bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared Imaging and Spatiotemporal Radiation Properties of a Turbulent Nonpremixed Jet Flame and Plume
Authors: Rankin Brent A. , Blunck David L. , Gore Jay P.
Published: December 2012

Radiation transfer from turbulent nonpremixed jet flames and plumes is important in many applications such as energy-efficient combustion systems, temperature sensitive pollutant control, and detection, control, and suppression of accidental fires. Combined spatial and temporal correlations of scalar values such as temperature and species concentrations affect the emitted radiation intensity. Spatiotemporal correlations and radiation intensity measurements downstream of the reacting parts of flames (plumes) have received limited attention. Motivated by this, planar time-dependent narrowband radiation intensity measurements are acquired of a turbulent nonpremixed flame and its plume using an infrared camera. Temporally and spatially correlated instantaneous realizations of local scalars and path integrated intensity values are calculated using a stochastic time and space series analysis, a narrowband radiation model, and the radiative transfer equation. The time-dependent infrared images reveal intermittent, low intensity regions in the plume characteristic of buoyancy-dominated transport. High radiation intensity structures are observed in the flame characteristic of momentum dominated flow and vorticity driven mixing. Normalized intensity fluctuations are nearly constant in the flame region, but increase by up to a factor of three in the plume. Normalized temporal correlations, power spectral density functions, and spatial correlations of the intensity are independent of the spatial location throughout both the flame and the plume. Spatial correlations of the radiation intensity exhibit approximately linear decay to half an integral length scale followed by an exponential decrement. The radiation intensity fluctuations remain spatially correlated up to separation distances two times larger than the integral length scale. Space–time cross correlations of the intensity fluctuations are measured for the first time and are shown to be more isotropic in comparison to the product of the spatial and temporal correlations. This suggests that a correction factor should be applied to the space–time correlation model in future stochastic calculations to account for the anisotropy. The infrared imaging technique, illustrated in this paper, is promising to be a useful qualitative and quantitative nonintrusive technique for studying both reacting and nonreacting flows.
Experimental Characterization of Capillary-Fed Carbon Nanotube Vapor Chamber Wicks
Authors: Weibel Justin A. , Kim Sungwon S. , Fisher Timothy S. , Garimella Suresh V.
Published: December 2012

The thermal performance of passive vapor chamber heat spreaders can be improved by enhancing evaporation from the internal wick structure. A wick structure that integrates conventional copper screen mesh and carbon nanotubes (CNTs) is developed and characterized for increased heat transport capability and reduced thermal resistance. The high-permeability mesh provides for a low-resistance liquid flow path while the carbon nanotubes, with their high thermal conductivity and large surface area, help reduce conduction and phase-change resistances. The wicks are fabricated by sintering a copper mesh on a multilayer substrate consisting of copper and molybdenum. CNTs are grown on to this mesh and a submicron layer of copper is evaporated on to the CNTs to improve wettability with water and wicking. Samples grown under varying degrees of positive bias voltage and varying thicknesses of post-CNT-growth copper evaporation are fabricated to investigate the effect of surface morphology variations. The resultant boiling curves indicate that micro/nano-integrated wicks fabricated with higher positive bias voltages during CNT synthesis coupled with thicker copper coatings produce lower wick thermal resistances. Notably, heat fluxes at the heater surface of greater than 500 W/cm2 were supported without a critical heat flux condition being reached.
A Thermohydrodynamic Analysis of Dry Gas Seals for High-Temperature Gas-Cooled Reactor
Authors: Hong Wang , Baoshan Zhu , Jianshu Lin , Changliu Ye
Published: December 2012

A comprehensive analysis method is proposed to resolve the problem of simulating the complex thermoflow with two kinds of distinct characteristic lengths in a dry gas seal. A conjugated simulation of the complicated heat transfer and the gas film flow is carried out by using the commercial computational fluid dynamics (CFD) software CFX. By using the proposed method, three-dimensional velocity and pressure fields in the gas film flow and the temperature distribution within the sealing rings are investigated for three kinds of film thickness, respectively. A comparison of thermohydrodynamic characteristics of the dry gas seal is conducted between the sealed gas of air and helium. The latter one is used in a helium compressor for a high-temperature gas-cooled reactor (HTGR). From comparisons and discussions of a series of simulation results, it will be found that the comprehensive proposal is effective and simulation results are reasonable. Even under a hypothetical accidental condition, the maximum temperature rise in the dry gas seal is within the acceptable range of HTGR safety requirements.
Dynamic Behaviors of the Elastohydrodynamic Lubricated Contact for Rolling Bearings
Authors: Zhang Yu-Yan , Wang Xiao-Li , Yan Xiao-Liang
Published: December 2012

