bluuebunny/crossref_metadata_2025 huggingface dataset:
Intercomparison of Temperature Sensors for Outdoor Monitoring of Photovoltaic Modules
Authors: Jankovec Marko , Topič Marko
Published: April 2013

Solar cells' temperature is a very important parameter that affects performance of photovoltaic (PV) modules since main electrical parameters of PV cells and modules are temperature dependent regardless the technology. The present study evaluates and compares different sensor types and mountings for long term outdoor temperature monitoring of PV modules along with a standardized method for determination of cell's temperature from open-circuit voltage. For that purpose, a special multicrystalline silicon PV module with miniature in situ Pt1000 temperature sensors was used for reference temperature measurement. On the back side of the PV module different temperature sensors were attached, including thermocouple (TC), platinum Pt1000 (PT) and digital temperature sensors DS18B20 (DS). All sensors except one were covered by a 1 cm thick insulation block. The whole setup was mounted on the outdoor PV testing site and all temperatures were monitored for several days with selection of different environmental conditions. On the basis of measurement results, deviations of different temperature sensors are investigated and compared to temperature calculated from open-circuit voltage measurement according to standard EN 60904-5. Among sensors attached at the back side, covered PT and TC sensors deliver the best results in range of 1–2 °C of lower temperature in average; while the covered DS sensor gives additional 1–2 °C underestimated temperature values. The worst measurement results demonstrate the PT sensor without insulation. All temperature sensors exhibit similar and adequate time response regarding the thermal capacitance of the PV module. DS sensors, although showing somewhat worse results, offer great advantages if several temperatures have to be acquired simultaneously and require very simple data acquisition equipment. They feature comparable measurement accuracy than commonly used Pt1000 temperature sensors if they are covered by insulation with 10 mm thick walls in lateral direction to avoid micro-environmental changes.
Thermodynamic Analyses of Single Brayton and Combined Brayton–Rankine Cycles for Distributed Solar Thermal Power Generation
Authors: Dunham M. T. , Lipiński W.
Published: April 2013

This paper reports theoretical efficiencies of single Brayton and combined Brayton–Rankine thermodynamic power cycles for distributed solar thermal power generation. Thermodynamic analyses are conducted with a nominal heat input to the cycle of 150 kW and component parameters for a 50 kWe gas microturbine for selected working fluids including air, Ar, CO2, He, H2, and N2 for the Brayton cycle and for the topping cycle of the combined system. Cycle parameters including maximum fluid temperature based on solar concentration ratio, pressure loss, and compressor/turbine efficiencies are then varied to examine their effect on cycle efficiency. C6-fluoroketone, cyclohexane, n-pentane, R-141b, R-245fa, and HFE-7000 are examined as working fluids in the bottoming segment of the combined cycle. A single Brayton cycle is found to reach a peak cycle efficiency of 15.31% with carbon dioxide at design point conditions. Each Brayton cycle fluid is examined as a topping cycle fluid in the combined cycle, being paired with six potential bottoming fluids, resulting in 36 working fluid configurations. The combination of the Brayton topping cycle using carbon dioxide and the Rankine bottoming cycle using R-245fa gives the highest combined cycle efficiency of 21.06%.
Adaptive Concepts for Herschel–Quincke Waveguides
Authors: Alonso Jose S. , Burdisso Ricardo A. , Ivers Douglas , Kwan Hwa W.
Published: April 2013

The enhancement of Herschel–Quincke (HQ) waveguides to incorporate adaptive capabilities is investigated. Passive HQ waveguides are known to provide noise attenuation in pipes and ducts at selective narrow frequency bands associated with their resonances. The approach to achieve adaptation is to produce a frequency shift in these resonances to allow targeting incoming tonal noise of variable frequency. The frequency shift is obtained by placing a variable cross-section constriction along the interior of the waveguide. Two adaptive devices are considered. The first consists of a ball with fixed diameter that can be axially displaced inside the waveguide. Then, the frequency tuning is obtained as a function of the ball position. The second device consists of a diaphragm at fixed axial location which can be deformed to obtain a variable cross section. In this case, the frequency shift is obtained as a function of the diaphragm deflection. The internal acoustic dynamics of the two devices are investigated both analytically and experimentally. The created constriction inside the HQ waveguide is modeled as a series of constant cross-section tube elements with small finite area jump between adjacent pieces. The model is validated by comparing the predicted dynamics with experimental data from an extended impedance tube setup based on the two-microphone technique. Finally, attenuation predictions on a one-dimensional pipe are presented in order to illustrate the performance of the proposed adaptive HQ waveguides.
Po‐Poster ‐ 13: A physical explanation for the failure of chamber calibrations for low energy brachytherapy seeds
Authors: Kay I
Published: April 2013

In the last few years it has become apparent that for low energy sources, chamber calibration factors are in error when used at sites with significant elevations. Empirical correction factors have been measured and published, but not a physical explanation of the effect. As the effect is only for low energy and not high energy sources, the explanation must lie in the relative ranges of the electrons set in motion in the wall. If all electrons stop in the chamber cavity, no correction for temperature and pressure need be applied. If all electrons cross the cavity then the usual Ctp correction is appropriate. For Ir‐192 or Cs‐137 sources, applying Ctp to account for changes of ambient pressure is appropriate. However, for lower energy sources (I‐125 or Pd‐103) a simple model predicts a significant number of electrons stop in the chamber and Ctp over‐corrects for the difference in ambient pressure. An analytic solution for a semi‐infinite parallel plate chamber predicts a behaviour similar to that described by the empirical correction factor. A simple numerical model of a well chamber shows that geometry is a second order effect, and that the ratio of cavity dimension to electron range is the principle physical consideration.
Po‐Poster ‐ 16: Correcting geometric distortion of EPID images
Authors: Gao Z , Gerig L , Szanto J
Published: April 2013

