind turbine can also eliminate some problems of self-starting in VAWTs. In the following paper we propose the introduction of a new generation of wind energy converter system. We will show, trough the use of numerical tools, that the proposed system is more efficient than classical VAWTs.
Combined Static and Dynamic Optimization of a Turbine Disk
Authors: Jun Li , Ning Fan , Xuecheng Zhao
Published: March 2015

Due to high working temperature and rotating speed, turbine disks are crucial parts in gas turbine engines. The weight of disks is always heavy in order to increase the reliability and structural integrity. So optimization design of disks could bring a significant reduction in engine weight. Focusing on a typical Low Pressure Turbine (LPT) disk, this paper improves its design in both static and dynamic characteristics with ANSYS Workbench platform. Based on a 2D parameterized model, the sensitivity of different structural parameters was investigated quickly. Then the optimization process to minimize the mass was conducted by NLPQL (Non-Linear Programming by Quadratic Lagrangian) method with 3D parameterized model. The equivalent stress of disk was limited in static optimization and resonance frequency was also restricted to a safe level through a Campbell diagram in dynamic optimization. A new design plan was acquired through optimization process, which reduces 13.6% of total weight under static and dynamic criteria.
Elastoplastic Analysis of the Erichsen Cupping Test Using Comsol Multiphysics FEM Code
Authors: Salazar Julio Alberto Boix , de Lange Dirk F. , Medellín Castillo Hugo I.
Published: March 2015

One of the standard procedures to test the formability of sheet material is the Erichsen cupping test, in which the metal sheet blank is held in its place over a circular space and depressed by a semi-spherical punch. The depth of depression that can be reached is the measure of the formability. In this work the elastoplastic deformation of the sheet is analyzed by multipurpose Finite Element Method software Comsol Multiphysics. The Comsol package is not specifically developed or focused on the analysis of solid mechanical problems with elastoplastic model behavior and contact problems, and still limited literature is available in which sheet forming processes are analyzed with Comsol. In this work, the development and testing of a simulation model in Comsol is reported and comparison is made with results reported with other FEM software.

The development and testing is realized in successive steps of increasing complexity. First a uniaxial stretching is simulated in order to evaluate the implementation of the elastoplastic material behavior. Next, the bending of a plate over a straight line is analyzed, adding the contact boundary condition between tool and sheet surface into the model. Finally, the axisymmetric model of the Erichsen cupping test is implemented.

It is found that the default Von Mises yield function results in incorrect stresses, and needs to be replaced by a yield function in which the Von Mises stress is calculated based on the Cauchy tensor. The non-linear contact condition is a source of oscillations in the local stresses near the zone where contact is established. The simulation results obtained with the final model are compared with punch forces, stresses and strains obtained in literature, showing an adequate comparison.
Analysis of Fluid Motion in Dynamic Stall and Forced Cylinder Flow Using Koopman Operator Methods
Authors: Glaz Bryan , Fonoberova Maria , Loire Sophie , Mezić Igor
Published: March 2015

Potential analogs between dynamics induced by periodic passage through a bifurcation critical value and the nonlinear dynamics associated with the aerodynamic dynamic stall problem are presented for the first time. Koopman operator methods are used to study the spectral features of a streamwise oscillating cylinder which exhibits wake dynamics due to externally forced oscillations through a Hopf bifurcation critical value. Koopman decomposition results show that the system transitions to a more continuous spectrum compared to the discrete spectrum associated with a stationary cylinder in post-critical flow. Finally, Fourier analysis of flow variables associated with an oscillating airfoil under dynamic stall conditions were compared with the oscillating cylinder spectra. The spectral characteristics of the two systems exhibited similar frequency broadening behavior induced by the externally forced oscillations. Therefore, the results indicate that the nonlinear dynamics associated with dynamic stall appear to have strong linkages to a system oscillating through a bifurcation critical value.
Numerical Simulation of Impact Events of the Ultimate Metallic Toe Cap Model for Safety Footwear
Authors: Costa Sérgio L. , Peixinho Nuno , Mendonça João P.
Published: March 2015

