bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitrocytotoxicity and antiviral efficacy against feline herpesvirus type 1 of famciclovir and its metabolites
Authors: Groth Allyson D. , Contreras Marcos T. , Kado‐Fong Helen K. , Nguyen Kyvan Q. , Thomasy Sara M. , Maggs David J.
Published: October 2013

Objectives

To assessin vitrothe antiviral efficacy against feline herpesvirus (FHV‐1) and cytotoxicity for cultured feline cells of famciclovir and its metabolites,BRL42359 and penciclovir. To investigate the effect of timing of penciclovir application onin vitroantiviral activity.

Procedures

Plaque reduction assays were used to estimate antiviral efficacy of all compounds and the effect of penciclovir exposure before or after exposure to aFHV‐1 field isolate. Cytotoxicity was evaluated by assessing cell morphology and viable cell number for 72 h following exposure to each compound.

Results

The penciclovir concentration that inhibitedFHV‐1‐induced plaque formation by 50% (IC50) was 0.86 μg/mL (3.4 μm). Famciclovir andBRL42359 had no antiviral effect againstFHV‐1 at any concentration assessed. Antiviral activity was significantly enhanced when cells were exposed to 4 μmpenciclovir (approximate IC50) for 1 h but not for 24 h before viral adsorption. Delaying exposure of cells to penciclovir for 1, 2, or 4 h after viral adsorption significantly enhanced antiviral activity. Relative to untreated control wells, >88% of cells remained viable when exposed to famciclovir (100 μm),BRL42359 (1.06 mm), or penciclovir (40 μm) for 72 h. No morphologic evidence of cytotoxicity was noted.

Conclusions

Penciclovir demonstrates potent antiviral activity againstFHV‐1 and may be effective at lower tissue, tear, and plasma concentrations than previously targeted. The duration ofin vitroantiviral effect of penciclovir suggests that frequent famciclovir administration may be necessaryin vivo. Famciclovir andBRL42359 showed no signs ofin vitrocytotoxicity.
Temperature Field Prediction of Rectangular Shell-and-Tube Heat Exchanger
Authors: Zhou J. F. , Li Y. , Gu B. Q. , Shao C. L.
Published: October 2013

Shell-and-tube heat exchangers are the most common type of heat exchangers in oil refineries and other large chemical processes. In this manuscript, we demonstrate that the shell-side flow in a cylindrical shell was not as homogeneous as that in a rectangular shell. According to the periodic flow field and the arrangement of tubes in the rectangular shell, the solid-fluid coupling heat transfer model consisting of a single tube section and the outer and inner fluids was developed to represent the whole heat exchanger. Using this model, the relationship among four temperatures, namely the inlet and outlet temperatures of tube-side fluid and the upstream and downstream temperatures of shell-side fluid, was established. By dividing each tube into several tube sections at the sites of baffles, a method for predicting the temperature field of the rectangular shell-and-tube heat exchanger was proposed. Based on the node temperature correlation, all the node temperatures were obtained by iterative computation using the established relationship between the four temperatures and the operating conditions. It was found that the temperature distribution of the fluid in tube was approximately linear along axial direction, but the temperature of tube showed nonlinear regularity. The axial deformation compatibility condition for the tube bundle and shell was considered when resolving the stresses in tubes. For the model established in this paper, the mean temperature of the tube at lower position was found to be larger than that at higher position; hence the thermal expansion of the tube at the lower end is larger. In the case the tube-side fluid was heated, all tubes were pulled because of the larger axial thermal expansion of shell, and the stress in the tube with higher temperature is smaller because of the smaller strain.
Theoretical Analysis of Flocking Algorithms in Networks of Second Order Dynamic Agents With Switching Topologies
Authors: Atrianfar Hajar , Haeri Mohammad
Published: October 2013

This paper deals with a refined analysis and modification of existing results on the flocking algorithms proposed for the second order dynamic agents. In the present work, the limiting condition of ever connectivity is removed and it is proved that the flocking can be reached if only the union of the network proximity graphs during nonoverlapping time intervals becomes connected frequently enough. Also, it is proved that including a static virtual leader cannot model the group objective of achieving the desired velocity and it will stop eventually at a predefined point in the space. The convergence rate to this fixed point is determined too. The last contribution of this paper is definition of group configuration when only a fraction of agents are informed about the virtual leader.
Coupling of One-Dimensional and Two-Dimensional Hydrodynamic Models Using an Immersed-Boundary Method
Authors: Zhang Ning , Li Puxuan , He Anpeng
Published: October 2013

Numerical simulations of flooding events through rivers and channels require coupling between one-dimensional (1D) and two-dimensional (2D) hydrodynamic models. The rivers and channels are relatively narrow, and the widths could be smaller than the grid size used in the background 2D model. The shapes of the rivers and channels are often complex and do not necessarily coincide with the grid points. The coupling between the 1D and 2D models are challenging. In this paper, a novel immersed-boundary (IB) type coupling is implemented. Using this method, no predetermined linking point is required, nor are the discharge boundary conditions needed to be specified on the linking points. The linkage will be dynamically determined by comparing the water levels in the 1D channel and the surrounding dry cell elevations on the 2D background. The linking-point flow conditions, thus, can be dynamically calculated by the IB type implementation. A typical problem of the IB treatment, which is the forming of the nonsmooth zigzag shaped boundary, has not been observed with this method. This coupling method enables more realistic and accurate simulations of water exchange between channels and dry lands during a flooding event.
Three-Dimensional Viscous Potential Electrohydrodynamic Kelvin–Helmholtz Instability Through Vertical Cylindrical Porous Inclusions With Permeable Boundaries
Authors: Moatimid Galal M. , Hassan Mohamed A.
Published: October 2013

