bluuebunny/crossref_metadata_2025 huggingface dataset:
Near- and Far-Field Pressure Skewness and Kurtosis in Heated Supersonic Jets From Round and Chevron Nozzles
Authors: Mora Pablo , Heeb Nick , Kastner Jeff , Gutmark Ephraim J. , Kailasanath K.
Published: November 2013

When the turbulent structures in the shear layer of high-speed jets travel at supersonic convective speeds relative to the ambient speed of sound, they radiate Mach waves that become the dominant component of the overall perceived noise. This is consistent with the OASPL in the far field reaching a maximum in same direction as the Mach wave angle. When the speed of the supersonic jet exceeds a certain level, the steepening of the wave-front in the near field produces a noise feature called “crackle.” Both pressure wave steepening and crackle cannot be recognized in the spectrum of the pressure signal, but in the temporal waveform of the pressure. The statistics of the pressure signal and its time derivative, particularly skewness, have become standard measures of crackle in heated supersonic jets. Previous studies showed that it is possible to reduce far-field pressure skewness with the implementation of notched and chevron nozzles, and to mitigate Mach Wave radiation with secondary flow techniques. In this paper, we investigate the effect of chevrons on the pressure and dP/dt high-order statistics of a Md = 1.5 converging-diverging round conical nozzle, both in the near and far fields. Cold and heated jets, To = 300 K and 600 K, are tested at over, design, and under-expanded conditions. Far-field results of the heated jet showed that chevrons effectively reduce elevated levels of skewness and kurtosis of the pressure and dP/dt. These reductions are remarkable especially around the Mach Wave angle, the region in which high-order statistics tend to propagate. Near-field results corroborated the effectiveness of chevrons in the skewness reduction.
A Unified Nonlinear Approach to Fault Diagnosis of Aircraft Engines
Authors: Zhang Xiaodong , Avram Remus C. , Tang Liang , Roemer Michael J.
Published: November 2013

Many existing aircraft engine diagnostic methods are based on linearized engine models. However, the dynamics of aircraft engines are highly nonlinear and rapidly changing. Future engine health management designs will benefit from new methods that are directly based on intrinsic nonlinearities of the engine dynamics. In this paper, a fault detection and isolation (FDI) method is developed for aircraft engines by utilizing nonlinear adaptive estimation and nonlinear observer techniques. Engine sensor faults, actuator faults and component faults are considered under one unified nonlinear framework. The fault diagnosis architecture consists of a fault detection estimator and a bank of nonlinear fault isolation estimators. The fault detection estimator is used for detecting the occurrence of a fault, while the bank of fault isolation estimators is employed to determine the particular fault type or location after fault detection. Each isolation estimator is designed based on the functional structure of a particular fault type under consideration. Specifically, adaptive estimation techniques are used for designing the isolation estimators for engine component faults and actuator faults, while nonlinear observer techniques are used for designing the isolation estimators for sensor faults. The FDI architecture has been integrated with the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) engine model developed by NASA researchers in recent years. The engine model is a realistic representation of the nonlinear aero thermal dynamics of a 90,000-pound thrust class turbofan engine with high-bypass ratio and a two-spool configuration. Representative simulation results and comparative studies are shown to verify the effectiveness of the nonlinear FDI method.
Interaction Between Swirl Number Fluctuations and Vortex Shedding in a Single-Nozzle, Turbulent, Swirling, Fully-Premixed Combustor
Authors: Bunce Nicholas A. , Quay Bryan D. , Santavicca Domenic A.
Published: November 2013

Flame response to imposed velocity fluctuations is experimentally measured in a single-nozzle, turbulent, swirling, fully-premixed combustor. The flame transfer function is used to quantify the flame’s response to imposed velocity fluctuations. Both the gain and phase of the flame transfer function are qualitatively similar for all operating conditions tested. Flame transfer function gain exhibits alternating regions of decreasing gain with increasing forcing frequency followed by regions of increasing gain with increasing forcing frequency. This alternating behavior gives rise to gain extrema. Flame transfer function phase magnitude increases quasi-linearly with increasing forcing frequency. Deviations from the linear behavior occur in the form of inflection points. Within the field, the current understanding is that the flame transfer function gain extrema are caused by the constructive/destructive interference of swirl number fluctuations and vortex shedding. Phase-synchronized images of forced flames are acquired to investigate the presence/importance of swirl number fluctuations, which manifest as fluctuations in mean flame position, and vortex shedding in this combustor. Analysis of phase-synchronized flame images reveals that mean flame position fluctuations are present at forcing frequencies corresponding to flame transfer function gain minima but not at forcing frequencies corresponding to flame transfer function gain maxima. This observation contradicts the understanding that flame transfer function gain maxima are caused by the constructive interference of mean flame position fluctuations and vortex shedding since mean flame position fluctuations are shown not to exist at flame transfer function gain maxima. Further analysis of phase-synchronized flame images shows that the variation of mean flame position fluctuation magnitude with forcing frequency follows an inverse trend to the variation of flame transfer function gain with forcing frequency, i.e. when mean flame position fluctuation magnitude increases flame transfer function gain decreases and vice versa. Based on these observations it is concluded that mean flame position fluctuations are a subtractive effect. The physical mechanism through which mean flame position fluctuations decrease flame response is through the interaction of the flame with the Kelvin-Helmholtz instability of the mixing layer in the combustor. When mean flame position fluctuations are large the flame moves closer to the mixing layer and damps the Kelvin-Helmholtz instability due to the increased kinematic viscosity, fluid dilatation, and baroclinic production of vorticity with opposite sign associated with the high temperature reaction zone.
Combined Heat and Power Generation for a Small Municipality for District Heating Purposes, Using Different Fuels
Authors: Tourlidakis A. , Malkogianni A. , Karlopoulos E.
Published: November 2013