In this paper the normative impact-crash test in the context of the experimental validation of the last and final approved prototype model is focused. The project S3 – Safety Slim Shoe presents the potential to reduce the weight in safety toe cap components combining a new geometric redesign deeply associated to local stiffeners to realize the full potential of AHSS – Advanced High Strength Steels. The investigation aimed to investigate the potential energy absorption capacity for a substantial thickness reduction of a new engineering geometry with evaluative corrections for the specific impact test performance. A set of FEA - Finite Element Analysis of the plastic deformation mode was performed, and some material parameters such as: hardening effects and sensitivity for material constitutive parameters with demanding test strain rates were carried out. Experimental results of the toe cap deformation behavior confront a weight saving range of over 40%, compared with the original steel toe cap.
Low Frequency Vibration Consideration in Tool-Path Computation of Two-Link Serial Manipulator for Improved Accuracy
Authors: Juschanin Denis , Alemayehu Fisseha M. , Ekwaro-Osire Stephen
Published: March 2015

Industrial robots are flexible and cost-efficient tools for a multitude of applications such as, polishing, grinding, deburring, and welding. However, their utilization in machining tasks is currently limited due to insufficient position accuracy. This study aims to answer the research question: ‘Does including low frequency vibrations (mode coupling chatter) in tool path computation improve accuracy?’ For this purpose, the current paper focuses on setting-up a robust and flexible simulation framework. The framework implements a predictive cutting force method into a multibody dynamic (MBD) model of an industrial robot. The framework is structured in an extendable fashion for future research tasks. Future work will include mode coupling chatter into the MBD model to help mitigate the effects of chatter in robotic machining process, which in turn will increase tool-path accuracy.
Flow Characteristics of Porous Metal Structures for Specified Permeability Manufactured by Laser Beam Melting Technology
Authors: Benra F.-K. , Dohmen H. J. , Clauss S. , Sehrt J. T. , Witt G.
Published: March 2015

The characteristic additive build-up at the laser beam melting technology provides the opportunity to freeform porous and defined structures at specific areas in one part. By adjusting the process parameters specific characteristics of the manufactured part such as density, permeability, pore size, porosity and shear strength can be realized. The manufacturing process of a test body is described in detail.

The permeability of the manufactured parts is investigated experimentally. In addition a numerical model is build and the flow structure inside of the test body is illustrated. The numerically obtained results are compared to the experimentally obtained results.

To show the advantages of this technology for future applications a numerical model of a porous blade surrounded by a hot gas flow and cooled from inside of the porous structure is investigated. The results show that the method to define the characteristics during the laser beam melting process has to be optimized.
A Generalized Runge-Kutta Method for Stability Prediction of Milling Operations With Variable Pitch Tools
Authors: Niu Jinbo , Ding Ye , Zhu Limin , Ding Han
Published: March 2015

This paper extends the generalized Runge-Kutta method (GRKM) to predict the machining stability of milling systems with variable-pitch tools. Different from the uniform cutters with fixed pitch angles, the variation of tooth distribution angles of variable pitch cutters significantly affects the stability diagrams of the milling systems. From the viewpoint of the regenerative chatter, the milling system with non-uniform tools is governed by a delayed differential equation (DDE) with multiple delays. Afterwards, the GRKM, an approach verified with high computational accuracy and efficiency for DDEs with a single delay, is extended to tackle the milling systems with multiple delays based on Floquet theory. Besides the pitch angles, other geometry parameters of the cutter are also taken into consideration, such as the helix angle, which is proved with limited influence on the stability lobes. With the objective of maximizing productivity, the resultant stability charts provide valuable reference for the geometry design of variable-pitch cutters and for the choice of machining parameters, i.e. the spindle speed and the depth of cut.
Thermodynamic Non-Dimensional Model to Estimate the Emitted Greenhouse Gases of a Turbofan Engine at Flight Altitude
Authors: Eshraghi Hamzeh , Ghaseminezhad Ali , Boroomand Masoud , Tousi Abolghasem M.
Published: March 2015

Non-dimensional simulation models are often used to interpret experimental data in order to better understand the combustion processes. Recent investigation has presented a thermodynamic non-dimensional model which is used for evaluating the emitted greenhouse gases of a turbofan engine at flight altitude. Combustion chamber flow has been modeled as a non-dimensional flow in provided model. Required data for this model are combustion chamber inlet, turbine inlet and outlet together with exit nozzle pressure and temperature which are calculated by gas turbine non-dimensional modeling software. In this regard mass flow and rotational speed compatibility, conservation of mass and energy equations have been solved. (GSP and KineTechs software (chemical kinetic solving software) have been used for solving the mentioned equations as well as modeling the non-dimensional flow in the combustion chamber, respectively.) This paper investigates the JT9D engine. The results have been validated with experimental data published by International Civil Aviation Organization (ICAO). Noteworthy is that the obtained experimental data have been considered for low flight altitude phases and therefore the presented model takes into account the Greenhouse Gases estimation values for the mentioned phases. After result validation and conformity of experimental data, engine cruise altitude conditions have been modeled. Subsequently, New York – London airway has been studied and emitted Greenhouse gases quantity at cruise altitude has been calculated in one year while verified with published official Statistical data.
Effects of Blade Leading Edge Fillet on Near Wall Pressure and Heat Transfer in a Linear Turbine Cascade
Authors: Mahmood Gazi I. , Acharya Sumanta
Published: March 2015