In this paper, the electrohydrodynamic three-dimensional Kelvin–Helmholtz instability of a cylindrical interface with heat and mass transfer between liquid and vapor phases is studied. The liquid and the vapor are saturated, two coaxial cylindrical porous layers, and the suction/injection velocities for the fluids at the permeable boundaries are also taken into account. The dispersion relation is derived and the stability analysis is discussed for various parameters. It is found that the streaming velocity has a destabilizing effect, while the axial electric field has a stabilizing one. The suction for both the liquid and the steam has a destabilizing effect in contrast with the injection at both boundaries. The flow through porous structure is more stable than the pure flow. The case of the axisymmetric (for zero value of the azimuthal wave number m) and asymmetric (for nonzero value of the azimuthal wave number m) disturbances at large wavelength (at the wave number k→0) are always stable. Meanwhile, it is the same dispersion relation for the plane geometry at large wave number. Finally, our results are corroborated by comparing them with the previous published results.
The Investigation of Plasma Produced by Intense Nanosecond Laser Ablation in Vacuum Under External Magnetic Field Using a Two-Stage Model
Authors: Tao Sha , Wu Benxin , Zhou Yun , Cheng Gary J.
Published: October 2013

In this paper a two-stage physics-based model has been applied to study the evolution of plasma produced by high-intensity nanosecond laser ablation in vacuum under external magnetic field. In the early stage (Stage I), the laser-induced plasma generation and its short-term evolution are described through one-dimensional (1D) hydrodynamic equations. An equation of state (EOS) that can cover the density and temperature range in the whole physical domain has been applied to supplement the hydrodynamic equations. In the later stage (Stage II), the plasma long-term evolution is simulated by solving 2D gas dynamic equations. The two-stage model can predict the spatial distributions and temporal evolutions of plasma temperature, density, velocity, and other parameters. The model is used to study and discuss the effects of external magnetic field on the plasma evolution. It provides a useful tool for related fundamental studies and practical applications.
Experimental Investigation on Aerodynamic Behavior of a Compressor Cascade in Droplet Laden Flow
Authors: Ober Birger , Joos Franz
Published: October 2013

The possibility to augment the power output of gas turbines by the use of water injection becomes more and more attractive in recent years as unsteadily available renewable energy sources become more present and the need of reserve power rises. Depending on the installed system, water injection may result in a two phase flow inside the compressor. The water droplet laden compressor flow promises benefits in efficiency and to some extent in performance and stability. A promising approach is the stabilizing influence on highly stressed airfoils as experimentally and numerically investigated by different research groups. Multiple numerical investigations have been undertaken by different research groups which found similar results. The ongoing experimental investigation presented in this paper focuses on the influence of a droplet laden flow on an axial compressors' aerodynamics over the range of relevant incidence flow angles. The result of the series of experiments is a comparison of a dry air compressor flow and a droplet laden air compressor flow at high velocity (Ma>0.85). The variables were water load and incidence angle. The discussion will investigate the effects of the presence of water droplet on the compressor cascade's discharge flow properties and their influence on the relevant performance parameters. For this a discussion of the loss coefficient the detailed discharge flow velocity and the axial velocity density ratio will take place.
Performance of a Turboshaft Engine for Helicopter Applications Operating at Variable Shaft Speed
Authors: Misté Gianluigi Alberto , Benini Ernesto
Published: October 2013

An off-design steady state model of a generic turboshaft engine has been implemented to assess the influence of variable free power turbine (FPT) rotational speed on overall engine performance, with particular emphasis on helicopter applications. To this purpose, three off-design flight conditions were simulated and engine performance obtained with different FTP rotational speeds were compared. In this way, the impact on engine performance of a particular speed requested from the main helicopter rotor could be evaluated. Furthermore, an optimization routine was developed to find the optimal FPT speed which minimizes the engine specific fuel consumption (SFC) for each off-design steady state condition. The usual running line obtained with constant design FPT speed is compared with the optimized one. The results of the simulations are presented and discussed in detail. As a final simulation, the main rotor speed Ω required to minimize the engine fuel mass flow was estimated taking into account the different requirements of the main rotor and the turboshaft engine.
Aerodynamic Shape Optimization of Air-Intakes of a Helicopter Turboshaft
Authors: Garavello A. , Russo M. , Comis da Ronco Claudio , Ponza R. , Benini E.
Published: October 2013