The dynamic behaviors of a single elastohydrodynamic lubricated (EHL) contact between a rolling element and raceways under wider load and speed ranges are analyzed numerically based on the transient EHL model and the free vibration model. The discrete convolution and fast fourier transform method is implemented in order to increase the computational efficiency associated with elastic deformations and the semisystem approach is applied to improve the solution convergence under severe conditions. The change of mutual approach is selected as the standard of bearing vibrations and the inlet length and dimensionless natural frequency corresponding to the working load and speed are determined. The numerical results demonstrate that the stiffness increases with the increasing load and decreases with speed. However, the changes of damping are different in various working conditions, especially under heavier load and higher speed. It is also indicated that the stiffness and damping increase with the increase in ambient viscosity and the decrease in pressure-viscosity coefficient.
Study of the Influence of Heat Convection Coefficient on Predicted Performance of a Large Tilting-Pad Thrust Bearing
Authors: Wodtke M. , Fillon M. , Schubert A. , Wasilczuk M.
Published: December 2012

Part of the heat generated by the shearing of the lubricating film during operation of a hydrodynamic bearing is transferred to the bearing components. In the case of the pad, which is usually fully submerged in the lubricating oil, heat is further transferred at the pad free walls to the oil by convection. This mechanism causes a thermal gradient in a pad and, consequently, its thermal deflection. In large hydrodynamic thrust bearings, thermal deflection of the pads is an important phenomenon influencing bearing performance. For such bearings, pad distortion can reach the level of hydrodynamic film thickness and can significantly change the bearing's properties. In this paper, the study of the influence of the heat convection coefficient on the predicted performance of a large hydrodynamic thrust bearing is presented. Two sets of convection coefficients at the pad free surfaces are investigated with the use of thermo-elasto-hydrodynamic (TEHD) calculations. An analysis is carried out for the Itaipu hydro turbine thrust bearing with the outer diameter equal to 5.2 m, which is one of the biggest hydro power plants in the world. The results of the theoretical predictions are compared to the measured data collected during bearing operation.
Effect of Age and Proteoglycan Deficiency on Collagen Fiber Re-Alignment and Mechanical Properties in Mouse Supraspinatus Tendon
Authors: Connizzo Brianne K. , Sarver Joseph J. , Iozzo Renato V. , Birk David E. , Soslowsky Louis J.
Published: December 2012

Collagen fiber realignment is one mechanism by which tendon responds to load. Re-alignment is altered when the structure of tendon is altered, such as in the natural process of aging or with alterations of matrix proteins, such as proteoglycan expression. While changes in re-alignment and mechanical properties have been investigated recently during development, they have not been studied in (1) aged tendons, or (2) in the absence of key proteoglycans. Collagen fiber re-alignment and the corresponding mechanical properties are quantified throughout tensile mechanical testing in both the insertion site and the midsubstance of mouse supraspinatus tendons in wild type (WT), decorin-null (Dcn-/-), and biglycan-null (Bgn-/-) mice at three different ages (90 days, 300 days, and 570 days). Percent relaxation was significantly decreased with age in the WT and Dcn-/- tendons, but not in the Bgn-/- tendons. Changes with age were found in the linear modulus at the insertion site where the 300 day group was greater than the 90 day and 570 day group in the Bgn-/- tendons and the 90 day group was smaller than the 300 day and 570 day groups in the Dcn-/- tendons. However, no changes in modulus were found across age in WT tendons were found. The midsubstance fibers of the WT and Bgn-/- tendons were initially less aligned with increasing age. The re-alignment was significantly altered with age in the WT tendons, with older groups responding to load later in the mechanical test. This was also seen in the Dcn-/- midsubstance and the Bgn-/- insertion, but not in the other locations. Although some studies have found changes in the WT mechanical properties with age, this study did not support those findings. However, it did show fiber re-alignment changes at both locations with age, suggesting a breakdown of tendon's ability to respond to load in later ages. In the proteoglycan-null tendons however, there were changes in the mechanical properties, accompanied only by location-dependent re-alignment changes, suggesting a site-specific role for these molecules in loading. Finally, changes in the mechanical properties did not occur in concert with changes in re-alignment, suggesting that typical mechanical property measurements alone are insufficient to describe how structural alterations affect tendon's response to load.
In Vitro Evaluation of a Novel Hemodynamically Optimized Trileaflet Polymeric Prosthetic Heart Valve
Authors: Claiborne Thomas E. , Sheriff Jawaad , Kuetting Maximilian , Steinseifer Ulrich , Slepian Marvin J. , Bluestein Danny
Published: December 2012