The use of Camera based Electronic Portal Image Devices (EPIDs) for online patient positioning is limited by their performance characteristics including image quality, mechanic stability and both geometric and intensity distortion. Geometric distortion of the EPID images arises in the imaging chain from lens or mirror distortions or from misalignment of the mirror. Correcting this geometric distortion requires mapping the EPID images into flat Cartesian space. In this work, we describe a simple method to measure this image distortion and to develop the appropriate image‐to‐physical space transforms using the properties of the MLC. An well characterized geometric pattern is created in the image plane by the superposition of two images. The individual images are created having every second MLC leaf pair fully closed while the adjacent pair is fully open. A second image is produced using exactly the same leaf configuration, but with the collimator rotated 90 degrees. The composite image is the sum of the two images and produces a well‐defined geometric pattern. A threshold function is applied to the composite image to produce a binary grid and the centroid of each dark/light square was determined. An affine transformation matrix is then generated to map the image of grid back to the virtual grid (physical space), thus correcting the spatial distortion. The mapping function was tested at various gantry angles and demonstrated to be robust.
Po‐Poster ‐ 18: Investigation of tilted dose kernels for portal dose prediction in a‐Si electronic portal imagers
Authors: McCurdy B , Chytyk K
Published: April 2013

The effect of beam divergence on dose calculation in an amorphous silicon electronic portal imaging device (EPID) was investigated with Monte Carlo generated dose kernels. The flat‐panel detector was simulated in EGSnrc (user code DOSXYZnrc) with a 3.0 cm water buildup; the model included details of the detector's imaging cassette and the front cover upstream of it. To approximate the effect of the EPID's rear housing, a 21 mm air gap and 10 mm water slab were introduced into the simulation as equivalent backscatter material. Kernels were generated with monoenergetic 2, 6, and 18 MeV photons with the orientation of the pencil beam varying from 0 to 14 degrees in 2 degree increments. Dose was scored in the phosphor layer of the detector. To reduce statistical fluctuations at large radial distances from the incident pencil beam, the kernels were first averaged bilaterally and then combined into square half rings. Profiles of the kernels were observed to demonstrate increasing asymmetry with increasing angle and energy, while the total energy deposited in the phosphor by the 2 MeV pencil beam decreased by greater than 2% at larger angles. Further investigation via comparison of superposition to convolution dose calculation methods is required to determine the effect these angled kernels have on calculation accuracy in clinical beam geometry.
Po‐Poster ‐ 21: On the use and sensitivity of dose‐functional volume histograms in radiation treatment planning
Authors: Basran P
Published: April 2013

With the increased use of multi‐modality imaging in radiation oncology, dose functional volume histograms (DfVHs) have been introduced as a simple and insightful means of incorporating healthy and diseased tissue functional information in treatment evaluation. The DfVHs themselves may also be used to estimate radiobiological metrics such as the Equivalent Uniform Dose (EUD) or probability of tumor control and normal tissue damage. As the concepts of the DfVH and its utility in computing radiobiological metrics are still in development, the purpose of this work was to investigate the interpretation and sensitivities of DfVH curves and subsequently deduced radiobiological estimates by using mathematically defined and perturbed functional image data sets. Factors such as the signal to noise ratio of the functional image, the relationship between signal intensity of the functional image to the number of functional sub‐units in the voxel, and the extent of mis‐alignment of the functional image to the dose distribution all may affect the shape of the DfVH. As a consequence radiobiological metrics, such as the EUD, are also sensitive to these factors and caution is recommended when using these functions as a predictive measure of outcome. Despite this, the simplicity and relative robustness of the DfVH provides an efficient means of ranking the quality of competing treatment plans. This work was funded through a grant from the MDS‐Nucletron CCO Medical Physics Fund.
Po‐Poster ‐ 25: Robust 3D prostate model reconstruction from a sparse collection of non‐parallel 2D TRUS biopsy images
Authors: Cool D , Downey D , Peters T , Fenster A
Published: April 2013

Biopsy of the prostate using 2D transrectal ultrasound (TRUS) guidance is the current gold standard for diagnosis of prostate cancer. Physicians' procedural accuracy and precision is limited by working within the current 2D biopsy environment that is susceptible to uncertainties when targeting 3D biopsy locations. We propose a technique for the reconstruction of a patient‐specific 3D prostate volume from a sparse collection of 2D US biopsy images that may be utilized for accurate prostate volume calculation. 2D TRUS biopsy images, with known 3D coordinates, were simulated from 3D US prostate image volumes acquired from biopsy patients. The prostate boundaries were manually outlined from each simulated biopsy image and radial basis functions were used to estimate the 3D prostate capsule from collections of 2D prostate outlines varying from 6–16 contours. Each reconstructed prostate model was compared to a manually segmented, 3D planimetry model for volume and surface boundary accuracy as well as the clinical‐standard prolate ellipsoid volume estimation technique. Prostate models reconstructed from one patient's simulated biopsy images demonstrated a consistent volume error range of 1.1%–0.4%, which was less than the clinical standard calculation that produced a 1.44% error. The mean prostate surface boundary error for all generated models was consistently < 1 mm with a RMS ≅ 1.1 mm. We have demonstrated a reconstruction technique capable of generating a 3D prostate model from a small sample of 2D TRUS biopsy images. This reconstruction technique has the potential to be incorporated into biopsy protocol for accurate volume measurements and needle guidance.
Po‐Poster ‐ 26: Investigation of normalized mutual information for co‐registration of CT — MR images of permanent prostate implants
Authors: Vidakovic S , Sloboda R
Published: April 2013