The research project HEAVYcOPTer, a sub task of the European R&D program Clean-Sky GRC2 [1], is devoted to the efficient design and the shape optimization of the Agusta Westland AW101 helicopter turboshaft engine intake and exhaust system, to be carried out by means of advanced multi-objective optimization algorithms coupled with CFD Navier-Stokes solvers. The present paper describes the outcomes of HEAVYcOPTer in relation to the air intakes shape optimisation activities. This paper describes the technical details of such program. The optimisation method chosen for the redesign of the engine installation involves the application of the state of the art genetic algorithm GDEA, developed at the University of Padova and successfully applied in several fluid-dynamics applications, especially in the field of turbomachinery. For the present application, the set of geometrical designs constituting the genetic algorithm population are generated by means of morphing the original CFD model surface mesh: shapes are applied to baseline surface nodes with a displacement intensity driven by the GA chosen scaling factors. Then, CFD models of new designs are automatically generated and analyzed by the flow solver, returning to the GA the evaluation of the selected objective functions required in order to evolve the population in the next step of the evolutionary process. AW101 intakes have been optimised following a multi-objective/multi-point approach, minimizing inlet total pressure loss in both hovering and forward flight conditions simultaneously; optimised solutions were also constrained so as to not exceed the total pressure distortion level at the engine aerodynamic interface plane, so as to ensure inlet/engine compatibility with respect to the compressor surge limit. This approach ensured the improvement of the engine/airframe integration efficiency for the overall rotorcraft flight envelop, reducing fuel burn and increasing the helicopter propulsive efficiency.
Effect of Impeller Blade Trimming on the Performance of a 5.5:1 Pressure Ratio Centrifugal Compressor
Authors: Swain Daniel , Engeda Abraham
Published: October 2013

Centrifugal compressor blade trimming can be used for the purpose of changing the performance characteristics of an impeller or allowing a single impeller design to be used for a range of operating conditions. There are a number of methods of impeller blade trimming that may be employed to change the impeller flowrate, the pressure ratio, or both; however, the limitations of blade trimming and the effect on the flow field are not well understood.

In this study, CFD is used to model the effects of three different methods of blade trimming on a single centrifugal compressor design. Impeller performance characteristics and analysis of the flow field are presented for a series of trims for each of the three trimming methods.

Each method of trimming was found to be limited at some point by choke. Shifting the original shroud profile both axially and radially in proportion to the desired flow coefficient allowed the pressure ratio and efficiency of the original impeller to be maintained while changing the flow coefficient. Trimming the blades along the meridional length in proportion to the desired new flow coefficient without regard to the original shroud profile produced similar results, but allowed the impeller to be trimmed further than was practical using the radial-axial shroud offset method. Trimming the blades axially so that the original shroud profile is maintained produced a change in pressure ratio while maintaining the original impeller flow coefficient.
Effect of Casing Geometry on Flow Characteristics in a Model Can-Combustor
Authors: Rahim Abdur , Alkhafagiy Dhirgham , Talukdar Prabal
Published: October 2013

In a gas turbine combustor, it is necessary to use a diffuser to decelerate the high velocity air stream delivered by the compressor and thus avoid high total pressure loss. The interaction between the diffuser and combustor external flows plays a key role in controlling the pressure loss, air flow distribution around the combustor liner. Flow through casing-liner annulus is crucial as it feeds air to the primary, secondary and dilution holes. It is important that the annulus flow has sufficient static pressure to achieve adequate penetration of the jets. Moreover, the correct proportion of air enters the combustor liner through the dome and the various ports to maintain stable operation and good quality outlet condition. Length of combustor can be reduced if a provision is made for sufficient diffusion in the dump region. In the present numerical study, three can-combustor models of different geometry with a constant dump-gap have been analyzed with emphasis on the flow through annulus. A comparison has been made amongst the three models in terms of flow uniformity, static pressure recovery and total pressure loss. It is observed that flow uniformity in the annulus region is improved if a small divergence in length and a curved shape step height casing is made.
CFD Code Validation and Qualitative Study of Effects of Tip Clearance Variation on Performance of Transonic Axial Compressor Rotor
Authors: Patkar Aniket R. , Rangasamy Srinivethan , Raghunath Sreekanth , Kalamkar Vilas
Published: October 2013

The main objective of this work is the validation of Computational Fluid Dynamics (CFD) code used for analysis of transonic axial compressors. NASA Rotor 35 is used here as test case for validation. In this work, computations are performed using parallelized RANS code, to predict the transonic axial compressor rotor flow characteristics. Advection Upstream Splitting Method (AUSM) scheme has been used. A Multiple Frame of Reference approach has been used to model the rotor passage. Spalart-Allmaras turbulence model is used to model turbulence. Multiblock Structured mesh is used. Performance characteristics for the entire range of operation, from maximum mass flow rate till maximum pressure ratio, have been simulated. The results obtained are comparable with experimental data within 5–10% error. Investigations have been carried out to study the effect of varying tip clearance in NASA Rotor 35. The present work is intended to study the clearance flow trajectory as a function of varying tip clearance. The effects of shock/vortex interaction in tip clearance region are also studied. The effects of tip clearance size on the generation and evolution of the end-wall vortical structures are discussed by investigating their evolutionary trajectories. By this study, it is observed that as tip clearance reduces, clearance flow trajectory moves downstream. From this it can be concluded that if tip clearance increases, tip clearance vortices expand. This may help in casing-treatment or tip-treatment to mitigate the loss in the performance, if the tip clearance increases.
Stall Margin Improvement in a Centrifugal Compressor Through Endwall Reshaping
Authors: Sope Suhas R. , Nagpurwala Quamber H.
Published: October 2013

