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Sample records for dual-layer mlc dynamic

  1. Dynamic MLC-QA Based On Portal Dosimetry

    Directory of Open Access Journals (Sweden)

    Sajeev Surendran

    2014-05-01

    Full Text Available Purpose: Intensity modulated radiotherapy using dynamic delivery method requires accurate verification of MLC, its position and speed of motion. These parameter have major impact on dose delivery on patients. For quality assurance (QA procedure requires more time consumed in a radiotherapy department. The main purpose of this study was to investigate the potential use of amorphous silicon based EPID portal dosimetry for dMLC QA Methods and Materials: A varian Clinac_iX with On Board Imager (OBI and Rapid Arc facility ( VMAT equipped with 120 leaf Millennium MLC and with Amorphous Silicon Based EPID (aSi-1000, varian mounted on a Exact Robotic Arm is used. The dMLC QA consists of different dynamic MLC pattern provided by varian for checking positional accuracy, MLC gap, Leaf speed and complex dynamic field. Results and Discussion: Various dMLC tests were done using portal dosimetry. All results are within the tolerance limit. Picket fence test shows that leaf position errors of upto 0.2mm can be detected which are within the tolerance limit. Complex dynamic field were exposed to EPID, which shows the leaf speed and are within the tolerance limit.

  2. Fast regional readout CMOS Image Sensor for dynamic MLC tracking

    Science.gov (United States)

    Zin, H.; Harris, E.; Osmond, J.; Evans, P.

    2014-03-01

    Advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT) require verification of the complex beam delivery including tracking of multileaf collimators (MLC) and monitoring the dose rate. This work explores the feasibility of a prototype Complementary metal-oxide semiconductor Image Sensor (CIS) for tracking these complex treatments by utilising fast, region of interest (ROI) read out functionality. An automatic edge tracking algorithm was used to locate the MLC leaves edges moving at various speeds (from a moving triangle field shape) and imaged with various sensor frame rates. The CIS demonstrates successful edge detection of the dynamic MLC motion within accuracy of 1.0 mm. This demonstrates the feasibility of the sensor to verify treatment delivery involving dynamic MLC up to ~400 frames per second (equivalent to the linac pulse rate), which is superior to any current techniques such as using electronic portal imaging devices (EPID). CIS provides the basis to an essential real-time verification tool, useful in accessing accurate delivery of complex high energy radiation to the tumour and ultimately to achieve better cure rates for cancer patients.

  3. Dynamic tumor tracking using the Elekta Agility MLC

    Energy Technology Data Exchange (ETDEWEB)

    Fast, Martin F., E-mail: martin.fast@icr.ac.uk; Nill, Simeon, E-mail: simeon.nill@icr.ac.uk; Bedford, James L.; Oelfke, Uwe [Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom)

    2014-11-01

    Purpose: To evaluate the performance of the Elekta Agility multileaf collimator (MLC) for dynamic real-time tumor tracking. Methods: The authors have developed a new control software which interfaces to the Agility MLC to dynamically program the movement of individual leaves, the dynamic leaf guides (DLGs), and the Y collimators (“jaws”) based on the actual target trajectory. A motion platform was used to perform dynamic tracking experiments with sinusoidal trajectories. The actual target positions reported by the motion platform at 20, 30, or 40 Hz were used as shift vectors for the MLC in beams-eye-view. The system latency of the MLC (i.e., the average latency comprising target device reporting latencies and MLC adjustment latency) and the geometric tracking accuracy were extracted from a sequence of MV portal images acquired during irradiation for the following treatment scenarios: leaf-only motion, jaw + leaf motion, and DLG + leaf motion. Results: The portal imager measurements indicated a clear dependence of the system latency on the target position reporting frequency. Deducting the effect of the target frequency, the leaf adjustment latency was measured to be 38 ± 3 ms for a maximum target speed v of 13 mm/s. The jaw + leaf adjustment latency was 53 ± 3 at a similar speed. The system latency at a target position frequency of 30 Hz was in the range of 56–61 ms for the leaves (v ≤ 31 mm/s), 71–78 ms for the jaw + leaf motion (v ≤ 25 mm/s), and 58–72 ms for the DLG + leaf motion (v ≤ 59 mm/s). The tracking accuracy showed a similar dependency on the target position frequency and the maximum target speed. For the leaves, the root-mean-squared error (RMSE) was between 0.6–1.5 mm depending on the maximum target speed. For the jaw + leaf (DLG + leaf) motion, the RMSE was between 0.7–1.5 mm (1.9–3.4 mm). Conclusions: The authors have measured the latency and geometric accuracy of the Agility MLC, facilitating its future use for clinical

  4. Implementation and acceptance of dynamic MLC for IMRT and VMAT; Implementacion y aceptacion de MLC dinamicos para IMRT y VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, B.; Marquina, J.; Ramirez, J.; Gonzales, A., E-mail: bertha.garcia@aliada.com.pe [ALIADA, Oncologia Integral, Av. Jose Galvez Barrenechea 1044, San Isidro, Lima 27 (Peru)

    2014-08-15

    The use of Multi-leaf Collimator (MLC) in Intensity-Modulated Radiation Therapy (IMRT) for dynamic treatment techniques as Volumetric Modulated Arc Therapy (VMAT) makes that the movement controls as the speed of the MLC are quantified by means of an acceptance test. The objective determination of the operation regulations of the radiotherapy equipment requires ideally the establishment of the quantitative relationship among the performance deviations and clinical results or some acceptable substitute. Different protocols exist detailed with parameters and acceptance ranges according to the MLC thickness. In our case the acceptance test was carried out for 120-MLC of Trilogy equipment brand Varian. For all the test were used 300-200 Um for each formed beam lets; source-surface distance (SSD) of 100 cm. 9 acceptance tests were used each one with different purposes like to quantify, synchronization, stability, complexity, precision, positioning, conformity, dynamic movements for the case of dynamic wedges, consecutive moves, among others, for the measurements were used film badges dosimetry (Gafchromic Ebt-3 scanner Epson expression 10000 XL); additionally the results were compared with a diodes arrangement Map-Check 2 brand Sun Nuclear; that consists of 1527 diodes prepared in a field of 32 x 26 cm located at a distance of 1 cm parallel, 0.5 cm diagonally. All the developed tests were inside the acceptance tolerance parameters when comparing the obtained result regarding the badges and the Map-Check was found a discrepancy of 0.01%, what gives a treatment certainty to the moment to impart volumetric dose in dynamic fields to the patients. (Author)

  5. Detailed analysis of latencies in image-based dynamic MLC tracking

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, Per Rugaard; Cho, Byungchul; Sawant, Amit; Ruan, Dan; Keall, Paul J. [Department of Radiation Oncology, Stanford University, Stanford, California 94305 and Department of Oncology and Department of Medical Physics, Aarhus University Hospital, 8000 Aarhus (Denmark); Department of Radiation Oncology, Stanford University, Stanford, California 94305 and Department of Radiation Oncology, Asan Medical Center, Seoul 138-736 (Korea, Republic of); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States)

    2010-09-15

    Purpose: Previous measurements of the accuracy of image-based real-time dynamic multileaf collimator (DMLC) tracking show that the major contributor to errors is latency, i.e., the delay between target motion and MLC response. Therefore the purpose of this work was to develop a method for detailed analysis of latency contributions during image-based DMLC tracking. Methods: A prototype DMLC tracking system integrated with a linear accelerator was used for tracking a phantom with an embedded fiducial marker during treatment delivery. The phantom performed a sinusoidal motion. Real-time target localization was based on x-ray images acquired either with a portal imager or a kV imager mounted orthogonal to the treatment beam. Each image was stored in a file on the imaging workstation. A marker segmentation program opened the image file, determined the marker position in the image, and transferred it to the DMLC tracking program. This program estimated the three-dimensional target position by a single-imager method and adjusted the MLC aperture to the target position. Imaging intervals {Delta}T{sub image} from 150 to 1000 ms were investigated for both kV and MV imaging. After the experiments, the recorded images were synchronized with MLC log files generated by the MLC controller and tracking log files generated by the tracking program. This synchronization allowed temporal analysis of the information flow for each individual image from acquisition to completed MLC adjustment. The synchronization also allowed investigation of the MLC adjustment dynamics on a considerably finer time scale than the 50 ms time resolution of the MLC log files. Results: For {Delta}T{sub image}=150 ms, the total time from image acquisition to completed MLC adjustment was 380{+-}9 ms for MV and 420{+-}12 ms for kV images. The main part of this time was from image acquisition to completed image file writing (272 ms for MV and 309 ms for kV). Image file opening (38 ms), marker segmentation (4 ms

  6. Implementation of a Quality Control using portal imaging dynamic MLC; Implementacion de un programa de control de calidad de MLC dinamico mediante imagen portal

    Energy Technology Data Exchange (ETDEWEB)

    Sanz Freire, C. J.; Vazquez Galinanes, A.; Collado Chamorro, P. M.; Diaz Pascual, V.; Gomez Amez, J.; Sanchez Martinez, S.; Ossola Lentati, G. A

    2011-07-01

    The precision in the correct beam irradiation in the treatment of highly modulated Intensity Modulated Radiation Therapy (IMRT) depends largely on the characteristics and behavior of the multi leaf collimator (MLC). Quality control (QC) of this element is essential to ensure proper delivery of the beams calculated. It is important to know the absolute position of each sheet, the motion characteristics of each behavior and stability. Among the numerous methods for carrying out the QC MLC, the use of portal imaging is a practical and high resolution. This paper describes the development of a quality control program based dynamic MLC portal image, self-developed software that enables analysis and the results of two years experience following the implementation of IMRT treatments at our center. (Author)

  7. The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

    DEFF Research Database (Denmark)

    Falk, Marianne; Larsson, Tobias; Keall, Paul

    2012-01-01

    -to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system. The dosimetric results were evaluated using gamma index evaluation with static target measurements as reference. Results: The plan quality......Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced...... on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans...

  8. Real-Time Dynamic MLC Tracking for Intensity Modulated Arc Therapy

    DEFF Research Database (Denmark)

    Falk, Marianne

    -fraction motion management that uses the MLC of the treatment machine to reshape the beam to follow the tumour movements. The 3D MLC tracking algorithm recalculates the planned MLC positions using information about the tumour location from an independent monitoring system and the leaves are adjusted accordingly...

  9. Real-Time Dynamic MLC Tracking for Intensity Modulated Arc Therapy

    DEFF Research Database (Denmark)

    Falk, Marianne

    -fraction motion management that uses the MLC of the treatment machine to reshape the beam to follow the tumour movements. The 3D MLC tracking algorithm recalculates the planned MLC positions using information about the tumour location from an independent monitoring system and the leaves are adjusted accordingly...

  10. RhoA-mediated MLC2 regulates actin dynamics for cytokinesis in meiosis.

    Science.gov (United States)

    Duan, Xing; Liu, Jun; Zhu, Cheng-Cheng; Wang, Qiao-Chu; Cui, Xiang-Shun; Kim, Nam-Hyung; Xiong, Bo; Sun, Shao-Chen

    2016-01-01

    During oocyte meiosis, the bipolar spindle forms in the central cytoplasm and then migrates to the cortex. Subsequently, the oocyte extrudes the polar body through two successive asymmetric divisions, which are regulated primarily by actin filaments. Myosin light chain2 (MLC2) phosphorylation plays pivotal roles in smooth muscle contraction, stress fiber formation, cell motility and cytokinesis. However, whether MLC2 phosphorylation participates in the oocyte polarization and asymmetric division has not been clarified. The present study investigated the expression and functions of MLC2 during mouse oocyte meiosis. Our result showed that p-MLC2 was localized in the oocyte cortex, with a thickened cap above the chromosomes. Meanwhile, p-MLC2 was also localized in the poles of spindle. Disruption of MLC2 activity by MLC2 knock down (KD) caused the failure of polar body extrusion. Immunofluorescent staining showed that a large proportion of oocytes arrested in telophase stage and failed to undergo cytokinesis after culturing for 12 hours. In the meantime, actin filament staining at oocyte membrane and cytoplasm were reduced in MLC2 KD oocytes. Finally, we found that the phosphorylation of MLC2 protein levels was decreased after disruption of RhoA activity. Above all, our data indicated that the RhoA-mediated MLC2 regulates the actin organization for cytokinesis during mouse oocyte maturation.

  11. Evaluation of MLC leaf positioning accuracy for static and dynamic IMRT treatments using DAVID in vivo dosimetric system.

    Science.gov (United States)

    Karagoz, Gulay; Zorlu, Faruk; Yeginer, Mete; Yildiz, Demet; Ozyigit, Gokhan

    2016-03-08

    Accuracy and precision of leaf positioning in multileaf collimators (MLCs) are significant factors for the accuracy of IMRT treatments. This study aimed to inves-tigate the accuracy and repeatability of the MLC leaf positioning via the DAVID invivo dosimetric system for dynamic and static MLC systems. The DAVID system was designed as multiwire transmission ionization chamber which is placed in accessory holder of linear accelerators. Each wire of DAVID system corresponds to a MLC leaf-pair to verify the leaf positioning accuracy during IMRT treatment and QA. In this study, verifications of IMRT plans of five head and neck (H&N) and five prostate patients treated in a Varian DHX linear accelerator with 80-leaf MLC were performed using DAVID system. Before DAVID-based dosimetry, Electronics Portal Imaging Device (EPID) and PTW 2D ARRAY dosimetry system were used for 2D verification of each plan. The measurements taken by DAVID system in the first day of the treatments were used as reference for the following measurements taken over the next four weeks. The deviations in leaf positioning were evaluated by "Total Deviation (TD)" parameter calculated by DAVID software. The delivered IMRT plans were originally prepared using dynamic MLC method. The same plans were subsequently calculated based on static MLC method with three different intensity levels of five (IL5), 10 (IL10) and 20 (IL20) in order to compare the performances of MLC leaf positioning repeatability for dynamic and static IMRT plans. The leaf positioning accuracy is also evaluated by analyzing DynaLog files based on error histograms and root mean square (RMS) errors of leaf pairs' positions. Moreover, a correlation analysis between simultaneously taken DAVID and EPID measurements and DynaLog file recordings was subsequently performed. In the analysis of DAVID outputs, the overall deviations of dynamic MLC-based IMRT calculated from the deviations of the four weeks were found as 0.55% ± 0.57% and 1.48% ± 0

  12. Dynamic path planning by using dual-layer fuzzy controllers%基于双层模糊控制器的动态路径规划

    Institute of Scientific and Technical Information of China (English)

    雷艳敏; 朱齐丹; 关秀丽; 冯志彬

    2011-01-01

    为解决没有通信情况下的多机器人系统在未知动态环境下的路径规划问题,设计了采用双层模糊控制器方法的危险度模糊控制器和速度模糊控制器.危险度模糊控制器充分考虑了运动障碍物的速度信息,把机器人同障碍物之间的碰撞可能性用基于碰撞时间因子和碰撞距离因子的碰撞危险度来表示,使之更适合于动态的环境.速度模糊控制器的输入充分考虑了目标方位角、障碍物方位角和碰撞危险度,采用行为思想设计模糊规则,规则中体现了奔向目标行为、躲避障碍物行为和沿着障碍物行走行为,使之更适合复杂的环境.仿真结果表明:该算法具有可行性、有效性和快速反应的能力.%To solve path planning problem of multi-robot systems with no communication in unknown dynamic environment, a dual-layer fuzzy controller was proposed. Danger degree fuzzy and velocity fuzzy controllers were designed in this controller. The velocity information of the moving obstacles was fully considered in the danger fuzzy controller, and it was more appropriate for dynamic environ- ment. Based on the time and distance factors of the collision, the danger degree of collision denoted the possibility that the robot collided with obstacles. The velocity fuzzy controller took full account of target azimuth, obstacle azimuth and danger degree of collision and designed fuzzy rules using behav- ior ideas. Fuzzy rules reflected the move-to-goal behavior, avoid-obstacle behavior and follow-obstacle behavior, and made velocity fuzzy controller suit to the complicated environment. Simulation results show that the proposed method is feasible and valid.

  13. Real-time dynamic MLC tracking for inversely optimized arc radiotherapy

    DEFF Research Database (Denmark)

    Falk, Marianne; af Rosenschöld, Per Munck; Keall, Paul;

    2010-01-01

    Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory....

  14. Real-time dynamic MLC tracking for inversely optimized arc radiotherapy

    DEFF Research Database (Denmark)

    Falk, Marianne; af Rosenschöld, Per Munck; Keall, Paul

    2010-01-01

    Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory.......Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory....

  15. Experimental investigation of a moving averaging algorithm for motion perpendicular to the leaf travel direction in dynamic MLC target tracking

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jai-Woong; Sawant, Amit; Suh, Yelin; Cho, Byung-Chul; Suh, Tae-Suk; Keall, Paul [Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul, Korea 131-700 and Research Institute of Biomedical Engineering, Catholic University of Korea, Seoul, 131-700 (Korea, Republic of); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States) and Department of Radiation Oncology, Asan Medical Center, Seoul, 138-736 (Korea, Republic of); Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul, 131-700 and Research Institute of Biomedical Engineering, Catholic University of Korea, Seoul, 131-700 (Korea, Republic of); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States) and Radiation Physics Laboratory, Sydney Medical School, University of Sydney, 2006 (Australia)

    2011-07-15

    Purpose: In dynamic multileaf collimator (MLC) motion tracking with complex intensity-modulated radiation therapy (IMRT) fields, target motion perpendicular to the MLC leaf travel direction can cause beam holds, which increase beam delivery time by up to a factor of 4. As a means to balance delivery efficiency and accuracy, a moving average algorithm was incorporated into a dynamic MLC motion tracking system (i.e., moving average tracking) to account for target motion perpendicular to the MLC leaf travel direction. The experimental investigation of the moving average algorithm compared with real-time tracking and no compensation beam delivery is described. Methods: The properties of the moving average algorithm were measured and compared with those of real-time tracking (dynamic MLC motion tracking accounting for both target motion parallel and perpendicular to the leaf travel direction) and no compensation beam delivery. The algorithm was investigated using a synthetic motion trace with a baseline drift and four patient-measured 3D tumor motion traces representing regular and irregular motions with varying baseline drifts. Each motion trace was reproduced by a moving platform. The delivery efficiency, geometric accuracy, and dosimetric accuracy were evaluated for conformal, step-and-shoot IMRT, and dynamic sliding window IMRT treatment plans using the synthetic and patient motion traces. The dosimetric accuracy was quantified via a {gamma}-test with a 3%/3 mm criterion. Results: The delivery efficiency ranged from 89 to 100% for moving average tracking, 26%-100% for real-time tracking, and 100% (by definition) for no compensation. The root-mean-square geometric error ranged from 3.2 to 4.0 mm for moving average tracking, 0.7-1.1 mm for real-time tracking, and 3.7-7.2 mm for no compensation. The percentage of dosimetric points failing the {gamma}-test ranged from 4 to 30% for moving average tracking, 0%-23% for real-time tracking, and 10%-47% for no compensation

  16. Technical Note: Motion-perturbation method applied to dosimetry of dynamic MLC target tracking—A proof-of-concept

    Energy Technology Data Exchange (ETDEWEB)

    Feygelman, Vladimir, E-mail: vladimir.feygelman@moffitt.org; Tonner, Brian; Hunt, Dylan; Zhang, Geoffrey; Moros, Eduardo [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)

    2015-11-15

    Purpose: Previous studies show that dose to a moving target can be estimated using 4D measurement-guided dose reconstruction based on a process called virtual motion simulation, or VMS. A potential extension of VMS is to estimate dose during dynamic multileaf collimator (MLC)-tracking treatments. The authors introduce a modified VMS method and quantify its performance as proof-of-concept for tracking applications. Methods: Direct measurements with a moving biplanar diode array were used to verify accuracy of the VMS dose estimates. A tracking environment for variably sized circular MLC apertures was simulated by sending preprogrammed control points to the MLC while simultaneously moving the accelerator treatment table. Sensitivity of the method to simulated tracking latency (0–700 ms) was also studied. Potential applicability of VMS to fast changing beam apertures was evaluated by modeling, based on the demonstrated dependence of the cumulative dose on the temporal dose gradient. Results: When physical and virtual latencies were matched, the agreement rates (2% global/2 mm gamma) between the VMS and the biplanar dosimeter were above 96%. When compared to their own reference dose (0 induced latency), the agreement rates for VMS and biplanar array track closely up to 200 ms of induced latency with 10% low-dose cutoff threshold and 300 ms with 50% cutoff. Time-resolved measurements suggest that even in the modulated beams, the error in the cumulative dose introduced by the 200 ms VMS time resolution is not likely to exceed 0.5%. Conclusions: Based on current results and prior benchmarks of VMS accuracy, the authors postulate that this approach should be applicable to any MLC-tracking treatments where leaf speeds do not exceed those of the current Varian accelerators.

  17. Technical Note: Motion-perturbation method applied to dosimetry of dynamic MLC target tracking--A proof-of-concept.

    Science.gov (United States)

    Feygelman, Vladimir; Tonner, Brian; Stambaugh, Cassandra; Hunt, Dylan; Zhang, Geoffrey; Moros, Eduardo; Nelms, Benjamin E

    2015-11-01

    Previous studies show that dose to a moving target can be estimated using 4D measurement-guided dose reconstruction based on a process called virtual motion simulation, or VMS. A potential extension of VMS is to estimate dose during dynamic multileaf collimator (MLC)-tracking treatments. The authors introduce a modified VMS method and quantify its performance as proof-of-concept for tracking applications. Direct measurements with a moving biplanar diode array were used to verify accuracy of the VMS dose estimates. A tracking environment for variably sized circular MLC apertures was simulated by sending preprogrammed control points to the MLC while simultaneously moving the accelerator treatment table. Sensitivity of the method to simulated tracking latency (0-700 ms) was also studied. Potential applicability of VMS to fast changing beam apertures was evaluated by modeling, based on the demonstrated dependence of the cumulative dose on the temporal dose gradient. When physical and virtual latencies were matched, the agreement rates (2% global/2 mm gamma) between the VMS and the biplanar dosimeter were above 96%. When compared to their own reference dose (0 induced latency), the agreement rates for VMS and biplanar array track closely up to 200 ms of induced latency with 10% low-dose cutoff threshold and 300 ms with 50% cutoff. Time-resolved measurements suggest that even in the modulated beams, the error in the cumulative dose introduced by the 200 ms VMS time resolution is not likely to exceed 0.5%. Based on current results and prior benchmarks of VMS accuracy, the authors postulate that this approach should be applicable to any MLC-tracking treatments where leaf speeds do not exceed those of the current Varian accelerators.

  18. Dynamic MLC tracking of moving targets with a single kV imager for 3D conformal and IMRT treatments

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, Per R. (Dept. of Oncology, Aarhus Univ. Hospital (Denmark)), E-mail: perpolse@rm.dk; Cho, Byungchul; Sawant, Amit; Ruan, Dan; Keall, Paul J. (Dept. of Radiation Oncology, Stanford Univ., Stanford (United States))

    2010-10-15

    Background. Tumor motion during radiotherapy is a major challenge for accurate dose delivery, in particular for hypofractionation and dose painting. The motion may be compensated by dynamic multileaf collimator (DMLC) tracking. Previous work has demonstrated that a single kV imager can accurately localize moving targets for DMLC tracking during rotational delivery, however this method has not been investigated for the static gantry geometry used for conformal and IMRT treatments. In this study we investigate the accuracy of single kV-imager based DMLC tracking for static-gantry delivery. Material and methods. A 5-field treatment plan with circular field shape and 200 MU per field was delivered in 20 s per field to a moving phantom with an embedded gold marker. Fluoroscopic kV images were acquired at 5 Hz perpendicular to the treatment beam axis during a 120 deg pre-treatment gantry rotation, during treatment delivery, and during inter-field gantry rotations. The three-dimensional marker position was estimated from the kV images and used for MLC adaptation. Experiments included 12 thoracic/abdominal tumor trajectories and five prostate trajectories selected from databases with 160 and 548 trajectories, respectively. The tracking error was determined as the mismatch between the marker position and the MLC aperture center in portal images. Simulations extended the study to all trajectories in the databases and to treatments with prolonged duration of 60 s per field. Results. In the experiments, the mean root-mean-square (rms) tracking error was 0.9 mm (perpendicular to MLC) and 1.1 mm (parallel to MLC) for thoracic/abdominal tumor trajectories and 0.6 mm (perpendicular) and 0.5 mm (parallel) for prostate trajectories. Simulations of these experiments agreed to within 0.1 mm. Simulations of all trajectories in the databases resulted in mean rms tracking errors of 0.6 mm (perpendicular) and 0.9 mm (parallel) for thorax/abdomen tumors and 0.4 mm (perpendicular) and 0

  19. Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul [Stanford University, Stanford, California 94394 (United States); Varian Medical Systems, Palo Alto, California 94304 (United States); Stanford University, Stanford, California 94394 (United States)

    2010-12-15

    Purpose: To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. Methods: A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Results: Failures modes with RPN{>=}125 were recommended to be tested monthly. Failure modes with RPN<125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software/hardware upgrades. System latency was determined to be {approx}193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%-3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was {approx}35 min, while that taken for comprehensive testing was {approx}3.5 h. Conclusions: FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures

  20. Real-time tracking of tumor motions and deformations along the leaf travel direction with the aid of a synchronized dynamic MLC leaf sequencer

    Energy Technology Data Exchange (ETDEWEB)

    Tacke, Martin; Nill, Simeon; Oelfke, Uwe [Deutsches Krebsforschungszentrum (DKFZ), Department of Medical Physics, Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2007-11-21

    Advanced radiotherapeutical techniques like intensity-modulated radiation therapy (IMRT) are based on an accurate knowledge of the location of the radiation target. An accurate dose delivery, therefore, requires a method to account for the inter- and intrafractional target motion and the target deformation occurring during the course of treatment. A method to compensate in real time for changes in the position and shape of the target is the use of a dynamic multileaf collimator (MLC) technique which can be devised to automatically arrange the treatment field according to real-time image information. So far, various approaches proposed for leaf sequencers have had to rely on a priori known target motion data and have aimed to optimize the overall treatment time. Since for a real-time dose delivery the target motion is not known a priori, the velocity range of the leading leaves is restricted by a safety margin to c x v{sub max} while the following leaves can travel with an additional maximum speed to compensate for the respective target movements. Another aspect to be considered is the tongue and groove effect. A uniform radiation field can only be achieved if the leaf movements are synchronized. The method presented in this note is the first to combine a synchronizing sequencer and real-time tracking with a dynamic MLC. The newly developed algorithm is capable of online optimizing the leaf velocities by minimizing the overall treatment time while at the same time it synchronizes the leaf trajectories in order to avoid the tongue and groove effect. The simultaneous synchronization is performed with the help of an online-calculated mid-time leaf trajectory which is common for all leaf pairs and which takes into account the real-time target motion and deformation information. (note)

  1. Block copolymer/homopolymer dual-layer hollow fiber membranes

    KAUST Repository

    Hilke, Roland

    2014-12-01

    We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene and the selective layer with isopores was formed by micelle assembly of polystyrene-. b-poly-4-vinyl pyridine. The dual layers had an excellent interfacial adhesion and pore interconnectivity. The dual membranes showed pH response behavior like single layer block copolymer membranes with a low flux for pH values less than 3, a fast increase between pH4 and pH6 and a constant high flux level for pH values above 7. The dry/wet spinning process was optimized to produce dual layer hollow fiber membranes with polystyrene internal support layer and a shell block copolymer selective layer.

  2. Virtual micro MLC commissioning.

    Science.gov (United States)

    Drever, Laura; Dickof, Peter

    2005-01-01

    The resolution of multileaf collimators (MLCs) is limited by their finite leaf width. A commercial package (HD-270) uses 3D couch translation and leaf adjustments to emulate smaller leaf widths. In this paper, we report on the commissioning of this feature using software testing, dial gauge measurements, and film dosimetry. We also identify a variety of limitations: software bugs and truncation artifacts, MLC leaf positioning uncertainties (random variations, systematic gantry dependence and backlash), and uncertainties in couch positioning. These reduce the capabilities of this implementation below that achievable theoretically.

  3. Basic Principles of MLC

    Directory of Open Access Journals (Sweden)

    Maria Rambla-Alegre

    2012-01-01

    Full Text Available Micellar liquid chromatography (MLC is an efficient alternative to conventional reversed-phase liquid chromatography with hydro-organic mobile phases. Almost three decades of experience have resulted in an increasing production of analytical applications. Current concern about the environment also reveals MLC as an interesting technique for “green” chemistry because it uses mobile phases containing 90% or more water. These micellar mobile phases have a low toxicity and are not producing hazardous wastes. The stationary phase is modified with an approximately constant amount of surfactant monomers, and the solubilising capability of the mobile phase is altered by the presence of micelles, giving rise to a great variety of interactions (hydrophobic, ionic, and steric with major implications in retention and selectivity. From its beginnings in 1980, the technique has evolved up to becoming in a real alternative in some instances (and a complement in others to classical RPLC with aqueous-organic mixtures, owing to its peculiar features and unique advantages. The addition of an organic solvent to the mobile phase was, however, soon suggested in order to enhance the low efficiencies and weak elution strength associated with the mobile phases that contained only micelles.

  4. Are simple IMRT beams more robust against MLC error? Exploring the impact of MLC errors on planar quality assurance and plan quality for different complexity beams.

    Science.gov (United States)

    Wang, Jiazhou; Jin, Xiance; Peng, Jiayuan; Xie, Jiang; Chen, Junchao; Hu, Weigang

    2016-01-01

    This study investigated the impact of beam complexities on planar quality assur-ance and plan quality robustness by introducing MLC errors in intensity-modulate radiation therapy. Forty patients' planar quality assurance (QA) plans were enrolled in this study, including 20 dynamic MLC (DMLC) IMRT plans and 20 static MLC (SMLC) IMRT plans. The total beam numbers were 150 and 160 for DMLC and SMLC, respectively. Six different magnitudes of MLC errors were introduced to these beams. Gamma pass rates were calculated by comparing error-free fluence and error-induced fluence. The plan quality variation was acquired by comparing PTV coverage. Eight complexity scores were calculated based on the beam flu-ence and the MLC sequence. The complexity scores include fractal dimension, monitor unit, modulation index, fluence map complexity, weighted average of field area, weighted average of field perimeter, and small aperture ratio (plan quality varia-tion. For planar QA, the most significant complexity index was fractal dimension for DMLC (p = -0.40) and weighted segment area for SMLC (p = 0.27) at low magnitude MLC error. For plan quality, the most significant complexity index was weighted segment perimeter for DMLC (p = 0.56) and weighted segment area for SMLC (p= 0.497) at low magnitude MLC error. The sensitivity of planar QA was weakly associated with the field complexity with low magnitude MLC error, but the plan quality robustness was associated with beam complexity. Plans with simple beams were more robust to MLC error.

  5. [Dosimetric comparison of non-small cell lung cancer treatment with multi fields dynamic-MLC IMRT].

    Science.gov (United States)

    Hao, Longying; Wang, Delin; Cao, Yujuan; Du, Fang; Cao, Feng; Liu, Chengwei

    2015-05-19

    We compared the dosimetric differences between the target and surrounding tissues/organs of the 5-field and 7,9-field (Hereinafter referred to as F5, F7, F9) treatment plan in non-small cell lung cancer (NSCLC) by the dynamic intensity-modulated radiotherapy (dIMRT), to provide reference for clinical application. Using Varian planning system (Eclipse 7.3), we randomly selected 30 cases of patients who received dIMRT to study, all patients were 5, 7, 9 fixed field dynamics intensity-modulated radiotherapy plans to meet the target prescription requirements (95% dose curve enveloping 100% of the PTV), by comparing dose-volume histogram DVH evaluation, and the maximum dose D(max), the minimum dose D(min), and the mean dose D(mean), and conformal index CI of PTV,organs at risk of spinal cord the maximum dose D(max), lung V(5), V(10), V(20), V(30), heart V(30) and esophageal V(50), V(60) of F5,F7 and F9 dIMRT plans,and compare the mu of the three treatment programs. The D(max), D(min) and D(mean) values of F5's PTV are (7 203 ± 128), (5 493 ± 331), (6 900 ± 138) cGy respectively; the D(max), D(min) and D(mean) values of F7's PTV are (7 304 ± 96), (5 526 ± 296), (6 976 ± 130) cGy respectively; and the D(max), D(min) and D(mean) values of F9's PTV are (7 356 ± 54), (5 578 ± 287), (7 019 ± 56) cGy respectively. The data shows that while we increased the numbers of fields, the isodose line surrounding the target area would also promote slightly. The conformity index CI of target became better with the increase of radiation fields. The whole lung V(5) and V(10) slightly became larger with increase of fields and the V(20) showed no significant difference in three models, V(30) of double lungs slightly decreased with the increase of fields. The above date was statistically meaningless (P > 0.05). With the increase of fields esophagus V(50) were reduced by 3% and 5% respectively, V(60) of the esophagus were reduced by 6% and 11%, the average dose reduced by 5% and 10

  6. Single arc volumetric-modulated arc therapy is sufficient for nasopharyngeal carcinoma: a dosimetric comparison with dual arc VMAT and dynamic MLC and step-and-shoot intensity-modulated radiotherapy

    OpenAIRE

    NING, ZHONG-HUA; Mu, Jin-Ming; Jin, Jian-Xue; Li, Xiao-Dong; LI, QI-LIN; GU, WEN-DONG; Huang, Jin; Han, Yang; PEI, HONG-LEI

    2013-01-01

    Background The performance of single arc VMAT (VMAT1) for nasopharyngeal carcinoma (NPC) on the Axesse linac has not been well described in previous studies. The purpose of this study is to assess the feasibility of VMAT1 for NPC by comparing the dosimetry, delivery efficiency, and accuracy with dual arc VMAT (VMAT2), dynamic MLC intensity-modulated radiotherapy (dIMRT), and step-and-shoot intensity-modulated radiotherapy (ssIMRT). Methods Twenty consecutive patients with non-metastatic NPC w...

  7. An experimental evaluation of the Agility MLC for motion-compensated VMAT delivery

    Science.gov (United States)

    Davies, G. A.; Clowes, P.; Bedford, J. L.; Evans, P. M.; Webb, S.; Poludniowski, G.

    2013-07-01

    An algorithm for dynamic multileaf-collimator (dMLC) tracking of a target performing a known a priori, rigid-body motion during volumetric modulated arc therapy (VMAT), has been experimentally validated and applied to investigate the potential of the Agility (Elekta AB, Stockholm, Sweden) multileaf-collimator (MLC) for use in motion-compensated VMAT delivery. For five VMAT patients, dosimetric measurements were performed using the Delta4 radiation detector (ScandiDos, Uppsala, Sweden) and the accuracy of dMLC tracking was evaluated using a gamma-analysis, with threshold levels of 3% for dose and 3 mm for distance-to-agreement. For a motion trajectory with components in two orthogonal directions, the mean gamma-analysis pass rate without tracking was found to be 58.0%, 59.0% and 60.9% and was increased to 89.1%, 88.3% and 93.1% with MLC tracking, for time periods of motion of 4 s, 6 s and 10 s respectively. Simulations were performed to compare the efficiency of the Agility MLC with the MLCi MLC when used for motion-compensated VMAT delivery for the same treatment plans and motion trajectories. Delivery time increases from a static-tumour to dMLC-tracking VMAT delivery were observed in the range 0%-20% for the Agility, and 0%-57% with the MLCi, indicating that the increased leaf speed of the Agility MLC is beneficial for MLC tracking during lung radiotherapy.

  8. Efficient dual layer interconnect coating for high temperature electrochemical devices

    DEFF Research Database (Denmark)

    Palcut, Marián; Mikkelsen, Lars; Neufeld, Kai

    2012-01-01

    Effects of novel dual layer coatings Co3O4/La0.85Sr0.15MnO3−δ on high temperature oxidation behaviour of candidate steels for interconnects are studied at 1123 K in flowing simulated ambient air (air + 1% H2O) and oxygen. Four alloys are investigated: Crofer 22 APU, Crofer 22 H, E-Brite and AL 29......-4C. The reaction kinetics is followed by measuring the mass increase of the samples over time. The oxide scale microstructure and chemical composition are investigated by scanning electron microscopy/energy dispersive spectroscopy. The kinetic data follow the parabolic rate law. It is found...... that the oxidation reaction is limited by outward Cr3+ diffusion in the chromia scale. The coating effectively reduces the oxidation rate. Reactions and cation inter-diffusion between the coating and the oxide scale are observed. Long term effects of these interactions are discussed and practical implications...

  9. Adaptive dual-layer super-twisting control and observation

    Science.gov (United States)

    Edwards, Christopher; Shtessel, Yuri

    2016-09-01

    In this paper, a super-twisting-like structure with adaptive gains is proposed. The structure is parameterised by two scalar gains, both of which adapt, and by an additional time-varying term. The magnitudes of the adaptive terms are allowed to both increase and decrease as appropriate so that they are as small as possible, in the sense that they do not unnecessarily over-bound the uncertainty, and yet are large enough to sustain a sliding motion. In the paper, a new time varying gain is incorporated into the traditional super-twisting architecture. The proposed adaption law has a dual-layer structure which is formally analyzed using Lyapunov techniques. The additional term has the effect of simplifying the stability analysis whilst guaranteeing the second-order sliding mode properties of the traditional super-twisting scheme.

  10. Dual layer hollow fiber sorbents: Concept, fabrication and characterization

    KAUST Repository

    Bhandari, Dhaval

    2013-02-01

    Hollow fiber sorbents are pseudo-monolithic separations materials created with fiber spinning technology using a polymer \\'binder\\', impregnated with high loadings of sorbent \\'fillers\\' [1]. To increase purified gas recovery during the sorption step and to ensure consistent sorption capacity over repeated cycles, a dense, thin polymer barrier layer on the fiber sorbents is needed to allow only thermal interactions between the sorbate loaded layer and the thermal regeneration fluid. This paper considers materials and methods to create delamination-free dual layer fiber sorbents, with a porous core and a barrier sheath layer formed using a simultaneous co-extrusion process. Low permeability polymers were screened for sheath layer creation, with the core layer comprising cellulose acetate polymer as binder and zeolite NaY as sorbent fillers. Appropriate core and sheath layer dope compositions were determined by the cloud-point method and rheology measurements. The morphology of the as-spun fibers was characterized in detail by SEM, EDX and gas permeation analysis. A simplified qualitative model is described to explain the observed fiber morphology. The effects of core, sheath spin dope and bore fluid compositions, spinning process parameters such as air-gap height, spin dope and coagulation bath temperatures, and elongation draw ratio are examined in detail. © 2012 Elsevier B.V. All rights reserved.

  11. Accomplishment of Blu-ray disc ROM by electron beam recording: dual layer with 50-GB capacity

    Science.gov (United States)

    Tsukuda, Masahiko; Ito, Eiichi; Tomiyama, Morio; Abe, Shinya; Ohno, Eiji; David, Stephane; Dubs, Martin; Bayliss, Chris; Dix, Colin; Ogilvie, Nick; Proffitt, Simon; Scott-Maxwell, David; Fantin, Bernard; Eisenhammer, Thomas

    2004-09-01

    A BD-ROM production-capable Electron Beam Recorder (EBR) has been developed, resulting from an optimization program conducted on a prior prototype. The key technical improvements are a comprehensive upgrade of the mechanical master driving system to reduce the track pitch deviations and the implementation of a dynamic focus system, including an axial run-out checker to obtain a uniform jitter. And the multi-pulse write strategy was adopted to control the pit shapes. The resulting masters show a typical radial track pitch variation comprised in the range +/-6.6nm across the entire recorded area. The corresponding push-pull signal deviation is found to be less than 18% on the whole disc and less than 14% in one revolution. The signal jitter of dual layered BD-ROM disc less than 6.1% on layer 0, and less than 6.7% on layer 1 with large enough push-pull amplitude through the whole radius. These results are fully compliant with the requirements for the dual layered BD-ROM disc of 50GB capacity.

  12. SU-C-BRB-02: Symmetric and Asymmetric MLC Based Lung Shielding and Dose Optimization During Translating Bed TBI

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, S; Kakakhel, MB [Pakistan Institute of Engineering & Applied Sciences (PIEAS), Islamabad (Pakistan); Ahmed, SBS; Hussain, A [Aga Khan University Hospital (AKUH), Karachi (Pakistan)

    2015-06-15

    Purpose: The primary aim was to introduce a dose optimization method for translating bed total body irradiation technique that ensures lung shielding dynamically. Symmetric and asymmetric dynamic MLC apertures were employed for this purpose. Methods: The MLC aperture sizes were defined based on the radiological depth values along the divergent ray lines passing through the individual CT slices. Based on these RD values, asymmetrically shaped MLC apertures were defined every 9 mm of the phantom in superior-inferior direction. Individual MLC files were created with MATLAB™ and were imported into Eclipse™ treatment planning system for dose calculations. Lungs can be shielded to an optimum level by reducing the MLC aperture width over the lungs. The process was repeated with symmetrically shaped apertures. Results: Dose-volume histogram (DVH) analysis shows that the asymmetric MLC based technique provides better dose coverage to the body and optimum shielding of the lungs compared to symmetrically shaped beam apertures. Midline dose homogeneity is within ±3% with asymmetric MLC apertures whereas it remains within ±4.5% with symmetric ones (except head region where it drops down to −7%). The substantial over and under dosage of ±5% at tissue interfaces has been reduced to ±2% with asymmetric MLC technique. Lungs dose can be reduced to any desired limit. In this experiment lungs dose was reduced to 80% of the prescribed dose, as was desired. Conclusion: The novel asymmetric MLC based technique assures optimum shielding of OARs (e.g. lungs) and better 3-D dose homogeneity and body-dose coverage in comparison with the symmetric MLC aperture optimization. The authors acknowledge the financial and infrastructural support provided by Pakistan Institute of Engineering & Applied Sciences (PIEAS), Islamabad and Aga Khan University Hospital (AKUH), Karachi during the course of this research project. Authors have no conflict of interest with any national / international

  13. Dual layer hollow fiber sorbents for trace H2S removal from gas streams

    KAUST Repository

    Bhandari, Dhaval A.

    2013-05-01

    Hollow fiber sorbents are pseudo monolithic materials with potential use in various adsorption based applications. Dual layer hollow fiber sorbents have the potential to allow thermal regeneration without direct contact of the regeneration fluid with the sorbent particles. This paper considers the application of dual layer hollow fiber sorbents for a case involving trace amounts of H2S removal from a simulated gas stream and offers a comparison with single layer hollow fiber sorbents. The effect of spin dope composition and core layer zeolite loading on the gas flux, H2S transient sorption capacity and pore structure are also studied. This work can be used as a guide to develop and optimize dual layer hollow fiber sorbent properties beyond the specific example considered here. © 2013 Elsevier Ltd.

  14. A numerical framework for the mechanical analysis of dual-layer stents in intracranial aneurysm treatment.

    Science.gov (United States)

    Alherz, Ali I; Tanweer, Omar; Flamini, Vittoria

    2016-08-16

    Dual-layer stents and multi-layer stents represent a new paradigm in endovascular interventions. Multi-layer stents match different stent designs in order to offer auxiliary functions. For example, dual-layer stents used in the endovascular treatment of intracranial aneurysms, like the FRED(TM) (MicroVention, CA) stent, combine a densely braided inner metallic mesh with a loosely braided outer mesh. The inner layer is designed to divert blood flow, whereas the outer one ensures microvessels branching out of the main artery remain patent. In this work, the implemented finite element (FE) analysis identifies the key aspects of dual-stent mechanics. In particular, dual-layer stents used in the treatment of intracranial aneurysms require the ability to conform to very narrow passages in their closed configuration, while at the same time they have to provide support and stability once deployed. This study developed a numerical framework for the analysis of dual-layer stents for endovascular intracranial aneurysm treatment. Our results were validated against analytical methods. For the designs considered, we observed that foreshortening was in average 37.5%±2.5%, and that doubling the number of wires in the outer stent increased bending moment by 23%, while halving the number of wires of the inner stent reduced von Mises stress by 2.3%. This framework can be extended to the design optimization of multi-layer stents used in other endovascular treatments.

  15. Motion management during IMAT treatment of mobile lung tumors-A comparison of MLC tracking and gated delivery

    DEFF Research Database (Denmark)

    Falk, Marianne; Pommer, Tobias; Keall, Paul

    2014-01-01

    Purpose:To compare real-time dynamic multileaf collimator (MLC) tracking, respiratory amplitude and phase gating, and no compensation for intrafraction motion management during intensity modulated arc therapy (IMAT). Methods: Motion management with MLC tracking and gating was evaluated for four l...... longer delivery time. In a clinical setting, the optical monitoring of the patients breathing would have to be correlated to the internal movements of the tumor...

  16. An eigenvalue study of the MLC circuit

    DEFF Research Database (Denmark)

    Lindberg, Erik; Murali, K.

    1998-01-01

    The MLC (Murali-Lakshmanan-Chua) circuit is the simplest non-autonomous chaotic circuit. Insight in the behaviour of the circuit is obtained by means of a study of the eigenvalues of the linearized Jacobian of the nonlinear differential equations. The trajectories of the eigenvalues as functions...

  17. Fault Analysis and Treatment of MLC VARIAN in Dynamic Intensity Modulated Radiotherapy%动态调强放疗中VARIAN MLC的故障分析处理

    Institute of Scientific and Technical Information of China (English)

    李亮; 陈勇; 徐钰梅; 范雪梅

    2015-01-01

    ObjectiveTo analyze the common faults of 23EX VARIAN linear accelerator MLC and provide the experience for the maintenance of the accelerator. Methods To observe the in the treatment process of the machine failure, observation 4DTC treatment control computer, through the MLC test software to check the fault information to find fault, analysis of the causes of failure, to solve the problem.ResultsAfter scientific analysis, symptomatic treatment, the effective elimination of failure, the system returned to normal operation, maintenance and maintenance for the machine has accumulated experience.Conclusion The use of MLC is high and easy to malfunction. To explore a set of effective method to repair the MLC fault can improve the machine performance, to ensure that the effect of the intensity of radiation therapy.%目的:分析VARIAN 23EX直线加速器MLC常见故障,为加速器维修提供经验交流。方法针对治疗过程中出现机器故障,观察4DTC治疗控制电脑,通过MLC自检软件查看报错信息找到故障所在,分析故障原因,解决故障。结果经过科学分析,对症处理,故障有效排除,系统恢复正常运转,为机器维护维修积累了经验。结论 MLC使用频率高,易发故障。探究一套有效的检修方法及时排除MLC故障可提高机器性能,确保调强放射治疗效果。

  18. The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators (MLC)

    Institute of Scientific and Technical Information of China (English)

    LI Zhaobin; XIONG Fei; HUANG Guofeng; CAO Zheng; JIANG Ruiyao; FU Shen

    2007-01-01

    Linear accelerators equipped with multileaf collimators (MLC) are becoming more common and are widely used in the intensity-modulated radiotherapy (IMRT). There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance (QA) and quality control (QC). This paper is aimed to investigate the role of AGFA high-energy CR (Computed Radiography) in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.

  19. Dual-layered Blu-ray disc ROM fabricated by all-spin method

    Science.gov (United States)

    Hisada, Kazuya; Hayashi, Kazuhiro; Nishikiori, Keiji; Ohno, Eiji

    2004-09-01

    We developed fabrication process using "all spin method" for dual layered Blu-ray Disc ROM. All of the light transmitting layer consisting of a space layer, a cover layer and a hard coat are formed by spin-coating method. Regarding the cover layer, the cycle time is less than 15 seconds and the efficiency of usage of the UV curable resin is 59%. The fabricated disc has sufficient property of thickness variation of the light transmitting layer for all disc area. The disc also has good performances of tilt characteristics including tilt transition caused by environmental sudden change due to the moisture control layer although the substrate material is conventional poly-carbonate. We confirmed the feasibility of the dual layered BD-ROM by "all spin method" and it shows the possibility of low cost BD-ROM disc.

  20. Retraction pattern of delaminated rotator cuff tears: dual-layer rotator cuff repair

    OpenAIRE

    Cha, Sang-Won; Lee, Choon-Key; Sugaya, Hiroyuki; Kim, Taegyun; Lee, Su-Chan

    2016-01-01

    Background There has been no report to date regarding retraction patterns of delaminated rotator cuff tears. The purpose of this study was to evaluate the incidence and tearing patterns of delamination and repair integrity after the dual-layer repair of delaminated cuff tears. Methods/design A consecutive series of 64 patients with posterosuperior rotator cuff tears underwent arthroscopic rotator cuff repair from August 2011 to September 2012. Among the patients, 53 who received either dual-l...

  1. Predicting Anticancer Drug Responses Using a Dual-Layer Integrated Cell Line-Drug Network Model.

    Directory of Open Access Journals (Sweden)

    Naiqian Zhang

    Full Text Available The ability to predict the response of a cancer patient to a therapeutic agent is a major goal in modern oncology that should ultimately lead to personalized treatment. Existing approaches to predicting drug sensitivity rely primarily on profiling of cancer cell line panels that have been treated with different drugs and selecting genomic or functional genomic features to regress or classify the drug response. Here, we propose a dual-layer integrated cell line-drug network model, which uses both cell line similarity network (CSN data and drug similarity network (DSN data to predict the drug response of a given cell line using a weighted model. Using the Cancer Cell Line Encyclopedia (CCLE and Cancer Genome Project (CGP studies as benchmark datasets, our single-layer model with CSN or DSN and only a single parameter achieved a prediction performance comparable to the previously generated elastic net model. When using the dual-layer model integrating both CSN and DSN, our predicted response reached a 0.6 Pearson correlation coefficient with observed responses for most drugs, which is significantly better than the previous results using the elastic net model. We have also applied the dual-layer cell line-drug integrated network model to fill in the missing drug response values in the CGP dataset. Even though the dual-layer integrated cell line-drug network model does not specifically model mutation information, it correctly predicted that BRAF mutant cell lines would be more sensitive than BRAF wild-type cell lines to three MEK1/2 inhibitors tested.

  2. Single arc volumetric-modulated arc therapy is sufficient for nasopharyngeal carcinoma: a dosimetric comparison with dual arc VMAT and dynamic MLC and step-and-shoot intensity-modulated radiotherapy

    Science.gov (United States)

    2013-01-01

    Background The performance of single arc VMAT (VMAT1) for nasopharyngeal carcinoma (NPC) on the Axesse linac has not been well described in previous studies. The purpose of this study is to assess the feasibility of VMAT1 for NPC by comparing the dosimetry, delivery efficiency, and accuracy with dual arc VMAT (VMAT2), dynamic MLC intensity-modulated radiotherapy (dIMRT), and step-and-shoot intensity-modulated radiotherapy (ssIMRT). Methods Twenty consecutive patients with non-metastatic NPC were selected to be planned with VMAT1, VMAT2, dIMRT and ssIMRT using Monaco 3.2 TPS on the Axesse™ linear accelerator. Three planning target volumes (PTVs), contoured as high risk, moderate risk and low risk regions, were set to receive median absorbed-dose (D50%) of 72.6 Gy, 63.6 Gy and 54 Gy, respectively. The Homogeneity Index (HI), Conformity Index (CI), Dose Volume Histograms (DVHs), delivery efficiency and accuracy were all evaluated. Results Mean HI of PTV72.6 is better with VMAT1(0.07) and VMAT2(0.07) than dIMRT(0.09) and ssIMRT(0.09). Mean HI of PTV63.6 is better with VMAT1(0.21) and VMAT2(0.21) than dIMRT and ssIMRT. Mean CI of PTV72.6 is also better with VMAT1(0.57) and VMAT2(0.57) than dIMRT(0.49) and ssIMRT(0.5). Mean CI of PTV63.6 is better with VMAT1(0.76) and VMAT2(0.76) than dIMRT(0.73) and ssIMRT(0.73). VMAT had significantly improved homogeneity and conformity compared with IMRT. There was no significant difference between VMAT1 and VMAT2 in PTV coverage. Dose to normal tissues was acceptable for all four plan groups. VMAT1 and VMAT2 showed no significant difference in normal tissue sparring, whereas the mean dose of the parotid gland of dIMRT was significantly reduced compared to VMAT1 and VMAT2. The mean delivery time for VMAT1, VMAT2, dIMRT and ssIMRT was 2.7 min, 3.9 min, 5.7 min and 14.1 min, respectively. VMAT1 reduced the average delivery time by 29.8%, 51.1% and 80.8% compared with VMAT2, dIMRT and ssIMRT, respectively. VMAT and IMRT could all be

  3. SU-E-T-479: IMRT Plan Recalculation in Patient Based On Dynalog Data and the Effect of a Single Failing MLC Motor

    Energy Technology Data Exchange (ETDEWEB)

    Morcos, M [Vantage Oncology, San Bernardino, CA (United States); Mitrou, E [Centre Hospitalier de l’Universite de Montreal, Montreal, QC (Canada)

    2015-06-15

    Purpose: Using Linac dynamic logs (Dynalogs) we evaluate the impact of a single failing MLC motor on the deliverability of an IMRT plan by assessing the recalculated dose volume histograms (DVHs) taking the delivered MLC positions and beam hold-offs into consideration. Methods: This is a retrospective study based on a deteriorating MLC motor (leaf 36B) which was observed to be failing via Dynalog analysis. To investigate further, Eclipse-importable MLC files were generated from Dynalogs to recalculate the actual delivered dose and to assess the clinical impact through DVHs. All deliveries were performed on a Varian 21EX linear accelerator equipped with Millennium-120 MLC. The analysis of Dynalog files and subsequent conversion to Eclipse-importable MLC files were all performed by in-house programming in Python. Effects on plan DVH are presented in the following section on a particular brain-IMRT plan which was delivered with a failing MLC motor which was then replaced. Results: Global max dose increased by 13.5%, max dose to the brainstem PRV increased by 8.2%, max dose to the optic chiasm increased by 7.6%, max dose to optic nerve increased by 8.8% and the mean dose to the PTV increased by 7.9% when comparing the original plan to the fraction with the failing MLC motor. The reason the dose increased was due to the failure being on the B-bank which is the lagging side on a sliding window delivery, therefore any failures on this side will cause an over-irradiation as the B-bank leaves struggles to keep the window from growing. Conclusion: Our findings suggest that a single failing MLC motor may jeopardize the entire delivery. This may be due to the bad MLC motor drawing too much current causing all MLCs on the same bank to underperform. This hypothesis will be investigated in a future study.

  4. Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance.

    Science.gov (United States)

    Wang, Peng; Teoh, May May; Chung, Tai-Shung

    2011-11-01

    A new strategy to enhance the desalination performance of polyvinylidene fluoride (PVDF) hollow fiber membrane for membrane distillation (MD) via architecture of morphological characteristics is explored in this study. It is proposed that a dual-layer hollow fiber consisting of a fully finger-like macrovoid inner-layer and a sponge-like outer-layer may effectively enhance the permeation flux while maintaining the wetting resistance. Dual-layer fibers with the proposed morphology have been fabricated by the dry-jet wet spinning process via careful choice of dopes composition and coagulation conditions. In addition to high energy efficiency (EE) of 94%, a superior flux of 98.6 L m(-2) h(-1) is obtained during the direct contact membrane distillation (DCMD) desalination experiments. Moreover, the liquid entry pressure (LEP) and long-term DCMD performance test show high wetting resistance and long-term stability. Mathematical modeling has been conducted to investigate the membrane mass transfer properties in terms of temperature profile and apparent diffusivity of the membranes. It is concluded that the enhancement in permeation flux arises from the coupling effect of two mechanisms; namely, a higher driving force and a lower mass transfer resistance, while the later is the major contribution. This work provides an insight on MD fundamentals and strategy to tailor making ideal membranes for DCMD application in desalination industry. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Behavior of W-SiC/SiC dual layer tiles under LHD plasma exposure

    Science.gov (United States)

    Mohrez, Waleed A.; Kishimoto, Hirotatsu; Kohno, Yutaka; Hirotaki, S.; Kohyama, Akira

    2013-11-01

    Towards the early realization of fusion power reactors, high performance first wall and plasma facing components (PFCs) are essentially required. As one of the biggest challenges for this, high heat flux component (HHFC) design and R & D has been emphasized. This report provides the high performance HHFC materials R & D status and the first plasma exposure test result from large helical device (LHD). W-SiC/SiC dual layer tiles (hereafter, W-SiC/SiC) were developed by applied NITE process. This is the realistic concept of tungsten armor with ceramic composite substrates for fusion power reactors. The dual layer tiles were fabricated and tested their survival under the LHD divertor plasma exposure (Nominally 10 MW/m2 maximum heat load for 6 s operation cycle). The microstructure evolution, including crack and pore formation, was analyzed, besides the behavior of bonding layer between tungsten and SiC/SiC was evaluated by C-scanning images of ultrasonic method and Electron probe Micro-analyzer (EPMA). Thermal analysis was conducted by finite element method, where ANSYS code release 13.0 was used.

  6. Behavior of W–SiC/SiC dual layer tiles under LHD plasma exposure

    Energy Technology Data Exchange (ETDEWEB)

    Mohrez, Waleed A., E-mail: dalywaleed@hotmail.com [Graduate School of Chemical and Materials Engineering, Muroran Institute of Technology, Muroran, Hokkaido 050-8585 (Japan); The nuclear materials authority, Cairo, Maadi (Egypt); Kishimoto, Hirotatsu; Kohno, Yutaka; Hirotaki, S. [College of Design and Manufacturing Technology, Muroran Institute of Technology, Muroran, Hokkaido 050-8585 (Japan); Kohyama, Akira [Organization of Advanced Sustainability Initiative for Energy System/Material (OASIS), Muroran Institute of Technology, Muroran, Hokkaido 050-8585 (Japan)

    2013-11-15

    Towards the early realization of fusion power reactors, high performance first wall and plasma facing components (PFCs) are essentially required. As one of the biggest challenges for this, high heat flux component (HHFC) design and R and D has been emphasized. This report provides the high performance HHFC materials R and D status and the first plasma exposure test result from large helical device (LHD). W–SiC/SiC dual layer tiles (hereafter, W–SiC/SiC) were developed by applied NITE process. This is the realistic concept of tungsten armor with ceramic composite substrates for fusion power reactors. The dual layer tiles were fabricated and tested their survival under the LHD divertor plasma exposure (Nominally 10 MW/m{sup 2} maximum heat load for 6 s operation cycle). The microstructure evolution, including crack and pore formation, was analyzed, besides the behavior of bonding layer between tungsten and SiC/SiC was evaluated by C-scanning images of ultrasonic method and Electron probe Micro-analyzer (EPMA). Thermal analysis was conducted by finite element method, where ANSYS code release 13.0 was used.

  7. A dual-layer transducer array for 3-D rectilinear imaging.

    Science.gov (United States)

    Yen, Jesse T; Seo, Chi Hyung; Awad, Samer I; Jeong, Jong S

    2009-01-01

    Very large element counts (16,000-65,000) are required for 2-D arrays for 3-D rectilinear imaging. The difficulties in fabricating and interconnecting 2-D arrays with a large number of elements (>5,000) have limited the development of suitable transducers for 3-D rectilinear imaging. In this paper, we propose an alternative solution to this problem by using a dual-layer transducer array design. This design consists of 2 perpendicular 1-D arrays for clinical 3-D imaging of targets near the transducer. These targets include the breast, carotid artery, and musculoskeletal system. This transducer design reduces the fabrication complexity and the channel count, making 3-D rectilinear imaging more realizable. With this design, an effective N x N 2-D array can be developed using only N transmitters and N receivers. This benefit becomes very significant when N becomes greater than 128, for example. To demonstrate feasibility, we constructed a 4 x 4 cm prototype dual-layer array. The transmit array uses diced PZT-5H elements, and the receive array is a single sheet of undiced P[VDF-TrFE] copolymer. The receive elements are defined by the copper traces on the flexible interconnect circuit. The measured -6 dB fractional bandwidth was 80% with a center frequency of 4.8 MHz. At 5 MHz, the nearest neighbor crosstalk of the PZT array and PVDF array was -30.4 +/- 3.1 dB and -28.8 +/- 3.7 dB, respectively. This dual-layer transducer was interfaced with an Ultrasonix Sonix RP system, and a synthetic aperture 3-D data set was acquired. We then performed offline 3-D beamforming to obtain volumes of nylon wire targets. The theoretical lateral beamwidth was 0.52 mm compared with measured beamwidths of 0.65 mm and 0.67 mm in azimuth and elevation, respectively. Then, 3-D images of an 8 mm diameter anechoic cyst phantom were also acquired.

  8. Deposition of dual-layer coating on Ti6Al4V

    Science.gov (United States)

    Hussain Din, Sajad; Shah, M. A.; Sheikh, N. A.

    2017-03-01

    Dual-layer diamond coatings were deposited on titanium alloy (Ti6Al4V) using a hot filament chemical vapour deposition technique with the anticipation of studying the structural and morphology properties of the alloy. The coated diamond films were characterized using scanning electron microscope, x-ray diffraction (XRD), and Raman spectroscopy. The XRD studies reveal that the deposited films are highly crystalline in nature, whereas morphological studies show that the films have a cauliflower structure. XRD analysis was used to calculate the structural parameters of the Ti6Al4V and CVD-coated Ti6Al4V. Raman spectroscopy was used to determine the nature and magnitude of the residual stress of the coatings.

  9. Dual-layered-coated mechanically-durable superomniphobic surfaces with anti-smudge properties.

    Science.gov (United States)

    Muthiah, Palanikkumaran; Bhushan, Bharat; Yun, Kyungsung; Kondo, Hirofumi

    2013-11-01

    Bio-inspired surfaces that exhibit high contact angle and low contact angle hysteresis for various liquids and demonstrate mechanical durability and anti-smudge properties are of interest for various applications. The fabrication of such surfaces has often involved complex or expensive processes, required techniques that may not be suitable for various substrates and particles, may require surface post-treatment, or may lack durability. Dual layered coatings of roughness-induced superomniphobic surfaces that demonstrate good mechanical durability were fabricated on glass substrates using hydrophobic SiO2 nanoparticles and low surface energy fluorobinders using dip coating and spray coating techniques. The particle-to-binder ratio was optimized for contact angles of interest. The mechanical durability of these coatings was examined under mechanical rubbing action. The anti-smudge properties were examined by wiping an artificially contaminated coating using oil-impregnated microfiber cloth.

  10. Security protection of DICOM medical images using dual-layer reversible watermarking with tamper detection capability.

    Science.gov (United States)

    Tan, Chun Kiat; Ng, Jason Changwei; Xu, Xiaotian; Poh, Chueh Loo; Guan, Yong Liang; Sheah, Kenneth

    2011-06-01

    Teleradiology applications and universal availability of patient records using web-based technology are rapidly gaining importance. Consequently, digital medical image security has become an important issue when images and their pertinent patient information are transmitted across public networks, such as the Internet. Health mandates such as the Health Insurance Portability and Accountability Act require healthcare providers to adhere to security measures in order to protect sensitive patient information. This paper presents a fully reversible, dual-layer watermarking scheme with tamper detection capability for medical images. The scheme utilizes concepts of public-key cryptography and reversible data-hiding technique. The scheme was tested using medical images in DICOM format. The results show that the scheme is able to ensure image authenticity and integrity, and to locate tampered regions in the images.

  11. Motion management during IMAT treatment of mobile lung tumors—A comparison of MLC tracking and gated delivery

    Science.gov (United States)

    Falk, Marianne; Pommer, Tobias; Keall, Paul; Korreman, Stine; Persson, Gitte; Poulsen, Per; Munck af Rosenschöld, Per

    2014-01-01

    Purpose: To compare real-time dynamic multileaf collimator (MLC) tracking, respiratory amplitude and phase gating, and no compensation for intrafraction motion management during intensity modulated arc therapy (IMAT). Methods: Motion management with MLC tracking and gating was evaluated for four lung cancer patients. The IMAT plans were delivered to a dosimetric phantom mounted onto a 3D motion phantom performing patient-specific lung tumor motion. The MLC tracking system was guided by an optical system that used stereoscopic infrared (IR) cameras and five spherical reflecting markers attached to the dosimetric phantom. The gated delivery used a duty cycle of 35% and collected position data using an IR camera and two reflecting markers attached to a marker block. Results: The average gamma index failure rate (2% and 2 mm criteria) was delivery time. In a clinical setting, the optical monitoring of the patients breathing would have to be correlated to the internal movements of the tumor. PMID:25281946

  12. 7.5 MHz dual-layer transducer array for 3-D rectilinear imaging.

    Science.gov (United States)

    Chen, Yuling; Nguyen, Man; Yen, Jesse T

    2011-07-01

    The difficulties associated with fabrication and interconnection have limited the development of 2-D ultrasound transducer arrays with a large number ofelements (>5000). In previous work, we described a 5 MHz center frequency PZT-P[VDF-TrFE] dual-layer transducer that used two perpendicular 1-D arrays for 3-D rectilinear imaging. This design substantially reduces the channel count as well as fabrication complexity, which makes 3-D imaging more realizable. Higher frequencies (>5 MHz) are more commonly used in clinical applications or imaging targets near transducers, such as the breast, carotid and musculoskeletal tissue. In this paper, we present a 7.5 MHz dual-layer transducer array for 3-D rectilinear imaging. A modified acoustic stack model was designed and fabricated. PZT elements were sub-diced to eliminate lateral coupling. This sub-dicing process made the PZT into a 2-2 composite material, which could help improve transducer sensitivity and bandwidth. Full synthetic-aperture 3-D data sets were acquired by interfacing the transducer with a Verasonics data-acquisition system (VDAS). Offline 3-D beamforming was then performed to obtain volumes of a multiwire phantom and a cyst phantom. The generalized coherence factor (GCF) was applied to improve the contrast of cyst images. The measured -6 dB fractional bandwidth of the transducer was 71% with a center frequency of 7.5 MHz. The measured lateral beamwidths were 0.521 mm and 0.482 mm in azimuth and elevation, respectively, compared with a simulated beamwidth of 0.43 mm.