Calcific aortic valve disease is the most common and life threatening form of valvular heart disease, characterized by stenosis and regurgitation, which is currently treated at the symptomatic end-stages via open-heart surgical replacement of the diseased valve with, typically, either a xenograft tissue valve or a pyrolytic carbon mechanical heart valve. These options offer the clinician a choice between structural valve deterioration and chronic anticoagulant therapy, respectively, effectively replacing one disease with another. Polymeric prosthetic heart valves (PHV) offer the promise of reducing or eliminating these complications, and they may be better suited for the new transcatheter aortic valve replacement (TAVR) procedure, which currently utilizes tissue valves. New evidence indicates that the latter may incur damage during implantation. Polymer PHVs may also be incorporated into pulsatile circulatory support devices such as total artificial heart and ventricular assist devices that currently employ mechanical PHVs. Development of polymer PHVs, however, has been slow due to the lack of sufficiently durable and biocompatible polymers. We have designed a new trileaflet polymer PHV for surgical implantation employing a novel polymer—xSIBS—that offers superior bio-stability and durability. The design of this polymer PHV was optimized for reduced stresses, improved hemodynamic performance, and reduced thrombogenicity using our device thrombogenicity emulation (DTE) methodology, the results of which have been published separately. Here we present our new design, prototype fabrication methods, hydrodynamics performance testing, and platelet activation measurements performed in the optimized valve prototype and compare it to the performance of a gold standard tissue valve. The hydrodynamic performance of the two valves was comparable in all measures, with a certain advantage to our valve during regurgitation. There was no significant difference between the platelet activation rates of our polymer valve and the tissue valve, indicating that similar to the latter, its recipients may not require anticoagulation. This work proves the feasibility of our optimized polymer PHV design and brings polymeric valves closer to clinical viability.
Computational Analysis of Non-Spherical Particle Transport and Deposition in Shear Flow With Application to Lung Aerosol Dynamics—A Review
Authors: Kleinstreuer Clement , Feng Yu
Published: December 2012

All naturally occurring and most man-made solid particles are nonspherical. Examples include air-pollutants in the nano- to micro-meter range as well as blood constituents, drug particles, and industrial fluid-particle streams. Focusing on the modeling and simulation of inhaled aerosols, theories for both spherical and nonspherical particles are reviewed to analyze the contrasting transport and deposition phenomena of spheres and equivalent spheres versus ellipsoids and fibers.
Mechanics of Healthy and Functionally Diseased Mitral Valves: A Critical Review
Authors: Rabbah Jean-Pierre M. , Saikrishnan Neelakantan , Siefert Andrew W. , Santhanakrishnan Arvind , Yoganathan Ajit P.
Published: December 2012

The mitral valve is a complex apparatus with multiple constituents that work cohesively to ensure unidirectional flow between the left atrium and ventricle. Disruption to any or all of the components—the annulus, leaflets, chordae, and papillary muscles—can lead to backflow of blood, or regurgitation, into the left atrium, which deleteriously effects patient health. Through the years, a myriad of surgical repairs have been proposed; however, a careful appreciation for the underlying structural mechanics can help optimize long-term repair durability and inform medical device design. In this review, we aim to present the experimental methods and significant results that have shaped the current understanding of mitral valve mechanics. Data will be presented for all components of the mitral valve apparatus in control, pathological, and repaired conditions from human, animal, and in vitro studies. Finally, current strategies of patient specific and noninvasive surgical planning will be critically outlined.
Review: The Role of Biomechanical Modeling in the Rupture Risk Assessment for Abdominal Aortic Aneurysms
Authors: Martufi Giampaolo , Christian Gasser T.
Published: December 2012

AAA disease is a serious condition and a multidisciplinary approach including biomechanics is needed to better understand and more effectively treat this disease. A rupture risk assessment is central to the management of AAA patients, and biomechanical simulation is a powerful tool to assist clinical decisions. Central to such a simulation approach is a need for robust and physiologically relevant models. Vascular tissue senses and responds actively to changes in its mechanical environment, a crucial tissue property that might also improve the biomechanical AAA rupture risk assessment. Specifically, constitutive modeling should not only focus on the (passive) interaction of structural components within the vascular wall, but also how cells dynamically maintain such a structure. In this article, after specifying the objectives of an AAA rupture risk assessment, the histology and mechanical properties of AAA tissue, with emphasis on the wall, are reviewed. Then a histomechanical constitutive description of the AAA wall is introduced that specifically accounts for collagen turnover. A test case simulation clearly emphasizes the need for constitutive descriptions that remodels with respect to the mechanical loading state. Finally, remarks regarding modeling of realistic clinical problems and possible future trends conclude the article.
Update on Grand Challenge Competition to Predict in Vivo Knee Loads
Authors: Kinney Allison L. , Besier Thor F. , D'Lima Darryl D. , Fregly Benjamin J.
Published: December 2012

Validation is critical if clinicians are to use musculoskeletal models to optimize treatment of individual patients with a variety of musculoskeletal disorders. This paper provides an update on the annual Grand Challenge Competition to Predict in Vivo Knee Loads, a unique opportunity for direct validation of knee contact forces and indirect validation of knee muscle forces predicted by musculoskeletal models. Three competitions (2010, 2011, and 2012) have been held at the annual American Society of Mechanical Engineers Summer Bioengineering Conference, and two more competitions are planned for the 2013 and 2014 conferences. Each year of the competition, a comprehensive data set collected from a single subject implanted with a force-measuring knee replacement is released. Competitors predict medial and lateral knee contact forces for two gait trials without knowledge of the experimental knee contact force measurements. Predictions are evaluated by calculating root-mean-square (RMS) errors and R2 values relative to the experimentally measured medial and lateral contact forces. For the first three years of the competition, competitors used a variety of methods to predict knee contact and muscle forces, including static and dynamic optimization, EMG-driven models, and parametric numerical models. Overall, errors in predicted contact forces were comparable across years, with average RMS errors for the four competition winners ranging from 229 N to 312 N for medial contact force and from 238 N to 326 N for lateral contact force. Competitors generally predicted variations in medial contact force (highest R2 = 0.91) better than variations in lateral contact force (highest R2 = 0.70). Thus, significant room for improvement exists in the remaining two competitions. The entire musculoskeletal modeling community is encouraged to use the competition data and models for their own model validation efforts.
Plasma-assisted cleaning by metastable-atom neutralization
Authors: Lytle Wayne M. , Andruczyk Daniel , Ruzic David N.
Published: December 2012