Post‐implant dosimetric evaluation is the standard contemporary method for assessing permanent prostate implant quality and determining the dose received by the prostate and organs at risk over the course of treatment. In current practice evaluation is performed using a CT image set typically acquired one month after the implant. However, due to poor visualization of prostate contours on the CT images, the evaluation can be difficult and is only approximate. MRI allows a better appreciation of prostate contours, but the visibility of the ensemble of the seeds is insufficient to allow its use as the only means of evaluating the treatment. Image registration of CT and MR image sets can combine the benefits of both imaging modalities and provide the means for sufficiently accurate dosimetric analysis. Mutual information is an efficient registration technique that can be used to fuse selected volumes of interest such as the prostate and neighbouring tissues. In our study we investigate optimization of registration search parameters, such as threshold level, translation and rotation angle ranges, and volume boundaries for fusing CT — MR images of a tissue equivalent prostate phantom implanted with inactive seeds, simulated image data, and clinical data sets. The results obtained so far are encouraging and suggest that mutual information‐based registration may eventually enable automatic fusion of clinical CT and MR images for prostate implant post‐dosimetry.
Po‐Poster ‐ 28: Examination of gene expression in p53(+/−) mice exposed to low dose radiation using Affymetrix cDNA microarrays
Authors: Morris D , Knox D , Lavoie J , Lemon J , Boreham D
Published: April 2013

Gamma radiation acts via the indirect effect to damage cells by producing reactive oxygen species (ROS). These ROS are capable damaging macromolecules and, altering signal pathways and gene transcription. Cells have evolved enzymes and mechanisms to scavenge ROS and repair oxidative damage. Microarrays allow the survey of the gene transcription activity of thousands of genes simultaneously. Messenger RNA is extracted from cells, hybridized with the complementary DNA (cDNA) of a microarray chip, and examined with a chip reader. Affymetrix microarray chips have been produced by the CSCHAH in Winnipeg containing 26000 murine genes. Groups of female mice have been exposed to low dose whole body chronic gamma radiation exposures of 0,50,100, and 120 mGy, corresponding to 15,30,60, and 75 weeks, respectively. MRNA from mice brain tissue has been extracted, isolated, converted to cDNA and labeled. Gene expression in each irradiated mouse was compared to the pooled expression of the control mice. Analysis of gene expression levels are performed with microarray analytical software, Array Pro by Media Cybernetics, and powerful statistical software, BRB microarray tools. Differences in gene expressions, focusing on genes for cytokines, DNA repair mechanisms, immuno‐modulators, apoptosis pathways, and enzymatic anti‐oxidant systems, are being examined and will be reported.
Sci‐AM Fri ‐ 06: Boxes, locks and talks: Making Class II compliance in a regulated environment
Authors: Evans M , DeBlois F , Abdel‐Rahman W , Corns R , Podgorsak E
Published: April 2013

Class II facilities in general and cancer centers running a radiation therapy program in particular, are being subjected to increasingly more rigorous regulation by the Canadian Nuclear Safety Commission (CNSC). The mission of the CNSC to regulate the use of nuclear energy and materials to protect health, safety, security and the environment can sometimes run counter to the day‐to‐day reality of running a cancer clinic. The recent division of our hospital radiation safety program into two distinct components: Class II (radiotherapy) and other (diagnostic radiology, nuclear medicine, research and laboratories, and consolidated), resulted in a significant improvement in the organization and delivery of radiation safety services. Performing the duties of a Class II Radiation Safety Officer to meet compliance requires a delicate balance of paper‐pushing and common sense: two activities that are often at odds with each other. License activities covered by CNSC document C‐120, such as applications and renewals as well as annual compliance reports, will be discussed. Devices we have installed to facilitate compliance for teletherapy and brachytherapy (HDR and manual) licenses will be presented. Procedures accepted by the CNSC for in‐house leak testing and survey meter calibration (R‐116 and R‐117) and suggestions for facilitating CNSC inspections and audits will also be discussed. Finally, a description of our approach to meeting several recent compliance requirements by the CNSC Nuclear Security Division (within the scope of Prescribed Information limitations) at our cancer center will be reviewed.
Sci‐YIS Fri ‐ 06: High spatial resolution magnetic resonance spectroscopic imaging of the brain at 3T for external beam radiation therapy planning
Authors: Heikal A , Wachowicz K , Fallone B
Published: April 2013