Environmental concerns related to climate change are forcing many countries to consider implementing cogeneration of heat and power with centralized heating systems (i.e. district heating networks) which are becoming increasingly widespread in many countries. Combined heat and power (CHP) or cogeneration is the simultaneous production of electricity and useful thermal energy. The big interest this technology is receiving, both globally and locally, has its reason in the chance of reducing fuel consumption by enhancing energy production processes. The considerable amount of waste heat associated to traditional power stations is transformed into useful heat, which can be sent through the district network to houses and buildings for heating or cooling. Considering the pollution district heating reduce local pollutants such as dust, sulphur dioxide and nitrogen oxides by replacing exhausts from individual boilers. In addition to the reduced use of fuels, far more effective pollution prevention and control measures can be taken in central production facilities.

The purpose of this paper is to present the results of the investigation for the installation of a small-scale CHP plant for District Heating purposes in a small municipality in Northern Greece.

Initially the heat and electricity demands were estimated based on a combination of historical consumption data, the construction features of the buildings and the weather conditions in the region.

A pipe network was designed and sized appropriately and the utilization of a CHP plant was studied.

Additionally, a number of various fuel options were considered such as natural gas, oil, pulverised coal and biomass from crop and forest residues, and also animal waste. The availability in biomass in the local region was estimated and it was found that it could cover a small percentage of approximately 5% of the required heating power.

Finally, a techno-economic analysis was carried out and the CO2 reduction benefits were estimated.
Large-Eddy Simulation for Turbine Heat Transfer
Authors: Medic Gorazd , Joo Jongwook , Milanovic Ivana , Sharma Om
Published: November 2013

Heat transfer in a high-pressure turbine configuration (from an experiment documented in [1–2]) has been analyzed by means of large-eddy simulation. Blair’s large-scale rotating rig consists of a first stator, a rotor and an exit stator. Flow and heat transfer in the first stator are assessed for two configurations — with and without the presence of turbulence generating grid. A particular challenge here is that turbulence grid generates fairly high levels of inlet turbulence with turbulence intensity (TU) of about 10% just upstream of leading edge; this in turn moves the transition location upstream in a dramatic fashion. As far as the rotor blade is concerned, the flow and heat transfer is also analyzed experimentally for a range of incidence angles assessing the pressure side heat transfer increase at negative incidence angles. Several challenging aspects relevant to flow in the rotor are also considered — the three-dimensionality of pressure side flow separation at negative incidence, the impact of upstream stator wakes, as well as the role of surface roughness.
Adaptive Control of Balance of Plant Components in a Fuel Cell Gas Turbine Power Plant Simulator
Authors: Tsai Alex , Tucker David , Perez Eduardo
Published: November 2013

The performance of a 300kW Solid Oxide Fuel Cell Gas Turbine (SOFC-GT) pilot power plant simulator is evaluated with the use of a model reference adaptive control (MRAC) scheme, implemented for empirical Transfer Functions. The SOFC-GT simulator allows testing of various Fuel Cell (FC) models under a Hardware-in-the-Loop configuration that incorporates a 120kW APU, and Balance-of-Plant (BoP) components in hardware, and a FC model in software. The study of the nonlinear behavior of the BoP components, representative of the cathode airflow side of the FC under the MRAC scheme is compared against that of a linear decentralized PI controller for two FC operating points. The adaptation technique used in the MIMO system through separate SISO loops is beneficial to plants having a wide range of operation, and strong coupling interaction, as is presently the case. The practical implementation of the adaptive methodology is presented through simulation in the MATLAB/SIMULINK environment.
Mechanical Behaviour and Microstructure Correlation in a Selective Laser Melted Superalloy
Authors: Brodin Håkan , Andersson Olov , Johansson Sten
Published: November 2013

Selective laser melting (SLM), or, as the industry standard denotes the process, laser sintering, is an additive manufacturing process where metal powder is melted by a laser source layer-wise, forming a solid, dense metallic component. With the SLM process, near net shape components can be manufactured directly from a CAD model. The model is sliced into thin (max 100μm thick) layers. Powder is spread onto a metallic build platform and the powder is fused by a laser as dictated by the CAD model. The laser energy is intense enough to permit full melting (welding) of the particles to form solid metal. The process is repeated layer by layer until the part is complete.

A number of materials are available, including steel, aluminium, titanium and, in recent time, also superalloys. The material investigated in the current project is an alloy in agreement with the composition of Haynes International Hastelloy X, a solution strengthened superalloy typically used in large welded components exposed to high temperatures in oxidizing as well as reducing environments.

Microstructurally, the material is different from both a hot-rolled, as well as a cast material due to the manufacturing process. Since the SLM process involves laser melting of powder particles in the size range of <50μm, the structure resembles of a weld structure, however on a smaller scale. Due to the layer-by-layer build strategy, the material will exhibit anisotropy. Different heat treatment approaches can be adopted in order to homogenize the material and to minimize the effect of anisotropy. A stress relieve heat treatment was adopted and compared to the findings of the as manufactured SLM material.