This paper presents the results of numerical studies on the effect of endwall reshaping on the performance and stall margin of a centrifugal compressor. The endwall (shroud) of a baseline compressor was reshaped by introducing a convex hump at a location downstream of the inducer where the flow turns from axial to radial direction. The depth of the hump was varied as 3%, 6%, and 9% of the local impeller blade height. The impeller was also locally reshaped to match the shroud, maintaining the baseline tip clearance. Other geometric parameters of the reshaped impeller were kept same as those of the baseline impeller. An implicit, coupled, density based solver (ANSYS FLUENT) was used with first order upwind discretization scheme. The local reshaping of the endwall and impeller blades showed a positive tendency of increase in compressor stall margin without any appreciable reduction in efficiency. Endwall reshaping of 9% of the local blade height resulted in reducing the stall mass flow rate by 6.4 % of the baseline stall flow rate. Further, the peak total pressure ratio showed a marginal increase of 0.8%. Reshaping of the endwall was observed to cause local acceleration of the flow, thus weakening separation bubble and delaying inception of stall.
Effect of a Confined Outer Air Stream on Instability of an Annular Liquid Sheet Exposed to Gas Flow
Authors: Chatterjee Souvick , Samanta Samiran , Mukhopadhyay Achintya , Ghosh Koushik , Sen Swarnendu
Published: October 2013

A gas turbine combustor will act in a desired way only if its components, specially the fuel injector perform satisfactorily producing fine homogeneous droplets. Stability analysis of liquid, a rich classical fluid mechanics problem, when applied to fuel injector studies can enhance our knowledge leading towards the design of an advanced efficient atomizer. In this work, we analyzed the instability of a swirling annular liquid, exposed to co-flowing inner and outer air streams, by a temporal linear stability analysis using perturbation method. This temporal analysis discusses the effect of liquid Weber number, liquid swirl strength, both inner and outer gas-to-liquid velocity ratio and outer air gas swirl strength on the growth rate of interface instability. Another interesting inclusion in this work is the effect of confinement of the outer air stream which leads to a finite thickness of the outer air stream. Our results show a higher optimum growth rate obtained at a higher axial wave number in the presence of confinement compared to that when the outer air stream extends to infinity. This leads to the formation of smaller droplets which increases the efficiency of atomization. A comparative study between different helical modes revealed that the helical modes are dominant compared to the axisymmetric mode in presence of outer air swirl, whereas reverse phenomenon occurs in its absence.
Influence of Area Distribution With Fixed Trajectory on Serpentine Intake Duct Performance
Authors: Gaur Ritesh , Narayanan Vimala , Kishore Kumar S.
Published: October 2013

Performance of intake duct with fixed inlet trajectory and different area distributions have been analyzed using a commercial CFD (Computational Fluid Dynamics) software. The performance have been evaluated for fixed boundary conditions. The area distributions studied are defined by varying cross sectional area at different locations of intake duct by keeping the inlet and exit area same. The performance of the intake ducts are studied in terms of the pressure recovery coefficient, total pressure loss, pressure recovery factor and distortion coefficient in the present work. The motion caused by the change in centerline curvature is analyzed. The objective of the work is to derive a shape of the duct with minimum distortion of the flow and maximum pressure recovery.
A Numerical Investigation to Study Effects of a Savonius Rotor’s Plate Shape on its Optimum Overlap Ratio
Authors: Abbaszadeh Morteza , Bagherzadeh Fariba , Iravani Mina
Published: October 2013

Present study is aimed to investigate the relationship between blade shape of Savonius rotor and its optimum overlap, an important parameter that can improve the rotor’s performance superbly. To set a relation between rotor’s shape and its overlap, a new parameter called “trailing angle” was introduced in this study and by a novel design method, several models were designed to represent a wide range of trailing angles. The investigation has been carried out by using Reynolds Stress Method (RSM) through ANSYS Fluent commercial software package. The application of the method was validated by comparing the results of a conventional model with experimental data acquired from one of the references. Results of this study have proved that optimum overlap ratio is associated with blades’ trailing angle and by increasing the trailing angle, optimum overlap would decrease. The results also demonstrate that by application of a proper overlap ratio, power coefficient of the rotor would increase by nearly 22 percent.
Effect of Erodent Particle Initial Velocity on the Erosion of Propeller Blades for Turboprop Engines
Authors: Farghaly Mohamed B. , El-Sayed Ahmed F. , Salem Galal B.
Published: October 2013

Propeller driven-engines operate efficiently at low speeds, and ground maneuvers, but its performance is affected by operating in unsuitable environment. Actually, it is susceptible to encounter many physical problems such as erosion, corrosion, foreign object damage, and icing. These problems not only cause changes in air path boundaries but also yield changes in the aerodynamic performance of the engine components due to the change of the propeller profile shape and increase in the overall surface roughness.

This work aims to study the effect of the particle initial velocity on the propeller erosion phenomena and the subsequent deterioration for the blades profile. Particle trajectory, erosion rate, frequency and the critical erosion area on the blade are the main issues under investigation.