  13. Pressure retarded osmosis dual-layer hollow fiber membranes developed by co-casting method and ammonium persulfate (APS) treatment

    KAUST Repository

    Fu, Fengjiang

    2014-11-01

    Delamination and low water permeability are two issues limiting the applications of dual-layer hollow fiber membranes in the pressure retarded osmosis (PRO) process. In this work, we first developed a universal co-casting method that is able to co-cast highly viscous dope solutions to form homogeneous dual-layer flat sheet membranes. By employing this method prior to the tedious dual-layer hollow fiber spinning process, both time and material consumptions are significantly saved. The addition of polyvinylpyrrolidone (PVP) is found to eliminate delamination at the sacrifice of water flux. A new post-treatment method that involves flowing ammonium persulfate (APS) solution and DI water counter-currently is potentially to remove the PVP molecules entrapped in the substrate while keeps the integrity of the interface. As the APS concentration increases, the water flux in the PRO process is increased while the salt leakage is slightly decreased. With the optimized APS concentration of 5wt%, the post-treated membrane shows a maximum power density of 5.10W/m2 at a hydraulic pressure of 15.0bar when 1M NaCl and 10mM NaCl were used as the draw and feed solutions, respectively. To the extent of our knowledge, this is the best phase inversion dual-layer hollow fiber membrane with an outer selective layer for osmotic power generation. © 2014 Elsevier B.V.

  14. Influence of Process Temperatures on Blister Creation in Micro Film Insert Molding of a Dual Layer Membrane

    DEFF Research Database (Denmark)

    Wöhner, Timo; R. Whiteside, Ben; Tosello, Guido

    2016-01-01

    In this work the suitability of a dual layer membrane, consisting of a non-woven Polypropylene (PP) support and a membrane layer made out of Polyethylene Terephthalate (PET) for Micro Film Insert Molding (μFIM) was investigated. The emergence of blisters at the surface of the PET-membrane layer...

  15. SU-E-T-01: 2-D Characterization of DLG Among All MLC Leaf Pairs

    Energy Technology Data Exchange (ETDEWEB)

    Kumaraswamy, L; Xu, Z; Podgorsak, M [Roswell Park Cancer Institute, Buffalo, NY (United States); Schmitt, J [RadAmerica, LLC--MedStar Health, Baltimore, MD (United States); Bailey, D [Northside Hospital, Atlanta, GA (United States)

    2014-06-01

    Purpose: The aim of this study is to evaluate the variation of dosimetric leaf-gap (DLG) along the travel path of each MLC leaf pair. This study evaluates whether the spatial variations in DLG could cause dose differences between TPS-calculated and measured dose. Methods: The 6MV DLG values were measured for all leaf pairs in the direction of leaf motion using a 2-D diode array and 0.6cc ion chamber. These measurements were performed on two Varian Linacs, employing the Millennium 120-leaf MLC and a 2-D-DLG variation map was created via in-house software. Several test plans were created with sweeping MLC fields using constant gaps from 2mm to 10mm and corrected for 2-D variation utilizing in-house software. Measurements were performed utilizing the MapCHECK at 5.0cm depth for plans with and without the 2-D DLG correction and compared to the TPS calculated dose via gamma analysis (3%/3mm). Results: The measured DLGs for the middle 40 MLC leaf pairs (0.5cm width) were very similar along the central superior-inferior axis, with maximum variation of 0.2mm. The outer 20 MLC leaf pairs (1.0cm width) have DLG values from 0.32mm (mean) to 0.65mm (maximum) lower than the central leaf-pair, depending on off-axis distance. Gamma pass rates for the 2mm, 4mm, and 6mm sweep plans increased by 23.2%, 28.7%, and 26.0% respectively using the 2-D-DLG correction. The most improved dose points occur in areas modulated by the 1.0cm leaf-pairs. The gamma pass rate for the 10mm sweep plan increased by only 7.7%, indicating that the 2D variation becomes less significant for dynamic plans with larger MLC gaps. Conclusion: Fluences residing significantly off-axis with narrow sweeping gaps may exhibit significant variations from planned dose due to large differences between the true DLG exhibited by the 1.0cm leaf-pairs versus the constant DLG value utilized by the TPS for dose calculation.

  16. Dual Heat Pulse, Dual Layer Thermal Protection System Sizing Analysis and Trade Studies for Human Mars Entry Descent and Landing

    Science.gov (United States)

    McGuire, Mary Kathleen

    2011-01-01

    NASA has been recently updating design reference missions for the human exploration of Mars and evaluating the technology investments required to do so. The first of these started in January 2007 and developed the Mars Design Reference Architecture 5.0 (DRA5). As part of DRA5, Thermal Protection System (TPS) sizing analysis was performed on a mid L/D rigid aeroshell undergoing a dual heat pulse (aerocapture and atmospheric entry) trajectory. The DRA5 TPS subteam determined that using traditional monolithic ablator systems would be mass expensive. They proposed a new dual-layer TPS concept utilizing an ablator atop a low thermal conductivity insulative substrate to address the issue. Using existing thermal response models for an ablator and insulative tile, preliminary hand analysis of the dual layer concept at a few key heating points indicated that the concept showed potential to reduce TPS masses and warranted further study. In FY09, the followon Entry, Descent and Landing Systems Analysis (EDL-SA) project continued by focusing on Exploration-class cargo or crewed missions requiring 10 to 50 metric tons of landed payload. The TPS subteam advanced the preliminary dual-layer TPS analysis by developing a new process and updated TPS sizing code to rapidly evaluate mass-optimized, full body sizing for a dual layer TPS that is capable of dual heat pulse performance. This paper describes the process and presents the results of the EDL-SA FY09 dual-layer TPS analyses on the rigid mid L/D aeroshell. Additionally, several trade studies were conducted with the sizing code to evaluate the impact of various design factors, assumptions and margins.

  17. Real-time tumor tracking: Automatic compensation of target motion using the Siemens 160 MLC

    Energy Technology Data Exchange (ETDEWEB)

    Tacke, Martin B.; Nill, Simeon; Krauss, Andreas; Oelfke, Uwe [Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg (Germany)

    2010-02-15

    Purpose: Advanced high quality radiation therapy techniques such as IMRT require an accurate delivery of precisely modulated radiation fields to the target volume. Interfractional and intrafractional motion of the patient's anatomy, however, may considerably deteriorate the accuracy of the delivered dose to the planned dose distributions. In order to compensate for these potential errors, a dynamic real-time capable MLC control system was designed. Methods: The newly developed adaptive MLC control system contains specialized algorithms which are capable of continuous optimization and correction of the aperture of the MLC according to the motion of the target volume during the dose delivery. The algorithms calculate the new leaf positions based on target information provided online to the system. The algorithms were implemented in a dynamic target tracking control system designed for a Siemens 160 MLC. To assess the quality of the new target tracking system in terms of dosimetric accuracy, experiments with various types of motion patterns using different phantom setups were performed. The phantoms were equipped with radiochromic films placed between solid water slabs. Dosimetric results of exemplary deliveries to moving targets with and without dynamic MLC tracking applied were compared in terms of the gamma criterion to the reference dose delivered to a static phantom. Results: Our measurements indicated that dose errors for clinically relevant two-dimensional target motion can be compensated by the new control system during the dose delivery of open fields. For a clinical IMRT dose distribution, the gamma success rate was increased from 19% to 77% using the new tracking system. Similar improvements were achieved for the delivery of a complete IMRT treatment fraction to a moving lung phantom. However, dosimetric accuracy was limited by the system's latency of 400 ms and the finite leaf width of 5 mm in the isocenter plane. Conclusions: Different

  18. Mathematical Modeling of Dual Layer Shell Type Recuperation System for Biogas Dehumidification

    Science.gov (United States)

    Gendelis, S.; Timuhins, A.; Laizans, A.; Bandeniece, L.

    2015-12-01

    The main aim of the current paper is to create a mathematical model for dual layer shell type recuperation system, which allows reducing the heat losses from the biomass digester and water amount in the biogas without any additional mechanical or chemical components. The idea of this system is to reduce the temperature of the outflowing gas by creating two-layered counter-flow heat exchanger around the walls of biogas digester, thus increasing a thermal resistance and the gas temperature, resulting in a condensation on a colder surface. Complex mathematical model, including surface condensation, is developed for this type of biogas dehumidifier and the parameter study is carried out for a wide range of parameters. The model is reduced to 1D case to make numerical calculations faster. It is shown that latent heat of condensation is very important for the total heat balance and the condensation rate is highly dependent on insulation between layers and outside temperature. Modelling results allow finding optimal geometrical parameters for the known gas flow and predicting the condensation rate for different system setups and seasons.

  19. Experimental Study on a New Dual-Layer Granular Bed Filter for Removing Particulates

    Institute of Scientific and Technical Information of China (English)

    YANG Guo-hua; ZHOU Jiang-hua

    2007-01-01

    A new dual-layer granular bed filter for hot gas cleanup was invented and studied experimentally. Fine sand, 0.5-1 mm grain size and about 1350 kg/m3 bulk density, was used as the lower layer of the filter. Expanded perlite particles, 2-5 mm grain size and about 70 kg/m3 bulk density, was used for the upper layer of the filter in this study. It was confirmed that the sizes and densities of these two media matched well; the binary media remained in complete segregation during regeneration by fluidization. Test results show that the filtration of the expanded perlite particle layer was characterized as "deep bed filtration." Filtration of the fine sand layer was "surface cake filtration." The expanded perlite particle layer contributed about 90% to the bed dust capacity, but only about 20% to the total bed pressure drop, which increased the bed dust capacity ten fold compared to a single-layer bed of the same sand and the same total bed pressure drop. The dust cake on the surface of the fine sand layer raised the collection efficiencies to over 99.99%.

  20. Monte Carlo study of MLC fields for cobalt therapy machine

    Directory of Open Access Journals (Sweden)

    Komanduri M Ayyangar

    2014-01-01

    Full Text Available An automated Multi-Leaf Collimator (MLC system has been developed as add-on for the cobalt-60 teletherapy machines available in India. The goal of the present computational study is to validate the MLC design using Monte Carlo (MC modeling. The study was based on the Kirloskar-supplied Phoenix model machines that closely match the Atomic Energy of Canada Limited (AECL theratron-80 machine. The MLC is a retrofit attachment to the collimator assembly, with 14 non-divergent leaf pairs of 40 mm thick, 7 mm wide, and 150 mm long tungsten alloy plates with rounded edges and 20 mm tongue and 2 mm groove in each leaf. In the present work, the source and collimator geometry has been investigated in detail to arrive at a model that best represents the measured dosimetric data. The authors have studied in detail the proto-I MLC built for cobalt-60. The MLC field sizes were MC simulated for 2 × 2 cm 2 to 14 × 14 cm 2 square fields as well as irregular fields, and the percent depth dose (PDD and profile data were compared with ROPS† treatment planning system (TPS. In addition, measured profiles using the IMATRIXX system‡ were also compared with the MC simulations. The proto-I MLC can define radiation fields up to 14 × 14 cm΂ within 3 mm accuracy. The maximum measured leakage through the leaf ends in closed condition was 3.4% and interleaf leakage observed was 7.3%. Good agreement between MC results, ROPS and IMATRIXX results has been observed. The investigation also supports the hypothesis that optical and radiation field coincidence exists for the square fields studied with the MLC. Plots of the percent depth dose (PDD data and profile data for clinically significant irregular fields have also been presented. The MC model was also investigated to speed up the calculations to allow calculations of clinically relevant conformal beams.

  1. High-performance, anode-supported, microtubular SOFC prepared from single-step-fabricated, dual-layer hollow fibers

    Energy Technology Data Exchange (ETDEWEB)

    Othman, Mohd Hafiz Dzarfan; Droushiotis, Nicolas; Wu, Zhentao; Kelsall, Geoff; Li, Kang [Department of Chemical Engineering, Imperial College London, London SW7 2AZ (United Kingdom)

    2011-06-03

    A high-performance, microtubular solid oxide fuel cell is developed using an improved electrolyte/anode dual-layer hollow fiber fabricated via a novel coextrusion and co-sintering technique. The technique allows control over the porosity of the anode, resulting in an increase in the power output to almost double what has been previously reported. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Design and Performance of Broadband Dual Layer Circular Polarizer Based on Frequency Selective Surface for X-Band Applications

    Directory of Open Access Journals (Sweden)

    FARMAN ALIMANGI

    2017-07-01

    Full Text Available A dual-layer circular polarizer based on FSS (Frequency Selective Surface composed of two periodic strips in xoy plane. The transmission characteristic of present structure is comprehensively investigated that convert linearly polarized wave into circular polarized wave at operated frequencies. The designed structure has optimal performance for x-band applications. In addition, the designed model of single and dual-layer circular polarizer feature exceptionally strong circular polarization with low loss transmission and attracted for radar and satellite applications. The designed structures of circular polarizers are simple and can be easy fabricated as well. The transmitted waves are achieved with RHCP (Right Handed Circular Polarization wave at 9.34 GHz and LHCP (Left Handed Circular Polarization wave at 10.73 GHZ. The corresponding axial ratio bandwidth is enhanced from 9.1610.85GHz = 16.89%, respectively. Meanwhile, the proposed dual-layer circular polarizer achieves transmission with RHCP wave at 9.59 GHz and axial ratio bandwidth is achieved from9.3-11.31GHz = 19.49%, respectively.

  3. Dual Layer Monolith ATR of Pyrolysis Oil for Distributed Synthesis Gas Production

    Energy Technology Data Exchange (ETDEWEB)

    Lawal, Adeniyi [Stevens Institute of Technology, Castle Point Hoboken NJ 07030

    2012-09-29

    We have successfully demonstrated a novel reactor technology, based on BASF dual layer monolith catalyst, for miniaturizing the autothermal reforming of pyrolysis oil to syngas, the second and most critical of the three steps for thermochemically converting biomass waste to liquid transportation fuel. The technology was applied to aged as well as fresh samples of pyrolysis oil derived from five different biomass feedstocks, namely switch-grass, sawdust, hardwood/softwood, golden rod and maple. Optimization of process conditions in conjunction with innovative reactor system design enabled the minimization of carbon deposit and control of the H2/CO ratio of the product gas. A comprehensive techno-economic analysis of the integrated process using in part, experimental data from the project, indicates (1) net energy recovery of 49% accounting for all losses and external energy input, (2) weight of diesel oil produced as a percent of the biomass to be ~14%, and (3) for a demonstration size biomass to Fischer-Tropsch liquid plant of ~ 2000 daily barrels of diesel, the price of the diesel produced is ~$3.30 per gallon, ex. tax. However, the extension of catalyst life is critical to the realization of the projected economics. Catalyst deactivation was observed and the modes of deactivation, both reversible and irreversible were identified. An effective catalyst regeneration strategy was successfully demonstrated for reversible catalyst deactivation while a catalyst preservation strategy was proposed for preventing irreversible catalyst deactivation. Future work should therefore be focused on extending the catalyst life, and a successful demonstration of an extended (> 500 on-stream hours) catalyst life would affirm the commercial viability of the process.

  4. MLC1 protein: a likely link between leukodystrophies and brain channelopathies

    Directory of Open Access Journals (Sweden)

    Maria Stefania eBrignone

    2015-04-01

    Full Text Available Megalencephalic leukoencephalopathy with subcortical cysts (MLC disease is a rare inherited, autosomal recessive form of childhood-onset spongiform leukodystrophy characterized by macrocephaly, deterioration of motor functions, epileptic seizures and mental decline. Brain edema, subcortical fluid cysts, myelin and astrocyte vacuolation are the histopathological hallmarks of MLC. Mutations in either the MLC1 gene (>75% of patients or the GlialCAM gene (<20% of patients are responsible for the disease. Recently, the GlialCAM adhesion protein was found essential for the membrane expression and function of the chloride channel ClC-2 indicating MLC disease caused by mutation in GlialCAM as the first channelopathy among leukodystrophies.. These results may explain the phenotypic convergence of ClC-2 KO mice showing brain edema and myelin vacuolation and human MLC pathology, despite mutations in the ClC-2 gene were not found in patients affected by this leukodystrophy. On the contrary, the function of MLC1 protein, which binds GlialCAM, its functional relationship with ClC-2 and the molecular mechanisms underlying MLC1 mutation-induced functional defects are not fully understood yet. The human MLC1 gene encodes a 377-amino acid membrane protein with eight predicted transmembrane domains which shows very low homology with voltage-dependent potassium K+ channel subunits. The high expression of MLC1 in brain astrocytes contacting blood vessels and meninges and brain alterations observed in MLC patients have led to hypothesize a role for MLC1 in the regulation of ion and water homeostasis. Recent studies have shown that MLC1 establishes structural and/or functional interactions with several ion/water channels and transporters and ion channel accessory proteins, and that these interactions are affected by MLC1 mutations causing MLC. Here, we review data on MLC1 functional properties obtained in in vitro and in vivo models and discuss evidence linking the

  5. Implications of a high-definition multileaf collimator (HD-MLC on treatment planning techniques for stereotactic body radiation therapy (SBRT: a planning study

    Directory of Open Access Journals (Sweden)

    Chen Yiyi

    2009-07-01

    Full Text Available Abstract Purpose To assess the impact of two multileaf collimator (MLC systems (2.5 and 5 mm leaf widths on three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and dynamic conformal arc techniques for stereotactic body radiation therapy (SBRT of liver and lung lesions. Methods Twenty-nine SBRT plans of primary liver (n = 11 and lung (n = 18 tumors were the basis of this study. Five-millimeter leaf width 120-leaf Varian Millennium (M120 MLC-based plans served as reference, and were designed using static conformal beams (3DCRT, sliding-window intensity-modulated beams (IMRT, or dynamic conformal arcs (DCA. Reference plans were either re-optimized or recomputed, with identical planning parameters, for a 2.5-mm width 120-leaf BrainLAB/Varian high-definition (HD120 MLC system. Dose computation was based on the anisotropic analytical algorithm (AAA, Varian Medical Systems with tissue heterogeneity taken into account. Each plan was normalized such that 100% of the prescription dose covered 95% of the planning target volume (PTV. Isodose distributions and dose-volume histograms (DVHs were computed and plans were evaluated with respect to target coverage criteria, normal tissue sparing criteria, as well as treatment efficiency. Results Dosimetric differences achieved using M120 and the HD120 MLC planning were generally small. Dose conformality improved in 51.7%, 62.1% and 55.2% of the IMRT, 3DCRT and DCA cases, respectively, with use of the HD120 MLC system. Dose heterogeneity increased in 75.9%, 51.7%, and 55.2% of the IMRT, 3DCRT and DCA cases, respectively, with use of the HD120 MLC system. DVH curves demonstrated a decreased volume of normal tissue irradiated to the lower (90%, 50% and 25% isodose levels with the HD120 MLC. Conclusion Data derived from the present comparative assessment suggest dosimetric merit of the high definition MLC system over the millennium MLC system. However, the clinical significance of these results

  6. Monte Carlo study of MLC fields for cobalt therapy machine

    Science.gov (United States)

    Ayyangar, Komanduri M.; Rani, Roopa A.; Kumar, Anil; Reddy, A. R.

    2014-01-01

    An automated Multi-Leaf Collimator (MLC) system has been developed as add-on for the cobalt-60 teletherapy machines available in India. The goal of the present computational study is to validate the MLC design using Monte Carlo (MC) modeling. The study was based on the Kirloskar-supplied Phoenix model machines that closely match the Atomic Energy of Canada Limited (AECL) theratron-80 machine. The MLC is a retrofit attachment to the collimator assembly, with 14 non-divergent leaf pairs of 40 mm thick, 7 mm wide, and 150 mm long tungsten alloy plates with rounded edges and 20 mm tongue and 2 mm groove in each leaf. In the present work, the source and collimator geometry has been investigated in detail to arrive at a model that best represents the measured dosimetric data. The authors have studied in detail the proto-I MLC built for cobalt-60. The MLC field sizes were MC simulated for 2 × 2 cm2 to 14 × 14 cm2 square fields as well as irregular fields, and the percent depth dose (PDD) and profile data were compared with ROPS† treatment planning system (TPS). In addition, measured profiles using the IMATRIXX system‡ were also compared with the MC simulations. The proto-I MLC can define radiation fields up to 14 × 14 cm2 within 3 mm accuracy. The maximum measured leakage through the leaf ends in closed condition was 3.4% and interleaf leakage observed was 7.3%. Good agreement between MC results, ROPS and IMATRIXX results has been observed. The investigation also supports the hypothesis that optical and radiation field coincidence exists for the square fields studied with the MLC. Plots of the percent depth dose (PDD) data and profile data for clinically significant irregular fields have also been presented. The MC model was also investigated to speed up the calculations to allow calculations of clinically relevant conformal beams. †Radiation Oncology Planning System (ROPS) is supplied by Tirumala Jyothi Computer Systems described at https

  7. Evaluating efficiency of coaxial MLC VMAT plan for spine SBRT

    Energy Technology Data Exchange (ETDEWEB)

    Son, Sang Jun; Mun, Jun Ki; Kim, Dae Ho; Yoo, Suk Hyun [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2014-12-15

    The purpose of the study is to evaluate the efficiency of Coaxial MLC VMAT plan (Using 273° and 350° collimator angle) That the leaf motion direction aligned with axis of OAR (Organ at risk, It means spinal cord or cauda equine in this study.) compare to Universal MLC VMAT plan (using 30° and 330 ° collimator angle) for spine SBRT. The 10 cases of spine SBRT that treated with VMAT planned by Coaxial MLC and Varian TBX were enrolled. Those cases were planned by Eclipse (Ver. 10.0.42, Varian, USA), PRO3 (Progressive Resolution Optimizer 10.0.28) and AAA (Anisotropic Analytic Algorithm Ver. 10.0.28) with coplanar 260 ° arcs and 10MV FFF (Flattening filter free). Each arc has 273° and 350 ° collimator angle, respectively. The Universal MLC VMAT plans are based on existing treatment plans. Those plans have the same parameters of existing treatment plans but collimator angle. To minimize the dose difference that shows up randomly on optimizing, all plans were optimized and calculated twice respectively. The calculation grid is 0.2 cm and all plans were normalized to the target V100%=90%. The indexes of evaluation are V10Gy, D0.03cc, Dmean of OAR (Organ at risk, It means spinal cord or cauda equine in this study.), H.I (Homogeneity index) of the target and total MU. All Coaxial VMAT plans were verified by gamma test with Mapcheck2 (Sun Nuclear Co., USA), Mapphan (Sun Nuclear Co., USA) and SNC patient (Sun Nuclear Co., USA Ver 6.1.2.18513). The difference between the coaxial and the universal VMAT plans are follow. The coaxial VMAT plan is better in the V10Gy of OAR, Up to 4.1%, at least 0.4%, the average difference was 1.9% and In the D0.03cc of OAR, Up to 83.6 cGy, at least 2.2 cGy, the average difference was 33.3 cGy. In Dmean, Up to 34.8 cGy, at least -13.0 cGy, the average difference was 9.6 cGy that say the coaxial VMAT plans are better except few cases. H.I difference Up to 0.04, at least 0.01, the average difference was 0.02 and the difference of average

  8. Ni/Ni-YSZ current collector/anode dual layer hollow fibers for micro-tubular solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kanawka, K.; Othman, M.H.D.; Droushiotis, N.; Wu, Z.; Kelsall, G.; Li, K. [Department of Chemical Engineering and Chemical Technology, Imperial College London, London SW7 2AZ (United Kingdom)

    2011-10-15

    A co-extrusion technique was employed to fabricate a novel dual layer NiO/NiO-YSZ hollow fiber (HF) precursor which was then co-sintered at 1,400 C and reduced at 700 C to form, respectively, a meshed porous inner Ni current collector and outer Ni-YSZ anode layers for SOFC applications. The inner thin and highly porous ''mesh-like'' pure Ni layer of approximately 50 {mu}m in thickness functions as a current collector in micro-tubular solid oxide fuel cell (SOFC), aiming at highly efficient current collection with low fuel diffusion resistance, while the thicker outer Ni-YSZ layer of 260 {mu}m acts as an anode, providing also major mechanical strength to the dual-layer HF. Achieved morphology consisted of short finger-like voids originating from the inner lumen of the HF, and a sponge-like structure filling most of the Ni-YSZ anode layer, which is considered to be suitable macrostructure for anode SOFC system. The electrical conductivity of the meshed porous inner Ni layer is measured to be 77.5 x 10{sup 5} S m{sup -1}. This result is significantly higher than previous reported results on single layer Ni-YSZ HFs, which performs not only as a catalyst for the oxidation reaction, but also as a current collector. These results highlight the advantages of this novel dual-layer HF design as a new and highly efficient way of collecting current from the lumen of micro-tubular SOFC. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Determination of optimal parameters for dual-layer cathode of polymer electrolyte fuel cell using computational intelligence-aided design.

    Science.gov (United States)

    Chen, Yi; Huang, Weina; Peng, Bei

    2014-01-01

    Because of the demands for sustainable and renewable energy, fuel cells have become increasingly popular, particularly the polymer electrolyte fuel cell (PEFC). Among the various components, the cathode plays a key role in the operation of a PEFC. In this study, a quantitative dual-layer cathode model was proposed for determining the optimal parameters that minimize the over-potential difference η and improve the efficiency using a newly developed bat swarm algorithm with a variable population embedded in the computational intelligence-aided design. The simulation results were in agreement with previously reported results, suggesting that the proposed technique has potential applications for automating and optimizing the design of PEFCs.

  10. Determination of the optimal tolerance for MLC positioning in sliding window and VMAT techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, V., E-mail: vhernandezmasgrau@gmail.com; Abella, R. [Department of Medical Physics, Hospital Sant Joan de Reus, IISPV, Tarragona 43204 (Spain); Calvo, J. F. [Department of Radiation Oncology, Hospital Quirón, Barcelona 08023 (Spain); Jurado-Bruggemann, D. [Department of Medical Physics, Institut Català d’Oncologia, Girona 17007 (Spain); Sancho, I. [Department of Medical Physics, Institut Català d’Oncologia, L’Hospitalet de Llobregat 08908 (Spain); Carrasco, P. [Department of Medical Physics, Hospital de la Santa Creu i Sant Pau, Barcelona 08041 (Spain)

    2015-04-15

    Purpose: Several authors have recommended a 2 mm tolerance for multileaf collimator (MLC) positioning in sliding window treatments. In volumetric modulated arc therapy (VMAT) treatments, however, the optimal tolerance for MLC positioning remains unknown. In this paper, the authors present the results of a multicenter study to determine the optimal tolerance for both techniques. Methods: The procedure used is based on dynalog file analysis. The study was carried out using seven Varian linear accelerators from five different centers. Dynalogs were collected from over 100 000 clinical treatments and in-house software was used to compute the number of tolerance faults as a function of the user-defined tolerance. Thus, the optimal value for this tolerance, defined as the lowest achievable value, was investigated. Results: Dynalog files accurately predict the number of tolerance faults as a function of the tolerance value, especially for low fault incidences. All MLCs behaved similarly and the Millennium120 and the HD120 models yielded comparable results. In sliding window techniques, the number of beams with an incidence of hold-offs >1% rapidly decreases for a tolerance of 1.5 mm. In VMAT techniques, the number of tolerance faults sharply drops for tolerances around 2 mm. For a tolerance of 2.5 mm, less than 0.1% of the VMAT arcs presented tolerance faults. Conclusions: Dynalog analysis provides a feasible method for investigating the optimal tolerance for MLC positioning in dynamic fields. In sliding window treatments, the tolerance of 2 mm was found to be adequate, although it can be reduced to 1.5 mm. In VMAT treatments, the typically used 5 mm tolerance is excessively high. Instead, a tolerance of 2.5 mm is recommended.

  11. A dual layer Ni/Ni-YSZ hollow fibre for micro-tubular SOFC anode support with a current collector

    Energy Technology Data Exchange (ETDEWEB)

    Kanawka, Krzysztof; Othman, Mohd Hafiz Dzarfan; Wu, Zhentao; Droushiotis, Nicolas; Kelsall, Geoff; Li, Kang [Department of Chemical Engineering and Chemical Technology, Imperial College London (United Kingdom)

    2011-01-15

    A co-extrusion technique was employed to fabricate a dual layer NiO/NiO-YSZ hollow fibre precursor which was then co-sintered at 1400C and reduced at 700C to form, respectively, a meshed porous inner Ni current collector and outer Ni-YSZ anode layers for SOFC applications. Achieved morphology consisted of short finger-like voids originating from the inner bore of the hollow fibre, and a sponge-like structure filling most of the Ni-YSZ anode layer, which is considered to be suitable macrostructure for anode SOFC system. The electrical conductivity of the meshed porous inner Ni layer was measured to be 77.5 x 10{sup 5} S m{sup -1}. This result is significantly higher than previous reported results on single layer Ni-YSZ hollow fibres, which besides performing a catalyst function for the oxidation reaction also act as a current collector. These results highlight the advantages of this dual-layer hollow fibre design especially in developing a new and highly efficient way in current collection for micro-tubular SOFC. (author)

  12. [Computer-assisted histocompatibility assessment in mixed lymphocyte culture (MLC)].

    Science.gov (United States)

    Schwartz, D; Hajek-Rosenmayr, A

    1987-02-20

    Analysis of the results of mixed lymphocyte culture (MLC) for compatibility testing preceding transplantation of bone marrow and other organs has so far required a vast input, both in terms of laboratory staff and work hours. We have developed a computer programme which performs this work rapidly. Graphics of the reaction patterns can be obtained, moreover, and these can prove a helpful tool in interpretation of the results.

  13. A dosimetric evaluation of the Eclipse AAA algorithm and Millennium 120 MLC for cranial intensity-modulated radiosurgery.

    Science.gov (United States)

    Calvo Ortega, Juan Francisco; Moragues, Sandra; Pozo, Miquel; José, Sol San; Puertas, Enrique; Fernández, Jaime; Casals, Joan

    2014-01-01

    The aim of this study is to assess the accuracy of a convolution-based algorithm (anisotropic analytical algorithm [AAA]) implemented in the Eclipse planning system for intensity-modulated radiosurgery (IMRS) planning of small cranial targets by using a 5-mm leaf-width multileaf collimator (MLC). Overall, 24 patient-based IMRS plans for cranial lesions of variable size (0.3 to 15.1cc) were planned (Eclipse, AAA, version 10.0.28) using fixed field-based IMRS produced by a Varian linear accelerator equipped with a 120 MLC (5-mm width on central leaves). Plan accuracy was evaluated according to phantom-based measurements performed with radiochromic film (EBT2, ISP, Wayne, NJ). Film 2D dose distributions were performed with the FilmQA Pro software (version 2011, Ashland, OH) by using the triple-channel dosimetry method. Comparison between computed and measured 2D dose distributions was performed using the gamma method (3%/1mm). Performance of the MLC was checked by inspection of the DynaLog files created by the linear accelerator during the delivery of each dynamic field. The absolute difference between the calculated and measured isocenter doses for all the IMRS plans was 2.5% ± 2.1%. The gamma evaluation method resulted in high average passing rates of 98.9% ± 1.4% (red channel) and 98.9% ± 1.5% (blue and green channels). DynaLog file analysis revealed a maximum root mean square error of 0.46mm. According to our results, we conclude that the Eclipse/AAA algorithm provides accurate cranial IMRS dose distributions that may be accurately delivered by a Varian linac equipped with a Millennium 120 MLC.

  14. A novel nano-sulfur/polypyrrole/graphene nanocomposite cathode with a dual-layered structure for lithium rechargeable batteries

    Science.gov (United States)

    Zhang, Yongguang; Zhao, Yan; Konarov, Aishuak; Gosselink, Denise; Soboleski, Hayden Greentree; Chen, P.

    2013-11-01

    A method for synthesizing nano-sulfur/polypyrrole/graphene nanosheet (nano-S/PPy/GNS) ternary composite with a dual-layered structure is described. By taking advantage of both capillary force driven self-assembly of polypyrrole on graphene nanosheets and adhesion ability of polypyrrole to sulfur, we develop a stable and ordered nano-S/PPy/GNS composite cathode for lithium/sulfur (Li/S) batteries. The high dispersion of nanoscopic sulfur on the surface of PPy/GNS composite and good electrical conductivity of GNS seems to benefit the sulfur utilization and the reactivity of the composite. Furthermore, PPy plays an important role in retarding diffusion of polysulfides out of the electrode. The resulting nano-S/PPy/GNS composite cathode delivers a high initial capacity of 1415.7 mAh g-1, remaining a reversible capacity of 641.5 mAh g-1 after 40 cycles at 0.1 C rate.

  15. Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes.

    Science.gov (United States)

    Jung, Dong-Won; Kim, Jun-Ho; Kim, Se-Hoon; Kim, Jun-Bom; Oh, Eun-Suok

    2013-05-01

    The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test.

  16. A Novel MLC Scheme with M2-QAM Constellations over AWGN and Rayleigh Fading Channels

    Institute of Scientific and Technical Information of China (English)

    YUANDongfeng; ZHANGPeng; WayneE.Stark

    2003-01-01

    Optimal multilevel codes (MLC) with M2-QAM constellations are considered with focus on both AWGN and Rayleigh fading channels. With the proposition of three new set partitioning rules for M2-QAM constellations, a novel simplified MLC scheme with a very simple MSD (Multistage decoding) structure comes into being, which is operated on the capacity rule. Compared with traditional MLC/MSD scheme the new MLC/MSD structure greatly reduces the calculation of the individual capacities in MLC system because the new set partitioning rules ensure the independency of two dimensions symbols. Furthermore the new MLC/MSD system cannot enhance any performance loss and the time delay is just 1/2 of that with traditional partitioning rules. As an example 64-QAM constellation with three new set partitioning rules are provided. Their performance is simulated over AWGN and Rayleigh fading channels by choosing BCH codes as the component codes.

  17. Acetonitrile extraction and dual-layer solid phase extraction clean-up for pesticide residue analysis in propolis.

    Science.gov (United States)

    Oellig, Claudia

    2016-05-06

    Propolis is a very complex mixture of substances that is produced by honey bees and is known to be a rather challenging matrix for residue analysis. Besides resins, flavonoids and phenols, high amount of wax is co-extracted resulting in immense matrix effects. Therefore a suitable clean-up is crucial and indispensable. In this study, a reliable solid phase extraction (SPE) clean-up was developed for pesticide residue analysis in propolis. The clean-up success was quickly and easily monitored by high-performance thin-layer chromatography with different detection possibilities. The final method consists of the extraction of propolis with acetonitrile according to the QuEChERS method followed by an effective extract purification on dual-layer SPE cartridges with spherical hydrophobic polystyrene-divinylbenzene resin/primary secondary amine as sorbent and a mixture of toluene/acetone (95:5, v/v) for elution. Besides fat-soluble components like waxes, flavonoids, and terpenoids, more polar compounds like organic acids, fatty acids, sugars and anthocyanins were also removed to large extent. Method performance was assessed by recovery experiments at spiking levels of 0.5 and 1mg/kg (n=5) for fourteen pesticides that are relevant for propolis. Mean recoveries determined by HPLC-MS against solvent standards were between 40 and 101%, while calculation against matrix-matched standards provided recoveries of 79-104%. Precision of recovery, assessed by relative standard deviations, were below 9%. Thus, the developed dual-layer SPE clean-up enables the reliable pesticide residue analysis in propolis and provides a suitable alternative to time-consuming clean-up procedures proposed in literature.

  18. Novel Electrospun Dual-Layered Composite Nanofibrous Membrane Endowed with Electricity-Magnetism Bifunctionality at One Layer and Photoluminescence at the Other Layer.

    Science.gov (United States)

    Wang, Zijiao; Ma, Qianli; Dong, Xiangting; Li, Dan; Xi, Xue; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

    2016-10-05

    Dual-layered composite nanofibrous membrane equipped with electrical conduction, magnetism and photoluminescence trifunctionality is constructed via electrospinning. The composite membrane consists of a polyaniline (PANI)/Fe3O4 nanoparticles (NPs)/polyacrylonitrile (PAN) tuned electrical-magnetic bifunctional nanofibrous layer at one side and a Eu(TTA)3(TPPO)2/polyvinylpyrrolidone (PVP) photoluminescent nanofibrous layer at the other side, and the two layers are tightly combined face-to-face together into the novel dual-layered composite membrane with trifunctionality. The electric conductivity and magnetism of electrical-magnetic bifunctionality can be respectively tunable via modulating the respective PANI and Fe3O4 NPs contents, and the highest electric conductivity approaches the order of 1 × 10(-2) S cm(-1). Predominant red emission at 615 nm can be obviously observed in the photoluminescent layer under 366 nm excitation. Moreover, the luminescent intensity of photoluminescent layer is almost unaffected by the electrical-magnetic bifunctional layer because of the fact that the photoluminescent materials have been successfully isolated from dark-colored PANI and Fe3O4 NPs. The novel dual-layered composite nanofibrous membrane with trifunctionality has potentials in many fields. Furthermore, the design philosophy and fabrication method for the dual-layered multifunctional membrane provide a new and facile strategy toward other membranes with multifunctionality.

  19. Efficiency Enhancement of Nanotextured Black Silicon Solar Cells Using Al2O3/TiO2 Dual-Layer Passivation Stack Prepared by Atomic Layer Deposition.

    Science.gov (United States)

    Wang, Wei-Cheng; Tsai, Meng-Chen; Yang, Jason; Hsu, Chuck; Chen, Miin-Jang

    2015-05-20

    In this study, efficient nanotextured black silicon (NBSi) solar cells composed of silicon nanowire arrays and an Al2O3/TiO2 dual-layer passivation stack on the n(+) emitter were fabricated. The highly conformal Al2O3 and TiO2 surface passivation layers were deposited on the high-aspect-ratio surface of the NBSi wafers using atomic layer deposition. Instead of the single Al2O3 passivation layer with a negative oxide charge density, the Al2O3/TiO2 dual-layer passivation stack treated with forming gas annealing provides a high positive oxide charge density and a low interfacial state density, which are essential for the effective field-effect and chemical passivation of the n(+) emitter. In addition, the Al2O3/TiO2 dual-layer passivation stack suppresses the total reflectance over a broad range of wavelengths (400-1000 nm). Therefore, with the Al2O3/TiO2 dual-layer passivation stack, the short-circuit current density and efficiency of the NBSi solar cell were increased by 11% and 20%, respectively. In conclusion, a high efficiency of 18.5% was achieved with the NBSi solar cells by using the n(+)-emitter/p-base structure passivated with the Al2O3/TiO2 stack.

  20. Analysis of direct clinical consequences of MLC positional errors in volumetric-modulated arc therapy using 3D dosimetry system.

    Science.gov (United States)

    Nithiyanantham, Karthikeyan; Mani, Ganesh K; Subramani, Vikraman; Mueller, Lutz; Palaniappan, Karrthick K; Kataria, Tejinder

    2015-09-08

    In advanced, intensity-modulated external radiotherapy facility, the multileaf collimator has a decisive role in the beam modulation by creating multiple segments or dynamically varying field shapes to deliver a uniform dose distribution to the target with maximum sparing of normal tissues. The position of each MLC leaf has become more critical for intensity-modulated delivery (step-and-shoot IMRT, dynamic IMRT, and VMAT) compared to 3D CRT, where it defines only field boundaries. We analyzed the impact of the MLC positional errors on the dose distribution for volumetric-modulated arc therapy, using a 3D dosimetry system. A total of 15 VMAT cases, five each for brain, head and neck, and prostate cases, were retrospectively selected for the study. All the plans were generated in Monaco 3.0.0v TPS (Elekta Corporation, Atlanta, GA) and delivered using Elekta Synergy linear accelerator. Systematic errors of +1, +0.5, +0.3, 0, -1, -0.5, -0.3 mm were introduced in the MLC bank of the linear accelerator and the impact on the dose distribution of VMAT delivery was measured using the COMPASS 3D dosim-etry system. All the plans were created using single modulated arcs and the dose calculation was performed using a Monte Carlo algorithm in a grid size of 3 mm. The clinical endpoints D95%, D50%, D2%, and Dmax,D20%, D50% were taken for the evaluation of the target and critical organs doses, respectively. A significant dosimetric effect was found for many cases even with 0.5 mm of MLC positional errors. The average change of dose D 95% to PTV for ± 1 mm, ± 0.5 mm, and ±0.3mm was 5.15%, 2.58%, and 0.96% for brain cases; 7.19%, 3.67%, and 1.56% for head and neck cases; and 8.39%, 4.5%, and 1.86% for prostate cases, respectively. The average deviation of dose Dmax was 5.4%, 2.8%, and 0.83% for brainstem in brain cases; 8.2%, 4.4%, and 1.9% for spinal cord in H&N; and 10.8%, 6.2%, and 2.1% for rectum in prostate cases, respectively. The average changes in dose followed a linear

  1. SIEMENS MLC-82日常维护及故障检修%Routine maintenance and trouble shooting of SIEMENS MLC-82 multi-leaf collimator

    Institute of Scientific and Technical Information of China (English)

    陶长龙

    2011-01-01

    The MLC-82 electric multi-leaf collimator (MLC-Multileaf Collimator) system of Siemens is composed of two parts of hardware and software. In this paper, the author introduced the effect of the collimator and methods for maintenance of its hardware to share with counterparts.%西门子MLC-82电动多叶准直器(MLC—MultileafCollimator)系统由硬件和软件两部分组成。简要阐述了多叶准直器的作用,系统硬件的维修经验,介绍SIEMENS MLC-82硬件系统的日常维护及常见故障的检修。

  2. Design and fabrication of a CH/Al dual-layer perturbation target for hydrodynamic instability experiments in ICF

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Jun [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Xie, Zhiyong [Shanghai Institute of Laser Plasma, Shanghai 201800 (China); Du, Ai [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Ye, Junjian [Shanghai Institute of Laser Plasma, Shanghai 201800 (China); Zhang, Zhihua; Shen, Jun [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Zhou, Bin, E-mail: zhoubin863@tongji.edu.cn [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China)

    2014-04-15

    Highlights: • Sinusoidal perturbed Al foil was prepared by single-point diamond turning. • Perturbed Al foil was measured by surface profiler and white light interferometer. • Perturbed Al foil and CH layer adhered with each other via a hot-press process. • Parameters and cross-section of the CH–Al perturbation target was characterized. - Abstract: A polystyrene (CH)/aluminum (Al) dual-layer perturbation target for hydrodynamic instability experiments in inertial confinement fusion (ICF) was designed and fabricated. The target was composed of a perturbed 40 μm Al foil and a CH layer. The detailed fabrication method consisted of four steps. The 40 μm Al foil was first prepared by roll and polish process; the perturbation patterns were then introduced on the surface of the Al foil by the single-point diamond turning (SPDT) technology; the CH layer was prepared via a simple method which called spin-coating process; finally, the CH layer was directly coated on the perturbation surface of Al foil by a hot-press process to avoid the use of a sticker and to eliminate the gaps between the CH layer and the Al foil. The parameters of the target, such as the perturbation wavelength (T) and perturbation amplitude (A), were characterized by a QC-5000 tool microscope, an alpha-step 500 surface profiler and a NT1100 white light interferometer. The results showed that T and A of the target were about 52 μm and 7.34 μm, respectively. Thickness of the Al foil (H1), thickness of the CH layer (H2), and cross-section of the dual-layer target were characterized by a QC-5000 tool microscope and a scanning electron microscope (SEM). H1 and H2 were about 40 μm and 15 μm, respectively, the cross-sectional photographs of the target showed that the CH layer and the Al foil adhered perfectly with each other.

  3. Impact of MLC properties and IMRT technique in meningioma and head-and-neck treatments

    DEFF Research Database (Denmark)

    Kantz, Steffi; Söhn, Matthias; Troeller, Almut

    2015-01-01

    -planned for step-and-shoot IMRT (ssIMRT), sliding window IMRT (dMLC) and VMAT using the MLCi2 without (-) and with (+) interdigitation and the Agility-MLC attached to an Elekta 6MV linac. This results in nine plans per patient. Consistent patient individual optimization parameters are used. Plans are generated...

  4. Combining MLC and SVM Classifiers for Learning Based Decision Making: Analysis and Evaluations.

    Science.gov (United States)

    Zhang, Yi; Ren, Jinchang; Jiang, Jianmin

    2015-01-01

    Maximum likelihood classifier (MLC) and support vector machines (SVM) are two commonly used approaches in machine learning. MLC is based on Bayesian theory in estimating parameters of a probabilistic model, whilst SVM is an optimization based nonparametric method in this context. Recently, it is found that SVM in some cases is equivalent to MLC in probabilistically modeling the learning process. In this paper, MLC and SVM are combined in learning and classification, which helps to yield probabilistic output for SVM and facilitate soft decision making. In total four groups of data are used for evaluations, covering sonar, vehicle, breast cancer, and DNA sequences. The data samples are characterized in terms of Gaussian/non-Gaussian distributed and balanced/unbalanced samples which are then further used for performance assessment in comparing the SVM and the combined SVM-MLC classifier. Interesting results are reported to indicate how the combined classifier may work under various conditions.

  5. Combining MLC and SVM Classifiers for Learning Based Decision Making: Analysis and Evaluations

    Directory of Open Access Journals (Sweden)

    Yi Zhang

    2015-01-01

    Full Text Available Maximum likelihood classifier (MLC and support vector machines (SVM are two commonly used approaches in machine learning. MLC is based on Bayesian theory in estimating parameters of a probabilistic model, whilst SVM is an optimization based nonparametric method in this context. Recently, it is found that SVM in some cases is equivalent to MLC in probabilistically modeling the learning process. In this paper, MLC and SVM are combined in learning and classification, which helps to yield probabilistic output for SVM and facilitate soft decision making. In total four groups of data are used for evaluations, covering sonar, vehicle, breast cancer, and DNA sequences. The data samples are characterized in terms of Gaussian/non-Gaussian distributed and balanced/unbalanced samples which are then further used for performance assessment in comparing the SVM and the combined SVM-MLC classifier. Interesting results are reported to indicate how the combined classifier may work under various conditions.

  6. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC leaves for volumetric modulated arc therapy (VMAT

    Directory of Open Access Journals (Sweden)

    Xu Zhengzheng

    2016-03-01

    Full Text Available This study is to report 1 the sensitivity of intensity modulated radiation therapy (IMRT QA method for clinical volumetric modulated arc therapy (VMAT plans with multi-leaf collimator (MLC leaf errors that will not trigger MLC interlock during beam delivery; 2 the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery.

  7. On the development of a dual-layered diamond-coated tool for the effective machining of titanium Ti-6Al-4V alloy

    Science.gov (United States)

    Srinivasan, Balaji; Ramachandra Rao, M. S.; Rao, Balkrishna C.

    2017-01-01

    This work is focused on the development of a dual-layered diamond-coated tungsten carbide tool for machining titanium Ti-6Al-4V alloy. A hot-filament chemical vapor deposition technique was used to synthesize diamond films on tungsten carbide tools. A boron-doped diamond interlayer was added to a microcrystalline diamond layer in an attempt to improve the interface adhesion strength. The dual-layered diamond-coated tool was employed in machining at cutting speeds in the range of 70 to 150 m min-1 with a lower feed and a lower depth of cut of 0.5 mm rev-1 and 0.5 mm, respectively, to operate in the transition from adhesion- to diffusion-tool-wear and thereby arrive at suitable conditions for enhancing tool life. The proposed tool was then compared, on the basis of performance under real-time cutting conditions, with commercially available microcrystalline diamond, nanocrystalline diamond, titanium nitride and uncoated tungsten carbide tools. The life and surface finish of the proposed dual-layered tool and uncoated tungsten carbide were also investigated in interrupted cutting such as milling. The results of this study show a significant improvement in tool life and finish of Ti-6Al-4V parts machined with the dual-layered diamond-coated tool when compared with its uncoated counterpart. These results pave the way for the use of a low-cost tool, with respect to, polycrystalline diamond for enhancing both tool life and machining productivity in critical sectors fabricating parts out of titanium Ti-6Al-4V alloy. The application of this coating technology can also be extended to the machining of non-ferrous alloys owing to its better adhesion strength.

  8. YAG:Ce/(Gd,Y)AG:Ce dual-layered composite structure ceramic phosphors designed for bright white light-emitting diodes with various CCT.

    Science.gov (United States)

    Hu, Chen; Shi, Yun; Feng, Xiqi; Pan, Yubai

    2015-07-13

    Y3Al5O12:Ce and (Gd,Y)3Al5O12:Ce ceramic phosphors were fabricated by solid-state reaction method under vacuum sintering. Pure garnet phase of these (Gd,Y)AG:Ce ceramics was confirmed by X-ray diffraction (XRD) with Gd content of 0, 25%, 50% and 75%, respectively. The electroluminescent properties of the unpacked and packed LED devices based on YAG:Ce and (Gd,Y)AG:Ce ceramics were measured. The highest luminous efficacy of 130.5 lm/W was achieved by YAG:Ce ceramic phosphor with thickness of 0.4 mm. However, the correlated color temperature (CCT) of the LED device based on it was high due to a lack of red component in the emission light. Therefore, Y3Al5O12:Ce/(Gdx,Y1-x)3Al5O12:Ce dual-layered composite structure ceramics phosphor were designed and fabricated according to the color space chromaticity diagram. In one demonstration, various CCT could be tuned from 3100 K to 3600 K by these dual-layered structure, while the luminous efficacy can reach 109.9 lm/W. The high luminous efficacy and safe warm white light emitted by these dual-layered phosphors made them promising candidate for white LED devices.

  9. Improvement of Energy Capacity with Vitamin C Treated Dual-Layered Graphene-Sulfur Cathodes in Lithium-Sulfur Batteries.

    Science.gov (United States)

    Kim, Jin Won; Ocon, Joey D; Kim, Ho-Sung; Lee, Jaeyoung

    2015-09-07

    A graphene-based cathode design for lithium-sulfur batteries (LSB) that shows excellent electrochemical performance is proposed. The dual-layered cathode is composed of a sulfur active layer and a polysulfide absorption layer, and both layers are based on vitamin C treated graphene oxide at various degrees of reduction. By controlling the degree of reduction of graphene, the dual-layered cathode can increase sulfur utilization dramatically owing to the uniform formation of nanosized sulfur particles, the chemical bonding of dissolved polysulfides on the oxygen-rich sulfur active layer, and the physisorption of free polysulfides on the absorption layer. This approach enables a LSB with a high specific capacity of over 600 mAh gsulfur (-1) after 100 cycles even under a high current rate of 1C (1675 mA gsulfur (-1) ). An intriguing aspect of our work is the synthesis of a high-performance dual-layered cathode by a green chemistry method, which could be a promising approach to LSBs with high energy and power densities.

  10. DVH Analysis of Cobalt-60 treatment plans incorporating a recently developed MLC

    Directory of Open Access Journals (Sweden)

    Gangarapu Sri Krishna

    2016-07-01

    Full Text Available Purpose: The aim of this investigation was to measure the gain in DVH indices when the recently developed MLC was used for Cobalt-60 treatments.Methods: A prototype multileaf collimator (MLC that was retrofitted to telecobalt-60 therapy machine was reported and is currently proposed for clinical trials in our institution. Ten patients’ plans that were previously planned through an ECLIPSE® treatment planning system and were treated with open beams from Cobalt-60 machine were imported into Radiation Oncology Planning System [ROPS] and the dose calculations and dose volume histogram (DVH analysis were performed. The plans were re-planned using the Cobalt-MLC, a feature available in the ROPS planning system. The DVH analysis consisted of conformity index (CI, homogeneity index (HI and conformation number (CN. The results of this study are presented in this paper. The analysis specifically aimed at measuring the gain in these indices when the MLC was compared with open beams.Results: DVH Comparison of ten sites using open and Cobalt MLC fields showed that the use of MLC results in reduced normal tissue dose, while maintaining the GTV dose. Lower value of CI for normal structures was observed demonstrating the sparing of critical organs when MLC was used. The index HI was studied to show the significance of hot spots outside the PTV. Hot spots were observed even with MLC beams for some cases due to less number of fields.Conclusion: It has been demonstrated through DVH analysis that the use of the recently developed MLC for Cobalt Teletherapy machine results in benefit for the treatment of patients.

  11. VARIAN 6EX MLC 叶片的维护及故障维修一例

    Institute of Scientific and Technical Information of China (English)

    王良

    2015-01-01

    目的:探讨 VARIAN 6EX MLC 系统叶片基本保养流程的方式和方法。方法:阐述 MLC 系统叶片维护保养的方法以及注意事项,简单介绍 diagLeafBacklashAll 和 diagLeafPWMTestMlc 两个 MLC 叶片测试代码命令的应用。结果:通过掌握 MLC 系统叶片的保养基本流程,可以避免日常使用中频繁的 MLC 故障报错。结论:保证 MLC 系统叶片的及时保养,能够大大减少维修资金和人力成本。

  12. The serological recognition of the human MLC determinants using a modified cytotoxicity technique.

    Science.gov (United States)

    van Rood, J J; van Leeuwen, A; Keuning, J J; van Oud Alblas, A B

    1975-04-01

    A new approach which presumably recognizes MLC determinants (or at least structures closely linked to MLC and different from the FOUR, AJ and LA series determinants) by serology is described. As the test can be performed within 10 h it could be used to match cadaveric kidney donors for these MLC determinants. Perhaps even more important is the fact that the antibodies detected by this technique could be used to study the immunochemistry of a class of determinants differing from the well known SD determinants.

  13. NeuroAid (MLC601) versus piracetam in the recovery of post-infarct homonymous hemianopsia

    Institute of Scientific and Technical Information of China (English)

    Kavian Ghandehari; Zahra Izadi Mood; Saeed Ebrahimzadeh; David Picard; Yue Zhang

    2011-01-01

    In the clinic, the natural recovery rate of homonymous hemianopsia caused by occipital lobe infarction is low. At present, ideal therapeutic effects of piracetam for improving visual field defects following homonymous hemianopsia do not exist. The present randomized, controlled study compared the effects of NeuroAid (MLC601) versus piracetam for improving visual field defects in post-infarct homonymous hemianopsia patients matched for age and sex. After 3 months of treatment with NeuroAid (MLC601) or piracetam, visual field defects were significantly improved, compared with prior to treatment (P < 0.001). After treatment with MLC601, relative reduction of right and left visual field defects was 45% and 45.7%, respectively, while relative reduction after treatment with piracetam was 32.7% and 30.3%, respectively. These findings suggested that MLC601 was superior to piracetam for reducing visual field defects in homonymous hemianopsia patients.

  14. Monte Carlo implementation, validation, and characterization of a 120 leaf MLC

    Energy Technology Data Exchange (ETDEWEB)

    Fix, Michael K.; Volken, Werner; Frei, Daniel; Frauchiger, Daniel; Born, Ernst J.; Manser, Peter [Division of Medical Radiation Physics, Inselspital and University of Bern, CH-3010 Bern (Switzerland)

    2011-10-15

    Purpose: Recently, the new high definition multileaf collimator (HD120 MLC) was commercialized by Varian Medical Systems providing high resolution in the center section of the treatment field. The aim of this work is to investigate the characteristics of the HD120 MLC using Monte Carlo (MC) methods. Methods: Based on the information of the manufacturer, the HD120 MLC was implemented into the already existing Swiss MC Plan (SMCP). The implementation has been configured by adjusting the physical density and the air gap between adjacent leaves in order to match transmission profile measurements for 6 and 15 MV beams of a Novalis TX. These measurements have been performed in water using gafchromic films and an ionization chamber at an SSD of 95 cm and a depth of 5 cm. The implementation was validated by comparing diamond measured and calculated penumbra values (80%-20%) for different field sizes and water depths. Additionally, measured and calculated dose distributions for a head and neck IMRT case using the DELTA{sup 4} phantom have been compared. The validated HD120 MLC implementation has been used for its physical characterization. For this purpose, phase space (PS) files have been generated below the fully closed multileaf collimator (MLC) of a 40 x 22 cm{sup 2} field size for 6 and 15 MV. The PS files have been analyzed in terms of energy spectra, mean energy, fluence, and energy fluence in the direction perpendicular to the MLC leaves and have been compared with the corresponding data using the well established Varian 80 leaf (MLC80) and Millennium M120 (M120 MLC) MLCs. Additionally, the impact of the tongue and groove design of the MLCs on dose has been characterized. Results: Calculated transmission values for the HD120 MLC are 1.25% and 1.34% in the central part of the field for the 6 and 15 MV beam, respectively. The corresponding ionization chamber measurements result in a transmission of 1.20% and 1.35%. Good agreement has been found for the comparison

  15. Fast motion-including dose error reconstruction for VMAT with and without MLC tracking

    DEFF Research Database (Denmark)

    Ravkilde, Thomas; Keall, Paul J.; Grau, Cai

    2014-01-01

    validate a simple model for fast motion-including dose error reconstruction applicable to intrafractional QA of MLC tracking treatments of moving targets. MLC tracking experiments were performed on a standard linear accelerator with prototype MLC tracking software guided by an electromagnetic transponder...... system. A three-axis motion stage reproduced eight representative tumour trajectories; four lung and four prostate. Low and high modulation 6 MV single-arc volumetric modulated arc therapy treatment plans were delivered for each trajectory with and without MLC tracking, as well as without motion...... for reference. Temporally resolved doses were measured during all treatments using a biplanar dosimeter. Offline, the dose delivered to each of 1069 diodes in the dosimeter was reconstructed with 500 ms temporal resolution by a motion-including pencil beam convolution algorithm developed in-house. The accuracy...

  16. The first clinical implementation of electromagnetic transponder-guided MLC tracking

    Energy Technology Data Exchange (ETDEWEB)

    Keall, Paul J., E-mail: paul.keall@sydney.edu.au; O’Brien, Ricky; Ng, Jin Aun [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006 (Australia); Colvill, Emma [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia and Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065 (Australia); Poulsen, Per Rugaard [Department of Oncology, Aarhus University Hospital, Aarhus 8000, Denmark and Institute of Clinical Medicine, Aarhus University, Aarhus 8000 (Denmark); Eade, Thomas; Kneebone, Andrew; Booth, Jeremy T. [Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065 (Australia)

    2014-02-15

    Purpose: We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre. Methods: An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used. Results: The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V{sub 60}. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V{sub 60} from that planned, even for the small motion. Conclusions: The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy.

  17. Partial transmission block production for real efficient method of block and MLC

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Ji Min; Park, Ju Young; Ju, Sang Kyu; Park, Jong Ho [Dept. of Radiation Oncology, Samsung Medical Center, Sunkyunkwan University, Seoul (Korea, Republic of)

    2004-09-15

    The Vaginal, the urethra, the vulva and anal cancer avoid the many dose to femur head and the additional treatment is necessary in inguinal LN. The partial transmission block to use inguinal LN addition there is to a method which it treats and produce partial transmission block a method and the MLC which to it analyzes. The Inguinal the LN treatment patient partial transmission it used block and the MLC in the object and with solid water phantom with the patient it reappeared the same depth. In order to analyze the error of the junction the EDR2 (Extended dose range, the Kodak and the U.S) it used the Film and it got film scanner it got the beam profile. The partial transmission block and the MLC bias characteristic, accuracy and stability of production for, it shared at hour and comparison it analyzed. The partial the transmission block compares in the MLC and the block production is difficult and production hour also above 1 hours. The custom the block the place where it revises the error of the junction is a difficult problem. If use of the MLC the fabrication will be break and only the periodical calibration of the MLC it will do and it will be able to use easily. The Inguinal there is to LN treatment and partial transmission block and the MLC there is efficiency of each one but there is a place where the junction of block for partial transmission block the production hour is caught long and it fixes and a point where the control of the block is difficult. Like this problem it transfers with the MLC and if it treats, it means the effective treatment will be possible.

  18. Yeast myosin light chain, Mlc1p, interacts with both IQGAP and class II myosin to effect cytokinesis.

    Science.gov (United States)

    Boyne, J R; Yosuf, H M; Bieganowski, P; Brenner, C; Price, C

    2000-12-01

    MLC1 (myosin light chain) acts as a dosage suppressor of a temperature sensitive mutation in the gene encoding the S. cerevisiae IQGAP protein. Both proteins localize to the bud neck in mitosis although Mlc1p localisation precedes Iqg1p. Mlc1p is also found at the incipient bud site in G(1) and the growing bud tip during S and G(2) phases of the cell cycle. A dominant negative GST-Mlc1p fusion protein specifically blocks cytokinesis and prevents Iqg1p localisation to the bud neck, as does depletion of Mlc1p. These data support a direct interaction between the two proteins and immunoprecipitation experiments confirm this prediction. Mlc1p is also shown to interact with the class II conventional myosin (Myo1p). All three proteins form a complex, however, the interaction between Mlc1p and Iqg1p can be separated from the Mlc1p/Myo1p interaction. Mlc1p localisation and maintenance at the bud neck is independent of actin, Myo1p and Iqg1p. It is proposed that Mlc1p therefore functions to recruit Iqg1p and in turn actin to the actomyosin ring and that it is also required for Myo1p function during ring contraction.

  19. Detecting MLC errors in stereotactic radiotherapy plans with a liquid filled ionization chamber array.

    Science.gov (United States)

    O'Connor, Patrick; Seshadri, Venkatakrisnan; Charles, Paul

    2016-03-01

    Quality assurance of stereotactic radiotherapy demands the use of equipment with the highest resolution and sensitivity available. This study examines the sensitivity of a commercially available liquid-filled ionization chamber array--the Octavius 1000 SRS (PTW, Frieburg, Germany) for detecting small (sub-millimetre) multi-leaf collimator (MLC) alignment errors in static square fields (side length 16-40 mm). Furthermore, the effectiveness of detecting small MLC errors in clinical stereotactic radiotherapy patient plans using the device was also evaluated. The commonly used gamma pass rate metric (of the measurements compared with treatment planning system generated results) was used. The gamma pass rates were then evaluated as a function of MLC position error (MLC error size 0.1-2.5 mm). The detector array exhibited a drop in pass rate between plans without error and those which had MLC errors induced. For example a drop in pass rate of 4.5% (gamma criteria 3%, 1 mm) was observed when a 0.8 mm error was introduced into a 16 mm square field. Furthermore the drop in pass rate increased as the MLC position error increased. This study showed that the Octavius 1000 SRS array could be a useful tool for applications requiring the detection of small geometric delivery uncertainties.

  20. SU-E-T-418: Explore the Sensitive of the Planar Quality Assurance to the MLC Error with Different Beam Complexity in Intensity-Modulate Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J; Peng, J; Xie, J; Hu, W [Fudan university shanghai cancer center, Shanghai (China)

    2015-06-15

    Purpose: The purpose of this study is to investigate the sensitivity of the planar quality assurance to MLC errors with different beam complexities in intensity-modulate radiation therapy. Methods: sixteen patients’ planar quality assurance (QA) plans in our institution were enrolled in this study, including 10 dynamic MLC (DMLC) IMRT plans measured by Portal Dosimetry and 6 static MLC (SMLC) IMRT plans measured by Mapcheck. The gamma pass rate was calculated using vender’s software. The field numbers were 74 and 40 for DMLC and SMLC, respectively. A random error was generated and introduced to these fields. The modified gamma pass rate was calculated by comparing the original measured fluence and modified fields’ fluence. A decreasing gamma pass rate was acquired using the original gamma pass rate minus the modified gamma pass rate. Eight complexity scores were calculated in MATLAB based on the fluence and MLC sequence of these fields. The complexity scores include fractal dimension, monitor unit of field, modulation index, fluence map complexity, weighted average of field area, weighted average of field perimeter, and small aperture ratio ( <5cm{sup 2} and <50cm{sup 2}). The Spearman’s rank correlation coefficient was implemented to analyze the correlation between these scores and decreasing gamma rate. Results: The relation between the decreasing gamma pass rate and field complexity was insignificant for most complexity scores. The most significant complexity score was fluence map complexity for SMLC, which have ρ =0.4274 (p-value=0.0063). For DMLC, the most significant complex score was fractal dimension, which have ρ=−0.3068 (p-value=0.0081). Conclusions: According to the primarily Result of this study, the sensitivity gamma pass rate was not strongly relate to the field complexity.

  1. Megalencephalic leukoencephalopathy with subcortical cysts protein-1 modulates endosomal pH and protein trafficking in astrocytes: relevance to MLC disease pathogenesis.