The current project focuses on evaluating mechanical properties for a material manufactured by the SLM process and comparing to data for established manufacturing processes. For evaluation of the mechanical properties, low cycle fatigue testing and tensile testing has been performed. The microstructure and material deformation / cracking are evaluated by light optical microscopy and SEM, where electron backscatter diffraction is used. Due to the weld-like structure, the material will be transversely isotropic in the as-manufactured condition with one symmetry plane perpendicular to the build direction. Any direction perpendicular to the build direction tends to give increased strength compared to a direction parallel to the build direction if monotonic data are concerned. If fatigue properties are concerned, the anisotropy is also obvious. It is shown that the differences in behaviour can be coupled to microstructure.
Flame and Flow Dynamics of a Self-Excited, Standing Wave Circumferential Instability in a Model Annular Gas Turbine Combustor
Authors: O’Connor Jacqueline , Worth Nicholas A. , Dawson James R.
Published: November 2013

Azimuthal instabilities are prevalent in annular gas turbine combustors; these instabilities have been observed in industrial systems and research combustors, and have been predicted in simulations. Recent experiments in a model annular combustor have resulted in self-excited, circumferential instability modes at a variety of operating conditions. The instability mode “drifts” between standing and spinning waves, both clockwise and counter-clockwise rotating, during the course of operation. In this study, we analyze the flame response to standing wave modes by comparing the flame dynamics in a self-excited annular combustor with the flame dynamics in a single nozzle, transverse forcing rig. In the model annular combustor, differences in flame fluctuation have been observed at the node and anti-node of the standing pressure wave. Flames at the pressure anti-node display symmetric fluctuations, while flames at the pressure node execute asymmetric, flapping motions. This flame motion has been measured using both OH* chemiluminescence and planar laser induced fluorescence of OH radicals. To better understand these flame dynamics, the time-resolved velocity fields from a transverse forcing experiment are presented, and show that such a configuration can capture the symmetric and asymmetric disturbance fields at similar frequency ranges. Using high-speed PIV in multiple planes of the flow, it has been found that symmetric ring vortex shedding is driven by pressure fluctuations at the pressure anti-node whereas helical vortex disturbances drive the asymmetric flame disturbances at pressure nodes. By comparing the results of these two experiments, we are able to more fully understand flame dynamics during self-excited combustion instability in annular combustion chambers.
Development of a Flame Transfer Function Framework for Transversely Forced Flames
Authors: O’Connor Jacqueline , Acharya Vishal
Published: November 2013

This paper describes a framework for the development of a flame transfer function for transversely forced flames. While extensive flame transfer function measurements have been made for longitudinally forced flames, the disturbance field characteristics governing the flame response of a transversely forced flame are different enough to warrant separate investigation. In this work, we draw upon previous investigations of the flame disturbance pathways in a transversely forced flame to describe the underlying mechanisms that govern the behavior of the flame transfer function. Previous transverse forcing studies have shown that acoustic coupling in the nozzle region can result in both transverse and longitudinal acoustic fluctuations at the flame, and that the acoustic coupling is a function of combustor geometry, and hence, frequency. The results presented here quantify this coupling across a large range of frequencies using a velocity transfer function, FTL. The shape of the velocity transfer function gain indicates that there is strong acoustic coupling between the main combustor section and the nozzle at certain frequencies. Next, measured flame transfer functions are compared with results from theory. These theoretical results are derived from two level-set models of flame response to velocity disturbance fields, where velocity inputs are derived from experimental results. Data at several test conditions are presented and larger implications of this research are described with respect to gas turbine combustor design.
Realistic Trench Film Cooling With a Thermal Barrier Coating and Deposition
Authors: Kistenmacher David A. , Davidson F. Todd , Bogard David G.
Published: November 2013

Thermal barrier coatings (TBC’s) see extensive use in high temperature gas turbines. However, little work has been done to experimentally characterize the combination of TBC and film cooling. The purpose of this study is to investigate the cooling performance of a thermally conducting turbine vane with a realistic film cooling trench geometry embedded in TBC. Additionally, the effect of contaminant deposition on the realistic trench was studied. The trench is termed realistic because it takes into account probable manufacturing limitations. The vane model and TBC used for this study were designed to match the thermal behavior of an actual gas turbine vane with TBC by properly scaling their convective heat transfer coefficients, thermal conductivities, and characteristic length scales. This study built upon previously published results with various film cooling geometries consisting of round holes, craters, an ideal trench, and a novel trench. The previous study showed that large changes in blowing ratio resulted in negligible effects on cooling performance. Changes to film cooling geometry also resulted in minor effects on cooling performance. This study found that the realistic trench and an idealized trench perform similarly. However, the width of the realistic trench left the vane wall more exposed to mainstream temperatures, especially at lower film coolant flow rates. This study also found that the trench designs helped to mitigate deposition formation better than round holes; however, the realistic trench was more prone to deposition within the trench. The overall cooling effectiveness was similar for both trench designs and relatively unchanged from the pre-deposition performance while the overall cooling effectiveness for round holes increased due to the additional thermal insulation offered by the unmitigated deposition.
The Development of a Model for the Assessment of Bio-Fouling in Gas Turbine System
Authors: Onabanjo Tosin , Di Lorenzo Giuseppina , Goodger Eric , Pilidis Pericles
Published: November 2013