The domain selected for computational study is a periodic sector through the propeller bounding and the boundary conditions are set corresponding to that exist in the propeller manuals. A three dimensional unstructured grid was generated and adopted using commercial turbomachinery grid generator GAMBIT software. The governing equations are solved using FLUENT6.3.26 a commercial CFD code, which uses a control volume approach on a grid over the computational domain. A Lagrangian-formulated particle equation of motion is added to predict particle velocity and trajectories once the air flow field is obtained.
Interplay effects between dose distribution quality and positioning accuracy in total marrow irradiation with volumetric modulated arc therapy
Authors: Mancosu Pietro , Navarria Piera , Castagna Luca , Reggiori Giacomo , Sarina Barbara , Tomatis Stefano , Alongi Filippo , Nicolini Giorgia , Fogliata Antonella , Cozzi Luca , Scorsetti Marta
Published: October 2013

Purpose:

To evaluate the dosimetric consequences of inaccurate isocenter positioning during treatment of total marrow (lymph‐node) irradiation (TMI‐TMLI) using volumetric modulated arc therapy (VMAT).

Methods:

Four patients treated with TMI and TMLI were randomly selected from the internal database. Plans were optimized with VMAT technique. Planning target volume (PTV) included all the body bones; for TMLI, lymph nodes and spleen were considered into the target, too. Dose prescription to PTV was 12 Gy in six fractions, two times per day for TMI, and 2 Gy in single fraction for TMLI. Ten arcs on five isocenters (two arcs for isocenter) were used to cover the upper part of PTV (i.e., from cranium to middle femurs). For each plan, three series of random shifts with values between −3 and +3 mm and three between −5 and +5 mm were applied to the five isocenters simulating involuntary patient motion during treatment. The shifts were applied separately in the three directions: left–right (L‐R), anterior–posterior (A‐P), and cranial–caudal (C‐C). The worst case scenario with simultaneous random shifts in all directions simultaneously was considered too. Doses were recalculated for the 96 shifted plans (24 for each patient).

Results:

For all shifts, differences <0.5% were found for mean doses to PTV, body, and organs at risk with volumes >100 cm3. Maximum doses increased up to 15% for C‐C shifted plans. PTV covered by the 95% isodose decreased of 2%–8% revealing target underdosage with the highest values in C‐C direction.

Conclusions:

The correct isocenter repositioning of TMI‐TMLI patients is fundamental, in particular in C‐C direction, in order to avoid over‐ and underdosages especially in the overlap regions. For this reason, a dedicated immobilization system was developed in the authorsˈ center to best immobilize the patient.
Urinary bladder segmentation in CT urography (CTU) using CLASS
Authors: Hadjiiski Lubomir , Chan Heang‐Ping , Cohan Richard H. , Caoili Elaine M. , Law Yuen , Cha Kenny , Zhou Chuan , Wei Jun
Published: October 2013

Purpose:

The authors are developing a computerized system for bladder segmentation on CTU, as a critical component for computer aided diagnosis of bladder cancer.

Methods:

A challenge for bladder segmentation is the presence of regions without contrast (NC) and filled with intravenous contrast (C). The authors have designed a Conjoint Level set Analysis and Segmentation System (CLASS) specifically for this application. CLASS performs a series of image processing tasks: preprocessing, initial segmentation, 3D and 2D level set segmentation, and postprocessing, designed according to the characteristics of the bladder in CTU. The NC and the C regions of the bladder were segmented separately in CLASS. The final contour is obtained in the postprocessing stage by the union of the NC and C contours. With Institutional Review Board (IRB) approval, the authors retrospectively collected 81 CTU scans, in which 40 bladders contained lesions, 26 contained diffuse wall thickening, and 15 were considered to be normal. The bladders were segmented by CLASS and the performance was assessed by rating the quality of the contours on a 10‐point scale (1 = “very poor,” 5 = “fair,” 10 = “perfect”). For 30 bladders, 3D hand‐segmented contours were obtained and the segmentation accuracy of CLASS was evaluated and compared to that of a single level set method in terms of the average minimum distance, average volume intersection ratio, average volume error and Jaccard index.

Results:

Of the 81 bladders, the average quality rating for CLASS was 6.5 ± 1.3. Thirty nine bladders were given quality ratings of 7 or above. Only five bladders had ratings under 5. The average minimum distance, average volume intersection ratio, average volume error, and average Jaccard index for CLASS were 3.5 ± 1.3 mm, (79.0 ± 8.2)%, (16.1 ± 16.3)%, and (75.7 ± 8.4)%, respectively, and for the single level set method were 5.2 ± 2.6 mm, (78.8 ± 16.3)%, (8.3 ± 33.1)%, (71.0 ± 15.4)%, respectively.

Conclusions:

The results demonstrate the potential of CLASS for segmentation of the bladder.
Development and validation of a measurement‐based source model for kilovoltage cone‐beam CT Monte Carlo dosimetry simulations
Authors: McMillan Kyle , McNitt‐Gray Michael , Ruan Dan
Published: October 2013

Purpose:

The purpose of this study is to adapt an equivalent source model originally developed for conventional CT Monte Carlo dose quantification to the radiation oncology context and validate its application for evaluating concomitant dose incurred by a kilovoltage (kV) cone‐beam CT (CBCT) system integrated into a linear accelerator.