Recent research has shown that Magnetic Resonance Spectroscopic Imaging (MRSI) has good prospects for cancer detection and staging. Recent advancements in hardware in the form of RF coils and gradient sets have resulted in a good outlook for MRSI to be used in detection, localization, and classification of the lesions. Work done by other groups has shown that merging molecular imaging information from MRSI with anatomic scans used for treatment planning proved beneficial in delineating the tumor volume. MRSI involves defining an MR image volume which can be divided into a matrix of 3‐D sub‐volumes. Spectroscopic data is then acquired for all these sub‐volumes simultaneously. This leads to the quantification and localization of different levels of metabolites such as Choline, Creatine and N‐ acetylaspartate that are highly useful in detecting and possibly staging lesions. We focused on performing MRSI on the brain using a head transmit/receive (T/R) coil. Utilizing a reduced 2‐Dimensional Point Resolved Spectroscopy (2‐D PRESS) Turbo Spectroscopic Imaging (TSI) sequence to improve the spectral resolution of different metabolite peaks and the spatial resolution of the spectroscopic scan, good spectral/spatial information can be acquired revealing more accurate bio‐chemical imaging. Thus, an MRSI study could be easily used for improved treatment planning. Using 3T MRI we have improved the spatial resolution of the MRSI scans to 5×5×10mm3/voxel, meanwhile maintaining a good signal to noise ratio. This would increase the spatial relevance of the spectra acquired in the scan and in turn provide more information in the treatment planning phase.
Sci‐PM Fri ‐ 09: Image analysis of inter‐leaf radiation leakage, a new approach to the correction of EPID mechanic inconsistencies
Authors: Gao Z , Gerig L , Szanto J
Published: April 2013

Electronic portal imaging devices are valuable for analyzing patient treatment data for geometric errors. The analysis can be more robust if an absolute reference position such as the isocentre (collimator axis of rotation) is used, allowing discrimination between setup errors and Jaw/MLC calibration errors. Conventionally, investigators have extracted field edges through global thresholding, and compared the treated to the planned field placement using techniques such as the method of moments and normalized cross‐correlation. The accuracy of these methods depends on the accuracy and consistency of the MLC and Jaw calibration as well as on EPID performance such as intensity uniformity. In this work we describe how the MLC inter‐leaf radiation leakage, hidden in the background of portal images, can be extracted and analyzed to find the field isocentre. The peak locations of inter‐leaf radiation leakage in a portal image are extracted providing a very precise and accurate determination of the isocentre location in the direction perpendicular to the MLC leaf travel. Clearly orthogonal portal images can provide a very accurate determination of beam isocentre in both directions. The orientation of the interleaf leakage can also be used to determine mechanical inconsistencies in the EPID structure as a function of gantry angle. The image analysis of the inter‐leaf radiation leakage for determining imager translation and orientation is described.
Sci‐AM1 Sat ‐ 02: Dynamic intraoperative prostate brachytherapy
Authors: Wei Z , Fenster A
Published: April 2013

The aim of this paper is to develop a dynamic intraoperative prostate brachytherapy system in order to deal with variabilities in the current procedure. System consists of 3D TRUS imaging, a robot and software for prostate segmentation, intraoperative planning, oblique needle segmentation and tracking, seed segmentation, and 3D dose planning. The robot and 3D TRUS coordinate systems are unified with robot and image calibrations. In 3D TRUS images, the prostate is segmented using the discrete dynamic contour method, and optimal implantation plan is performed by using geometric optimization followed by simulated annealing. The inserted needles are segmented and tracked using grey‐level change in near real‐time, and seed segmentation is performed using 3D line segment patterns. Needle placement accuracy of the robot at the “patient” skin was 0.15mm±0.06mm, and needle angulation error was 0.07°. Needle targeting accuracy was 0.79mm±0.32mm. The average difference between manual and the prostate segmentation algorithm of prostate boundaries was −0.20±0.28mm. In our needle tracking tests, errors in determining needle orientation were less than 2° in robot yaw and 0.7° in robot pitch orientations, for up to 20° needle insertion angles when the needle insertion distance was greater than 15mm. The true‐positive rates for the seed segmentation algorithm in 3D TRUS images were 100% for agar and 93% for chicken phantoms. The result of this work provides a tool to achieve dynamic intraoperative prostate brachytherapy using 3D TRUS imaging and robotic assistance together with efficient segmentation software.
Sci‐AM1 Sat ‐ 08: Towards MR‐based treatment planning: Characterisation of geometric distortion in 3T MR images
Authors: Baldwin L , Wachowicz K , Fallone B
Published: April 2013

Because of the excellent soft‐tissue detail provided by MR images, it is the optimum imaging modality for treatment planning target delineation. While the structure of a tumor can be seen in great detail on MR images, the geometric accuracy of the images is limited by the homogeneity of the background field, the linearity of the applied gradients, and the magnetic susceptibility of the imaged tissues. As such, MR images cannot be used alone for novel treatment planning purposes (i.e. MR simulation), or in conjunction with CT because of geometric distortion. Our research seeks to quantify the amount of distortion in 3T MR images due to both background inhomogeneities and gradient nonlinearities on a sequence by sequence basis by using a specialized grid phantom and an in‐house developed software program. The matlab‐based program accurately determines the 3D coordinates of over 9000 control points distributed throughout the phantom's volume. Three dimensional distortion maps can be generated by comparing the control point coordinates determined from an MR scan to the control point coordinates determined from a CT scan. Control point locations can be determined to an accuracy of 0.2 mm and distortions as large as 13 mm have been measured. With appropriate post‐processing correction factors derived from the 3D distortion maps, MR images can be undistorted and either combined or used individually for new treatment planning methods that benefit from the superior soft‐tissue information that magnetic resonance techniques provide.
Sci‐AM2 Sat ‐ 01: A novel geometric analysis for beam angle optimization in 3D‐CRT based on target conformity
Authors: Potrebko P , McCurdy B
Published: April 2013