A significant problem encountered in the gas turbine industry with fuel products is the degradation of fuel and fuel systems by microorganisms, which are largely bacteria, embedded in biofilms. These microorganisms cause system fouling and other degradatory effects, extending often to sudden failure of components with cost implications. Current methods of assessment are only post-impact evaluation and do not necessarily quantify the effects of fuel degradation on engine performance and emission. Therefore, effective models that allow predictive condition monitoring are required for engine’s fuel system reliability, especially with readily biodegradable biofuels. The aim of this paper is to introduce the concept of bio-fouling in gas turbines and the development of a bio-mathematical model with potentials to predict the extent and assess the effects of microbial growth in fuel systems. The tool takes into account mass balance stoichiometry equations of major biological processes in fuel bio-fouling. Further development, optimization and integration with existing Cranfield in-house simulation tools will be carried out to assess the overall engine performance and emission characteristics. This new tool is important for engineering design decision, optimization processes and analysis of microbial fuel degradation in gas turbine fuels and fuel systems.
Performance Analysis of Organic Rankine Cycle With Preliminary Design of Radial Turbo Expander for Binary-Cycle Geothermal Plants
Authors: Wang Xing , Liu Xiaomin , Zhang Chuhua
Published: November 2013

In order to produce less emission of greenhouse gas, many studies have been done on the binary-cycle geothermal power plant to obtain the better performance. The radial turbo expander plays an important role in the performance of Organic Rankine Cycle (ORC) for binary-cycle geothermal plants. However, few studies have investigated the effect of parameters of radial turbo expander on the performance of ORC. In this paper, a new thermodynamic model of ORC coupled with the preliminary design of radial turbo expanders is developed. The effects of geothermal water temperature on the ORC performance parameters such as power output and thermal efficiency are investigated by using the proposed thermodynamic model. The variation of radial turbo expanders’ parameters such as specific rotational speed with geothermal water temperature is revealed. In the present study, the more reasonable efficiency of radial turbo expanders by using the preliminary design is adapted to analysis the performance of ORC, and more accuracy reference about the effect of geothermal source on the parameters of radial turbo expanders is obtained.
Biot-Number Analogy for Design of Experiments in Turbine Cooling
Authors: Shih Tom I.-P. , Ramachandran Saiprashanth Gomatam
Published: November 2013

Cooling of turbine components that come in contact with the hot gases strongly affects the turbine’s efficiency and service life. Designing effective and efficient cooling configurations requires detailed understanding on how geometry and operating conditions affect the way coolant cools the turbine materials. Experimental measurements that can reveal such information are difficult and costly to obtain because gas turbines operate at high temperatures (up to 2,000 K), high pressures (30+ bar), and the dimensions of many key features in the cooling configurations are small (millimeters or smaller). This paper presents a method that enables experiments to be conducted at near room temperatures, near atmospheric pressures, and using scaled-up geometries to reveal the temperature and heat-flux distributions within turbine materials as if the experiments were conducted under engine operating conditions. The method is demonstrated by performing conjugate CFD analyses on two test problems. Both problems involve a TBC-coated flat plate exposed to a hot-gas environment on one side and coolant flow on the other. In one problem, the heat transfer on the coolant side is enhanced by inclined ribs. In the other, it is enhanced by an array of pin fins.

This conjugate CFD study is based on 3-D steady RANS closed by the shear-stress-transport turbulence model for the fluid phase and the Fourier law for the solid phase. Results obtained show that, of the dimensionless parameters that are important to this problem, it is the Biot number that dominates. This study also shows that for two geometrically similar configurations, if the Biot number distributions on the corresponding hot-gas and coolant sides are nearly matched, then the magnitude and contours of the non-dimensional temperature and heat-flux distributions in the material will be nearly the same for the two configurations — even though the operating temperatures and pressures differ considerably. Thus, experimental measurements of temperature and heat-flux distributions within turbine materials that are obtained under ‘laboratory’ conditions could be scaled up to provide meaningful results under ‘engine’ relevant conditions.
Elastomer–Fuel Compatibility Studies With Alternative Jet Fuels for Dynamic Seal Applications
Authors: Jeyashekar Nigil , Frame Ed , Wilson George , Hutzler Scott , O’Brien Shayla
Published: November 2013

Alternative jet fuels (Fischer-Tropsch fuels and Biomass derived fuels) lack aromatic compounds and does not provide the desired seal-swell characteristics and other needed “fit-for-purpose” (FFP) properties. The research need is to investigate the effect of alternative fuels and fuel blends on elastomer seals in a simulated turbojet engine environment. In light of this research need, this paper describes the laboratory bench top apparatus that evaluates the engineering performance of elastomer o-rings exposed to alternative fuels and fuel blends under dynamic conditions. The three elastomer materials selected for dynamic tests were Fluorosilicone, Viton, and Buna-N o-rings. The performance of the elastomer o-rings was determined in terms of failure time that was based on fuel leakage past the o-ring seals. Pre-test and post-test elastomer properties were measured. Performance-property envelopes were used as a metric to compare different elastomer materials exposed to the same fuel and further investigate the effect of different alternative fuels on elastomers under dynamic conditions. This paper presents and compares the results from the alternative fuel (R8) and a 50/50 blend containing R-8–JP-8 on all three elastomer materials in terms of performance-property envelope charts.
Jet Engine Bird Ingestion Simulations: Comparison of Rotating to Non-Rotating Fan Blades
Authors: Howard Samuel A. , Hammer Jeremiah T. , Carney Kelly S. , Pereira J. Michael
Published: November 2013