    Science.gov (United States)

    Brignone, Maria S; Lanciotti, Angela; Visentin, Sergio; De Nuccio, Chiara; Molinari, Paola; Camerini, Serena; Diociaiuti, Marco; Petrini, Stefania; Minnone, Gaetana; Crescenzi, Marco; Laudiero, Luisa Bracci; Bertini, Enrico; Petrucci, Tamara C; Ambrosini, Elena

    2014-06-01

    Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare leukodystrophy caused by mutations in the gene encoding MLC1, a membrane protein mainly expressed in astrocytes in the central nervous system. Although MLC1 function is unknown, evidence is emerging that it may regulate ion fluxes. Using biochemical and proteomic approaches to identify MLC1 interactors and elucidate MLC1 function we found that MLC1 interacts with the vacuolar ATPase (V-ATPase), the proton pump that regulates endosomal acidity. Because we previously showed that in intracellular organelles MLC1 directly binds Na, K-ATPase, which controls endosomal pH, we studied MLC1 endosomal localization and trafficking and MLC1 effects on endosomal acidity and function using human astrocytoma cells overexpressing wild-type (WT) MLC1 or MLC1 carrying pathological mutations. We found that WT MLC1 is abundantly expressed in early (EEA1(+), Rab5(+)) and recycling (Rab11(+)) endosomes and uses the latter compartment to traffic to the plasma membrane during hyposmotic stress. We also showed that WT MLC1 limits early endosomal acidification and influences protein trafficking in astrocytoma cells by stimulating protein recycling, as revealed by FITC-dextran measurement of endosomal pH and transferrin protein recycling assay, respectively. WT MLC1 also favors recycling to the plasma-membrane of the TRPV4 cation channel which cooperates with MLC1 to activate calcium influx in astrocytes during hyposmotic stress. Although MLC disease-causing mutations differentially affect MLC1 localization and trafficking, all the mutated proteins fail to influence endosomal pH and protein recycling. This study demonstrates that MLC1 modulates endosomal pH and protein trafficking suggesting that alteration of these processes contributes to MLC pathogenesis. Copyright © 2014. Published by Elsevier Inc.

  2. Automatic detection of MLC relative position errors for VMAT using the EPID-based picket fence test

    Science.gov (United States)

    Christophides, Damianos; Davies, Alex; Fleckney, Mark

    2016-12-01

    Multi-leaf collimators (MLCs) ensure the accurate delivery of treatments requiring complex beam fluences like intensity modulated radiotherapy and volumetric modulated arc therapy. The purpose of this work is to automate the detection of MLC relative position errors  ⩾0.5 mm using electronic portal imaging device-based picket fence tests and compare the results to the qualitative assessment currently in use. Picket fence tests with and without intentional MLC errors were measured weekly on three Varian linacs. The picket fence images analysed covered a time period ranging between 14-20 months depending on the linac. An algorithm was developed that calculated the MLC error for each leaf-pair present in the picket fence images. The baseline error distributions of each linac were characterised for an initial period of 6 months and compared with the intentional MLC errors using statistical metrics. The distributions of median and one-sample Kolmogorov-Smirnov test p-value exhibited no overlap between baseline and intentional errors and were used retrospectively to automatically detect MLC errors in routine clinical practice. Agreement was found between the MLC errors detected by the automatic method and the fault reports during clinical use, as well as interventions for MLC repair and calibration. In conclusion the method presented provides for full automation of MLC quality assurance, based on individual linac performance characteristics. The use of the automatic method has been shown to provide early warning for MLC errors that resulted in clinical downtime.

  3. Dose domain regularization of MLC leaf patterns for highly complex IMRT plans

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dan; Yu, Victoria Y.; Ruan, Dan; Cao, Minsong; Low, Daniel A.; Sheng, Ke, E-mail: ksheng@mednet.ucla.edu [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095 (United States); O’Connor, Daniel [Department of Mathematics, University of California Los Angeles, Los Angeles, California 90095 (United States)

    2015-04-15

    Purpose: The advent of automated beam orientation and fluence optimization enables more complex intensity modulated radiation therapy (IMRT) planning using an increasing number of fields to exploit the expanded solution space. This has created a challenge in converting complex fluences to robust multileaf collimator (MLC) segments for delivery. A novel method to regularize the fluence map and simplify MLC segments is introduced to maximize delivery efficiency, accuracy, and plan quality. Methods: In this work, we implemented a novel approach to regularize optimized fluences in the dose domain. The treatment planning problem was formulated in an optimization framework to minimize the segmentation-induced dose distribution degradation subject to a total variation regularization to encourage piecewise smoothness in fluence maps. The optimization problem was solved using a first-order primal-dual algorithm known as the Chambolle-Pock algorithm. Plans for 2 GBM, 2 head and neck, and 2 lung patients were created using 20 automatically selected and optimized noncoplanar beams. The fluence was first regularized using Chambolle-Pock and then stratified into equal steps, and the MLC segments were calculated using a previously described level reducing method. Isolated apertures with sizes smaller than preset thresholds of 1–3 bixels, which are square units of an IMRT fluence map from MLC discretization, were removed from the MLC segments. Performance of the dose domain regularized (DDR) fluences was compared to direct stratification and direct MLC segmentation (DMS) of the fluences using level reduction without dose domain fluence regularization. Results: For all six cases, the DDR method increased the average planning target volume dose homogeneity (D95/D5) from 0.814 to 0.878 while maintaining equivalent dose to organs at risk (OARs). Regularized fluences were more robust to MLC sequencing, particularly to the stratification and small aperture removal. The maximum and

  4. Dual-layer write-once media for 1x-4x-speed recording based on Blu-ray Disc format

    Science.gov (United States)

    Uno, Mayumi; Akiyama, Tetsuya; Kitaura, Hideki; Kojima, Rie; Nishiuchi, Kenichi; Yamada, Noboru

    2003-09-01

    We have developed dual-layer write-once media with Te-O-Pd based recording films on Blu-ray (BD) format. Recording capacity was 50GB with dual layers on a disk of 120mm in diameter. Rear and Front layers showed jitters of 5.8% and 7.7% at 1x speed, and 6.0% and 8.0% at 2x speed, respectively, which were good enough to satisfy the BD format. Evaluations were carried out with blue-violet laser of 405nm wavelength, objective lens NA of 0.85. Recording linear velocities were 4.92m/s at BD 1x (36Mbps), and 9.84m/s at BD 2x (72Mbps). Characteristics at 4x speed recording were also examined, and it was revealed that carrier to niose ratio at high recording linear velocity of 19.7m/s, which corresponds to BD 4x (144Mbps), was alomst as same as those of 1x and 2x. Recording mechanism was discussed and proposed a model that Te-O-Pd films were not crystallized directly through solid process, but crystallized through melting.

  5. Dual-Layer Oxidation-Protective Plasma-Sprayed SiC-ZrB2/Al2O3-Carbon Nanotube Coating on Graphite

    Science.gov (United States)

    Ariharan, S.; Sengupta, Pradyut; Nisar, Ambreen; Agnihotri, Ankur; Balaji, N.; Aruna, S. T.; Balani, Kantesh

    2017-02-01

    Graphite is used in high-temperature gas-cooled reactors because of its outstanding irradiation performance and corrosion resistance. To restrict its high-temperature (>873 K) oxidation, atmospheric-plasma-sprayed SiC-ZrB2-Al2O3-carbon nanotube (CNT) dual-layer coating was deposited on graphite substrate in this work. The effect of each layer was isolated by processing each component of the coating via spark plasma sintering followed by isothermal kinetic studies. Based on isothermal analysis and the presence of high residual thermal stress in the oxide scale, degradation appeared to be more severe in composites reinforced with CNTs. To avoid the complexity of analysis of composites, the high-temperature activation energy for oxidation was calculated for the single-phase materials only, yielding values of 11.8, 20.5, 43.5, and 4.5 kJ/mol for graphite, SiC, ZrB2, and CNT, respectively, with increased thermal stability for ZrB2 and SiC. These results were then used to evaluate the oxidation rate for the composites analytically. This study has broad implications for wider use of dual-layer (SiC-ZrB2/Al2O3) coatings for protecting graphite crucibles even at temperatures above 1073 K.

  6. Phosphorylated Myosin Light Chain 2 (p-MLC2) as a Molecular Marker of Antemortem Coronary Artery Spasm

    Science.gov (United States)

    Li, Liliang; Li, Yuhua; Lin, Junyi; Jiang, Jieqing; He, Meng; Sun, Daming; Zhao, Ziqin; Shen, Yiwen; Xue, Aimin

    2016-01-01

    Background It is not uncommon that only mild coronary artery stenosis is grossly revealed after a system autopsy. While coronary artery spasm (CAS) is the suspected mechanism of these deaths, no specific biomarker has been identified to suggest antemortem CAS. Material/Methods To evaluate the potential of using phosphorylated myosin light chain 2 (p-MLC2) as a diagnostic marker of antemortem CAS, human vascular smooth muscle cells (VSMCs) were cultured and treated with common vasoconstrictors, including prostaglandins F2α (PGF2α), acetylcholine (ACh), and 5-hydroxy tryptamine (5-HT). The p-MLC2 level was examined in the cultured cells using Western blot analysis and in a rat model of spasm provocation tests using immunohistochemistry (IHC). Effects of increased p-MLC2 level on VSMCs contractile activities were assessed in vitro using confocal immunofluorescence assay. Four fatal cases with known antemortem CAS were collected and subject to p-MLC2 detection. Results The p-MLC2 was significantly increased in VSMCs after treatments with vasoconstrictors and in the spasm provocation tests. Myofilament was well-organized and densely stained in VSMCs with high p-MLC2 level, but disarrayed in VSMCs with low p-MLC2 level. Three of the 4 autopsied cases showed strongly positive staining of p-MLC2 at the stenosed coronary segment and the adjacent interstitial small arteries. The fourth case was autopsied at the 6th day after death and showed negative-to-mild positive staining of p-MLC2. Conclusions p-MLC2 might be a useful marker for diagnosis of antemortem CAS. Autopsy should be performed as soon as possible to collect coronary arteries for detection of p-MLC2. PMID:27643564

  7. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC) leaves for volumetric modulated arc therapy (VMAT).

    Science.gov (United States)

    Xu, Zhengzheng; Wang, Iris Z; Kumaraswamy, Lalith K; Podgorsak, Matthew B

    2016-03-01

    This study is to report 1) the sensitivity of intensity modulated radiation therapy (IMRT) QA method for clinical volumetric modulated arc therapy (VMAT) plans with multi-leaf collimator (MLC) leaf errors that will not trigger MLC interlock during beam delivery; 2) the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery. Eleven VMAT plans were selected and modified using an in-house developed software. For each control point of a VMAT arc, MLC leaves with the highest speed (1.87-1.95 cm/s) were set to move at the maximal allowable speed (2.3 cm/s), which resulted in a leaf position difference of less than 2 mm. The modified plans were considered as 'standard' plans, and the original plans were treated as the 'slowing MLC' plans for simulating 'standard' plans with leaves moving at relatively lower speed. The measurement of each 'slowing MLC' plan using MapCHECK®2 was compared with calculated planar dose of the 'standard' plan with respect to absolute dose Van Dyk distance-to-agreement (DTA) comparisons using 3%/3 mm and 2%/2 mm criteria. All 'slowing MLC' plans passed the 90% pass rate threshold using 3%/3 mm criteria while one brain and three anal VMAT cases were below 90% with 2%/2 mm criteria. For ten out of eleven cases, DVH comparisons between 'standard' and 'slowing MLC' plans demonstrated minimal dosimetric changes in targets and organs-at-risk. For highly modulated VMAT plans, pass rate threshold (90%) using 3%/3mm criteria is not sensitive in detecting MLC leaf errors that will not trigger the MLC leaf interlock. However, the consequential effects of non-beam hold MLC errors on target and OAR doses are negligible, which supports the reliability of current patient-specific IMRT quality assurance (QA) method for VMAT plans.

  8. Fast motion-including dose error reconstruction for VMAT with and without MLC tracking

    DEFF Research Database (Denmark)

    Ravkilde, Thomas; Keall, Paul J.; Grau, Cai

    2014-01-01

    of the algorithm for reconstruction of dose and motion-induced dose errors throughout the tracking and non-tracking beam deliveries was quantified. Doses were reconstructed with a mean dose difference relative to the measurements of -0.5% (5.5% standard deviation) for cumulative dose. More importantly, the root......-mean-square deviation between reconstructed and measured motion-induced 3%/3 mm γ failure rates (dose error) was 2.6%. The mean computation time for each calculation of dose and dose error was 295 ms. The motion-including dose reconstruction allows accurate temporal and spatial pinpointing of errors in absorbed dose...... validate a simple model for fast motion-including dose error reconstruction applicable to intrafractional QA of MLC tracking treatments of moving targets. MLC tracking experiments were performed on a standard linear accelerator with prototype MLC tracking software guided by an electromagnetic transponder...

  9. Multiple linear combination (MLC) regression tests for common variants adapted to linkage disequilibrium structure

    Science.gov (United States)

    Yoo, Yun Joo; Sun, Lei; Poirier, Julia G.; Paterson, Andrew D.

    2016-01-01

    ABSTRACT By jointly analyzing multiple variants within a gene, instead of one at a time, gene‐based multiple regression can improve power, robustness, and interpretation in genetic association analysis. We investigate multiple linear combination (MLC) test statistics for analysis of common variants under realistic trait models with linkage disequilibrium (LD) based on HapMap Asian haplotypes. MLC is a directional test that exploits LD structure in a gene to construct clusters of closely correlated variants recoded such that the majority of pairwise correlations are positive. It combines variant effects within the same cluster linearly, and aggregates cluster‐specific effects in a quadratic sum of squares and cross‐products, producing a test statistic with reduced degrees of freedom (df) equal to the number of clusters. By simulation studies of 1000 genes from across the genome, we demonstrate that MLC is a well‐powered and robust choice among existing methods across a broad range of gene structures. Compared to minimum P‐value, variance‐component, and principal‐component methods, the mean power of MLC is never much lower than that of other methods, and can be higher, particularly with multiple causal variants. Moreover, the variation in gene‐specific MLC test size and power across 1000 genes is less than that of other methods, suggesting it is a complementary approach for discovery in genome‐wide analysis. The cluster construction of the MLC test statistics helps reveal within‐gene LD structure, allowing interpretation of clustered variants as haplotypic effects, while multiple regression helps to distinguish direct and indirect associations. PMID:27885705

  10. Low-Dose Lithium Stabilizes Human Endothelial Barrier by Decreasing MLC Phosphorylation and Universally Augments Cholinergic Vasorelaxation Capacity in a Direct Manner

    Science.gov (United States)

    Bosche, Bert; Molcanyi, Marek; Rej, Soham; Doeppner, Thorsten R.; Obermann, Mark; Müller, Daniel J.; Das, Anupam; Hescheler, Jürgen; Macdonald, R. Loch; Noll, Thomas; Härtel, Frauke V.

    2016-01-01

    Lithium at serum concentrations up to 1 mmol/L has been used in patients suffering from bipolar disorder for decades and has recently been shown to reduce the risk for ischemic stroke in these patients. The risk for stroke and thromboembolism depend not only on cerebral but also on general endothelial function and health; the entire endothelium as an organ is therefore pathophysiologically relevant. Regardless, the knowledge about the direct impact of lithium on endothelial function remains poor. We conducted an experimental study using lithium as pharmacologic pretreatment for murine, porcine and human vascular endothelium. We predominantly investigated endothelial vasorelaxation capacities in addition to human basal and dynamic (thrombin-/PAR-1 receptor agonist-impaired) barrier functioning including myosin light chain (MLC) phosphorylation (MLC-P). Low-dose therapeutic lithium concentrations (0.4 mmol/L) significantly augment the cholinergic endothelium-dependent vasorelaxation capacities of cerebral and thoracic arteries, independently of central and autonomic nerve system influences. Similar concentrations of lithium (0.2–0.4 mmol/L) significantly stabilized the dynamic thrombin-induced and PAR-1 receptor agonist-induced permeability of human endothelium, while even the basal permeability appeared to be stabilized. The lithium-attenuated dynamic permeability was mediated by a reduced endothelial MLC-P known to be followed by a lessening of endothelial cell contraction and paracellular gap formation. The well-known lithium-associated inhibition of inositol monophosphatase/glycogen synthase kinase-3-β signaling-pathways involving intracellular calcium concentrations in neurons seems to similarly occur in endothelial cells, too, but with different down-stream effects such as MLC-P reduction. This is the first study discovering low-dose lithium as a drug directly stabilizing human endothelium and ubiquitously augmenting cholinergic endothelium

  11. Independent dose calculation of the Tps Iplan in radiotherapy conformed with MLC; Calculo independiente de dosis del TPS Iplan en radioterapia conformada con MLC

    Energy Technology Data Exchange (ETDEWEB)

    Adrada, A.; Tello, Z.; Medina, L.; Garrigo, E.; Venencia, D., E-mail: jorge.alberto.adrada@gmail.com [Instituto Privado de Radioterapia, Obispo Oro 423, X5000BFI Cordoba (Argentina)

    2014-08-15

    The systems utilization of independent dose calculation in three dimensional-Conformal Radiation Therapy (3D-Crt) treatments allows a direct verification of the treatments times. The utilization of these systems allows diminishing the probability of errors occurrence generated by the treatment planning system (Tps), allowing a detailed analysis of the dose to delivering and review of the normalization point (Np) or prescription. The independent dose calculation is realized across the knowledge of dosimetric parameters of the treatment machine and particular characteristics of every individual field. The aim of this work is develops a calculation system of punctual doses for isocentric fields conformed with multi-leaf collimation systems (MLC), where the dose calculation is in conformity with the suggested ones by ICRU Report No. 42, 1987. Calculation software was realized in C ++ under a free platform of programming (Code::Blocks). The system uses files in format Rtp, exported from the Tps to systems of record and verification (Lantis). This file contains detailed information of the dose, Um, position of the MLC sheets and collimators for every field of treatment. The size of equivalent field is obtained from the positions of every sheet; the effective depth of calculation can be introduced from the dosimetric report of the Tps or automatically from the DFS of the field. The 3D coordinates of the isocenter and the Np for the treatment plan must be introduced manually. From this information the system looks the dosimetric parameters and calculates the Um. The calculations were realized in two accelerators a NOVALIS Tx (Varian) with 120 sheets of high definition (hd-MLC) and a PRIMUS Optifocus (Siemens) with 82 sheets. 705 patients were analyzed for a total of 1082, in plans made for both equipment s, the average uncertainty with regard to the calculation of the Tps is-0.43% ± 2.42% in a range between [-7.90 %, 7.50 %]. The major uncertainty was in Np near of the

  12. 6 MV dosimetric characterization of the 160 MLC, the new Siemens multileaf collimator.

    Science.gov (United States)

    Tacke, Martin B; Nill, Simeon; Häring, Peter; Oelfke, Uwe

    2008-05-01

    New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC, Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d(max) = 15 mm with standard 100 x 100 mm2 fields is 4.1 +/- 0.5 mm for the central range and increases to 4.9 +/- 1.3 mm for the entire field range of 400 x 400 mm2. The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9 +/- 0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to precision and dose

  13. Molecular In Vivo Imaging Using a Noninvasive Cardiac-Specific MLC-2v Promoter Driven Dual-Gene Recombinant Lentivirus Monitoring System.

    Directory of Open Access Journals (Sweden)

    Miao Zhang

    Full Text Available Our study aimed to demonstrate the feasibility of using the sodium/iodide symporter (NIS to monitor vascular endothelial growth factor (VEGF165 expression in vivo.We constructed a recombinant lentivirus plasmid with the MLC-2v promoter driving the sodium/iodide symporter (NIS reporter gene linked to the VEGF165 gene. Expression of NIS and VEGF gene were identified by Western blot. On days 2 and 54, 99mTc-MIBI imaging was used to evaluate changes in myocardial ischemia. Noninvasive 125I micro-SPECT/CT imaging was used to assess the expression of NIS reporter gene dynamically over the next 2 months.Western blot analysis showed that both NIS and VEGF165 were highly expressed in rat cardiomyoblast H9C2 cells transduced with Lenti-MLC-2v-NIS--VEGF165. 125I micro-SPECT/CT reporter imaging showed higher uptake in mouse myocardium transduced with Lenti-MLC-2v-VEGF165-IRES-NIS. NIS expression peaked on day 1 after transduction followed by a progressive decline to negligible levels by day 21. On day 1, mean 125I activity value in group 1 was higher than that in group 2 (P 0.05. In group 1 (test group, 99mTc-MIBI SPECT/CT revealed improvements in perfusion and wall thickening in the apical anterior wall. Mean IOD values of NIS and CD34 were significantly higher in group 1 than group 3 (P<0.05. Our study proved mean I-125 uptake was significantly correlated with mean IOD value of NIS and CD34 (P<0.05.This study demonstrates the feasibility of using the NIS gene to monitor VEGF165 expression in a mouse myocardial ischemia model.

  14. Unusual 5'-regulatory structure and regulation of the murine Mlc1 gene: Lack of promoter-specific functional elements

    Directory of Open Access Journals (Sweden)

    Darja Henseler

    2011-10-01

    Full Text Available Normal 0 21 false false false MicrosoftInternetExplorer4 The MLC1 gene is involved in an autosomal recessive neurological disorder, megalencephalic leucoencephalopathy with subcortical cysts (MLC, which is characterized by macrocephaly during the first year of life and swollen white matter (leucoencephaly. Variants of MLC1 have also been associated with psychiatric disorders such as schizophrenia, major depression and bipolar disorder. Currently, little is known about the encoded protein (MLC1. Judging from its similarity to other known proteins, it may serve as a trans-membrane transporter. However, the function of the encoded protein and its gene regulation has not been investigated successfully so far. We investigated the 5’ region of the murine Mlc1 with respect to regulatory elements for gene expression. A promoter search and an in silico analysis were conducted. Luciferase reporter gene constructs with potential promoter regions were created to study promoter activity in vitro. We found two alternative first exons for the murine Mlc1 but were not able to detect any promoter activity for the investigated reporter gene constructs in different cell lines, thus pointing to the presence of essential cis-acting elements far outside of the region. In silico analysis indicated an uncommon promoter structure for Mlc1, with CCAAT-boxes representing the only noticeable elements.

  15. Involvement of caveolin-1 in low shear stress-induced breast cancer cell motility and adhesion: Roles of FAK/Src and ROCK/p-MLC pathways.

    Science.gov (United States)

    Xiong, Niya; Li, Shun; Tang, Kai; Bai, Hongxia; Peng, Yueting; Yang, Hong; Wu, Chunhui; Liu, Yiyao

    2017-01-01

    Tumor cells translocating to distant sites are subjected to hemodynamic shear forces during their passage in the blood vessels. Low shear stress (LSS) plays a critical role in the regulation of various aspects of tumor cells functions, including motility and adhesion. Beyond its structural role, caveolin-1 (Cav-1), the important component of caveolae, represents a modulator of several cancer-associated functions as tumor progression and metastasis. However, the role of Cav-1 in regulating tumor cells response to shear stress remains poorly explored. Here, we characterized the role of LSS and Cav-1 in mediating cell motility and adhesion on human breast carcinoma MDA-MB-231 cells. We first showed that LSS exposure promoted cell polarity and focal adhesion (FA) dynamics, thus indicating elevated cell migration. Silencing of Cav-1 leaded to a significantly lower formation of stress fibers. However, LSS exposure was able to rescue it via the alteration of actin-associated proteins expression, including ROCK, p-MLC, cofilin and filamin A. Time-lapse migration assay indicated that Cav-1 expression fostered MDA-MB-231 cells motility and LSS triggered cells to rapidly generate new lamellipodia. Furthermore, Cav-1 and LSS significantly influenced cell adhesion. Taken together, our findings provide insights into mechanisms underlying LSS triggered events mediated by downstream Cav-1, including FAK/Src and ROCK/p-MLC pathways, involved in the reorganization of the cytoskeleton, cell motility, FA dynamics and breast cancer cell adhesion.

  16. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC) leaves for volumetric modulated arc therapy (VMAT)

    OpenAIRE

    2016-01-01

    Background This study is to report 1) the sensitivity of intensity modulated radiation therapy (IMRT) QA method for clinical volumetric modulated arc therapy (VMAT) plans with multi-leaf collimator (MLC) leaf errors that will not trigger MLC interlock during beam delivery; 2) the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery. Materials and methods. Eleven VMAT plans were selected and modified using an in-house developed software. For each control point of a...

  17. Heterologous expression of MlcE in Saccharomyces cerevisiae provides resistance to natural and semi-synthetic statins

    DEFF Research Database (Denmark)

    Ley, Ana; Coumou, Hilde Cornelijne; Frandsen, Rasmus John Normand

    2015-01-01

    -encoding gene mlcE from the mevastatin-producing Penicillium citrinum into the S. cerevisiae genome. The resulting strain showed increased resistance to both natural statins (mevastatin and lovastatin) and semi-synthetic statin (simvastatin) when compared to the wild type strain. Expression of RFP-tagged mlc......E showed that MlcE is localized to the yeast plasma and vacuolar membranes. We provide a possible engineering strategy for improvement of future yeast based production of natural and semi-synthetic statins....

  18. Development and evaluation of a LOR-based image reconstruction with 3D system response modeling for a PET insert with dual-layer offset crystal design

    Science.gov (United States)

    Zhang, Xuezhu; Stortz, Greg; Sossi, Vesna; Thompson, Christopher J.; Retière, Fabrice; Kozlowski, Piotr; Thiessen, Jonathan D.; Goertzen, Andrew L.

    2013-12-01

    In this study we present a method of 3D system response calculation for analytical computer simulation and statistical image reconstruction for a magnetic resonance imaging (MRI) compatible positron emission tomography (PET) insert system that uses a dual-layer offset (DLO) crystal design. The general analytical system response functions (SRFs) for detector geometric and inter-crystal penetration of coincident crystal pairs are derived first. We implemented a 3D ray-tracing algorithm with 4π sampling for calculating the SRFs of coincident pairs of individual DLO crystals. The determination of which detector blocks are intersected by a gamma ray is made by calculating the intersection of the ray with virtual cylinders with radii just inside the inner surface and just outside the outer-edge of each crystal layer of the detector ring. For efficient ray-tracing computation, the detector block and ray to be traced are then rotated so that the crystals are aligned along the X-axis, facilitating calculation of ray/crystal boundary intersection points. This algorithm can be applied to any system geometry using either single-layer (SL) or multi-layer array design with or without offset crystals. For effective data organization, a direct lines of response (LOR)-based indexed histogram-mode method is also presented in this work. SRF calculation is performed on-the-fly in both forward and back projection procedures during each iteration of image reconstruction, with acceleration through use of eight-fold geometric symmetry and multi-threaded parallel computation. To validate the proposed methods, we performed a series of analytical and Monte Carlo computer simulations for different system geometry and detector designs. The full-width-at-half-maximum of the numerical SRFs in both radial and tangential directions are calculated and compared for various system designs. By inspecting the sinograms obtained for different detector geometries, it can be seen that the DLO crystal

  19. Typing for MLC determinants using lymphocytes from cousin-marriage offspring as typing cells.

    Science.gov (United States)

    Singal, D P; Villanueva, R; Naipaul, N

    1975-07-01

    A first cousin marriage family with three children was studied. One sibling (AW) was homozygous for W32.W10. When used as stimulator in one way MLC, AW elicited a very low response in family members possessing this haplotype. Serologically identical sibling and father combination showed bidirectional non-stimulation in one way MLC. Therefore, AW is assumed to be homozygous not only for SD antigens, but also for LD determinants which we call LD W10a. Among the 43 unrelated individuals tested with AW, an association between LD W10a and W10 antigen of the second HL-A locus was observed. Of 12 W10 positive individuals tested, five carry this allele as compared to one out of 31 W10 negative individuals. The data suggest a strong linkage disequilibrium between the FOUR locus determinant W10 and LD determinant LD W10a.

  20. Real-time auto-adaptive margin generation for MLC-tracked radiotherapy

    Science.gov (United States)

    Glitzner, M.; Fast, M. F.; de Senneville, B. Denis; Nill, S.; Oelfke, U.; Lagendijk, J. J. W.; Raaymakers, B. W.; Crijns, S. P. M.

    2017-01-01

    In radiotherapy, abdominal and thoracic sites are candidates for performing motion tracking. With real-time control it is possible to adjust the multileaf collimator (MLC) position to the target position. However, positions are not perfectly matched and position errors arise from system delays and complicated response of the electromechanic MLC system. Although, it is possible to compensate parts of these errors by using predictors, residual errors remain and need to be compensated to retain target coverage. This work presents a method to statistically describe tracking errors and to automatically derive a patient-specific, per-segment margin to compensate the arising underdosage on-line, i.e. during plan delivery. The statistics of the geometric error between intended and actual machine position are derived using kernel density estimators. Subsequently a margin is calculated on-line according to a selected coverage parameter, which determines the amount of accepted underdosage. The margin is then applied onto the actual segment to accommodate the positioning errors in the enlarged segment. The proof-of-concept was tested in an on-line tracking experiment and showed the ability to recover underdosages for two test cases, increasing {{V}90 %} in the underdosed area about 47 % and 41 % , respectively. The used dose model was able to predict the loss of dose due to tracking errors and could be used to infer the necessary margins. The implementation had a running time of 23 ms which is compatible with real-time requirements of MLC tracking systems. The auto-adaptivity to machine and patient characteristics makes the technique a generic yet intuitive candidate to avoid underdosages due to MLC tracking errors.

  1. Inhibition of MLC phosphorylation restricts replication of influenza virus--a mechanism of action for anti-influenza agents.

    Directory of Open Access Journals (Sweden)

    Mehran Haidari

    Full Text Available Influenza A viruses are a severe threat worldwide, causing large epidemics that kill thousands every year. Prevention of influenza infection is complicated by continuous viral antigenic changes. Newer anti-influenza agents include MEK/ERK and protein kinase C inhibitors; however, the downstream effectors of these pathways have not been determined. In this study, we identified a common mechanism for the inhibitory effects of a significant group of anti-influenza agents. Our studies showed that influenza infection activates a series of signaling pathways that converge to induce myosin light chain (MLC phosphorylation and remodeling of the actin cytoskeleton. Inhibiting MLC phosphorylation by blocking RhoA/Rho kinase, phospholipase C/protein kinase C, and HRas/Raf/MEK/ERK pathways with the use of genetic or chemical manipulation leads to the inhibition of influenza proliferation. In contrast, the induction of MLC phosphorylation enhances influenza proliferation, as does activation of the HRas/Raf/MEK/ERK signaling pathway. This effect is attenuated by inhibiting MLC phosphorylation. Additionally, in intracellular trafficking studies, we found that the nuclear export of influenza ribonucleoprotein depends on MLC phosphorylation. Our studies provide evidence that modulation of MLC phosphorylation is an underlying mechanism for the inhibitory effects of many anti-influenza compounds.

  2. The first patient treatment of electromagnetic-guided real time adaptive radiotherapy using MLC tracking for lung SABR.

    Science.gov (United States)

    Booth, Jeremy T; Caillet, Vincent; Hardcastle, Nicholas; O'Brien, Ricky; Szymura, Kathryn; Crasta, Charlene; Harris, Benjamin; Haddad, Carol; Eade, Thomas; Keall, Paul J

    2016-10-01

    Real time adaptive radiotherapy that enables smaller irradiated volumes may reduce pulmonary toxicity. We report on the first patient treatment of electromagnetic-guided real time adaptive radiotherapy delivered with MLC tracking for lung stereotactic ablative body radiotherapy. A clinical trial was developed to investigate the safety and feasibility of MLC tracking in lung. The first patient was an 80-year old man with a single left lower lobe lung metastasis to be treated with SABR to 48Gy in 4 fractions. In-house software was integrated with a standard linear accelerator to adapt the treatment beam shape and position based on electromagnetic transponders implanted in the lung. MLC tracking plans were compared against standard ITV-based treatment planning. MLC tracking plan delivery was reconstructed in the patient to confirm safe delivery. Real time adaptive radiotherapy delivered with MLC tracking compared to standard ITV-based planning reduced the PTV by 41% (18.7-11cm(3)) and the mean lung dose by 30% (202-140cGy), V20 by 35% (2.6-1.5%) and V5 by 9% (8.9-8%). An emerging technology, MLC tracking, has been translated into the clinic and used to treat lung SABR patients for the first time. This milestone represents an important first step for clinical real-time adaptive radiotherapy that could reduce pulmonary toxicity in lung radiotherapy. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  3. Fast leaf-fitting with generalized underdose/overdose constraints for real-time MLC tracking

    Science.gov (United States)

    Ruan, Dan; Sawant, Amit

    2016-01-01

    Purpose: Real-time multileaf collimator (MLC) tracking is a promising approach to the management of intrafractional tumor motion during thoracic and abdominal radiotherapy. MLC tracking is typically performed in two steps: transforming a planned MLC aperture in response to patient motion and refitting the leaves to the newly generated aperture. One of the challenges of this approach is the inability to faithfully reproduce the desired motion-adapted aperture. This work presents an optimization-based framework with which to solve this leaf-fitting problem in real-time. Methods: This optimization framework is designed to facilitate the determination of leaf positions in real-time while accounting for the trade-off between coverage of the PTV and avoidance of organs at risk (OARs). Derived within this framework, an algorithm is presented that can account for general linear transformations of the planned MLC aperture, particularly 3D translations and in-plane rotations. This algorithm, together with algorithms presented in Sawant et al. [“Management of three-dimensional intrafraction motion through real-time DMLC tracking,” Med. Phys. 35, 2050–2061 (2008)] and Ruan and Keall [Presented at the 2011 IEEE Power Engineering and Automation Conference (PEAM) (2011) (unpublished)], was applied to apertures derived from eight lung intensity modulated radiotherapy plans subjected to six-degree-of-freedom motion traces acquired from lung cancer patients using the kilovoltage intrafraction monitoring system developed at the University of Sydney. A quality-of-fit metric was defined, and each algorithm was evaluated in terms of quality-of-fit and computation time. Results: This algorithm is shown to perform leaf-fittings of apertures, each with 80 leaf pairs, in 0.226 ms on average as compared to 0.082 and 64.2 ms for the algorithms of Sawant et al., Ruan, and Keall, respectively. The algorithm shows approximately 12% improvement in quality-of-fit over the Sawant et al

  4. Low-dose lithium stabilizes human endothelial barrier by decreasing MLC phosphorylation and universally augments cholinergic vasorelaxation capacity in a direct manner

    Directory of Open Access Journals (Sweden)

    Bert Bosche

    2016-12-01

    Full Text Available Lithium at plasma concentrations up to 1 mmol/L has been used in patients suffering from bipolar disorder for decades and has recently been shown to reduce the risk for ischemic stroke in these patients. The risk for stroke and thromboembolism depend not only on cerebral but also on general endothelial function and health; the entire endothelium as an organ is therefore pathophysiologically relevant. Regardless, the knowledge about the direct impact of lithium on endothelial function remains poor. We conducted an experimental study using lithium as pharmacologic pretreatment for murine, porcine and human vascular endothelium. We predominantly investigated endothelial vasorelaxation capacities in addition to human basal and dynamic (thrombin-/PAR-1 receptor agonist-impaired barrier functioning including myosin light chain phosphorylation (MLC-P. Low-dose therapeutic lithium concentrations (0.4 mmol/L significantly augment the cholinergic endothelium-dependent vasorelaxation capacities of cerebral and thoracic arteries, independently of central and autonomic nerve system influences. Similar concentrations of lithium (0.2-0.4 mmol/L significantly stabilized the dynamic thrombin-induced and PAR-1 receptor agonist-induced permeability of human endothelium, while even the basal permeability appeared to be stabilized. The lithium-attenuated dynamic permeability was mediated by a reduced endothelial MLC-P known to be followed by a lessening of endothelial cell contraction and paracellular gap formation. The well-known lithium-associated inhibition of inositol monophosphatase/glycogen synthase kinase-3-β signaling-pathways involving intracellular calcium concentrations in neurons seems to similarly occur in endothelial cells, too, but with different down-stream effects such as MLC-P reduction. This is the first study discovering low-dose lithium as a drug directly stabilizing human endothelium and ubiquitously augmenting cholinergic endothelium

  5. Treatment plan comparison between helical tomotherapy and MLC-based IMRT using radiobiological measures

    Energy Technology Data Exchange (ETDEWEB)

    Mavroidis, Panayiotis [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University (Sweden); Ferreira, Brigida Costa [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University (Sweden); Shi, Chengyu [Department of Radiation Oncology, University of Texas Health Science Center, San Antonio, TX (United States); Lind, Bengt K [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University (Sweden); Papanikolaou, Nikos [Department of Radiation Oncology, University of Texas Health Science Center, San Antonio, TX (United States)

    2007-07-07

    The rapid implementation of advanced treatment planning and delivery technologies for radiation therapy has brought new challenges in evaluating the most effective treatment modality. Intensity-modulated radiotherapy (IMRT) using multi-leaf collimators (MLC) and helical tomotherapy (HT) are becoming popular modes of treatment delivery and their application and effectiveness continues to be investigated. Presently, there are several treatment planning systems (TPS) that can generate and optimize IMRT plans based on user-defined objective functions for the internal target volume (ITV) and organs at risk (OAR). However, the radiobiological parameters of the different tumours and normal tissues are typically not taken into account during dose prescription and optimization of a treatment plan or during plan evaluation. The suitability of a treatment plan is typically decided based on dosimetric criteria such as dose-volume histograms (DVH), maximum, minimum, mean and standard deviation of the dose distribution. For a more comprehensive treatment plan evaluation, the biologically effective uniform dose D-bar is applied together with the complication-free tumour control probability (P{sub +}). Its utilization is demonstrated using three clinical cases that were planned with two different forms of IMRT. In this study, three different cancer types at different anatomical sites were investigated: head and neck, lung and prostate cancers. For each cancer type, a linac MLC-based step-and-shoot IMRT plan and a HT plan were developed. The MLC-based IMRT treatment plans were developed on the Philips treatment-planning platform, using the Pinnacle 7.6 software release. For the tomotherapy HiArt plans, the dedicated tomotherapy treatment planning station was used, running version 2.1.2. By using D-bar as the common prescription point of the treatment plans and plotting the tissue response probabilities versus D-bar for a range of prescription doses, a number of plan trials can be

  6. SU-E-T-506: Dosimetric Verification of Photon MLC Delivered Electron Fields for Implementing MERT On An Artiste Linac

    Energy Technology Data Exchange (ETDEWEB)

    Jin, L; Eldib, A; Li, J; Wang, L; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States); Fan, J [Virtua Fox Chase Cancer Center, Philadelphia, PA (United States)

    2014-06-01

    Purpose: To verify the dose accuracy of photon MLC delivered electron fields for implementing energy-intensity modulated electron radiotherapy (MERT) on an Artiste linac. Methods: It was proposed to deliver MERT on an Artiste linac at a short SSD (60 cm) to reduce beam penumbra caused by electron scatters. An in-house developed Monte Carlo (MC)-based dose calculation/optimization planning code was used for treatment planning. Our previous study showed that the measured dose distribution of a breast plan showed good agreement with the calculations in low-medium dose regions while the differences in high dose regions were outstanding. A continuous work found that the discrepancy is mainly caused by improper modeling in MC for the single focused MLC in the Artiste which was simplified as double focused in the previous MC simulations. With this remodeled MLC in the calculations, an energy-intensity modulated electron plan using 6, 9, 12 and 15 MeV was generated for a breast treatment on a breast phantom at a 60 cm SSD and recalculated regarding a solid water phantom. For a test study, four of MLC segments (each with a different energy) generated in the plan were delivered to the phantom and a film measurement was performed at the depth of 2 cm. The measured 2D dose distribution was then compared with calculations. Results: For composite doses of the four segments, measured 2D dose distributions overall agree well with the calculations (3mm/3%) in most area. The separate measurement for a single MLC segment for each of energies also showed the consistence with the calculations. Conclusion: After remodeling MLC in the MC calculations, the measured dose distribution for a subset of MLC segments from a MERT plan showed good agreement. Further detailed verification for the full plan will be the work in the next step.

  7. Development and evaluation of aperture-based complexity metrics using film and EPID measurements of static MLC openings

    Energy Technology Data Exchange (ETDEWEB)

    Götstedt, Julia [Department of Radiation Physics, University of Gothenburg, Göteborg 413 45 (Sweden); Karlsson Hauer, Anna; Bäck, Anna, E-mail: anna.back@vgregion.se [Department of Therapeutic Radiation Physics, Sahlgrenska University Hospital, Göteborg 413 45 (Sweden)

    2015-07-15

    Purpose: Complexity metrics have been suggested as a complement to measurement-based quality assurance for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). However, these metrics have not yet been sufficiently validated. This study develops and evaluates new aperture-based complexity metrics in the context of static multileaf collimator (MLC) openings and compares them to previously published metrics. Methods: This study develops the converted aperture metric and the edge area metric. The converted aperture metric is based on small and irregular parts within the MLC opening that are quantified as measured distances between MLC leaves. The edge area metric is based on the relative size of the region around the edges defined by the MLC. Another metric suggested in this study is the circumference/area ratio. Earlier defined aperture-based complexity metrics—the modulation complexity score, the edge metric, the ratio monitor units (MU)/Gy, the aperture area, and the aperture irregularity—are compared to the newly proposed metrics. A set of small and irregular static MLC openings are created which simulate individual IMRT/VMAT control points of various complexities. These are measured with both an amorphous silicon electronic portal imaging device and EBT3 film. The differences between calculated and measured dose distributions are evaluated using a pixel-by-pixel comparison with two global dose difference criteria of 3% and 5%. The extent of the dose differences, expressed in terms of pass rate, is used as a measure of the complexity of the MLC openings and used for the evaluation of the metrics compared in this study. The different complexity scores are calculated for each created static MLC opening. The correlation between the calculated complexity scores and the extent of the dose differences (pass rate) are analyzed in scatter plots and using Pearson’s r-values. Results: The complexity scores calculated by the edge

  8. SU-E-J-67: Evaluation of Adaptive MLC Morphing for Online Correction of Prostate Cancer Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Sandhu, R; Qin, A; Yan, D [William Beaumont Hospital, Royal Oak, MI (United States)

    2015-06-15

    Purpose: Online adaptive MLC morphing is desirable over translational couch shifts to accommodate target position as well as anatomic changes. A reliable method of adaptive MLC segment to target during prostate cancer IMRT treatment is proposed and evaluated by comparison with daily online-image guidance (IGRT) correction and online-IMRT planning. Methods: The MLC adaptive algorithm involves following steps; move the MLC segments according to target translational shifts, and then morph the segment shape to maintain the spatial relationship between the planning-target contour and MLC segment. Efficacy of this method was evaluated retrospectively using daily-CBCT images on seven prostate patients treated with seven-beam IMRT treatment to deliver 64Gy in 20 fractions. Daily modification was simulated with three approaches; daily-IGRT correction based on implanted radio-markers, adaptive MLC morphing, and online-IMRT planning, with no-residual variation. The selected dosimetric endpoints and nEUD (normalized equivalent uniform dose to online-IMRT planning) of each organ of interest were determined for evaluation and comparison. Results: For target(prostate), bladder and rectal-wall, the mean±sd of nEUD were 97.6%+3.2%, 103.9%±4.9% and 97.4%±1.1% for daily-IGRT correction; and 100.2%+0.2%, 108.9%±5.1% and 99.8%±1.2% for adaptive MLC morphing, respectively. For daily-IGRT correction, adaptive MLC morphing and online-IMRT planning, target D99 was <95% of the prescription dose in 30%, 0% and 0% of 140 fractions, respectively. For the rectal-wall, D5 exceeded 105% of the planned-D5 in 2.8%, 11.4% and 0% of 140 fractions, respectively. For the bladder, Dmax exceeded 105% of the planned-D5 in 2.8%, 5.6% and 0% of 140 fractions, respectively. D30 of bladder and rectal-wall were well within the planned-D30 for all three approaches. Conclusion: The proposed method of adaptive MLC morphing can be beneficial for the prostate patient population with large deformation and

  9. Monitoring daily MLC positional errors using trajectory log files and EPID measurements for IMRT and VMAT deliveries

    Science.gov (United States)

    Agnew, A.; Agnew, C. E.; Grattan, M. W. D.; Hounsell, A. R.; McGarry, C. K.

    2014-05-01

    This work investigated the differences between multileaf collimator (MLC) positioning accuracy determined using either log files or electronic portal imaging devices (EPID) and then assessed the possibility of reducing patient specific quality control (QC) via phantom-less methodologies. In-house software was developed, and validated, to track MLC positional accuracy with the rotational and static gantry picket fence tests using an integrated electronic portal image. This software was used to monitor MLC daily performance over a 1 year period for two Varian TrueBeam linear accelerators, with the results directly compared with MLC positions determined using leaf trajectory log files. This software was validated by introducing known shifts and collimator errors. Skewness of the MLCs was found to be 0.03 ± 0.06° (mean ±1 standard deviation (SD)) and was dependent on whether the collimator was rotated manually or automatically. Trajectory log files, analysed using in-house software, showed average MLC positioning errors with a magnitude of 0.004 ± 0.003 mm (rotational) and 0.004 ± 0.011 mm (static) across two TrueBeam units over 1 year (mean ±1 SD). These ranges, as indicated by the SD, were lower than the related average MLC positioning errors of 0.000 ± 0.025 mm (rotational) and 0.000 ± 0.039 mm (static) that were obtained using the in-house EPID based software. The range of EPID measured MLC positional errors was larger due to the inherent uncertainties of the procedure. Over the duration of the study, multiple MLC positional errors were detected using the EPID based software but these same errors were not detected using the trajectory log files. This work shows the importance of increasing linac specific QC when phantom-less methodologies, such as the use of log files, are used to reduce patient specific QC. Tolerances of 0.25 mm have been created for the MLC positional errors using the EPID-based automated picket fence test. The software allows diagnosis

  10. SU-E-T-583: Optimizing the MLC Model Parameters for IMRT in the RayStation Treatment Planning System

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S; Yi, B; Xu, H; Yang, X; Prado, K; D' Souza, W [University of Maryland School of Medicine, Baltimore, MD (United States)

    2014-06-01

    Purpose: To optimize the MLC model parameters for IMRT in the RayStation v.4.0 planning system and for a Varian C-series Linac with a 120-leaf Millennium MLC. Methods: The RayStation treatment planning system models rounded leaf-end MLC with the following parameters: average transmission, leaf-tip width, tongue-and-groove, and position offset. The position offset was provided by Varian. The leaf-tip width was iteratively evaluated by comparing computed and measured transverse dose profiles of MLC-defined fields at dmax in water. The profile comparison was also used to verify the MLC position offset. The transmission factor and leaf tongue width were derived iteratively by optimizing five clinical patient IMRT QA Results: brain, lung, pancreas, head-and-neck (HN), and prostate. The HN and prostate cases involved splitting fields. Verifications were performed with Mapcheck2 measurements and Monte Carlo calculations. Finally, the MLC model was validated using five test IMRT cases from the AAPM TG119 report. Absolute gamma analyses (3mm/3% and 2mm/2%) were applied. In addition, computed output factors for MLC-defined small fields (2×2, 3×3, 4×4, 6×6cm) of both 6MV and 18MV were compared to those measured by the Radiological Physics Center (RPC). Results: Both 6MV and 18MV models were determined to have the same MLC parameters: 2.5% transmission, tongue-and-groove 0.05cm, and leaftip 0.3cm. IMRT QA analysis for five cases in TG119 resulted in a 100% passing rate with 3mm/3% gamma analysis for 6MV, and >97.5% for 18MV. With 2mm/2% gamma analysis, the passing rate was >94.6% for 6MV and >90.9% for 18MV. The difference between computed output factors in RayStation and RPC measurements was less than 2% for all MLCdefined fields, which meets the RPC's acceptance criterion. Conclusion: The rounded leaf-end MLC model in RayStation 4.0 planning system was verified and IMRT commissioning was clinically acceptable. The IMRT commissioning was well validated using guidance

  11. Limiting dilution analysis of alloantigen-reactive cells which respond to allogeneic lymphocytes in human MLC and PLT.

    Science.gov (United States)

    Singal, D P; Naipaul, N; Joseph, S

    1980-10-01

    We have determined the frequency of the alloantigen-reactive cells (ARC) in human MLC and PLT by the limiting dilution analysis. In PLT, the frequency of the ARC to the original sensitizing donor ranged between 1:32 to 1:62, an increase of six to nine-fold after priming in MLC. The MLC primed populations were also enriched (three to five fold) for the ARC responding to the PL-positive allogeneic donors. The incidence of the ARC was 1:62 to 1:118 with donors positive for the sensitizing HLA-DRw antigen and 1:77 to 1:144 with donors negative for the specific HLA-DRw determinant. The results from experiments utilizing pooled stimulating cells from the original and allogeneic donors suggest that same subpopulation of cells responds to the sensitizing HLA-DRw determinant, whether it is presented by the specific stimulator or by a third-party allogeneic donor. On the other hand, different subpopulations of alloreactive cells respond to different alloantigens. In MLC experiments between HLA-identical siblings, the incidence of the ARC ranged between 1:995 to 1:1673. The responses of the ARC to non-HLA antigens were observed under conditions where responder cells were limiting. Also, the responses of the limiting numbers of responding cells were inhibited by mitomycin-treated autologous lymphocytes. Nonresponse in MLC combinations with higher responder cell numbers was not due to small numbers of stimulating cells.

  12. Improving IMRT-plan quality with MLC leaf position refinement post plan optimization.

    Science.gov (United States)

    Niu, Ying; Zhang, Guowei; Berman, Barry L; Parke, William C; Yi, Byongyong; Yu, Cedric X

    2012-08-01

    In intensity-modulated radiation therapy (IMRT) planning, reducing the pencil-beam size may lead to a significant improvement in dose conformity, but also increase the time needed for the dose calculation and plan optimization. The authors develop and evaluate a postoptimization refinement (POpR) method, which makes fine adjustments to the multileaf collimator (MLC) leaf positions after plan optimization, enhancing the spatial precision and improving the plan quality without a significant impact on the computational burden. The authors' POpR method is implemented using a commercial treatment planning system based on direct aperture optimization. After an IMRT plan is optimized using pencil beams with regular pencil-beam step size, a greedy search is conducted by looping through all of the involved MLC leaves to see if moving the MLC leaf in or out by half of a pencil-beam step size will improve the objective function value. The half-sized pencil beams, which are used for updating dose distribution in the greedy search, are derived from the existing full-sized pencil beams without need for further pencil-beam dose calculations. A benchmark phantom case and a head-and-neck (HN) case are studied for testing the authors' POpR method. Using a benchmark phantom and a HN case, the authors have verified that their POpR method can be an efficient technique in the IMRT planning process. Effectiveness of POpR is confirmed by noting significant improvements in objective function values. Dosimetric benefits of POpR are comparable to those of using a finer pencil-beam size from the optimization start, but with far less computation and time. The POpR is a feasible and practical method to significantly improve IMRT-plan quality without compromising the planning efficiency.

  13. Dosimetric comparison between cone/Iris-based and InCise MLC-based CyberKnife plans for single and multiple brain metastases.

    Science.gov (United States)

    Jang, Si Young; Lalonde, Ron; Ozhasoglu, Cihat; Burton, Steven; Heron, Dwight; Huq, M Saiful

    2016-09-08

    We performed an evaluation of the CyberKnife InCise MLC by comparing plan qualities for single and multiple brain lesions generated using the first version of InCise MLC, fixed cone, and Iris collimators. We also investigated differences in delivery efficiency among the three collimators. Twenty-four patients with single or multiple brain mets treated previously in our clinic on a CyberKnife M6 using cone/Iris collimators were selected for this study. Treatment plans were generated for all lesions using the InCise MLC. Number of monitor units, delivery time, target coverage, conformity index, and dose falloff were compared between MLC- and clinical cone/Iris-based plans. Statistical analysis was performed using the non-parametric Wilcoxon-Mann-Whitney signed-rank test. The planning accuracy of the MLC-based plans was validated using chamber and film measurements. The InCise MLC-based plans achieved mean dose and target coverage comparable to the cone/Iris-based plans. Although the conformity indices of the MLC-based plans were slightly higher than those of the cone/Iris-based plans, beam delivery time for the MLC-based plans was shorter by 30% ~ 40%. For smaller targets or cases with OARs located close to or abutting target volumes, MLC-based plans provided inferior dose conformity compared to cone/Iris-based plans. The QA results of MLC-based plans were within 5% absolute dose difference with over 90% gamma passing rate using 2%/2 mm gamma criteria. The first version of InCise MLC could be a useful delivery modality, especially for clinical situations for which delivery time is a limiting factor or for multitarget cases. © 2016 The Authors.

  14. Evaluation of calculation methods of collimator scatter factors in a linear accelerator equipped with MLC instead of lower collimators.

    Science.gov (United States)

    Kojima, Tomo; Sasaki, Koji

    2009-09-20

    In the monitor unit verification for high-energy radiation therapy, we evaluated methods of calculation of collimator scatter factors (S(c)) in a linear accelerator equipped with MLC instead of lower collimators. Routinely,S(c) is calculated from rectangular fields shaped by upper and lower jaws in the linear accelerator. However, this calculation method should not be used for the linear accelerator equipped with MLC instead of lower collimators. Consequently, we used a backprojected field at the flattening filter plane projected by calculation point's eye view on each MLC. We then attempted to deviseS(c) by using Clarkson's integration for these backprojected irregular fields. This method makes it possible to calculate collimator scatter factors in error of less than +/-0.3% in all of sixteen measured irregular fields.

  15. A compact and high sensitivity positron detector using dual-layer thin GSO scintillators for a small animal PET blood sampling system.

    Science.gov (United States)

    Yamamoto, Seiichi; Imaizumi, Masao; Shimosegawa, Eku; Kanai, Yasukazu; Sakamoto, Yusuke; Minato, Kotaro; Shimizu, Keiji; Senda, Michio; Hatazawa, Jun

    2010-07-07

    For quantitative measurements of small animals such as mice or rats, a compact and high sensitivity continuous blood sampling detector is required because their blood sampling volume is limited. For this purpose we have developed and tested a new positron detector. The positron detector uses a pair of dual-layer thin gadolinium orthosilicate (GSO) scintillators with different decay times. The front layer detects the positron and the background gamma photons, and the back layer detects the background gamma photons. By subtracting the count rate of the latter from that of the former, the count rate of the positrons can be estimated. The GSO for the front layer has a Ce concentration of 1.5 mol% (decay time of 35 ns), and that for the back layer has a Ce concentration of 0.5 mol% (decay time of 60 ns). By using the pulse shape analysis, the count rate of these two GSOs can be discriminated. The thickness is 0.5 mm, which is thick enough to detect positrons while minimizing the detection of the background gamma photons. These two types of thin GSOs were optically coupled to each other and connected to a metal photomultiplier tube (PMT) through triangular light guides. The signal from the PMT was digitized by 100 MHz free-running A-D converters in the data acquisition system and digitally integrated at two different integration times for the pulse shape analysis. We obtained good separation of the pulse shape distributions of these two GSOs. The energy threshold level was decreased to 80 keV, increasing the sensitivity of the detector. The sensitivity of a small diameter plastic tube was 8.6% and 24% for the F-18 and C-11 positrons, respectively. The count rate performance was linear up to approximately 50 kcps. The background counts from the gamma photons could be precisely corrected. The time-activity curve (TAC) of the rat artery blood was successfully obtained and showed a good correlation with that measured using a well counter. With these results, we confirmed

  16. Development of a Monte Carlo model for the Brainlab microMLC.

    Science.gov (United States)

    Belec, Jason; Patrocinio, Horacio; Verhaegen, Frank

    2005-03-07

    Stereotactic radiosurgery with several static conformal beams shaped by a micro multileaf collimator (microMLC) is used to treat small irregularly shaped brain lesions. Our goal is to perform Monte Carlo calculations of dose distributions for certain treatment plans as a verification tool. A dedicated microMLC component module for the BEAMnrc code was developed as part of this project and was incorporated in a model of the Varian CL2300 linear accelerator 6 MV photon beam. As an initial validation of the code, the leaf geometry was visualized by tracing particles through the component module and recording their position each time a leaf boundary was crossed. The leaf dimensions were measured and the leaf material density and interleaf air gap were chosen to match the simulated leaf leakage profiles with film measurements in a solid water phantom. A comparison between Monte Carlo calculations and measurements (diode, radiographic film) was performed for square and irregularly shaped fields incident on flat and homogeneous water phantoms. Results show that Monte Carlo calculations agree with measured dose distributions to within 2% and/or 1 mm except for field size smaller than 1.2 cm diameter where agreement is within 5% due to uncertainties in measured output factors.

  17. Analysis of the impact of uncertainties in the movement of a MLC to perform SBRT of prostate by IMAT; Analisis del impacto de las incertidumbres en el movimiento de un MLC al effectuar SBRT de prostata mediante IMAT

    Energy Technology Data Exchange (ETDEWEB)

    Reynes llomport, G.; Sancho Kolster, I.; Blas Pinol, R. de; Modolell Farre, I.; Picon Olmos, C.

    2013-07-01

    The present work shows, dosimetric level, how the technique of SBRT (Steretactic Body Radiation Therapy), studied can be administered safely, using accepted tolerances in the systematic uncertainty of MLC truck, accepted in the rest of the used techniques, although they suggest approaching the stock level tolerances for a better control of the clinical response in this type of treatment. (Author)

  18. Amorphous-crystalline dual-layer structures resulting from metastable liquid phase separation in (Fe50Co25B15Si10)8oCu20 melt-spun ribbons

    Institute of Scientific and Technical Information of China (English)

    Cao Chong-De; Gong Su-Lian; Guo Jin-Bo; Song Rui-Bo; Sun Zhan-Bo; Yang Sen; Wang Wei-Min

    2012-01-01

    (Fe50Co25B15Si10)80Cu20 ribbons are prepared by using the single-roller melt-spinning method.A dual-layer structure consisting of a (Fe,Co)-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification.The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature.It is indicated that the coercivity of the ribbon is almost zero in the as-quenched state.The crystallization leads to the increase of coercivity and decrease of saturation magnetization.

  19. SU-E-T-633: Dose Differences in Lung Cancer SBRT: The Influences of MLC Width

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J; Yin, Y [Shandong Cancer Hospital, Jinan, Shandong (China)

    2014-06-15

    Purpose: The aim is to compare the plan dose distribution of lung SBRT with MLCs in different width. Methods: Cases with phase INSCLC were enrolled. 9 cases were undergone 4D-CT scanning in the supine position with both arms raised. 3D-CT images without IV contrast were afterwards acquired with 3mm thickness and used for dose calculations. ITV was generated by using the inspiration and expiration images. The ITV can be expanded by geometric set-up uncertainty (5 mm) to generate the PTV. All chest normal tissues including chest wall were contoured by doctors. A total dose of 55 Gy will be given in 5 fractions within 10–14 days with an inter fraction interval of 2–3 days. Guided by the RTOG trial 3502 protocol, 11–13 non-coplanar fields with 6MV photon were arranged. Three types of MLCs with width of 3mm, 5mm and 10mm at isocenter position, were used separately to generate a CRT plan for each case. Monte Carlo algorithm was applied to dose calculation. All plans were adjusted as possible to meet the dose constraints. Dose-volume parameters from plans as followed were compared and analysized: PTV V55Gy, COMPTV D70% (70% of normalization dose), volume A (body minus PTV), and R100% and R50% (the ratio of x% of prescription dose isoline volume to PTV volume). Results: MLCs, 3mm and 5mm wide, played the identical roles on dosimetry of the plans, excluding the parameter volume A (p<0.05). On the contrary, MLC with width of 10mm was significantly inferior to the other two types on most parameters (p<0.05). For R50%, all types contributed equally (p>0.05). Conclusion: For lung cancer SBRT, MLC width had influence to dosimetry, especially in irradiation area. Small size MLC, e.g. 3mm and 5mm, are helpful to generate a high quality treatment plan, which could meet the strict criteria for targets and OAR.

  20. Impact of MLC leaf position errors on simple and complex IMRT plans for head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Mu, G; Ludlum, E; Xia, P [Department of Radiation Oncology, University of California, San Francisco, CA (United States)

    2008-01-07

    The dosimetric impact of random and systematic multi-leaf collimator (MLC) leaf position errors is relatively unknown for head and neck intensity-modulated radiotherapy (IMRT) patients. In this report we studied 17 head and neck IMRT patients, including 12 treated with simple plans (<50 segments) and 5 treated with complex plans (>100 segments). Random errors (-2 to +2 mm) and systematic errors ({+-}0.5 mm and {+-}1 mm) in MLC leaf positions were introduced into the clinical plans and the resultant dose distributions were analyzed based on defined endpoint doses. The dosimetric effect was insignificant for random MLC leaf position errors up to 2 mm for both simple and complex plans. However, for systematic MLC leaf position errors, we found significant dosimetric differences between the simple and complex IMRT plans. For 1 mm systematic error, the average changes in D{sub 95%} were 4% in simple plans versus 8% in complex plans. The average changes in D{sub 0.1cc} of the spinal cord and brain stem were 4% in simple plans versus 12% in complex plans. The average changes in parotid glands were 9% in simple plans versus 13% for the complex plans. Overall, simple IMRT plans are less sensitive to leaf position errors than complex IMRT plans.

  1. SU-E-T-122: Dosimetric Comparison Between Cone, HDMLC and MicroMLC for the Treatment of Trigeminal Neuralgia

    Energy Technology Data Exchange (ETDEWEB)

    Vacca, N; Caussa, L; Filipuzzi, M; Garrigo, E; Venencia, C [Instituto Privado de Radioterapia - Fundacion Marie Curie, Cordoba (Argentina)

    2014-06-01

    Purpose: The purpose of this work was to evaluate the dosimetric characteristics of three collimation systems, 5mm circular cone (Brainlab) and square fields of 5mm with HDMLC (Varian) and microMLC Moduleaf, Siemens) for trigeminal neuralgia treatment. Methods: A TPS Iplan v4.5 BrainLAB was used to do treatment plans for each collimations system in a square solid water phantom with isocenter at 5cm depth. Single field and treatment plan including 11 arcs with fix field and 100° gantry range was made for each collimation systems. EBT3 films were positioned at isocenter in a coronal plane to measured dose distribution for all geometries. Films were digitized with a Vidar DosimetryPro Red scanner with a resolution of 89dpi and RIT113v6.1 software was used for analysis. Penumbra region (80%–20%), FWHM and dose percentage at 5mm and 10mm from CAX were determined. All profiles were normalized at CAX. Results: For single beam the penumbra (FWHM) was 1.5mm (5.3mm) for the cone, 1.9mm (5.5mm) for HDMLC and 1.8mm (5.4mm) for the microMLC. Dose percentage at 5mm was 6.9% for cone, 12.5% for HDMLC and 8.7% for the microMLC. For treatment plan the penumbra (FWHM) was 2.58mm (5.47mm) for the cone, 2.8mm (5.84mm) for HDMLC and 2.58mm (6.09mm) for the microMLC. Dose perecentage at 5mm was 13.1% for cone, 16.1% for HDMLC, 15.2% for the microMLC. Conclusion: The cone has a dose falloff larger than the microMLC and HDMLC, by its reduced penumbra, this translates into better protection of surrounding healthy tissue, however, the microMLC and HDMLC have similar accuracy to cone.