Methods:

In order to properly characterize beams from the integrated kV CBCT system, the authors have adapted a previously developed equivalent source model consisting of an equivalent spectrum module that takes into account intrinsic filtration and an equivalent filter module characterizing the added bowtie filtration. An equivalent spectrum was generated for an 80, 100, and 125 kVp beam with beam energy characterized by half‐value layer measurements. An equivalent filter description was generated from bowtie profile measurements for both the full‐ and half‐bowtie. Equivalent source models for each combination of equivalent spectrum and filter were incorporated into the Monte Carlo software package MCNPX. Monte Carlo simulations were then validated against in‐phantom measurements for both the radiographic and CBCT mode of operation of the kV CBCT system. Radiographic and CBCT imaging dose was measured for a variety of protocols at various locations within a body (32 cm in diameter) and head (16 cm in diameter) CTDI phantom. The in‐phantom radiographic and CBCT dose was simulated at all measurement locations and converted to absolute dose using normalization factors calculated from air scan measurements and corresponding simulations. The simulated results were compared with the physical measurements and their discrepancies were assessed quantitatively.

Results:

Strong agreement was observed between in‐phantom simulations and measurements. For the radiographic protocols, simulations uniformly underestimated measurements by 0.54%–5.14% (mean difference = −3.07%, SD = 1.60%). For the CBCT protocols, simulations uniformly underestimated measurements by 1.35%–5.31% (mean difference = −3.42%, SD = 1.09%).

Conclusions:

This work demonstrates the feasibility of using a measurement‐based kV CBCT source model to facilitate dose calculations with Monte Carlo methods for both the radiographic and CBCT mode of operation. While this initial work validates simulations against measurements for simple geometries, future work will involve utilizing the source model to investigate kV CBCT dosimetry with more complex anthropomorphic phantoms and patient specific models.
A new concept of pencil beam dose calculation for 40–200 keV photons using analytical dose kernels
Authors: Bartzsch Stefan , Oelfke Uwe
Published: October 2013

Purpose:

The advent of widespread kV‐cone beam computer tomography in image guided radiation therapy and special therapeutic application of keV photons, e.g., in microbeam radiation therapy (MRT) require accurate and fast dose calculations for photon beams with energies between 40 and 200 keV. Multiple photon scattering originating from Compton scattering and the strong dependence of the photoelectric cross section on the atomic number of the interacting tissue render these dose calculations by far more challenging than the ones established for corresponding MeV beams. That is why so far developed analytical models of kV photon dose calculations fail to provide the required accuracy and one has to rely on time consuming Monte Carlo simulation techniques.

Methods:

In this paper, the authors introduce a novel analytical approach for kV photon dose calculations with an accuracy that is almost comparable to the one of Monte Carlo simulations. First, analytical point dose and pencil beam kernels are derived for homogeneous media and compared to Monte Carlo simulations performed with the Geant4 toolkit. The dose contributions are systematically separated into contributions from the relevant orders of multiple photon scattering. Moreover, approximate scaling laws for the extension of the algorithm to inhomogeneous media are derived.

Results:

The comparison of the analytically derived dose kernels in water showed an excellent agreement with the Monte Carlo method. Calculated values deviate less than 5% from Monte Carlo derived dose values, for doses above 1% of the maximum dose. The analytical structure of the kernels allows adaption to arbitrary materials and photon spectra in the given energy range of 40–200 keV.

Conclusions:

The presented analytical methods can be employed in a fast treatment planning system for MRT. In convolution based algorithms dose calculation times can be reduced to a few minutes.
Reduced efficiency of audiovisual integration for nonnative speech
Authors: Yi Han-Gyol , Phelps Jasmine E. B. , Smiljanic Rajka , Chandrasekaran Bharath
Published: October 2013

The role of visual cues in native listeners' perception of speech produced by nonnative speakers has not been extensively studied. Native perception of English sentences produced by native English and Korean speakers in audio-only and audiovisual conditions was examined. Korean speakers were rated as more accented in audiovisual than in the audio-only condition. Visual cues enhanced word intelligibility for native English speech but less so for Korean-accented speech. Reduced intelligibility of Korean-accented audiovisual speech was associated with implicit visual biases, suggesting that listener-related factors partially influence the efficiency of audiovisual integration for nonnative speech perception.
Abrupt Shifts in Horn of Africa Hydroclimate Since the Last Glacial Maximum
Authors: Tierney Jessica E. , deMenocal Peter B.
Published: October 2013

Quick-Dry Region

The Sahara Desert is one of the driest places on Earth. However, 11,000 to 5000 years ago, it was a relatively lush region containing savannah grasslands and humid tropical forests. This interval, the Early Holocene African Humid Period, ended, of course, but whether the drying occurred rapidly or gradually is unclear.
Tierney and deMenocal
(p.
843
, published online 10 October; see the Perspective by

Bard

) report results from the Horn of Africa that suggest that the transitions both into and out of the humid period were abrupt—occurring within centuries rather than over millennia.
Genome Sequence of
Halomonas
sp. Strain A3H3, Isolated from Arsenic-Rich Marine Sediments
Authors: Koechler Sandrine , Plewniak Frédéric , Barbe Valérie , Battaglia-Brunet Fabienne , Jost Bernard , Joulian Catherine , Philipps Muriel , Vicaire Serge , Vincent Stéphanie , Ye Tao , Bertin Philippe N.
Published: October 2013