Thermal stresses and failure of components in the gas turbine passages are common due to exposure of the passage walls to extremely hot combustion gasses. In addition, the gas turbine engine efficiency suffers due to secondary flows and passage vortex formations in turbine passages. Investigations are being conducted to reduce the thermal stresses and secondary flows in the turbine passages with endwall modifications and film cooling. The present investigation employs two types of fillets at the junction of blade leading edge and endwall in a low speed linear blade cascade to control the effects of passage vortex. Blade and endwall static pressure, axial vorticity and air temperature near endwall, and Nusselt numbers on endwall and blade wall are measured and presented in the cascade passage with and without the leading edge fillets. A constant Reynolds number of 233,000 based on the blade chord and the inlet velocity is employed for the measurements. The blade profile is obtained from the hub-side of first stage blade in the GE-E3 gas turbine and scaled 10 times in the present cascade. One of the two fillet shapes has a linear profile from the blade to endwall (Filet 1), and the other has a parabolic profile (Fillet 2) from the blade to endwall. Fillets are employed only at the blade leading edge at the bottom endwall. Results on axial vorticity and air temperature indicate that the fillets weaken passage vortex and reduce heat transfer from the endwall. This occurs as the pitchwise endwall pressure difference from the pressure side to the suction side is reduced near the filleted region. However, the distributions of wall static pressure coefficients and Nusselt numbers along the blade surface are about the same with and without the fillets and indicate no effects from the fillets on the blade surface. The blade-loadings are thus unaffected and require no design modifications with the fillets. The endwall Nusselt number distributions show lower values for the fillets than for the baseline (without fillets) which also indicate reduced heat transfer to or from the endwall. The results of the present investigations thus can be applied in designing the blade passages where the secondary flow effects are passively controlled and endwall thermal stresses are reduced.
Silanized Graphene-Based Nanocomposite Coatings on Fiber Reinforced Composites Against the Environmental Degradations
Authors: Diouf D. , Asmatulu R.
Published: March 2015

This report presents the development of graphene-based nanocomposite coatings on the fiber reinforced composites to improve the coating resistance against the corrosion and other environmental weathering. Graphene nanoflakes were initially functionalized through a silanization process, and then dispersed well into the polyurethane primer and top coats at 0, 2, 4 and 8wt% using high speed agitation and sonication processes. The dispersed nanocomposite coatings were an air sprayed on the surfaces of the composite coupons at different thicknesses, and cured prior to the alternative UV and salt fog exposure tests for 20 days. The performance analyses of the nanocomposite coatings were carried out using atomic force microscopy (AFM), Fourier transform infrared spectrometer (FTIR), thickness measurements, water contact angle, and electro-chemical impedance spectroscopy tests. The test results indicated that the silanization process on the graphene nanoflakes significantly improved the corrosion resistances of the nanocomposite coatings when compared to the non-functionalized graphenes. This study may be useful for the performance improvements of many coatings on the composite aircraft, wind turbines and other applications.
Optimizing the Efficiency in Direct Laser Deposition Process Using Vibrations of Nozzle to Control the Flow of Powder
Authors: Nazir Kamran , Sohn Chang Hyun , Hassan Fahad , Awais Muhammad , Ali Muhammad , Miran Sajjad
Published: March 2015

In direct laser deposition (DLD), metallic powder is injected into the melt pool in order to join different metals to develop fully dense and near net shape part. The cost of powder wasted in commercial DLD machines has been a major concern to the industries. More than 60% of the powder is wasted and is being disposed off which make the system economically and environmentally expensive. Recycling of powder is not feasible in many sectors, because of the fear of drop in the quality of the product. The objective of this study is to enhance the deposition efficiency of the DLD process, so that to minimize the amount of powder wasted. In present study, flow of powder is achieved by vibration of the powder delivery nozzle at sonic frequencies. Experimental studies are performed to analyze the deposition of powder by varying laser intensities, powder flow rate and laser scanning speed. The mass flow during certain time is weighed and the actual clad weight that is formed during the same period is weighted. The difference of the two is used to calculate the powder efficiency. Different set of experiments are performed. Powder mass flow rates are increased subsequently and Taguchi matrix are prepared for each set of experiment. Mass flow rate in initial experiments is from 0.044 grams/sec to 0.244 g/s and increases up to 0.86 g/s in the final set of experiments. Laser power during these experiments varies between 1KW to 2 KW, while laser scanning speeds varies from 100 mm/min to 350 mm/min. Maximum deposition efficiency is achieved in initial set of experiments and is up to 70%, which is significant improvement in the form of deposition efficiencies available in literature.
Design and Internal Flow Analysis of a Ducted Contra-Rotating Axial Flow Fan
Authors: Mohammadi Ali , Boroomand Masoud
Published: March 2015