  2. Beamlet based direct aperture optimization for MERT using a photon MLC

    Energy Technology Data Exchange (ETDEWEB)

    Henzen, D., E-mail: henzen@ams.unibe.ch; Manser, P.; Frei, D.; Volken, W.; Born, E. J.; Joosten, A.; Lössl, K.; Aebersold, D. M.; Chatelain, C.; Fix, M. K. [Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Berne CH-3010 (Switzerland); Neuenschwander, H. [Clinic for Radiation-Oncology, Lindenhofspital, Berne CH-3012 (Switzerland); Stampanoni, M. F. M. [Institute for Biomedical Engineering, ETH Zürich and Paul Scherrer Institut, Villigen CH-5234 (Switzerland)

    2014-12-15

    Purpose: A beamlet based direct aperture optimization (DAO) for modulated electron radiotherapy (MERT) using photon multileaf collimator (pMLC) shaped electron fields is developed and investigated. Methods: The Swiss Monte Carlo Plan (SMCP) allows the calculation of dose distributions for pMLC shaped electron beams. SMCP is interfaced with the Eclipse TPS (Varian Medical Systems, Palo Alto, CA) which can thus be included into the inverse treatment planning process for MERT. This process starts with the import of a CT-scan into Eclipse, the contouring of the target and the organs at risk (OARs), and the choice of the initial electron beam directions. For each electron beam, the number of apertures, their energy, and initial shape are defined. Furthermore, the DAO requires dose–volume constraints for the structures contoured. In order to carry out the DAO efficiently, the initial electron beams are divided into a grid of beamlets. For each of those, the dose distribution is precalculated using a modified electron beam model, resulting in a dose list for each beamlet and energy. Then the DAO is carried out, leading to a set of optimal apertures and corresponding weights. These optimal apertures are now converted into pMLC shaped segments and the dose calculation for each segment is performed. For these dose distributions, a weight optimization process is launched in order to minimize the differences between the dose distribution using the optimal apertures and the pMLC segments. Finally, a deliverable dose distribution for the MERT plan is obtained and loaded back into Eclipse for evaluation. For an idealized water phantom geometry, a MERT treatment plan is created and compared to the plan obtained using a previously developed forward planning strategy. Further, MERT treatment plans for three clinical situations (breast, chest wall, and parotid metastasis of a squamous cell skin carcinoma) are created using the developed inverse planning strategy. The MERT plans are

  3. Dosimetric evaluation of photon dose calculation under jaw and MLC shielding

    Energy Technology Data Exchange (ETDEWEB)

    Fogliata, A.; Clivio, A.; Vanetti, E.; Nicolini, G.; Belosi, M. F.; Cozzi, L. [Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona 6500 (Switzerland)

    2013-10-15

    Purpose: The accuracy of photon dose calculation algorithms in out-of-field regions is often neglected, despite its importance for organs at risk and peripheral dose evaluation. The present work has assessed this for the anisotropic analytical algorithm (AAA) and the Acuros-XB algorithms implemented in the Eclipse treatment planning system. Specifically, the regions shielded by the jaw, or the MLC, or both MLC and jaw for flattened and unflattened beams have been studied.Methods: The accuracy in out-of-field dose under different conditions was studied for two different algorithms. Measured depth doses out of the field, for different field sizes and various distances from the beam edge were compared with the corresponding AAA and Acuros-XB calculations in water. Four volumetric modulated arc therapy plans (in the RapidArc form) were optimized in a water equivalent phantom, PTW Octavius, to obtain a region always shielded by the MLC (or MLC and jaw) during the delivery. Doses to different points located in the shielded region and in a target-like structure were measured with an ion chamber, and results were compared with the AAA and Acuros-XB calculations. Photon beams of 6 and 10 MV, flattened and unflattened were used for the tests.Results: Good agreement between calculated and measured depth doses was found using both algorithms for all points measured at depth greater than 3 cm. The mean dose differences (±1SD) were −8%± 16%, −3%± 15%, −16%± 18%, and −9%± 16% for measurements vs AAA calculations and −10%± 14%, −5%± 12%, −19%± 17%, and −13%± 14% for Acuros-XB, for 6X, 6 flattening-filter free (FFF), 10X, and 10FFF beams, respectively. The same figures for dose differences relative to the open beam central axis dose were: −0.1%± 0.3%, 0.0%± 0.4%, −0.3%± 0.3%, and −0.1%± 0.3% for AAA and −0.2%± 0.4%, −0.1%± 0.4%, −0.5%± 0.5%, and −0.3%± 0.4% for Acuros-XB. Buildup dose was overestimated with AAA, while Acuros-XB gave

  4. Dosimetric evaluation of photon dose calculation under jaw and MLC shielding.

    Science.gov (United States)

    Fogliata, A; Clivio, A; Vanetti, E; Nicolini, G; Belosi, M F; Cozzi, L

    2013-10-01

    The accuracy of photon dose calculation algorithms in out-of-field regions is often neglected, despite its importance for organs at risk and peripheral dose evaluation. The present work has assessed this for the anisotropic analytical algorithm (AAA) and the Acuros-XB algorithms implemented in the Eclipse treatment planning system. Specifically, the regions shielded by the jaw, or the MLC, or both MLC and jaw for flattened and unflattened beams have been studied. The accuracy in out-of-field dose under different conditions was studied for two different algorithms. Measured depth doses out of the field, for different field sizes and various distances from the beam edge were compared with the corresponding AAA and Acuros-XB calculations in water. Four volumetric modulated arc therapy plans (in the RapidArc form) were optimized in a water equivalent phantom, PTW Octavius, to obtain a region always shielded by the MLC (or MLC and jaw) during the delivery. Doses to different points located in the shielded region and in a target-like structure were measured with an ion chamber, and results were compared with the AAA and Acuros-XB calculations. Photon beams of 6 and 10 MV, flattened and unflattened were used for the tests. Good agreement between calculated and measured depth doses was found using both algorithms for all points measured at depth greater than 3 cm. The mean dose differences (± 1SD) were -8% ± 16%, -3% ± 15%, -16% ± 18%, and -9% ± 16% for measurements vs AAA calculations and -10% ± 14%, -5% ± 12%, -19% ± 17%, and -13% ± 14% for Acuros-XB, for 6X, 6 flattening-filter free (FFF), 10X, and 10FFF beams, respectively. The same figures for dose differences relative to the open beam central axis dose were: -0.1% ± 0.3%, 0.0% ± 0.4%, -0.3% ± 0.3%, and -0.1% ± 0.3% for AAA and -0.2% ± 0.4%, -0.1% ± 0.4%, -0.5% ± 0.5%, and -0.3% ± 0.4% for Acuros-XB. Buildup dose was overestimated with AAA, while Acuros-XB gave results more consistent with

  5. MLC2450无烟煤立磨的开发设计

    Institute of Scientific and Technical Information of China (English)

    谢伟安

    2014-01-01

    MLC2450无烟煤立磨是北方重工集团有限公司水泥设备分公司在MPF煤立磨、MLK矿渣立磨成功经验的基础上,从无烟煤的特性入手,自行开发设计的高细煤粉粉磨设备。文章简要介绍了该立磨的结构组成和工作原理,详细分析了该磨的技术特点和性能优势。粉磨无烟煤具有能耗低、磨损小、运行平稳等特点。

  6. Commissioning, evaluation, quality assurance and clinical application of a virtual micro MLC technique.

    Science.gov (United States)

    Woo, M; Charland, P; Kim, B; Nico, A

    2003-02-01

    Multileaf collimators (MLCs) are a valuable tool in modern radiation therapy, offering flexible and convenient field shaping. One disadvantage, however, is the undulation of the dose distribution at the edge shaped by the leaves due to the finite leaf width. An attempt to reduce the effect of this undulation is the objective of the commercial linear accelerator package HD270, which incorporates three-dimensional couch translation together with leaf adjustment to emulate finer leaf widths. In this paper we report on the commissioning and evaluation of this feature, together with the development of a process for quality assurance, as well as description of a clinical application of this technique. It is concluded that this technique could be applied reliably to situations currently utilizing MLC for shielding, with little added cost in treatment time, provided that a comprehensive quality assurance program is in place to monitor the performance of this complicated procedure.

  7. The efflux pump MlcE from the Penicillium solitum compactin biosynthetic gene cluster increases Saccharomyces cerevisiae resistance to natural statins

    DEFF Research Database (Denmark)

    Ley, Ana; Frandsen, Rasmus John Normand

    in yeast, which would overcome the undesirable effects of statins. One possible mechanism is an active export of statins, a mechanism that does not just provide the resistance but can also significantly ease the purification of the produced compounds. In order to establish export of statins from yeast we...... integrated a putative efflux pump-encoding gene mlcE from the P. solitum compactin biosynthetic gene cluster into S. cerevisiae genome. The resulting strain was tested for susceptibility to statins by growing the strain on media containing statins. The constructed strain showed an increased resistance...... to both natural statins (compactin and lovastatin), and also to a semi-synthetic statin simvastatin, when compared to the wild type strain. Expression of a mRFP-tagged MlcE show that MlcE is localized in the yeast plasma membrane. In conclusion we provide evidence indicating that MlcE is a transmembrane...

  8. SU-C-BRB-04: Characteristics and Performance Evaluation of the First Commercial MLC for a Robotic Delivery System

    Energy Technology Data Exchange (ETDEWEB)

    Fuerweger, C [Erasmus MC Cancer Institute, Rotterdam (Netherlands); European Cyberknife Center Munich, Munich, DE (Germany); Prins, P; Coskan, H; Heijmen, B [Erasmus MC Cancer Institute, Rotterdam (Netherlands)

    2015-06-15

    Purpose: To assess characteristics and performance of the “Incise™” MLC (41 leaf pairs, 2.5mm width, FFF linac) mounted on the robotic SRS/SBRT platform “CyberKnife M6™” in a pre-clinical 5 months (11/2014–03/2015) test period. Methods: Beam properties were measured with unshielded diodes and EBT3 film. The CyberKnife workspace for MLC was analyzed by transforming robot node coordinates (cranial / body paths) into Euler geometry. Bayouth tests for leaf / bank position accuracy were performed in standard (A/P) and clinically relevant non-standard positions, before and after exercising the MLC for 10+ minutes. Total system and delivery accuracy were assessed in End-to-End tests and dosimetric verification of exemplary plans. Stability over time was evaluated in Picket-Fence-and adapted Winston-Lutz-tests (AQA) for different collimator angles. Results: Penumbrae (80–20%, with 100%=2*dose at inflection point; SAD 80cm; 10cm depth) parallel / perpendicular to leaf motion were 2.87/2.64mm for the smallest (0×76×0.75cm{sup 2}) and 5.34/4.94mm for the largest (9.76×9.75cm{sup 2}) square field. MLC circular field penumbrae exceeded fixed cones by 10–20% (e.g. 60mm: 4.0 vs. 3.6mm; 20mm: 3.6 vs. 2.9mm). Interleaf leakage was <0.5%. Clinically accessible workspace with MLC covered (non-coplanar) gantry angles of [-113°;+112°] (cranial) and [-108°;+102°] (body), and collimator angles of [-100°;+107°] (cranial) and [-91°;+100°] (body). Average leaf position offsets were ≤0.2mm in 14 standard A/P Bayouth tests and ≤0.6mm in 8 non-standard direction tests. Pre-test MLC exercise increased jaggedness (range ±0.3mm vs. ±0.5mm) and allowed to identify one malfunctioning leaf motor. Total system accuracy with MLC was 0.39±0.06mm in 6 End-to-End tests. Picket-Fence and AQA showed no adverse trends during the test period. Conclusion: The Incise™ MLC for CyberKnife M6™ displayed high accuracy and mechanical stability over the test period. The

  9. Immunosuppressant MPA Modulates Tight Junction through Epigenetic Activation of MLCK/MLC-2 Pathway via p38MAPK

    Directory of Open Access Journals (Sweden)

    Niamat Khan

    2015-12-01

    Full Text Available Background: Mycophenolic acid (MPA is an important immunosuppressive drug (ISD prescribed to prevent graft rejection in the organ transplanted patients, however, its use is also associated with adverse side effects like sporadic gastrointestinal (GI disturbances. Recently, we reported the MPA induced tight junctions (TJs deregulation which involves MLCK/MLC-2 pathway. Here, we investigated the global histone acetylation as well as gene-specific chromatin signature of several genes associated with TJs regulation in Caco-2 cells after MPA treatment.Results: The epigenetic analysis shows that MPA treatment increases the global histone acetylation levels as well as the enrichment for transcriptional active histone modification mark (H3K4me3 at promoter regions of p38MAPK, ATF-2, MLCK, and MLC-2. In contrast, the promoter region of occludin was enriched for transcriptional repressive histone modification mark (H3K27me3 after MPA treatment. In line with the chromatin status, MPA treatment increased the expression of p38MAPK, ATF-2, MLCK, and MLC-2 both at transcriptional and translational level, while occludin expression was negatively influenced. Interestingly, the MPA induced gene expression changes and functional properties of Caco-2 cells could be blocked by the inhibition of p38MAPK using a chemical inhibitor (SB203580.Conclusions: Collectively, our results highlight that MPA disrupts the structure of TJs via p38MAPK-dependent activation of MLCK/MLC-2 pathway that results in decreased integrity of Caco-2 monolayer. These results led us to suggest that p38MAPK-mediated lose integrity of epithelial monolayer could be the possible cause of GI disturbance (barrier dysfunction in the intestine, leading to leaky style diarrhea observed in the organ-transplanted patients treated with MPA.

  10. Safety and Efficacy of MLC601 in Iranian Patients after Stroke: A Double-Blind, Placebo-Controlled Clinical Trial

    Directory of Open Access Journals (Sweden)

    A. A. Harandi

    2011-01-01

    Full Text Available Objective. To investigate the safety and efficacy of MLC601 (NeuroAid as a traditional Chinese medicine on motor recovery after ischemic stroke. Methods. This study was a double-blind, placebo-controlled clinical trial on 150 patients with a recent (less than 1 month ischemic stroke. All patients were given either MLC601 (100 patients or placebo (50 patients, 4 capsules 3 times a day, as an add-on to standard stroke treatment for 3 months. Results. Sex, age, elapsed time from stroke onset, and risk factors in the treatment group were not significantly different from placebo group at baseline (P>.05. Repeated measures analysis showed that Fugl-Meyer assessment was significantly higher in the treatment group during 12 weeks after stroke (P<.001. Good tolerability to treatment was shown, and adverse events were mild and transient. Conclusion. MLC601 showed better motor recovery than placebo and was safe on top of standard ischemic stroke medications especially in the severe and moderate cases.

  11. Ameliorative effect of melatonin against increased intestinal permeability in diabetic rats: possible involvement of MLCK-dependent MLC phosphorylation.

    Science.gov (United States)

    Yang, Xiaoping; Zou, Duobing; Tang, Songtao; Fan, Tingting; Su, Huan; Hu, Ruolei; Zhou, Qing; Gui, Shuyu; Zuo, Li; Wang, Yuan

    2016-05-01

    The increased intestinal permeability and functional impairment play an important role in type 2 diabetes (T2D), and melatonin may possess enteroprotection properties. Therefore, we used streptozotocin-induced diabetic rat model to investigate the regulation of intestinal permeability by melatonin. Rats were randomly divided into three groups, including control, diabetes mellitus (DM), and DM rats treated with melatonin. Melatonin was administered (10 mg/kg/day) by gavage for 24 weeks. The DM rats significantly increased the serum fasting blood glucose and lipid levels, which were alleviated by melatonin treatment. Importantly, the intestinal epithelial permeability was significantly increased in DM rats but was ameliorated following treatment with melatonin. These findings also indicated the expression of myosin light chain kinase (MLCK) and phosphorylation of MLC targeting subunit (MYPT) induced myosin light chain (MLC) phosphorylation level was markedly elevated in hyperglycemic and hyperlipidemic status. They were partly associated with down-regulated membrane type 1 and 2 (MT1 and MT2) expression, and up-regulated Rho-associated protein kinase (ROCK) expression and increased extracellular signal-regulated kinase (ERK) phosphorylation. However, the changes in target protein expression were reversed by melatonin. In conclusion, our results show melatonin beneficial effects on impaired intestinal epithelial permeability in T2D by suppressing ERK/MLCK- and ROCK/MCLP-dependent MLC phosphorylation.

  12. Heterologous expression of MlcE in Saccharomyces cerevisiae provides resistance to natural and semi-synthetic statins

    Directory of Open Access Journals (Sweden)

    Ana Ley

    2015-12-01

    Full Text Available Statins are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the key enzyme in cholesterol biosynthesis. Their extensive use in treatment and prevention of cardiovascular diseases placed statins among the best selling drugs. Construction of Saccharomyces cerevisiae cell factory for the production of high concentrations of natural statins will require establishment of a non-destructive self-resistance mechanism to overcome the undesirable growth inhibition effects of statins. To establish active export of statins from yeast, and thereby detoxification, we integrated a putative efflux pump-encoding gene mlcE from the mevastatin-producing Penicillium citrinum into the S. cerevisiae genome. The resulting strain showed increased resistance to both natural statins (mevastatin and lovastatin and semi-synthetic statin (simvastatin when compared to the wild type strain. Expression of RFP-tagged mlcE showed that MlcE is localized to the yeast plasma and vacuolar membranes. We provide a possible engineering strategy for improvement of future yeast based production of natural and semi-synthetic statins.

  13. Monte Carlo simulation of MLC-shaped TrueBeam electron fields benchmarked against measurement

    CERN Document Server

    Lloyd, Samantha AM; Zavgorodni, Sergei

    2014-01-01

    Modulated electron radiotherapy (MERT) and combined, modulated photon/electron radiotherapy (MPERT) have received increased research attention, having shown capacity for reduced low dose exposure to healthy tissue and comparable, if not improved, target coverage for a number of treatment sites. Accurate dose calculation tools are necessary for clinical treatment planning, and Monte Carlo (MC) is the gold standard for electron field simulation. With many clinics replacing older accelerators, MC source models of the new machines are needed for continued development, however, Varian has kept internal schematics of the TrueBeam confidential and electron phase-space sources have not been made available. TrueBeam electron fields are not substantially different from those generated by the Clinac 21EX, so we have modified the internal schematics of the Clinac 21EX to simulate TrueBeam electrons. BEAMnrc/DOSXYZnrc were used to simulate 5x5 and 20x20 cm$^2$ electron fields with MLC-shaped apertures. Secondary collimati...

  14. Schemes of Repeater Optimizing Distribution based on the MLC Application and CBLRD Simulation

    Directory of Open Access Journals (Sweden)

    Qian Qiuye

    2013-07-01

    Full Text Available The widely use of repeaters raises concern about their coordination among the public. Since repeaters may suffer interaction and limitation bearing capacity, designing a reasonable repeaters coordination method is of great significance. This study address the problem if repeater coordination in a circular flat area with minimal number of repeaters with seamless coverage theory, system simulation method. With 1,000 users, this study model the coverage, getting the minimal number of repeaters of different coverage radius based on extensive used regular hexagon coverage theory. A numerical example was given in this case. When the number of users increases to 10,000, this study simulate to get the signal density across the area according to the consideration of repeaters and the different distribution of users, which are divided into uniform distribution, linear distribution, normal distribution and lognormal distribution. Then, Multi-Layer Coverage (MLC and Coverage by Link Rate Density (CBLRD are created as the distribution scheme on the area where repeat service demand is large. Moreover, for solution on the distribution of the repeaters with barriers, distribution schemes are given considering the transmission of VHF spectrums and the distribution of users around the barrier. Additionally, Spring Comfortable Degree (SCD is used for evaluation of the results and the developing tends are given to improve the model. Due to the reasonable assumption, the solution of repeater distribution is of pivotal reference value based on the reasonable results.

  15. Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators

    Directory of Open Access Journals (Sweden)

    Mostafa R. A. Nabawy

    2016-01-01

    Full Text Available Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF for cantilever based piezoelectric actuators and provides for the first time explicit expressions for calculation of dynamic EMCF based on arrangement of passive and active layers, layer geometry, and active and passive materials selection. Three main cantilever layer configurations are considered: unimorph, dual layer bimorph and triple layer bimorph. The actuator is modeled using standard constitutive dynamic equations that relate deflection and charge to force and voltage. A mode shape formulation is used for the cantilever dynamics that allows the generalized mass to be the actual mass at the first resonant frequency, removing the need for numerical integration in the design process. Results are presented in the form of physical insight from the model structure and also numerical evaluations of the model to provide trends in dynamic EMCF with actuator design parameters. For given material properties of the active and passive layers and given system overall damping ratio, the triple layer bimorph topology is the best in terms of theoretically achievable dynamic EMCF, followed by the dual layer bimorph. For a damping ratio of 0.035, the dynamic EMCF for an example dual layer bimorph configuration is 9% better than for a unimorph configuration. For configurations with a passive layer, the ratio of thicknesses for the passive and active layers is the primary geometric design variable. Choice of passive layer stiffness (Young’s modulus relative to the stiffness of the material in the active layer is an important materials related design choice. For unimorph configurations, it is beneficial to use the highest stiffness possible passive material, whereas for triple layer bimorph configurations, the passive

  16. Comparison of conventional inserts and an add-on electron MLC for chest wall irradiation of left-sided breast cancer

    Energy Technology Data Exchange (ETDEWEB)

    Vatanen, Tero; Lahtinen, Tapani (Dept. of Oncology, Kuopio Univ. Hospital, Kuopio (Finland)); Traneus, Erik (Nucletron Scandinavia AB, Uppsala (Sweden))

    2009-04-15

    Background. Collimation of irregularly shaped clinical electron beams is currently based on electron inserts made of low melting point alloys. The present investigation compares a conventional electron applicator with insert and add-on eMLC-based dose distributions in the postoperative chest wall irradiation of left-sided breast cancer. Material and methods. Voxel Monte Carlo++ (VMC++) calculated dose distributions related to electron fields were compared with 10 left-sided breast cancer patients after radical mastectomy. The prescription dose was 50 Gy at a build-up maximum. The same dose was prescribed for the ipsilateral axillary, parasternal and supraclavicular lymph nodes that were treated with photons and calculated with a pencil beam algorithm. The insert beams were shaped with 1.5 cm thick Wood's metal electron inserts in an electron applicator of a Varian 2100 C/D linac. Doses for the eMLC-shaped beams were calculated for an eMLC prototype with 2 cm thick and 5 mm wide steel leaves. The same collimator-to-surface distance (CSD) of 5.8 cm was used for both collimators. Results. The mean PTV dose was slightly higher for the eMLC plans (50.7 vs 49.5 Gy, p<0.001, respectively). The maximum doses assessed by D5% for the eMLC and insert were 60.9 and 59.1 Gy (p<0.001). The difference was due to the slightly higher doses near the field edges for the eMLC. The left lung V20 volumes were 34.5% and 34.0% (p<0.001). There was only a marginal difference in heart doses. Discussion: Despite a slight increase of maximum dose in PTV the add-on electron MLC for chest wall irradiation results in practically no differences in dose distributions compared with the present insert-based collimation.

  17. Serial tomotherapy vs. MLC-IMRT (Multileaf Collimator Intensity Modulated Radiotherapy) for simultaneous boost treatment large intracerebral lesions; Serielle Tomotherapie vs. MLC-IMRT (Multileaf Collimator Intensity Modulated Radiotherapy) fuer die simultane Boostbestrahlung mehrerer groesserer Hirnfiliae

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, Dirk; Lohr, Frank; Mai, Sabine; Polednik, Martin; Wenz, Frederik [Universitaetsklinikum Mannheim, Mannheim (Germany). Klinik fuer Strahlentherapie und Radioonkologie; Abo-Madyan, Yasser [Universitaetsklinikum Mannheim, Mannheim (Germany). Klinik fuer Strahlentherapie und Radioonkologie; Kasr-El-Einy Hospital. Cairo Univ. (EG). Dept. of Oncology (NEMROCK); Dobler, Barbara [Klinikum der Universitaet Regensburg (Germany). Strahlentherapie

    2009-07-01

    Introduction: Recent data suggest that a radiosurgery boost treatment for up to three brain metastases in addition to whole brain radiotherapy (WBRT) is beneficial. Sequential treatment of multiple metastatic lesions is time-consuming and optimal normal tissue sparing is not trivial for larger metastases when separate plans are created and are only superimposed afterwards. Sequential Tomotherapy with noncoplanar arcs and Multi-field IMRT may streamline the process and enable easy simultaneous treatment. We compared plans for 2-3 intracerebral targets calculated with Intensity Modulated Radiotherapy (IMRT) based on treatment with MLC or sequential Tomotherapy using the Peacock-System. Treatment time was not to exceed 90 min on a linac with standart dose rate. MIMiC plans without treatment-time restrictions were created as a benchmark. Materials and methods: Calculations are based on a Siemens KD2 linac with a dose rate of 200 MU/min. Step-and-Shoot IMRT is performed with a standard MLC (2 x 29 leaves, 1 cm), serial Tomotherapy with the Multivane-Collimator MIMiC (NOMOS Inc. USA). Treatment plans are created with Corvus 5.0. To create plans with good conformity we chose a noncoplanar beam- and arc geometry for each approach (IMRT 4-, MIMiC 5-couch angles). The benchmark MIMiC plans with maximally steep dose gradients had 9 couch angles. For plan comparison reasons, 10Gy were prescribed to 90% of the PTV. Steepness of dose gradients, homogeneity and conformity were assessed by the following parameters: Volume encompassed by certain isodoses outside the target as well as homogeneity and conformity as indicated by Homogeneity- and Conformity-Index. Results: Plans without treatment-time restrictions had slightest dose to organ at risk (OAR), normal tissue and least Conformity-index. MIMiC- and MLC-IMRT based plans can be treated within the intended period of 90 min, all plans met the required dose. MLC based plans resulted in higher dose to organs at risk (OAR) and dose

  18. SU-E-T-175: Evaluation of the Relative Output Ratio for Collimator Jaw and MLC Defined Small Static 6MV Photon Fields

    Energy Technology Data Exchange (ETDEWEB)

    Cho, G [Chris O' Brien Lifehouse at RPAH, Camperdown, NSW 2050 (Australia); Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW (Australia); Thwaites, D [Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW (Australia)

    2014-06-01

    Purpose: To evaluate relative output ratio of collimator jaw and MLC defined small photon fields. Methods: Relative output ratios were measured using Gafchromic EBT3 film for a 6 MV photon beam on a Novalis Tx with HD120 MLC. Beam collimation was achieved by the jaws for 1.0 cm and 3.0 cm and MLC defined square field sizes between 0.5 cm and 1.0 cm with varying jaw settings between 2.0 and 4.0 cm. Film pieces were exposed to 4 Gy. Experiments were repeated with each session consisting of five consecutive exposures for the given MLC and/or jaw collimation and with the MLC and the jaws reset for each exposure. Films were scanned using EPSON 10000XL flatbed scanner approximately 24 hours after exposure in 48 bit RGB format at 150 dpi. Film calibration data were corrected for daily linac output variations. Doses were evaluated using the green channel with square ROI sizes of 0.1 – 0.6 cm. Converted doses were normalised for output ratio calculation using the 3.0 cm field as a machine specific reference field size. Mean output ratio and coefficient of variation (CV) were calculated for each experimental session. Results: For the Novalis 6 MV photon beam the output ratios between 0.719 and 0.872 have been measured for the jaw/MLC combinations tested. For a jaw setting of 4.0 cm field, the mean CV of the output ratios increased from 0.77% to 1.48% with decreasing MLC field size from 1.0 cm to 0.5 cm. For a nominal MLC 1.0 cm field, the CV increased to 1.00% from 0.77% with reducing jaw field size from 4.0 cm to 2.0 cm. Conclusion: The relative output ratio and the associated CV were dependent on the collimator jaw and MLC settings. The field size dependent CV showed similar trends to those reported in the literature.

  19. Evaluation of the dose calculation accuracy for small fields defined by jaw or MLC for AAA and Acuros XB algorithms.

    Science.gov (United States)

    Fogliata, Antonella; Lobefalo, Francesca; Reggiori, Giacomo; Stravato, Antonella; Tomatis, Stefano; Scorsetti, Marta; Cozzi, Luca

    2016-10-01

    Small field measurements are challenging, due to the physical characteristics coming from the lack of charged particle equilibrium, the partial occlusion of the finite radiation source, and to the detector response. These characteristics can be modeled in the dose calculations in the treatment planning systems. Aim of the present work is to evaluate the MU calculation accuracy for small fields, defined by jaw or MLC, for anisotropic analytical algorithm (AAA) and Acuros XB algorithms, relative to output measurements on the beam central axis. Single point output factor measurement was acquired with a PTW microDiamond detector for 6 MV, 6 and 10 MV unflattened beams generated by a Varian TrueBeam STx equipped with high definition-MLC. Fields defined by jaw or MLC apertures were set; jaw-defined: 0.6 × 0.6, 0.8 × 0.8, 1 × 1, 2 × 2, 3 × 3, 4 × 4, 5 × 5, and 10 × 10 cm(2); MLC-defined: 0.5 × 0.5 cm(2) to the maximum field defined by the jaw, with 0.5 cm stepping, and jaws set to: 2 × 2, 3 × 3, 4 × 4, 5 × 5, and 10 × 10 cm(2). MU calculation was obtained with 1 mm grid in a virtual water phantom for the same fields, for AAA and Acuros algorithms implemented in the Varian eclipse treatment planning system (version 13.6). Configuration parameters as the effective spot size (ESS) and the dosimetric leaf gap (DLG) were varied to find the best parameter setting. Differences between calculated and measured doses were analyzed. Agreement better than 0.5% was found for field sizes equal to or larger than 2 × 2 cm(2) for both algorithms. A dose overestimation was present for smaller jaw-defined fields, with the best agreement, averaged over all the energies, of 1.6% and 4.6% for a 1 × 1 cm(2) field calculated by AAA and Acuros, respectively, for a configuration with ESS = 1 mm for both X and Y directions for AAA, and ESS = 1.5 and 0 mm for X and Y directions for Acuros. Conversely, a calculated dose underestimation was found for small MLC-defined fields, with the

  20. New chicken Rfp-Y haplotypes on the basis of MHC class II RFLP and MLC analyses

    DEFF Research Database (Denmark)

    Juul-Madsen, H R; Zoorob, R; Auffray, C;

    1997-01-01

    New chicken Rfp-Y haplotypes were determined by the use of restriction fragment length polymorphism (RFLP) and mixed lymphocyte culture (MLC) in four different chicken haplotypes, B15, B19, B21, B201. The RFLP polymorphism was mapped to the Rfp-Y system by the use of a subclone (18.1) which maps...... near a polymorphic lectin gene located in the Rfp-Y system and DNA from families with known segregation of the implicated RFLP polymorphism. For the first time it is shown that major histocompatibility complex class II genes in the Rfp-Y system have functional implications. Sequence information...

  1. Asymmetric Programming: A Highly Reliable Metadata Allocation Strategy for MLC NAND Flash Memory-Based Sensor Systems

    Science.gov (United States)

    Huang, Min; Liu, Zhaoqing; Qiao, Liyan

    2014-01-01

    While the NAND flash memory is widely used as the storage medium in modern sensor systems, the aggressive shrinking of process geometry and an increase in the number of bits stored in each memory cell will inevitably degrade the reliability of NAND flash memory. In particular, it's critical to enhance metadata reliability, which occupies only a small portion of the storage space, but maintains the critical information of the file system and the address translations of the storage system. Metadata damage will cause the system to crash or a large amount of data to be lost. This paper presents Asymmetric Programming, a highly reliable metadata allocation strategy for MLC NAND flash memory storage systems. Our technique exploits for the first time the property of the multi-page architecture of MLC NAND flash memory to improve the reliability of metadata. The basic idea is to keep metadata in most significant bit (MSB) pages which are more reliable than least significant bit (LSB) pages. Thus, we can achieve relatively low bit error rates for metadata. Based on this idea, we propose two strategies to optimize address mapping and garbage collection. We have implemented Asymmetric Programming on a real hardware platform. The experimental results show that Asymmetric Programming can achieve a reduction in the number of page errors of up to 99.05% with the baseline error correction scheme. PMID:25310473

  2. The effect of extremely narrow MLC leaf width on the plan quality of VMAT for prostate cancer.

    Science.gov (United States)

    Park, Jong Min; Park, So-Yeon; Kim, Jin Ho; Carlson, Joel; Kim, Jung-In

    2016-06-23

    To investigate the effect of multi-leaf collimators (MLCs) with leaf width of 1.25 mm on the plan quality of volumetric modulated arc therapy (VMAT) for prostate cancer. A total of 20 patients with prostate cancer were retrospectively selected. Using a high definition MLC (HD MLC), primary and boost VMAT plans with two full arcs were generated for each patient (original plan). After that, by shifting the isocenter position of the 2nd arc by 1.25 mm in the cranio-caudal direction, we simulated fluences made with MLCs with leaf width of 1.25 mm. After shifting, primary and boost plans were generated for each patient (shifted plan). A sum plan was generated by summation of the primary and boost plan for each patient. Dose-volumetric parameters were calculated and compared. Both the homogeneity index (HI) and conformity index (CI) of the shifted plans were better than those of the original plans in primary plans (HI = 0.065 vs. 0.059 with p plans for the boost target volume showed better homogeneity and conformity than did the original plans (HI = 0.060 vs. 0.053 with p plans was closer to the prescription dose than that of the shifted plans in the case of sum plans (81.45 Gy vs. 81.12 Gy with p = 0.001). Use of extremely narrow MLCs could increase dose homogeneity and conformity of the target volume for prostate VMAT.

  3. Honokiol inhibits migration of renal cell carcinoma through activation of RhoA/ROCK/MLC signaling pathway.

    Science.gov (United States)

    Cheng, Shujie; Castillo, Victor; Welty, Matt; Eliaz, Isaac; Sliva, Daniel

    2016-10-01

    Honokiol, a biologically active compound isolated from Magnolia bark, has been shown to possess promising anticancer effect through induction of apoptosis. However, there is a relative lack of information regarding its anti‑metastatic activity. Renal cell carcinoma (RCC) is the most common malignancy of the adult kidney and is known for high risk of metastasis. Clinically, therapeutic methods for metastatic RCC cases are limited and efforts to exploit new treatments are still ongoing. The results of our current investigation first revealed that honokiol suppressed the proliferation of different human RCCs without affecting cell viability. In addition, honokiol inhibited migration of highly metastatic RCC 786‑0 cells and stimulated the activity of small GTPase, RhoA. Furthermore, phosphorylated myosin light chain (MLC) and excessive formation of actin stress fibers were identified in 786‑0 cells treated with honokiol. Interestingly, the pharmacological Rho‑associated protein kinase (ROCK) inhibitor Y‑27632 attenuated contraction of actin stress fibers induced by honokiol and abrogated honokiol‑mediated inhibition of cell migration. Together these important findings suggest that honokiol suppresses the migration of highly metastatic RCC through activation of RhoA/ROCK/MLC signaling and warrants attention in the treatment of RCC metastasis as a novel therapeutic approach.

  4. Dose-to-water conversion for the backscatter-shielded EPID: A frame-based method to correct for EPID energy response to MLC transmitted radiation

    Energy Technology Data Exchange (ETDEWEB)

    Zwan, Benjamin J., E-mail: benjamin.zwan@uon.edu.au; O’Connor, Daryl J. [School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales 2308 (Australia); King, Brian W. [Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University Health System, Richmond, Virginia 23298 (United States); Greer, Peter B. [School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales 2308, Australia and Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Newcastle, New South Wales 2310 (Australia)

    2014-08-15

    Purpose: To develop a frame-by-frame correction for the energy response of amorphous silicon electronic portal imaging devices (a-Si EPIDs) to radiation that has transmitted through the multileaf collimator (MLC) and to integrate this correction into the backscatter shielded EPID (BSS-EPID) dose-to-water conversion model. Methods: Individual EPID frames were acquired using a Varian frame grabber and iTools acquisition software then processed using in-house software developed inMATLAB. For each EPID image frame, the region below the MLC leaves was identified and all pixels in this region were multiplied by a factor of 1.3 to correct for the under-response of the imager to MLC transmitted radiation. The corrected frames were then summed to form a corrected integrated EPID image. This correction was implemented as an initial step in the BSS-EPID dose-to-water conversion model which was then used to compute dose planes in a water phantom for 35 IMRT fields. The calculated dose planes, with and without the proposed MLC transmission correction, were compared to measurements in solid water using a two-dimensional diode array. Results: It was observed that the integration of the MLC transmission correction into the BSS-EPID dose model improved agreement between modeled and measured dose planes. In particular, the MLC correction produced higher pass rates for almost all Head and Neck fields tested, yielding an average pass rate of 99.8% for 2%/2 mm criteria. A two-sample independentt-test and fisher F-test were used to show that the MLC transmission correction resulted in a statistically significant reduction in the mean and the standard deviation of the gamma values, respectively, to give a more accurate and consistent dose-to-water conversion. Conclusions: The frame-by-frame MLC transmission response correction was shown to improve the accuracy and reduce the variability of the BSS-EPID dose-to-water conversion model. The correction may be applied as a preprocessing step

  5. Efficacy and Safety of MLC601 in the Treatment of Mild Cognitive Impairment: A Pilot, Randomized, Double-Blind, Placebo-Controlled Study

    Directory of Open Access Journals (Sweden)

    Hossein Pakdaman

    2017-05-01

    Full Text Available Background and Aim: Mild cognitive impairment (MCI is characterized by declined cognitive function greater than that expected for a person’s age. The clinical significance of this condition is its possible progression to dementia. MLC601 is a natural neuroprotective medication that has shown promising effects in Alzheimer disease. Accordingly, we conducted this randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of MLC601 in MCI patients. Methods: Seventy-two patients with a diagnosis of MCI were recruited. The included participants were randomly assigned to groups to receive either MLC601 or placebo. An evaluation of global cognitive function was performed at baseline as well as at 3-month and 6-month follow-up visits. Global cognitive function was assessed by Mini-Mental State Examination (MMSE and Alzheimer’s Disease Assessment Scale-cognitive subscale (ADAS-cog scores. Efficacy was evaluated by comparing global function scores between the 2 groups during the study period. Safety assessment included adverse events (AEs and abnormal laboratory results. Results: Seventy patients completed the study, 34 in the MLC601 group and 36 in the placebo group. The mean changes (±SD in cognition scores over 6 months in the MLC601 group were –2.26 (±3.42 for the MMSE and 3.82 (±6.16 for the ADAS-cog; in the placebo group, they were –2.66 (±3.43 for the MMSE and 4.41 (±6.66 for the ADAS-cog. The cognition changes based on both MMSE and ADAS-cog scores were statistically significant between the placebo and the MLC601 group (p < 0.001. Only 5 patients (14.7% reported minor AEs in the MLC601 group, the most commonly reported of which were gastrointestinal, none of them leading to patient withdrawal. Conclusion: MLC601 has shown promising efficacy and acceptable AEs in MCI patients.

  6. SU-E-T-128: Dosimetric Evaluation of MLC Modeling in Pinnacle V9.2 for Varian TrueBeam STx

    Energy Technology Data Exchange (ETDEWEB)

    Otageri, P; Grant, E; Maricle, S; Mathews, B [CARTI, Inc., Little Rock, AR (United States)

    2014-06-01

    Purpose: To evaluate the effects of MLC modeling after commissioning the Varian TrueBeam LINAC in Pinnacle version 9.2. Methods: Stepand-shoot IMRT QAs were investigated when we observed our measured absolute dose results using ion chamber (Capintec PR-05P) were uncharacteristically low; about 4–5% compared to doses calculated by Pinnacle{sup 3} (Phillips, Madison, WI). This problem was predominant for large and highly modulated head and neck (HN) treatments. Intuitively we knew this had to be related to shortcomings in the MLC modeling in Pinnacle. Using film QA we were able to iteratively adjust the MLC parameters. We confirmed results by re-testing five failed IMRT QA patients; and ion chamber measurements were verified in Quasar anthropomorphic phantom. Results: After commissioning the LINAC in Pinnacle version 9.2, the MLC transmission for 6X, 10X and 15X were 2.0%, 1.7% and 2.0%, respectively, and additional Interleaf leakage for all three energies was 0.5%. These parameters were obtained from profiles scanned with an Edge detector (Sun Nuclear, Melbourne, FL) during machine commissioning. A Verification testing with radiographic EDR2 film (Kodak, Rochester, NY) measurement was performed by creating a closed MLC leaf pattern and analyzing using RIT software (RIT, Colorado Springs, CO). This reduced MLC transmission for 6X, 10X and 15X to 0.7%, 0.9% and 0.9%, respectively; while increasing additional Interleaf leakage for all three energies to 1.0%. Conclusion: Radiographic film measurements were used to correct MLC transmission values for step and shoot IMRT fields used in Pinnacle version 9.2. After adjusting the MLC parameters to correlate with the film QA, there was still very good agreement between the Pinnacle model and commissioning data. Using the same QA methodology, we were also able to improve the beam models for the Varian C-series linacs, Novalis-Tx, and TrueBeam M-120 linacs.

  7. Analysis of polynuclear aromatic hydrocarbons in olive oil after solid-phase extraction using a dual-layer sorbent cartridge followed by high-performance liquid chromatography with fluorescence detection.

    Science.gov (United States)

    Stenerson, Katherine K; Shimelis, Olga; Halpenny, Michael R; Espenschied, Ken; Ye, Maochun M

    2015-05-27

    A simple and easy direct solid-phase extraction (SPE) method was developed for the analysis of polynuclear aromatic hydrocarbons (PAHs) in olive oil using a dual-layer cartridge containing activated Florisil and a mixture of octadecyl (C18)-bonded and zirconia-coated silicas. Undiluted olive oil was applied directly to the SPE cartridge, and the sample was eluted with acetonitrile solvent. Background in the extract was found to be low enough for either gas chromatography-mass spectrometry (GC-MS) or high-performance liquid chromatography with fluorescence detection (HPLC-FLD) analysis. Average recoveries for 16 different PAHs from spiked olive oil replicates were >75%, with intraday precisions of <20% relative standard deviation (% RSD). Detection limits ranged from 0.2 to 1.0 μg/kg and, specifically for the PAHs listed in EC Regulation 835/2011, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, and benzo(a)pyrene, were from 0.3 to 0.7 μg/kg. The method was then applied to determine the PAH content present in commercial samples of refined versus extra-virgin olive oils.

  8. Implementation of intensity modulation with dynamic multileaf collimation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, J.W.; Yu, C.; Jaffray, D. [William Beaumont Hospital, Royal Oak, MI (United States)

    1995-12-01

    The computer-controlled multileaf collimator (MLC) marks one of the most important advances in radiation therapy. The device efficiently replaces manual blocking to shape fields and can be used to modulate beam intensity. The results of a research programme at William Beaumont Hospital, aimed at bringing dynamic intensity modulation into clinical use, are discussed.

  9. MLC Libraries--A School Library's Journey with Students, Staff and Web 2.0 Technologies: Blogs, Wikis and E-Books--Where Are We Going Next?

    Science.gov (United States)

    Viner, Jane; Lucas, Amanda; Ricchini, Tracey; Ri, Regina

    2010-01-01

    This workshop paper explores the Web 2.0 journey of the MLC Libraries' teacher-librarians, librarian, library and audio visual technicians. Our journey was initially inspired by Will Richardson and supported by the School Library Association of Victoria (SLAV) Web 2.0 professional development program. The 12 week technological skills program…

  10. A Multistage Longitudinal Comparative (MLC) Design Stage II: Evaluation of the Changing Lives Program (CLP)--The Possible Selves Questionnaire-Qualitative Extensions (PSQ-QE)

    Science.gov (United States)

    Kortsch, Gabrielle; Kurtines, William M.; Montgomery, Marilyn J.

    2008-01-01

    The study reported in this paper, a Multistage Longitudinal Comparative (MLC) Design Stage II evaluation conducted as a planned preliminary efficacy evaluation (psychometric evaluation of measures, short-term controlled outcome studies, etc.) of the Changing Lives Program (CLP), provided evidence for the reliability and validity of qualitative…

  11. Development of an iterative reconstruction method to overcome 2D detector low resolution limitations in MLC leaf position error detection for 3D dose verification in IMRT

    NARCIS (Netherlands)

    Visser, Ruurd; Godart, J.; Wauben, D. J. L.; Langendijk, J. A.; van't Veld, A. A.; Korevaar, E. W.

    2016-01-01

    The objective of this study was to introduce a new iterative method to reconstruct multi leaf collimator (MLC) positions based on low resolution ionization detector array measurements and to evaluate its error detection performance. The iterative reconstruction method consists of a fluence model, a

  12. 双层预紧式六维力传感器及其静态标定%Dual Layers Pre-stressed Six-axis Force Sensor and Its Static Calibration

    Institute of Scientific and Technical Information of China (English)

    王志军; 姚建涛; 吴遥; 叶冬; 赵永生

    2013-01-01

    针对基于传统Stewart结构六维力传感器在解耦、刚度等方面性能的不足,设计并研制一种双层预紧式六维力传感器,并对其进行静态标定试验研究.所设计的六维力传感器采用球窝锥头式球面副代替传统球副,有效地减小了球副的摩擦力矩,另外测量分支只承受压力,消除了力在换向时对接触球面的冲击,提高了整体刚度.基于螺旋理论推导出传感器所施加外力与测量分支轴向力之间的映射关系,进而说明预紧式六维力传感器的测量原理.采用最小二乘线性化标定方法对传感器进行静态解耦和测量误差分析,推导出传感器的标定矩阵和误差矩阵.研制出双层预紧式六维力传感器样机,并进行静态标定试验.经过标定试验,该传感器各方向最大非线性度误差低于满量程的1.17%,最大耦合误差低于满量程的1.82%.试验结果表明双层预紧式六维力传感器具有很高的测量精度,可用于工业生产中对六维力测量要求较高的场合.%According to the deficiency of performance of the traditional six-axis force sensor based on Stewart platform structure on decoupling and stiffness, a pre-stressed six-axis force sensor with dual layers is designed and developed, and the static calibration of the sensor is carried out. The proposed six-axis force sensor uses cone-socket type spherical joint instead of the traditional one, which reduces the friction torque of spherical pair effectively and eliminates the commutation impact force for the measuring limbs compressed all the time, so the overall stiffness is improved. Based on screw theory, the mapping of the applied external force and the axial force of measuring limbs of the sensor is derived, and then the measuring principle of the pre-stressed six-axis force sensor is described. Analysis of static decoupling and measurement error of the sensor is conducted by using linear least squares calibration method, and

  13. 用于燃气锅炉低碳钢耐冲蚀-腐蚀磨损的双层热喷涂层%Thermal Sprayed Dual-layer Coatings for Steel Protection against Corrosion-Erosion at Power Boilers

    Institute of Scientific and Technical Information of China (English)

    王卜谦; 税正荣; 王海斗

    2001-01-01

    为防护发电厂锅炉的热交换器管道的腐蚀冲蚀磨损,研究开发了一种热喷涂双层涂层(高速火焰喷涂Cr3C2/TiC–25NiCr涂层+燃烧电弧喷涂Ni21Cr9Mo35Nb涂层).在锅炉管道上实际应用两年后,对这种双涂层进行冲蚀试验和金相分析,并对其性能进行讨论.结果发现,燃烧电弧喷涂Ni21Cr9Mo3.5Nb涂层在高硫及氯环境中是一种良好的防护涂层.%The heat exchanger tubes of power plant boilers suffer from corrosion-erosion by ash particles and corrosive gases attack at elevated temperatures. The tube wastage rate depends on the boiler design and operation, the characteristics of ash particles, environment conditions, and tube materials. Thermal sprayed dual-layer coatings (HVOF Cr3C2/TiC-25NiCr coating and combustion arc-sprayed Ni21Cr9Mo3.5Nb coating) were developed for the tube corrosion-erosion protection. The erosion test comparison and metallographic examination of the coated tube after two years service in boiler were presented and its performance was discussed. The combustion arc-sprayed Ni21Cr9Mo3.5Nb coating was found a good solution for relatively high sulfur and chlorine environment.

  14. Inter-layer charge disproportionation in the dual-layer organic metal (tTTF-I)2ClO4 with unsymmetrical I···O halogen bond interactions.

    Science.gov (United States)

    Shin, Kyoung-Soon; Jeannin, Olivier; Brezgunova, Mariya; Dahaoui, Slimane; Aubert, Emmanuel; Espinosa, Enrique; Auban-Senzier, Pascale; Świetlik, Roman; Frąckowiak, Arkadiusz; Fourmigué, Marc

    2014-04-14

    A mixed-valence salt of tTTF-I with ClO4(-), formulated as (tTTF-I)2ClO4, is characterized by the presence of two crystallographically independent donor molecules, segregated in different layers and linked together through I···O interactions with the ClO4(-) anion disordered at room temperature. The tTTF-I donor molecule was prepared by metallation of tTTF (trimethylene tetrathiafulvalene) followed by reaction with iodine to afford the mono and diiodo derivatives tTTF-I and tTTFI2, respectively. The crystal structure of the latter neutral tTTFI2 shows the occurrence of strong type II, II halogen bond interactions. Band structure calculations of the dual-layer structure of the 2 : 1 salt (tTTF-I)2ClO4 show co-existence of both 1D open and 2D closed Fermi surfaces. The salt undergoes a metal-insulator phase transition at T(MI) = 90 K, associated with an electronic dimensionality decrease, since already at 100 K, the 2D part of the Fermi surface transforms into 1D corrugated planes. High resolution X-ray investigations performed at 100 K, combined with multipolar refinements, indicate an approximately equivalent +0.5e charge in both donor molecules, as also deduced from the intramolecular bond distances. On the other hand, Raman spectroscopic investigations show that at ambient temperature the charge is actually distributed non-uniformly in conducting layers of tTTF-I molecules, with the identification of molecules with charges +1, +0.5, 0e, while at low temperature the charge distribution becomes essentially uniform (+0.5e), as confirmed from the X-ray high resolution data. These apparently contradictory behaviors are actually a consequence of a partial electron transfer between the two independent slabs to reach a common Fermi level in the metallic phase.

  15. Microwave assisted sol-gel synthesis of high dielectric constant CCTO and BFN ceramics for MLC applications

    Directory of Open Access Journals (Sweden)

    Sonia

    2017-06-01

    Full Text Available Ba(Fe1/2Nb1/2O3 (BFN and CaCu3Ti4O12 (CCTO ceramic powders were synthesized by microwave assisted sol-gel synthesis technique and sintered at 1100°C and 1000°C, respectively. Calcination and sintering processes were carried out in a microwave furnace. Dielectric constant (εr~2450 and dielectric loss (tan δ~0.5 at frequency of 1 kHz and 20°C were observed for the BFN ceramic samples. Higher value of εr ~ 3600 and lower value of tan δ ~ 0.07 at frequency of 1 kHz and in 20-60°C temperature range for the CCTO ceramic samples suggested its utility for MLC applications. Sharp decrease of εr and sharp increase of tan δ at higher frequencies of BFN ceramic samples indicated the presence of Debye like relaxation.

  16. Pennogenin tetraglycoside induces rat myometrial contraction and MLC20 phosphorylation via PLC-IP(3 and RhoA/Rho kinase signaling pathways.

    Directory of Open Access Journals (Sweden)

    Limei Wang

    Full Text Available BACKGROUND: Total steroidal saponins extracted from the rhizome of Paris polyphylla Sm. var. yunnanensis (TSSPs have been widely used in China for the treatment of abnormal uterine bleeding. We previously studied the main active constituents of TSSPs and their structure-activity relationships with respect to rat myometrial contractions. Tg (pennogenin tetraglycoside was identified as one of the active ingredients in TSSPs able to induce rat myometrial contractions. However, the mechanisms underlying the pharmacological actions on uterine activity have not been described clearly. METHODS: Here Tg was screened for effects on contractile activity in isolated uterine strips from estrogen-primed rats and on MLC20 phosphorylation and related signaling pathways in cultured rat myometrial cells as determined by Western blot. Intracellular calcium ([Ca(2+](i was monitored under a confocal microscope using Fluo-4 AM-loaded myometrial cells. RESULTS: Tg dose-dependently stimulated rat myometrial contractions as well as MLC20 phosphorylation in vitro, which could be completely suppressed by an inhibitor of myosin light chain kinase (MLCK. Use of Ca(2+ channel blockers and kinase inhibitors demonstrated that Tg-induced myometrial contractions are mediated by activation of the phospholipase C (PLC-inositol triphosphate (IP3 signaling pathway, resulting in increased MLC20 phosphorylation. Furthermore, Y27632, a specific inhibitor of Rho kinase (ROK, notably suppressed Tg-stimulated myometrial contractions and decreased MLC20 phosphorylation. CONCLUSIONS: These data provide evidence that rat myometrial contractility induced by Tg results from enhanced MLC20 phosphorylation, while both PLC-IP3 and RhoA/ROK signaling pathways mediate the process. These mechanisms may be responsible for the therapeutic effects of TSSPs on abnormal uterine bleeding.

  17. The use of intensity-modulated radiation therapy photon beams for improving the dose uniformity of electron beams shaped with MLC

    Energy Technology Data Exchange (ETDEWEB)

    Mosalaei, Homeira, E-mail: homeira.mosalaei@lhsc.on.ca [London Regional Cancer Program, London Health Science Centre, Ontario (Canada); Karnas, Scott [London Regional Cancer Program, London Health Science Centre, Ontario (Canada); University of Waterloo, Waterloo, Ontario (Canada); Shah, Sheel [University of Western Ontario, London, Ontario (Canada); Van Doodewaard, Sharon [McMaster University, Hamilton, Ontario (Canada); Foster, Tim [University of Western Ontario, London, Ontario (Canada); Chen, Jeff [London Regional Cancer Program, London Health Science Centre, Ontario (Canada); University of Waterloo, Waterloo, Ontario (Canada)

    2012-04-01

    Electrons are ideal for treating shallow tumors and sparing adjacent normal tissue. Conventionally, electron beams are collimated by cut-outs that are time-consuming to make and difficult to adapt to tumor shape throughout the course of treatment. We propose that electron cut-outs can be replaced using photon multileaf collimator (MLC). Two major problems of this approach are that the scattering of electrons causes penumbra widening because of a large air gap, and available commercial treatment planning systems (TPSs) do not support MLC-collimated electron beams. In this study, these difficulties were overcome by (1) modeling electron beams collimated by photon MLC for a commercial TPS, and (2) developing a technique to reduce electron beam penumbra by adding low-energy intensity-modulated radiation therapy (IMRT) photons (4 MV). We used blocks to simulate MLC shielding in the TPS. Inverse planning was used to optimize boost photon beams. This technique was applied to a parotid and a central nervous system (CNS) clinical case. Combined photon and electron plans were compared with conventional plans and verified using ion chamber, film, and a 2D diode array. Our studies showed that the beam penumbra for mixed beams with 90 cm source to surface distance (SSD) is comparable with electron applicators and cut-outs at 100 cm SSD. Our mixed-beam technique yielded more uniform dose to the planning target volume and lower doses to various organs at risk for both parotid and CNS clinical cases. The plans were verified with measurements, with more than 95% points passing the gamma criteria of 5% in dose difference and 5 mm for distance to agreement. In conclusion, the study has demonstrated the feasibility and potential advantage of using photon MLC to collimate electron beams with boost photon IMRT fields.

  18. Deleted in liver cancer 1 (DLC1 negatively regulates Rho/ROCK/MLC pathway in hepatocellular carcinoma.

    Directory of Open Access Journals (Sweden)

    Carmen Chak-Lui Wong

    Full Text Available AIMS: Deleted in liver cancer 1 (DLC1, a member of RhoGTPase activating protein (GAP family, is known to have suppressive activities in tumorigenicity and cancer metastasis. However, the underlying molecular mechanisms of how DLC1 suppresses cell motility have not been fully elucidated. Rho-kinase (ROCK is an immediate down-stream effector of RhoA in mediating cellular cytoskeletal events and cell motility. In the present study, we aimed to investigate the effects of DLC1 on Rho/ROCK signaling pathway in hepatocellular carcinoma (HCC. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrated that DLC1 negatively regulated ROCK-dependent actomyosin contractility. From immunofluorescence study, we found that ectopic expression of DLC1 abrogated Rho/ROCK-mediated cytoskeletal reorganization including formation of stress fibers and focal adhesions. It also downregulated cortical phosphorylation of myosin light chain 2 (MLC2. These inhibitory events by DLC1 were RhoGAP-dependent, as RhoGAP-deficient mutant of DLC1 (DLC1 K714E abolished these inhibitory events. In addition, from western study, DLC1 inhibited ROCK-related myosin light chain phosphatase targeting unit 1 (MYPT1 phosphorylation at Threonine 853. By examining cell morphology under microscope, we found that ectopic expression of dominant-active ROCK released cells from DLC1-induced cytoskeletal collapse and cell shrinkage. CONCLUSION: Our data suggest that DLC1 negatively regulates Rho/ROCK/MLC2. This implicates a ROCK-mediated pathway of DLC1 in suppressing metastasis of HCC cells and enriches our understanding in the molecular mechanisms involved in the progression of hepatocellular carcinoma.

  19. Intensity- and energy-modulated electron radiotherapy by means of an xMLC for head and neck shallow tumors

    Energy Technology Data Exchange (ETDEWEB)

    Salguero, Francisco Javier; Palma, Bianey Atriana; Leal, Antonio [Departamento de FisiologIa Medica y Biofisica, Universidad de Sevilla (Spain); Arrans, Rafael [Hospital Universitario Virgen Macarena, Sevilla (Spain)], E-mail: alplaza@us.es

    2010-03-07

    The purpose of this paper is to assess the feasibility of delivering intensity- and energy-modulated electron radiation treatment (MERT) by a photon multileaf collimator (xMLC) and to evaluate the improvements obtained in shallow head and neck (HN) tumors. Four HN patient cases covering different clinical situations were planned by MERT, which used an in-house treatment planning system that utilized Monte Carlo dose calculation. The cases included one oronasal, two parotid and one middle ear tumors. The resulting dose-volume histograms were compared with those obtained from conventional photon and electron treatment techniques in our clinic, which included IMRT, electron beam and mixed beams, most of them using fixed-thickness bolus. Experimental verification was performed with plane-parallel ionization chambers for absolute dose verification, and a PTW ionization chamber array and radiochromic film for relative dosimetry. A MC-based treatment planning system for target with compromised volumes in depth and laterally has been validated. A quality assurance protocol for individual MERT plans was launched. Relative MC dose distributions showed a high agreement with film measurements and absolute ion chamber dose measurements performed at a reference point agreed with MC calculations within 2% in all cases. Clinically acceptable PTV coverage and organ-at-risk sparing were achieved by using the proposed MERT approach. MERT treatment plans, based on delivery of intensity-modulated electron beam using the xMLC, for superficial head and neck tumors, demonstrated comparable or improved PTV dose homogeneity with significantly lower dose to normal tissues. The clinical implementation of this technique will be able to offer a viable alternative for the treatment of shallow head and neck tumors.

  20. SU-E-T-475: An Accurate Linear Model of Tomotherapy MLC-Detector System for Patient Specific Delivery QA

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y; Mo, X; Chen, M; Olivera, G; Parnell, D; Key, S; Lu, W [21st Century Oncology, Madison, WI (United States); Reeher, M [21st Century Oncology, Naples, FL (United States); Galmarini, D [21st Century Oncology, Fort Myers, FL (United States)

    2014-06-01

    Purpose: An accurate leaf fluence model can be used in applications such as patient specific delivery QA and in-vivo dosimetry for TomoTherapy systems. It is known that the total fluence is not a linear combination of individual leaf fluence due to leakage-transmission, tongue-and-groove, and source occlusion effect. Here we propose a method to model the nonlinear effects as linear terms thus making the MLC-detector system a linear system. Methods: A leaf pattern basis (LPB) consisting of no-leaf-open, single-leaf-open, double-leaf-open and triple-leaf-open patterns are chosen to represent linear and major nonlinear effects of leaf fluence as a linear system. An arbitrary leaf pattern can be expressed as (or decomposed to) a linear combination of the LPB either pulse by pulse or weighted by dwelling time. The exit detector responses to the LPB are obtained by processing returned detector signals resulting from the predefined leaf patterns for each jaw setting. Through forward transformation, detector signal can be predicted given a delivery plan. An equivalent leaf open time (LOT) sinogram containing output variation information can also be inversely calculated from the measured detector signals. Twelve patient plans were delivered in air. The equivalent LOT sinograms were compared with their planned sinograms. Results: The whole calibration process was done in 20 minutes. For two randomly generated leaf patterns, 98.5% of the active channels showed differences within 0.5% of the local maximum between the predicted and measured signals. Averaged over the twelve plans, 90% of LOT errors were within +/−10 ms. The LOT systematic error increases and shows an oscillating pattern when LOT is shorter than 50 ms. Conclusion: The LPB method models the MLC-detector response accurately, which improves patient specific delivery QA and in-vivo dosimetry for TomoTherapy systems. It is sensitive enough to detect systematic LOT errors as small as 10 ms.

  1. SU-E-T-363: Error Detection Comparison of EPID and MLC Log File Based IMRT QA Systems

    Energy Technology Data Exchange (ETDEWEB)

    Defoor, D; Obeidat, M; Linden, P; Kirby, N; Papanikolaou, N; Stathakis, S [University of Texas Health Science Center at San Antonio, San Antonio, TX (United States); Mavroidis, P [University of North Carolina, Chapel Hill, NC (United States)

    2015-06-15

    Purpose: In this study we will compare the ability of three QA methods (Delta4, MU-EPID, Dynalog QA) to detect specific errors. Methods: A Varian Novalis Tx with a HD120 MLC and aS1000 Electronic Portal Imaging Device (EPID) was used in our study. Multi-leaf collimator (MLC) errors, gantry angle and dose errors were introduced into 5 volumetric arc therapy (VMAT) plans. 3D dose distributions calculated with data from the EPID and Dynalog QA methods were compared with the planned dose distribution. The gamma passing percentages as well as percentage error of planning target volume (PTV) dose were used for passing determination. Baselines for gamma passing percentages and PTV dose were established by measuring the original plan 5 times consecutively. Standard passing thresholds as well as thresholds derived from receiver operator characteristic (ROC) analysis and 2 standard deviation (SD) criteria were used. Results: When applying the standard 95% pass rate at 3%/3mm gamma analysis 14, 21 and 8 of 30 errors were detected by the Delta4, MU-EPID and Dynalog QA methods respectively. Thresholds set at 2 SD from our base line measurements resulted in the detection of 18, 9 and 14 of 30 errors for the Delta4, MU-EPID and Dynalog QA methods respectively. When using D2 of the PTV as a metric the Dynalog QA detected 20 of 30 errors while the EPID method detected 14 of 30 errors. Using D98 of the PTV, Dynalog QA detected 13 of 30 while the EPID detected 3 of 30 errors. Conclusion: Although MU-EPID detected the most errors at the standard 95% cutoff it also produced the most false detections in the baseline data. The Dynalog QA was the most effective when the ROC adjusted passing threshold was used. D2 was more effective as a metric for detecting errors than D98.

  2. 斑鳜轻链3基因(MLC3)cDNA的克隆及纵向表达分析%cDNA Cloning and Vertical Expression Analysis of the Myosin Light Chain 3 ( MLC3 ) Gene in Siniperca Scherzeri

    Institute of Scientific and Technical Information of China (English)

    农小献; 赵发兰; 宾石玉; 陈敦学; 刘希良; 史竸; 褚武英

    2011-01-01

    提取斑鳜肌肉组织总RNA,逆转录得到cDNA,然后利用常规PCR法扩增得到斑鳜肌球蛋白轻链3基因(MLC3)序列.斑鳜MLC3基因cDNA序列的全长为532 bp,编码150个氨基酸.通过PROSITE tools软件预测显示该序列具有2个EF-手相结构.通过实时荧光定量PCR法对斑鳜MLC3纵向表达进行分析发现,MLC3在斑鳜背肌的近头部、中部和近尾部都有表达,近头部和中部的表达量差异不显著,近尾部表达量显著高于近头部和中部.%RNA of Siniperca scherzeri was isolated from muscle tissue, applied differential display reversed transcripted PCR (DDRT-PCR) technique to get cDNA sequence of MLC3, which is 532 bp in length, and encodes a 150 amino acid peptide.It is found that it contains two EF-hand motifs by using the indicating PROSITE tools software.Longitudinal expression of mandarin fish was studied by using Real-time Quantitative PCR showed that the MLC3 mRNA was expressed along longitudinal axis with unsignificant between the anterior and middle muscle positions, but significant variation between the posterior and anterior, middle muscle positions.

  3. Machine learning control taming nonlinear dynamics and turbulence

    CERN Document Server

    Duriez, Thomas; Noack, Bernd R

    2017-01-01

    This is the first book on a generally applicable control strategy for turbulence and other complex nonlinear systems. The approach of the book employs powerful methods of machine learning for optimal nonlinear control laws. This machine learning control (MLC) is motivated and detailed in Chapters 1 and 2. In Chapter 3, methods of linear control theory are reviewed. In Chapter 4, MLC is shown to reproduce known optimal control laws for linear dynamics (LQR, LQG). In Chapter 5, MLC detects and exploits a strongly nonlinear actuation mechanism of a low-dimensional dynamical system when linear control methods are shown to fail. Experimental control demonstrations from a laminar shear-layer to turbulent boundary-layers are reviewed in Chapter 6, followed by general good practices for experiments in Chapter 7. The book concludes with an outlook on the vast future applications of MLC in Chapter 8. Matlab codes are provided for easy reproducibility of the presented results. The book includes interviews with leading r...

  4. Regulation of PTS gene expression by the homologous transcriptional regulators, Mlc and NagC, in Escherichia coli (or how two similar repressors can behave differently).

    Science.gov (United States)

    Plumbridge, J

    2001-07-01

    NagC and Mlc are paralogous transcriptional repressors in E.coli. Unexpectedly they possess almost identical amino acid sequences in their helix-turn-helix (H-T-H), DNA binding motif and they bind to very similar consensus operator targets. Binding to each others sites can be demonstrated in vitro but no cross regulation can be detected in vivo with physiological amounts of the two proteins. Although both proteins are involved in regulating the expression of PTS genes, the characteristics of their repression and induction are very different. NagC is a dual-function, activator-repressor which co-ordinates the metabolism of the amino sugars, N-acetylglucosamine (GlcNAc) and glucosamine, by repressing the divergent nagE-BA operons and by activating the glmUS operon. Repression (and activation) by NagC requires that NagC binds simultaneously to two operators, thus forming a DNA loop. This chelation effect allows use of lower affinity sites which would not individually bind the repressor. The specific inducer for NagC is GlcNAc-6-P, the product of GlcNAc transport by the PTS and a key compound in amino sugar metabolism. Mlc represses several genes implicated in the uptake of glucose; ptsG, ptsHI and manXYZ, and malT, the activator of the mal regulon. Glucose behaves like the inducer but growth on glucose only produces an overall increase in expression for ptsG and ptsHI. All Mlc repressed genes are also controlled by cAMP/CAP, so that glucose affects their transcription in two opposing ways: increasing expression by acting as the inducer for Mlc but decreasing expression by lowering the cAMP/CAP concentration. The Mlc protein is not directly responsive to glucose per se but to the activity status of the PTS. Displacement of Mlc from its binding sites occurs during growth on glucose and other PTS sugars and involves sequestration of the repressor to membranes by binding to dephosphorylated PtsG.