Plasma-assisted cleaning by metastable atomic neutralization (PACMAN) is a process that can clean hydrocarbon from extreme ultraviolet photo masks and dissolve hydrocarbon particles. It was developed with semiconductor manufacturing and cleaning in mind. The PACMAN process works by utilizing helium metastable atoms to break apart the contamination to be cleaned. As helium metastables interact with the contaminant surface, bonding electrons from the surface are “stolen” by the metastable helium resulting in “holes” where a bonding electron used to be. In this way, the structure of the contamination is compromised and allows for the removal either through desorption of CxHy molecules or by chain scission of the hydrocarbon backbone. A model of the helium metastable density within the processing chamber has been developed in addition to experimental measurements of the metastable density at the sample surface. Cleaning efficiency has been linked to both helium metastable density as well as electric field in the plasma sheath. Electric field calculations in the plasma sheath reveal that an electric field pointing into the plasma is needed for achieving high cleaning rates of hydrocarbons since it pins the holes that are created to the surface and stops the hydrocarbon bonds from re-forming. Operating the PACMAN process in this fashion allows for cleaning rates of approximately 1.2 × 107 ± 5.1 × 105 nm3/min from a particle without causing damage to the surrounding structure of the sample being cleaned. Carbon contamination in the form of carbon films on lithographic material has been shown to clean at rates of approximately 11.4 ± 0.3 nm/min.
Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications
Authors: Huang Yujian , Pandraud Gregory , Sarro Pasqualina M.
Published: December 2012

TiO2 is an interesting and promising material for micro-/nanoelectromechanical systems (MEMS/NEMS). For high performance and reliable MEMS/NEMS, optimization of the optical characteristics, mechanical stress, and especially surface smoothness of TiO2 is required. To overcome the roughness issue of the TiO2 films due to crystallization during deposition at high temperatures (above 250 °C), low temperature (80–120 °C) atomic layer deposition (ALD) is investigated. By lowering the deposition temperature, the surface roughness significantly decreases from 3.64 nm for the 300 °C deposited crystalline (anatase phase) TiO2 to 0.24 nm for the 120 °C amorphous TiO2. However, the layers deposited at low temperature present different physical behaviors comparing to the high temperature ones. The refractive index drops from 2.499 to 2.304 (at 633 nm) and the stress sharply decreases from 684 to 133 MPa. Superhydrophilic surface is obtained for the high temperature deposited TiO2 under ultraviolet illumination, while little changes are found for the low temperature TiO2. The authors demonstrate that by suitable postdeposition annealing, all the properties of the low temperature deposited films recover to that of the 300 °C deposited TiO2, while the smooth surface profile (less than 1 nm roughness) is maintained. Finally, micromachining of the low temperature ALD TiO2 by dry etching is also studied.
Modeling of top and bottom contact structure organic field effect transistors
Authors: Kumar Brijesh , Kaushik Brajesh Kumar , Negi Yuvraj Singh
Published: December 2012

This research paper proposes analytical models for top and bottom contact organic field effect transistors by considering the overlapping of source-drain (S/D) contacts on to the organic semiconductor layer and effective channel between the contacts. The contact effect is investigated in the proposed models and further verified through two-dimensional (2-D) numerical device simulation. The electrical characteristics are obtained from the linear to saturation regime and analytical outcomes are compared with the simulation and experimental results, which shows good agreement and thus validate the models. The extracted mobilities for top and bottom contact structure include 0.129 and 0.0019 cm2/Vs, and the device resistance as 2.25 and 450MΩ and the contact resistance as 2.25 and 450 MΩ μm2, respectively. The performance difference between top and bottom contact is attributed to the structural difference and morphological disorders of pentacene film around the contacts in bottom contact device which results in higher contact resistance and lower mobility as compared to the top contact device.
Deep centers and persistent photocapacitance in AlGaN/GaN high electron mobility transistor structures grown on Si substrates
Authors: Polyakov Alexander Y. , Smirnov N. B. , Govorkov A. V. , Kozhukhova E. A. , Pearton Stephen J. , Ren Fan , Lui Lu , Johnson J. Wayne , Kargin N. I. , Ryzhuk R. V.
Published: December 2012