This paper presents the design procedure of a ducted contra-rotating axial flow fan and investigates the flow behavior inside it using ANSYS CFX-15 flow solver. This study investigates parameters such as pressure ratio, inlet mass flow rate and efficiency in different operating points. This system consists of two rotors with an outer diameter of 434 mm and an inner diameter of 260 mm which rotate contrary to each other with independent nominal rotational speeds of 1300 rpm. Blades’ maximum thickness and rotational speeds of each rotor will be altered as well as the axial distance between the two rotors to investigate their effect on the overall performance of the system. Designed to deliver a total pressure ratio of 1.005 and a mass flow rate of 1.8 kg/s at nominal rotational speeds, this system proves to be much more efficient compared to the conventional rotor-stator fans. NACA-65 airfoils are used in this analysis with the necessary adjustments at each section. Inverse design method is used for the first rotor and geometrical constraints are employed for the second one to have an axial inlet and outlet flow without using any inlet or outlet guide vanes. Using free vortex swirl distribution method, characteristic parameters and the necessary data for 3D generation of this model are obtained. The appropriate grid is generated using ATM method in ANSYS TurboGrid and the model is simulated in CFX-15 flow solver by employing k-ε turbulence model in the steady state condition. Both design algorithm and simulation analysis confirm the high anticipated efficiency for this system. The accuracy of the design algorithm will be explored and the most optimum operating points in different rotational speed ratios and axial distances will be identified. By altering the outlet static pressure of the system, the characteristic map is obtained.
Ultimate Strength of Aircraft Structures
Authors: Coburn Todd
Published: March 2015

Strength analysis of aircraft structures focuses on static strength, fatigue, and damage tolerance of the materials. Countless hours are invested in quantifying the static strength, which is allowed to fully yield under ultimate loads so that the structure can be designed as light and efficient as possible. This analysis is critical to a lightweight initial design, but is also of great importance in the evaluation of engineering modifications and repairs. Analysis of the critical sections often resorts to plastic bending analysis, and use of E.F. Bruhn’s Iterative Slice Method, or Cozzone’s Simplified Method for Symmetric Sections, is often employed. Yet these methods fall short when the critical section includes thin flanges that buckle or cripple prior to ultimate failure, as is generally the case for frames, floor beams, stringers, and other structural members used on aircraft. This paper presents a solution to this shortfall, and introduces a hybrid procedure for calculating the ultimate strength of a cross section that accounts for material non-linearity, flange stability, and other effects.
Analysis of Deep Hole Drilling in Presence of Electromagnetic Field Using Taguchi Technique
Authors: Najarian F. , Noordin M. Y. , Nor F. M. , Kurniawan D.
Published: March 2015

Electromagnetic field assisted machining is potential and is of particular interest to be explored to improve machining quality with minimum environmental effect. In this study, the effect of electromagnetic field on tool and workpiece is analyzed along with the effects of presence of drilling bush, feedrate, and spindle speed to the quality of hole for deep hole drilling. The effect of these control factors to the drilled hole’s cylindricity error and roundness error was determined using Taguchi technique. L16 orthogonal array design of experiments was used, with regression model was calculated and tested using analysis of variance. Spindle speed was found to be the only significant factor, with other factors did not give significant effect to roundness or cylindricity, except for tool magnetization which affected cylindricity. Issues with magnetization system are likely hinder the magnetic field to exhibit potential to improve machining quality, and should be addressed for future study.
An Investigation of Carbon Nanotube Dispersion in Vinyl Ester Resin Using Mechanical, Thermal and Statistical Techniques
Authors: Sabet Seyed Morteza , Mahfuz Hassan , Hashemi Javad
Published: March 2015