  5. Improvements in dose accuracy delivered with static-MLC IMRT on an integrated linear accelerator control system

    Energy Technology Data Exchange (ETDEWEB)

    Li Ji; Wiersma, Rodney D.; Stepaniak, Christopher J.; Farrey, Karl J.; Al-Hallaq, Hania A. [Department of Radiation and Cellular Oncology, University of Chicago, 5758 South Maryland Avenue, MC9006, Chicago, Illinois 60637 (United States)

    2012-05-15

    Purpose: Dose accuracy has been shown to vary with dose per segment and dose rate when delivered with static multileaf collimator (SMLC) intensity modulated radiation therapy (IMRT) by Varian C-series MLC controllers. The authors investigated the impact of monitor units (MUs) per segment and dose rate on the dose delivery accuracy of SMLC-IMRT fields on a Varian TrueBeam linear accelerator (LINAC), which delivers dose and manages motion of all components using a single integrated controller. Methods: An SMLC sequence was created consisting of ten identical 10 x 10 cm{sup 2} segments with identical MUs. Beam holding between segments was achieved by moving one out-of-field MLC leaf pair. Measurements were repeated for various combinations of MU/segment ranging from 1 to 40 and dose rates of 100-600 MU/min for a 6 MV photon beam (6X) and dose rates of 800-2400 MU/min for a 10 MV flattening-filter free photon (10XFFF) beam. All measurements were made with a Farmer (0.6 cm{sup 3}) ionization chamber placed at the isocenter in a solid-water phantom at 10 cm depth. The measurements were performed on two Varian LINACs: C-series Trilogy and TrueBeam. Each sequence was delivered three times and the dose readings for the corresponding segments were averaged. The effects of MU/segment, dose rate, and LINAC type on the relative dose variation ({Delta}{sub i}) were compared using F-tests ({alpha} = 0.05). Results: On the Trilogy, large {Delta}{sub i} was observed in small MU segments: at 1 MU/segment, the maximum {Delta}{sub i} was 10.1% and 57.9% at 100 MU/min and 600 MU/min, respectively. Also, the first segment of each sequence consistently overshot ({Delta}{sub i} > 0), while the last segment consistently undershot ({Delta}{sub i} < 0). On the TrueBeam, at 1 MU/segment, {Delta}{sub i} ranged from 3.0% to 4.5% at 100 and 600 MU/min; no obvious overshoot/undershoot trend was observed. F-tests showed statistically significant difference [(1 - {beta}) =1.0000] between the

  6. Dosimetric and delivery efficiency investigation for treating hepatic lesions with a MLC-equipped robotic radiosurgery–radiotherapy combined system

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Lihui, E-mail: lihui.jin@fccc.edu; Price, Robert A.; Wang, Lu; Meyer, Joshua; Fan, James; Charlie Ma, Chang Ming [Department of Radiation Oncology, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111 (United States)

    2016-02-15

    Purpose: The CyberKnife M6 (CK-M6) Series introduced a multileaf collimator (MLC) for extending its capability from stereotactic radiosurgery/stereotactic radiotherapy (SBRT) to conventionally fractionated radiotherapy. This work is to investigate the dosimetric quality of plans that are generated using MLC-shaped beams on the CK-M6, as well as their delivery time, via comparisons with the intensity modulated radiotherapy plans that were clinically used on a Varian Linac for treating hepatic lesions. Methods: Nine patient cases were selected and divided into three groups with three patients in each group: (1) the group-one patients were treated conventionally (25 fractions); (2) the group-two patients were treated with SBRT-like hypofractionation (5 fractions); and (3) the group-three patients were treated similar to group-one patients, but with two planning target volumes (PTVs) and two different prescription dose levels correspondingly. The clinically used plans were generated on the ECLIPSE treatment planning system (TPS) and delivered on a Varian Linac (E-V plans). The multiplan (MP) TPS was used to replan these clinical cases with the MLC as the beam device for the CK-M6 (C-M plans). After plans were normalized to the same PTV dose coverage, comparisons between the C-M and E-V plans were performed based on D{sub 99%} (percentage of prescription dose received by 99% of the PTV), D{sub 0.1cm{sup 3}} (the percentage of prescription dose to 0.1 cm{sup 3} of the PTV), and doses received by critical structures. Then, the delivery times for the C-M plans will be obtained, which are the MP TPS generated estimations assuming having an imaging interval of 60 s. Results: The difference in D{sub 99%} between C-M and E-V plans is +0.6% on average (+ or − indicating a higher or lower dose from C-M plans than from E-V plans) with a range from −4.1% to +3.8%, and the difference in D{sub 0.1cm{sup 3}} was −1.0% on average with a range from −5.1% to +2.9%. The PTV

  7. Preliminary studies for implementation of a MCL quality control using EPID (Portal Dosimetry); Estudos preliminares para implementacao de um controle de qualidade de MLC com o uso do EPID (Portal Dosimetry)

    Energy Technology Data Exchange (ETDEWEB)

    Mattos, Fabio R.; Furnari, Laura [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Faculdade de Medicina

    2016-07-01

    A Quality Control (CQ) to ensure the expected performance of a Multileaf Collimator System (MLC) is essential for delivering dose in a safety and appropriate way. The time required for equipment control and dosimetry may be lowered when the Electronic Portal Image Device (EPID) is used. The aim of this paper was to check the resolution limits of the detection system for IMRT mode, and to do the analysis of three tests of MLC performance: Picket Fence, Slinding GAP, MLC versus Gantry. A Varian iX Clinac equipped with an 80 leaf Millennium MLC and with amorphous silicon based EPID (aS1000) was use. The EPID proved Effective, where errors up to 0,5 mm can be detected. Information about interleaf transmissions, dose profile and gravity influence in the leaf banks also were included. (author)

  8. Effects of tertiary MLC configuration on secondary neutron spectra from 18 MV x-ray beams for the Varian 21EX linear accelerator.

    Science.gov (United States)

    Howell, Rebecca M; Kry, Stephen F; Burgett, Eric; Followill, David; Hertel, Nolan E

    2009-09-01

    The effect of the jaw configuration and the presence and configuration of the tertiary multileaf collimator (MLC) on the secondary neutron spectra for an 18 MV Varian 21EX linear accelerator (linac) is investigated in detail. The authors report the measured spectra for four collimator (jaw-and-MLC) configurations. These configurations represent the extreme settings of the jaws and MLC and should therefore describe the range of possible fluence and spectra that may be encountered during use of this linac. In addition to measurements, a Monte Carlo model was used to simulate the four collimator configurations and calculate the energy spectra and fluence at the same location as it was measured. The Monte Carlo model was also used to calculate the sources of neutron production in the linac head for each collimator configuration. They found that photoneutron production in the linac treatment head is dominated by the order in which the primary photon beam intercepts the high-Z material. The primary collimator, which has the highest position in the linac head (in a fixed location), is the largest source of secondary neutrons. Thereafter, the collimator configuration plays a role in where the neutrons originate. For instance, if the jaws are closed, they intercept the beam and contribute substantially to the secondary neutron production. Conversely, if the jaws are open, the MLC plays a larger role in neutron production (assuming, of course, that it intercepts the beam). They found that different collimator configurations make up to a factor of 2 difference in the ambient dose equivalent.

  9. Melatonin Attenuates Aortic Endothelial Permeability and Arteriosclerosis in Streptozotocin-Induced Diabetic Rats: Possible Role of MLCK- and MLCP-Dependent MLC Phosphorylation.

    Science.gov (United States)

    Tang, Song-tao; Su, Huan; Zhang, Qiu; Tang, Hai-qin; Wang, Chang-jiang; Zhou, Qing; Wei, Wei; Zhu, Hua-qing; Wang, Yuan

    2016-01-01

    The development of diabetic macrovascular complications is a multifactorial process, and melatonin may possess cardiovascular protective properties. This study was designed to evaluate whether melatonin attenuates arteriosclerosis and endothelial permeability by suppressing the myosin light-chain kinase (MLCK)/myosin light-chain phosphorylation (p-MLC) system via the mitogen-activated protein kinase (MAPK) signaling pathway or by suppressing the myosin phosphatase-targeting subunit phosphorylation (p-MYPT)/p-MLC system in diabetes mellitus (DM). Rats were randomly divided into 4 groups, including control, high-fat diet, DM, and DM + melatonin groups. Melatonin was administered (10 mg/kg/d) by gavage for 12 weeks. The DM significantly increased the serum fasting blood glucose and lipid levels, as well as insulin resistance and endothelial dysfunction, which were attenuated by melatonin therapy to various extents. Importantly, the aortic endothelial permeability was significantly increased in DM rats but was dramatically reversed following treatment with melatonin. Our findings further indicated that hyperglycemia and hyperlipidemia enhanced the expressions of MLCK, p-MYPT, and p-MLC, which were partly associated with decreased membrane type 1 expression, increased extracellular signal-regulated kinase (ERK) phosphorylation, and increased p38 expression. However, these changes in protein expression were also significantly reversed by melatonin. Thus, our results are the first to demonstrate that the endothelial hyperpermeability induced by DM is associated with increased expressions of MLCK, p-MYPT, and p-MLC, which can be attenuated by melatonin at least partly through the ERK/p38 signaling pathway.

  10. Airborne particulate matter in vitro exposure induces cytoskeleton remodeling through activation of the ROCK-MYPT1-MLC pathway in A549 epithelial lung cells.

    Science.gov (United States)

    Chirino, Yolanda I; García-Cuellar, Claudia María; García-García, Carlos; Soto-Reyes, Ernesto; Osornio-Vargas, Álvaro Román; Herrera, Luis A; López-Saavedra, Alejandro; Miranda, Javier; Quintana-Belmares, Raúl; Pérez, Irma Rosas; Sánchez-Pérez, Yesennia

    2017-03-06

    Airborne particulate matter with an aerodynamic diameter ≤10μm (PM10) is considered a risk factor for the development of lung cancer. Little is known about the cellular mechanisms by which PM10 is associated with cancer, but there is evidence that its exposure can lead to an acquired invasive phenotype, apoptosis evasion, inflammasome activation, and cytoskeleton remodeling in lung epithelial cells. Cytoskeleton remodeling occurs through actin stress fiber formation, which is partially regulated through ROCK kinase activation, we aimed to investigate if this protein was activated in response to PM10 exposure in A549 lung epithelial cells. Results showed that 10μg/cm(2) of PM10 had no influence on cell viability but increased actin stress fibers, cytoplasmic ROCK expression, and phosphorylation of myosin phosphatase-targeting 1 (MYPT1) and myosin light chain (MLC) proteins, which are targeted by ROCK. The inhibition of ROCK prevented actin stress fiber formation and the phosphorylation of MYPT1 and MLC, suggesting that PM10 activated the ROCK-MYPT1-MLC pathway in lung epithelial cells. The activation of ROCK1 has been involved in the acquisition of malignant phenotypes, and its induction by PM10 exposure could contribute to the understanding of PM10 as a risk factor for cancer development through the mechanisms associated with invasive phenotype.

  11. WE-A-304-01: Strategies and Technologies for Cranial Radiosurgery Planning: MLC-Based Linac

    Energy Technology Data Exchange (ETDEWEB)

    Kim, G. [University of California, San Diego (United States)

    2015-06-15

    The high fractional doses, stringent requirements for accuracy and precision, and surgical perspective characteristic of intracranial radiosurgery create considerations for treatment planning which are distinct from most other radiotherapy procedures. This session will introduce treatment planning techniques specific to two popular intracranial SRS modalities: Gamma Knife and MLC-based Linac. The basic treatment delivery characteristics of each device will be reviewed with a focus on how those characteristics determine the paradigm used for treatment planning. Basic techniques for treatment planning will be discussed, including considerations such as isodose selection, target and organ-at-risk definition, quality indices, and protection of critical structures. Future directions for SRS treatment planning will also be discussed. Learning Objectives: Introduce the basic physical principles of intracranial radiosurgery and how they are realized in the treatment planning paradigms for Gamma Knife and Linac radiosurgery. Demonstrate basic treatment planning techniques. Discuss metrics for evaluating SRS treatment plan quality. Discuss recent and future advances in SRS treatment planning. D. Schlesinger receives research support from Elekta, AB.

  12. A genetic algorithm used for the intensity level discretization in MLC leaf sequencing for step and shoot IMRT

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The inverse planning for a step-and-shoot plan in intensity-modulated radiotherapy(IMRT)is usually a multiple step process.Before being converted into the MLC segments,the optimum intensity profiles of beams,which are generated by an optimization algorithm,shall be discretized into a few intensity levels.The discretization process of the optimum intensity profiles can induce deviations in the final dose distribution from the original optimum dose distribution.This paper describes a genetic algorithm for the discredzation of given optimum intensity profiles.The algorithm minimizes an objective function written in terms of the intensity levels.Both the dose-based objective function,which is defined by the deviation between the dose distributions before and after the discretization,and the intensity-based objective function,which is defined by the deviation between the optimum intensity profiles and the discretization intensity profiles,have been adopted.To evaluate this algorithm,a series of simulation calculations had been carried out using the present algorithm,the even-spaced discredzation and the k-means clustering algorithm respectively.By comparing the resultant diseretization-induced deviations(DIDs)in intensity profiles and in dose distributions,we have found that the genetic algorithm induced less DIDs in comparison with that induced in the even-spaced discretization or the k-means clustering algorithm.Additionally,it has been found that the DIDs created in the genetic algorithm correlate with the complexity of the intensity profiles that is measured by the"fluence map complexity".

  13. A virtual photon source model of an Elekta linear accelerator with integrated mini MLC for Monte Carlo based IMRT dose calculation.

    Science.gov (United States)

    Sikora, M; Dohm, O; Alber, M

    2007-08-07

    A dedicated, efficient Monte Carlo (MC) accelerator head model for intensity modulated stereotactic radiosurgery treatment planning is needed to afford a highly accurate simulation of tiny IMRT fields. A virtual source model (VSM) of a mini multi-leaf collimator (MLC) (the Elekta Beam Modulator (EBM)) is presented, allowing efficient generation of particles even for small fields. The VSM of the EBM is based on a previously published virtual photon energy fluence model (VEF) (Fippel et al 2003 Med. Phys. 30 301) commissioned with large field measurements in air and in water. The original commissioning procedure of the VEF, based on large field measurements only, leads to inaccuracies for small fields. In order to improve the VSM, it was necessary to change the VEF model by developing (1) a method to determine the primary photon source diameter, relevant for output factor calculations, (2) a model of the influence of the flattening filter on the secondary photon spectrum and (3) a more realistic primary photon spectrum. The VSM model is used to generate the source phase space data above the mini-MLC. Later the particles are transmitted through the mini-MLC by a passive filter function which significantly speeds up the time of generation of the phase space data after the mini-MLC, used for calculation of the dose distribution in the patient. The improved VSM model was commissioned for 6 and 15 MV beams. The results of MC simulation are in very good agreement with measurements. Less than 2% of local difference between the MC simulation and the diamond detector measurement of the output factors in water was achieved. The X, Y and Z profiles measured in water with an ion chamber (V = 0.125 cm(3)) and a diamond detector were used to validate the models. An overall agreement of 2%/2 mm for high dose regions and 3%/2 mm in low dose regions between measurement and MC simulation for field sizes from 0.8 x 0.8 cm(2) to 16 x 21 cm(2) was achieved. An IMRT plan film verification

  14. SU-E-T-282: Remove Field-Size Limitation Using the Combination of Collimator Rotation and Jaw Tracking with MLC Aperture

    Energy Technology Data Exchange (ETDEWEB)

    Shiu, A; Chiu, R; Cumming, D; Chung, E; Ragab, O; Cui, G [UniversitySouthern California, Los Angeles, CA (United States)

    2014-06-01

    Purpose: this study is to investigate the use of variable-collimators and/or collimator-rotation to overcome the field-size limitation on TrueBeamSTX. Methods: The maximum static field-size is 22- × 40-cm for TrueBeamSTX and 40- × 40-cm for Trilogy. Maximum displacement between adjacent leaf ends at a single carriage position is 15-cm for TBSTX and 14-cm for Trilogy. Our current practice for IMRT treatment at Trilogy is as follows, if MLC leaves travel more than 13.5 cm in the MLC traveling direction, the treatment fields will be split at isocenter to two groups of IMRT fields to cover the large tumors. However, TrueBeamSTX is not limited in this way because the jaws can track each segments of the MLC aperture. Radiation treatment plans for ten patients (different tumor sites) treated at Trilogy with one dimension of the field is greater than 22 cm and the other dimension is less than or equal to 22 cm. All the plans will be converted with jaws tracking each segment's MLC aperture. If necessary, the collimator rotation will also be applied for the planning. Comparison of the converted plans with the original clinical plans will be evaluated and based on the following criterion: (1) tumor coverage; (2) dose sparing to the critical structures; and (3) treatment time. Results: The tumor coverage is compatible between two plans. The dose of critical structures was evaluated in the cumulative DVH for spinal cord, parotids, and brainstem at V20 and V5. In all patients, the maximum reduction in V20 was never more than 5% and was typically less than 1%. In V5, the maximum reduction was 10% and 3% respectively. The significant difference can be found in using the variable collimator to shorten the treatment time. Conclusion: We conclude that we will use the variable-collimator for all IMRT cases on TrueBeamSTX and as a potential backup machine for Trilogy.

  15. Minocycline Promotes Neurite Outgrowth of PC12 Cells Exposed to Oxygen-Glucose Deprivation and Reoxygenation Through Regulation of MLCP/MLC Signaling Pathways.

    Science.gov (United States)

    Tao, Tao; Feng, Jin-Zhou; Xu, Guang-Hui; Fu, Jie; Li, Xiao-Gang; Qin, Xin-Yue

    2017-04-01

    Minocycline, a semi-synthetic second-generation derivative of tetracycline, has been reported to exert neuroprotective effects both in animal models and in clinic trials of neurological diseases. In the present study, we first investigated the protective effects of minocycline on oxygen-glucose deprivation and reoxygenation-induced impairment of neurite outgrowth and its potential mechanism in the neuronal cell line, PC12 cells. We found that minocycline significantly increased cell viability, promoted neurite outgrowth and enhanced the expression of growth-associated protein-43 (GAP-43) in PC12 cells exposed to oxygen-glucose deprivation/reoxygenation injury. In addition, immunoblots revealed that minocycline reversed the overexpression of phosphorylated myosin light chain (MLC) and the suppression of activated extracellular signal-regulated kinase 1/2 (ERK1/2) caused by oxygen-glucose deprivation/reoxygenation injury. Moreover, the minocycline-induced neurite outgrowth was significantly blocked by Calyculin A (1 nM), an inhibitor of myosin light chain phosphatase (MLCP), but not by an ERK1/2 inhibitor (U0126; 10 μM). These findings suggested that minocycline activated the MLCP/MLC signaling pathway in PC12 cells after oxygen-glucose deprivation/reoxygenation injury, which resulted in the promotion of neurite outgrowth.

  16. An independent system for real-time dynamic multileaf collimation trajectory verification using EPID

    Science.gov (United States)

    Fuangrod, Todsaporn; Woodruff, Henry C.; Rowshanfarzad, Pejman; O'Connor, Daryl J.; Middleton, Richard H.; Greer, Peter B.

    2014-01-01

    A new tool has been developed to verify the trajectory of dynamic multileaf collimators (MLCs) used in advanced radiotherapy techniques using only the information provided by the electronic portal imaging devices (EPID) measured image frames. The prescribed leaf positions are resampled to a higher resolution in a pre-processing stage to improve the verification precision. Measured MLC positions are extracted from the EPID frames using a template matching method. A cosine similarity metric is then applied to synchronise measured and planned leaf positions for comparison. Three additional comparison functions were incorporated to ensure robust synchronisation. The MLC leaf trajectory error detection was simulated for both intensity modulated radiation therapy (IMRT) (prostate) and volumetric modulated arc therapy (VMAT) (head-and-neck) deliveries with anthropomorphic phantoms in the beam. The overall accuracy for MLC positions automatically extracted from EPID image frames was approximately 0.5 mm. The MLC leaf trajectory verification system can detect leaf position errors during IMRT and VMAT with a tolerance of 3.5 mm within 1 s.

  17. Study of the positioning of the films of the MLC by a Test of bands and your influence in the clinic dosimetry in IMRT; Estudio del posicionamiento de las laminas del MLC mediante un test de bandas y su influencia en la dosimetria clinica en IMRT

    Energy Technology Data Exchange (ETDEWEB)

    Serrano Zabaleta, S.; Millan Cebrian, E.; Calvo Carrillo, S.; Alba Escorihuela, V.; Garcia Romero, A.; Ortega Pardina, P.; Canella Anoz, M.; Hernandez Vitoria, A.

    2015-07-01

    We performed a test of adjacent bands inspired by the proposed in AAPM Report No. 72, we provides a parameter characterizing the state of the MLC as to the actual position of its blades. This test has been validated by studying repeatability and reproducibility and has found the correlation between the parameter and creep detected by the ILD. Subsequently it has studied the impact of changes in the positioning of the blades on clinical dosimetry in IMRT patients, reconstructing the patient dose by Matrix Evolution team and Compass software, IBA Dosimetry. (Author)

  18. Dynamics

    CERN Document Server

    Goodman, Lawrence E

    2001-01-01

    Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.

  19. A Monte Carlo model for independent dose verification in IMRT and VMAT for the Varian Novalis TX with high definition MLC

    Directory of Open Access Journals (Sweden)

    Luis Vazquez Quino

    2015-09-01

    Full Text Available Purpose: With intensity modulated radiation therapy (IMRT, the physician can prescribe, design and deliver optimized treatment plans that target the tumor and spare adjacent critical structures. The increased conformity of such plans often comes at the expenses of adding significant complexity to the delivery of the treatment. With volumetrically modulated arc therapy (VMAT, in addition to the modulation of the intensity of the radiation beam, other mechanical parameters such as gantry speed and dose rate are varied during treatment delivery. It is therefore imperative that we develop comprehensive and accurate methods to validate such complex delivery techniques prior to the commencement of the patient’s treatment. Methods: In this study, a Monte Carlo simulation was performed for the high definition multileaf collimator (HD-MLC of a Varian Novalis TX linac. Our simulation is based on the MCSIM code and provides a comprehensive model of the linac head. After validating the model in reference geometries, treatment plans for different anatomical sites were simulated and compared against the treatment planning system (TPS dose calculations. All simulations were performed in a cylindrical water phantom as opposed to the patient anatomy, to remove any complexities associated with density effects. Finally, a comparison through gamma analysis of dose plane between the simulation, the TPS and the measurements from the Matrixx array (IBA was conducted to verify the accuracy of our model against both the measurements and the TPS. Results: Gamma analysis of ten IMRT and ten VMAT cases for different anatomical sites was performed, using a 3%/3 mm passing criterion. The average passing rates were 97.5% and 94.3% for the IMRT and the VMAT plans respectively when comparing the MCSIM and TPS dose calculations. Conclusion: In the present work a Monte Carlo model of a Novalis TX linac which has been tested and benchmarked to produce phase-space files for the

  20. The Effects of Lactobacillus acidophilus on the Intestinal Smooth Muscle Contraction through PKC/MLCK/MLC Signaling Pathway in TBI Mouse Model.

    Directory of Open Access Journals (Sweden)

    Bo Sun

    Full Text Available Clinical studies have shown that probiotics influence gastrointestinal motility. However, the molecular mechanisms by which probiotic Lactobacillus modulates intestinal motility in traumatic brain injury (TBI mouse model have not been explored. In the present study, we provided evidence showing that treatment of TBI mice with Lactobacillus acidophilus significantly improved the terminal ileum villus morphology, restored the impaired interstitial cells of Cajal (ICC and the disrupted ICC networks after TBI, and prevented TBI-mediated inhibition of contractile activity in intestinal smooth muscle. Mechanistically, the decreased concentration of MLCK, phospho-MLC20 and phospho-MYPT1 and increased concentration of MLCP and PKC were observed after TBI, and these events mediated by TBI were efficiently prevented by Lactobacillus acidophilus application. These findings may provide a novel mechanistic basis for the application of Lactobacillus acidophilus in the treatment of TBI.

  1. The Effects of Lactobacillus acidophilus on the Intestinal Smooth Muscle Contraction through PKC/MLCK/MLC Signaling Pathway in TBI Mouse Model.

    Science.gov (United States)

    Sun, Bo; Hu, Chen; Fang, Huan; Zhu, Lina; Gao, Ning; Zhu, Jingci

    2015-01-01

    Clinical studies have shown that probiotics influence gastrointestinal motility. However, the molecular mechanisms by which probiotic Lactobacillus modulates intestinal motility in traumatic brain injury (TBI) mouse model have not been explored. In the present study, we provided evidence showing that treatment of TBI mice with Lactobacillus acidophilus significantly improved the terminal ileum villus morphology, restored the impaired interstitial cells of Cajal (ICC) and the disrupted ICC networks after TBI, and prevented TBI-mediated inhibition of contractile activity in intestinal smooth muscle. Mechanistically, the decreased concentration of MLCK, phospho-MLC20 and phospho-MYPT1 and increased concentration of MLCP and PKC were observed after TBI, and these events mediated by TBI were efficiently prevented by Lactobacillus acidophilus application. These findings may provide a novel mechanistic basis for the application of Lactobacillus acidophilus in the treatment of TBI.

  2. 一种估算静态MLC调强放疗治疗时间的方法%Estimate the Delivery Time of Static MLC-based IMRT

    Institute of Scientific and Technical Information of China (English)

    张彦新; 戴建荣; 李明辉; 张寅

    2011-01-01

    Objective: To analyze the influence factors of static MLC-based IMRT plans' delivery time and make a simulant formula to estimate it. Methods: Taking Varian 600CD as the object linac and Pinnacle3 (v8.0) as the treatment plan system, the delivery time of static MLC-based IMRT plan was divided into fourparts: beam-on time, MLC moving time, prepare time of original beams and prepare time of additional beams. If we got every part's linear function expression, we got the formula.Each beam's MLC moving time / beam-on time and the ending time could be got from treatment history. The other data of delivery time could be reckoned through these two data. In this study, 30 patients' treatment time data were used to get the coefficients of the formula. Results: The final formula was T = MU/DR+(NBs-NoB-NAB)×2.98+GA/5.78+(NoB-1)×1 7.58+NAB×26.95.The other 6 patients' plan parameters were used to validate this formula. The rates of the calculating values and the real values were 1.03, 0.92, 1.13, 0.99, 0.99, and 1.06. Conclusions: The main factors which influence delivery time of static MLC-based IMRT are beam numbers and segment beam numbers. Reducing beam and segment beam numbers can obvious reduce delivery time on the condition that dose distribution still conform to the clinic and physical criterion.%目的:本研究针对静态多叶准直器(MLC)调强放疗技术,分析影响治疗时间的各种因素,建立数学模型估算治疗时间,为临床评价计划执行效率提供一个工具.方法:以Varian600CD加速器为研究对象,计划采用Philips公司Pinnacle3(v8.0)计划系统设计.将静态MLC调强放疗的治疗时间T分为4个部分:射线照射时间TMU、MLC走位时间TMLC、原射野准备时间TpOB和分野准备时间TPAB.求出各部分的线性函数表达式,即可得到治疗时间的模拟公式.在VARIS治疗记录中可查到两项有关治疗时间的历史记录,一项是每个射野中所有子野的MLC走位和射线照射时长,另一

  3. 缺氧复氧后内皮细胞中PBEF与VEGF、p-MLC的相关性研究%Study on the Relationship between p-MLC and VEGF and PBEF in Endothelial Cells after Hypoxia

    Institute of Scientific and Technical Information of China (English)

    杨威; 董啸

    2015-01-01

    目的探讨前β细胞克隆增强因子(PBEF)、血管内皮生长因子(VEGF)和肌球蛋白轻链磷酸化(pMLC)在人脐静脉内皮细胞(HUVEC)缺氧复氧中的表达及相互间的相关性。方法体外常规培养HUVEC细胞,实验分为对照组、缺氧组和缺氧复氧组三组,每组10个培养板孔细胞;Western blot ing检测三组PBEF、VEGF和pMLC蛋白表达;并分析PBEF、VEGF和pMLC三组在HUVEC缺氧复氧中的相关性。结果 HUVEC细胞缺氧后,PBEF,VEGF和pMLC蛋白表达较对照组均显著升高(<0.01);缺氧组HUVEC细胞复氧12h后,PBEF,VEGF和pMLC蛋白表达较单纯缺氧组进一步升高,比较差异有统计学意义(<0.01)。 PBEF、VEGF和pMLC蛋白在HUVEC缺氧复氧中的表达均呈正相关;PBEF和VEGF间的等级相关系数为0.493,PBEF和pMLC间的等级相关系数为0.534,VEGF和pMLC间的等级相关系数为0.469。结论 PBEF、VEGF和pMLC参与HUVEC缺氧复氧过程,且三者在HUVEC缺氧复氧中的表达之间均呈正相关。%Objective To discuss the expression and relationship of pre-βcel colony-enhancing factor(PBEF),vessel endothelial growth factor(VEGF)and phosphorylation of myosin light chains(pMLC)in anoxia-reoxygenation of human umbilical vein endothelial cel (HUVEC).Methods HUVEC cel s were cultivated by the conventional method in vitro and divided into control,anoxia and anoxia-reoxygenation groups with 10 hole cel culture plate each.Expression of PBEF,VEGF and pMLC protein in every group were detected by western blot ing and analyzed the cor elation in anoxia-reoxygenation of HUVEC.Results Expression of PBEF,VEGF and pMLC protein were obviously higher than control group after HUVEC cel s of oxygen ( <0.01).Expression of PBEF,VEGF and pMLC protein increased more in HUVEC cel s of anoxia group after reoxygenation 12 h than anoxia group with statistical y significances ( <0.01).There are positive cor elations among expression of PBEF, VEGF and pMLC protein in HUVEC anoxia

  4. MiR-31 Regulates Rho-Associated Kinase-Myosin Light Chain (ROCK-MLC) Pathway and Inhibits Gastric Cancer Invasion: Roles of RhoA.

    Science.gov (United States)

    Chen, Zhuo; Liu, Shengnan; Xia, Yuan; Wu, Kejian

    2016-12-01

    BACKGROUND This study evaluated how the expression of miR-31 can be used to detect gastric cancer (GC) to help illuminate the role of miR-31 and RhoA in GC cells. MATERIAL AND METHODS We carried out our experiments using tissue specimens from 70 GC patients. The relative expression of miR-31 and RhoA mRNA in tissues and cells was detected by RT-PCR. The expression level of RhoA protein was detected by immunohistochemistry. GC cell line BGC-823 was transfected with six groups of vectors: blank group, NC (negative control) group, miR-31 mimics group, miR-31 mimics + RhoA group, miR-31 mimics + ROCK group, and miR-31 mimics + MLCK agonist group. AGS cells were also transfected with six groups of vectors: blank group, NC group, miR-31 inhibitor group, miR-31 inhibitor + RhoA siRNA group, miR-31 inhibitor + ROCK siRNA group, and miR-31 inhibitor + MLCK inhibitor group. Transwell assay was performed to detect the invasion and migration of cells. The protein expression in different transfected groups was detected using Western blotting. RESULTS GC tissues exhibited significantly lower levels of miR-31 expression compared to pericarcinous tissues (p<0.01). Moreover, a significantly higher expression of RhoA in GC tissues was observed (p<0.05). MiR-31 inhibited RhoA expression by binding to 3'UTR of mRNA, whereas miR-31 mimics significantly decreased the number of invaded and migrated cells (p<0.05). The activation of RhoA, ROCK, and phosphorylation of MLC remarkably exacerbate the invasion and migration ability of GC cells (p<0.05). CONCLUSIONS We found miR-31 could downregulate the ROCK/MLC pathway by inhibiting the expression of RhoA in order to suppress the invasion and migration of GC cells.

  5. Modulation of Muscle Atrophy, Fatigue and MLC Phosphorylation by MuRF1 as Indicated by Hindlimb Suspension Studies on MuRF1-KO Mice

    Directory of Open Access Journals (Sweden)

    Siegfried Labeit

    2010-01-01

    Full Text Available MuRF1 is a member of the TRIM/RBCC superfamily, a gene family that encompasses a large variety of proteins, all sharing the conserved TRIM (Tripartite Motive sequential array of RING, B-box, and coiled-coil domains. Within this family, MuRF1(also named TRIM63 is a specialized member that contributes to the development of muscle atrophy and sarcopenia. Here we studied MuRF1's role in muscle atrophy during muscle unloading induced by hindlimb suspension. Consistent with previous studies, we found that MuRF1 inactivation leads to an attenuated muscle atrophy response. The amount of protection was higher as compared to the denervation model, and within the 10 day-suspension period the soleus muscle was spared from atrophy in MuRF1-KO mice. Contractility studies on hindlimb suspended muscle tissues suggested that MuRF1's functions extend beyond muscle trophicity and implicate MuRF1 in muscle fatigue and MLC phosphorylation control: soleus muscle from MuRF1-KO mice fatigued significantly faster and in addition showed a reduced posttetanic twitch potentiation. Thus the present work further established the role of MuRF1 in muscle atrophy and for the first time shows that MuRF1 plays a role in muscle fatigue and twitch potentiation.

  6. Interactions of allogeneic human mononuclear cells in the two-way mixed leucocyte culture (MLC): influence of cell numbers, subpopulations and cyclosporin

    Science.gov (United States)

    Sato, T; Deiwick, A; Raddatz, G; Koyama, K; Schlitt, H J

    1999-01-01

    With organ allografts considerable numbers of donor-type mononuclear cells are transferred to the recipient, leading to bilateral immunological interactions between donor and recipient lymphocytes. To study such bilateral immune reactions in detail, human two-way MLC were performed. In this model proliferation kinetics, patterns of activation, and survival of the two populations were analysed, and the relevance of initial cell subset composition, relative cell numbers, and the effect of immunosuppression on this co-culture were evaluated. It could be demonstrated that with an initial 50:50 ratio of two populations of allogeneic cells one population dominated after 21 days of co-culture in 78 out of 80 combinations (97%) tested; the other population decreased markedly after an initially stable phase of 6–7 days. With unequal starting conditions the larger population dominated when resting cells were used, but small populations of preactivated cells or separated CD8+ cells could also dominate. Depletion of CD16+ natural killer (NK) cells and of CD2− cells (B cell and monocytes) had no effect on domination. Addition of cyclosporin delayed or blocked the domination process while addition of IL-2 accelerated it. Disappearance of one population was associated with detection of apoptotic cells. The findings indicate that co-cultures of allogeneic mononuclear cells are generally not stable for more than 1 week, but lead to active elimination of one population. CD8+ cells and particularly preactivated cells seem to play the most important role in that process, while NK cells are of less importance. Cyclosporin can prolong survival of allogeneic cells in co-culture. These observations suggest that under the conditions of clinical organ transplantation even small amounts of immunocompetent donor cells transferred by the graft may persist for some time and may, thereby, have the chance to exert immunomodulatory functions. PMID:9933457

  7. The Dose Influence of IMRT to Systematic MLC Leaf Bank Offsets%多叶准直器叶片到位偏差对调强放射治疗剂量的影响

    Institute of Scientific and Technical Information of China (English)

    王矫健; 徐利明; 全红; 李长虎; 阮长利

    2013-01-01

    Objective:The accuracy of multi-leaf collimate has taken a great influence to the IMRT (Intensity-modulated radiation therapy).By modifying the MLC files of patient's plans,set the MLC offset artificially to learn the influence of the dose distribution,so that can verify the necessity of the MLC QA.Methods:We select 13 patient's IMRT plan randomly,7 of the IMRT beams are delivered using MLC files containing systematic offset(+0.3 mm,+0.6 mm,+1 mm,representing the contracting of the MLC,we made it group A)in two banks,and the others containing offset(-0.3 mm,-0.6 mm,-1 mm,representing the expansion of the MLC,we made it group B)in two banks.The files are transmitted to eclipses8.0.Then beams are measured using MAPCHECK,comparing with the calculated fields without offset.Using commonly adopted criteria including absolute dose difference,relative dose difference,distance to agreement,and the gamma index.Results:Both group A and B takes little difference when the criterion based on the relative dose measurements.When using the criterion based on the absolute dose measurements.the passing points have a significantly reduction.Conclusions:When the mlc offset within 0.3mm can be acceptable in IMRT.Comparing with criteria of the relative dose difference,absolute dose difference is more significant.%目的:通过修改病人计划MLC文件,人为的设置MLC偏移距离,来了解MLC到位偏差对于剂量学的影响.方法:随机筛选13个病人的调强计划,提取计划MLC文件进行修改,使MLC叶片在运动方向上相对于原叶片文件位置分别有1mm和0.6mm以及0.3 mm的偏移.将其中7位患者计划叶片文件位置设置为两侧叶片分别在张开方向上有1mm、0.6 mm、以及0.3mm的位移相对于原叶片文件位置,记为A组,另外6位患者叶片文件对于原叶片文件两侧叶片分别在闭合方向上有lmm、0.6 mm、0.3 mm的位移,记为B组.将修改过后的MLC文件重新导入到Varian Eclipse计划系统,通过二维半

  8. Small fields output factors measurements and correction factors determination for several detectors for a CyberKnife{sup Registered-Sign} and linear accelerators equipped with microMLC and circular cones

    Energy Technology Data Exchange (ETDEWEB)

    Bassinet, C.; Huet, C.; Derreumaux, S.; Baumann, M.; Trompier, F.; Roch, P.; Clairand, I. [Institut de Radioprotection et de Surete Nucleaire (IRSN), BP17, 92262 Fontenay-aux-Roses Cedex (France); Brunet, G.; Gaudaire-Josset, S. [Institut de Cancerologie de l' Ouest Rene Gauducheau, bd Jacques Monod, 44805 Saint Herblain Cedex (France); Chea, M.; Boisserie, G. [Groupe Hospitalier Pitie-Salpetriere, 47/83 bd de l' Hopital, 75651 Paris Cedex 13 (France); Lacornerie, T. [Centre Oscar Lambret, 3, rue Frederic Combemale, BP 307, 59020 Lille Cedex (France)

    2013-07-15

    Purpose: The use of small photon fields is now an established practice in stereotactic radiosurgery and radiotherapy. However, due to a lack of lateral electron equilibrium and high dose gradients, it is difficult to accurately measure the dosimetric quantities required for the commissioning of such systems. Moreover, there is still no metrological dosimetric reference for this kind of beam today. In this context, the first objective of this work was to determine and to compare small fields output factors (OF) measured with different types of active detectors and passive dosimeters for three types of facilities: a CyberKnife{sup Registered-Sign} system, a dedicated medical linear accelerator (Novalis) equipped with m3 microMLC and circular cones, and an adaptive medical linear accelerator (Clinac 2100) equipped with an additional m3 microMLC. The second one was to determine the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors introduced in a recently proposed small field dosimetry formalism for different active detectors.Methods: Small field sizes were defined either by microMLC down to 6 Multiplication-Sign 6 mm{sup 2} or by circular cones down to 4 mm in diameter. OF measurements were performed with several commercially available active detectors dedicated to measurements in small fields (high resolution diodes: IBA SFD, Sun Nuclear EDGE, PTW 60016, PTW 60017; ionizing chambers: PTW 31014 PinPoint chamber, PTW 31018 microLion liquid chamber, and PTW 60003 natural diamond). Two types of passive dosimeters were used: LiF microcubes and EBT2 radiochromic films.Results: Significant differences between the results obtained by several dosimetric systems were observed, particularly for the smallest field size for which the difference in the measured OF reaches more than 20%. For passive dosimeters, an excellent agreement was observed (better than 2%) between EBT2 and LiF microcubes

  9. Role of cyclic nucleotide-dependent actin cytoskeletal dynamics:Ca(2+](i and force suppression in forskolin-pretreated porcine coronary arteries.

    Directory of Open Access Journals (Sweden)

    Kyle M Hocking

    Full Text Available Initiation of force generation during vascular smooth muscle contraction involves a rise in intracellular calcium ([Ca(2+]i and phosphorylation of myosin light chains (MLC. However, reversal of these two processes alone does not account for the force inhibition that occurs during relaxation or inhibition of contraction, implicating that other mechanisms, such as actin cytoskeletal rearrangement, play a role in the suppression of force. In this study, we hypothesize that forskolin-induced force suppression is dependent upon changes in actin cytoskeletal dynamics. To focus on the actin cytoskeletal changes, a physiological model was developed in which forskolin treatment of intact porcine coronary arteries (PCA prior to treatment with a contractile agonist resulted in complete suppression of force. Pretreatment of PCA with forskolin suppressed histamine-induced force generation but did not abolish [Ca(2+]i rise or MLC phosphorylation. Additionally, forskolin pretreatment reduced filamentous actin in histamine-treated tissues, and prevented histamine-induced changes in the phosphorylation of the actin-regulatory proteins HSP20, VASP, cofilin, and paxillin. Taken together, these results suggest that forskolin-induced complete force suppression is dependent upon the actin cytoskeletal regulation initiated by the phosphorylation changes of the actin regulatory proteins and not on the MLC dephosphorylation. This model of complete force suppression can be employed to further elucidate the mechanisms responsible for smooth muscle tone, and may offer cues to pathological situations, such as hypertension and vasospasm.

  10. SU-E-T-545: A MLC-Equipped Robotic Radiosurgery-Radiotherapy Combined System in Treating Hepatic Lesions: Delivery Efficiency as Compared to a Standard Linac for Treating Hepatic Lesions

    Energy Technology Data Exchange (ETDEWEB)

    Jin, L; Price, R; Wang, L; Meyer, J; Ma, C [Fox Chase Cancer Center, Philadephia, PA (United States); Fan, J [Virtua Fox Chase Cancer Center, Philadelphia, PA (United States)

    2014-06-01

    Purpose: The CyberKnife (CK) M6 Series introduced a mulitleaf collimator (MLC) beam for extending its capability to the conventional radiotherapy. This work is to investigate delivery efficiency of this system as compared to a standard Varian linac when treating hepatic lesions. Methods: Nine previously treated patients were divided into three groups with three patients in each. Group one: fractionated radiotherapy; Group two: SBRT-like treatments and Group three: fractionated radiotherapy targeting two PTVs. The clinically used plans were generated with the Eclipse treatment planning system (TPS). We re-planned these cases using a Mulitplan (MP) TPS for the CK M6 and normalized to the same PTV dose coverage. CK factors (CF) (defined as modulation scaling factor in this work), number of nodes (NN), number of MLC segments (NS) and beam delivery time (BT) with an estimated image interval of 60 seconds, were used for evaluation of delivery efficiency. Results: Generated plans from the MP and Eclipse TPS demonstrated the similar quality in terms of PTV confomality index, minimum and maximum PTV doses, and doses received by critical structures. Group one: CF ranged from 8.1 to 8.7, NN from 30 to 40, NS from 120 to 155 and BT from 20 to 23 minutes; group two: CF from 4.7 to 8.5, NN from 15 to 19, NS from 82 to 141 and BT from 18 to 24 minutes; and group three: CF from 7.9 to 10, NN from 47 to 49, NS from 110 to 113 and BT from 20 to 22 minutes. Conclusions: Delivery time is longer for the CK M6 than for the Varian linac (7.8 to 13.7 minutes). Further investigation will be necessary to determine if a PTV reduction from the tracking feature will shorten the delivery time without decreasing plan quality.

  11. Monte Carlo simulated corrections for beam commissioning measurements with circular and MLC shaped fields on the CyberKnife M6 System: a study including diode, microchamber, point scintillator, and synthetic microdiamond detectors

    Science.gov (United States)

    Francescon, P.; Kilby, W.; Noll, J. M.; Masi, L.; Satariano, N.; Russo, S.

    2017-02-01

    Monte Carlo simulation was used to calculate correction factors for output factor (OF), percentage depth-dose (PDD), and off-axis ratio (OAR) measurements with the CyberKnife M6 System. These include the first such data for the InCise MLC. Simulated detectors include diodes, air-filled microchambers, a synthetic microdiamond detector, and point scintillator. Individual perturbation factors were also evaluated. OF corrections show similar trends to previous studies. With a 5 mm fixed collimator the diode correction to convert a measured OF to the corresponding point dose ratio varies between  -6.1% and  -3.5% for the diode models evaluated, while in a 7.6 mm  ×  7.7 mm MLC field these are  -4.5% to  -1.8%. The corresponding microchamber corrections are  +9.9% to  +10.7% and  +3.5% to  +4.0%. The microdiamond corrections have a maximum of  -1.4% for the 7.5 mm and 10 mm collimators. The scintillator corrections are  15%, reducing to    d max were  stopping power perturbations. The microdiamond OAR corrections were  <3% outside the beam. This paper provides OF corrections that can be used for commissioning new CyberKnife M6 Systems and retrospectively checking estimated corrections used previously. We recommend the PDD and OAR corrections are used to guide detector selection and inform the evaluation of results rather than to explicitly correct measurements.

  12. 容积调强旋转放疗的计划验证通过率对多叶准直器位置误差的灵敏度%The sensitivity of patient-specific VMAT QA to MLC positioning errors

    Institute of Scientific and Technical Information of China (English)

    王清鑫; 戴建荣; 张可; 杨昕

    2013-01-01

    Objective To evaluate the sensitivity of patient-specific volumetric-modulated arc therapy (VMAT) quality assurance (QA) to minor multileaf collimator (M LC) positioning errors.Methods Systematic multileaf collimator (MLC) positioning errors (+0.5 mm,+ 1 mm and +2 mm) were introduced into the clinical VMAT patient plans with 2 types of MLC positioning errors:systematic MLC gap width errors and systematic MLC shift errors for 6 cases,including 3 cases with prostatic cancer and 3 cases with nasopharyngeal cancer.The planar dose distributions of the original and modified plans were measured using ArcCheck array.The coincidence between the measured results and the calculated results was evaluated using both absolute distance-to-agreement (AD-DTA) analysis with 3%/3 mm and 2%/2 mm criteria.Results The average passing rate of the 6 original VMAT plans was 96.0% with the ADDTA criteria of 3%/3 mm which was commonly adopted in clinical practice.For the MLC gap width errors of + 1 mm,+2 mm,and-2 mm and the MLC shift errors of 2 mm,the drop levels in average passing rate with the AD-DTA criteria of 3%/3 mm were 8.8%,15.5%,6.1% and 7.9%,respectively.The + 2 mm MLC positioning errors and + 1 mm MLC gap width errors could be detected by the patient-specific VMAT QA procedure.The AD-DTA criteria of 2%/2 mm was more sensitive compared with the criteria of 3%/3 mm.Conclusions Patient-specific VMAT QA is not sensitive enough to detect the systematic MLC positioning errors within 1 mm.Additional MLC QA is needed to guarantee the accuracy of VMAT delivery.%目的 针对容积调强旋转放疗技术(VMAT),分析患者计划验证通过率对多叶准直器(MLC)位置误差的灵敏度.方法 选取6例双弧VMAT计划,引入MLC位置误差(±0.5 mm、±1 mm和±2 mm),模拟VMAT执行过程中MLC可能出现的系统误差,包括MLC射野宽度误差和MLC整体偏向一侧的误差.每个病例有10个计划,1个原计划和9个带有误差的新计划.利用

  13. A feasibility study of Dynamic Phantom scanner for quality assurance of photon beam profiles at various gantry angles.

    Science.gov (United States)

    Zhang, Yunkai; Hsi, Wen C; Chu, James C H; Bernard, Damian B; Abrams, Ross A

    2005-01-01

    The effect of gantry rotation on beam profiles of photon and electron beams is an important issue in quality assurance for radiotherapy. To address variations in the profiles of photon and electron beams at different gantry angles, a Dynamic Phantom scanner composed of a 20 x 12 x 6 cm3 scanning Lucite block was designed as a cross-beam-profile scanner. To our knowledge, differences between scanned profiles acquired at different gantry angles with a small size Lucite block and those acquired a full-size (60 x 60 x 50 cm3) water phantom have not been previously investigated. We therefore performed a feasibility study for a first prototype Dynamic Phantom scanner without a gantry attachment mount. Radiation beams from a Varian LINAC 21EX and 2100C were used. Photon beams (6 MV and 18 MV) were shaped by either collimator jaws or a Varian 120 Multileaf (MLC) collimator, and electron beams (6 MeV, 12 MeV, and 20 MeV) were shaped by a treatment cone. To investigate the effect on profiles by using a Lucite block, a quantitative comparison of scanned profiles with the Dynamic Phantom and a full-size water phantom was first performed at a 0 degrees gantry angle for both photon and electron beams. For photon beam profiles defined by jaws at 1.0 cm and 5.0 cm depths of Lucite (i.e., at 1.1 cm and 5.7 cm depth of water), a good agreement (less than 1% variation) inside the field edge was observed between profiles scanned with the Dynamic Phantom and with a water phantom. The use of Lucite in the Dynamic Phantom resulted in reduced penumbra width (about 0.5 mm out of 5 mm to 8mm) and reduced (1% to 2%) scatter dose beyond the field edges for both 6 MV and 18 MV beams, compared with the water phantom scanner. For profiles of the MLC-shaped 6 MV photon beam, a similar agreement was observed. For profiles of electron beams scanned at 2.9 cm depth of Lucite (i.e., at 3.3 cm depth of water), larger disagreements in profiles (3% to 4%) and penumbra width (3 mm to 4 mm out of 12 mm

  14. SU-E-T-444: Gravity Effect On Maximum Leaf Speed in Dynamic IMRT Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Olasolo, J; Pellejero, S; Gracia, M; Gallardo, N; Martin, ML; Lozares, S; Maneru, F; Bragado, L; Miquelez, S [Complejo Hospitalario de Navarra, Pamplona (Spain); Artacho, JM [Universidad de Zaragoza, Zaragoza (Spain)

    2015-06-15

    Purpose: A leaf sequencing algorithm has been recently developed in our department. Our purpose is to utilize this algorithm to reduce treatment time by studying the feasibility of using several maximum leaf speeds depending on gantry angle and leaf thickness (0.5 or 1 cm at isocenter). To do so, the gravity effect on MLC performance has been examined by means of analysing the dynalog files. Methods: Leaf position errors has been ascertained according to gantry angle and leaf speed in MLC Millenium120 (Varian). In order to do this, the following test has been designed: all leaves move in synchrony, with same speed and 1 cm gap between opposite leaves. This test is implemented for 18 different speeds: 0.25-0.5-0.75-1-1.25-1.5-1.75-2-2.1-2.2-2.3-2.4-2.5-2.6-2.7-2.8-2.9-3.0 cm/s and 8 gantry angles: 0-45-90-135-180-225-270-315. Collimator angle is 2 degrees in all cases since it is the most usual one in IMRT treatments in our department. Dynamic tolerance is 2 mm. Dynalogs files of 10 repetitions of the test are analysed with a Mathlab in-house developed software and RMS error and 95th percentiles are calculated. Varian recommends 2.5 cm/s as the maximum leaf speed for its segmentation algorithm. In our case, we accept this speed in the most restrictive situation: gantry angle 270 and 1 cm leaf thickness. Maximum speeds for the rest of the cases are calculated by keeping the difference between 95th percentile and dynamic tolerance. In this way, beam hold-off probability does not increase. Results: Maximum speeds every 45 degrees of gantry rotation have been calculated for both leaf thickness. These results are 2.9-2.9-2.9-2.9-2.7-2.6-2.6-2.7 cm/s for 0.5 cm leaf thickness and 2.7-2.7-2.7-2.7-2.6-2.5-2.5-2.6 cm/s for 1 cm leaf thickness. Conclusion: Gravity effect on MLC positioning has been studied. Maximum leaf speed according to leaf thickness and gantry angle have been calculated which reduces treatment time.

  15. Crop Type Mapping from a Sequence of Terrasar-X Images with Dynamic Conditional Random Fields

    Science.gov (United States)

    Kenduiywo, B. K.; Bargiel, D.; Soergel, U.

    2016-06-01

    Crop phenology is dynamic as it changes with times of the year. Such biophysical processes also look spectrally different to remote sensing satellites. Some crops may depict similar spectral properties if their phenology coincide, but differ later when their phenology diverge. Thus, conventional approaches that select only images from phenological stages where crops are distinguishable for classification, have low discrimination. In contrast, stacking images within a cropping season limits discrimination to a single feature space that can suffer from overlapping classes. Since crop backscatter varies with time, it can aid discrimination. Therefore, our main objective is to develop a crop sequence classification method using multitemporal TerraSAR-X images. We adopt first order markov assumption in undirected temporal graph sequence. This property is exploited to implement Dynamic Conditional Random Fields (DCRFs). Our DCRFs model has a repeated structure of temporally connected Conditional Random Fields (CRFs). Each node in the sequence is connected to its predecessor via conditional probability matrix. The matrix is computed using posterior class probabilities from association potential. This way, there is a mutual temporal exchange of phenological information observed in TerraSAR-X images. When compared to independent epoch classification, the designed DCRF model improved crop discrimination at each epoch in the sequence. However, government, insurers, agricultural market traders and other stakeholders are interested in the quantity of a certain crop in a season. Therefore, we further develop a DCRF ensemble classifier. The ensemble produces an optimal crop map by maximizing over posterior class probabilities selected from the sequence based on maximum F1-score and weighted by correctness. Our ensemble technique is compared to standard approach of stacking all images as bands for classification using Maximum Likelihood Classifier (MLC) and standard CRFs. It

  16. Validation of quality control tests of a multi leaf collimator using electronic portal image devices and commercial software; Validacion de unas pruebas de control de calidad del colimador multilamina utilizando dispositivos electronicos de imagen portal y una aplicacion comercial

    Energy Technology Data Exchange (ETDEWEB)

    Latorre-Musoll, A.; Jornet Sala, N.; Carrasco de Fez, P.; Edualdo Puell, T.; Ruiz Martinez, A.; Ribas Morales, M.

    2013-07-01

    We describe a daily quality control procedure of the multi leaf collimator (MLC) based on electronic portal image devices and commercial software. We designed tests that compare portal images of a set of static and dynamic MLC configurations to a set of reference images using commercial portal dosimetry software. Reference images were acquired using the same set of MLC configurations after the calibration of the MLC. To assess the sensitivity to detect MLC under performances, we modified the MLC configurations by inserting a range of leaf position and speed errors. Distance measurements on portal images correlated with leaf position errors down to 0.1 mm in static MLC configurations. Dose differences between portal images correlated both with speed errors down to 0.5% of the nominal leaf velocities and with leaf position errors down to 0.1 mm in dynamic MLC configurations. The proposed quality control procedure can assess static and dynamic MLC configurations with high sensitivity and reliability. (Author)

  17. Development of dual-layer GSO depth-of-interaction block detector using angled optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Okumura, Satoshi, E-mail: okumura.satoshi@c.mbox.nagoya-u.ac.jp [Nagoya University Graduate School of Medicine (Japan); Yamamoto, Seiichi [Nagoya University Graduate School of Medicine (Japan); Watabe, Hiroshi [Cyclotron and Radioisotope Center (CYRIC), Tohoku University (Japan); Kato, Natsuki; Hamamura, Huka [Nagoya University Graduate School of Medicine (Japan)

    2015-05-01

    A PET system for small animals requires a small detector ring to obtain high-spatial resolution images. However, when we use a relatively large size of photodetector such as a position-sensitive photomultiplier tube (PSPMT), the detector ring is arranged in a hexagonal- or octagonal-shape, and the PET system has large gaps between the block detectors. The large gaps produce image distortion, and the reconstruction algorithm is difficult. To solve these problems, we proposed to arrange two scintillator blocks on one PSPMT using two angled optical fiber-based image guides. We could set two scintillator blocks angled at 22.5° on a PSPMT so that these scintillator blocks are arranged in a nearly circular (hexadecagonal) shape with eight developed block detectors. We used Gd{sub 2}SiO{sub 5} (GSO) scintillators with Ce concentrations of 1.5 mol% (decay time: 39 ns) and 0.4 mol% (decay time: 63 ns). Sizes of these GSO cells were 1.6×2.4×7.0 mm{sup 3} and 1.6×2.4×8.0 mm{sup 3} for 1.5 mol% Ce and 0.4 mol% Ce, respectively. These two types of GSO were arranged in an 11×15 matrix and optically coupled in the depth direction to form a depth-of-interaction (DOI) detector. Two GSO blocks and two optical fiber-based image guides were optically coupled to a 2-in. PSPMT (Hamamatsu Photonics H8500: 8×8 anodes). We measured the performances of the block detector with Cs-137 gamma photons (662-keV). We could resolve almost all pixels clearly in a two-dimensional position histogram. The average peak-to-valley ratios (P/Vs) of the two-dimensional position histogram along profiles were 2.6 and 4.8 in horizontal and vertical directions, respectively. The energy resolution was 28.4% full-width at half-maximum (FWHM). The pulse shape spectra showed good separation with a P/V of 5.2. The developed block detector performed well and shows promise for the development of high-sensitivity and high-spatial resolution PET systems.

  18. Non-blind acoustic invisibility by dual layers of homogeneous single-negative media

    Science.gov (United States)

    Gao, He; Zhu, Yi-Fan; Fan, Xu-Dong; Liang, Bin; Yang, Jing; Cheng, Jian-Chun

    2017-02-01

    Non-blind invisibility cloaks allowing the concealed object to sense the outside world have great application potentials such as in high-precision sensing or underwater camouflage. However the existing designs based on coordinate transformation techniques need complicated spatially-varying negative index or intricate multi-layered configurations, substantially increasing the difficulty in practical realization. Here we report on the non-blind acoustic invisibility for a circular object in free space with simple distribution of cloak parameters. The mechanism is that, instead of utilizing the transformation acoustics technique, we develop the analytical formulae for fast prediction of the scattering from the object and then use an evolutionary optimization to retrieve the desired cloak parameters for minimizing the scattered field. In this way, it is proven possible to break through the fundamental limit of complementary condition that must be satisfied by the effective parameters of the components in transformation acoustics-based cloaks. Numerical results show that the resulting cloak produces a non-bflind invisibility as perfect as in previous designs, but only needs two layers with homogenous single-negative parameters. With full simplification in parameter distribution and broken symmetry in complementary relationship, our scheme opens new route to free-space non-blind invisibility, taking a significant step towards real-world application of cloaking devices.

  19. A Technique for Producing Large Dual-Layer Pellets in Support of Disruption Mitigation Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Combs, Stephen Kirk [ORNL; Leachman, J. W. [Washington State University; Meitner, Steven J [ORNL; Baylor, Larry R [ORNL; Foust, Charles R [ORNL; Commaux, Nicolas JC [ORNL; Jernigan, Thomas C [ORNL

    2011-01-01

    A special single-shot pellet injection system that produces and accelerates large cryogenic pellets (~16 mm diameter and composed of D2 or Ne) to relatively high speeds (>300 and 600 m/s, respectively) was previously developed at the Oak Ridge National Laboratory. Subsequently, a similar system was installed on DIII-D and used successfully in disruption mitigation experiments. To circumvent some operational issues with injecting the large Ne pellets, a technique has been developed in which a relatively thin layer (0.1 to 1.0 mm) of D2 is frozen on the inner wall of the pipe-gun barrel, followed by filling the core with solid Ne. The technique and the initial laboratory tests are described, as well as the implementation and operational issues for fusion experiments.

  20. Chromatographic behaviour of single cells in a microchannel with dynamic geometry.

    Science.gov (United States)

    Gerhardt, Thomas; Woo, Sangpil; Ma, Hongshen

    2011-08-21

    We present the design of a microchannel with dynamic geometry that imparts different flow rates to different cells based on their physical properties. This dynamic microchannel is formed between a textured surface and a flexible membrane. As cells flow through the microchannel, the height of the channel oscillates causing periodic entrapment of the larger cells, and as a result, attenuating their velocity relative to the bulk liquid. The smaller cells are not slowed by the moving microstructure, and move synchronously with the bulk liquid. The ability of the dynamic microchannel to selectively attenuate the flow rate of eukaryotic cells is similar to a size-exclusion chromatography column, but with the opposite behavior. The speed of smaller substances is attenuated relative to the larger substances in traditional size-exclusion chromatography columns, whereas the speed of the larger substances that is attenuated in the dynamic microchannel. We verified this property by tracking the flow of single cells through the dynamic microchannel. L1210 mouse lymphoma cells (MLCs), peripheral blood mononuclear cells (PBMCs), and red blood cells (RBCs) were used as model cells. We showed that the flow rate of MLC is slowed by more than 50% compared to PBMCs and RBCs. We characterized the operation of the microchannel by measuring the velocity of each of the three cell types as a function of the pressures used to oscillate the membrane position, as well as the duty cycle of the oscillation.

  1. Modelling and Simulation of Fuel Cell Dynamics for Electrical Energy Usage of Hercules Airplanes

    Directory of Open Access Journals (Sweden)

    Hamid Radmanesh

    2014-01-01

    Full Text Available Dynamics of proton exchange membrane fuel cells (PEMFC with hydrogen storage system for generating part of Hercules airplanes electrical energy is presented. Feasibility of using fuel cell (FC for this airplane is evaluated by means of simulations. Temperature change and dual layer capacity effect are considered in all simulations. Using a three-level 3-phase inverter, FC’s output voltage is connected to the essential bus of the airplane. Moreover, it is possible to connect FC’s output voltage to airplane DC bus alternatively. PID controller is presented to control flow of hydrogen and oxygen to FC and improve transient and steady state responses of the output voltage to load disturbances. FC’s output voltage is regulated via an ultracapacitor. Simulations are carried out via MATLAB/SIMULINK and results show that the load tracking and output voltage regulation are acceptable. The proposed system utilizes an electrolyser to generate hydrogen and a tank for storage. Therefore, there is no need for batteries. Moreover, the generated oxygen could be used in other applications in airplane.

  2. Modelling and simulation of fuel cell dynamics for electrical energy usage of Hercules airplanes.

    Science.gov (United States)

    Radmanesh, Hamid; Heidari Yazdi, Seyed Saeid; Gharehpetian, G B; Fathi, S H

    2014-01-01

    Dynamics of proton exchange membrane fuel cells (PEMFC) with hydrogen storage system for generating part of Hercules airplanes electrical energy is presented. Feasibility of using fuel cell (FC) for this airplane is evaluated by means of simulations. Temperature change and dual layer capacity effect are considered in all simulations. Using a three-level 3-phase inverter, FC's output voltage is connected to the essential bus of the airplane. Moreover, it is possible to connect FC's output voltage to airplane DC bus alternatively. PID controller is presented to control flow of hydrogen and oxygen to FC and improve transient and steady state responses of the output voltage to load disturbances. FC's output voltage is regulated via an ultracapacitor. Simulations are carried out via MATLAB/SIMULINK and results show that the load tracking and output voltage regulation are acceptable. The proposed system utilizes an electrolyser to generate hydrogen and a tank for storage. Therefore, there is no need for batteries. Moreover, the generated oxygen could be used in other applications in airplane.

  3. Dynamic Logics of Dynamical Systems

    CERN Document Server

    Platzer, André

    2012-01-01

    We survey dynamic logics for specifying and verifying properties of dynamical systems, including hybrid systems, distributed hybrid systems, and stochastic hybrid systems. A dynamic logic is a first-order modal logic with a pair of parametrized modal operators for each dynamical system to express necessary or possible properties of their transition behavior. Due to their full basis of first-order modal logic operators, dynamic logics can express a rich variety of system properties, including safety, controllability, reactivity, liveness, and quantified parametrized properties, even about relations between multiple dynamical systems. In this survey, we focus on some of the representatives of the family of differential dynamic logics, which share the ability to express properties of dynamical systems having continuous dynamics described by various forms of differential equations. We explain the dynamical system models, dynamic logics of dynamical systems, their semantics, their axiomatizations, and proof calcul...