Deep trap spectra in AlGaN/GaN high electron mobility transistor structures grown on Si by metalorganic chemical vapor deposition show four major electron traps (Ec—0.15, 0.29, 0.40 and 0.76 eV) in the AlGaN barrier/interface region and three (Ec—0.18, 0.27 and 0.45 eV) in the undoped GaN buffer region. The presence of a high density of deep acceptor traps was observed in the AlGaN barrier region, as determined by hysteresis in low temperature capacitance-voltage (C-V) characteristics. The spectral dependence of persistent photocapacitance shifts showed two optical thresholds of 1.5 V and 3.1 eV, with the second being specific to structures grown on Si substrates. Comparison of results obtained on transistors and on large-area Schottky diodes prepared on heterostructures from which transistors are fabricated show that measurements on test large-area diodes are representative of the main characteristics important for transistor performance.
Stability and annealing of alucones and alucone alloys
Authors: Ghazaryan Lilit , Kley Ernst-Bernhard , Tünnermann Andreas , Viorica Szeghalmi Adriana
Published: December 2012

Hybrid organic–inorganic alucone films have been deposited using trimethylaluminum and ethylene glycol by molecular layer deposition (MLD). The stability of the coatings was monitored in ambient as well as in dry air. Alloys have also been deposited using alucone and Al2O3. The effect of thermal annealing as a function of the Al2O3 content was assessed. The stability and morphology of such organic–inorganic alloys are finely tuned by their composition. The alucones and alucone/Al2O3 alloys with the ratio of 5 cycles to 1 cycle resulted in a compact layer after thermal treatment, whereas the 1:1 composite showed numerous cracks. Slow thermal annealing at the rate of 10 °C/h of the 5:1 alloy leads to the decrease of refractive index from n = 1.52 to n = 1.34 with a thickness loss of ∼28%. Fast heating rate of 120 °C/h results in a larger thickness loss of ∼37% and the development of a more dense film with an effective refractive index of n = 1.40. The slow thermal annealing facilitates the formation of larger pores resulting in films with considerably lower refractive index. The atomic layer deposition/MLD approach is highly promising to develop novel, nanoporous, low index functional materials for different applications in optical coatings, catalysis, or gas separation.
A field‐shaping multi‐well avalanche detector for direct conversion amorphous selenium
Authors: Goldan A. H. , Zhao W.
Published: December 2012

Purpose:

A practical detector structure is proposed to achieve stable avalanche multiplication gain in direct‐conversion amorphous selenium radiation detectors.

Methods:

The detector structure is referred to as a field‐shaping multi‐well avalanche detector. Stable avalanche multiplication gain is achieved by eliminating field hot spots using high‐density avalanche wells with insulated walls and field‐shaping inside each well.

Results:

The authors demonstrate the impact of high‐density insulated wells and field‐shaping to eliminate the formation of both field hot spots in the avalanche region and high fields at the metal–semiconductor interface. Results show a semi‐Gaussian field distribution inside each well using the field‐shaping electrodes, and the electric field at the metal–semiconductor interface can be one order‐of‐magnitude lower than the peak value where avalanche occurs.

Conclusions:

This is the first attempt to design a practical direct‐conversion amorphous selenium detector with avalanche gain.
Survival of tumor and normal cells upon targeting with electron‐emitting radionuclides
Authors: Rajon Didier , Bolch Wesley E. , Howell Roger W.
Published: December 2012

Purpose:

Previous studies have shown that the mean absorbed dose to a tissue element may not be a suitable quantity for correlating with the biological response of cells in that tissue element. Cell survival can depend strongly on the distribution of radioactivity at the cellular and multicellular levels. Furthermore, when cellular absorbed doses are examined, the cross‐dose from neighbor cells can be less radiotoxic than the self‐dose component. To better understand how the nonuniformity of activity among cells can affect the dose response, a computer model of a 3D tissue culture was previously constructed and showed that activity distribution among cells is significantly more relevant than the mean absorbed dose for low‐energy‐electron emitters. The present work greatly expands upon those findings.

Methods:

In the present study, we used this same computer model but restricted the number of labeled cells to a fraction of the whole cell population (50%, 10%, and 1%, respectively). The labeled cells were randomly distributed among the whole cell population.

Results:

While the activity distribution is an important factor in determining the tissue response for low‐energy‐electron emitters, the fraction of labeled cells has an even more pronounced effect on survival response. For all electron energies studied, reducing the percentage of cells labeled significantly increases the surviving fraction of the whole population.

Conclusions:

This study provides abundant information on killing tumor and normal cells under some conditions relevant to targeted radionuclide therapy of isolated tumor cells and micrometastases. The percentage of cells labeled, activity distribution among the labeled cells, and electron energy play key roles in determining their response. Most importantly, and not previously demonstrated, lognormal activity distributions can have a profound impact on the response of the tumor cells even when the radionuclide emits high‐energy electrons.
Dynamic modulated brachytherapy (DMBT) for rectal cancer
Authors: Webster Matthew J. , Devic Slobodan , Vuong Te , Yup Han Dae , Park Justin C. , Scanderbeg Dan , Lawson Joshua , Song Bongyong , Tyler Watkins W. , Pawlicki Todd , Song William Y.
Published: December 2012

Purpose:

All forms of past and current high‐dose‐rate brachytherapy utilize immobile applicators during treatment delivery. The only moving part is the source itself. This paradigm misses an important degree of freedom that, if explored, can in some instances produce previously unachievable dose conformality; that is, the dynamic motion of the applicator itself during treatment delivery. Monte Carlo and treatment planning simulations were used to illustrate the potential benefits of moving applicators for rectal cancer applications in particular. This concept is termed dynamic modulated brachytherapy (DMBT).