The inclusion of 0.25 and 0.5 wt.% functionalized multi-walled carbon nanotubes (MWCNTs) into a vinyl ester (VE) resin has been studied. To investigate the effect of carbon nanotubes (CNTs) dispersion, the sonication process has been performed under a variety of parameters including mixing time and sonication amplitude. Differential scanning calorimetry (DSC) and 3-point flexural testing methods have been employed to explore the thermo-mechanical properties of materials. Differential scanning calorimetry results show up to 13°C increase in the glass transition temperature (Tg) of the VE polymer by introducing 0.25 wt.% CNTs with a total sonication energy of 60 KJ. It is also established that the flexural modulus of the polymer can be improved up to 24%. An array indentation technique has been used to evaluate the hardness and elastic modulus variations in the regions of nanoparticle concentration. The resulting variations along the indentation array have been statistically studied using three-parameter Weibull distribution. Based on the resulting dispersion conditions, the optimum sonication parameters and nanoparticle concentration have been determined.
Ion chamber absorbed dose calibration coefficients, ND,w, measured at ADCLs: Distribution analysis and stability
Authors: Muir B. R.
Published: March 2015

Purpose:

To analyze absorbed dose calibration coefficients, ND,w, measured at accredited dosimetry calibration laboratories (ADCLs) for client ionization chambers to study (i) variability among ND,w coefficients for chambers of the same type calibrated at each ADCL to investigate ion chamber volume fluctuations and chamber manufacturing tolerances; (ii) equivalency of ion chamber calibration coefficients measured at different ADCLs by intercomparing ND,w coefficients for chambers of the same type; and (iii) the long‐term stability of ND,w coefficients for different chamber types by investigating repeated chamber calibrations.

Methods:

Large samples of ND,w coefficients for several chamber types measured over the time period between 1998 and 2014 were obtained from the three ADCLs operating in the United States. These are analyzed using various graphical and numerical statistical tests for the four chamber types with the largest samples of calibration coefficients to investigate (i) and (ii) above. Ratios of calibration coefficients for the same chamber, typically obtained two years apart, are calculated to investigate (iii) above and chambers with standard deviations of old/new ratios less than 0.3% meet stability requirements for accurate reference dosimetry recommended in dosimetry protocols.

Results:

It is found that ND,w coefficients for a given chamber type compared among different ADCLs may arise from differing probability distributions potentially due to slight differences in calibration procedures and/or the transfer of the primary standard. However, average ND,w coefficients from different ADCLs for given chamber types are very close with percent differences generally less than 0.2% for Farmer‐type chambers and are well within reported uncertainties.

Conclusions:

The close agreement among calibrations performed at different ADCLs reaffirms the Calibration Laboratory Accreditation Subcommittee process of ensuring ADCL conformance with National Institute of Standards and Technology standards. This study shows that ND,w coefficients measured at different ADCLs are statistically equivalent, especially considering reasonable uncertainties. This analysis of ND,w coefficients also allows identification of chamber types that can be considered stable enough for accurate reference dosimetry.
New precise dates for the ancient and sacred coral pyramidal tombs of
Leluh
(Kosrae, Micronesia)
Authors: Richards Zoe T. , Shen Chuan-Chou , Hobbs Jean-Paul A. , Wu Chung-Che , Jiang Xiuyang , Beardsley Felicia
Published: March 2015

Dating of coral tombs sheds light on ancient trans-oceanic civilization.
Gene therapy rescues disease phenotype in a spinal muscular atrophy with respiratory distress type 1 (SMARD1) mouse model
Authors: Nizzardo Monica , Simone Chiara , Rizzo Federica , Salani Sabrina , Dametti Sara , Rinchetti Paola , Del Bo Roberto , Foust Kevin , Kaspar Brian K. , Bresolin Nereo , Comi Giacomo P. , Corti Stefania
Published: March 2015

Preclinical proof-of-principle data demonstrate the high efficacy of IGHMBP2 gene therapy in the SMARD1 mouse model as well as in an in vitro model of the human disease.
Quantum walks and wavepacket dynamics on a lattice with twisted photons
Authors: Cardano Filippo , Massa Francesco , Qassim Hammam , Karimi Ebrahim , Slussarenko Sergei , Paparo Domenico , de Lisio Corrado , Sciarrino Fabio , Santamato Enrico , Boyd Robert W. , Marrucci Lorenzo
Published: March 2015

A discrete quantum walk occurs in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons.
Evidence of Active Methanogen Communities in Shallow Sediments of the Sonora Margin Cold Seeps
Authors: Vigneron Adrien , L'Haridon Stéphane , Godfroy Anne , Roussel Erwan G. , Cragg Barry A. , Parkes R. John , Toffin Laurent
Published: March 2015