Bird strike events in commercial airliners are a fairly common occurrence. According to data collected by the US Department of Agriculture, over 80,000 bird strikes were reported in the period 1990–2007 in the US alone [1]. As a result, bird ingestion is an important factor in aero engine design and FAA certification. When it comes to bird impacts on engine fan blades, the FAA requires full-scale bird ingestion tests on an engine running at full speed to pass certification requirements. These rotating tests are complex and very expensive. To reduce development costs associated with new materials for fan blades, it is desirable to develop more cost effective testing procedures than full-scale rotating engine tests for material evaluation. An impact test on a non-rotating single blade that captures most of the salient physics of the rotating test would go a long way towards enabling large numbers of evaluative material screening tests.

NASA Glenn Research Center has been working to identify a static blade test procedure that would be effective at reproducing similar results as seen in rotating tests. The current effort compares analytical simulations of a bird strike on various non-rotating blades to a bird strike simulation on a rotating blade as a baseline case. Several different concepts for simulating the rotating loads on a non-rotating blade were analyzed with little success in duplicating the deformation results seen in the rotating case. The rotating blade behaves as if it were stiffer than the non-rotating blade resulting in less plastic deformation from a given bird impact. The key factor limiting the success of the non-rotating blade simulations is thought to be the effect of gyroscopics. Prior to this effort, it was anticipated the difficulty would be in matching the pre-stress in the blade due to centrifugal forces Additional work is needed to verify this assertion, and to determine if a static test procedure can simulate the gyroscopic effects in a suitable manner. This paper describes the various non-rotating concepts analyzed, and demonstrates the effect believed to be gyroscopic in nature on the results.
A New 1.5-Stage Turbine Wheelspace Hot Gas Ingestion Rig (HGIR): Part I — Experimental Test Vehicle, Measurement Capability and Baseline Results
Authors: Palafox Pepe , Ding Zhongman , Bailey Jeremy , Vanduser Todd , Kirtley Kevin , Moore Kenneth , Chupp Raymond
Published: November 2013

An introduction is given to a new rotating wheelspace test vehicle known as the GE Hot Gas Ingestion Rig (HGIR). This scaled 1.5 stage turbine rig is configured similar to a current generation heavy duty gas turbine. It has a broad spectrum of measurement capability, including radial and circumferential ports for CO2 measurements that are used to measure the sealing effectiveness from candidate rim seal geometries. Engine-matched conditions are presented in a non-dimensional form that demonstrate the value of this fully capable test facility, including static pressure signatures at stage 1 nozzle exit, exit Reynolds number, exit Mach number and rotational Reynolds number. This paper also provides details of the operating conditions and assessment of a thermal steady-state condition achieved consistently throughout each test. Part I of this two-part paper focuses on the geometric details of this new state-of-the-art wheelspace rig, the measurement capabilities currently available and planned, and the results from the baseline geometry. The test data from this test vehicle are used to validate reduced order models, including unsteady CFD models. Details of the CFD modeling and validation are presented in the Part II paper Ding et al. [1]. Measurement uncertainties for all key parameters as well as the repeatability of the test rig to reproduce test conditions are presented to demonstrate the rigor taken in the design and operation of this testing facility.
Distance‐preserving rigidity penalty on deformable image registration of multiple skeletal components in the neck
Authors: Kim Jihun , Matuszak Martha M. , Saitou Kazuhiro , Balter James M.
Published: November 2013

Purpose:

This study aims at developing and testing a novel rigidity penalty suitable for the deformable registration of tightly located skeletal components in the head and neck from planning computed tomography (CT) and daily cone‐beam CT (CBCT) scans of patients undergoing radiotherapy.

Methods:

The proposed rigidity penalty is designed to preserve intervoxel distances within each bony structure. This penalty was tested in the intensity‐based B‐spline deformable registration of five cervical vertebral bodies (C1–C5). The displacement vector fields (DVFs) from the registrations were compared to the DVFs generated by using rigid body motions of the cervical vertebrae, measured by the surface registration of vertebrae delineated on CT and CBCT images. Twenty five pairs of planning CT (reference) and treatment CBCTs (target) from five patients were aligned without and with the penalty. An existing penalty based on the orthonormality of the deformation gradient tensor was also tested and the effects of the penalties compared.

Results:

The mean magnitude of the maximum registration error with the proposed distance‐preserving penalty was (0.86, 1.12, 1.33) mm compared to (2.11, 2.49, 2.46) without penalty and (1.53, 1.64, 1.64) with the existing orthonormality‐based penalty. The improvement in the accuracy of the deformable image registration was also verified by comparing the Procrustes distance between the DVFs. With the proposed penalty, the average distance was 0.11 (σ 0.03 mm) which is smaller than 0.53 (0.1 mm) without penalty and 0.28 (0.04 mm) with the orthonormality‐based penalty.