Methods:

The DMBT system uses a high‐density, 18.0 g/cm3, 45 mm long tungsten alloy shield, cylindrical in shape, with a small window on one side to encapsulate a 192Ir source, to create collimation that results in a highly directional beam profile. This shield can be dynamically translated and rotated, using an attached robotic arm, during treatment to create a volumetric modulated arc therapy‐type delivery, but from inside the rectal cavity. Monte Carlo simulations and planning optimization algorithms were developed inhouse to evaluate the effectiveness of this new approach using 36 clinical treatment plans comprised of 13 patients each treated using the intracavitary mold applicator (ICMA, Nucletron, The Netherlands) to quantify the potential clinical benefit. The prescription dose was 10 Gy/fx and the group had an average clinical target volume of 9.0 ± 3.5 cm3. Ideal phantom geometries were used to evaluate the impact of various shield dimensions and designs on the resulting plan quality.

Results:

Simulations of ideal phantom geometries found that shields as small as 10 mm in diameter can produce high quality plans. For the clinical patient cases, compared to the ICMA, for equal prescription tumor coverage, the DMBT plans provided >30% decrease in D5 (high dose volume) resulting in a ∼40% decrease in dose heterogeneity index. In addition, mean dose and D98 showed a reduction (typically 40%–60%) on all critical structures evaluated. However, for a 10 Gy prescribed dose there was an increase in total treatment time on average from 7.6 to 20.8 min for a source with an air‐kerma strength of 40.25 kU (10 Ci).

Conclusions:

Dosimetric properties of a novel DMBT system have been described and evaluated. Comparison with the ICMA commercial applicator has shown it to be a prospective step forward in high‐dose‐rate brachytherapy192Ir technology. Dynamic motion of an applicator during treatment, for any applicator and site in general, can provide additional degrees of freedom that, if properly considered, can potentially increase the plan quality significantly.
Three‐dimensional optoacoustic tomography using a conventional ultrasound linear detector array: Whole‐body tomographic system for small animals
Authors: Gateau Jérôme , Caballero Miguel Ángel Araque , Dima Alexander , Ntziachristos Vasilis
Published: December 2012

Purpose:

Optoacoustic imaging relies on the detection of ultrasonic waves induced by laser pulse excitations to map optical absorption in biological tissue. A tomographic geometry employing a conventional ultrasound linear detector array for volumetric optoacoustic imaging is reported. The geometry is based on a translate‐rotate scanning motion of the detector array, and capitalizes on the geometrical characteristics of the transducer assembly to provide a large solid angular detection aperture. A system for three‐dimensional whole‐body optoacoustic tomography of small animals is implemented.

Methods:

The detection geometry was tested using a 128‐element linear array (5.0/7.0 MHz, Acuson L7, Siemens), moved by steps with a rotation/translation stage assembly. Translation and rotation range of 13.5 mm and 180°, respectively, were implemented. Optoacoustic emissions were induced in tissue‐mimicking phantoms andex vivo mice using a pulsed laser operating in the near‐IR spectral range at 760 nm. Volumetric images were formed using a filtered backprojection algorithm.

Results:

The resolution of the optoacoustic tomography system was measured to be better than 130μm in‐plane and 330 μm in elevation (full width half maximum), and to be homogenous along a 15 mm diameter cross section due to the translate‐rotate scanning geometry. Whole‐body volumetric optoacoustic images of mice were performed ex vivo, and imaged organs and blood vessels through the intact abdominal and head regions were correlated to the mouse anatomy.

Conclusions:

Overall, the feasibility of three‐dimensional and high‐resolution whole‐body optoacoustic imaging of small animal using a conventional linear array was demonstrated. Furthermore, the scanning geometry may be used for other linear arrays and is therefore expected to be of great interest for optoacoustic tomography at macroscopic and mesoscopic scale. Specifically, conventional detector arrays with higher central frequencies may be investigated.
A multitarget training method for artificial neural network with application to computer‐aided diagnosis
Authors: Liu Bei , Jiang Yulei
Published: December 2012

Purpose:

The authors propose a new training method for artificial neural networks (ANNs) in two‐class classification tasks such as classifying breast lesions on a mammogram as malignant or benign.

Methods:

Whereas the conventional binary training method uses binary training target values based on the diagnostic truth of a lesion being malignant or benign, the authors use multiple training target values based on more detailed histological diagnosis that presumably are related to the posterior probability of a lesion being malignant. The authors performed Monte Carlo simulation studies in which training target values were assigned based on posterior probability, and they also performed a mammography study in which training target values were assigned according to histological subtypes.

Results:

These studies showed that the multitarget training method produced less variability in the ANN outputs than the binary training method. The simulation studies also showed that except for when the number of training cases was extremely large, the multitarget training method produced improved overall classification performance over the binary training method.