In radiotherapy, the primary goal is to deliver high dose to the Planning Target Volume (PTV) while sparing surrounding healthy tissue. For maximum radiation conformity to the PTV, one tries to achieve an extremely sharp dose gradient around the PTV. In this work, we have conducted a fundamental geometrical analysis of the PTV to explore the concept of geometrically inferring the preferred location of sharp dose gradients. To achieve this, the polygonal surface mesh data of the PTV was extracted from the Pinnacle3 treatment planning system and the surface normal of each polygon composing the PTV surface mesh was computed. Vectors describing the source/isocentre orientation of every possible couch and gantry combination were pre‐computed. If the polygon surface normal and the gantry‐couch vector were perpendicular, then the area of that polygon was cumulatively stored at the gantry‐couch combination. This beam orientation would then allow a beam to be aligned parallel to that particular surface of the PTV in order to produce a sharp dose gradient between the PTV and surrounding tissue. Optimal beam orientations were inferred from gantry‐couch combinations that were parallel to the largest cumulative area of PTV polygons. The algorithm was implemented on a cohort of prostate, lung, and head‐and‐neck patients. Optimal beam orientations for target conformity are presented for coplanar geometry, in order to simplify comparison to clinical beam configurations. This is the first work based on a geometric analysis of the PTV surface to demonstrate the 4‐field box configuration as an optimal orientation for prostate radiotherapy.
Sci‐AM2 Sat ‐ 03: Anatomy‐based MLC field optimization for the treatment of gynecologic malignancies
Authors: Nadeau S , Bouchard M , Germain I , Raymond P‐E , Beaulieu F , Beaulieu L , Roy R , Harel F , Gingras L
Published: April 2013

To evaluate the use of a new inverse planning system with anatomy‐based field segmentation, as an alternative between “4‐field box” and beamlet‐based IMRT, to treat whole pelvis of women with resected gynecologic malignancies. A class solution has been elaborated with the assistance of an in‐house optimization tool named Ballista. This inverse planning system can generate anatomy‐based MLC fields and simultaneously optimize their orientation and weight. The selected geometry consists of 7 coplanar and 2 noncoplanar incidences. For 10 patients planned to receive 45Gy for resected endometrial or cervix neoplasia, target volume and organ at risk (bowel, region “at risk to find bowel” (B‐RAR), bladder, rectum, bone marrow) were delineated. Using the Pinnacle3 planning system, four plans were generated for each patient: conventional 4‐field, enlarged 4‐field (aperture shaped to PTV),“step‐and‐shoot” IMRT and Ballista plans. Dose‐volume histograms, number of segments and monitor units (MU) were analyzed. Statistical significance is based on Student's paired t‐test. The mean volume of B‐RAR receiving 45Gy was: 4‐field, 49.7±7.1%; enlarged 4‐field, 63.4±5.8%; IMRT, 26.4±3.1%; Ballista, 29.0±3.0%. No statistical difference was noted between the ability of IMRT and Ballista to spare bowel (p=0.14), while both plans were better than 4‐field (p<0.001). The mean number of segments for Ballista was 33.3±2.3 vs 128.6±2.6 for IMRT and the mean number of MU was 325.0±11.8 vs 731.5±25.0. Weight optimization, with anatomy‐based MLC fields, is a good alternative between manual planning and IMRT for the treatment of gynecologic malignancies. Clinical results of treatment tolerance will follow.
Sci‐PM Sat ‐ 02: Development of a novel high quantum efficiency flat panel detector for megavoltage cone beam CT: An experimental study
Authors: Mei X , Pang G
Published: April 2013

Soft tissue imaging in the treatment room is one of the main challenges faced today in high precision radiotherapy. Megavoltage cone‐beam CT (MVCT) is a promising new imaging technique for image‐guided radiotherapy due to its simplicity and its potentially higher accuracy. However, currently the dose required to achieve sufficient soft tissue contrast to visualize and delineate, e.g., the prostate using MVCT is prohibitively large for daily verification. This is due to the low x‐ray absorption of the electronic portal imaging devices (EPIDs) used, i.e., low quantum efficiency (QE), which is typically on the order of 2–4%. Our overall goal is to develop a new generation of area detectors for MVCT, with a QE an order of magnitude higher than that of current EPIDs and yet an equivalent spatial resolution. With this new generation of detectors, the large dose currently required to visualize and delineate soft‐tissue targets with MVCT will be significantly reduced, and image‐guided radiotherapy using MVCT can be realized. In this work, we constructed a prototype single‐pixel detector based on the novel design introduced recently by Pang and Rowlands. Some fundamental imaging properties including the QE, spatial resolution, and sensitivity of the prototype detector were measured with a 6MV beam. It has been shown that the experimental results agree with our theoretical predictions and further development based on the novel design including the construction of a prototype area detector is warranted. This work was supported by the Department of Defense Prostate Cancer Research Program (DAMD17‐04‐1‐0276).
Science Signaling
Podcast: 30 April 2013
Authors: Borroni Elena M. , Bonecchi Raffaella , VanHook Annalisa M.
Published: April 2013

The chemokine scavenging activity of an atypical chemokine receptor requires signaling through β-arrestin.
Male and Female Plasmodium falciparum Mature Gametocytes Show Different Responses to Antimalarial Drugs
Authors: Delves Michael J. , Ruecker Andrea , Straschil Ursula , Lelièvre Jöel , Marques Sara , López-Barragán María José , Herreros Esperanza , Sinden Robert E.
Published: April 2013