  4. Dynamical Languages

    Science.gov (United States)

    Xie, Huimin

    The following sections are included: * Definition of Dynamical Languages * Distinct Excluded Blocks * Definition and Properties * L and L″ in Chomsky Hierarchy * A Natural Equivalence Relation * Symbolic Flows * Symbolic Flows and Dynamical Languages * Subshifts of Finite Type * Sofic Systems * Graphs and Dynamical Languages * Graphs and Shannon-Graphs * Transitive Languages * Topological Entropy

  5. Megavoltage Image-Based Dynamic Multileaf Collimator Tracking of a NiTi Stent in Porcine Lungs on a Linear Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, Per R., E-mail: perpolse@rm.dk [Department of Oncology, Aarhus University Hospital, Aarhus (Denmark); Carl, Jesper; Nielsen, Jane; Nielsen, Martin S.; Thomsen, Jakob B. [Department of Medical Physics, Aalborg Hospital, University of Aarhus, Aalborg (Denmark); Jensen, Henrik K. [Department of Pulmonary Medicine, Aalborg Hospital, University of Aarhus, Aalborg (Denmark); Kjaergaard, Benedict; Zepernick, Peter R. [Department of Thoracic Surgery, Aalborg Hospital, University of Aarhus, Aalborg (Denmark); Worm, Esben; Fledelius, Walther [Department of Oncology, Aarhus University Hospital, Aarhus (Denmark); Cho, Byungchul [Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Sawant, Amit [University of Texas Southwestern Medical Center, Dallas, TX (United States); Ruan, Dan [Department of Radiation Oncology, University of California-Los Angeles, Los Angeles, CA (United States); Keall, Paul J. [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Sydney Medical School, University of Sydney, Sydney, New South Wales (Australia)

    2012-02-01

    Purpose: To investigate the accuracy and potential limitations of MV image-based dynamic multileaf collimator (DMLC) tracking in a porcine model on a linear accelerator. Methods and Materials: A thermo-expandable NiTi stent designed for kilovoltage (kV) X-ray visualization of lung lesions was inserted into the bronchia of three anaesthetized Goettingen minipigs. A four-dimensional computed tomography scan was used for planning a five-field conformal treatment with circular multileaf collimator (MLC) apertures. A 22.5 Gy single fraction treatment was delivered to the pigs. The peak-to-peak stent motion was 3 to 8 mm, with breathing periods of 1.2 to 4 s. Before treatment, X-ray images were used for image-guided setup based on the stent. During treatment delivery, continuous megavoltage (MV) portal images were acquired at 7.5 Hz. The stent was segmented in the images and used for continuous adaptation of the MLC aperture. Offline, the tracking error in beam's eye view of the treatment beam was calculated for each MV image as the difference between the MLC aperture center and the segmented stent position. The standard deviations of the systematic error {Sigma} and the random error {sigma} were determined and compared with the would-be errors for a nontracking treatment with pretreatment image-guided setup. Results: Reliable stent segmentation was obtained for 11 of 15 fields. Segmentation failures occurred when image contrast was dominated by overlapping anatomical structures (ribs, diaphragm) rather than by the stent, which was designed for kV rather than MV X-ray visibility. For the 11 fields with reliable segmentation, {Sigma} was 0.5 mm/0.4 mm in the two imager directions, whereas {sigma} was 0.5 mm/1.1 mm. Without tracking, {Sigma} and {sigma} would have been 1.7 mm/1.4 mm and 0.8 mm/1.4 mm, respectively. Conclusion: For the first time, in vivo DMLC tracking has been demonstrated on a linear accelerator showing the potential for improved targeting accuracy

  6. TM图像杨树林识别的MLC与LSU算法应用分析——以河北省文安县为例%Image Recognition and Extraction of Poplar Plantation Based on MLC and LSU:Case of Wen-an County of Hebei Province

    Institute of Scientific and Technical Information of China (English)

    赵宇鸾; 李秀彬; 辛良杰; 张英

    2011-01-01

    China is actively implementing the fast-growing and high-yielding timber base construction program in the past few years. There is an increasing number of poplar woodland in the North China Plain over the past decade, and the North China Plain is one of the major grain-producing areas in China. So the expansion of poplar woodland may influence food security, which attracts more and more attention. The area of poplar woodland is a key to the attention. We used TM band 1, band 2, band 3, band 4, band 5,and band 7 of Landsat 5 as fundamental datum and preproeessed them, then produced a new data set of 13 bands by generating vegetation index and principal component analysis. At last, we chose band combination of visual interpretation by using optimum index factor (OIF) and extracted information of area ofpoplar woodland by using maximum likelihood classification (MLC) and linear spectral unmixing (LSU).The results showed that: (1) Visible red light, near-infrared, mid-infrared, canopy vegetation index, and the first three principal components were dominant to the information extraction. (2) The 13 bands were separated according to correlation coefficient of the bands and then OIF was computed, which can save work time. (3) The area of extracted pixels of poplar woodland by MLC was 11 259. 84ha, which accounted for 10. 95% of the research area. Through outdoor authentication, the precision of producer and user was 84. 07% and 93. 14%, respectively, the outcome of classification and mapping was good. (4) LSU is a sub-pixel technology. So the area of extracted pixels of poplar woodland by LSU was better than that by MLC in the area of surface fragmentation. The extracted area by LSU reached 11 259. 84ha, which increased largely in the research area. And it accounted for 13. 33% of the research area. In a word, the two ways complemented each other, which can supply a sample for the quickly investigation of poplar woodland and the research on land-use conflict

  7. Molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Ladd, A.J.C.

    1988-08-01

    The basic methodology of equilibrium molecular dynamics is described. Examples from the literature are used to illustrate how molecular dynamics has been used to resolve theoretical controversies, provide data to test theories, and occasionally to discover new phenomena. The emphasis is on the application of molecular dynamics to an understanding of the microscopic physics underlying the transport properties of simple fluids. 98 refs., 4 figs.

  8. Dynamics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Dynamics Lab replicates vibration environments for every Navy platform. Testing performed includes: Flight Clearance, Component Improvement, Qualification, Life...

  9. Dynamical systems

    CERN Document Server

    Sternberg, Shlomo

    2010-01-01

    Celebrated mathematician Shlomo Sternberg, a pioneer in the field of dynamical systems, created this modern one-semester introduction to the subject for his classes at Harvard University. Its wide-ranging treatment covers one-dimensional dynamics, differential equations, random walks, iterated function systems, symbolic dynamics, and Markov chains. Supplementary materials offer a variety of online components, including PowerPoint lecture slides for professors and MATLAB exercises.""Even though there are many dynamical systems books on the market, this book is bound to become a classic. The the

  10. Commissioning and quality assurance for intensity modulated radiotherapy with dynamic multileaf collimator: experience of the Pontificia Universidad Católica de Chile.

    Science.gov (United States)

    Venencia, Carlos Daniel; Besa, Pelayo

    2004-01-01

    The objective of this paper is to present our experience in the commissioning and quality assurance (QA) for intensity modulated radiotherapy (IMRT) using dynamic multileaf collimator (dMLC), sliding window technique. Using Varian equipment solution, the connectivity and operation between all IMRT chain components was checked. Then the following test were done: stability of leaf positioning and leaf speed, sensitivity to treatment interruptions (acceleration and deceleration), evaluation of standard field patterns, stability of dMLC output, segmental dose accuracy check, average leaf transmission, dosimetric leaf separation, effects of lateral disequilibrium between adjacent leaves in dose profiles and multiple carriage field verification. Standard patterns were generated for verification: uniform field, pyramid, hole, wedge, peaks and chair. Weekly QA Protocol include: sweeping gap output, Garden Fence Test (narrow bands, 2 mm wide, of exposure spaced at 2-cm intervals) and segmental dose accuracy check. Monthly QA include: sweeping gap output at multiple gantry and collimator angle, sweeping gap output off-axis, Picket Fence Test (eight consecutive movements of a 5-cm wide rectangular field spaced at 5-cm intervals), stability of leaf speed and leaf motor current test (PWM test). Patient QA procedure consists of an absolute dose measurement for all treatments fields in the treatment condition, analysis of actual leaf position versus planned leaf position (dynalog files) for each treatment field, film relative dose determination for each field, film relative dose determination for the plan (all treatment fields) in two axial planes and patient positioning verification with orthogonal films. The tests performed showed acceptable result. After more than one year of IMRT treatment the routine QA machine checks confirm the precision and stability of the IMRT system.

  11. TU-CD-304-04: Scanning Field Total Body Irradiation Using Dynamic Arc with Variable Dose Rate and Gantry Speed

    Energy Technology Data Exchange (ETDEWEB)

    Yi, B; Xu, H; Mutaf, Y; Prado, K [Univ. of Maryland School Of Medicine, Baltimore, MD (United States)

    2015-06-15

    Purpose: Enable a scanning field total body irradiation (TBI) technique, using dynamic arcs, which is biologically equivalent to a moving couch TBI. Methods: Patient is treated slightly above the floor and the treatment field scans across the patient by a moving gantry. MLC positions change during gantry motion to keep same field opening at the level of the treatment plane (170 cm). This is done to mimic the same geometry as the moving couch TBI technique which has been used in our institution for over 10 years. The dose rate and the gantry speed are determined considering a constant speed of the moving field, variations in SSD and slanted depths resulting from oblique gantry angles. An Eclipse (Varian) planning system is commissioned to accommodate the extended SSD. The dosimetric foundations of the technique have been thoroughly investigated using phantom measurements. Results: Dose uniformity better than 2% across 180 cm length at 10cm depth is achieved by moving the gantry from −55 to +55 deg. Treatment range can be extended by increasing gantry range. No device such as a gravity-oriented compensator is needed to achieve a uniform dose. It is feasible to modify the dose distribution by adjusting the dose rate at each gantry angle to compensate for body thickness differences. Total treatment time for 2 Gy AP/PA fields is 40–50 minutes excluding patient set up time, at the machine dose rate of 100 MU/min. Conclusion: This novel yet transportable moving field technique enables TBI treatment in a small treatment room with less program development preparation than other techniques. Treatment length can be extended per need, and. MLC-based thickness compensation and partial lung blocking are also possible.

  12. Molecular dynamics

    NARCIS (Netherlands)

    Bergstra, J.A.; Bethke, I.

    2002-01-01

    Molecular dynamics is a model for the structure and meaning of object based programming systems. In molecular dynamics the memory state of a system is modeled as a fluid consisting of a collection of molecules. Each molecule is a collection of atoms with bindings between them. A computation is model

  13. Dynamic Squares

    NARCIS (Netherlands)

    Blackburn, P.; Venema, Y.

    2008-01-01

    This paper examines various propositional logics in which the dynamic implication connective (discussed in Groenendijk and Stokhof's (1992) Dynamic Predicate Logic and Kamp's (1981) Discourse Representation Theory) plays the central role. Our approach is modal: the basic idea is to view as a binary

  14. Record dynamics

    DEFF Research Database (Denmark)

    Robe, Dominic M.; Boettcher, Stefan; Sibani, Paolo

    2016-01-01

    When quenched rapidly beyond their glass transition, colloidal suspensions fall out of equilibrium. The pace of their dynamics then slows down with the system age, i.e., with the time elapsed after the quench. This breaking of time translational invariance is associated with dynamical observables...

  15. Fluid Dynamics

    DEFF Research Database (Denmark)

    Brorsen, Michael

    These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University.......These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University....

  16. Persuasion dynamics

    Science.gov (United States)

    Weisbuch, Gérard; Deffuant, Guillaume; Amblard, Frédéric

    2005-08-01

    We here discuss a model of continuous opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. We concentrate on the version of the model in the presence of few extremists which might drive the dynamics to generalized extremism. A network version of the dynamics is presented here, and its results are compared to those previously obtained for the full-mixing case. The same dynamical regimes are observed, but in rather different parameter regions. We here show that the combination of meso-scale features resulting from the first interaction steps determines the asymptotic state of the dynamics.

  17. Dynamic Optimization

    Science.gov (United States)

    Laird, Philip

    1992-01-01

    We distinguish static and dynamic optimization of programs: whereas static optimization modifies a program before runtime and is based only on its syntactical structure, dynamic optimization is based on the statistical properties of the input source and examples of program execution. Explanation-based generalization is a commonly used dynamic optimization method, but its effectiveness as a speedup-learning method is limited, in part because it fails to separate the learning process from the program transformation process. This paper describes a dynamic optimization technique called a learn-optimize cycle that first uses a learning element to uncover predictable patterns in the program execution and then uses an optimization algorithm to map these patterns into beneficial transformations. The technique has been used successfully for dynamic optimization of pure Prolog.

  18. Dynamic triggering

    Science.gov (United States)

    Hill, David P.; Prejean, Stephanie; Schubert, Gerald

    2015-01-01

    Dynamic stresses propagating as seismic waves from large earthquakes trigger a spectrum of responses at global distances. In addition to locally triggered earthquakes in a variety of tectonic environments, dynamic stresses trigger tectonic (nonvolcanic) tremor in the brittle–plastic transition zone along major plate-boundary faults, activity changes in hydrothermal and volcanic systems, and, in hydrologic domains, changes in spring discharge, water well levels, soil liquefaction, and the eruption of mud volcanoes. Surface waves with periods of 15–200 s are the most effective triggering agents; body-wave trigger is less frequent. Triggering dynamic stresses can be < 1 kPa.

  19. Galactic dynamics

    CERN Document Server

    Binney, James

    2008-01-01

    Since it was first published in 1987, Galactic Dynamics has become the most widely used advanced textbook on the structure and dynamics of galaxies and one of the most cited references in astrophysics. Now, in this extensively revised and updated edition, James Binney and Scott Tremaine describe the dramatic recent advances in this subject, making Galactic Dynamics the most authoritative introduction to galactic astrophysics available to advanced undergraduate students, graduate students, and researchers. Every part of the book has been thoroughly overhauled, and many section

  20. Dynamic capabilities

    DEFF Research Database (Denmark)

    Grünbaum, Niels Nolsøe; Stenger, Marianne

    2013-01-01

    it was dominated by a lack of systematism, assessment, monitoring, marketing speculations and feasibility calculation. Furthermore, the sphere was dictated by asymmetric supplier-customer relationships and negotiation power leading, among other possible factors, to meager profitability.......The consequences of dynamic capabilities (i.e. innovation performance and profitability) is an under researched area in the growing body of literature on dynamic capabilities and innovation management. This study aims to examine the relationship between dynamic capabilities, innovation performance...... and profitability of small and medium sized manufacturing enterprises operating in volatile environments. A multi-case study design was adopted as research strategy. The findings reveal a positive relationship between dynamic capabilities and innovation performance in the case companies, as we would expect. It was...

  1. Dosimetric performance of the new high-definition multileaf collimator for intracranial stereotactic radiosurgery.

    Science.gov (United States)

    Dhabaan, Anees; Elder, Eric; Schreibmann, Eduard; Crocker, Ian; Curran, Walter J; Oyesiku, Nelson M; Shu, Hui-Kuo; Fox, Tim

    2010-06-21

    The objective was to evaluate the performance of a high-definition multileaf collimator (MLC) of 2.5 mm leaf width (MLC2.5) and compare to standard 5 mm leaf width MLC (MLC5) for the treatment of intracranial lesions using dynamic conformal arcs (DCA) technique with a dedicated radiosurgery linear accelerator. Simulated cases of spherical targets were created to study solely the effect of target volume size on the performance of the two MLC systems independent of target shape complexity. In addition, 43 patients previously treated for intracranial lesions in our institution were retrospectively planned using DCA technique with MLC2.5 and MLC5 systems. The gross tumor volume ranged from 0.07 to 40.57 cm3 with an average volume of 5.9 cm3. All treatment parameters were kept the same for both MLC-based plans. The plan evaluation was performed using figures of merits (FOM) for a rapid and objective assessment on the quality of the two treatment plans for MLC2.5 and MLC5. The prescription isodose surface was selected as the greatest isodose surface covering >or= 95% of the target volume and delivering 95% of the prescription dose to 99% of target volume. A Conformity Index (CI) and conformity distance index (CDI) were used to quantifying the dose conformity to a target volume. To assess normal tissue sparing, a normal tissue difference (NTD) was defined as the difference between the volume of normal tissue receiving a certain dose utilizing MLC5 and the volume receiving the same dose using MLC2.5. The CI and normal tissue sparing for the simulated spherical targets were better with the MLC2.5 as compared to MLC5. For the clinical patients, the CI and CDI results indicated that the MLC2.5 provides better treatment conformity than MLC5 even at large target volumes. The CI's range was 1.15 to 2.44 with a median of 1.59 for MLC2.5 compared to 1.60-2.85 with a median of 1.71 for MLC5. Improved normal tissue sparing was also observed for MLC2.5 over MLC5, with the NTD always

  2. Jumping Dynamics

    DEFF Research Database (Denmark)

    Sannino, Francesco

    2013-01-01

    We propose an alternative paradigm to the conjectured Miransky scaling potentially underlying the physics describing the transition from the conformally broken to the conformally restored phase when tuning certain parameters such as the number of flavors in gauge theories. According to the new...... paradigm the physical scale and henceforth also the massive spectrum of the theory jump at the lower boundary of the conformal window. In particular we propose that a theory can suddenly jump from a Quantum Chromodynamics type spectrum, at the lower boundary of the conformal window, to a conformal one...... without particle interpretation. The jumping scenario, therefore, does not support a near-conformal dynamics of walking type. We will also discuss the impact of jumping dynamics on the construction of models of dynamical electroweak symmetry breaking....

  3. Dynamic Bifurcations

    CERN Document Server

    1991-01-01

    Dynamical Bifurcation Theory is concerned with the phenomena that occur in one parameter families of dynamical systems (usually ordinary differential equations), when the parameter is a slowly varying function of time. During the last decade these phenomena were observed and studied by many mathematicians, both pure and applied, from eastern and western countries, using classical and nonstandard analysis. It is the purpose of this book to give an account of these developments. The first paper, by C. Lobry, is an introduction: the reader will find here an explanation of the problems and some easy examples; this paper also explains the role of each of the other paper within the volume and their relationship to one another. CONTENTS: C. Lobry: Dynamic Bifurcations.- T. Erneux, E.L. Reiss, L.J. Holden, M. Georgiou: Slow Passage through Bifurcation and Limit Points. Asymptotic Theory and Applications.- M. Canalis-Durand: Formal Expansion of van der Pol Equation Canard Solutions are Gevrey.- V. Gautheron, E. Isambe...

  4. Dual-Layer Nanostructured Flexible Thin-Film Amorphous Silicon Solar Cells with Enhanced Light Harvesting and Photoelectric Conversion Efficiency.

    Science.gov (United States)

    Lin, Yinyue; Xu, Zhen; Yu, Dongliang; Lu, Linfeng; Yin, Min; Tavakoli, Mohammad Mahdi; Chen, Xiaoyuan; Hao, Yuying; Fan, Zhiyong; Cui, Yanxia; Li, Dongdong

    2016-05-04

    Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth.

  5. Nanoporous BiVO4 photoanodes with dual-layer oxygen evolution catalysts for solar water splitting.

    Science.gov (United States)

    Kim, Tae Woo; Choi, Kyoung-Shin

    2014-02-28

    Bismuth vanadate (BiVO4) has a band structure that is well-suited for potential use as a photoanode in solar water splitting, but it suffers from poor electron-hole separation. Here, we demonstrate that a nanoporous morphology (specific surface area of 31.8 square meters per gram) effectively suppresses bulk carrier recombination without additional doping, manifesting an electron-hole separation yield of 0.90 at 1.23 volts (V) versus the reversible hydrogen electrode (RHE). We enhanced the propensity for surface-reaching holes to instigate water-splitting chemistry by serially applying two different oxygen evolution catalyst (OEC) layers, FeOOH and NiOOH, which reduces interface recombination at the BiVO4/OEC junction while creating a more favorable Helmholtz layer potential drop at the OEC/electrolyte junction. The resulting BiVO4/FeOOH/NiOOH photoanode achieves a photocurrent density of 2.73 milliamps per square centimenter at a potential as low as 0.6 V versus RHE.

  6. Dynamical systems

    CERN Document Server

    Birkhoff, George D

    1927-01-01

    His research in dynamics constitutes the middle period of Birkhoff's scientific career, that of maturity and greatest power. -Yearbook of the American Philosophical Society The author's great book€¦is well known to all, and the diverse active modern developments in mathematics which have been inspired by this volume bear the most eloquent testimony to its quality and influence. -Zentralblatt MATH In 1927, G. D. Birkhoff wrote a remarkable treatise on the theory of dynamical systems that would inspire many later mathematicians to do great work. To a large extent, Birkhoff was writing about his o

  7. Forest dynamics.

    Science.gov (United States)

    Frelich, Lee

    2016-01-01

    Forest dynamics encompass changes in stand structure, species composition, and species interactions with disturbance and environment over a range of spatial and temporal scales. For convenience, spatial scale is defined as individual tree, neighborhood, stand, and landscape. Whether a given canopy-leveling disturbance will initiate a sequence of development in structure with little change in composition or initiate an episode of succession depends on a match or mismatch, respectively, with traits of the dominant tree species that allow the species to survive disturbance. When these match, certain species-disturbance type combinations lock in a pattern of stand and landscape dynamics that can persist for several generations of trees; thus, dominant tree species regulate, as well as respond to, disturbance. A complex interaction among tree species, neighborhood effects, disturbance type and severity, landform, and soils determines how stands of differing composition form and the mosaic of stands that compose the landscape. Neighborhood effects (e.g., serotinous seed rain, sprouting, shading, leaf-litter chemistry, and leaf-litter physical properties) operate at small spatial extents of the individual tree and its neighbors but play a central role in forest dynamics by contributing to patch formation at stand scales and dynamics of the entire landscape. Dominance by tree species with neutral to negative neighborhood effects leads to unstable landscape dynamics in disturbance-prone regions, wherein most stands are undergoing succession; stability can only occur under very low-severity disturbance regimes. Dominance by species with positive effects leads to stable landscape dynamics wherein only a small proportion of stands undergo succession at any one time. Positive neighborhood effects are common in temperate and boreal zones, whereas negative effects are more common in tropical climates. Landscapes with positive dynamics have alternate categories of dynamics

  8. A system for EPID-based real-time treatment delivery verification during dynamic IMRT treatment

    Energy Technology Data Exchange (ETDEWEB)

    Fuangrod, Todsaporn [Faculty of Engineering and Built Environment, School of Electrical Engineering and Computer Science, the University of Newcastle, NSW 2308 (Australia); Woodruff, Henry C.; O’Connor, Daryl J. [Faculty of Science and IT, School of Mathematical and Physical Sciences, the University of Newcastle, NSW 2308 (Australia); Uytven, Eric van; McCurdy, Boyd M. C. [Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada); Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Department of Radiology, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Kuncic, Zdenka [School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Greer, Peter B. [Faculty of Science and IT, School of Mathematical and Physical Sciences, the University of Newcastle, NSW 2308, Australia and Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Locked Bag 7, Hunter region Mail Centre, Newcastle, NSW 2310 (Australia)

    2013-09-15

    Purpose: To design and develop a real-time electronic portal imaging device (EPID)-based delivery verification system for dynamic intensity modulated radiation therapy (IMRT) which enables detection of gross treatment delivery errors before delivery of substantial radiation to the patient.Methods: The system utilizes a comprehensive physics-based model to generate a series of predicted transit EPID image frames as a reference dataset and compares these to measured EPID frames acquired during treatment. The two datasets are using MLC aperture comparison and cumulative signal checking techniques. The system operation in real-time was simulated offline using previously acquired images for 19 IMRT patient deliveries with both frame-by-frame comparison and cumulative frame comparison. Simulated error case studies were used to demonstrate the system sensitivity and performance.Results: The accuracy of the synchronization method was shown to agree within two control points which corresponds to approximately ∼1% of the total MU to be delivered for dynamic IMRT. The system achieved mean real-time gamma results for frame-by-frame analysis of 86.6% and 89.0% for 3%, 3 mm and 4%, 4 mm criteria, respectively, and 97.9% and 98.6% for cumulative gamma analysis. The system can detect a 10% MU error using 3%, 3 mm criteria within approximately 10 s. The EPID-based real-time delivery verification system successfully detected simulated gross errors introduced into patient plan deliveries in near real-time (within 0.1 s).Conclusions: A real-time radiation delivery verification system for dynamic IMRT has been demonstrated that is designed to prevent major mistreatments in modern radiation therapy.

  9. Internetwork dynamics

    NARCIS (Netherlands)

    Rutten, R.J.

    1995-01-01

    This review places current research in quiet-Sun chromospheric dynamics in the context of past and future work, concentrating on observational aspects of three-minute oscillations and Ca II K2V grains. The subject is of interest at present because observations and simulations come together to permit

  10. Structural dynamics

    CERN Document Server

    Strømmen, Einar N

    2014-01-01

    This book introduces to the theory of structural dynamics, with focus on civil engineering structures that may be described by line-like beam or beam-column type of systems, or by a system of rectangular plates. Throughout this book the mathematical presentation contains a classical analytical description as well as a description in a discrete finite element format, covering the mathematical development from basic assumptions to the final equations ready for practical dynamic response predictions. Solutions are presented in time domain as well as in frequency domain. Structural Dynamics starts off at a basic level and step by step brings the reader up to a level where the necessary safety considerations to wind or horizontal ground motion induced dynamic design problems can be performed. The special theory of the tuned mass damper has been given a comprehensive treatment, as this is a theory not fully covered elsewhere. For the same reason a chapter on the problem of moving loads on beams has been included.

  11. Coastal Dynamics

    NARCIS (Netherlands)

    Bakker, W.T.

    1998-01-01

    This book deals on "Coastal Dynamics", which will be defined in a narrow sense as a mathematical theory, which starts from given equations of motion for the sediment, which leads with the continuity equation and given boundary conditions to a calculated (eventually schematized) coastal topography,

  12. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  13. Glassy Dynamics

    DEFF Research Database (Denmark)

    Jensen, Henrik J.; Sibani, Paolo

    2007-01-01

    The term glassy dynamics is often used to refer to the extremely slow relaxation observed in several types of many component systems. The time span needed to reach a steady, time independent, state will typically be far beyond experimentally accessible time scales. When melted alloys are cooled d...

  14. Dynamic LIMIDS

    NARCIS (Netherlands)

    Díez, F.J.; Gerven, M.A.J. van

    2011-01-01

    One of the objectives of artificial intelligence is to build decision-support models for systems that evolve over time and include several types of uncertainty. Dynamic limited-memory influence diagrams (DLIMIDs) are a new type of model proposed recently for this kind of problems. DLIMIDs are simila

  15. Dynamic LIMIDS

    NARCIS (Netherlands)

    Díez, F.J.; Gerven, M.A.J. van

    2011-01-01

    One of the objectives of artificial intelligence is to build decision-support models for systems that evolve over time and include several types of uncertainty. Dynamic limited-memory influence diagrams (DLIMIDs) are a new type of model proposed recently for this kind of problems. DLIMIDs are simila

  16. Record dynamics

    DEFF Research Database (Denmark)

    Robe, Dominic M.; Boettcher, Stefan; Sibani, Paolo

    2016-01-01

    -facto irreversible and become increasingly harder to achieve. Thus, a progression of record-sized dynamical barriers are traversed in the approach to equilibration. Accordingly, the statistics of the events is closely described by a log-Poisson process. Originally developed for relaxation in spin glasses...

  17. System Dynamics

    Science.gov (United States)

    Morecroft, John

    System dynamics is an approach for thinking about and simulating situations and organisations of all kinds and sizes by visualising how the elements fit together, interact and change over time. This chapter, written by John Morecroft, describes modern system dynamics which retains the fundamentals developed in the 1950s by Jay W. Forrester of the MIT Sloan School of Management. It looks at feedback loops and time delays that affect system behaviour in a non-linear way, and illustrates how dynamic behaviour depends upon feedback loop structures. It also recognises improvements as part of the ongoing process of managing a situation in order to achieve goals. Significantly it recognises the importance of context, and practitioner skills. Feedback systems thinking views problems and solutions as being intertwined. The main concepts and tools: feedback structure and behaviour, causal loop diagrams, dynamics, are practically illustrated in a wide variety of contexts from a hot water shower through to a symphony orchestra and the practical application of the approach is described through several real examples of its use for strategic planning and evaluation.

  18. Classical dynamics

    CERN Document Server

    Greenwood, Donald T

    1997-01-01

    Graduate-level text for science and technology students provides strong background in the more abstract and intellectually satisfying areas of dynamical theory. Topics include d'Alembert's principle and the idea of virtual work, Hamilton's equations, Hamilton-Jacobi theory, canonical transformations, more. Problems and references at chapter ends.

  19. Internetwork dynamics

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    This review places current research in quiet-Sun chromospheric dynamics in the context of past and future work, concentrating on observational aspects of three-minute oscillations and Ca II K2V grains. The subject is of interest at present because observations and simulations come together to permit

  20. Mitotic dynamics

    Institute of Scientific and Technical Information of China (English)

    唐孝威

    1996-01-01

    A new model for mitotic dynamics of eukaryotic cells is proposed. In the kinetochore mo-tor-midzone motor model two kinds of motors, the kinetochore motors and the midzone motors, play important roles in chromosome movement. Using this model the chromosome congression during prometaphase, the chromosome oscillation during metaphase and the chromatid segregation during anaphase are described in a unified way.

  1. Discrete dynamics versus analytic dynamics

    DEFF Research Database (Denmark)

    Toxværd, Søren

    2014-01-01

    For discrete classical Molecular dynamics obtained by the “Verlet” algorithm (VA) with the time increment h there exists a shadow Hamiltonian H˜ with energy E˜(h) , for which the discrete particle positions lie on the analytic trajectories for H˜ . Here, we proof that there, independent...

  2. Multilevel-clamped multilevel converters (MLC2)

    DEFF Research Database (Denmark)

    Rodriguez, Pedro; Bellar, Maria Dias; Muñoz-Aguliar, Raúl Santiago;

    2012-01-01

    This letter introduces a new series of multilevel (ML) converters based on the ML clamping concept. By applying this technique, a ML clamping unit (MCU) conveys additional levels for synthesizing the output waveforms of a diode-clampedML dc– ac power converter. The basic building block of the ML ...

  3. Applied dynamics

    CERN Document Server

    Schiehlen, Werner

    2014-01-01

    Applied Dynamics is an important branch of engineering mechanics widely applied to mechanical and automotive engineering, aerospace and biomechanics as well as control engineering and mechatronics. The computational methods presented are based on common fundamentals. For this purpose analytical mechanics turns out to be very useful where D’Alembert’s principle in the Lagrangian formulation proves to be most efficient. The method of multibody systems, finite element systems and continuous systems are treated consistently. Thus, students get a much better understanding of dynamical phenomena, and engineers in design and development departments using computer codes may check the results more easily by choosing models of different complexity for vibration and stress analysis.

  4. Fluid dynamics

    CERN Document Server

    Bernard, Peter S

    2015-01-01

    This book presents a focused, readable account of the principal physical and mathematical ideas at the heart of fluid dynamics. Graduate students in engineering, applied math, and physics who are taking their first graduate course in fluids will find this book invaluable in providing the background in physics and mathematics necessary to pursue advanced study. The book includes a detailed derivation of the Navier-Stokes and energy equations, followed by many examples of their use in studying the dynamics of fluid flows. Modern tensor analysis is used to simplify the mathematical derivations, thus allowing a clearer view of the physics. Peter Bernard also covers the motivation behind many fundamental concepts such as Bernoulli's equation and the stream function. Many exercises are designed with a view toward using MATLAB or its equivalent to simplify and extend the analysis of fluid motion including developing flow simulations based on techniques described in the book.

  5. Dynamic capabilities

    DEFF Research Database (Denmark)

    Grünbaum, Niels Nolsøe; Stenger, Marianne

    2013-01-01

    and profitability of small and medium sized manufacturing enterprises operating in volatile environments. A multi-case study design was adopted as research strategy. The findings reveal a positive relationship between dynamic capabilities and innovation performance in the case companies, as we would expect. It was...... it was dominated by a lack of systematism, assessment, monitoring, marketing speculations and feasibility calculation. Furthermore, the sphere was dictated by asymmetric supplier-customer relationships and negotiation power leading, among other possible factors, to meager profitability....

  6. Cybersecurity Dynamics

    Science.gov (United States)

    2014-08-20

    envisioned) Science of Cybersecurity:  Soul: Security (concepts)  Brain: Cybersecurity Dynamics (kind of Complexity Science)  Muscle & Blood ...Complexity Science)  Muscle & Blood : Probability Theory, Number Theory, Abstract Algebra, etc.  Thrust I: Building a systematic theory of...Under-specification, composition and emergent properties. In Proc. NSPW’97, pp. 83–93. [11] A. Kubík. Toward a formalization of emergence. Artif . Life

  7. Beam rate influence on dose distribution and fluence map in IMRT dynamic technique.

    Science.gov (United States)

    Slosarek, Krzysztof; Grządziel, Aleksandra; Osewski, Wojciech; Dolla, Lukasz; Bekman, Barbara; Petrovic, Borislava

    2012-01-01

    To examine the impact of beam rate on dose distribution in IMRT plans and then to evaluate agreement of calculated and measured dose distributions for various beam rate values. Accelerators used in radiotherapy utilize some beam rate modes which can shorten irradiation time and thus reduce ability of patient movement during a treatment session. This aspect should be considered in high conformal dynamic techniques. Dose calculation was done for two different beam rates (100 MU/min and 600 MU/min) in an IMRT plan. For both, a comparison of Radiation Planning Index (RPI) and MU was conducted. Secondly, the comparison of optimal fluence maps and corresponding actual fluence maps was done. Next, actual fluence maps were measured and compared with the calculated ones. Gamma index was used for that assessment. Additionally, positions of each leaf of the MLC were controlled by home made software. Dose distribution obtained for lower beam rates was slightly better than for higher beam rates in terms of target coverage and risk structure protection. Lower numbers of MUs were achieved in 100 MU/min plans than in 600 MU/min plans. Actual fluence maps converted from optimal ones demonstrated more similarity in 100 MU/min plans. Better conformity of the measured maps to the calculated ones was obtained when a lower beam rate was applied. However, these differences were small. No correlation was found between quality of fluence map conversion and leaf motion accuracy. Execution of dynamic techniques is dependent on beam rate. However, these differences are minor. Analysis shows a slight superiority of a lower beam rate. It does not significantly affect treatment accuracy.

  8. Hamiltonian dynamics

    CERN Document Server

    Vilasi, Gaetano

    2001-01-01

    This is both a textbook and a monograph. It is partially based on a two-semester course, held by the author for third-year students in physics and mathematics at the University of Salerno, on analytical mechanics, differential geometry, symplectic manifolds and integrable systems. As a textbook, it provides a systematic and self-consistent formulation of Hamiltonian dynamics both in a rigorous coordinate language and in the modern language of differential geometry. It also presents powerful mathematical methods of theoretical physics, especially in gauge theories and general relativity. As a m

  9. PREFACE: Cooperative dynamics Cooperative dynamics

    Science.gov (United States)

    Gov, Nir

    2011-09-01

    The dynamics within living cells are dominated by non-equilibrium processes that consume chemical energy (usually in the form of ATP, adenosine triphosphate) and convert it into mechanical forces and motion. The mechanisms that allow this conversion process are mostly driven by the components of the cytoskeleton: (i) directed (polar) polymerization of filaments (either actin or microtubules) and (ii) molecular motors. The forces and motions produced by these two components of the cytoskeleton give rise to the formation of cellular shapes, and drive the intracellular transport and organization. It is clear that these systems present a multi-scale challenge, from the physics of the molecular processes to the organization of many interacting units. Understanding the physical nature of these systems will have a large impact on many fundamental problems in biology and break new grounds in the field of non-equilibrium physics. This field of research has seen a rapid development over the last ten years. Activities in this area range from theoretical and experimental work on the underlying fundamental (bio)physics at the single-molecule level, to investigations (in vivo and in vitro) of the dynamics and patterns of macroscopic pieces of 'living matter'. In this special issue we have gathered contributions that span the whole spectrum of length- and complexity-scales in this field. Some of the works demonstrate how active forces self-organize within the polymerizing cytoskeleton, on the level of cooperative cargo transport via motors or due to active fluxes at the cell membrane. On a larger scale, it is shown that polar filaments coupled to molecular motors give rise to a huge variety of surprising dynamics and patterns: spontaneously looping rings of gliding microtubules, and emergent phases of self-organized filaments and motors in different geometries. All of these articles share the common feature of being out-of-equilibrium, driven by metabolism. As demonstrated here

  10. Complex dynamics

    CERN Document Server

    Carleson, Lennart

    1993-01-01

    Complex dynamics is today very much a focus of interest. Though several fine expository articles were available, by P. Blanchard and by M. Yu. Lyubich in particular, until recently there was no single source where students could find the material with proofs. For anyone in our position, gathering and organizing the material required a great deal of work going through preprints and papers and in some cases even finding a proof. We hope that the results of our efforts will be of help to others who plan to learn about complex dynamics and perhaps even lecture. Meanwhile books in the field a. re beginning to appear. The Stony Brook course notes of J. Milnor were particularly welcome and useful. Still we hope that our special emphasis on the analytic side will satisfy a need. This book is a revised and expanded version of notes based on lectures of the first author at UCLA over several \\Vinter Quarters, particularly 1986 and 1990. We owe Chris Bishop a great deal of gratitude for supervising the production of cour...

  11. Population dynamics

    Directory of Open Access Journals (Sweden)

    Cooch, E. G.

    2004-06-01

    Full Text Available Increases or decreases in the size of populations over space and time are, arguably, the motivation for much of pure and applied ecological research. The fundamental model for the dynamics of any population is straightforward: the net change over time in the abundance of some population is the simple difference between the number of additions (individuals entering the population minus the number of subtractions (individuals leaving the population. Of course, the precise nature of the pattern and process of these additions and subtractions is often complex, and population biology is often replete with fairly dense mathematical representations of both processes. While there is no doubt that analysis of such abstract descriptions of populations has been of considerable value in advancing our, there has often existed a palpable discomfort when the ‘beautiful math’ is faced with the often ‘ugly realities’ of empirical data. In some cases, this attempted merger is abandoned altogether, because of the paucity of ‘good empirical data’ with which the theoretician can modify and evaluate more conceptually–based models. In some cases, the lack of ‘data’ is more accurately represented as a lack of robust estimates of one or more parameters. It is in this arena that methods developed to analyze multiple encounter data from individually marked organisms has seen perhaps the greatest advances. These methods have rapidly evolved to facilitate not only estimation of one or more vital rates, critical to population modeling and analysis, but also to allow for direct estimation of both the dynamics of populations (e.g., Pradel, 1996, and factors influencing those dynamics (e.g., Nichols et al., 2000. The interconnections between the various vital rates, their estimation, and incorporation into models, was the general subject of our plenary presentation by Hal Caswell (Caswell & Fujiwara, 2004. Caswell notes that although interest has traditionally

  12. Multileaf collimator intercomparison for intensity modulated radiation therapy implementation; Intercomparacao de colimadores de multiplas laminas para implementacao de terapia de feixes de intensidade modulada

    Energy Technology Data Exchange (ETDEWEB)

    Viteri, Juan Fernando Delgado

    2006-07-01

    In this work a dosimetric comparison between three multileaf collimator systems is presented: a Varian Millennium with 120 leaves, Brainlab mMLC m3 and Varian Mark II both with 52 leaves. The width projection at isocenter level in field's central region are: 0,5 cm; 0,35 cm and 1,0 cm respectively. Common dosimetric characteristics for the three systems in static mode and dynamic capabilities for the two first were compared. In dynamic mode, tests validating proper MLC function through film irradiation were done, such MLC stability, MU linearity, treatment interruptions sensitivity, stability of MLC in dynamic mode, leaf speed stability, were found within {+-}3% deviation in all cases. Dose rate linearity showed differences when this parameter decreases in dynamic mode. Average dose errors for fixed width gaps moving at constant speed were found to be proportional to gap errors and inversely proportional to the gap width. Output factors differences delivered through a sweeping gap were found less than {+-}1% when the gantry was in a lateral position. For the three MLC systems, when comparing beam profiles for the same field was observed that for mMLC presents the sharpest dose gradient region. In the output factors small differences where observed in every MLC system. Dosimetric leaf gap was determined for MLC 120, mMLC and MLC 52, obtained values for a 6 MV beam are: (0,202 {+-} 0,054) cm; (0,157 {+-} 0,070) cm and (0,189 {+-} 0,081) cm respectively. The transmission showed an increase with depth and field width for 6 MV in all the three systems. Average values obtained with ionization chamber for this energy were: (1,630 {+-} 0,018)% for MLC 120; (1,291 {+-} 0,029)% for mMLC and (1,638 {+-} 0,010)% for MLC 52. When obtained through film irradiation, inter and intra leaf transmission showed an off axis dependent behavior for MLC 120 and mMLC. Scatter produced by MLC as a 6 MV open reference field ratio was: (0,297 {+-} 0,024)% for MLC 120; (0,239 {+-} 0

  13. Nonlinear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Turchetti, G. (Bologna Univ. (Italy). Dipt. di Fisica)

    1989-01-01

    Research in nonlinear dynamics is rapidly expanding and its range of applications is extending beyond the traditional areas of science where it was first developed. Indeed while linear analysis and modelling, which has been very successful in mathematical physics and engineering, has become a mature science, many elementary phenomena of intrinsic nonlinear nature were recently experimentally detected and investigated, suggesting new theoretical work. Complex systems, as turbulent fluids, were known to be governed by intrinsically nonlinear laws since a long time ago, but received purely phenomenological descriptions. The pioneering works of Boltzmann and Poincare, probably because of their intrinsic difficulty, did not have a revolutionary impact at their time; it is only very recently that their message is reaching a significant number of mathematicians and physicists. Certainly the development of computers and computer graphics played an important role in developing geometric intuition of complex phenomena through simple numerical experiments, while a new mathematical framework to understand them was being developed.

  14. Superconductor Dynamics

    CERN Document Server

    Gömöry, F

    2014-01-01

    Superconductors used in magnet technology could carry extreme currents because of their ability to keep the magnetic flux motionless. The dynamics of the magnetic flux interaction with superconductors is controlled by this property. The cases of electrical transport in a round wire and the magnetization of wires of various shapes (circular, elliptical, plate) in an external magnetic field are analysed. Resistance to the magnetic field penetration means that the field produced by the superconducting magnet is no longer proportional to the supplied current. It also leads to a dissipation of electromagnetic energy. In conductors with unequal transverse dimensions, such as flat cables, the orientation with respect to the magnetic field plays an essential role. A reduction of magnetization currents can be achieved by splitting the core of a superconducting wire into fine filaments; however, new kinds of electrical currents that couple the filaments consequently appear. Basic formulas allowing qualitative analyses ...

  15. Fluid dynamics

    CERN Document Server

    Ruban, Anatoly I

    This is the first book in a four-part series designed to give a comprehensive and coherent description of Fluid Dynamics, starting with chapters on classical theory suitable for an introductory undergraduate lecture course, and then progressing through more advanced material up to the level of modern research in the field. The present Part 1 consists of four chapters. Chapter 1 begins with a discussion of Continuum Hypothesis, which is followed by an introduction to macroscopic functions, the velocity vector, pressure, density, and enthalpy. We then analyse the forces acting inside a fluid, and deduce the Navier-Stokes equations for incompressible and compressible fluids in Cartesian and curvilinear coordinates. In Chapter 2 we study the properties of a number of flows that are presented by the so-called exact solutions of the Navier-Stokes equations, including the Couette flow between two parallel plates, Hagen-Poiseuille flow through a pipe, and Karman flow above an infinite rotating disk. Chapter 3 is d...

  16. Dynamic Processes

    Science.gov (United States)

    Klingshirn, C.

    The purpose of this chapter is to present the results of the dynamics of exciton (polariton)s or more generally of electron-hole pairs. For a recent review of this topic concentrating on quantum wells, see Davies and Jagadish (Laser Photon. Rev. 3(1), 1(2008)). We neither consider the dynamics of carriers, for example, their relaxation time entering in Hall mobility or electrical conductivity, nor the dynamics of phonons or spins, respectively. We give here only a very small selection of references to these topics (Baxter and Schmuttenmaer, J. Phys. Chem. B, 110:25229, 2006; Queiroz et al. Superlattice Microstruct. 42:270, 2007; Niehaus and Schwarz, Superlattice Microstruct. 42:299, 2007; Lee et al., J. Appl. Phys. 93:4939, 2003; A. K Azad, J. Han, W. Zhang, Appl. Phys. Lett. 88:021103, 2006; Janssen et al., QELS 2008 IEEE 2; D. Lagarde et al., Phys. Stat. Sol. C 4:472, 2007; S. Gosh et al., Appl. Phys. Lett. 86:232507, 2005; W. K. Liu et al. Phys. Rev. Lett. 98:186804, 2007). The main characteristic time constants relevant to optical properties close to the fundamental absorption edge are the dephasing time T 2, (i.e. the time after which the polarization amplitude of the optically excited electron-hole pair loses the coherence with the driving light field), the intra band or inter sub band relaxation times T 3 (i.e. the time it takes for the electron-hole pairs to relax from their initial state of excitation to a certain other state e.g. to a thermal distribution with a temperature equal to or possibly still above lattice temperature) and finally the lifetime T 1 (i.e. the time until the electron-hole pairs recombine). The characteristic time constants T 2 and T 1 are also known as transverse and longitudinal relaxation times, respectively. Their inverses are the corresponding rate constants. T 2 is inversely proportional to the homogeneous width Γ, and T 1 includes both the radiative and the generally dominating non-radiative recombination (Hauser et al., Appl

  17. Internet dynamics

    Science.gov (United States)

    Lukose, Rajan Mathew

    The World Wide Web and the Internet are rapidly expanding spaces, of great economic and social significance, which offer an opportunity to study many phenomena, often previously inaccessible, on an unprecedented scale and resolution with relative ease. These phenomena are measurable on the scale of tens of millions of users and hundreds of millions of pages. By virtue of nearly complete electronic mediation, it is possible in principle to observe the time and ``spatial'' evolution of nearly all choices and interactions. This cyber-space therefore provides a view into a number of traditional research questions (from many academic disciplines) and creates its own new phenomena accessible for study. Despite its largely self-organized and dynamic nature, a number of robust quantitative regularities are found in the aggregate statistics of interesting and useful quantities. These regularities can be understood with the help of models that draw on ideas from statistical physics as well as other fields such as economics, psychology and decision theory. This thesis develops models that can account for regularities found in the statistics of Internet congestion and user surfing patterns and discusses some practical consequences. practical consequences.

  18. Void Dynamics

    Science.gov (United States)

    Padilla, Nelson D.; Paz, Dante; Lares, Marcelo; Ceccarelli, Laura; Lambas, Diego Garcí A.; Cai, Yan-Chuan; Li, Baojiu

    2016-10-01

    Cosmic voids are becoming key players in testing the physics of our Universe.Here we concentrate on the abundances and the dynamics of voids as these are among the best candidatesto provide information on cosmological parameters. Cai, Padilla & Li (2014)use the abundance of voids to tell apart Hu & Sawicki f(R) models from General Relativity. An interestingresult is that even though, as expected, voids in the dark matter field are emptier in f(R) gravity due to the fifth force expellingaway from the void centres, this result is reversed when haloes are used to find voids. The abundance of voids in this casebecomes even lower in f(R) compared to GR for large voids. Still, the differences are significant and thisprovides a way to tell apart these models. The velocity field differences between f(R) and GR, on the other hand, arethe same for halo voids and for dark matter voids.Paz et al. (2013), concentrate on the velocity profiles around voids. First they show the necessityof four parameters to describe the density profiles around voids given two distinct voidpopulations, voids-in-voids and voids-in-clouds. This profile is used to predict peculiar velocities around voids,and the combination of the latter with void density profiles allows the construction of modelvoid-galaxy cross-correlation functions with redshift space distortions. When these modelsare tuned to fit the measured correlation functions for voids and galaxies in the SloanDigital Sky Survey, small voids are found to be of the void-in-cloud type, whereas largerones are consistent with being void-in-void. This is a novel result that is obtaineddirectly from redshift space data around voids. These profiles can be used toremove systematics on void-galaxy Alcock-Pacinsky tests coming from redshift-space distortions.

  19. Dynamical system synchronization

    CERN Document Server

    Luo, Albert C J

    2013-01-01

    Dynamical System Synchronization (DSS) meticulously presents for the first time the theory of dynamical systems synchronization based on the local singularity theory of discontinuous dynamical systems. The book details the sufficient and necessary conditions for dynamical systems synchronizations, through extensive mathematical expression. Techniques for engineering implementation of DSS are clearly presented compared with the existing techniques.  This book also:  Presents novel concepts and methods for dynamical system synchronization Extends beyond the Lyapunov theory for dynamical system synchronization Introduces companion and synchronization of discrete dynamical systems Includes local singularity theory for discontinuous dynamical systems Covers the invariant domains of synchronization Features more than 75 illustrations Dynamical System Synchronization is an ideal book for those interested in better understanding new concepts and methodology for dynamical system synchronization, local singularity...

  20. Fundamentals of structural dynamics

    CERN Document Server

    Craig, Roy R

    2006-01-01

    From theory and fundamentals to the latest advances in computational and experimental modal analysis, this is the definitive, updated reference on structural dynamics.This edition updates Professor Craig's classic introduction to structural dynamics, which has been an invaluable resource for practicing engineers and a textbook for undergraduate and graduate courses in vibrations and/or structural dynamics. Along with comprehensive coverage of structural dynamics fundamentals, finite-element-based computational methods, and dynamic testing methods, this Second Edition includes new and e

  1. OTTO MOTOR DYNAMICS

    OpenAIRE

    Petrescu, Florian Ion Tiberiu; Polytechnic University of Bucharest; Petrescu, Relly Victoria Virgil; Polytechnic University of Bucharest

    2016-01-01

    Otto engine dynamics are similar in almost all common internal combustion engines. We can speak so about dynamics of engines: Lenoir, Otto, and Diesel. The dynamic presented model is simple and original. The first thing necessary in the calculation of Otto engine dynamics, is to determine the inertial mass reduced at the piston. It uses then the Lagrange equation. The dynamic equation of motion of the piston, obtained by integrating the Lagrange equation, takes a new form. It presents a new r...

  2. Comparison of multileaf collimation and shield alloy blocks on an irregular target volume

    Energy Technology Data Exchange (ETDEWEB)

    Dirican, B.; Beyzadeoglu, M.; Turgay, H.T.; Pak, Y. [Gulhane Military Medical Academy, Ankara (Turkey)

    1996-09-01

    Multileaf collimation (MLC) is a crucial component dynamic conformal radiotherapy and can be used as a replacement for conventional blocks. The most appropriate volumetric approach for the lesion`s shape is achieved by MLC by conforming the prescribed dose to the critical structure or normal tissue dose. In this study, the edge effects of dose profiles on an irregular radiation field obtained by MLC and shield alloy blocks drawn by a water-phantom system were compared. We used a SL25 linac machine with MLC consisting of 40 pairs of opposing leaves and conventional alloy block shielding on a water phantom system. We found no significant edge effect difference between MLC and conventional shielding, but MLC showed clear advantages over conventional blocks in terms of time-saving, repeatability, and reliability. (author)

  3. Dynamical systems theory for music dynamics

    CERN Document Server

    Boon, J P

    1994-01-01

    Abstract:We show that, when music pieces are cast in the form of time series of pitch variations, the concepts and tools of dynamical systems theory can be applied to the analysis of {\\it temporal dynamics} in music. (i) Phase space portraits are constructed from the time series wherefrom the dimensionality is evaluated as a measure of the {\\pit global} dynamics of each piece. (ii) Spectral analysis of the time series yields power spectra (\\sim f^{-\

  4. Dosimetric comparison of intensity modulated radiosurgery with dynamic conformal arc radiosurgery for small cranial lesions

    Directory of Open Access Journals (Sweden)

    Juan F Calvo-Ortega

    2016-01-01

    Conclusions: We have shown that IMRS provides the dosimetric advantages compared with DCARS. Based on the dosimetric findings in this study, fixed gantry IMRS technique can be adopted as a standard procedure for cranial SRS when micro-MLC technology is not available on the linear accelerator.

  5. for hybrid dynamical systems

    Directory of Open Access Journals (Sweden)

    Wassim M. Haddad

    2001-01-01

    Full Text Available In this paper we develop a unified dynamical systems framework for a general class of systems possessing left-continuous flows; that is, left-continuous dynamical systems. These systems are shown to generalize virtually all existing notions of dynamical systems and include hybrid, impulsive, and switching dynamical systems as special cases. Furthermore, we generalize dissipativity, passivity, and nonexpansivity theory to left-continuous dynamical systems. Specifically, the classical concepts of system storage functions and supply rates are extended to left-continuous dynamical systems providing a generalized hybrid system energy interpretation in terms of stored energy, dissipated energy over the continuous-time dynamics, and dissipated energy over the resetting events. Finally, the generalized dissipativity notions are used to develop general stability criteria for feedback interconnections of left-continuous dynamical systems. These results generalize the positivity and small gain theorems to the case of left-continuous, hybrid, and impulsive dynamical systems.

  6. Vibro-impact dynamics

    CERN Document Server

    Luo, Albert C J

    2012-01-01

    Presents a systematic view of vibro-impact dynamics based on the nonlinear dynamics analysis Comprehensive understanding of any vibro-impact system is critically impeded by the lack of analytical tools viable for properly characterizing grazing bifurcation. The authors establish vibro-impact dynamics as a subset of the theory of discontinuous systems, thus enabling all vibro-impact systems to be explored and characterized for applications.  Vibro-impact Dynamics presents an original theoretical way of analyzing the behavior of vibro-impact dynamics that can be extended to discontinuous dynamic

  7. Dynamic statistical information theory

    Institute of Scientific and Technical Information of China (English)

    XING; Xiusan

    2006-01-01

    In recent years we extended Shannon static statistical information theory to dynamic processes and established a Shannon dynamic statistical information theory, whose core is the evolution law of dynamic entropy and dynamic information. We also proposed a corresponding Boltzmman dynamic statistical information theory. Based on the fact that the state variable evolution equation of respective dynamic systems, i.e. Fokker-Planck equation and Liouville diffusion equation can be regarded as their information symbol evolution equation, we derived the nonlinear evolution equations of Shannon dynamic entropy density and dynamic information density and the nonlinear evolution equations of Boltzmann dynamic entropy density and dynamic information density, that describe respectively the evolution law of dynamic entropy and dynamic information. The evolution equations of these two kinds of dynamic entropies and dynamic informations show in unison that the time rate of change of dynamic entropy densities is caused by their drift, diffusion and production in state variable space inside the systems and coordinate space in the transmission processes; and that the time rate of change of dynamic information densities originates from their drift, diffusion and dissipation in state variable space inside the systems and coordinate space in the transmission processes. Entropy and information have been combined with the state and its law of motion of the systems. Furthermore we presented the formulas of two kinds of entropy production rates and information dissipation rates, the expressions of two kinds of drift information flows and diffusion information flows. We proved that two kinds of information dissipation rates (or the decrease rates of the total information) were equal to their corresponding entropy production rates (or the increase rates of the total entropy) in the same dynamic system. We obtained the formulas of two kinds of dynamic mutual informations and dynamic channel

  8. Solar Dynamics Observatory

    Data.gov (United States)

    National Aeronautics and Space Administration — A searchable database of all Solar Dynamics Observatory data including EUV, magnetograms, visible light and X-ray. SDO: The Solar Dynamics Observatory is the first...

  9. Dynamic Interactive Learning Systems

    Science.gov (United States)

    Sabry, Khaled; Barker, Jeff

    2009-01-01

    This paper reviews and discusses the notions of interactivity and dynamicity of learning systems in relation to information technologies and design principles that can contribute to interactive and dynamic learning. It explores the concept of dynamic interactive learning systems based on the emerging generation of information as part of a…

  10. Intramolecular and nonlinear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M.J. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Research in this program focuses on three interconnected areas. The first involves the study of intramolecular dynamics, particularly of highly excited systems. The second area involves the use of nonlinear dynamics as a tool for the study of molecular dynamics and complex kinetics. The third area is the study of the classical/quantum correspondence for highly excited systems, particularly systems exhibiting classical chaos.

  11. Dynamics of Carroll particles

    NARCIS (Netherlands)

    Bergshoeff, Eric; Gomis, Joaquim; Longhi, Giorgio

    2014-01-01

    We investigate particles whose dynamics are invariant under the Carroll group. Although a single, free such Carroll particle has no non-trivial dynamics (the Carroll particle does not move), we show that non-trivial dynamics exists for a set of interacting Carroll particles. Furthermore, we gauge th

  12. The dynamics of scaffolding

    NARCIS (Netherlands)

    Van Geert, P. L. C.; Steenbeek, H.W.

    2005-01-01

    In this article we have reinterpreted a relatively standard definition of scaffolding in the context of dynamic systems theory. Our main point is that scaffolding cannot be understood outside the context of a dynamic approach of learning and (formal or informal) teaching. We provide a dynamic system

  13. TU-CD-304-01: FEATURED PRESENTATION and BEST IN PHYSICS (THERAPY): Trajectory Modulated Arc Therapy: Development of Novel Arc Delivery Techniques Integrating Dynamic Table Motion for Extended Volume Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Chin, E; Hoppe, R; Million, L; Loo, B; Koong, A; Xing, L; Hsu, A; Fahimian, B [Stanford University, Stanford, CA (United States); Otto, K [University of British Columbia, Vancouver, BC (Canada)

    2015-06-15

    Purpose: Integration of coordinated robotic table motion with inversely-planned arc delivery has the potential to resolve table-top delivery limitations of large-field treatments such as Total Body Irradiation (TBI), Total Lymphoid Irradiation (TLI), and Cranial-Spinal Irradiation (CSI). We formulate the foundation for Trajectory Modulated Arc Therapy (TMAT), and using Varian Developer Mode capabilities, experimentally investigate its practical implementation for such techniques. Methods: A MATLAB algorithm was developed for inverse planning optimization of the table motion, MLC positions, and gantry motion under extended-SSD geometry. To maximize the effective field size, delivery trajectories for TMAT TBI were formed with the table rotated at 270° IEC and dropped vertically to 152.5cm SSD. Preliminary testing of algorithm parameters was done through retrospective planning analysis. Robotic delivery was programmed using custom XML scripting on the TrueBeam Developer Mode platform. Final dose was calculated using the Eclipse AAA algorithm. Initial verification of delivery accuracy was measured using OSLDs on a solid water phantom of varying thickness. Results: A comparison of DVH curves demonstrated that dynamic couch motion irradiation was sufficiently approximated by static control points spaced in intervals of less than 2cm. Optimized MLC motion decreased the average lung dose to 68.5% of the prescription dose. The programmed irradiation integrating coordinated table motion was deliverable on a TrueBeam STx linac in 6.7 min. With the couch translating under an open 10cmx20cm field angled at 10°, OSLD measurements along the midline of a solid water phantom at depths of 3, 5, and 9cm were within 3% of the TPS AAA algorithm with an average deviation of 1.2%. Conclusion: A treatment planning and delivery system for Trajectory Modulated Arc Therapy of extended volumes has been established and experimentally demonstrated for TBI. Extension to other treatment

  14. Monte Carlo evaluation of the dose calculation algorithm of TomoTherapy for clinical cases in dynamic jaws mode.

    Science.gov (United States)

    Sterpin, E

    2015-05-01

    For the TomoTherapy(®) system, longitudinal conformation can be improved by selecting a smaller field width but at the expense of longer treatment time. Recently, the TomoEdge(®) feature has been released with the possibility to move dynamically the jaws at the edges of the target volume, improving longitudinal penumbra and enabling faster treatments. Such delivery scheme requires additional modeling of treatment delivery. Using a previously validated Monte Carlo model (TomoPen), we evaluated the accuracy of the implementation of TomoEdge in the new dose engine of TomoTherapy for 15 clinical cases. TomoPen is based on PENELOPE. Particle tracking in the treatment head is performed almost instantaneously by 1) reading a particle from a phase-space file corresponding to the largest field and 2) correcting the weight of the particle depending on the actual jaw and MLC configurations using Monte Carlo pre-generated data. 15 clinical plans (5 head-and-neck, 5 lung and 5 prostate tumors) planned with TomoEdge and with the last release of the treatment planning system (VoLO(®)) were re-computed with TomoPen. The resulting dose-volume histograms were compared. Good agreement was achieved overall, with deviations for the target volumes typically within 2% (D95), excepted for small lung tumors (17 cm(3)) where a maximum deviation of 4.4% was observed for D95. The results were consistent with previously reported values for static field widths. For the clinical cases considered in the present study, the introduction of TomoEdge did not impact significantly the accuracy of the computed dose distributions. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  15. Dynamics at Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sylvia Ceyer, Nancy Ryan Gray

    2010-05-04

    The 2009 Gordon Conference on Dynamics at Surfaces is the 30th anniversary of a meeting held every two years that is attended by leading researchers in the area of experimental and theoretical dynamics at liquid and solid surfaces. The conference focuses on the dynamics of the interaction of molecules with either liquid or solid surfaces, the dynamics of the outermost layer of liquid and solid surfaces and the dynamics at the liquid-solid interface. Specific topics that are featured include state-to-state dynamics, non-adiabatic interactions in molecule-metal systems, photon induced desorption from semiconductor and metal surfaces, ultrafast x-ray and electron diffraction as probes of the dynamics of ablation, ultrafast vibrational spectroscopy of water surface dynamics, dynamics of a single adsorbate, growth at nano-scale mineral surfaces, dynamics of atom recombination on interstellar dust grains and the dynamics of the interaction of water with lipid bilayers. The conference brings together investigators from a variety of scientific disciplines including chemistry, physics, materials science, geology and biophysics.

  16. Variable Dynamic Testbed Vehicle: Dynamics Analysis

    Science.gov (United States)

    Lee, A. Y.; Le, N. T.; Marriott, A. T.

    1997-01-01

    The Variable Dynamic Testbed Vehicle (VDTV) concept has been proposed as a tool to evaluate collision avoidance systems and to perform driving-related human factors research. The goal of this study is to analytically investigate to what extent a VDTV with adjustable front and rear anti-roll bar stiffnesses, programmable damping rates, and four-wheel-steering can emulate the lateral dynamics of a broad range of passenger vehicles.

  17. SU-E-T-140: Dynamic Wave Arc Trajectory Verification Using KV X-Ray Fluoroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Burghelea, M; Poels, K; Depuydt, T; Tournel, K; Verellen, D; De Ridder, M [Universitair Ziekenhuis Brussel, Jette, Brussels (Belgium)

    2014-06-01

    Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/Ring rotation during Dynamic Wave Arc (DWA) delivery. Methods: The Vero SBRT system consists of a 6MV LINAC mounted on an O-ring gantry that can rotate around the vertical axis (±60°), similar to couch rotation on C-arm gantries. To provide CBCT and fluoroscopy imaging functionalities, two orthogonal kV imaging units are attached to the O-ring at −45°/+45° from the beam axis.Dynamic Wave Arc maximizes Vero's motion capabilities by employing synchronized gantry and ring motion on a complex non-coplanar trajectory in combination with aperture based optimized MLC segments.Four wave arc trajectories (T1-4) were delivered using a cubic phantom with a configuration of five lead beads. O-ring gantry position information was retrieved through continuous dual-source kV X-ray image acquisition during DWA. An in-house algorithm read in the image set, extracted the projected marker positions and determined the angulation through reconstruction of the beam source position. The geometric error was quantified as the distance between the independently detected positions from kV-images and reference trajectory derived from the treatment plan in the Ring-Gantry space. Results: The average displacement between the 3D gantry/ring positions reconstructed from the fluoroscopy images and the reference trajectory was 0.346 mm (SD 0,171) for T1. A mean offset of 0.348 mm (SD 0,182) and 0.357 mm (SD 0.194) was observed for trajectory T2(2segmens) and T3(4segments), respectively. The saw shape T4 presented a mean geometric error of 0.363 (SD 0.156). The overall systematic error of 0.350 was caused by the difference between planned reference trajectory created by linear interpolation between CP, and the machine delivery following a spline curve. Conclusion: An independent geometric QA approach has been developed for DWA delivery verification, successfully applied on diverse trajectories and

  18. Complexity and Dynamical Depth

    Directory of Open Access Journals (Sweden)

    Terrence Deacon

    2014-07-01

    Full Text Available We argue that a critical difference distinguishing machines from organisms and computers from brains is not complexity in a structural sense, but a difference in dynamical organization that is not well accounted for by current complexity measures. We propose a measure of the complexity of a system that is largely orthogonal to computational, information theoretic, or thermodynamic conceptions of structural complexity. What we call a system’s dynamical depth is a separate dimension of system complexity that measures the degree to which it exhibits discrete levels of nonlinear dynamical organization in which successive levels are distinguished by local entropy reduction and constraint generation. A system with greater dynamical depth than another consists of a greater number of such nested dynamical levels. Thus, a mechanical or linear thermodynamic system has less dynamical depth than an inorganic self-organized system, which has less dynamical depth than a living system. Including an assessment of dynamical depth can provide a more precise and systematic account of the fundamental difference between inorganic systems (low dynamical depth and living systems (high dynamical depth, irrespective of the number of their parts and the causal relations between them.

  19. Synchronization dynamics of two different dynamical systems

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Albert C.J., E-mail: aluo@siue.edu [Department of Mechanical and Industrial Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1805 (United States); Min Fuhong [Department of Mechanical and Industrial Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1805 (United States)

    2011-06-15

    Highlights: > Synchronization dynamics of two distinct dynamical systems. > Synchronization, de-synchronization and instantaneous synchronization. > A controlled pendulum synchronizing with the Duffing oscillator. > Synchronization invariant set. > Synchronization parameter map. - Abstract: In this paper, synchronization dynamics of two different dynamical systems is investigated through the theory of discontinuous dynamical systems. The necessary and sufficient conditions for the synchronization, de-synchronization and instantaneous synchronization (penetration or grazing) are presented. Using such a synchronization theory, the synchronization of a controlled pendulum with the Duffing oscillator is systematically discussed as a sampled problem, and the corresponding analytical conditions for the synchronization are presented. The synchronization parameter study is carried out for a better understanding of synchronization characteristics of the controlled pendulum and the Duffing oscillator. Finally, the partial and full synchronizations of the controlled pendulum with periodic and chaotic motions are presented to illustrate the analytical conditions. The synchronization of the Duffing oscillator and pendulum are investigated in order to show the usefulness and efficiency of the methodology in this paper. The synchronization invariant domain is obtained. The technique presented in this paper should have a wide spectrum of applications in engineering. For example, this technique can be applied to the maneuvering target tracking, and the others.