Conclusions:

Therefore, the multitarget ANN training method is potentially useful for ANN applications in computer‐aided diagnosis of breast cancer.
The assessment of postural control and the influence of a secondary task in people with anterior cruciate ligament reconstructed knees using a Nintendo Wii Balance Board
Authors: Howells Brooke E , Clark Ross A , Ardern Clare L , Bryant Adam L , Feller Julian A , Whitehead Timothy S , Webster Kate E
Published: December 2012

Background

Postural control impairments may persist following anterior cruciate ligament (ACL) reconstruction. The effect of a secondary task on postural control has, however, not been determined. The purpose of this case–control study was to compare postural control in patients following ACL reconstruction with healthy individuals with and without a secondary task.

Participants

45 patients (30 men and 15 women) participated at least 6 months following primary ACL reconstruction surgery. Participants were individually matched by age, gender and sports activity to healthy controls.

Materials

Postural control was measured using a Nintendo Wii Balance Board and customised software during static single-leg stance and with the addition of a secondary task. The secondary task required participants to match the movement of an oscillating marker by adducting and abducting their arm.

Main outcome measures

Centre of pressure (CoP) path length in both medial-lateral and anterior–posterior directions, and CoP total path length.

Results

When compared with the control group, the anterior–posterior path length significantly increased in the ACL reconstruction patients' operated (12.3%, p=0.02) and non-operated limbs (12.8%, p=0.02) for the single-task condition, and the non-operated limb (11.5%, p=0.006) for the secondary task condition. The addition of a secondary task significantly increased CoP path lengths in all measures (p<0.001), although the magnitude of the increase was similar in both the ACL reconstruction and control groups.

Discussion

ACL reconstruction patients showed a reduced ability in both limbs to control the movement of the body in the anterior–posterior direction. The secondary task affected postural control by comparable amounts in patients after ACL reconstruction and healthy controls. Devices for the objective measurement of postural control, such as the one used in this study, may help clinicians to more accurately identify patients with deficits who may benefit from targeted neuromuscular training programs.
Clinical significance of ESR1 gene copy number changes in breast cancer as measured by fluorescence in situ hybridisation
Authors: Lin Ching-Hung , Liu Jacqueline M , Lu Yen-Shen , Lan Chieh , Lee Wei-Chung , Kuo Kuan-Ting , Wang Chung-Chieh , Chang Dwan-Ying , Huang Chiun-Sheng , Cheng Ann-Lii
Published: December 2012

Aims

TheESR1gene encodes for oestrogen receptor (ER) α, which plays a crucial role in mammary carcinogenesis and clinical outcome in patients with breast cancer. However, the clinical significance of theESR1gene copy number change for breast cancer has not been clarified.

Methods

ESR1gene copy number was determined by fluorescence in situ hybridisation (FISH) on tissue sections. A minimum of 20 tumour cells were counted per section, and a FISH ratio ofESR1gene to CEP6 ≥2.0 was consideredESR1amplification. A ratio >1.2 but <2.0 was consideredESR1gain. TheESR1copy number was further measured by quantitative real-time PCR (Q-PCR) with ASXL2 as a reference.

Results

FISH revealedESR1amplification in six cases (4.0%) andESR1gain in 13 cases (8.7%) from a total of 150 cases.ESR1gain and amplification were more common in older patients (p<0.001), and correlated well with ER protein expression (p=0.03) measured by immunohistochemistry, andESR1copy number (p<0.001) measured by Q-PCR. Furthermore, the multivariate analysis revealed thatESR1amplification was associated with a shorter disease-free survival (HR=5.56, p=0.03) and a shorter overall survival (HR=5.11, p=0.04).

Conclusions

In general, the frequency ofESR1amplification in breast cancer is low when measured by FISH in large sections.ESR1gain and amplification in breast cancer may be associated with older age and poorer outcomes.
Low-grade adenosquamous carcinoma of the breast
Authors: Soo Kailing , Tan Puay Hoon
Published: December 2012

Low-grade adenosquamous carcinoma is a rare and unique form of invasive mammary carcinoma. Though it is categorised as a variant of metaplastic carcinoma, it differs from its counterparts in this heterogeneous category by its relative clinical indolence, also reflected histologically in its low-grade cytomorphology. Descriptions of such a tumour were reported as early as 1912. However, low-grade adenosquamous carcinoma was only formally recognised in 1987 with the publication of Rosen and Ernsberger's landmark paper. Since then, several case reports and larger series have reaffirmed the clinicopathological characteristics of this unusual and uncommon tumour. Due to its rarity, however, many aspects of low-grade adenosquamous carcinoma, including its immunohistochemical and genetic profiles, remain unclear. This paper reviews the literature on this entity from 1987 to date, summarising its clinical and pathological features, and highlighting the diagnostic challenges it poses.
Correlation between placental bacterial culture results and histological chorioamnionitis: a prospective study on 376 placentas
Authors: Queiros da Mota Vanessa , Prodhom Guy , Yan Pu , Hohlfheld Patrick , Greub Gilbert , Rouleau Caroline
Published: December 2012

Objective

To study the correlation between the bacteriological and histopathological findings in placentas from women with suspected or proven chorioamnionitis (CA).

Methods

Over a 1-year period, 376 placentas were prospectively collected and processed for bacteriological and pathological studies in cases of confirmed or suspected maternal or neonatal infection.