In the Sonora Margin cold seep ecosystems (Gulf of California), sediments underlying microbial mats harbor high biogenic methane concentrations, fueling various microbial communities, such as abundant lineages of anaerobic methanotrophs (ANME). However, the biodiversity, distribution, and metabolism of the microorganisms producing this methane remain poorly understood. In this study, measurements of methanogenesis using radiolabeled dimethylamine, bicarbonate, and acetate showed that biogenic methane production in these sediments was mainly dominated by methylotrophic methanogenesis, while the proportion of autotrophic methanogenesis increased with depth. Congruently, methane production and methanogenic
Archaea
were detected in culture enrichments amended with trimethylamine and bicarbonate. Analyses of denaturing gradient gel electrophoresis (DGGE) fingerprinting and reverse-transcribed PCR-amplified 16S rRNA sequences retrieved from these enrichments revealed the presence of active methylotrophic
Methanococcoides
burtonii
relatives and several new autotrophic
Methanogenium
lineages, confirming the cooccurrence of
Methanosarcinales
and
Methanomicrobiales
methanogens with abundant ANME populations in the sediments of the Sonora Margin cold seeps.
Integrated Cryptosporidium Assay To Determine Oocyst Density, Infectivity, and Genotype for Risk Assessment of Source and Reuse Water
Authors: King Brendon , Fanok Stella , Phillips Renae , Swaffer Brooke , Monis Paul
Published: March 2015

Cryptosporidium
continues to be problematic for the water industry, with risk assessments often indicating that treatment barriers may fail under extreme conditions. However, risk analyses have historically used oocyst densities and not considered either oocyst infectivity or species/genotype, which can result in an overestimation of risk if the oocysts are not human infective. We describe an integrated assay for determining oocyst density, infectivity, and genotype from a single-sample concentrate, an important advance that overcomes the need for processing multiple-grab samples or splitting sample concentrates for separate analyses. The assay incorporates an oocyst recovery control and is compatible with standard primary concentration techniques. Oocysts were purified from primary concentrates using immunomagnetic separation prior to processing by an infectivity assay. Plate-based cell culture was used to detect infectious foci, with a monolayer washing protocol developed to allow recovery and enumeration of oocysts. A simple DNA extraction protocol was developed to allow typing of any wells containing infectious
Cryptosporidium
. Water samples from a variety of source water and wastewater matrices, including a semirural catchment, wastewater, an aquifer recharge site, and storm water, were analyzed using the assay. Results demonstrate that the assay can reliably determine oocyst densities, infectivity, and genotype from single-grab samples for a variety of water matrices and emphasize the varying nature of
Cryptosporidium
risk extant throughout source waters and wastewaters. This assay should therefore enable a more comprehensive understanding of
Cryptosporidium
risk for different water sources, assisting in the selection of appropriate risk mitigation measures.
Sharing a Host Plant (Wheat [Triticum aestivum]) Increases the Fitness of Fusarium graminearum and the Severity of Fusarium Head Blight but Reduces the Fitness of Grain Aphids (Sitobion avenae)
Authors: Drakulic Jassy , Caulfield John , Woodcock Christine , Jones Stephen P. T. , Linforth Robert , Bruce Toby J. A. , Ray Rumiana V.
Published: March 2015

We hypothesized that interactions between fusarium head blight-causing pathogens and herbivores are likely to occur because they share wheat as a host plant. Our aim was to investigate the interactions between the grain aphid,
Sitobion avenae
, and
Fusarium graminearum
on wheat ears and the role that host volatile chemicals play in mediating interactions. Wheat ears were treated with aphids and
F. graminearum
inoculum, together or separately, and disease progress was monitored by visual assessment and by quantification of pathogen DNA and mycotoxins. Plants exposed to both aphids and
F. graminearum
inoculum showed accelerated disease progression, with a 2-fold increase in disease severity and 5-fold increase in mycotoxin accumulation over those of plants treated only with
F. graminearum
. Furthermore, the longer the period of aphid colonization of the host prior to inoculation with
F. graminearum
, the greater the amount of pathogen DNA that accumulated. Headspace samples of plant volatiles were collected for use in aphid olfactometer assays and were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-coupled electroantennography. Disease-induced plant volatiles were repellent to aphids, and 2-pentadecanone was the key semiochemical underpinning the repellent effect. We measured aphid survival and fecundity on infected wheat ears and found that both were markedly reduced on infected ears. Thus, interactions between
F. graminearum
and grain aphids on wheat ears benefit the pathogen at the expense of the pest. Our findings have important consequences for disease epidemiology, because we show increased spread and development of host disease, together with greater disease severity and greater accumulation of pathogen DNA and mycotoxin, when aphids are present.
Using Total Internal Reflection Fluorescence Microscopy To Visualize Rhodopsin-Containing Cells
Authors: Keffer J. L. , Sabanayagam C. R. , Lee M. E. , DeLong E. F. , Hahn M. W. , Maresca J. A.
Published: March 2015