  20. Multiscale Gentlest Ascent Dynamics

    CERN Document Server

    Zhou, Xiang

    2016-01-01

    The gentlest ascent dynamics (E and Zhou in {\\it Nonlinearity} vol 24, p1831, 2011) locally converges to a nearby saddle point with one dimensional unstable manifold. Here we present a multiscale gentlest ascent dynamics for stochastic slow-fast systems in order to compute saddle point associated with the effective dynamics of the slow variable. Such saddle points, as the candidates of transition states, are important in non-equilibrium transitions for the coarse-grained slow variables; they are also helpful to explore free energy surface. We derive the expressions of the gentlest ascent dynamics for the averaged system, and propose the multiscale numerical methods to efficiently solve the multiscale gentlest ascent dynamics for search of saddle point. The examples of stochastic ordinary and partial differential equations are presented to illustrate the performance of this multiscale gentlest ascent dynamics.

  1. Dynamics of Media Attention

    CERN Document Server

    Traag, V A; Hicks, J; van Klinken, G

    2014-01-01

    Studies of human attention dynamics analyses how attention is focused on specific topics, issues or people. In online social media, there are clear signs of exogenous shocks, bursty dynamics, and an exponential or powerlaw lifetime distribution. We here analyse the attention dynamics of traditional media, focussing on co-occurrence of people in newspaper articles. The results are quite different from online social networks and attention. Different regimes seem to be operating at two different time scales. At short time scales we see evidence of bursty dynamics and fast decaying edge lifetimes and attention. This behaviour disappears for longer time scales, and in that regime we find Poissonian dynamics and slower decaying lifetimes. We propose that a cascading Poisson process may take place, with issues arising at a constant rate over a long time scale, and faster dynamics at a shorter time scale.

  2. Dynamic Boiler Performance

    DEFF Research Database (Denmark)

    Sørensen, Kim

    Traditionally, boilers have been designed mainly focussing on the static operation of the plant. The dynamic capability has been given lower priority and the analysis has typically been limited to assuring that the plant was not over-stressed due to large temperature gradients. New possibilities...... for buying and selling energy has increased the focus on the dynamic operation capability, efciency, emissions etc. For optimizing the design of boilers for dynamic operation a quantication of the dynamic capability is needed. A framework for optimizing design of boilers for dynamic operation has been...... developed. Analyzing boilers for dynamic operation gives rise to a number of opposing aims: shrinking and swelling, steam quality, stress levels, control system/philosophy, pressurization etc. Common for these opposing aims is that an optimum can be found for selected operation conditions. The framework has...

  3. Dynamic Capabilities and Performance

    DEFF Research Database (Denmark)

    Wilden, Ralf; Gudergan, Siegfried P.; Nielsen, Bo Bernhard

    2013-01-01

    Dynamic capabilities are widely considered to incorporate those processes that enable organizations to sustain superior performance over time. In this paper, we argue theoretically and demonstrate empirically that these effects are contingent on organizational structure and the competitive...... are contingent on the competitive intensity faced by firms. Our findings demonstrate the performance effects of internal alignment between organizational structure and dynamic capabilities, as well as the external fit of dynamic capabilities with competitive intensity. We outline the advantages of PLS...

  4. Dynamical Constraints on Exoplanets

    CERN Document Server

    Horner, Jonti; Tinney, Chris; Hinse, Tobias C; Marshall, Jonathan P

    2013-01-01

    Dynamical studies of new exoplanet systems are a critical component of the discovery and characterisation process. Such studies can provide firmer constraints on the parameters of the newly discovered planets, and may even reveal that the proposed planets do not stand up to dynamical scrutiny. Here, we demonstrate how dynamical studies can assist the characterisation of such systems through two examples: QS Virginis and HD 73526.

  5. ON NONDETERMINISTIC DYNAMIC PROGRAMMING

    OpenAIRE

    2008-01-01

    R. Bellman left a lot of research problems in his work “Dynamic Programming" (1957). Having received ideas from Bellman, S. Iwamoto has extracted, out of his problems, a problem on nondeterministic dynamic programming (NDP). Instead of stochastic dynamic programming which has been well studied, Iwamoto has opened a gate to NDP. This report presents speci_c optimal solutions for NDPs on continuous state and decision spaces.

  6. Dynamical Systems Conference

    CERN Document Server

    Gils, S; Hoveijn, I; Takens, F; Nonlinear Dynamical Systems and Chaos

    1996-01-01

    Symmetries in dynamical systems, "KAM theory and other perturbation theories", "Infinite dimensional systems", "Time series analysis" and "Numerical continuation and bifurcation analysis" were the main topics of the December 1995 Dynamical Systems Conference held in Groningen in honour of Johann Bernoulli. They now form the core of this work which seeks to present the state of the art in various branches of the theory of dynamical systems. A number of articles have a survey character whereas others deal with recent results in current research. It contains interesting material for all members of the dynamical systems community, ranging from geometric and analytic aspects from a mathematical point of view to applications in various sciences.

  7. Dynamics of machinery

    CERN Document Server

    Dresig, Hans

    2010-01-01

    Dynamic loads and disturbing oscillations increase with higher speed of the machines and more lightweight constructions. Industrial safety standards require better oscillation reduction and noise control. The book by Dresig/Holzweissig deals with these topics. It presents the classical areas of modeling, dynamics of rigid bodies, balancing, torsional and bending vibrations, problems of vibration isolation and the dynamic behavior of complex vibrating systems. Typical dynamic effects, i.e., the gyroscopic effect, the damping of oscillations, resonances of k-th order, subharmonic and nonlinear f

  8. Structural Dynamics Laboratory (SDL)

    Data.gov (United States)

    Federal Laboratory Consortium — Structural dynamic testing is performed to verify the survivability of a component or assembly when exposed to vibration stress screening, or a controlled simulation...

  9. Symplectic algebraic dynamics algorithm

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the algebraic dynamics solution of ordinary differential equations andintegration of  ,the symplectic algebraic dynamics algorithm sn is designed,which preserves the local symplectic geometric structure of a Hamiltonian systemand possesses the same precision of the na ve algebraic dynamics algorithm n.Computer experiments for the 4th order algorithms are made for five test modelsand the numerical results are compared with the conventional symplectic geometric algorithm,indicating that sn has higher precision,the algorithm-inducedphase shift of the conventional symplectic geometric algorithm can be reduced,and the dynamical fidelity can be improved by one order of magnitude.

  10. Nonlinear dynamics and complexity

    CERN Document Server

    Luo, Albert; Fu, Xilin

    2014-01-01

    This important collection presents recent advances in nonlinear dynamics including analytical solutions, chaos in Hamiltonian systems, time-delay, uncertainty, and bio-network dynamics. Nonlinear Dynamics and Complexity equips readers to appreciate this increasingly main-stream approach to understanding complex phenomena in nonlinear systems as they are examined in a broad array of disciplines. The book facilitates a better understanding of the mechanisms and phenomena in nonlinear dynamics and develops the corresponding mathematical theory to apply nonlinear design to practical engineering.

  11. Essential dynamics and relativity

    CERN Document Server

    O'Donnell, Peter J

    2014-01-01

    Essential Dynamics & Relativity provides students with an introduction to the core aspects of dynamics and special relativity. The author reiterates important ideas and terms throughout and covers concepts that are often missing from other textbooks at this level. He also places each topic within the wider constructs of the theory, without jumping from topic to topic to illustrate a point.The first section of the book focuses on dynamics, discussing the basic aspects of single particle motion and analyzing the motion of multi-particle systems. The book also explains the dynamical behavior of b

  12. Introduction to dynamic programming

    CERN Document Server

    Cooper, Leon; Rodin, E Y

    1981-01-01

    Introduction to Dynamic Programming provides information pertinent to the fundamental aspects of dynamic programming. This book considers problems that can be quantitatively formulated and deals with mathematical models of situations or phenomena that exists in the real world.Organized into 10 chapters, this book begins with an overview of the fundamental components of any mathematical optimization model. This text then presents the details of the application of dynamic programming to variational problems. Other chapters consider the application of dynamic programming to inventory theory, Mark

  13. Dynamic power flow controllers

    Science.gov (United States)

    Divan, Deepakraj M.; Prasai, Anish

    2017-03-07

    Dynamic power flow controllers are provided. A dynamic power flow controller may comprise a transformer and a power converter. The power converter is subject to low voltage stresses and not floated at line voltage. In addition, the power converter is rated at a fraction of the total power controlled. A dynamic power flow controller controls both the real and the reactive power flow between two AC sources having the same frequency. A dynamic power flow controller inserts a voltage with controllable magnitude and phase between two AC sources; thereby effecting control of active and reactive power flows between two AC sources.

  14. Partial Dynamical Symmetry and Mixed Dynamics

    CERN Document Server

    Leviatan, A

    1996-01-01

    Partial dynamical symmetry describes a situation in which some eigenstates have a symmetry which the quantum Hamiltonian does not share. This property is shown to have a classical analogue in which some tori in phase space are associated with a symmetry which the classical Hamiltonian does not share. A local analysis in the vicinity of these special tori reveals a neighbourhood of phase space foliated by tori. This clarifies the suppression of classical chaos associated with partial dynamical symmetry. The results are used to divide the states of a mixed system into ``chaotic'' and ``regular'' classes.

  15. Dynamical Non-Equilibrium Molecular Dynamics

    Directory of Open Access Journals (Sweden)

    Giovanni Ciccotti

    2013-12-01

    Full Text Available In this review, we discuss the Dynamical approach to Non-Equilibrium Molecular Dynamics (D-NEMD, which extends stationary NEMD to time-dependent situations, be they responses or relaxations. Based on the original Onsager regression hypothesis, implemented in the nineteen-seventies by Ciccotti, Jacucci and MacDonald, the approach permits one to separate the problem of dynamical evolution from the problem of sampling the initial condition. D-NEMD provides the theoretical framework to compute time-dependent macroscopic dynamical behaviors by averaging on a large sample of non-equilibrium trajectories starting from an ensemble of initial conditions generated from a suitable (equilibrium or non-equilibrium distribution at time zero. We also discuss how to generate a large class of initial distributions. The same approach applies also to the calculation of the rate constants of activated processes. The range of problems treatable by this method is illustrated by discussing applications to a few key hydrodynamic processes (the “classical” flow under shear, the formation of convective cells and the relaxation of an interface between two immiscible liquids.

  16. Dynamic normal forms and dynamic characteristic polynomial

    DEFF Research Database (Denmark)

    Frandsen, Gudmund Skovbjerg; Sankowski, Piotr

    2011-01-01

    with relative error 2−b in additional O(nlog2nlogb) time. Furthermore, it can be used to dynamically maintain the singular value decomposition (SVD) of a generic matrix. Together with the algorithm, the hardness of the problem is studied. For the symmetric case, we present an Ω(n2) lower bound for rank...

  17. Bisimulation of Dynamical Systems

    NARCIS (Netherlands)

    Schaft, Arjan van der

    2004-01-01

    A general notion of bisimulation is studied for dynamical systems. An algebraic characterization of bisimulation together with an algorithm for computing the maximal bisimulation relation is derived using geometric control theory. Bisimulation of dynamical systems is shown to be a concept which

  18. Dynamic Calorimetry for Students

    Science.gov (United States)

    Kraftmakher, Yaakov

    2007-01-01

    A student experiment on dynamic calorimetry is described. Dynamic calorimetry is a powerful technique for calorimetric studies, especially at high temperatures and pressures. A low-power incandescent lamp serves as the sample. The ScienceWorkshop data-acquisition system with DataStudio software from PASCO Scientific displays the results of the…

  19. Dynamic Latent Classification Model

    DEFF Research Database (Denmark)

    Zhong, Shengtong; Martínez, Ana M.; Nielsen, Thomas Dyhre

    as possible. Motivated by this problem setting, we propose a generative model for dynamic classification in continuous domains. At each time point the model can be seen as combining a naive Bayes model with a mixture of factor analyzers (FA). The latent variables of the FA are used to capture the dynamics...... in the process as well as modeling dependences between attributes....

  20. Space Manifold dynamics

    OpenAIRE

    Gómez, Gerard; Barrabés Vera, Esther

    2011-01-01

    The term Space Manifold Dynamics (SMD) has been proposed for encompassing the various applications of Dynamical Systems methods to spacecraft mission analysis and design, ranging from the exploitation of libration orbits around the collinear Lagrangian points to the design of optimal station-keeping and eclipse avoidance manoeuvres or the determination of low energy lunar and interplanetary transfers

  1. Team coordination dynamics.

    Science.gov (United States)

    Gorman, Jamie C; Amazeen, Polemnia G; Cooke, Nancy J

    2010-07-01

    Team coordination consists of both the dynamics of team member interaction and the environmental dynamics to which a team is subjected. Focusing on dynamics, an approach is developed that contrasts with traditional aggregate-static concepts of team coordination as characterized by the shared mental model approach. A team coordination order parameter was developed to capture momentary fluctuations in coordination. Team coordination was observed in three-person uninhabited air vehicle teams across two experimental sessions. The dynamics of the order parameter were observed under changes of a team familiarity control parameter. Team members returned for the second session to either the same (Intact) or different (Mixed) team. 'Roadblock' perturbations, or novel changes in the task environment, were introduced in order to probe the stability of team coordination. Nonlinear dynamic methods revealed differences that a traditional approach did not: Intact and Mixed team coordination dynamics looked very different; Mixed teams were more stable than Intact teams and explored the space of solutions without the need for correction. Stability was positively correlated with the number of roadblock perturbations that were overcome successfully. The novel and non-intuitive contribution of a dynamical analysis was that Mixed teams, who did not have a long history working together, were more adaptive. Team coordination dynamics carries new implications for traditional problems such as training adaptive teams.

  2. Dynamic defense workshop :

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, Sean Michael; Doak, Justin E.; Haas, Jason Juedes.; Helinski, Ryan; Lamb, Christopher C.

    2013-02-01

    On September 5th and 6th, 2012, the Dynamic Defense Workshop: From Research to Practice brought together researchers from academia, industry, and Sandia with the goals of increasing collaboration between Sandia National Laboratories and external organizations, de ning and un- derstanding dynamic, or moving target, defense concepts and directions, and gaining a greater understanding of the state of the art for dynamic defense. Through the workshop, we broadened and re ned our de nition and understanding, identi ed new approaches to inherent challenges, and de ned principles of dynamic defense. Half of the workshop was devoted to presentations of current state-of-the-art work. Presentation topics included areas such as the failure of current defenses, threats, techniques, goals of dynamic defense, theory, foundations of dynamic defense, future directions and open research questions related to dynamic defense. The remainder of the workshop was discussion, which was broken down into sessions on de ning challenges, applications to host or mobile environments, applications to enterprise network environments, exploring research and operational taxonomies, and determining how to apply scienti c rigor to and investigating the eld of dynamic defense.

  3. Dynamical inverse problems

    CERN Document Server

    Gladwell, Graham ML

    2011-01-01

    The papers in this volume present an overview of the general aspects and practical applications of dynamic inverse methods, through the interaction of several topics, ranging from classical and advanced inverse problems in vibration, isospectral systems, dynamic methods for structural identification, active vibration control and damage detection, imaging shear stiffness in biological tissues, wave propagation, to computational and experimental aspects relevant for engineering problems.

  4. Transformations, Dynamics and Complexity

    CERN Document Server

    Glazunov, Nikolaj

    2011-01-01

    We review and investigate some new problems and results in the field of dynamical systems generated by iteration of maps, {\\beta}-transformations, partitions, group actions, bundle dynamical systems, Hasse-Kloosterman maps, and some aspects of complexity of the systems.

  5. EU Budgetary Dynamics

    DEFF Research Database (Denmark)

    Citi, Manuele

    2013-01-01

    and change in the EU in light of the two models of policy dynamics currently existing in the literature: the incrementalist model and the punctuated equilibrium model. The analysis of long series of original data extracted from the EU budget shows that EU policies do not evolve following an incrementalist...... pattern, but by a punctuated equilibrium dynamic....

  6. Dynamic public service mediation

    NARCIS (Netherlands)

    Hofman, W.; Staalduinen, M. van

    2010-01-01

    This paper presents an approach to dynamic public service mediation. It is based on a conceptual model and the use of search and ranking algorithms. The conceptual model is based on Abstract State Machine theory. Requirements for dynamic service mediation were derived from a real-world case. The con

  7. Probabilistic Dynamic Epistemic Logic

    NARCIS (Netherlands)

    Kooi, B.P.

    2003-01-01

    In this paper I combine the dynamic epistemic logic of Gerbrandy (1999) with the probabilistic logic of Fagin and Halpern (1999). The result is a new probabilistic dynamic epistemic logic, a logic for reasoning about probability, information, and information change that takes higher order informatio

  8. Visualizing Dynamic Memory Allocations

    NARCIS (Netherlands)

    Moreta, Sergio; Telea, Alexandru

    2007-01-01

    We present a visualization tool for dynamic memory allocation information obtained from instrumenting the runtime allocator used by C programs. The goal of the presented visualization techniques is to convey insight in the dynamic behavior of the allocator. The purpose is to help the allocator desig

  9. Dynamic covalent surfactants

    NARCIS (Netherlands)

    Minkenberg, C.B.

    2012-01-01

    In this thesis the development of surfactant aggregates with fast exchange dynamics between the aggregated and non-aggregated state is described. Dynamic surfactant exchange plays an important role in natural systems, for instance in cell signaling, cell division, and uptake and release of cargo. Re

  10. Applications of fluid dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Round, G.R.; Garg, V.K.

    1986-01-01

    This book describes flexible and practical approach to learning the basics of fluid dynamics. Each chapter is a self-contained work session and includes a fluid dynamics concept, an explanation of the principles involved, an illustration of their application and references on where more detailed discussions can be found.

  11. Dynamic Calorimetry for Students

    Science.gov (United States)

    Kraftmakher, Yaakov

    2007-01-01

    A student experiment on dynamic calorimetry is described. Dynamic calorimetry is a powerful technique for calorimetric studies, especially at high temperatures and pressures. A low-power incandescent lamp serves as the sample. The ScienceWorkshop data-acquisition system with DataStudio software from PASCO Scientific displays the results of the…

  12. Dynamic reservoir well interaction

    NARCIS (Netherlands)

    Sturm, W.L.; Belfroid, S.P.C.; Wolfswinkel, O. van; Peters, M.C.A.M.; Verhelst, F.J.P.C.M.

    2004-01-01

    In order to develop smart well control systems for unstable oil wells, realistic modeling of the dynamics of the well is essential. Most dynamic well models use a semi-steady state inflow model to describe the inflow of oil and gas from the reservoir. On the other hand, reservoir models use steady s

  13. Dual-layered nanogel-coated hollow lipid/polypeptide conjugate assemblies for potential pH-triggered intracellular drug release.

    Directory of Open Access Journals (Sweden)

    Wen-Hsuan Chiang

    Full Text Available To achieve effective intracellular anticancer drug delivery, the polymeric vesicles supplemented with the pH-responsive outlayered gels as a delivery system of doxorubicin (DOX were developed from self-assembly of the lipid/polypeptide adduct, distearin grafted poly(γ-glutamic acid (poly(γ-GA, followed by sequential deposition of chitosan and poly(γ-GA-co-γ-glutamyl oxysuccinimide-g-monomethoxy poly(ethylene glycol in combination with in situ covalent cross-linking on assembly surfaces. The resultant gel-caged polymeric vesicles (GCPVs showed superior performance in regulating drug release in response to the external pH change. Under typical physiological conditions (pH 7.4 and 37 °C at which the γ-GA/DOX ionic pairings remained mostly undisturbed, the dense outlayered gels of GCPVs significantly reduced the premature leakage of the uncomplexed payload. With the environmental pH being reduced from pH 7.4 to 4.7, the drug liberation was appreciably promoted by the massive disruption of the ionic γ-GA/DOX complexes along with the significant swelling of nanogel layers upon the increased protonation of chitosan chain segments. After being internalized by HeLa cells via endocytosis, GCPVs exhibited cytotoxic effect comparable to free DOX achieved by rapidly releasing the payload in intracellular acidic endosomes and lysosomes. This strongly implies the great promise of such unique GCPVs as an intracellular drug delivery carrier for potential anticancer treatment.

  14. Six-band terahertz metamaterial absorber based on the combination of multiple-order responses of metallic patches in a dual-layer stacked resonance structure

    Science.gov (United States)

    Wang, Ben-Xin; Wang, Gui-Zhen; Sang, Tian; Wang, Ling-Ling

    2017-01-01

    This paper reports on a numerical study of the six-band metamaterial absorber composed of two alternating stack of metallic-dielectric layers on top of a continuous metallic plane. Six obvious resonance peaks with high absorption performance (average larger than 99.37%) are realized. The first, third, fifth, and the second, fourth, sixth resonance absorption bands are attributed to the multiple-order responses (i.e., the 1-, 3- and 5-order responses) of the bottom- and top-layer of the structure, respectively, and thus the absorption mechanism of six-band absorber is due to the combination of two sets of the multiple-order resonances of these two layers. Besides, the size changes of the metallic layers have the ability to tune the frequencies of the six-band absorber. Employing the results, we also present a six-band polarization tunable absorber through varying the sizes of the structure in two orthogonal polarization directions. Moreover, nine-band terahertz absorber can be achieved by using a three-layer stacked structure. Simulation results indicate that the absorber possesses nine distinct resonance bands, and average absorptivities of them are larger than 94.03%. The six-band or nine-band absorbers obtained here have potential applications in many optoelectronic and engineering technology areas. PMID:28120897

  15. Vehicle Dynamics and Control

    CERN Document Server

    Rajamani, Rajesh

    2012-01-01

    Vehicle Dynamics and Control provides a comprehensive coverage of vehicle control systems and the dynamic models used in the development of these control systems. The control system applications covered in the book include cruise control, adaptive cruise control, ABS, automated lane keeping, automated highway systems, yaw stability control, engine control, passive, active and semi-active suspensions, tire-road friction coefficient estimation, rollover prevention, and hybrid electric vehicle. In developing the dynamic model for each application, an effort is made to both keep the model simple enough for control system design but at the same time rich enough to capture the essential features of the dynamics. A special effort has been made to explain the several different tire models commonly used in literature and to interpret them physically. In the second edition of the book, chapters on roll dynamics, rollover prevention and hybrid electric vehicles have been added, and the chapter on electronic stability co...

  16. Nonlinear dynamics of structures

    CERN Document Server

    Oller, Sergio

    2014-01-01

    This book lays the foundation of knowledge that will allow a better understanding of nonlinear phenomena that occur in structural dynamics.   This work is intended for graduate engineering students who want to expand their knowledge on the dynamic behavior of structures, specifically in the nonlinear field, by presenting the basis of dynamic balance in non‐linear behavior structures due to the material and kinematics mechanical effects.   Particularly, this publication shows the solution of the equation of dynamic equilibrium for structure with nonlinear time‐independent materials (plasticity, damage and frequencies evolution), as well as those time dependent non‐linear behavior materials (viscoelasticity and viscoplasticity). The convergence conditions for the non‐linear dynamic structure solution  are studied, and the theoretical concepts and its programming algorithms are presented.  

  17. Financial market dynamics

    Science.gov (United States)

    Michael, Fredrick; Johnson, M. D.

    2003-03-01

    A necessary precondition for modeling financial markets is a complete understanding of their statistics, including dynamics. Distributions derived from nonextensive Tsallis statistics are closely connected with dynamics described by a nonlinear Fokker-Planck equation. The combination shows promise in describing stochastic processes with power-law distributions and superdiffusive dynamics. We investigate intra-day price changes in the S& P500 stock index within this framework. We find that the power-law tails of the distributions, and the index's anomalously diffusing dynamics, are very accurately described by this approach. Our results show good agreement between market data and Fokker-Planck dynamics. This approach may be applicable in any anomalously diffusing system in which the correlations in time can be accounted for by an Ito-Langevin process with a simple time-dependent diffusion coefficient.

  18. Dynamic fracture mechanics

    Science.gov (United States)

    Kobayashi, A. S.; Ramulu, M.

    1985-01-01

    Dynamic fracture and crack propagation concepts for ductile materials are reviewed. The equations for calculating dynamic stress integrity and the dynamic energy release rate in order to study dynamic crack propagation are provided. The stress intensity factor versus crack velocity relation is investigated. The uses of optical experimental techniques and finite element methods for fracture analyses are described. The fracture criteria for a rapidly propagating crack under mixed mode conditions are discussed; crack extension and fracture criteria under combined tension and shear loading are based on maximum circumferential stress or energy criteria such as strain energy density. The development and use of a Dugdale model and finite element models to represent crack and fracture dynamics are examined.

  19. Dynamics of aesthetic appreciation

    Science.gov (United States)

    Carbon, Claus-Christian

    2012-03-01

    Aesthetic appreciation is a complex cognitive processing with inherent aspects of cold as well as hot cognition. Research from the last decades of empirical has shown that evaluations of aesthetic appreciation are highly reliable. Most frequently, facial attractiveness was used as the corner case for investigating aesthetic appreciation. Evaluating facial attractiveness shows indeed high internal consistencies and impressively high inter-rater reliabilities, even across cultures. Although this indicates general and stable mechanisms underlying aesthetic appreciation, it is also obvious that our taste for specific objects changes dynamically. Aesthetic appreciation on artificial object categories, such as fashion, design or art is inherently very dynamic. Gaining insights into the cognitive mechanisms that trigger and enable corresponding changes of aesthetic appreciation is of particular interest for research as this will provide possibilities to modeling aesthetic appreciation for longer durations and from a dynamic perspective. The present paper refers to a recent two-step model ("the dynamical two-step-model of aesthetic appreciation"), dynamically adapting itself, which accounts for typical dynamics of aesthetic appreciation found in different research areas such as art history, philosophy and psychology. The first step assumes singular creative sources creating and establishing innovative material towards which, in a second step, people adapt by integrating it into their visual habits. This inherently leads to dynamic changes of the beholders' aesthetic appreciation.

  20. From Molecular Dynamics to Brownian Dynamics

    CERN Document Server

    Erban, Radek

    2014-01-01

    Three coarse-grained molecular dynamics (MD) models are investigated with the aim of developing and analyzing multiscale methods which use MD simulations in parts of the computational domain and (less detailed) Brownian dynamics (BD) simulations in the remainder of the domain. The first MD model is formulated in one spatial dimension. It is based on elastic collisions of heavy molecules (e.g. proteins) with light point particles (e.g. water molecules). Two three-dimensional MD models are then investigated. The obtained results are applied to a simplified model of protein binding to receptors on the cellular membrane. It is shown that modern BD simulators of intracellular processes can be used in the bulk and accurately coupled with a (more detailed) MD model of protein binding which is used close to the membrane.

  1. Dynamic Recrystallization: The Dynamic Deformation Regime

    Science.gov (United States)

    Murr, L. E.; Pizaña, C.

    2007-11-01

    Severe plastic deformation (PD), especially involving high strain rates (>103 s 1), occurs through solid-state flow, which is accommodated by dynamic recrystallization (DRX), either in a continuous or discontinuous mode. This flow can be localized in shear instability zones (or adiabatic shear bands (ASBs)) with dimensions smaller than 5 μ, or can include large volumes with flow zone dimensions exceeding centimeters. This article illustrates these microstructural features using optical and electron metallography to examine a host of dynamic deformation examples: shaped charge jet formation, high-velocity and hypervelocity impact crater formation, rod penetration into thick targets (which includes rod and target DRX flow and mixing), large projectile-induced target plug formation and failure, explosive welding, and friction-stir welding and processing. The DRX is shown to be a universal mechanism that accommodates solid-state flow in extreme (or severe) PD regimes.

  2. Fundamentals of gas dynamics

    CERN Document Server

    Babu, V

    2014-01-01

    Fundamentals of Gas Dynamics, Second Edition isa comprehensively updated new edition and now includes a chapter on the gas dynamics of steam. It covers the fundamental concepts and governing equations of different flows, and includes end of chapter exercises based on the practical applications. A number of useful tables on the thermodynamic properties of steam are also included.Fundamentals of Gas Dynamics, Second Edition begins with an introduction to compressible and incompressible flows before covering the fundamentals of one dimensional flows and normal shock wav

  3. The dynamics of leadership

    Directory of Open Access Journals (Sweden)

    C. J. A. Vos

    2002-08-01

    Full Text Available The dynamics of leadership This article reflects on the need for dynamic leadership. An organisation'sfunctionality is dependent on the intellectual, emotional andphysical energy which the people involved in the organisation arewilling to contribute. The process of energy release is determined mainlyby two concepts: vision and mission. A vision is inextricably linked to astrategy. Leadership plays an essential part in the realisation of anorganisation's vision and mission. In this article different leadershipmodels are discussed. Autocratic leadership is critically analysed.Dynamic leadership, which encompasses inspirational and imaginativeleadership is discussed. The community of faith and society both have alife-long need for inspirational leadership.

  4. Shadowing in dynamical systems

    CERN Document Server

    Pilyugin, Sergei Yu

    1999-01-01

    This book is an introduction to the theory of shadowing of approximate trajectories in dynamical systems by exact ones. This is the first book completely devoted to the theory of shadowing. It shows the importance of shadowing theory for both the qualitative theory of dynamical systems and the theory of numerical methods. Shadowing Methods allow us to estimate differences between exact and approximate solutions on infinite time intervals and to understand the influence of error terms. The book is intended for specialists in dynamical systems, for researchers and graduate students in the theory of numerical methods.

  5. Stability of dynamical systems

    CERN Document Server

    Liao, Xiaoxin; Yu, P 0

    2007-01-01

    The main purpose of developing stability theory is to examine dynamic responses of a system to disturbances as the time approaches infinity. It has been and still is the object of intense investigations due to its intrinsic interest and its relevance to all practical systems in engineering, finance, natural science and social science. This monograph provides some state-of-the-art expositions of major advances in fundamental stability theories and methods for dynamic systems of ODE and DDE types and in limit cycle, normal form and Hopf bifurcation control of nonlinear dynamic systems.ʺ Presents

  6. Elements of analytical dynamics

    CERN Document Server

    Kurth, Rudolph; Stark, M

    1976-01-01

    Elements of Analytical Dynamics deals with dynamics, which studies the relationship between motion of material bodies and the forces acting on them. This book is a compilation of lectures given by the author at the Georgia and Institute of Technology and formed a part of a course in Topological Dynamics. The book begins by discussing the notions of space and time and their basic properties. It then discusses the Hamilton-Jacobi theory and Hamilton's principle and first integrals. The text concludes with a discussion on Jacobi's geometric interpretation of conservative systems. This book will

  7. Real estate investment dynamics

    OpenAIRE

    Gruber, Johannes

    2010-01-01

    This thesis is motivated by the steadily increasing interest in the dynamic relationship between the macro-economy and the real estate sector. One of the main issues in this respect is to study the investment dynamics. Since the bursting of the U.S. housing bubble in 2006 is identified as the point of origin of the so called subprime crises, which led to the collapse of the U.S. financial system, the dynamics of real estate investments is of particular interest. In the first part of my the...

  8. High enthalpy gas dynamics

    CERN Document Server

    Rathakrishnan, Ethirajan

    2014-01-01

    This is an introductory level textbook which explains the elements of high temperature and high-speed gas dynamics. written in a clear and easy to follow style, the author covers all the latest developments in the field including basic thermodynamic principles, compressible flow regimes and waves propagation in one volume covers theoretical modeling of High Enthalpy Flows, with particular focus on problems in internal and external gas-dynamic flows, of interest in the fields of rockets propulsion and hypersonic aerodynamics High enthalpy gas dynamics is a compulsory course for aerospace engine

  9. Basic structural dynamics

    CERN Document Server

    Anderson, James C

    2012-01-01

    A concise introduction to structural dynamics and earthquake engineering Basic Structural Dynamics serves as a fundamental introduction to the topic of structural dynamics. Covering single and multiple-degree-of-freedom systems while providing an introduction to earthquake engineering, the book keeps the coverage succinct and on topic at a level that is appropriate for undergraduate and graduate students. Through dozens of worked examples based on actual structures, it also introduces readers to MATLAB, a powerful software for solving both simple and complex structural d

  10. Recovery of dynamic interference

    CERN Document Server

    Baghery, Mehrdad; Rost, Jan M

    2016-01-01

    We develop general quantitative criteria for dynamic interference, a manifestation of double-slit interference in time which should be realizable with brilliant state-of-the-art high-frequency laser sources. Our analysis reveals that the observation of dynamic interference hinges upon maximizing the difference between the dynamic polarization of the initial bound and the final continuum state of the electron during the light pulse, while keeping depletion of the initial state small. Confirmed by numerical results, we predict that this is impossible for the hydrogen ground-state but feasible with excited states explicitly exemplified with the hydrogen 2p-state.

  11. Theoretical Fluid Dynamics

    CERN Document Server

    Shivamoggi, Bhimsen K

    1998-01-01

    "Although there are many texts and monographs on fluid dynamics, I do not know of any which is as comprehensive as the present book. It surveys nearly the entire field of classical fluid dynamics in an advanced, compact, and clear manner, and discusses the various conceptual and analytical models of fluid flow." - Foundations of Physics on the first edition. Theoretical Fluid Dynamics functions equally well as a graduate-level text and a professional reference. Steering a middle course between the empiricism of engineering and the abstractions of pure mathematics, the author focuses

  12. Discrete Dynamics Lab

    Science.gov (United States)

    Wuensche, Andrew

    DDLab is interactive graphics software for creating, visualizing, and analyzing many aspects of Cellular Automata, Random Boolean Networks, and Discrete Dynamical Networks in general and studying their behavior, both from the time-series perspective — space-time patterns, and from the state-space perspective — attractor basins. DDLab is relevant to research, applications, and education in the fields of complexity, self-organization, emergent phenomena, chaos, collision-based computing, neural networks, content addressable memory, genetic regulatory networks, dynamical encryption, generative art and music, and the study of the abstract mathematical/physical/dynamical phenomena in their own right.

  13. Thermofield dynamics and Gravity

    CERN Document Server

    Nair, V P

    2015-01-01

    Thermofield dynamics is presented in terms of a path-integral using coherent states, equivalently, using a coadjoint orbit action. A field theoretic formulation in terms of fields on a manifold ${\\mathcal M} \\times {\\tilde{\\mathcal M}}$ where the two components have opposite orientation is also presented. We propose formulating gravitational dynamics for noncommutative geometry using thermofield dynamics, doubling the Hilbert space modeling the noncommutative space. We consider 2+1 dimensions in some detail and since ${\\mathcal M}$ and ${\\tilde{\\mathcal M}}$ have opposite orientation, the commutative limit leads to the Einstein-Hilbert action as the difference of two Chern-Simons actions.

  14. Dynamics of Tectonic Plates

    CERN Document Server

    Pechersky, E; Sadowski, G; Yambartsev, A

    2014-01-01

    We suggest a model that describes a mutual dynamic of tectonic plates. The dynamic is a sort of stick-slip one which is modeled by a Markov random process. The process defines a microlevel of the dynamic. A macrolevel is obtained by a scaling limit which leads to a system of integro-differential equations which determines a kind of mean field systems. Conditions when Gutenberg-Richter empirical law are presented on the mean field level. These conditions are rather universal and do not depend on features of resistant forces.

  15. Dynamics of Tectonic Plates

    OpenAIRE

    2014-01-01

    We suggest a model that describes a mutual dynamic of tectonic plates. The dynamic is a sort of stick-slip one which is modeled by a Markov random process. The process defines a microlevel of the dynamic. A macrolevel is obtained by a scaling limit which leads to a system of integro-differential equations which determines a kind of mean field systems. Conditions when Gutenberg-Richter empirical law are presented on the mean field level. These conditions are rather universal and do not depend ...

  16. Fluid dynamics transactions

    CERN Document Server

    Fiszdon, W

    1965-01-01

    Fluid Dynamics Transactions, Volume 2 compiles 46 papers on fluid dynamics, a subdiscipline of fluid mechanics that deals with fluid flow. The topics discussed in this book include developments in interference theory for aeronautical applications; diffusion from sources in a turbulent boundary layer; unsteady motion of a finite wing span in a compressible medium; and wall pressure covariance and comparison with experiment. The certain classes of non-stationary axially symmetric flows in magneto-gas-dynamics; description of the phenomenon of secondary flows in curved channels by means of co

  17. Process Fairness and Dynamic Consistency

    NARCIS (Netherlands)

    S.T. Trautmann (Stefan); P.P. Wakker (Peter)

    2010-01-01

    textabstractAbstract: When process fairness deviates from outcome fairness, dynamic inconsistencies can arise as in nonexpected utility. Resolute choice (Machina) can restore dynamic consistency under nonexpected utility without using Strotz's precommitment. It can similarly justify dynamically

  18. Chiral Gauge Dynamics and Dynamical Supersymmetry Breaking

    Energy Technology Data Exchange (ETDEWEB)

    Poppitz, Erich; /Toronto U.; Unsal, Mithat; /SLAC /Stanford U.

    2009-05-07

    We study the dynamics of a chiral SU(2) gauge theory with a Weyl fermion in the I = 3/2 representation and of its supersymmetric generalization. In the former, we find a new and exotic mechanism of confinement, induced by topological excitations that we refer to as magnetic quintets. The supersymmetric version was examined earlier in the context of dynamical supersymmetry breaking by Intriligator, Seiberg, and Shenker, who showed that if this gauge theory confines at the origin of moduli space, one may break supersymmetry by adding a tree level superpotential. We examine the dynamics by deforming the theory on S{sup 1} x R{sup 3}, and show that the infrared behavior of this theory is an interacting CFT at small S{sup 1}. We argue that this continues to hold at large S{sup 1}, and if so, that supersymmetry must remain unbroken. Our methods also provide the microscopic origin of various superpotentials in SQCD on S{sup 1} x R{sup 3}--which were previously obtained by using symmetry and holomorphy--and resolve a long standing interpretational puzzle concerning a flux operator discovered by Affleck, Harvey, and Witten. It is generated by a topological excitation, a 'magnetic bion', whose stability is due to fermion pair exchange between its constituents. We also briefly comment on composite monopole operators as leading effects in two dimensional antiferromagnets.

  19. Assimilation Dynamic Network (ADN) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Assimilation Dynamic Network (ADN) is a dynamic inter-processor communication network that spans heterogeneous processor architectures, unifying components,...

  20. 基于两种瓶颈度的制造车间多瓶颈动态预测方法%Dynamic Prediction Method of Multi-bottleneck in Manufacturing Shop Based on Two Bottleneck Degrees

    Institute of Scientific and Technical Information of China (English)

    刘志; 蒋增强; 龚本刚

    2014-01-01

    针对制造车间多瓶颈预测问题,提出一种基于两种瓶颈度的多瓶颈动态预测方法,以在合理认定瓶颈责任的前提下实现系统多瓶颈的连续准确预测。首先,建立综合瓶颈度和独立瓶颈度的概念模型,并以时间、质量和成本为参数,构建其数学模型;然后,构建包含多瓶颈双层预测机制、瓶颈多态性分析和瓶颈指数迭代预测模型的多瓶颈动态预测方法;最后,将多瓶颈动态预测方法、单瓶颈度法和PBM 法运用至某汽车产品总装线,以验证该方法有效性。%Aiming at the prediction problem of multi-bottleneck in complex manufacturing shop , a dynamic prediction method of multi-bottleneck was proposed based on two bottleneck degrees ,which can forecast bottleneck accurately under conditions that bottleneck responsibility was verified reasona-bly .Firstly ,conceptual models about general bottleneck degree and independent bottleneck degree were built ,and then taking time ,quality and cost as parameters ,their mathematical models were es-tablished .Secondly ,one dynamic prediction method of multi-bottleneck was come up with ,which con-tained dual-layer multi-bottleneck prediction mechanism ,bottleneck polymorphism analysis and the it-erative prediction of bottleneck index .Finally ,it is proved to be superior and credible by comparison to the method of single bottleneck degree and the method of PBM for production bottleneck prediction problem of one vehicle assembly line .

  1. Dynamic Boolean Mathematics

    Science.gov (United States)

    Bossé, Michael J.; Adu-Gyamfi, Kwaku; Chandler, Kayla; Lynch-Davis, Kathleen

    2016-01-01

    Dynamic mathematical environments allow users to reify mathematical concepts through multiple representations, transform mathematical relations and organically explore mathematical properties, investigate integrated mathematics, and develop conceptual understanding. Herein, we integrate Boolean algebra, the functionalities of a dynamic…

  2. Dynamic plasmonic colour display

    Science.gov (United States)

    Duan, Xiaoyang; Kamin, Simon; Liu, Na

    2017-02-01

    Plasmonic colour printing based on engineered metasurfaces has revolutionized colour display science due to its unprecedented subwavelength resolution and high-density optical data storage. However, advanced plasmonic displays with novel functionalities including dynamic multicolour printing, animations, and highly secure encryption have remained in their infancy. Here we demonstrate a dynamic plasmonic colour display technique that enables all the aforementioned functionalities using catalytic magnesium metasurfaces. Controlled hydrogenation and dehydrogenation of the constituent magnesium nanoparticles, which serve as dynamic pixels, allow for plasmonic colour printing, tuning, erasing and restoration of colour. Different dynamic pixels feature distinct colour transformation kinetics, enabling plasmonic animations. Through smart material processing, information encoded on selected pixels, which are indiscernible to both optical and scanning electron microscopies, can only be read out using hydrogen as a decoding key, suggesting a new generation of information encryption and anti-counterfeiting applications.

  3. Ansatz for dynamical hierarchies

    DEFF Research Database (Denmark)

    Rasmussen, S.; Baas, N.A.; Mayer, B.

    2001-01-01

    Complex, robust functionalities can be generated naturally in at least two ways: by the assembly of structures and by the evolution of structures. This work is concerned with spontaneous formation of structures. We define the notion of dynamical hierarchies in natural systems and show...... the importance of this particular kind of organization for living systems. We then define a framework that enables us to formulate, investigate, and manipulate such dynamical hierarchies. This framework allows us to simultaneously investigate different levels of description together with them interrelationship...... three. Formulating this system as a simple two-dimensional molecular dynamics (MD) lattice gas allows us within one dynamical system to demonstrate the successive emergence of two higher levels (three levels all together) of robust structures with associated properties. Second, we demonstrate how...

  4. The Dynamics of Standardization

    DEFF Research Database (Denmark)

    Brunsson, Nils; Rasche, Andreas; Seidl, David

    2012-01-01

    This paper suggests that when the phenomenon of standards and standardization is examined from the perspective of organization studies, three aspects stand out: the standardization of organizations, standardization by organizations and standardization as (a form of) organization. Following......, and show that, while standards and standardization are typically associated with stability and sameness, they are essentially a dynamic phenomenon. The paper highlights the contributions of this special issue to the topic of standards as a dynamic phenomenon in organization studies and makes suggestions...... a comprehensive overview of existing research in these three areas, we argue that the dynamic aspects of standardization are under-represented in the scholarly discourse. Furthermore, we identify the main types of tension associated with standardization and the dynamics they generate in each of those three areas...

  5. Transonic Dynamics Tunnel (TDT)

    Data.gov (United States)

    Federal Laboratory Consortium — The Transonic Dynamics Tunnel (TDT) is a continuous flow wind-tunnel facility capable of speeds up to Mach 1.2 at stagnation pressures up to one atmosphere. The TDT...

  6. Market Squid Population Dynamics

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains population dynamics data on paralarvae, juvenile and adult market squid collected off California and the US Pacific Northwest. These data were...

  7. Network-behavior dynamics

    NARCIS (Netherlands)

    Veenstra, René; Dijkstra, Jan; Steglich, Christian; Van Zalk, Maarten H. W.

    2013-01-01

    Researchers have become increasingly interested in disentangling selection and influence processes. This literature review provides context for the special issue on network-behavior dynamics. It brings together important conceptual, methodological, and empirical contributions focusing on longitudina

  8. Fractional Dynamical Systems

    CERN Document Server

    Edelman, Mark

    2014-01-01

    In this paper the author presents the results of the preliminary investigation of fractional dynamical systems based on the results of numerical simulations of fractional maps. Fractional maps are equivalent to fractional differential equations describing systems experiencing periodic kicks. Their properties depend on the value of two parameters: the non-linearity parameter, which arises from the corresponding regular dynamical systems; and the memory parameter which is the order of the fractional derivative in the corresponding non-linear fractional differential equations. The examples of the fractional Standard and Logistic maps demonstrate that phase space of non-linear fractional dynamical systems may contain periodic sinks, attracting slow diverging trajectories, attracting accelerator mode trajectories, chaotic attractors, and cascade of bifurcations type trajectories whose properties are different from properties of attractors in regular dynamical systems. The author argues that discovered properties s...

  9. Gun Dynamics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Gun Dynamics Laboratory is a research multi-task facility, which includes two firing bays, a high bay area and a second floor laboratory space. The high bay area...

  10. Discrete dynamical models

    CERN Document Server

    Salinelli, Ernesto

    2014-01-01

    This book provides an introduction to the analysis of discrete dynamical systems. The content is presented by an unitary approach that blends the perspective of mathematical modeling together with the ones of several discipline as Mathematical Analysis, Linear Algebra, Numerical Analysis, Systems Theory and Probability. After a preliminary discussion of several models, the main tools for the study of linear and non-linear scalar dynamical systems are presented, paying particular attention to the stability analysis. Linear difference equations are studied in detail and an elementary introduction of Z and Discrete Fourier Transform is presented. A whole chapter is devoted to the study of bifurcations and chaotic dynamics. One-step vector-valued dynamical systems are the subject of three chapters, where the reader can find the applications to positive systems, Markov chains, networks and search engines. The book is addressed mainly to students in Mathematics, Engineering, Physics, Chemistry, Biology and Economic...

  11. Invitation to dynamical systems

    CERN Document Server

    Scheinerman, Edward R

    2012-01-01

    This text is designed for those who wish to study mathematics beyond linear algebra but are unready for abstract material. Rather than a theorem-proof-corollary exposition, it stresses geometry, intuition, and dynamical systems. 1996 edition.

  12. Polymer Fluid Dynamics.

    Science.gov (United States)

    Bird, R. Byron

    1980-01-01

    Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)

  13. Causal graph dynamics

    CERN Document Server

    Arrighi, Pablo

    2012-01-01

    We generalize the theory of Cellular Automata to arbitrary, time-varying graphs. In other words we formalize, and prove theorems about, the intuitive idea of a labelled graph which evolves in time - but under the natural constraint that information can only ever be transmitted at a bounded speed, with respect to the distance given by the graph. The notion of translation-invariance is also generalized. The definition we provide for these `causal graph dynamics' is simple and axiomatic. The theorems we provide also show that it is robust. For instance, causal graph dynamics are stable under composition and under restriction to radius one. In the finite case some fundamental facts of Cellular Automata theory carry through: causal graph dynamics admit a characterization as continuous functions and they are stable under inversion. The provided examples suggest a wide range of applications of this mathematical object, from complex systems science to theoretical physics. Keywords: Dynamical networks, Boolean network...

  14. Discrete Wigner function dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Klimov, A B; Munoz, C [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410, Guadalajara, Jalisco (Mexico)

    2005-12-01

    We study the evolution of the discrete Wigner function for prime and the power of prime dimensions using the discrete version of the star-product operation. Exact and semiclassical dynamics in the limit of large dimensions are considered.

  15. Advances in soil dynamics

    DEFF Research Database (Denmark)

    Advances in Soil Dynamics, Volume 3, represents the culmination of the work undertaken by the Advances in Soil Dynamics Monograph Committee, PM-45-01, about 15 years ago to summarize important developments in this field over the last 35 years. When this project was initiated, the main goal...... was to abridge major strides made in the general area of soil dynamics during the sixties, seventies, and eighties. However, by about the mid-nineties soil dynamics research in the US and much of the developed world had come to a virtual standstill. Although significant progress was made prior to the mid......-nineties, we still do not have a sound fundamental knowledge of soil-machine and soil-plant interactions. It is the hope of the editors that these three volumes will provide a ready reference for much needed future research in this area....

  16. Advances in soil dynamics

    DEFF Research Database (Denmark)

    Advances in Soil Dynamics, Volume 3, represents the culmination of the work undertaken by the Advances in Soil Dynamics Monograph Committee, PM-45-01, about 15 years ago to summarize important developments in this field over the last 35 years. When this project was initiated, the main goal...... was to abridge major strides made in the general area of soil dynamics during the sixties, seventies, and eighties. However, by about the mid-nineties soil dynamics research in the US and much of the developed world had come to a virtual standstill. Although significant progress was made prior to the mid......-nineties, we still do not have a sound fundamental knowledge of soil-machine and soil-plant interactions. It is the hope of the editors that these three volumes will provide a ready reference for much needed future research in this area....

  17. ON PERIODIC DYNAMICAL SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    LU WENLIAN; CHEN TIANPING

    2004-01-01

    The authors investigate the existence and the global stability of periodic solution for dynamical systems with periodic interconnections, inputs and self-inhibitions. The model is very general, the conditions are quite weak and the results obtained are universal.

  18. Stochastic dynamics and irreversibility

    CERN Document Server

    Tomé, Tânia

    2015-01-01

    This textbook presents an exposition of stochastic dynamics and irreversibility. It comprises the principles of probability theory and the stochastic dynamics in continuous spaces, described by Langevin and Fokker-Planck equations, and in discrete spaces, described by Markov chains and master equations. Special concern is given to the study of irreversibility, both in systems that evolve to equilibrium and in nonequilibrium stationary states. Attention is also given to the study of models displaying phase transitions and critical phenomema both in thermodynamic equilibrium and out of equilibrium. These models include the linear Glauber model, the Glauber-Ising model, lattice models with absorbing states such as the contact process and those used in population dynamic and spreading of epidemic, probabilistic cellular automata, reaction-diffusion processes, random sequential adsorption and dynamic percolation. A stochastic approach to chemical reaction is also presented.The textbook is intended for students of ...

  19. Supervision and group dynamics

    DEFF Research Database (Denmark)

    Hansen, Søren; Jensen, Lars Peter

    2004-01-01

    as well as at Aalborg University. The first visible result has been participating supervisors telling us that the course has inspired them to try supervising group dynamics in the future. This paper will explore some aspects of supervising group dynamics as well as, how to develop the Aalborg model...... An important aspect of the problem based and project organized study at Aalborg University is the supervision of the project groups. At the basic education (first year) it is stated in the curriculum that part of the supervisors' job is to deal with group dynamics. This is due to the experience...... that many students are having difficulties with practical issues such as collaboration, communication, and project management. Most supervisors either ignore this demand, because they do not find it important or they find it frustrating, because they do not know, how to supervise group dynamics...

  20. Nonequilibrium molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hoover, W.G. (California Univ., Davis, CA (USA). Dept. of Applied Science Lawrence Livermore National Lab., CA (USA))

    1990-11-01

    The development of nonequilibrium molecular dynamics is described, with emphasis on massively-parallel simulations involving the motion of millions, soon to be billions, of atoms. Corresponding continuum simulations are also discussed. 14 refs., 8 figs.

  1. Dynamic Stage Design

    Institute of Scientific and Technical Information of China (English)

    Florian von Hofen[GER

    2013-01-01

    Concepts and methods for dynamic stage designs were introduced ranging from different ifelds of TV live shows, exhibitions and theatre performances, and a special emphasis was put on solution to the theatre stage design.

  2. Dynamic performance management system

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An integrated, efficient and effective performance management system, "dynamic performance management system", is presented, which covers the entire performance management process including measures design, analysis, and dynamic update. The analysis of performance measures using causal loop diagrams, qualitative inference and analytic network process is mainly discussed. A real world case study is carried out throughout the paper to explain how the framework works. A software tool for DPMS, Performance Analyzer, is also introduced.

  3. Photochemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

    1993-12-01

    The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

  4. Dynamics in artifact ecologies

    DEFF Research Database (Denmark)

    Bødker, Susanne; Klokmose, Clemens Nylandsted

    2012-01-01

    We increasingly interact with multiple interactive artifacts with overlapping capabilities during our daily activities. It has previously been shown that the use of an interactive artifact cannot be understood in isolation, but artifacts must be understood as part of an artifact ecology, where ar...... in artifact ecologies cannot be understood as static, instead they evolve dynamically over time. We provide activity theory-based concepts to explain these dynamics....

  5. Dynamics of curved fronts

    CERN Document Server

    Pelce, Pierre

    1989-01-01

    In recent years, much progress has been made in the understanding of interface dynamics of various systems: hydrodynamics, crystal growth, chemical reactions, and combustion. Dynamics of Curved Fronts is an important contribution to this field and will be an indispensable reference work for researchers and graduate students in physics, applied mathematics, and chemical engineering. The book consist of a 100 page introduction by the editor and 33 seminal articles from various disciplines.

  6. Dynamics of Soft Matter

    CERN Document Server

    García Sakai, Victoria; Chen, Sow-Hsin

    2012-01-01

    Dynamics of Soft Matter: Neutron Applications provides an overview of neutron scattering techniques that measure temporal and spatial correlations simultaneously, at the microscopic and/or mesoscopic scale. These techniques offer answers to new questions arising at the interface of physics, chemistry, and biology. Knowledge of the dynamics at these levels is crucial to understanding the soft matter field, which includes colloids, polymers, membranes, biological macromolecules, foams, emulsions towards biological & biomimetic systems, and phenomena involving wetting, friction, adhesion, or micr

  7. Dynamically Generated $\\Xi (1690)$

    CERN Document Server

    Sekihara, Takayasu

    2016-01-01

    We show that the $\\Xi (1690)$ resonance can be dynamically generated in the $s$-wave $\\bar{K} \\Sigma$-$\\bar{K} \\Lambda$-$\\pi \\Xi$-$\\eta \\Xi$ coupled-channels chiral unitary approach. In our model, the $\\Xi (1690)$ resonance appears near the $\\bar{K} \\Sigma$ threshold as a $\\bar{K} \\Sigma$ molecular state and the experimental data are reproduced well. We discuss properties of the dynamically generated $\\Xi (1690)$.

  8. Nonuniversality in level dynamics

    CERN Document Server

    Kunstman, P; Zakrzewski, J A; Kunstman, Pawe{\\l}; Zyczkowski, Karol \\.; Zakrzewski, Jakub

    1997-01-01

    Statistical properties of parametric motion in ensembles of Hermitian banded random matrices are studied. We analyze the distribution of level velocities and level curvatures as well as their correlation functions in the crossover regime between three universality classes. It is shown that the statistical properties of level dynamics are in general non-universal and strongly depend on the way in which the parametric dynamics is introduced.

  9. Nonuniversality in level dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kunstman, P.; Zyczkowski, K.; Zakrzewski, J. [Instytut Fizyki Mariana Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland)

    1997-03-01

    Statistical properties of parametric motion in ensembles of Hermitian banded random matrices are studied. We analyze the distribution of level velocities and level curvatures as well as their correlation functions in the crossover regime between three universality classes. It is shown that the statistical properties of level dynamics are in general {ital nonuniversal} and strongly depend on the way in which the parametric dynamics is introduced. {copyright} {ital 1997} {ital The American Physical Society}

  10. Ocean Dynamics: Dynamo

    Science.gov (United States)

    2012-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Ocean Dynamics: Dynamo Robert Pinkel Marine Physical...execution of the Dynamo Leg IV Experiment in December 2011. Our objective was to document the development of the diurnal surface layer and its...2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Ocean Dynamics: Dynamo 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  11. Chaotic dynamics with Maxima

    OpenAIRE

    2013-01-01

    We present an introduction to the study of chaos in discrete and continuous dynamical systems using the CAS Maxima. These notes are intended to cover the standard topics and techniques: discrete and continuous logistic equation to model growth population, staircase plots, bifurcation diagrams and chaos transition, nonlinear continuous dynamics (Lorentz system and Duffing oscillator), Lyapunov exponents, Poincar\\'e sections, fractal dimension and strange attractors. The distinctive feature her...

  12. Ocean Dynamics: Vietnam DRI

    Science.gov (United States)

    2014-09-30

    Dynamics: Vietnam DRI Robert Pinkel Marine Physical Laboratory Scripps Institution of Oceanography La Jolla California 92093-0213 Phone: (858) 534...DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Ocean Dynamics: Vietnam DRI 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM...cycle.. The Thorpe-scale estimates are local to Site III. South China Sea Process Cruise 2014 Under Vietnam DRI funding, Researcher Drew Lucas

  13. Dynamical quantum teleportation

    Energy Technology Data Exchange (ETDEWEB)

    Muschik, Christine [ICFO-Institut de Ciencies Fotoniques (Spain); Polzik, Eugene [Niels Bohr Institute (Denmark); Cirac, Ignacio [Max-Planck-Institute (Germany)

    2013-07-01

    We introduce two protocols for inducing non-local dynamics between two separate parties. The first scheme allows for the engineering of an interaction between the two remote systems, while the second protocol induces a dynamics in one of the parties, which is controlled by the other one. Both schemes apply to continuous variable systems, run continuously in time and are based on instantaneous feedback.

  14. Assimilating seizure dynamics.

    Directory of Open Access Journals (Sweden)

    Ghanim Ullah

    2010-05-01

    Full Text Available Observability of a dynamical system requires an understanding of its state-the collective values of its variables. However, existing techniques are too limited to measure all but a small fraction of the physical variables and parameters of neuronal networks. We constructed models of the biophysical properties of neuronal membrane, synaptic, and microenvironment dynamics, and incorporated them into a model-based predictor-controller framework from modern control theory. We demonstrate that it is now possible to meaningfully estimate the dynamics of small neuronal networks using as few as a single measured variable. Specifically, we assimilate noisy membrane potential measurements from individual hippocampal neurons to reconstruct the dynamics of networks of these cells, their extracellular microenvironment, and the activities of different neuronal types during seizures. We use reconstruction to account for unmeasured parts of the neuronal system, relating micro-domain metabolic processes to cellular excitability, and validate the reconstruction of cellular dynamical interactions against actual measurements. Data assimilation, the fusing of measurement with computational models, has significant potential to improve the way we observe and understand brain dynamics.

  15. Dynamic hardness of metals

    Science.gov (United States)

    Liang, Xuecheng

    Dynamic hardness (Pd) of 22 different pure metals and alloys having a wide range of elastic modulus, static hardness, and crystal structure were measured in a gas pulse system. The indentation contact diameter with an indenting sphere and the radius (r2) of curvature of the indentation were determined by the curve fitting of the indentation profile data. r 2 measured by the profilometer was compared with that calculated from Hertz equation in both dynamic and static conditions. The results indicated that the curvature change due to elastic recovery after unloading is approximately proportional to the parameters predicted by Hertz equation. However, r 2 is less than the radius of indenting sphere in many cases which is contradictory to Hertz analysis. This discrepancy is believed due to the difference between Hertzian and actual stress distributions underneath the indentation. Factors which influence indentation elastic recovery were also discussed. It was found that Tabor dynamic hardness formula always gives a lower value than that directly from dynamic hardness definition DeltaE/V because of errors mainly from Tabor's rebound equation and the assumption that dynamic hardness at the beginning of rebound process (Pr) is equal to kinetic energy change of an impact sphere over the formed crater volume (Pd) in the derivation process for Tabor's dynamic hardness formula. Experimental results also suggested that dynamic to static hardness ratio of a material is primarily determined by its crystal structure and static hardness. The effects of strain rate and temperature rise on this ratio were discussed. A vacuum rotating arm apparatus was built to measure Pd at 70, 127, and 381 mum sphere sizes, these results exhibited that Pd is highly depended on the sphere size due to the strain rate effects. P d was also used to substitute for static hardness to correlate with abrasion and erosion resistance of metals and alloys. The particle size effects observed in erosion were

  16. A HYBRID DYNAMIC PROGRAM SLICING

    Institute of Scientific and Technical Information of China (English)

    Yi Tong; Wu Fangjun

    2005-01-01

    This letter proposes a hybrid method for computing dynamic program slicing. The key element is to construct a Coverage-Testing-based Dynamic Dependence Graph (CTDDG),which makes use of both dynamic and static information to get execution status. The approach overcomes the limitations of previous dynamic slicing methods, which have to redo slicing if slice criterion changes.

  17. Dynamics in Epistasis Analysis.

    Science.gov (United States)

    Awdeh, Aseel; Phenix, Hilary; Kaern, Mads; Perkins, Theodore

    2017-01-16

    Finding regulatory relationships between genes, including the direction and nature of influence between them, is a fundamental challenge in the field of molecular genetics. One classical approach to this problem is epistasis analysis. Broadly speaking, epistasis analysis infers the regulatory relationships between a pair of genes in a genetic pathway by considering the patterns of change in an observable trait resulting from single and double deletion of genes. While classical epistasis analysis has yielded deep insights on numerous genetic pathways, it is not without limitations. Here, we explore the possibility of dynamic epistasis analysis, in which, in addition to performing genetic perturbations of a pathway, we drive the pathway by a time-varying upstream signal. We explore the theoretical power of dynamical epistasis analysis by conducting an identifiability analysis of Boolean models of genetic pathways, comparing static and dynamic approaches. We find that even relatively simple input dynamics greatly increases the power of epistasis analysis to discriminate alternative network structures. Further, we explore the question of experiment design, and show that a subset of short time-varying signals, which we call dynamic primitives, allow maximum discriminative power with a reduced number of experiments.

  18. Astrophysical fluid dynamics

    Science.gov (United States)

    Ogilvie, Gordon I.

    2016-06-01

    > These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is `frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, including shocks and other discontinuities, are discussed. The spherical blast wave resulting from a supernova, and involving a strong shock, is a classic problem that can be solved analytically. Steady solutions with spherical or axial symmetry reveal the physics of winds and jets from stars and discs. The linearized equations determine the oscillation modes of astrophysical bodies, as well as their stability and their response to tidal forcing.

  19. Semipredictable dynamical systems

    Science.gov (United States)

    García-Morales, Vladimir

    2016-10-01

    A new class of deterministic dynamical systems, termed semipredictable dynamical systems, is presented. The spatiotemporal evolution of these systems have both predictable and unpredictable traits, as found in natural complex systems. We prove a general result: The dynamics of any deterministic nonlinear cellular automaton (CA) with p possible dynamical states can be decomposed at each instant of time in a superposition of N layers involving p0, p1, …, pN - 1 dynamical states each, where the pk ∈ N , k ∈ [ 0 , N - 1 ] are divisors of p. If the divisors coincide with the prime factors of p this decomposition is unique. Conversely, we also prove that N CA working on symbols p0, p1, …, pN - 1 can be composed to create a graded CA rule with N different layers. We then show that, even when the full spatiotemporal evolution can be unpredictable, certain traits (layers) can exactly be predicted. We present explicit examples of such systems involving compositions of Wolfram's 256 elementary CA and a more complex CA rule acting on a neighborhood of two sites and 12 symbols and whose rule table corresponds to the smallest Moufang loop M12(S3, 2).

  20. Modeling dynamic swarms

    KAUST Repository

    Ghanem, Bernard

    2013-01-01

    This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal interdependency and stationarity, i.e., the motions are similar in any small spatiotemporal neighborhood. Examples of DS abound in nature, e.g., herds of animals and flocks of birds. To capture the local spatiotemporal properties of the DS, we present a probabilistic model that learns both the spatial layout of swarm elements (based on low-level image segmentation) and their joint dynamics that are modeled as linear transformations. To this end, a spatiotemporal neighborhood is associated with each swarm element, in which local stationarity is enforced both spatially and temporally. We assume that the prior on the swarm dynamics is distributed according to an MRF in both space and time. Embedding this model in a MAP framework, we iterate between learning the spatial layout of the swarm and its dynamics. We learn the swarm transformations using ICM, which iterates between estimating these transformations and updating their distribution in the spatiotemporal neighborhoods. We demonstrate the validity of our method by conducting experiments on real and synthetic video sequences. Real sequences of birds, geese, robot swarms, and pedestrians evaluate the applicability of our model to real world data. © 2012 Elsevier Inc. All rights reserved.

  1. Dynamic stiffness of suction caissons

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Liingaard, Morten; Andersen, Lars

    The purpose of this report is to evaluate the dynamic soil-structure interaction of suction caissons for offshore wind turbines. The investigation is limited to a determination of the vertical dynamic stiffness of suction caissons. The soil surrounding the foundation is homogenous with linear...... of the skirt length, Poisson's ratio and the ratio between soil stiffness and skirt stiffness. Finally the dynamic behaviour at high frequencies is investigated....... viscoelastic properties. The dynamic stiffness of the suction caisson is expressed by dimensionless frequency-dependent dynamic stiffness coefficients corresponding to the vertical degree of freedom. The dynamic stiffness coefficients for the foundations are evaluated by means of a dynamic three...

  2. System dynamics with interaction discontinuity

    CERN Document Server

    Luo, Albert C J

    2015-01-01

    This book describes system dynamics with discontinuity caused by system interactions and presents the theory of flow singularity and switchability at the boundary in discontinuous dynamical systems. Based on such a theory, the authors address dynamics and motion mechanism of engineering discontinuous systems due to interaction. Stability and bifurcations of fixed points in nonlinear discrete dynamical systems are presented, and mapping dynamics are developed for analytical predictions of periodic motions in engineering discontinuous dynamical systems. Ultimately, the book provides an alternative way to discuss the periodic and chaotic behaviors in discontinuous dynamical systems.