It is the mature gametocytes of
Plasmodium
that are solely responsible for parasite transmission from the mammalian host to the mosquito. They are therefore a logical target for transmission-blocking antimalarial interventions, which aim to break the cycle of reinfection and reduce the prevalence of malaria cases. Gametocytes, however, are not a homogeneous cell population. They are sexually dimorphic, and both males and females are required for parasite transmission. Using two bioassays, we explored the effects of 20 antimalarials on the functional viability of both male and female mature gametocytes of
Plasmodium falciparum
. We show that mature male gametocytes (as reported by their ability to produce male gametes, i.e., to exflagellate) are sensitive to antifolates, some endoperoxides, methylene blue, and thiostrepton, with submicromolar 50% inhibitory concentrations (IC
50
s), whereas female gametocytes (as reported by their ability to activate and form gametes expressing the marker Pfs25) are much less sensitive to antimalarial intervention, with only methylene blue and thiostrepton showing any significant activity. These findings show firstly that the antimalarial responses of male and female gametocytes differ and secondly that the mature male gametocyte should be considered a more vulnerable target than the female gametocyte for transmission-blocking drugs. Given the female-biased sex ratio of
Plasmodium falciparum
(∼3 to 5 females:1 male), current gametocyte assays without a sex-specific readout are unlikely to identify male-targeted compounds and prioritize them for further development. Both assays reported here are being scaled up to at least medium throughput and will permit identification of key transmission-blocking molecules that have been overlooked by other screening campaigns.
ACH-806, an NS4A Antagonist, Inhibits Hepatitis C Virus Replication by Altering the Composition of Viral Replication Complexes
Authors: Yang Wengang , Sun Yongnian , Hou Xiaohong , Zhao Yongsen , Fabrycki Joanne , Chen Dawei , Wang Xiangzhu , Agarwal Atul , Phadke Avinash , Deshpande Milind , Huang Mingjun
Published: April 2013

Treatment of hepatitis C patients with direct-acting antiviral drugs involves the combination of multiple small-molecule inhibitors of distinctive mechanisms of action. ACH-806 (or GS-9132) is a novel, small-molecule inhibitor specific for hepatitis C virus (HCV). It inhibits viral RNA replication in HCV replicon cells and was active in genotype 1 HCV-infected patients in a proof-of-concept clinical trial (1). Here, we describe a potential mechanism of action (MoA) wherein ACH-806 alters viral replication complex (RC) composition and function. We found that ACH-806 did not affect HCV polyprotein translation and processing, the early events of the formation of HCV RC. Instead, ACH-806 triggered the formation of a homodimeric form of NS4A with a size of 14 kDa (p14) both in replicon cells and in Huh-7 cells where NS4A was expressed alone. p14 production was negatively regulated by NS3, and its appearance in turn was associated with reductions in NS3 and, especially, NS4A content in RCs due to their accelerated degradation. A previously described resistance substitution near the N terminus of NS3, where NS3 interacts with NS4A, attenuated the reduction of NS3 and NS4A conferred by ACH-806 treatment. Taken together, we show that the compositional changes in viral RCs are associated with the antiviral activity of ACH-806. Small molecules, including ACH-806, with this novel MoA hold promise for further development and provide unique tools for clarifying the functions of NS4A in HCV replication.
A Phenotype at Last: Essential Role for the Yersinia enterocolitica Ysa Type III Secretion System in a Drosophila melanogaster S2 Cell Model
Authors: Walker Kimberly A. , Maltez Vivien I. , Hall Joshua D. , Vitko Nicholas P. , Miller Virginia L.
Published: April 2013

The highly pathogenic
Yersinia enterocolitica
strains have a chromosomally encoded type III secretion system (T3SS) that is expressed and functional
in vitro
only when the bacteria are cultured at 26°C. Mutations that render this system nonfunctional are slightly attenuated in the mouse model of infection only following an oral inoculation and only at early time points postinfection. The discrepancy between the temperature required for the Ysa gene expression and the physiological temperature required for mammalian model systems has made defining the role of this T3SS challenging. Therefore, we explored the use of
Drosophila
S2 cells as a model system for studying Ysa function. We show here that
Y. enterocolitica
is capable of infecting S2 cells and replicating intracellularly to high levels, an unusual feature of this pathogen. Importantly, we show that the Ysa T3SS is required for robust intracellular replication. A secretion-deficient mutant lacking the secretin gene,
ysaC
, is defective in replication within S2 cells, marking the first demonstration of a pronounced Ysa-dependent virulence phenotype. Establishment of S2 cells as a model for
Y. enterocolitica
infection provides a versatile tool to elucidate the role of the Ysa T3SS in the life cycle of this gastrointestinal pathogen.
Alkaptonuria and pompe disease in one patient: metabolic and molecular analysis
Authors: Habbal Mohammad Zouheir , Bou Assi Tarek , Mansour Hicham
Published: April 2013