Conclusions:

The accuracy of aligning multiple bony elements was improved by using the proposed distance‐preserving rigidity penalty. The voxel‐based statistical analysis of the registration error shows that the proposed penalty improved the integrity of the DVFs within the vertebral bodies.
Novel multimodality segmentation using level sets and Jensen‐Rényi divergence
Authors: Markel Daniel , Zaidi Habib , El Naqa Issam
Published: November 2013

Purpose:

Positron emission tomography (PET) is playing an increasing role in radiotherapy treatment planning. However, despite progress, robust algorithms for PET and multimodal image segmentation are still lacking, especially if the algorithm were extended to image‐guided and adaptive radiotherapy (IGART). This work presents a novel multimodality segmentation algorithm using the Jensen‐Rényi divergence (JRD) to evolve the geometric level set contour. The algorithm offers improved noise tolerance which is particularly applicable to segmentation of regions found in PET and cone‐beam computed tomography.

Methods:

A steepest gradient ascent optimization method is used in conjunction with the JRD and a level set active contour to iteratively evolve a contour to partition an image based on statistical divergence of the intensity histograms. The algorithm is evaluated using PET scans of pharyngolaryngeal squamous cell carcinoma with the corresponding histological reference. The multimodality extension of the algorithm is evaluated using 22 PET/CT scans of patients with lung carcinoma and a physical phantom scanned under varying image quality conditions.

Results:

The average concordance index (CI) of the JRD segmentation of the PET images was 0.56 with an average classification error of 65%. The segmentation of the lung carcinoma images had a maximum diameter relative error of 63%, 19.5%, and 14.8% when using CT, PET, and combined PET/CT images, respectively. The estimated maximal diameters of the gross tumor volume (GTV) showed a high correlation with the macroscopically determined maximal diameters, with aR2 value of 0.85 and 0.88 using the PET and PET/CT images, respectively. Results from the physical phantom show that the JRD is more robust to image noise compared to mutual information and region growing.

Conclusions:

The JRD has shown improved noise tolerance compared to mutual information for the purpose of PET image segmentation. Presented is a flexible framework for multimodal image segmentation that can incorporate a large number of inputs efficiently for IGART.
Four‐dimensional Monte Carlo simulations demonstrating how the extent of intensity‐modulation impacts motion effects in proton therapy lung treatments
Authors: Dowdell Stephen , Grassberger Clemens , Paganetti Harald
Published: November 2013

Purpose:

To compare motion effects in intensity modulated proton therapy (IMPT) lung treatments with different levels of intensity modulation.

Methods:

Spot scanning IMPT treatment plans were generated for ten lung cancer patients for 2.5Gy(RBE) and 12Gy(RBE) fractions and two distinct energy‐dependent spot sizes (σ ∼8–17 mm and ∼2–4 mm). IMPT plans were generated with the target homogeneity of each individual field restricted to <20% (IMPT20%). These plans were compared to full IMPT (IMPTfull), which had no restriction on the single field homogeneity. 4D Monte Carlo simulations were performed upon the patient 4DCT geometry, including deformable image registration and incorporating the detailed timing structure of the proton delivery system. Motion effects were quantified via comparison of the results of the 4D simulations (4D‐IMPT20%, 4D‐IMPTfull) with those of a 3D Monte Carlo simulation (3D‐IMPT20%, 3D‐IMPTfull) upon the planning CT using the equivalent uniform dose (EUD), V95 and D1‐D99. The effects in normal lung were quantified using mean lung dose (MLD) and V90%.

Results:

For 2.5Gy(RBE), the mean EUD for the large spot size is 99.9% ± 2.8% for 4D‐IMPT20% compared to 100.1% ± 2.9% for 4D‐IMPTfull. The corresponding values are 88.6% ± 8.7% (4D‐IMPT20%) and 91.0% ± 9.3% (4D‐IMPTfull) for the smaller spot size. The EUD value is higher in 69.7% of the considered deliveries for 4D‐IMPTfull. The V95 is also higher in 74.7% of the plans for 4D‐IMPTfull, implying that IMPTfull plans experience less underdose compared to IMPT20%. However, the target dose homogeneity is improved in the majority (67.8%) of plans for 4D‐IMPT20%. The higher EUD and V95 suggests that the degraded homogeneity in IMPTfull is actually due to the introduction of hot spots in the target volume, perhaps resulting from the sharper in‐target dose gradients. The greatest variations between the IMPT20% and IMPTfull deliveries are observed for patients with the largest motion amplitudes. These patients would likely be treated using gating or another motion mitigation technique, which was not the focus of this study.

Conclusions:

For the treatment parameters considered in this study, the differences between IMPTfull and IMPT20% are only likely to be clinically significant for patients with large (>20 mm) motion amplitudes.
Room-Temperature Quantum Bit Storage Exceeding 39 Minutes Using Ionized Donors in Silicon-28
Authors: Saeedi Kamyar , Simmons Stephanie , Salvail Jeff Z. , Dluhy Phillip , Riemann Helge , Abrosimov Nikolai V. , Becker Peter , Pohl Hans-Joachim , Morton John J. L. , Thewalt Mike L. W.
Published: November 2013

Long-Lived Donors

Quantum computing in materials such as silicon would simplify integration with existing electronic components; however, the coherence times of such qubits, especially at room temperature, are affected by the interaction with the busy environment of a solid. Eliminating isotopic impurities from the host material improves coherence times, as observed for qubits, based on the nuclear spin of neutral P donors in Si.