Sunlight is captured and converted to chemical energy in illuminated environments. Although (bacterio)chlorophyll-based photosystems have been characterized in detail, retinal-based photosystems, rhodopsins, have only recently been identified as important mediators of light energy capture and conversion. Recent estimates suggest that up to 70% of cells in some environments harbor rhodopsins. However, because rhodopsin autofluorescence is low—comparable to that of carotenoids and significantly less than that of (bacterio)chlorophylls—these estimates are based on metagenomic sequence data, not direct observation. We report here the use of ultrasensitive total internal reflection fluorescence (TIRF) microscopy to distinguish between unpigmented, carotenoid-producing, and rhodopsin-expressing bacteria.
Escherichia coli
cells were engineered to produce lycopene, β-carotene, or retinal. A gene encoding an uncharacterized rhodopsin, actinorhodopsin, was cloned into retinal-producing
E. coli
. The production of correctly folded and membrane-incorporated actinorhodopsin was confirmed via development of pink color in
E. coli
and SDS-PAGE. Cells expressing carotenoids or actinorhodopsin were imaged by TIRF microscopy. The 561-nm excitation laser specifically illuminated rhodopsin-containing cells, allowing them to be differentiated from unpigmented and carotenoid-containing cells. Furthermore, water samples collected from the Delaware River were shown by PCR to have rhodopsin-containing organisms and were examined by TIRF microscopy. Individual microorganisms that fluoresced under illumination from the 561-nm laser were identified. These results verify the sensitivity of the TIRF microscopy method for visualizing and distinguishing between different molecules with low autofluorescence, making it useful for analyzing natural samples.
Pseudomycoicidin, a Class II Lantibiotic from Bacillus pseudomycoides
Authors: Basi-Chipalu Shradha , Dischinger Jasmin , Josten Michaele , Szekat Christiane , Zweynert Annegret , Sahl Hans-Georg , Bierbaum Gabriele
Published: March 2015

Lantibiotics are ribosomally synthesized antimicrobial peptides with substantial posttranslational modifications. They are characterized by the unique amino acids lanthionine and methyllanthionine, which are introduced by dehydration of Ser/Thr residues and linkage of the resulting dehydrated amino acids with Cys residues. BLAST searches using the mersacidin biosynthetic enzyme (MrsM) in the NCBI database revealed a new class II lantibiotic gene cluster in
Bacillus pseudomycoides
DSM 12442. Production of an antimicrobial substance with activity against Gram-positive bacteria was detectable in a cell wash extract of this strain. The substance was partially purified, and mass spectrometric analysis predicted a peptide of 2,786 Da in the active fraction. In order to characterize the putative lantibiotic further, heterologous expression of the predicted biosynthetic genes was performed in
Escherichia coli
. Coexpression of the prepeptide (PseA) along with the corresponding modification enzyme (PseM) resulted in the production of a modified peptide with the corresponding mass, carrying four out of eight possible dehydrations and supporting the presence of four thioether and one disulfide bridge. After the proteolytic removal of the leader, the core peptide exhibited antimicrobial activity. In conclusion, pseudomycoicidin is a novel lantibiotic with antimicrobial activity that was heterologously produced in
E. coli
.
Nitrite Control over Dissimilatory Nitrate/Nitrite Reduction Pathways in Shewanella loihica Strain PV-4
Authors: Yoon Sukhwan , Sanford Robert A. , Löffler Frank E.
Published: March 2015