  3. Vehicle dynamics theory and application

    CERN Document Server

    Jazar, Reza N

    2017-01-01

    This intermediate textbook is appropriate for students in vehicle dynamics courses, in their last year of undergraduate study or their first year of graduate study. It is also appropriate for mechanical engineers, automotive engineers, and researchers in the area of vehicle dynamics for continuing education or as a reference. It addresses fundamental and advanced topics, and a basic knowledge of kinematics and dynamics, as well as numerical methods, is expected. The contents are kept at a theoretical-practical level, with a strong emphasis on application. This third edition has been reduced by 25%, to allow for coverage over one semester, as opposed to the previous edition that needed two semesters for coverage. The textbook is composed of four parts: Vehicle Motion: covers tire dynamics, forward vehicle dynamics, and driveline dynamics Vehicle Kinematics: covers applied kinematics, applied mechanisms, steering dynamics, and suspension mechanisms Vehicle Dynamics: covers applied dynamics, vehicle planar dynam...

  4. Conference on Multibody Dynamics

    CERN Document Server

    Multibody Dynamics : Computational Methods and Applications

    2014-01-01

    By having its origin in analytical and continuum mechanics, as well as in computer science and applied mathematics, multibody dynamics provides a basis for analysis and virtual prototyping of innovative applications in many fields of contemporary engineering. With the utilization of computational models and algorithms that classically belonged to different fields of applied science, multibody dynamics delivers reliable simulation platforms for diverse highly-developed industrial products such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, smart structures, biomechanical applications and nano-technologies. The chapters of this volume are based on the revised and extended versions of the selected scientific papers from amongst 255 original contributions that have been accepted to be presented within the program of the distinguished international ECCOMAS conference. It reflects state-of-the-art in the advances of multibody dynamics, providing excellent insight in the recen...

  5. Fractional Dynamics and Control

    CERN Document Server

    Machado, José; Luo, Albert

    2012-01-01

    Fractional Dynamics and Control provides a comprehensive overview of recent advances in the areas of nonlinear dynamics, vibration and control with analytical, numerical, and experimental results. This book provides an overview of recent discoveries in fractional control, delves into fractional variational principles and differential equations, and applies advanced techniques in fractional calculus to solving complicated mathematical and physical problems.Finally, this book also discusses the role that fractional order modeling can play in complex systems for engineering and science. Discusses how fractional dynamics and control can be used to solve nonlinear science and complexity issues Shows how fractional differential equations and models can be used to solve turbulence and wave equations in mechanics and gravity theories and Schrodinger’s equation  Presents factional relaxation modeling of dielectric materials and wave equations for dielectrics  Develops new methods for control and synchronization of...

  6. Complex dynamics in nanosystems.

    Science.gov (United States)

    Ni, Xuan; Ying, Lei; Lai, Ying-Cheng; Do, Younghae; Grebogi, Celso

    2013-05-01

    Complex dynamics associated with multistability have been studied extensively in the past but mostly for low-dimensional nonlinear dynamical systems. A question of fundamental interest is whether multistability can arise in high-dimensional physical systems. Motivated by the ever increasing widespread use of nanoscale systems, we investigate a prototypical class of nanoelectromechanical systems: electrostatically driven Si nanowires, mathematically described by a set of driven, nonlinear partial differential equations. We develop a computationally efficient algorithm to solve the equations. Our finding is that multistability and complicated structures of basins of attraction are common types of dynamics, and the latter can be attributed to extensive transient chaos. Implications of these phenomena to device operations are discussed.

  7. Dynamical laser spike processing

    CERN Document Server

    Shastri, Bhavin J; Tait, Alexander N; Rodriguez, Alejandro W; Wu, Ben; Prucnal, Paul R

    2015-01-01

    Novel materials and devices in photonics have the potential to revolutionize optical information processing, beyond conventional binary-logic approaches. Laser systems offer a rich repertoire of useful dynamical behaviors, including the excitable dynamics also found in the time-resolved "spiking" of neurons. Spiking reconciles the expressiveness and efficiency of analog processing with the robustness and scalability of digital processing. We demonstrate that graphene-coupled laser systems offer a unified low-level spike optical processing paradigm that goes well beyond previously studied laser dynamics. We show that this platform can simultaneously exhibit logic-level restoration, cascadability and input-output isolation---fundamental challenges in optical information processing. We also implement low-level spike-processing tasks that are critical for higher level processing: temporal pattern detection and stable recurrent memory. We study these properties in the context of a fiber laser system, but the addit...

  8. Dynamics of Paroxysmal Tachycardia

    Science.gov (United States)

    Glass, Leon

    2004-03-01

    Parosxysmal tachycardia refers to abnormally fast cardiac arrhythmias that suddenly start and stop. Paroxysmal tachycardias can occur in many regions of the heart and may be associated with many different mechanisms. In order to study paroxysmal tachycardias, we have analyzed tissue cultures of cells from embryonic chick heart that are imaged using calcium and voltage sensitive dyes. This model system displays a number of different types of dynamics including dynamics originating from pacemakers, triggered dynamics in which an excitation leads to the initiation of a sequence of waves originating from a single source, and spontaneously iniitiating and terminating rotating spiral waves. Theoretical models that include heterogeneity, spontaneous pacemaker activity, and fatigue or reduced excitability arising as a consequence of rapid excitation can be used to account for these behaviors.

  9. Dynamics of aerospace vehicles

    Science.gov (United States)

    Schmidt, David K.

    1991-01-01

    The focus of this research was to address the modeling, including model reduction, of flexible aerospace vehicles, with special emphasis on models used in dynamic analysis and/or guidance and control system design. In the modeling, it is critical that the key aspects of the system being modeled be captured in the model. In this work, therefore, aspects of the vehicle dynamics critical to control design were important. In this regard, fundamental contributions were made in the areas of stability robustness analysis techniques, model reduction techniques, and literal approximations for key dynamic characteristics of flexible vehicles. All these areas are related. In the development of a model, approximations are always involved, so control systems designed using these models must be robust against uncertainties in these models.

  10. Dynamic Data Structures

    DEFF Research Database (Denmark)

    Tsakalidis, Konstantinos

    We study dynamic data structures for different variants of orthogonal range reporting query problems. In particular, we consider (1) the planar orthogonal 3-sided range reporting problem: given a set of points in the plane, report the points that lie within a given 3-sided rectangle with one....... Dynamic problems like the above arise in various applications of network optimization, VLSI layout design, computer graphics and distributed computing. For the first problem, we present dynamic data structures for internal and external memory that support planar orthogonal 3-sided range reporting queries......, and insertions and deletions of points efficiently over an average case sequence of update operations. The external memory data structures find applications in constraint and temporal databases. In particular, we assume that the coordinates of the points are drawn from different probabilistic distributions...

  11. Safe Dynamic Multiple Inheritance

    DEFF Research Database (Denmark)

    Ernst, Erik

    2002-01-01

    Multiple inheritance and similar mechanisms are usually only supported at compile time in statically typed languages. Nevertheless, dynamic multiple inheritance would be very useful in the development of complex systems, because it allows the creation of many related classes without an explosion...... in the size and level of redundancy in the source code. In fact, dynamic multiple inheritance is already available. The language gbeta is statically typed and has supported run-time combination of classes and methods since 1997, by means of the combination operator '&'. However, with certain combinations...... of operands the '&' operator fails; as a result, dynamic creation of new classes and methods was considered a dangerous operation in all cases. This paper presents a large and useful category of combinations, and proves that combinations in this category will always succeed....

  12. Introduction to dynamics

    CERN Document Server

    Pfeiffer, Friedrich

    2015-01-01

    This concise textbook for students preferably of a postgraduate level, but also for engineers in practice, contains the basic kinematical and kinetic structures of dynamics together with carefully selected applications. The book is a condensed introduction to the fundamental laws of kinematics and kinetics, on the most important principles of mechanics and presents the equations of motion in the form of Lagrange and Newton-Euler. Selected problems of linear and nonlinear dynamics are treated, as well as problems of vibration formation. The presented selection of topics gives a useful basis for stepping into more advanced problems of dynamics. The contents of this book represent the result of a regularly revised course, which has been and still is given for masters students at the Technische Universität München. .

  13. Flight Dynamics Laboratory overview

    Science.gov (United States)

    Sandford, Thaddeus

    1986-01-01

    The Flight Dynamics Laboratory (FDL) is one of four Air Force Wright Aeronautical Laboratories (AFWAL) and part of the Aeronautical Systems Division located at Wright-Patterson AFB, Ohio. The FDL is responsible for the planning and execution of research and development programs in the areas of structures and dynamics, flight controls, vehicle equipment/subsystems, and aeromechanics. Some of the areas being researched in the four FDL divisions are as follows: large space structures (LSS) materials and controls; advanced cockpit designs; bird-strike-tolerant windshields; and hypersonic interceptor system studies. Two of the FDL divisions are actively involved in programs that deal directly with LSS control/structures interaction: the Flight Controls Division and the Structures and Dynamics Division.

  14. Dynamics of Immobilized Flagella

    CERN Document Server

    Fry, D; Ludu, A

    2003-01-01

    Although the auger-like 'swimming' motility of the African trypanosome was described upon its discovery over one hundred years ago, the precise biomechanical and biophysical properties of trypanosome flagellar motion has not been elucidated. In this study, we describe five different modes of flagellar beat/wave patterns in African trypanosomes by microscopically examining the flagellar movements of chemically tethered cells. The dynamic nature of the different beat/wave patterns suggests that flagellar motion in Trypanosoma brucei is a complex mixture of oscillating waves, rigid bends, helical twists and non-linear waves. Interestingly, we have observed soliton-like depression waves along the flagellar membrane, suggesting a nonlinear mechanism for the dynamics of this system. The physical model is inspired by the 2-dimensional elastic dynamics of a beam, and by taking into account uniform distribution of molecular motors torque and nonlinear terms in the curvature.

  15. Dynamics in geometrical confinement

    CERN Document Server

    Kremer, Friedrich

    2014-01-01

    This book describes the dynamics of low molecular weight and polymeric molecules when they are constrained under conditions of geometrical confinement. It covers geometrical confinement in different dimensionalities: (i) in nanometer thin layers or self supporting films (1-dimensional confinement) (ii) in pores or tubes with nanometric diameters (2-dimensional confinement) (iii) as micelles embedded in matrices (3-dimensional) or as nanodroplets.The dynamics under such conditions have been a much discussed and central topic in the focus of intense worldwide research activities within the last two decades. The present book discusses how the resulting molecular mobility is influenced by the subtle counterbalance between surface effects (typically slowing down molecular dynamics through attractive guest/host interactions) and confinement effects (typically increasing the mobility). It also explains how these influences can be modified and tuned, e.g. through appropriate surface coatings, film thicknesses or pore...

  16. Dynamic Data Structures

    DEFF Research Database (Denmark)

    Tsakalidis, Konstantinos

    We study dynamic data structures for different variants of orthogonal range reporting query problems. In particular, we consider (1) the planar orthogonal 3-sided range reporting problem: given a set of points in the plane, report the points that lie within a given 3-sided rectangle with one....... Dynamic problems like the above arise in various applications of network optimization, VLSI layout design, computer graphics and distributed computing. For the first problem, we present dynamic data structures for internal and external memory that support planar orthogonal 3-sided range reporting queries...... unbounded side, (2) the planar orthogonal range maxima reporting problem: given a set of points in the plane, report the points that lie within a given orthogonal range and are not dominated by any other point in the range, and (3) the problem of designing fully persistent B-trees for external memory...

  17. Fundamental composite electroweak dynamics

    DEFF Research Database (Denmark)

    Arbey, Alexandre; Cacciapaglia, Giacomo; Cai, Haiying

    2017-01-01

    Using the recent joint results from the ATLAS and CMS collaborations on the Higgs boson, we determine the current status of composite electroweak dynamics models based on the expected scalar sector. Our analysis can be used as a minimal template for a wider class of models between the two limiting...... cases of composite Goldstone Higgs and Technicolor-like ones. This is possible due to the existence of a unified description, both at the effective and fundamental Lagrangian levels, of models of composite Higgs dynamics where the Higgs boson itself can emerge, depending on the way the electroweak...... space at the effective Lagrangian level. We show that a wide class of models of fundamental composite electroweak dynamics are still compatible with the present constraints. The results are relevant for the ongoing and future searches at the Large Hadron Collider....

  18. Effect of Conductor Verbalization, Dynamic Markings, Conductor Gesture, and Choir Dynamic Level on Singers' Dynamic Responses.

    Science.gov (United States)

    Skadsem, Julie A.

    1997-01-01

    Examines the effects of conductor verbalization, dynamic markings, conductor gesture, and choir dynamic level on individual singers' dynamic responses. Indicates that verbal instructions from the conductor elicited significantly stronger dynamic performance responses than did the other instructional conditions. Suggests that additional research…

  19. Principles of dynamics

    CERN Document Server

    Hill, Rodney

    2013-01-01

    Principles of Dynamics presents classical dynamics primarily as an exemplar of scientific theory and method. This book is divided into three major parts concerned with gravitational theory of planetary systems; general principles of the foundations of mechanics; and general motion of a rigid body. Some of the specific topics covered are Keplerian Laws of Planetary Motion; gravitational potential and potential energy; and fields of axisymmetric bodies. The principles of work and energy, fictitious body-forces, and inertial mass are also looked into. Other specific topics examined are kinematics

  20. Dynamics of structures

    CERN Document Server

    Paultre, Patrick

    2013-01-01

    This book covers structural dynamics from a theoretical and algorithmic approach. It covers systems with both single and multiple degrees-of-freedom. Numerous case studies are given to provide the reader with a deeper insight into the practicalities of the area, and the solutions to these case studies are given in terms of real-time and frequency in both geometric and modal spaces. Emphasis is also given to the subject of seismic loading. The text is based on many lectures on the subject of structural dynamics given at numerous institutions and thus will be an accessible and practical aid to

  1. Computational fluid dynamics

    CERN Document Server

    Blazek, Jiri

    2015-01-01

    Computational Fluid Dynamics: Principles and Applications, Third Edition presents students, engineers, and scientists with all they need to gain a solid understanding of the numerical methods and principles underlying modern computation techniques in fluid dynamics. By providing complete coverage of the essential knowledge required in order to write codes or understand commercial codes, the book gives the reader an overview of fundamentals and solution strategies in the early chapters before moving on to cover the details of different solution techniques. This updated edition includes new

  2. Partial Dynamical Symmetries

    CERN Document Server

    Leviatan, A

    2010-01-01

    This overview focuses on the notion of partial dynamical symmetry (PDS), for which a prescribed symmetry is obeyed by a subset of solvable eigenstates, but is not shared by the Hamiltonian. General algorithms are presented to identify interactions, of a given order, with such intermediate-symmetry structure. Explicit bosonic and fermionic Hamiltonians with PDS are constructed in the framework of models based on spectrum generating algebras. PDSs of various types are shown to be relevant to nuclear spectroscopy, quantum phase transitions and systems with mixed chaotic and regular dynamics.

  3. Statistics of football dynamics

    CERN Document Server

    Mendes, R S; Anteneodo, C

    2007-01-01

    We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by $q$-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.

  4. Gas Dynamics Equations: Computation

    CERN Document Server

    Chen, Gui-Qiang G

    2012-01-01

    Shock waves, vorticity waves, and entropy waves are fundamental discontinuity waves in nature and arise in supersonic or transonic gas flow, or from a very sudden release (explosion) of chemical, nuclear, electrical, radiation, or mechanical energy in a limited space. Tracking these discontinuities and their interactions, especially when and where new waves arise and interact in the motion of gases, is one of the main motivations for numerical computation for the gas dynamics equations. In this paper, we discuss some historic and recent developments, as well as mathematical challenges, in designing and formulating efficient numerical methods and algorithms to compute weak entropy solutions for the Euler equations for gas dynamics.

  5. Substructured multibody molecular dynamics.

    Energy Technology Data Exchange (ETDEWEB)

    Grest, Gary Stephen; Stevens, Mark Jackson; Plimpton, Steven James; Woolf, Thomas B. (Johns Hopkins University, Baltimore, MD); Lehoucq, Richard B.; Crozier, Paul Stewart; Ismail, Ahmed E.; Mukherjee, Rudranarayan M. (Rensselaer Polytechnic Institute, Troy, NY); Draganescu, Andrei I.

    2006-11-01

    We have enhanced our parallel molecular dynamics (MD) simulation software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator, lammps.sandia.gov) to include many new features for accelerated simulation including articulated rigid body dynamics via coupling to the Rensselaer Polytechnic Institute code POEMS (Parallelizable Open-source Efficient Multibody Software). We use new features of the LAMMPS software package to investigate rhodopsin photoisomerization, and water model surface tension and capillary waves at the vapor-liquid interface. Finally, we motivate the recipes of MD for practitioners and researchers in numerical analysis and computational mechanics.

  6. Dynamical Structure of Baryons

    CERN Document Server

    Aleksejevs, A

    2013-01-01

    Compton scattering offers a unique opportunity to study the dynamical structure of hadrons over a wide kinematic range, with polarizabilities characterizing the hadron active internal degrees of freedom. We present calculations and detailed analysis of electric and magnetic and the spin-dependent dynamical polarizabilities for the lowest in mass SU(3) octet of baryons. These extensive calculations are made possible by the recent implementation of semi-automatized calculations in chiral perturbation theory which allows evaluating polarizabilities from Compton scattering up to next-to-the-leading order. The dependencies for the range of photon energies covering the majority of the meson photoproduction channels are analyzed.

  7. Dynamically assisted Schwinger mechanism.

    Science.gov (United States)

    Schützhold, Ralf; Gies, Holger; Dunne, Gerald

    2008-09-26

    We study electron-positron pair creation from the Dirac vacuum induced by a strong and slowly varying electric field (Schwinger effect) which is superimposed by a weak and rapidly changing electromagnetic field (dynamical pair creation). In the subcritical regime where both mechanisms separately are strongly suppressed, their combined impact yields a pair creation rate which is dramatically enhanced. Intuitively speaking, the strong electric field lowers the threshold for dynamical particle creation--or, alternatively, the fast electromagnetic field generates additional seeds for the Schwinger mechanism. These findings could be relevant for planned ultrahigh intensity lasers.

  8. Dynamical angled brane

    Science.gov (United States)

    Maeda, Kei-ichi; Uzawa, Kunihito

    2016-12-01

    We discuss the dynamical D p -brane solutions describing any number of D p branes whose relative orientations are given by certain SU(2) rotations. These are the generalization of the static angled D p -brane solutions. We study the collision of the dynamical D3 brane with angles in type-II string theory, and show that the particular orientation of the smeared D3-brane configuration can provide an example of colliding branes if they have the same charges. Otherwise a singularity appears before D3 branes collide.

  9. Introduction to cluster dynamics

    CERN Document Server

    Reinhard, Paul-Gerhard

    2008-01-01

    Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. The tendency to miniaturise technical objects requires knowledge about systems which contain a ""small"" number of atoms or molecules only. This is all the more true for dynamical aspects, particularly in relation to the qick development of laser technology and femtosecond spectroscopy. Here, for the first time is a highly qualitative introduction to cluster physics. With its emphasis on cluster dynamics, this will be vital to everyone involved in this interdisciplinary subje

  10. Dynamic Global Currency Hedging

    DEFF Research Database (Denmark)

    Christensen, Bent Jesper; Varneskov, Rasmus T.

    2016-01-01

    This paper proposes a model for discrete-time hedging based on continuous-time movements in portfolio and foreign currency exchange rate returns. In particular, the vector of optimal currency exposures is shown to be given by the negative realized regression coefficients from a one......-period conditional expectation of the intra-period quadratic covariation matrix for portfolio and foreign exchange rate returns. These are labelled the realized currency betas. The model, hence, facilitates dynamic hedging strategies that depend exclusively on the dynamic evolution of the ex-post quadratic...

  11. Dynamics of Catalyst Nanoparticles

    DEFF Research Database (Denmark)

    Hansen, Thomas Willum; Cavalca, Filippo; Wagner, Jakob Birkedal

    under gas exposure, dynamic phenomena such as sintering and growth can be observed with sub-Ångstrøm resolution. Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals...... and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. In order to initiate a systematic study of the dynamics and sintering of nanoparticles, various catalytic systems have been...

  12. Dynamic gamma knife radiosurgery.

    Science.gov (United States)

    Luan, Shuang; Swanson, Nathan; Chen, Zhe; Ma, Lijun

    2009-03-21

    Gamma knife has been the treatment of choice for various brain tumors and functional disorders. Current gamma knife radiosurgery is planned in a 'ball-packing' approach and delivered in a 'step-and-shoot' manner, i.e. it aims to 'pack' the different sized spherical high-dose volumes (called 'shots') into a tumor volume. We have developed a dynamic scheme for gamma knife radiosurgery based on the concept of 'dose-painting' to take advantage of the new robotic patient positioning system on the latest Gamma Knife C and Perfexion units. In our scheme, the spherical high dose volume created by the gamma knife unit will be viewed as a 3D spherical 'paintbrush', and treatment planning reduces to finding the best route of this 'paintbrush' to 'paint' a 3D tumor volume. Under our dose-painting concept, gamma knife radiosurgery becomes dynamic, where the patient moves continuously under the robotic positioning system. We have implemented a fully automatic dynamic gamma knife radiosurgery treatment planning system, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least-square optimizations. We have also carried out experimental studies of dynamic gamma knife radiosurgery and showed the following. (1) Dynamic gamma knife radiosurgery is ideally suited for fully automatic inverse planning, where high quality radiosurgery plans can be obtained in minutes of computation. (2) Dynamic radiosurgery plans are more conformal than step-and-shoot plans and can maintain a steep dose gradient (around 13% per mm) between the target tumor volume and the surrounding critical structures. (3) It is possible to prescribe multiple isodose lines with dynamic gamma knife radiosurgery, so that the treatment can cover the periphery of the target volume while escalating the dose for high tumor burden regions. (4) With dynamic gamma knife radiosurgery, one can obtain a family of plans representing a tradeoff between the delivery time and the dose

  13. Structural dynamics analysis

    Science.gov (United States)

    Housner, J. M.; Anderson, M.; Belvin, W.; Horner, G.

    1985-01-01

    Dynamic analysis of large space antenna systems must treat the deployment as well as vibration and control of the deployed antenna. Candidate computer programs for deployment dynamics, and issues and needs for future program developments are reviewed. Some results for mast and hoop deployment are also presented. Modeling of complex antenna geometry with conventional finite element methods and with repetitive exact elements is considered. Analytical comparisons with experimental results for a 15 meter hoop/column antenna revealed the importance of accurate structural properties including nonlinear joints. Slackening of cables in this antenna is also a consideration. The technology of designing actively damped structures through analytical optimization is discussed and results are presented.

  14. Dynamic gamma knife radiosurgery

    Science.gov (United States)

    Luan, Shuang; Swanson, Nathan; Chen, Zhe; Ma, Lijun

    2009-03-01

    Gamma knife has been the treatment of choice for various brain tumors and functional disorders. Current gamma knife radiosurgery is planned in a 'ball-packing' approach and delivered in a 'step-and-shoot' manner, i.e. it aims to 'pack' the different sized spherical high-dose volumes (called 'shots') into a tumor volume. We have developed a dynamic scheme for gamma knife radiosurgery based on the concept of 'dose-painting' to take advantage of the new robotic patient positioning system on the latest Gamma Knife C™ and Perfexion™ units. In our scheme, the spherical high dose volume created by the gamma knife unit will be viewed as a 3D spherical 'paintbrush', and treatment planning reduces to finding the best route of this 'paintbrush' to 'paint' a 3D tumor volume. Under our dose-painting concept, gamma knife radiosurgery becomes dynamic, where the patient moves continuously under the robotic positioning system. We have implemented a fully automatic dynamic gamma knife radiosurgery treatment planning system, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least-square optimizations. We have also carried out experimental studies of dynamic gamma knife radiosurgery and showed the following. (1) Dynamic gamma knife radiosurgery is ideally suited for fully automatic inverse planning, where high quality radiosurgery plans can be obtained in minutes of computation. (2) Dynamic radiosurgery plans are more conformal than step-and-shoot plans and can maintain a steep dose gradient (around 13% per mm) between the target tumor volume and the surrounding critical structures. (3) It is possible to prescribe multiple isodose lines with dynamic gamma knife radiosurgery, so that the treatment can cover the periphery of the target volume while escalating the dose for high tumor burden regions. (4) With dynamic gamma knife radiosurgery, one can obtain a family of plans representing a tradeoff between the delivery time and the

  15. Dynamic gamma knife radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Luan Shuang; Swanson, Nathan; Chen Zhe [Department of Computer Science, University of New Mexico, Albuquerque, NM 87131 (United States); Ma Lijun [Department of Radiation Oncology, University of California San Francisco, San Francisco, CA 94143 (United States)], E-mail: sluan@cs.unm.edu, E-mail: nate@cs.unm.edu, E-mail: zchen@cs.unm.edu, E-mail: lijunma@radonc.ucsf.edu

    2009-03-21

    Gamma knife has been the treatment of choice for various brain tumors and functional disorders. Current gamma knife radiosurgery is planned in a 'ball-packing' approach and delivered in a 'step-and-shoot' manner, i.e. it aims to 'pack' the different sized spherical high-dose volumes (called 'shots') into a tumor volume. We have developed a dynamic scheme for gamma knife radiosurgery based on the concept of 'dose-painting' to take advantage of the new robotic patient positioning system on the latest Gamma Knife C(TM) and Perfexion(TM) units. In our scheme, the spherical high dose volume created by the gamma knife unit will be viewed as a 3D spherical 'paintbrush', and treatment planning reduces to finding the best route of this 'paintbrush' to 'paint' a 3D tumor volume. Under our dose-painting concept, gamma knife radiosurgery becomes dynamic, where the patient moves continuously under the robotic positioning system. We have implemented a fully automatic dynamic gamma knife radiosurgery treatment planning system, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least-square optimizations. We have also carried out experimental studies of dynamic gamma knife radiosurgery and showed the following. (1) Dynamic gamma knife radiosurgery is ideally suited for fully automatic inverse planning, where high quality radiosurgery plans can be obtained in minutes of computation. (2) Dynamic radiosurgery plans are more conformal than step-and-shoot plans and can maintain a steep dose gradient (around 13% per mm) between the target tumor volume and the surrounding critical structures. (3) It is possible to prescribe multiple isodose lines with dynamic gamma knife radiosurgery, so that the treatment can cover the periphery of the target volume while escalating the dose for high tumor burden regions. (4) With dynamic gamma knife radiosurgery, one can

  16. Gravitational Lensing & Stellar Dynamics

    CERN Document Server

    Koopmans, L V E

    2005-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-anisotropy degeneracies. Second, observational results are presented from the Lenses Structure & Dynamics (LSD) Survey and the Sloan Lens ACS (SLACS) Survey collaborations to illustrate this new methodology in constraining the dark and stellar density profiles, and mass structure, of early-type galaxies to redshifts of unity.

  17. Complexified dynamical systems

    Energy Technology Data Exchange (ETDEWEB)

    Bender, Carl M [Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Holm, Darryl D [Department of Mathematics, Imperial College, London SW7 2AZ (United Kingdom); Hook, Daniel W [Blackest Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

    2007-08-10

    Many dynamical systems, such as the Lotka-Volterra predator-prey model and the Euler equations for the free rotation of a rigid body, are PT symmetric. The standard and well-known real solutions to such dynamical systems constitute an infinitessimal subclass of the full set of complex solutions. This paper examines a subset of the complex solutions that contains the real solutions, namely those having PT symmetry. The condition of PT symmetry selects out complex solutions that are periodic. (fast track communication)

  18. Maya Studio Projects Dynamics

    CERN Document Server

    Palamar, Todd

    2009-01-01

    The only hands-on book devoted to mastering Maya's dynamics tools for water, wind, and fire. In the world of animation, the ability to create realistic water, wind, and fire effects is key. Autodesk Maya software includes powerful dynamics tools that have been used to design breathtaking effects for movies, games, commercials, and short films. This professional guide teaches you the primary techniques you need to make the most of Maya's toolkit, so you'll soon be creating water that ripples, gusting winds and gentle breezes, and flickering fires the way Hollywood pros do. The one-of-a-kind boo

  19. Organisations’ evolutionary dynamics: a group dynamics approach

    Directory of Open Access Journals (Sweden)

    Germán Eduardo Vargas

    2010-04-01

    Full Text Available Colombian entrepreneurs’ straggling, reactionary and inertial orientation has been inconsistently lustified by the availability of internal and leveraged resources, a concept intensifying deficient technological capacity. Company activity (seen as being a socioeconomic unit has been integrally orientated within an evolutionary framework by company identity and cohesion as well as adaptation and evolutionary mechanisms. The present document uses a group dynamics’ model to illustrate how knowledge-based strategic orientation and integration for innovation have become an imperative for development, from slight leverage, distinguishing between two evolutionary company forms: traditional economic (inertial, as they introduce sporadic incremental improvements and modern companies (dynamic and radical innovators. Revealing conclusions obtained from such model may be used for intervening in and modernising company activity.

  20. Dynamic Analysis of a Pendulum Dynamic Automatic Balancer

    Directory of Open Access Journals (Sweden)

    Jin-Seung Sohn

    2007-01-01

    Full Text Available The automatic dynamic balancer is a device to reduce the vibration from unbalanced mass of rotors. Instead of considering prevailing ball automatic dynamic balancer, pendulum automatic dynamic balancer is analyzed. For the analysis of dynamic stability and behavior, the nonlinear equations of motion for a system are derived with respect to polar coordinates by the Lagrange's equations. The perturbation method is applied to investigate the dynamic behavior of the system around the equilibrium position. Based on the linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue analysis.

  1. Dynamic Systems and Software

    DEFF Research Database (Denmark)

    Thomsen, Per Grove

    1996-01-01

    A one-dimensional model with axial discretization of engine components has been formulated using tha balance equations for mass energy and momentum and the ideal gas equation of state. ODE's that govern the dynamic behaviour of the regenerator matrix temperatures are included in the model. Known ...

  2. Dynamics of Information Systems

    CERN Document Server

    Hirsch, Michael J; Murphey, Robert

    2010-01-01

    Our understanding of information and information dynamics has outgrown classical information theory. This book presents the research explaining the importance of information in the evolution of a distributed or networked system. It presents techniques for measuring the value or significance of information within the context of a system

  3. The Dynamics of Shape

    CERN Document Server

    Gomes, Henrique

    2011-01-01

    This thesis consists of two parts, connected by one central theme: the dynamics of the "shape of space". The first part of the thesis concerns the construction of a theory of gravity dynamically equivalent to general relativity (GR) in 3+1 form (ADM). What is special about this theory is that it does not possess foliation invariance, as does ADM. It replaces that "symmetry" by another: local conformal invariance. In so doing it more accurately reflects a theory of the "shape of space", giving us reason to call it \\emph{shape dynamics} (SD). In the first part we will try to present some of the highlights of results so far, and indicate what we can and cannot do with shape dynamics. Because this is a young, rapidly moving field, we have necessarily left out some interesting new results which are not yet in print and were developed alongside the writing of the thesis. The second part of the thesis will develop a gauge theory for "shape of space"--theories. To be more precise, if one admits that the physically re...

  4. Dynamics via measurability

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available Generators f for σ -algebras can be used to view the dynamics of an invertible measurable transformation T in terms of the range values of f ∘ T . Such generators are the norm rather than the exception. Related measurable and quantitative methods of estimating a function from the behavior of ergodic averages are also discussed.

  5. Chicxulub Ejecta Dynamics

    Science.gov (United States)

    OKeefe, John D.; Stewart, Sarah T.; Ahrens, Thomas J.

    2001-01-01

    We modeled in detail the ejecta dynamics associated with the Chicxulub impact. We determined: (1) ejecta trajectories, (2) stratigraphic motions, (3) depth of ejecta stages, (4) thermodynamic histories of the ejecta particles, and (5) the final ejecta distribution. Additional information is contained in the original extended abstract.

  6. The Dynamics of Information

    CERN Document Server

    CERN. Geneva

    2007-01-01

    efficacy at making predictions in the real world. About the speaker Bernardo Huberman is a Senior HP Fellow and Director of the Information Dynamics Lab at Hewlett Packard Laboratories. He received his Ph.D. in Physics from the University of Pennsylvania, and is currently a Consulting Professor in the Department of Applied Physics at Stanford University...

  7. Screw bondgraph contact dynamics

    NARCIS (Netherlands)

    Visser, Martijn; Stramigioli, Stefano; Heemskerk, Cock

    2002-01-01

    This paper presents an elegant contact dynamics model in screw bondgraph form. It can model the contact between any two objects of finite curvature. It does so by defining a Gauss frame on the surfaces of both objects in the points that are closest to each other. Then it describes how the Gauss fram

  8. Dynamic Systems and Software

    DEFF Research Database (Denmark)

    Thomsen, Per Grove

    1996-01-01

    A one-dimensional model with axial discretization of engine components has been formulated using tha balance equations for mass energy and momentum and the ideal gas equation of state. ODE's that govern the dynamic behaviour of the regenerator matrix temperatures are included in the model. Known...

  9. Electronic Spectroscopy & Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Mark Maroncelli, Nancy Ryan Gray

    2010-06-08

    The Gordon Research Conference (GRC) on Electronic Spectroscopy and Dynamics was held at Colby College, Waterville, NH from 07/19/2009 thru 07/24/2009. The Conference was well-attended with participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. The GRC on Electronic Spectroscopy & Dynamics showcases some of the most recent experimental and theoretical developments in electronic spectroscopy that probes the structure and dynamics of isolated molecules, molecules embedded in clusters and condensed phases, and bulk materials. Electronic spectroscopy is an important tool in many fields of research, and this GRC brings together experts having diverse backgrounds in physics, chemistry, biophysics, and materials science, making the meeting an excellent opportunity for the interdisciplinary exchange of ideas and techniques. Topics covered in this GRC include high-resolution spectroscopy, biological molecules in the gas phase, electronic structure theory for excited states, multi-chromophore and single-molecule spectroscopies, and excited state dynamics in chemical and biological systems.

  10. Dynamic Contingency Analysis Tool

    Energy Technology Data Exchange (ETDEWEB)

    2016-01-14

    The Dynamic Contingency Analysis Tool (DCAT) is an open-platform and publicly available methodology to help develop applications that aim to improve the capabilities of power system planning engineers to assess the impact and likelihood of extreme contingencies and potential cascading events across their systems and interconnections. Outputs from the DCAT will help find mitigation solutions to reduce the risk of cascading outages in technically sound and effective ways. The current prototype DCAT implementation has been developed as a Python code that accesses the simulation functions of the Siemens PSS�E planning tool (PSS/E). It has the following features: It uses a hybrid dynamic and steady-state approach to simulating the cascading outage sequences that includes fast dynamic and slower steady-state events. It integrates dynamic models with protection scheme models for generation, transmission, and load. It models special protection systems (SPSs)/remedial action schemes (RASs) and automatic and manual corrective actions. Overall, the DCAT attempts to bridge multiple gaps in cascading-outage analysis in a single, unique prototype tool capable of automatically simulating and analyzing cascading sequences in real systems using multiprocessor computers.While the DCAT has been implemented using PSS/E in Phase I of the study, other commercial software packages with similar capabilities can be used within the DCAT framework.

  11. Predictability in community dynamics

    DEFF Research Database (Denmark)

    Blonder, Benjamin; Moulton, Derek E; Blois, Jessica

    2017-01-01

    prominent in disequilibrium ecology, proposing that communities track climate change following a fixed function or with a time delay. However, more complex dynamics are possible and may lead to memory effects and alternate unstable states. We develop graphical and analytic methods for assessing...

  12. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani

  13. Models for Dynamic Applications

    DEFF Research Database (Denmark)

    2011-01-01

    be applied to formulate, analyse and solve these dynamic problems and how in the case of the fuel cell problem the model consists of coupledmeso and micro scale models. It is shown how data flows are handled between the models and how the solution is obtained within the modelling environment....

  14. Organizational knowledge dynamics

    OpenAIRE

    Simona VASILACHE

    2008-01-01

    The paper addresses the main issues concerning knowledge conceptualization and knowledge dynamics, in the context of Romanian organizations. The links between organizational knowledge, organizational learning and organizational culture are being investigated, with the aim of conceptual clarification and paradigm unification, in a domain of increasing research interest, where increasing complexity implies the risk of increasing confusion.

  15. Dynamic Contingency Analysis Tool

    Energy Technology Data Exchange (ETDEWEB)

    2016-01-14

    The Dynamic Contingency Analysis Tool (DCAT) is an open-platform and publicly available methodology to help develop applications that aim to improve the capabilities of power system planning engineers to assess the impact and likelihood of extreme contingencies and potential cascading events across their systems and interconnections. Outputs from the DCAT will help find mitigation solutions to reduce the risk of cascading outages in technically sound and effective ways. The current prototype DCAT implementation has been developed as a Python code that accesses the simulation functions of the Siemens PSS/E planning tool (PSS/E). It has the following features: It uses a hybrid dynamic and steady-state approach to simulating the cascading outage sequences that includes fast dynamic and slower steady-state events. It integrates dynamic models with protection scheme models for generation, transmission, and load. It models special protection systems (SPSs)/remedial action schemes (RASs) and automatic and manual corrective actions. Overall, the DCAT attempts to bridge multiple gaps in cascading-outage analysis in a single, unique prototype tool capable of automatically simulating and analyzing cascading sequences in real systems using multiprocessor computers.While the DCAT has been implemented using PSS/E in Phase I of the study, other commercial software packages with similar capabilities can be used within the DCAT framework.

  16. Dynamic covalent polymers

    NARCIS (Netherlands)

    Garcia Melo, Fatima; Smulders, Maarten M.J.

    2016-01-01

    This Highlight presents an overview of the rapidly growing field of dynamic covalent polymers. This class of polymers combines intrinsic reversibility with the robustness of covalent bonds, thus enabling formation of mechanically stable, polymer-based materials that are responsive to external

  17. Dynamics of homogeneous nucleation

    DEFF Research Database (Denmark)

    Toxværd, Søren

    2015-01-01

    The classical nucleation theory for homogeneous nucleation is formulated as a theory for a density fluctuation in a supersaturated gas at a given temperature. But molecular dynamics simulations reveal that it is small cold clusters which initiates the nucleation. The temperature in the nucleating...

  18. Dynamic public lighting (DYNO)

    NARCIS (Netherlands)

    Kaptein, N.A.; Hogema, J.H.; Folles, E.

    1997-01-01

    In The Netherlands the concept of Dynamic Public Lighting (DYNO) has been introduced, which implies that road lighting is continuously adapted to the prevailing conditions, finding a balance between traffic safety and environment. For instance, in case of favourable weather conditions and low

  19. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and

  20. VYGOTSKIAN DYNAMICS OF DEVELOPMENT

    NARCIS (Netherlands)

    VANGEERT, P

    1994-01-01

    The main thesis of this article is that Vygotsky's 'zone of proximal development' (ZPD) can be redefined in the form of a nonlinear dynamic model. Following a short introduction to the conceptual components of the model, a mathematical reformulation is presented. The mathematical form is shown to ge

  1. Gravitomagnetic dynamical friction

    CERN Document Server

    Cashen, Benjamin; Kesden, Michael

    2016-01-01

    A supermassive black hole moving through a field of stars will gravitationally scatter the stars, inducing a backreaction force on the black hole known as dynamical friction. In Newtonian gravity, the axisymmetry of the system about the black hole's velocity $\\mathbf{v}$ implies that the dynamical friction must be anti-parallel to $\\mathbf{v}$. However, in general relativity the black hole's spin $\\mathbf{S}$ need not be parallel to $\\mathbf{v}$, breaking the axisymmetry of the system and generating a new component of dynamical friction similar to the Lorentz force $\\mathbf{F} = q\\mathbf{v} \\times \\mathbf{B}$ experienced by a particle with charge $q$ moving in a magnetic field $\\mathbf{B}$. We call this new force gravitomagnetic dynamical friction and calculate its magnitude for a spinning black hole moving through a field of stars with Maxwellian velocity dispersion $\\sigma$, assuming that both $v$ and $\\sigma$ are much less than the speed of light $c$. We use post-Newtonian equations of motion accurate to $...

  2. Dynamic lighting design

    DEFF Research Database (Denmark)

    Linnebjerg, Sofie

    and under various weather conditions, creating a multitude of light settings. Humans live in interaction with this dynamic light and consider it as a natural part of our world [Mathiasen, 2015]. Furthermore, it has by the recent discovery of intrinsically photosensitive retinal ganglion cells in 2002...

  3. Dynamics Calculation of DTL

    Institute of Scientific and Technical Information of China (English)

    LI; Jin-hai

    2012-01-01

    <正>The DTL is very important accelerator structure, and it is necessary for the proton linac accelerator. We did the dynamics simulation for the 20 MeV DTL, and obtained the physical and mechanical parameters. The input energy of the DTL is 3 MeV, and the pulsed beam current is 50 mA.

  4. Minimalistic Dynamic Climbing

    Science.gov (United States)

    2010-11-01

    chimpanzees are dynamic climbers that can reach virtually any part of a tree and even move to neighboring trees, while sloths are quasistatic climbers...climbers that can reach virtually any part of a tree and even move to neighboring trees, while sloths are quasistatic climbers confined only to a few

  5. Eutrophication and Zoobenthos Dynamics

    NARCIS (Netherlands)

    Heip, C.H.R.

    1995-01-01

    The possible effects of eutrophication on benthic dynamics are discussed based on the Pearson-Rosenberg Model that describes the effects of organic enrichment on qualitative characteristics of benthic communities. Depending on the amount of organic matter reaching the sediments, the model describes

  6. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani

  7. Dynamic Systems Modeling

    Directory of Open Access Journals (Sweden)

    Sorin Dan ŞANDOR

    2003-01-01

    Full Text Available System Dynamics was introduced by Jay W. Forrester in the 1960s. Since then the methodology was adopted in many areas of natural or social sciences. This article tries to present briefly how this methodology works, both as Systems Thinking and as Modelling with Vensim computer software.

  8. Dynamic public lighting (DYNO)

    NARCIS (Netherlands)

    Kaptein, N.A.; Hogema, J.H.; Folles, E.

    1997-01-01

    In The Netherlands the concept of Dynamic Public Lighting (DYNO) has been introduced, which implies that road lighting is continuously adapted to the prevailing conditions, finding a balance between traffic safety and environment. For instance, in case of favourable weather conditions and low traffi

  9. Dynamic causal modelling revisited.

    Science.gov (United States)

    Friston, K J; Preller, Katrin H; Mathys, Chris; Cagnan, Hayriye; Heinzle, Jakob; Razi, Adeel; Zeidman, Peter

    2017-02-17

    This paper revisits the dynamic causal modelling of fMRI timeseries by replacing the usual (Taylor) approximation to neuronal dynamics with a neural mass model of the canonical microcircuit. This provides a generative or dynamic causal model of laminar specific responses that can generate haemodynamic and electrophysiological measurements. In principle, this allows the fusion of haemodynamic and (event related or induced) electrophysiological responses. Furthermore, it enables Bayesian model comparison of competing hypotheses about physiologically plausible synaptic effects; for example, does attentional modulation act on superficial or deep pyramidal cells - or both? In this technical note, we describe the resulting dynamic causal model and provide an illustrative application to the attention to visual motion dataset used in previous papers. Our focus here is on how to answer long-standing questions in fMRI; for example, do haemodynamic responses reflect extrinsic (afferent) input from distant cortical regions, or do they reflect intrinsic (recurrent) neuronal activity? To what extent do inhibitory interneurons contribute to neurovascular coupling? What is the relationship between haemodynamic responses and the frequency of induced neuronal activity? This paper does not pretend to answer these questions; rather it shows how they can be addressed using neural mass models of fMRI timeseries. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  10. Dynamic public lighting (DYNO)

    NARCIS (Netherlands)

    Kaptein, N.A.; Hogema, J.H.; Folles, E.

    1997-01-01

    In The Netherlands the concept of Dynamic Public Lighting (DYNO) has been introduced, which implies that road lighting is continuously adapted to the prevailing conditions, finding a balance between traffic safety and environment. For instance, in case of favourable weather conditions and low traffi

  11. Dynamic term structure models

    DEFF Research Database (Denmark)

    Andreasen, Martin Møller; Meldrum, Andrew

    This paper studies whether dynamic term structure models for US nominal bond yields should enforce the zero lower bound by a quadratic policy rate or a shadow rate specification. We address the question by estimating quadratic term structure models (QTSMs) and shadow rate models with at most four...

  12. Innovations in dynamic architecture

    Directory of Open Access Journals (Sweden)

    Abdulmajid Karanouh

    2015-11-01

    Full Text Available High performance adaptive solutions are capable of responding to the dynamic nature of users and context. These innovative and dynamic systems are steadily gaining ground over ubiquitous ‘best fit’ static models. These architectural elements often exist beyond the scope of mainstream building standards and traditional methods for data representation or communication. This presents major challenges to a highly standardized and compartmentalized industry in which ‘innovation’ is limited to a few signature practices that design iconic yet expensive structures, which often prioritize aesthetics over performance. This paper offers an overview of the benefits that integrated dynamic systems bring to buildings. Through an examination of an applied practice, this paper offers guidelines for communicating complex geometry in a clear design language across interdisciplinary collaborations. The use of diagrammatic grammar to translate underlying algorithmic rules into instructions for design allows complex, innovative solutions to be realized more effectively. The ideas presented here are based on the design principles of the competition-winning scheme of the Al-Bahr Towers. As lead consultant in Innovation Design & Research at AHR (former Aedas-UK, Abdulmajid Karanouh designed and spearheaded this project in close collaboration with Arup. The buildings won the Best Innovation Award 2012 by the Council for Tall Buildings and Urban Habitat (CTBUH. The pair of towers won recognition for its performance-driven form, and dynamic facade that operates following the movement of the sun.

  13. Dynamic Displays of Data

    Science.gov (United States)

    Angotti, Robin

    2017-01-01

    This article describes Gapminder, a dynamic time-series graph that can be found at http://www.gapminder.org. Gapminder was created by a team of developers (Rosling, Ronnlund, and Rosling 2005) to create beautiful, interactive graphs of otherwise lifeless numbers. Their goal is increased use and understanding of statistics and data that…

  14. Topics in Nonlinear Dynamics

    DEFF Research Database (Denmark)

    Mosekilde, Erik

    Through a significant number of detailed and realistic examples this book illustrates how the insights gained over the past couple of decades in the fields of nonlinear dynamics and chaos theory can be applied in practice. Aomng the topics considered are microbiological reaction systems, ecological...

  15. Dynamic Topography Revisited

    Science.gov (United States)

    Moresi, Louis

    2015-04-01

    Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The

  16. Dynamic nanoparticle assemblies.

    Science.gov (United States)

    Wang, Libing; Xu, Liguang; Kuang, Hua; Xu, Chuanlai; Kotov, Nicholas A

    2012-11-20

    Although nanoparticle (NP) assemblies are at the beginning of their development, their unique geometrical shapes and media-responsive optical, electronic, and magnetic properties have attracted significant interest. Nanoscale assembly bridges multiple levels of hierarchy of materials: individual nanoparticles, discrete molecule-like or virus-like nanoscale agglomerates, microscale devices, and macroscale materials. The capacity to self-assemble can greatly facilitate the integration of nanotechnology with other technologies and, in particular, with microscale fabrication. In this Account, we describe developments in the emerging field of dynamic NP assemblies, which are spontaneously form superstructures containing more than two inorganic nanoscale particles that display the ability to change their geometrical, physical, chemical, and other attributes. In many ways, dynamic assemblies can represent a bottleneck in the "bottom-up" fabrication of NP-based devices because they can produce a much greater variety of assemblies, but they also provide a convenient tool for variation of geometries and dimensions of nanoparticle assemblies. Superstructures of NPs (and those held together by similar intrinsic forces)are classified into two groups: Class 1 where media and external fields can alter shape, conformation, and order of stable super structures with a nearly constant number of NPs or Class 2 where the total number of NPs changes, while the organizational motif in the final superstructure remains the same. The future development of successful dynamic assemblies requires understanding the equilibrium in dynamic NP systems. The dynamic nature of Class 1 assemblies is associated with the equilibrium between different conformations of a superstructure and is comparable to the isomerization in classical chemistry. Class 2 assemblies involve the formation or breakage of linkages between the NPs, which is analogous to the classical chemical equilibrium for the formation of

  17. Complexity in Dynamical Systems

    Science.gov (United States)

    Moore, Cristopher David

    The study of chaos has shown us that deterministic systems can have a kind of unpredictability, based on a limited knowledge of their initial conditions; after a finite time, the motion appears essentially random. This observation has inspired a general interest in the subject of unpredictability, and more generally, complexity; how can we characterize how "complex" a dynamical system is?. In this thesis, we attempt to answer this question with a paradigm of complexity that comes from computer science, we extract sets of symbol sequences, or languages, from a dynamical system using standard methods of symbolic dynamics; we then ask what kinds of grammars or automata are needed a generate these languages. This places them in the Chomsky heirarchy, which in turn tells us something about how subtle and complex the dynamical system's behavior is. This gives us insight into the question of unpredictability, since these automata can also be thought of as computers attempting to predict the system. In the culmination of the thesis, we find a class of smooth, two-dimensional maps which are equivalent to the highest class in the Chomsky heirarchy, the turning machine; they are capable of universal computation. Therefore, these systems possess a kind of unpredictability qualitatively different from the usual "chaos": even if the initial conditions are known exactly, questions about the system's long-term dynamics are undecidable. No algorithm exists to answer them. Although this kind of unpredictability has been discussed in the context of distributed, many-degree-of -freedom systems (for instance, cellular automata) we believe this is the first example of such phenomena in a smooth, finite-degree-of-freedom system.

  18. Dynamically orthogonal field equations for stochastic flows and particle dynamics

    Science.gov (United States)

    2011-02-01

    turbulence. Cambridge University Press, 1959. [10] G.K. Batchelor . An Introduction to Fluid Dynamics . Cambridge University Press, 2000. [11] D. Bau III... Dynamically orthogonal field equations for stochastic fluid flows and particle dynamics by Themistoklis P. Sapsis Dipl., National Technical...unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 2 Dynamically orthogonal field equations for stochastic fluid flows and particle

  19. Growth of nanocomposite films : From dynamic roughening to dynamic smoothening

    NARCIS (Netherlands)

    Pei, Y.T.; Shaha, K.P.; Chen, C.Q.; van der Hulst, Ruben; Turkin, A; Vainshtein, D.I.; Hosson, J.Th.M. De

    2009-01-01

    This paper reports several new findings on the breakdown of dynamic roughening in thin film growth. With increasing energy flux of concurrent ion impingement during pulsed DC sputtering, a transition from dynamic roughening to dynamic smoothening is observed in the growth behavior of TiC/a-C nanocom

  20. Nonlinear Dynamic Model Explains The Solar Dynamic

    Science.gov (United States)

    Kuman, Maria

    Nonlinear mathematical model in torus representation describes the solar dynamic. Its graphic presentation shows that without perturbing force the orbits of the planets would be circles; only perturbing force could elongate the circular orbits into ellipses. Since the Hubble telescope found that the planetary orbits of other stars in the Milky Way are also ellipses, powerful perturbing force must be present in our galaxy. Such perturbing force is the Sagittarius Dwarf Galaxy with its heavy Black Hole and leftover stars, which we see orbiting around the center of our galaxy. Since observations of NASA's SDO found that magnetic fields rule the solar activity, we can expect when the planets align and their magnetic moments sum up, the already perturbed stars to reverse their magnetic parity (represented graphically as periodic looping through the hole of the torus). We predict that planets aligned on both sides of the Sun, when their magnetic moments sum-up, would induce more flares in the turbulent equatorial zone, which would bulge. When planets align only on one side of the Sun, the strong magnetic gradient of their asymmetric pull would flip the magnetic poles of the Sun. The Sun would elongate pole-to-pole, emit some energy through the poles, and the solar activity would cease. Similar reshaping and emission was observed in stars called magnetars and experimentally observed in super-liquid fast-spinning Helium nanodroplets. We are certain that NASA's SDO will confirm our predictions.

  1. Canard cycles in global dynamics

    CERN Document Server

    Vidal, Alexandre

    2009-01-01

    Fast-slow systems are studied usually by "geometrical dissection". The fast dynamics exhibit attractors which may bifurcate under the influence of the slow dynamics which is seen as a parameter of the fast dynamics. A generic solution comes close to a connected component of the stable invariant sets of the fast dynamics. As the slow dynamics evolves, this attractor may lose its stability and the solution eventually reaches quickly another connected component of attractors of the fast dynamics and the process may repeat. This scenario explains quite well relaxation and bursting oscillations. More recently, in relation both with theory of dynamical systems and with applications to physiology, a new interest has emerged in canard cycles. These orbits share the property that they remain for a while close to an unstable invariant set (either singular set or periodic orbits of the fast dynamics). Although canards were first discovered when the transition points are folds, in this article, we focus on the case where...

  2. Stellar dynamics and black holes

    Indian Academy of Sciences (India)

    David Merritt

    2011-07-01

    Chandrasekhar’s most important contribution to stellar dynamics was the concept of dynamical friction. I briefly review that work, then discuss some implications of Chandrasekhar’s theory of gravitational encounters for motion in galactic nuclei.

  3. Homegarden Dynamics in Kerala, India

    NARCIS (Netherlands)

    Peyre, A.; Guidal, A.; Wiersum, K.F.; Bongers, F.J.J.M.

    2006-01-01

    The study of structural and functional dynamics of homegardens offers an opportunity to understand the trends in socioeconomic sustainability in relation to their ecological sustainability. These dynamics were studied in a survey of 30 homegardens

  4. Similarity transformed semiclassical dynamics

    Science.gov (United States)

    Van Voorhis, Troy; Heller, Eric J.

    2003-12-01

    In this article, we employ a recently discovered criterion for selecting important contributions to the semiclassical coherent state propagator [T. Van Voorhis and E. J. Heller, Phys. Rev. A 66, 050501 (2002)] to study the dynamics of many dimensional problems. We show that the dynamics are governed by a similarity transformed version of the standard classical Hamiltonian. In this light, our selection criterion amounts to using trajectories generated with the untransformed Hamiltonian as approximate initial conditions for the transformed boundary value problem. We apply the new selection scheme to some multidimensional Henon-Heiles problems and compare our results to those obtained with the more sophisticated Herman-Kluk approach. We find that the present technique gives near-quantitative agreement with the the standard results, but that the amount of computational effort is less than Herman-Kluk requires even when sophisticated integral smoothing techniques are employed in the latter.

  5. Dynamics of cyclic machines

    CERN Document Server

    Vulfson, Iosif

    2015-01-01

    This book focuses on modern methods of oscillation analysis in machines, including cyclic action mechanisms (linkages, cams, steppers, etc.). It presents schematization techniques and mathematical descriptions of oscillating systems, taking into account the variability of the parameters and nonlinearities, engineering evaluations of dynamic errors, and oscillation suppression methods. The majority of the book is devoted to the development of new methods of dynamic analysis and synthesis for cyclic machines that form regular oscillatory systems with multiple duplicate modules.  There are also sections examining aspects of general engineering interest (nonlinear dissipative forces, systems with non-stationary constraints, impacts and pseudo-impacts in clearances, etc.)  The examples in the book are based on the widely used results of theoretical and experimental studies as well as engineering calculations carried out in relation to machines used in the textile, light, polygraphic and other industries. Particu...

  6. Dynamic coherent backscattering mirror

    Energy Technology Data Exchange (ETDEWEB)

    Zeylikovich, I.; Xu, M., E-mail: mxu@fairfield.edu [Physics Department, Fairfield University, Fairfield, CT 06824 (United States)

    2016-02-15

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

  7. Corruption dynamics model

    Science.gov (United States)

    Malafeyev, O. A.; Nemnyugin, S. A.; Rylow, D.; Kolpak, E. P.; Awasthi, Achal

    2017-07-01

    The corruption dynamics is analyzed by means of the lattice model which is similar to the three-dimensional Ising model. Agents placed at nodes of the corrupt network periodically choose to perfom or not to perform the act of corruption at gain or loss while making decisions based on the process history. The gain value and its dynamics are defined by means of the Markov stochastic process modelling with parameters established in accordance with the influence of external and individual factors on the agent's gain. The model is formulated algorithmically and is studied by means of the computer simulation. Numerical results are obtained which demonstrate asymptotic behaviour of the corruption network under various conditions.

  8. Lattice Boltzmann Stokesian dynamics.

    Science.gov (United States)

    Ding, E J

    2015-11-01

    Lattice Boltzmann Stokesian dynamics (LBSD) is presented for simulation of particle suspension in Stokes flows. This method is developed from Stokesian dynamics (SD) with resistance and mobility matrices calculated using the time-independent lattice Boltzmann algorithm (TILBA). TILBA is distinguished from the traditional lattice Boltzmann method (LBM) in that a background matrix is generated prior to the calculation. The background matrix, once generated, can be reused for calculations for different scenarios, thus the computational cost for each such subsequent calculation is significantly reduced. The LBSD inherits the merits of the SD where both near- and far-field interactions are considered. It also inherits the merits of the LBM that the computational cost is almost independent of the particle shape.

  9. Dynamic system classifier

    CERN Document Server

    Pumpe, Daniel; Müller, Ewald; Enßlin, Torsten A

    2016-01-01

    Stochastic differential equations describe well many physical, biological and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of DSC to oscillation processes with a time dependent frequency {\\omega}(t) and damping factor {\\gamma}(t). Although real systems might be more complex, this simple oscillator captures many characteristic features. The {\\omega} and {\\gamma} timelines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiment...

  10. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  11. Dynamic system classifier

    Science.gov (United States)

    Pumpe, Daniel; Greiner, Maksim; Müller, Ewald; Enßlin, Torsten A.

    2016-07-01

    Stochastic differential equations describe well many physical, biological, and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time-dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of the DSC to oscillation processes with a time-dependent frequency ω (t ) and damping factor γ (t ) . Although real systems might be more complex, this simple oscillator captures many characteristic features. The ω and γ time lines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiments show that such classifiers perform well even in the low signal-to-noise regime.

  12. Constraints On Cosmic Dynamics

    CERN Document Server

    Mbonye, M R

    2003-01-01

    Observationally, the universe appears virtually critical. Yet, there is no simple explanation for this state. In this article we advance and explore the premise that the dynamics of the universe always seeks equilibrium conditions. Vacuum-induced cosmic accelerations lead to creation of matter-energy modes at the expense of vacuum energy. Because they gravitate, such modes constitute inertia against cosmic acceleration. On the other extreme, the would-be ultimate phase of local gravitational collapse is checked by a phase transition in the collapsing matter fields leading to a de Sitter-like fluid deep inside the black hole horizon, and at the expense of the collapsing matter fields. As a result, the universe succumbs to neither vacuum-induced run-away accelerations nor to gravitationally induced spacetime curvature singularities. Cosmic dynamics is self-regulating. We discuss the physical basis for these constraints and the implications, pointing out how the framework relates and helps resolve standing puzzl...

  13. Optimization by record dynamics

    DEFF Research Database (Denmark)

    Barettin, Daniele; Sibani, Paolo

    2014-01-01

    Large dynamical changes in thermalizing glassy systems are triggered by trajectories crossing record sized barriers, a behavior revealing the presence of a hierarchical structure in configuration space. The observation is here turned into a novel local search optimization algorithm dubbed record...... dynamics optimization,or RDO. RDO uses the Metropolis rule to accept or reject candidate solutions depending on the value of a parameter akin to the temperature and minimizes the cost function of the problem at hand through cycles where its ‘temperature’ is raised and subsequently decreased in order...... to expediently generate record high (and low) values of the cost function. Below, RDO is introduced and then tested by searching for the ground state of the Edwards–Anderson spin-glass model, in two and three spatial dimensions. A popularand highly efficient optimization algorithm, parallel tempering (PT...

  14. Dynamics of pyroelectric accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ghaderi, R.; Davani, F. Abbasi, E-mail: fabbasi@sbu.ac.ir [Radiation Application Department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

    2015-01-26

    Pyroelectric crystals are used to produce high energy electron beams. We have derived a method to model electric potential generation on LiTaO{sub 3} crystal during heating cycle. In this method, effect of heat transfer on the potential generation is investigated by some experiments. In addition, electron emission from the crystal surface is modeled by measurements and analysis. These spectral data are used to present a dynamic equation of electric potential with respect to thickness of the crystal and variation of its temperature. The dynamic equation's results for different thicknesses are compared with measured data. As a result, to attain more energetic electrons, best thickness of the crystals could be extracted from the equation. This allows for better understanding of pyroelectric crystals and help to study about current and energy of accelerated electrons.

  15. Dynamics of cell orientation

    Science.gov (United States)

    de, Rumi; Zemel, Assaf; Safran, Samuel A.

    2007-09-01

    Many physiological processes depend on the response of biological cells to mechanical forces generated by the contractile activity of the cell or by external stresses. Using a simple theoretical model that includes the forces due to both the mechanosensitivity of cells and the elasticity of the matrix, we predict the dynamics and orientation of cells in both the absence and presence of applied stresses. The model predicts many features observed in measurements of cellular forces and orientation including the increase with time of the cellular forces in the absence of applied stress and the consequent decrease of the force in the presence of quasi-static stresses. We also explain the puzzling observation of parallel alignment of cells for static and quasi-static stresses and of nearly perpendicular alignment for dynamically varying stresses. In addition, we predict the response of the cellular orientation to a sinusoidally varying applied stress as a function of frequency.

  16. Dynamics and Relativity

    CERN Document Server

    Forshaw, Jeffrey

    2009-01-01

    A new title in the Manchester Physics Series, this introductory text emphasises physical principles behind classical mechanics and relativity. It assumes little in the way of prior knowledge, introducing relevant mathematics and carefully developing it within a physics context. Designed to provide a logical development of the subject, the book is divided into four sections, introductory material on dynamics, and special relativity, which is then followed by more advanced coverage of dynamics and special relativity. Each chapter includes problems ranging in difficulty from simple to challenging with?solutions for solving problems. Includes?solutions for solving problemsNumerous worked examples included throughout the bookMathematics is carefully explained and developed within a physics environmentSensitive to topics that can appear daunting or confusing

  17. Granular Dynamics During Impact

    Science.gov (United States)

    Nordstrom, K. N.; Lim, E.; Harrington, M.; Losert, W.

    2014-06-01

    We study the impact of a projectile onto a bed of 3 mm grains immersed in an index-matched fluid. We vary the amount of prestrain on the sample, strengthening the force chains within the system. We find this affects only the prefactor of the linear depth-dependent term in the stopping force. We propose a simple model to account for the strain dependence of this term, owing to increased pressure in the pile. Interestingly, we find that the presence of the fluid does not affect the impact dynamics, suggesting that dynamic friction is not a factor. Using a laser sheet scanning technique to visualize internal grain motion, we measure the trajectory of each grain throughout an impact. Microscopically, our results indicate that weaker initial force chains result in more irreversible, plastic rearrangements, suggesting static friction between grains does play a substantial role in the energy dissipation.

  18. Metaheuristics for Dynamic Optimization

    CERN Document Server

    Nakib, Amir; Siarry, Patrick

    2013-01-01

    This book is an updated effort in summarizing the trending topics and new hot research lines in solving dynamic problems using metaheuristics. An analysis of the present state in solving complex problems quickly draws a clear picture: problems that change in time, having noise and uncertainties in their definition are becoming very important. The tools to face these problems are still to be built, since existing techniques are either slow or inefficient in tracking the many global optima that those problems are presenting to the solver technique. Thus, this book is devoted to include several of the most important advances in solving dynamic problems. Metaheuristics are the more popular tools to this end, and then we can find in the book how to best use genetic algorithms, particle swarm, ant colonies, immune systems, variable neighborhood search, and many other bioinspired techniques. Also, neural network solutions are considered in this book. Both, theory and practice have been addressed in the chapters of t...

  19. Hysteresis in structural dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Ivanyi, A., E-mail: aivanyi@morpheus.pte.hu [Pollack Mihaly Faculty of Engineering, University of Pecs, Boszorkany u. 2, H-7624 Pecs (Hungary); Ivanyi, P., E-mail: peteri@morpheus.pte.hu [Pollack Mihaly Faculty of Engineering, University of Pecs, Boszorkany u. 2, H-7624 Pecs (Hungary); Ivanyi, M.M., E-mail: ivanyi@uvaterv.hu [Pollack Mihaly Faculty of Engineering, University of Pecs, Boszorkany u. 2, H-7624 Pecs (Hungary); UVATERV Ltd, Budapest, 1117, Dombovari ut 17, Budapest (Hungary); Ivanyi, M., E-mail: drivanyi@pmmk.pte.hu [Pollack Mihaly Faculty of Engineering, University of Pecs, Boszorkany u. 2, H-7624 Pecs (Hungary)

    2012-05-01

    In this paper the Preisach hysteresis model is applied to determine the dynamic behavior of a steel column with mass on the top and loaded by an impulse force. The column is considered as a rigid element, while the fixed end of the column is modeled with a rotational spring of hysterestic characteristic. In the solution of the non-linear dynamical equation of motion the fix-point technique is inserted to the time marching iteration. In the investigation the non-linearity of the rotation spring is modeled with the Preisach hysteresis model. The variation of amplitude and the action time interval of force are changing. The results are plotted in figures.

  20. Dynamic coherent backscattering mirror

    Science.gov (United States)

    Xu, M.

    2016-01-01

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation. PMID:26937296