Saeedi
et al.

(p.
830
) modified this system by using charged P donors instead of neutral ones; by manipulating the states of the donors optically and using dynamical decoupling, the coherence time of the qubits was extended to 3 hours at cryogenic temperatures and 39 minutes at room temperature.
The Man Who Bottled Evolution
Authors: Pennisi Elizabeth
Published: November 2013

Richard Lenski's 25-year experiment in bacterial evolution shows no signs of running out of surprises about how mutation and selection shape living things.
Turning Up the Light
Authors: Service Robert F.
Published: November 2013

Photovoltaic materials called perovskites work wonders in the lab, but will they shine as commercial technology?
Simultaneous Detection of Antibodies against Apx Toxins ApxI, ApxII, ApxIII, and ApxIV in Pigs with Known and Unknown Actinobacillus pleuropneumoniae Exposure Using a Multiplexing Liquid Array Platform
Authors: Giménez-Lirola Luis G. , Jiang Yong-Hou , Sun Dong , Hoang Hai , Yoon Kyoung-Jin , Halbur Patrick G. , Opriessnig Tanja
Published: November 2013

Surveillance for the presence ofActinobacillus pleuropneumoniaeinfection in a population plays a central role in controlling the disease. In this study, a 4-plex fluorescent microbead-based immunoassay (FMIA), developed for the simultaneous detection of IgG antibodies to repeat-in-toxin (RTX) toxins (ApxI, ApxII, ApxIII, and ApxIV) ofA. pleuropneumoniae, was evaluated using (i) blood serum samples from pigs experimentally infected with each of the 15 knownA. pleuropneumoniaeserovars or withActinobacillus suis, (ii) blood serum samples from pigs vaccinated with a bacterin containingA. pleuropneumoniaeserovar 1, 3, 5, or 7, and (iii) blood serum samples from pigs with an unknownA. pleuropneumoniaeexposure status. The results were compared to those obtained in a previous study where a dual-plate complement fixation test (CFT) and three commercially available enzyme-linked immunosorbent assays (ELISAs) were conducted on the same sample set. On samples from experimentally infected pigs, the 4-plex Apx FMIA detected specific seroconversion to Apx toxins as early as 7 days postinfection in a total of 29 pigs inoculated with 14 of the 15A. pleuropneumoniaeserovars. Seroconversion to ApxII and ApxIII was detected by FMIA in pigs inoculated withA. suis. The vaccinated pigs showed poor humoral responses against ApxI, ApxII, ApxIII, and ApxIV. In the field samples, the humoral response to ApxIV and theA. pleuropneumoniaeseroprevalence increased with age. This novel FMIA (with a sensitivity of 82.7% and a specificity of 100% for the anti-ApxIV antibody) was found to be more sensitive and accurate than current tests (sensitivities, 9.5 to 56%; specificity, 100%) and is potentially an improved tool for the surveillance of disease and for monitoring vaccination compliance.
Characterization of Escherichia coli Isolates from Hospital Inpatients or Outpatients with Urinary Tract Infection
Authors: Toval Francisco , Köhler Christian-Daniel , Vogel Ulrich , Wagenlehner Florian , Mellmann Alexander , Fruth Angelika , Schmidt M. Alexander , Karch Helge , Bielaszewska Martina , Dobrindt Ulrich
Published: November 2013

Uropathogenic
Escherichia coli
(UPEC) is the most common cause of community- and hospital-acquired urinary tract infections (UTIs). Isolates from uncomplicated community-acquired UTIs express a variety of virulence traits that promote the efficient colonization of the urinary tract. In contrast, nosocomial UTIs can be caused by
E. coli
strains that differ in their virulence traits from the community-acquired UTI isolates. UPEC virulence markers are used to distinguish these facultative extraintestinal pathogens, which belong to the intestinal flora of many healthy individuals, from intestinal pathogenic
E. coli
(IPEC). IPEC is a diarrheagenic pathogen with a characteristic virulence gene set that is absent in UPEC. Here, we characterized 265 isolates from patients with UTIs during inpatient or outpatient treatment at a hospital regarding their phylogenies and IPEC or UPEC virulence traits. Interestingly, 28 of these isolates (10.6%) carried typical IPEC virulence genes that are characteristic of enteroaggregative
E. coli
(EAEC), Shiga toxin-producing
E. coli
(STEC), and atypical enteropathogenic
E. coli
(aEPEC), although IPEC is not considered a uropathogen. Twenty-three isolates harbored the
astA
gene coding for the EAEC heat-stable enterotoxin 1 (EAST1), and most of them carried virulence genes that are characteristic of UPEC and/or EAEC. Our results indicate that UPEC isolates from hospital patients differ from archetypal community-acquired isolates from uncomplicated UTIs by their spectrum of virulence traits. They represent a diverse group, including EAEC, as well as other IPEC pathotypes, which in addition contain typical UPEC virulence genes. The combination of typical extraintestinal pathogenic
E. coli
(ExPEC) and IPEC virulence determinants in some isolates demonstrates the marked genome plasticity of
E. coli
and calls for a reevaluation of the strict pathotype classification of EAEC.
Rapid Detection of Mycobacterium tuberculosis and Pyrazinamide Susceptibility Related topncAMutations in Sputum Specimens through an Integrated Gene-to-Protein Function Approach
Authors: Li Heng , Chen Jun , Zhou Man , Geng Xuelei , Yu Junping , Wang Weihua , Zhang Xian-En , Wei Hongping
Published: November 2013