Pompe disease is characterised by deficiency of acid α-glucosidase that results in abnormal glycogen deposition in the muscles. Alkaptonuria is caused by a defect in the enzyme homogentisate 1,2-dioxygenase with subsequent accumulation of homogentisic acid. We report the case of a 6-year-old boy diagnosed with Pompe disease and alkaptonuria. Urine organic acids and α-glucosidase were measured. Homogentisate 1,2-dioxygenase (HGO) and acid alpha-glucosidase (GAA) genes were sequenced by Sanger DNA sequencing. The level of α-glucosidase in white blood cells was markedly decreased (4 nm/mg) while the level of homogentisic acid was markedly increased (15 027 mmol/mol creatine). GAA sequencing detected two heterozygous GAA mutations (C.670C>T and C.1064T>C) while HGO sequencing revealed three polymorphisms in exons 4, 5 and 6, respectively. To the best of our knowledge, this is the first reported instance of Pompe disease and alkaptonuria occurring in the same individual.
The ‘Jedward’ versus the ‘Mohawk’: a prospective study on a paediatric distraction technique
Authors: Fogarty Eoin , Dunning Eilis , Koe Stanley , Bolger Turlough , Martin Ciara
Published: April 2013

Objective

To examine the use of a standard hospital glove, inflated as a balloon with a face drawn on it, as a distraction technique in children with an acute injury.

Methods

We designed a study to assess the ‘best’ way to orientate the glove when drawing a face on it. A prospective study was performed in the authors’ institution, where all children between the ages of 2 and 8 years presenting during the study period were given the option of playing with one of two glove balloons with a face drawn on it in two different ways.

Results

149 paediatric patients were assessed, of whom 136 picked a glove, 75 picked the ‘Jedward’ version and 61 the ‘Mohawk’ version.

Conclusions

A standard hospital glove, inflated as a balloon with a face drawn on it, is a useful distraction for children with an acute injury. The face drawn should be drawn ‘Jedward’ style.
Effects of age, sex, and treatment on weight-loss dynamics in overweight people
Authors: Rojo-Tirado Miguel A. , Benito Pedro J. , Atienza David , Rincón Emiliano , Calderón Francisco J.
Published: April 2013

The objective of this work was to evaluate how sex, age, and the kind of treatment followed affect weight loss in overweight men and women, as well as to develop an explanation for the evolution of weight-loss dynamics. The study consisted of 119 overweight participants (18–50 years old, body mass index >25 and <29.9 kg·m-2), who were randomly assigned to 1 of 4 treatment programs, namely, strength training (n = 30), endurance training (n = 30), a combination of strength training and endurance training (n = 30), and a careful treatment including diet and physical recommendations (n = 29). Each of the training groups exercised 3 times per week for 24 weeks, and their daily diet was restricted to a specific protocol during the testing period and controlled carefully. Body weight changes in the participants were evaluated every 15 days. Based on this study, we developed and validated different sets of equations to accurately capture the weight-loss dynamics. There were no significant differences in terms of global body weight changes from the statistical viewpoint, either regarding the carried out treatment or the individuals’ ages. However, significant differences in weight-loss tendency were found depending on participant sex. We concluded that the effectiveness of different possible treatments for weight loss varies by sex and, based on our experimental observations, a quadratic function provides the most accurate model for capturing specific weight-loss dynamics. This trial is registered at Clinical Trials Gov.: number NCT01116856.
Can scar-based fire history reconstructions be biased? An experimental study in boreal Scots pine
Authors: Piha Aura , Kuuluvainen Timo , Lindberg Henrik , Vanha-Majamaa Ilkka
Published: April 2013

Determining forest fire history is commonly based on fire scar dating with dendrochronological methods. We used an experimental setup to investigate the impacts of low-intensity prescribed fire on fire scar formation 8 years after fire in 12 young managed Scots pine (Pinus sylvestris L.) stands. Five stands were between 30 and 35 years old and seven were 45 years old at the time of burning. A total of 217 fire scars were recorded in 142 trees. The number of separate scars per tree originating from a single fire ranged from 1 to 6, with 67% of the trees having just one scar. The proportion of fire-scarred trees out of all trees per plot ranged from 0% to 30%, averaging 16.5% in young stands and 2.8% in older stands. Four of the 12 burned plots did not have any trees with fire scars, and these were all in the older age group. This means that in the older stands, in only three of seven plots (43%) did the fire leave scars from which fire can potentially be detected and dated afterwards. Our results suggest that fire scar dating in Scots pine dominated forests may underestimate fire frequency, area, and the importance of historically common low-intensity surface fires in dendrochronological reconstructions of past fire histories.
TOEPLITZ OPERATORS AND THE ESSENTIAL BOUNDARY ON POLYANALYTIC FUNCTIONS
Authors: PESSOA LUÍS V.
Published: April 2013

Let j be a nonzero integer and let U be a bounded domain. We construct a Fredholm symbol calculus for the C*-algebra generated by the poly-Bergman projection and the operators of multiplication by continuous functions. We define the j-removal boundary in Hilbert spaces of polyanalytic functions and prove that the quotient poly-Toeplitz C*-algebra generated by cosets of poly-Toeplitz operators with continuous symbols is *-isomorphic to the C*-algebra of continuous functions over the j-essential boundary. Unlike the Bergman case, we also show that if j ≠ ±1 then the j-essential boundary coincides with the set of non-isolated points on the boundary.
ZERO NODES EFFECT: VALID LINK PREDICTION IN SPARSE NETWORKS
Authors: SHAO CHEN-XI , DOU HUI-LING , YANG RONG-XU , WANG BING-HONG
Published: April 2013