We report the genome sequence of
Halomonas
sp. strain A3H3, a bacterium with a high tolerance to arsenite, isolated from multicontaminated sediments of the l'Estaque harbor in Marseille, France. The genome is composed of a 5,489,893-bp chromosome and a 157,085-bp plasmid.
Draft Genome Sequence of a Meningitic Isolate of Cronobacter sakazakii Clonal Complex 4, Strain 8399
Authors: Masood Naqash , Moore Karen , Farbos Audrey , Hariri Sumyya , Block Colin , Paszkiewicz Konrad , Dickins Ben , McNally Alan , Forsythe Stephen
Published: October 2013

The
Cronobacter sakazakii
clonal lineage defined as clonal complex 4 (CC4), composed of nine sequence types, is associated with severe cases of neonatal meningitis. To date, only closely related
C. sakazakii
sequence type 4 (ST4) strains have been sequenced.
C. sakazakii
strain 8399, isolated from a case of neonatal meningitis, was sequenced as the first non-ST4
C. sakazakii
strain.
Draft Genome Sequence of
Bacillus
sp. Strain NSP9.1, a Moderately Halophilic Bacterium Isolated from the Salt Marsh of the Great Rann of Kutch, India
Authors: Dey Rinku , Pal Kamal Krishna , Sherathia Dharmesh , Dalsania Trupti , Savsani Kinjal , Patel Ilaxi , Thomas Manesh , Ghorai Sucheta , Vanpariya Sejal , Rupapara Rupal , Rawal Priya , Sukhadiya Bhoomika , Mandaliya Mona , Saxena Anil Kumar
Published: October 2013

We report the 4.52-Mbp draft genome sequence of
Bacillus
sp. strain NSP9.1, a moderately halophilic bacterium isolated from the salt marsh of the Great Rann of Kutch, India. Analysis of the genome of this organism will lead to a better understanding of the genes and metabolic pathways involved in imparting osmotolerance.
Cotyledonoid dissecting leiomyoma as a possible cause of chronic lower back pain
Authors: Onu David O , Fiorentino Lisa M , Bunting Michael W
Published: October 2013

Uterine fibroids having the distinct pathological and immunohistochemical features of cotyledonoid dissecting leiomyoma have been reported infrequently. We describe a postmenopausal woman with an incidental finding of an abdominopelvic mass arising from the uterine fundus on routine radiological imaging of the lumbar spine. The imaging was performed for the investigation of chronic radicular lower back pain refractory to usual pain management. However, the woman did not manifest any gynaecological symptoms. Intraoperatively, the pelvic mass appeared malignant and a frozen section suggested uterine sarcoma. As such, the mass was radically resected, resulting in significant resolution of the back pain. To the authors’ knowledge, this is the first report of cotyledonoid dissecting leiomyoma presenting solely as chronic lower back pain, and also the first report of this fibroid variant in Australasia. We discuss the diagnostic and operative challenges, emphasising the role of radiological imaging and immunohistopathology in such cases and review current literature.
Vanishing corneal vessels
Authors: Nicholson Luke , Chana Rupinder
Published: October 2013

We wish to highlight the importance of acknowledging the accompanying effects of topical phenylephrine drops on the eye other than its intended mydriasis. We reported a case of a 92-year-old woman with a corneal graft who was noted to have superficial corneal vascularisation which was not documented previously. After the instillation of topical tropicamide 1% and phenylephrine 2.5%, for funduscopy, the corneal vascularisation was not visible. When reassessed on another visit, tropicamide had no effect on the vessels and only phenylephrine did. We wish to highlight that when reviewing patients in cornea clinics, instilling phenylephrine prior to being seen may mask important corneal vascularisation.
A retrospective study of pyometra at five RSPCA hospitals in the UK: 1728 cases from 2006 to 2011
Authors: Gibson A. , Dean R. , Yates D. , Stavisky J.
Published: October 2013

A retrospective cross‐sectional study was used to analyse pyometra cases at five RSPCA Animal Hospitals across the UK from 2006 to 2011. A total of 1728 cases of pyometra were recovered from a female dog outpatient caseload of 78,469 animals, giving a total prevalence of 2.2 per cent over the study period. There was an annual increase in the incidence of pyometra within the population, while elective ovariohysterectomy caseload has declined. There were variations in breed and age at presentation. Bullmastiffs (P<0.0001), golden retrievers (P=0.001) and dogue de Bordeaux (P=0.008) were over‐represented in the pyometra population when compared with the female dog outpatient caseload. Mean age at presentation was 7.7 years. Some breeds presented at a significantly lower age, including dogue de Bordeaux (mean age 3.3 years) and bullmastiffs (mean age 5.4 years), while others presented as older dogs, including Yorkshire terriers (mean age 9.4 years) and border collies (mean age 10.3 years). Surgical mortality rate at the Greater Manchester Animal Hospital was 3.2 per cent. Pyometra is of significant welfare concern, and also has cost implications, particularly in charity practice. These results serve to highlight this condition so that future change in charity practice caseload can be anticipated and strategies can be directed to improve animal welfare.
ALGORITHMS FOR OBTAINING A SADDLE TORUS BETWEEN TWO ATTRACTORS
Authors: KAMIYAMA KYOHEI , KOMURO MOTOMASA , ENDO TETSURO
Published: October 2013