Testing the pyrazinamide (PZA) susceptibility ofMycobacterium tuberculosisisolates is challenging. In a previous paper, we described the development of a rapid colorimetric test for the PZA susceptibility ofM. tuberculosisby a PCR-basedin vitro-synthesized-pyrazinamidase (PZase) assay. Here, we present an integrated approach to detectM. tuberculosisand PZA susceptibility directly from sputum specimens.M. tuberculosiswas detected first, using a novel long-fragment quantitative real-time PCR (LF-qPCR), which amplified a fragment containing the wholepncAgene. Then, the positive amplicons were sequenced to find mutations in thepncAgene. For new mutations not found in the Tuberculosis Drug Resistance Mutation Database (www.tbdreamdb.com), thein vitroPZase assay was used to test the PZA resistance. This approach could detectM. tuberculosiswithin 3 h with a detection limit of 7.8 copies/reaction and report the PZA susceptibility within 2 days. In an initial testing of 213 sputum specimens, the LF-qPCR found 53 positive samples with 92% sensitivity and 97% specificity compared to the culture test forM. tuberculosisdetection. DNA sequencing of the LF-qPCR amplicons revealed that 49 samples were PZA susceptible and 1 was PZA resistant. In the remaining 3 samples, with newpncAmutations, thein vitroPZase assay found that 1 was PZA susceptible and 2 were PZA resistant. This integrated approach provides a rapid, efficient, and relatively low-cost solution for detectingM. tuberculosisand PZA susceptibility without culture.
Fatal Empyema Thoracis Caused by Schizophyllum commune with Cross-Reactive Cryptococcal Antigenemia
Authors: Chan Jasper F. W. , Teng Jade L. L. , Li Iris W. S. , Wong Sally C. Y. , Leung Sally S. M. , Ho Po-On , To Kelvin K. W. , Lau Susanna K. P. , Woo Patrick C. Y. , Yuen Kwok-Yung
Published: November 2013

We report a fatal case of
Schizophyllum commune
empyema thoracis with cross-reactive cryptococcal antigenemia.
In vitro
testing confirmed the ability of the fungus to cause a positive
c
ryptococcal
a
ntigen
l
atex
a
gglutination
s
ystem (CALAS) test result. Such a result may lead to delay in diagnosis and treatment, as most strains of
S. commune
are resistant to fluconazole.
A Fishy Tale: a Man with Empyema Caused by Streptococcus halichoeri
Authors: Foo Rui Min , Chan Douglas
Published: November 2013

In 2004, veterinary laboratories in the United Kingdom reported a novel Lancefield group B streptococcus,
Streptococcus halichoeri
, in seals. We report a case of
Streptococcus halichoeri
causing postoperative empyema in a patient. A search of the literature revealed that this is the first case of
S. halichoeri
ever reported in humans.
Inosine-Mediated Modulation of RNA Sensing by Toll-Like Receptor 7 (TLR7) and TLR8
Authors: Sarvestani Soroush T. , Tate Michelle D. , Moffat Jessica M. , Jacobi Ashley M. , Behlke Mark A. , Miller Alistair R. , Beckham Simone A. , McCoy Claire E. , Chen Weisan , Mintern Justine D. , O'Keeffe Meredith , John Matthias , Williams Bryan R. G. , Gantier Michael P.
Published: November 2013

RNA-specific adenosine deaminase (ADAR)-mediated adenosine-to-inosine (A-to-I) editing is a critical arm of the antiviral response. However, mechanistic insights into how A-to-I RNA editing affects viral infection are lacking. We posited that inosine incorporation into RNA facilitates sensing of nonself RNA by innate immune sensors and accordingly investigated the impact of inosine-modified RNA on Toll-like receptor 7 and 8 (TLR7/8) sensing. Inosine incorporation into synthetic single-stranded RNA (ssRNA) potentiated tumor necrosis factor alpha (TNF-α) or alpha interferon (IFN-α) production in human peripheral blood mononuclear cells (PBMCs) in a sequence-dependent manner, indicative of TLR7/8 recruitment. The effect of inosine incorporation on TLR7/8 sensing was restricted to immunostimulatory ssRNAs and was not seen with inosine-containing short double-stranded RNAs or with a deoxy-inosine-modified ssRNA. Inosine-mediated increase of self-secondary structure of an ssRNA resulted in potentiated IFN-α production in human PBMCs through TLR7 recruitment, as established through the use of a TLR7 antagonist and
Tlr7
-deficient cells. There was a correlation between hyperediting of influenza A viral ssRNA and its ability to stimulate TNF-α, independent of 5′-triphosphate residues, and involving Adar-1. Furthermore, A-to-I editing of viral ssRNA directly enhanced mouse Tlr7 sensing, when present in proportions reproducing biologically relevant levels of RNA editing. Thus, we demonstrate for the first time that inosine incorporation into immunostimulatory ssRNA can potentiate TLR7/8 activation. Our results suggest a novel function of A-to-I RNA editing, which is to facilitate TLR7/8 sensing of phagocytosed viral RNA.