Results

Histological CA was diagnosed in 26.9% of placentas (101/376), and 27.7% (28/101) of these placentas had positive bacteriological cultures. A monomicrobial culture, mainly represented by Gram-positive cocci and Gram-negative bacilli, was identified in 27% of the positive bacterial cultures. The proportion of positive cultures was higher (p=0.03) when CA was associated with funisitis, as compared with placental samples with early CA. In placentas without histological CA, bacteriological cultures were mostly negative (230/275), although pathogenic bacteria were identified in 16.3% of them (45/275).

Conclusions

The histological and bacteriological results were concordant in about 70% of the examined placentas, with 61.1% negative cases (CA absent and negative bacterial cultures), and only 7.4% placentas with positive histological and bacteriological results. Discordant results (positive histology with negative bacteriology) were obtained in placentas with early CA documented by histology although possibly in relation with antibiotic prophylaxis and the presence of fastidious bacteria. Conversely, negative histology with positive bacteriology could be explained by the presence of an early-stage bacterial infection that has not yet led to detectable microscopic lesions.
Adenocarcinoma of gallbladder: an immunohistochemical profile and comparison with cholangiocarcinoma
Authors: Hughes Norman Richard , Bhathal Prithi S
Published: December 2012

Aim

Cholangiocarcinomas display intestinal and pyloric gland metaplasia-cell phenotypes. Those that arise in chronically inflamed (fluke infested) bile ducts more frequently express the intestinal metaplasia-cell phenotype and p53 than sporadic cholangiocarcinomas. We wished to determine if adenocarcinomas of the gallbladder display a similar profile.

Methods

Adenocarcinoma, adenoma, and dysplastic and metaplastic epithelia were studied in 55 gallbladders. Serial paraffin sections were stained for five foregut antigens characteristically present in pyloric gland metaplasia, three intestinal-specific antigens and p53. Antigen expression was compared with that shown by 65 fluke-associated and 47 sporadic cholangiocarcinomas.

Results

Pyloric gland metaplasia in gallbladders with chronic cholecystitis invariably displayed the five foregut antigens. The frequency of expression of these five antigens by the gallbladder cancers and cholangiocarcinomas did not differ significantly. An intestinal goblet-cell marker and p53 were more frequently expressed by gallbladder carcinoma (59% and 45%, respectively) and fluke-associated cholangiocarcinoma (45% and 46%) than by sporadic cholangiocarcinoma (17% and 23%). K20 was more frequently expressed by gallbladder carcinoma (52%) than either fluke-associated (21%) or sporadic (17%) cholangiocarcinoma. Dysplastic epithelium and adenomas also displayed the pyloric gland and intestinal metaplasia-cell phenotypes. Cells staining for pyloric gland metaplasia-cell phenotypes were distinct from the intestinal metaplasia-cell phenotypes when present together in a gallbladder carcinoma, cholangiocarcinoma, dysplastic epithelium or adenoma.

Conclusions

Adenocarcinomas of gallbladder generally arise from a foregut cell lineage via a metaplasia-dysplasia-carcinoma sequence. A background of chronic inflammation increases the frequency of expression of an intestinal goblet-cell phenotype and p53 in the cancers.
Helicobacter pylori-associated hypochlorhydria in children, and development of iron deficiency
Authors: Harris Paul R , Serrano Carolina A , Villagrán Andrea , Walker Marjorie M , Thomson Melanie , Duarte Ignacio , Windle Henry J , Crabtree Jean E
Published: December 2012

Aims

AcuteHelicobacter pyloriinfection is associated with transient hypochlorhydria. InH pylori-associated atrophy, hypochlorhydria has a role in iron deficiency (ID) through changes in the physiology of iron-complex absorption. The aims were to evaluate the association betweenH pylori-associated hypochlorhydria and ID in children.

Methods

Symptomatic children (n=123) were prospectively enrolled. Blood, gastric juice and gastric biopsies were taken, respectively, for haematological analyses, pH assessment andH pyloridetermination, and duodenal biopsies for exclusion of coeliac disease. Stool samples were collected for parasitology/microbiology. Thirteen children were excluded following parasitology and duodenal histopathology, and five due to impaired blood analysis.

Results

Ten children were hypochlorhydric (pH>4) and 33 wereH pyloripositive. InH pylori-positive children with pH>4 (n=6) serum iron and transferrin saturation levels % were significantly lower (p<0.01) thanH pylori-positive children with pH≤4. No differences in ferritin, or total iron binding capacity, were observed. InH pylori-negative children with pH>4, iron and transferrin saturation were not significantly different from children with pH≤4.

Conclusions

Low serum iron and transferrin in childhoodH pyloriinfection is associated with hypochlorhydria. In uninfected children, hypochlorhydria was not associated with altered serum iron parameters, indicating a combination ofH pyloriinfection and/or inflammation, and hypochlorhydria has a role in the aetiology of ID. AlthoughH pylori-associated hypochlorhydria is transient during acute gastritis, this alters iron homeostasis with clinical impact in developing countries with a highH pyloriprevalence.