Zero-degree nodes are an important difficulty in sparse networks' link prediction. Clustering and preferential attachment, as the most important characteristics of complex networks, have been paid little attention in similarity indices. Inspired by the coexistence of clustering and preferential attachment in real networks, this paper proposes a new preferential attachment index and new clustering index, which have here been integrated into a hybrid index that considers the dynamic evolutionary forces of complex networks and can solve the problem of excessive zero-degree nodes in sparse networks and check evolution mechanism. Experiments proved prediction accuracy can be remarkably enhanced.
ANOMALIES IN SPECIFIC HEAT: THE INFLUENCE OF SPIN FLUCTUATIONS AND SUPERCONDUCTIVITY IN CUPRATES
Authors: MOHANTA K. L. , ROUT G. C.
Published: April 2013

We report here a microscopic theory of the temperature dependence of specific heat in high-Tc cuprate superconductors. The system is described by a model Hamiltonian consisting the antiferromagnetic spin fluctuations due to the impurity f-electrons as well as the conduction electrons, besides the superconducting interaction due to the itinerant electrons. The Hamiltonian is treated within a mean-field approach. The transverse spin fluctuation parameters and the superconducting gap are calculated by Zubarev's Green's function technique and solved self-consistently. The temperature dependent specific heat is calculated from the free energy in order to study the anomalies appearing at the spin fluctuation and superconducting transition temperatures. The evolutions of these anomalies are studied by varying the model parameters of the systems and results are discussed in reference to experimental observations.
CONVERGENCE OF A FINITE VOLUME SCHEME FOR GAS–WATER FLOW IN A MULTI-DIMENSIONAL POROUS MEDIUM
Authors: BENDAHMANE MOSTAFA , KHALIL ZIAD , SAAD MAZEN
Published: April 2013

This paper deals with construction and convergence analysis of a finite volume scheme for compressible/incompressible (gas–water) flows in porous media. The convergence properties of finite volume schemes or finite element scheme are only known for incompressible fluids. We present a new result of convergence in a two or three dimensional porous medium and under the only consideration that the density of gas depends on global pressure. In comparison with incompressible fluid, compressible fluids requires more powerful techniques; especially the discrete energy estimates are not standard.
DIFFRACTIVE INTERACTION OF NEUTRINOS
Authors: KOPELIOVICH B. Z. , POTASHNIKOVA I. K. , SCHMIDT IVÁN , SIDDIKOV M.
Published: April 2013

Interactions of high-energy neutrinos expose hadronic properties, in particular, contain a strong diffractive channel. The Adler relation (AR) between soft interactions of neutrinos and pions, might look as a manifestation of pion dominance. However, neutrinos cannot fluctuate to pions because of conservation of the lepton current, and interact via much heavier hadronic components. This fact leads to nontrivial relations between interactions of different hadronic species, in particular, it links diagonal and off-diagonal diffractive interactions of pions. Absorptive corrections break these relations making the AR impossible to hold universally, for any target and at any energy.
ON THE JLO COCYCLE AND ITS TRANSGRESSION IN ENTIRE CYCLIC COHOMOLOGY
Authors: LAI ALAN
Published: April 2013

The JLO character formula due to Jaffe–Lesniewski–Osterwalder [Quantum K-theory: the Chern character, Commun. Math. Phys.112 (1988) 75–88] assigns to each Fredholm module a cocycle in entire cyclic cohomology. It descends to define a cohomological Chern character on K-homology. This paper extends the definition of the JLO character formula for Breuer–Fredholm modules, the modules that represent type II noncommutative geometry; and shows that the JLO character formula coincides with the Connes character formula [see M. Benameur and T. Fack, Type II noncommutative geometry. I. Dixmier trace in von Neumann algebras, Adv. Math.199 (2006) 29–87] at the level of entire cyclic cohomology.
CURVATURE PROPERTIES OF 3-QUASI-SASAKIAN MANIFOLDS
Authors: CAPPELLETTI-MONTANO BENIAMINO , DE NICOLA ANTONIO , YUDIN IVAN
Published: April 2013

We find some curvature properties of 3-quasi-Sasakian manifolds which extend certain well-known identities holding in the Sasakian case. As an application, we prove that any 3-quasi-Sasakian manifold of constant horizontal sectional curvature is necessarily either 3-α-Sasakian or 3-cosymplectic.
FIBER INTEGRATION OF THE COUPLING CLASS
Authors: VIÑA ANDRÉS
Published: April 2013

Given a Hamiltonian action of a Lie group (not necessarily compact) on a symplectic manifold M, by means of the integration over M of the coupling class associated with this action, we define an element which is invariant under deformations of the action.
Selective oxidative synthesis of meso-beta fused porphyrin dimers
Authors: Brennan Bradley J. , Arero Jaro , Liddell Paul A. , Moore Thomas A. , Moore Ana L. , Gust Devens
Published: April 2013

An efficient route to meso-β doubly connected fused porphyrin dimers was developed. Synthesis of the dimers incorporated two successive C–C bond-forming steps selectively coupling unsubstituted meso- and β-positions. Using Cu(BF4)2 as an oxidant in nitromethane solvent, the radical coupling of Cu(II) -porphyrins occurred in high yield and without side-products, allowing chromatography-free purification. Efficient demetalation of the product yielded free-base derivatives and the possibility to incorporate other metals into the macrocycles. The absorption and electrochemical properties vary with the inserted metal, showing broad UV-visible-NIR absorption and multiple one-electron oxidations/reductions in a relatively narrow electrochemical window.