Shewanella loihica
strain PV-4 harbors both a functional denitrification (NO
3
−
→N
2
) and a respiratory ammonification (NO
3
−
→NH
4
+
) pathway. Batch and chemostat experiments revealed that NO
2
−
affects pathway selection and the formation of reduced products. Strain PV-4 cells grown with NO
2
−
as the sole electron acceptor produced exclusively NH
4
+
. With NO
3
−
as the electron acceptor, denitrification predominated and N
2
O accounted for ∼90% of reduced products in the presence of acetylene. Chemostat experiments demonstrated that the NO
2
−
:NO
3
−
ratio affected the distribution of reduced products, and respiratory ammonification dominated at high NO
2
−
:NO
3
−
ratios, whereas low NO
2
−
:NO
3
−
ratios favored denitrification. The NO
2
−
:NO
3
−
ratios affected
nirK
transcript abundance, a measure of denitrification activity, in the chemostat experiments, and cells grown at a NO
2
−
:NO
3
−
ratio of 3 had ∼37-fold fewer
nirK
transcripts per cell than cells grown with NO
3
−
as the sole electron acceptor. In contrast, the transcription of
nrfA
, implicated in NO
2
−
-to-NH
4
+
reduction, remained statistically unchanged under continuous cultivation conditions at NO
2
−
:NO
3
−
ratios below 3. At NO
2
−
:NO
3
−
ratios above 3, both
nirK
and
nrfA
transcript numbers decreased and the chemostat culture washed out, presumably due to NO
2
−
toxicity. These findings implicate NO
2
−
as a relevant modulator of NO
3
−
fate in
S. loihica
strain PV-4, and, by extension, suggest that NO
2
−
is a relevant determinant for N retention (i.e., ammonification) versus N loss and greenhouse gas emission (i.e., denitrification).
Organic Amendments to Avocado Crops Induce Suppressiveness and Influence the Composition and Activity of Soil Microbial Communities
Authors: Bonilla Nuria , Vida Carmen , Martínez-Alonso Maira , Landa Blanca B. , Gaju Nuria , Cazorla Francisco M. , de Vicente Antonio
Published: March 2015

One of the main avocado diseases in southern Spain is white root rot caused by the fungus
Rosellinia necatrix
Prill. The use of organic soil amendments to enhance the suppressiveness of natural soil is an inviting approach that has successfully controlled other soilborne pathogens. This study tested the suppressive capacity of different organic amendments against
R. necatrix
and analyzed their effects on soil microbial communities and enzymatic activities. Two-year-old avocado trees were grown in soil treated with composted organic amendments and then used for inoculation assays. All of the organic treatments reduced disease development in comparison to unamended control soil, especially yard waste (YW) and almond shells (AS). The YW had a strong effect on microbial communities in bulk soil and produced larger population levels and diversity, higher hydrolytic activity and strong changes in the bacterial community composition of bulk soil, suggesting a mechanism of general suppression. Amendment with AS induced more subtle changes in bacterial community composition and specific enzymatic activities, with the strongest effects observed in the rhizosphere. Even if the effect was not strong, the changes caused by AS in bulk soil microbiota were related to the direct inhibition of
R. necatrix
by this amendment, most likely being connected to specific populations able to recolonize conducive soil after pasteurization. All of the organic amendments assayed in this study were able to suppress white root rot, although their suppressiveness appears to be mediated differentially.
Processing Environment and Ingredients Are Both Sources of Leuconostoc gelidum, Which Emerges as a Major Spoiler in Ready-To-Eat Meals
Authors: Pothakos Vasileios , Stellato Giuseppina , Ercolini Danilo , Devlieghere Frank
Published: March 2015

Mesophilic and psychrotrophic organism viable counts, as well as high-throughput 16S rRNA gene-based pyrosequencing, were performed with the aim of elucidating the origin of psychrotrophic lactic acid bacteria (LAB) in a ready-to-eat (RTE) meal manufacturing plant. The microbial counts of the products at the end of the shelf life were greatly underestimated when mesophilic incubation was implemented due to overlooked, psychrotrophic members of the LAB.
Pseudomonas
spp.,
Enterobacteriaceae
,
Streptococcaceae
, and
Lactobacillus
spp. constituted the most widespread operational taxonomic units (OTUs), whereas
Leuconostoc
gelidum
was detected as a minor member of the indigenous microbiota of the food ingredients and microbial community of the processing environment, albeit it colonized samples at almost every sampling point on the premises. However,
L. gelidum
became the most predominant microbe at the end of the shelf life. The ability of
L. gelidum
to outgrow notorious, spoilage-related taxa like
Pseudomonas
,
Brochothrix
, and
Lactobacillus
underpins its high growth dynamics and severe spoilage character under refrigeration temperatures. The use of predicted metagenomes was useful for observation of putative gene repertoires in the samples analyzed in this study. The end products grouped in clusters characterized by gene profiles related to carbohydrate depletion presumably associated with a fast energy yield, a finding which is consistent with the fastidious nature of highly competitive LAB that dominated at the end of the shelf life. The present study showcases the detrimental impact of contamination with psychrotrophic LAB on the shelf life of packaged and cold-stored foodstuffs and the long-term quality implications for production batches once resident microbiota are established in the processing environment.