We develop two algorithms for obtaining an index 1 saddle torus between two attractors of which basin boundary is smooth by using the bisection method. In the first algorithm, which we name "overall template method", we make a template approximating a whole attractor and use it for pattern matching. The attractor can be a periodic orbit, a torus and even a chaos. In the second algorithm, which we name "partial template method", we make a template approximating only a part of an attractor. In this algorithm, the attractor is restricted to a periodic orbit and a two-torus, but calculation time is much smaller than that of the overall template method. We demonstrate these two algorithms for two solutions, observed in a ring of six-coupled bistable oscillators. One is a saddle torus in the basin boundary of the two switching solutions, and the other is of the two quasi-periodic propagating wave solutions. We calculate the Lyapunov spectrum of the obtained saddle torus, and confirm one positive Lyapunov exponent.
UNIVERSAL FORM OF RENORMALIZABLE KNOTS IN SYMBOLIC DYNAMICS OF BIMODAL MAPS
Authors: GAO WEN , XU CHUAN-YUN , PENG SHOU-LI , CAO KE-FEI
Published: October 2013

A general relation between knot theory and symbolic dynamics is studied for bimodal maps in this paper. When symbolic sequences of maps are expressed as knots, it is easy to see that the knot of a renormalizable sequence is composed of a bunch of periodic flows. In this setting, the generation of renormalizable knots can be simply operated in geometry and explicitly calculated in algebra. In this paper we provide a universal form of renormalizable knots, which can be decomposed into a sequence of elementary templates; especially, it is independent of the traditional *-products of symbolic dynamics. We present some examples and list the elementary templates of period not bigger than 6.
Tropical Marginal Seas: Priority Regions for Managing Marine Biodiversity and Ecosystem Function
Authors: McKinnon A. David , Williams Alan , Young Jock , Ceccarelli Daniela , Dunstan Piers , Brewin Robert J.W. , Watson Reg , Brinkman Richard , Cappo Mike , Duggan Samantha , Kelley Russell , Ridgway Ken , Lindsay Dhugal , Gledhill Daniel , Hutton Trevor , Richardson Anthony J.
Published: October 2013

Tropical marginal seas (TMSs) are natural subregions of tropical oceans containing biodiverse ecosystems with conspicuous, valued, and vulnerable biodiversity assets. They are focal points for global marine conservation because they occur in regions where human populations are rapidly expanding. Our review of 11 TMSs focuses on three key ecosystems—coral reefs and emergent atolls, deep benthic systems, and pelagic biomes—and synthesizes, illustrates, and contrasts knowledge of biodiversity, ecosystem function, interaction between adjacent habitats, and anthropogenic pressures. TMSs vary in the extent that they have been subject to human influence—from the nearly pristine Coral Sea to the heavily exploited South China and Caribbean Seas—but we predict that they will all be similarly complex to manage because most span multiple national jurisdictions. We conclude that developing a structured process to identify ecologically and biologically significant areas that uses a set of globally agreed criteria is a tractable first step toward effective multinational and transboundary ecosystem management of TMSs.
Nutritional and Functional Assessment of Hospitalized Elderly: Impact of Sociodemographic Variables
Authors: Esmayel Emam M. M. , Eldarawy Mohsen M. , Hassan Mohamed M. M. , Hassanin Hassan Mahmoud , Reda Ashour Walid M. , Mahmoud Wael
Published: October 2013

Background.This work was constructed in order to assess the nutritional and functional status in hospitalized elderly and to study the associations between them and sociodemographic variables.Methods.200 elderly patients (>65 years old) admitted to Internal Medicine and Neurology Departments in nonemergency conditions were included. Comprehensive geriatric assessments, including nutritional and functional assessments, were done according to nutritional checklist and Barthel index, respectively. Information was gathered from the patients, from the ward nurse responsible for the patient, and from family members who were reviewed.Results.According to the nutritional checklist, 56% of participants were at high risk, 18% were at moderate risk of malnutrition, and 26% had good nutrition. There was a high nutritional risk in patients with low income and good nutrition in patients with moderate income. Also, there was a high nutritional risk in rural residents (61.9%) in comparison with urban residents (25%). Barthel index score was significantly lower in those at high risk of malnutrition compared to those at moderate risk and those with good nutrition.Conclusions.Hospitalized elderly are exposed to malnutrition, and malnourished hospitalized patients are candidates for functional impairment. Significant associations are noticed between both nutritional and functional status and specific sociodemographic variables.
Secure Actor Directed Localization in Wireless Sensor and Actor Networks
Authors: Ali Tamleek , Khan Muazzam A. , Hayat Amir , Alam Masoom , Ali Muhammad
Published: October 2013

Wireless sensor and actor networks are fully automated. Actor nodes are inducted to communicate with sensor nodes directly and reduce the communication delay caused by base station or sink nodes. Sometimes, the actor node is directly accessible without the involvement of any control room. The actor node is responsible for taking a prompt action against the reported event by a sensor node. For secure communication, it is essential that sensor and actor nodes be aware of their existing location and the data must be encrypted before transmission. Due to energy constraints, secure localization in wireless sensor networks is a hot issue. To date, the researchers have proposed many approaches for localization of sensor nodes in the network. In this paper, we provide new insights for secure actor directed localization technique in wireless sensor and actor networks. A secure connectivity based localization (CBL) approach for sensor and actor nodes localization is presented. The proposed approach helps to locate a sensor node efficiently and effectively. We have also decreased the possibility of attacks and the registration of attacker nodes with other legitimate nodes in the network. The proposed technique prevents man-in-the-middle attacks and securely delivers data to the destination.